| Jocko Homo |
I think is time for a new law, and therefore a new thread.
What is the law?
Don't use transistors that (used to) come in metal packages for audio.
That means no TO-5s, no TO-18s, and no (gasp!) TO-3s.
That means no 2N2222s, 2N2907s, 2N2218s, 2N2907s, 2N3904s, 2N3906s, 2N2102s, etc.
Why, you ask?
Because they are all lousy transistors, that is why.
These parts have been around longer that most any of us have been designing stuff. They are from an era when a breakdown voltage of 40 or 60 volts was hot stuff. They all have low beta, which means they have low gain. Which you need to eliminate the nonlinearities they generate.
In the 70's, power amp desingers discovered high voltage transistors with weird numbers like MPS-U10 and MPS-U60 had very low capacitance. This made them very desirable for the gain stage of a typical amp. Too bad thay had low betas, but they were fairly linear, and hey, back then we used tons of gain (and feedback), so no problem.
Today, they a lots of modern transistors with a small base region, which means they will have low noise and capacitance, and a high beta. These devices have breakdown voltages of 80-120 volts and are very linear. Their Ft is plenty high enough for audio, but not high enough to build 70 MHz IF amps with. (See earlier post on why not to use RF transistors. Come to think of it....most of them also came in metal cans.) These devices are made by companies like Toshiba, Rohm, Zetex, and others. They are out there, and not all that hard to find.
Now, as for TO-3s.........
I can't think of a worse package to try to work with. A senior engineer I knew used to swear everytime he was forced to use one. Blamed the damn military for coming up with them, and holding back the evolution of modern packages.
In the 70's all we had to work with was lousy, stinking TO-3's. And the parts themselves weren't much better electrically. Thanks to places like Toshiba, Sanken, Fujitsu, and others, we now have modern plastic packages that are much easier to work with. Plus, the parts are higher beta, more linear, lower capacitance, and more rugged. Don't believe me? Then why is Motorola ("On".....or whoever they call themsleves now) second-sourcing Toshiba 2SA1302s and 2SC3281s? (You didn't hear this from me, but the first few batches Motorola sold were rebadged Toshibas: they couldn't get theirs right yet. You heard this from my retired friend who worked there at the time.) So there should not be any reason to buy a MJ15003 or MJ15028 or whatever unless you have to fix some old boat anchor amplifier.
Speaking of lousy TO-3s and power amps.........
A dealer I knew was having troble back in the early 80's with a certain amp blowing up all the time. I was called in to fix the problem. The amp used 40 volt rails. The problem was that the output transistors were rated at 80 volts. At 25 degrees C., that is. Too bad the amp was much warmer that that.
I called the company that designed it and explained the problem. I suggested a better transistor with a higher breakdown voltage. Their response?
"Well, that transitor has a different slope in the SOA. I don't think it will work."
Appears as if they were smart enough to look at a data sheet, and even where to look. Maybe. Too bad they weren't smart enough to understand how to derate operating voltage as a function of temperature.
Guess what? They soon went out of business, and not a moment too soon. We made $$ fixing amps for dealers who couldn't get repair work done. They didn't come back after we finished working on them.
Let's see how much hate mail this generates.
Class dismissed. |
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| subwo1 |
| To start, I totally agree about the T03 cases. I always hated them too. But could it be that most transistors like 2N3906 etc are not really made and structured like they were in the past? Recently I bought some 1N4001 diodes which were able to stand 600 volts! I think that manufacturers often just relable similar transistors with the old numbers just to supply the market. |
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| rtirion |
Don't throw your to-3 out of the window just yet!
A lot depends on the type of heatsink you use with them!
Most of the time thermal specs and application is vastly superior to that of flat packs.
Yes, even the much touted toshiba 2sc3281/2sa1302 is a poor performer in the thermal department. Tried them in a class A amp (JLH 1969) version on massive heatsinks, very carefully mounted. They got up to 70 degrees within a few minutes. I even have them in a commercial amp, and they are not to my liking. Used the old to-3 2n3055E in TO-3 from motorola and RCA in this JLH and they are quit fine.
Mr. Nelson Pass uses IRF's in to-3 package and these work very nice. Ask around on this forum, and you will hear a lot of nice comments about his products and designs.
Yes, I am aware of better flatpacks, for instance the ones from Sanken, but did you compare the price per unit with for instance a nice MLJ 15XXX from motorola?
regards |
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| Damon Hill |
I think it's a non-issue.
I've been using MJ15003/4s for literally decades with no problems,
on 60 volt rails. Sometimes I had the bias turned up a bit high,
before I realized I didn't like the sound, and the silicon was
getting pretty hot. I'm currently using MJ21193/4s, which have
much higher breakdown voltages and even better SOA. Both
are reasonably rugged devices, more so than the plastic case
versions, and there are good choices there, too.
Sometime getting the heatsink drilled for TO-3 cases is a problem.
Plastic case devices may need at most one hole for the mounting
screw, and that can be a money-saver in a given design. Plastic
devices lend themselves to PCBs and designs with minimal or no wiring and no sockets, and that's certainly A Good Thing on several counts.
The above TO-3 transistors are packaged in steel (magnetic) cases, and audiophiles consider this A Bad Thing. I'm not convinced, and it's not easy finding every electronic component with non-magnetic construction. On my budget, I just live with it.
Given a choice of bipolar power transistors, I'd take a serious
look at the Toshiba devices as they're more linear and faster,
and reasonably rugged, too. But my present amplifiers have or
will use heat sinks drilled for TO-3, and I prefer to use them as
they can dissipate more heat and have a higher SOA.
Very good driver transistors are available in plastic cases, so there's no need to worry about metal cases any more, as are most signal transistors. Moot issue, and it's been that way for
a long time.
I don't see a need for any laws, new or old. Just a good understanding of the choices and how to design with them.
(Cheerfully tosses bucket of ice water on Jocko Homo) |
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| grataku |
Cheers to that Yoko!
I haven't been using motorolas since I found the way to put my hands on multi-emitter, extended beta sankens. Then I discovered that japanese drivers, ie 2sc4793pair, where also ALOT better (read beta within 10 units for both NPN and PNP, try that with the MJE15030-31!), full plastic case, and much easier to work with. Further down the line I found that there were low noise small signal trannies 2sa1015(I think) that were rated to 120-130V with the same excellent consistency in beta values at that point it was bye-bye to the BC550-560c.
Damon,
unless you got that "buy American" thing going, I think it's high time for you to move to the 21th century.;) |
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| dice45 |
| quote: | Originally posted by Damon Hill
....
The above TO-3 transistors are packaged in steel (magnetic) cases, and audiophiles consider this A Bad Thing. I'm not convinced, and it's not easy finding every electronic component with non-magnetic construction. On my budget, I just live with it. ...
|
Damon,
being a tube nuts (but with the mind open to use "sand" where it is useful), i cannot avoid using magnetic material, allthemore as i finally had to face that signal transformers (quite oposite to their reputation do not add to audible distortion and eat up detail resolution) sonically can behave like a piece of wire and/or add speed, juice, flavour to the sound.
But apart from excessive (and expensive) use of "iron" in my amps, i have learned to avoid any magnetic component, be it a capacitor, a resistor, a wire sort, a part of a plug, what ever. I even made listeningcomparisons between the same amp mounted into a magnetic, non-magnetic and non-metallic housing. Provided the amp needs no shielding, the non-metallic housing and the non-magnetic housing play in the same league, the non-metalic however wins. But both win hands-down agains a magnetic housing, Admitted, a non-magnetic case costs.
But we are in the DIY area here, right? Why not building the amp in a wooden box with the heatsink mounted to it? Why not using a small pocket magnet when choosing components, be they from the surplus store or slaughtered out from an old Tektronix? this cost a bit of care, not more. And there is no need to buy fancy NOS stuff llike Vitamin Q for $$$ and later complaining about the nastiness not trackable in the sound (just to give an example).
A year ago, i made a huge listening comparison of different coupling capacitors. I also measured them, and noted down physical properties, magnetism among them. Those caps i loved or atleast could live with all were non-magnetic. Those I loathed or could not stand all were magnetic to some extent. The cap I hated most (in fact my body insisted to escape) was an expensive hermitcally sealed Teflon Mil cap and its housing was very magnetic. The test was done in a scinetific manner, separating data acquisition from analyzing the data. However, before others second my experience, i stick with calling this magnetic thing a coincidence.
As said above, this anti-magnetic thing is not a cost issue, it is an issue of a ittle bit care and effort. And we all DIYers have heaps of that, right? :)
Damon, i dod not like how Jocko expressed or described his coincidental finding; for my taste he was a bit quick to call it a law and asking the community whether they can share the observation leads to a better open-mindedness to that topic for us all. At the moment it is nothing more than a coincidence although i can follow his logic. I have learned to track coincidences of that sort and to pay attention to them, often an explanation can be found later, turning the coincidence into a general rule. |
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| Jocko Homo |
To subwo1:
They probably make them the same old way. Eventually they will stop making them period and suggest better parts. Somewhere I have an old National book from the 70's that shows the die geometry. No reason to change it, unless they have too. When they do, there is always someone who complains that the part no longer works in their design.
To rtirion:
I don't have to worry about price......availabilty is a more important issue with us. Any transistor will overheat, and yes 70 degrees is too high. But that doesn't mean the heat transfer was the problem. Ever check for oscillations? Nothing heats an output faster. My designs might be more conservative (not necessarily better, just different), so I don't encounter that problem.
To Damon Hill:
I hate cold!!!!!! Brrrrrrr. I think you may have missed the joke buried inside all the sarcastic diatribe. You are right though: DIY types would do themselves well to adhere to the basics, and learn to master them. I have seen many professional designs done in by overlooking the basics, namely good grounding. Perhaps you would like to share your expertise in those areas with the gang. No one is too old too learn.
You will note that the part I skewered used 40 volt rails and was only rated for 80 volts. I believe the part you are using is better than the one I was so riled over. Plus, you are probably smart enough not to drive it to hell and back. Dealers.........can't live with them, can't shove them in the trunk of your car......
To grataku:
Yoko......I like that. You were paying attention. Move to the front of the class.
To dice45:
I think you missed the joke too. I'm just tired of seeing postings with ancient parts that are lousy.
It has nothing to do with magnetic steel parts or any or anal-retentive audio neurophillia.
Let me put it this way:
L-I-N-E-A-R-I-T-Y.
Keep that hate mail coming! |
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| Chucko |
Jocko, might we ask: What are your favorite parts of the moment?
As an aside, I play with a lot of mass-market musical instrument gear, and it always amazes me what those manufacturers expect a humble 4558 op amp to do! Even a TL072 sounds better in many of these applications, and that's not saying much. |
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| Damon Hill |
Jocko:
In the eternal search for The Better Part, I am VERY curious
about the 2SA1302/2SC3281 and how they're constructed
differently that allow them to have much better bandwidth
and linearity than most audio power transistors. Toshiba's
web page hasn't offered any clues.
I'm using TO=3 cased devices because that's the type of
heat sink that I have to work with at present. At some point
I want to build a professional-looking implementation of Leach's
amplifier design, and the Toshiba transistors are candidates
for the output stage. I'd like to take best advantage of their
characteristics, if I can; that might include a redesign of the
PCB layout for that type of case, to eliminate the wiring and
sockets, if I can. In the short term, the most I can do is
obtain some samples and try them on a prototype to verify
stability, etc.
But I'm not dismissing Motorola/ONSemi devices out of hand,
either. I recently obtained 10 each of the MJ21193/4 devices
and found them pretty tightly grouped for gain; they're more
linear and have twice the Ft of the MJ15003/4. And they're
pretty rugged, partly because of the TO-3 case.
Does one really need an Ft of 30 Mhz in an audio output transistor? Sound like asking for trouble into a highly reactive load.
Sanken and HItachi, among others, make some interesting
bipolar output devices, but I know next to nothing about them.
Sanken likes to use a package for which I cannot find insulators.
Don't know what to tell you about dealers and repair shops; some
of the things I/we know in this forum are very specialized.
grakatu:
Noted on the transistors you like; those numbers will go into my
little black book for further investigation.
Dice45:
It's really difficult to find electronic components that are always
non-ferrous in construction. Some of them are expensive, too.
I used Black Gate electrolytics in a couple of places in my present
build of Leach's amplifier where I thought the application was
critical enough and might have used Mills wirewounds for the
emitter resistors; I found some good quality IRC wirewounds
locally that appeared to be a distinct improvement over sandcast
devices, but they do have ferrous end caps. I attempted to
select metal film resistors that were non-ferrous from my local
supplier, but was only partially successful and I can only afford
ten cent parts, not seven dollar tantalums or bulk foil! But it
would have been awful nice...
I made other tweaks too, but I'm under a tight budget and couldn't afford all the best parts; I had to select the best ones
I could afford and the rest came out of my collection of parts.
I just have to hope that I made good compromises.
Building with wood is out of the question. Don't go there. To get
a decent chassis I may have to cannabalize a Hafler; I don't have
access to shop tools for metal fabrication. That's always been a
big headache for me. |
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| rtirion |
Jocko,
Oscillation was not the problem at all. Checked with scope and spectrum analyzer. Dissipating 35W per device continuossly is what TO218, TO247, TOP-3 simply can't handle reliable.
Getting Sankens, Toshibas and the like is no problem what so ever in the Netherlands. Even mica insulators or silpads are no problem. 15$ for a single 2sc2922 and 1$ for an insulator is what I think a little expensive. When you need 4 or 6 per channel things add up fast.
I also found the production span of a lot of japanese transistors to be short. So if you think you found a good one, you must be carefull it is not out of production within a couple of years.
Famous hiraga's are all prone to this. |
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| Jocko Homo |
rtirion:
You are right: J. A. Pan does make brief runs, and when they are gone, that's it.
35 watts is a bit much, but at least the plastic parts use copper instead of steel to get the heat out.
You are unfortunately paying much more than I am. I use perhaps a dozen devices per channel. And I am not rich.
Damon:
Right now all my data on that stuff is packed away, so you will have to trust me on this for a while. If the data is available, you should notice how low the Cob is. Think phase margin......
The higher you can push the point at which the gain goes to unity, the more likely you are to have enough phase margin to keep the whole thing from blowing up. Especially if a reactive load shifts the phase even more.
I believe I have a stash of mica washers for the Sankens here somewhere. Email me, and perhaps we can work out something in the way of a swap. I don't think I have very many Sanken devices, though.
Motorola has learned much by cooperating with........well, can I say......the enemy. You might notice that a lot of those TO-3 types they used to make are now gone. They are a volume driven firm; if the demand dries up and they have something else in its place, then say goodbye to your favorite part.
chucko:
Anything in specific? Or just in general? BJT or JFET? |
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| rtirion |
Jocko,
Copper to get the heat out? Where?
Not on Sankens, not on Toshibas.
All have nice steel backs. Come to think of it, I never saw a power BJT with a copper back. If you can show me one (photo), I will believe you.
Medium power, Motorola BC362 (very, very old) has a flimsy little copper/brass tap. This is the only transistor I ever saw with copper.
So what's wrong with this story?
Regards |
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| dice45 |
| quote: | Originally posted by Jocko Homo
To dice45:
I think you missed the joke too. I'm just tired of seeing postings with ancient parts that are lousy.
It has nothing to do with magnetic steel parts or any or anal-retentive audio neurophillia.
Let me put it this way:
L-I-N-E-A-R-I-T-Y.
Keep that hate mail coming! |
Jocko,
Your call for linearity tries to break-open doors already open, but linearity is not all-and everything and the magnetic issue touched here (serving only as an example) might be quite a challenge to measure and fit into any signal theory but it is audible.
DTopic,
now you sign your post a 2nd time with "Keep that hate mail coming!"
Do you enjoy that? Do you intend to start flaming around in this friedly forum?
You obvioulsy are very competent in the semiconductor electronic field but being a master in one field does not make you automatically a master in all other fields. One of them being human communication.
I read your post over and over again and , normally being very receptive for jokes, i could not find the joke, not even even traces of it. The fact you had a joke in mind is not enough for all to reckognize the joke. Email and forums are tricky as they do not carry emotions at all. Misunderstandings happen often from that. So may i recommend the use of smilies/emoticons as a beginner's technique for indicating if you do not mean it that serious or intend a put-on or whatever?
Besides that, better get your neck soft. smooth and supple again; it can be very nasty on the long run if the neck remains stiff in that position and it is permanently raining into the nostrils :) besides that fists with flight height of ~6' cannot be seen early enough :) :) :) |
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| dice45 |
Hello Damon,
| quote: | Originally posted by Damon Hill
It's really difficult to find electronic components that are always
non-ferrous in construction. Some of them are expensive, too.
I used Black Gate electrolytics in a couple of places in my present
build of Leach's amplifier where I thought the application was
critical enough and might have used Mills wirewounds for the
emitter resistors; I found some good quality IRC wirewounds
locally that appeared to be a distinct improvement over sandcast
devices, but they do have ferrous end caps. I attempted to
select metal film resistors that were non-ferrous from my local
supplier, but was only partially successful and I can only afford
ten cent parts, not seven dollar tantalums or bulk foil! But it
would have been awful nice...
|
you are exposing an exquisite taste, if biased me may say so :)
Since a buddy of mine came up with this magnetic thing, i have a strong samarium cobalt magnet in my rucksack when i go shoping components. I build with ordinary components until i know which values i need, then i take from my collected stock what i came across over the years and the rest of expensive parts i order. Have tried out all form your list, i like the Mills, Vishay bulk foils and tantalums very much. I can afford this rest as i invest some time in slaughteing old Tektronix equipment and my stock of non-magnetics is quite big meanwhile :)
| quote: |
I made other tweaks too, but I'm under a tight budget and couldn't afford all the best parts; I had to select the best ones
I could afford and the rest came out of my collection of parts.
I just have to hope that I made good compromises.
|
There are some expensivish components like Hovland and Holco and Teflon Mil Caps and Audionote copper and silver foil in oil which were quite a disappointment for me. But i often find stuff sounding 1st class from non-audiophile sources. My preferred coupling cap is primarily used in military, railroad, avoinics applications, not cheap but affordable: 1µF @ 500V~ costs about 10$, compare that to Hovland or the like.
| quote: | Building with wood is out of the question. Don't go there. To get
a decent chassis I may have to cannabalize a Hafler; I don't have
access to shop tools for metal fabrication. That's always been a
big headache for me. [/B] |
If you are on a tough budget (so am i), plywood boxes carrying components make your amp sound better and cost less, freeing the money for better components. Consider it :)
So did i and ended up using an old wine bottle box to build a prototype of my PP AD1 amplifier with Tango OPTs. Super expensive components (collected over the years, could afford none of them today), built in a wine box! (Bordeaux, of course :) )
The beauity with this box is, i can fold the p2p-wired monster open and have access to every solder joint at once, not directly German style engineering :) and if the box is closed, no lil'critter can crawl in where 400Vdc are alive and check out its own conductivity :)
Give your self a bit of time to get accustomed to the concept :D |
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| traderbam |
| I just bought some IRF740As in TO-220 which have plated, solid copper heastsinks. |
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| Havoc |
| You just need to use a torque wrench to set them on the heat sink. I prefer TO3 over TO220 any day. |
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| djdan |
The debate TO3 versus Plastic it is not so relevant for sound quality .
1. What do you want for a power amplifier ?
2. It would be some domestic HI-Fi or something like a tank for stage or dance club ?
( I am a DJ for 15 years and for me the nr.1 priority is " my power amps must work " )
3. Majority of people ( 99%) heare from 20Hz to 16.000Hz.
So why should I care if my amp will deliver full power at 100Khz or at 30Khz ?
4. If somebody heare 0.003% THD or 0.03% please send me a picture of his ear.
5. Why should I care if my amp deliver 0.003% THD if the most better high end speakers have a very very poor distorsion figure and linearity like an EKG from a man in the middle at heart atack.
"Buy american's" or "buy japanese" or " buy europeans " ?
Come on people ! We are in 21 th century ! |
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| paulb |
| quote: | Originally posted by djdan
If somebody heare 0.003% THD or 0.03% please send me a picture of his ear. |
Not the ear itself, just a picture. Don't want any kidnapping scares here.:D |
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| HarryHaller |
I got both ears in the shot....
H.H. |
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| Jocko Homo |
rtirion:
I have HUNDREDS of Japanese plastic "flat-pak" transistors. All with copper backs.
Sorry, but I don't have a digital camera to send you a picture of them. I hate digital.........(joke!)
I see that this thread is going astray. The original point was that why are there postings in 2002 that use ancient parts like 2N2102s? Parts like this should have gone away with the Apollo space program. But it gets posted, and no one notices. Instead, people reply with details of their favorite topolgies (which is fine), but no one points the guy in the right direction where he is probably in the need of the most help.
I realise that there a lots of people here who weren't building stuff in the 60's. But the point is that any transistor that ever came in those old metal cans is also old, and therefore should not be used in a new design/project. There are much better, and modern, parts at our use now.
If one were to ask "Hey, I have a schematic here, probably from the 70's. It has some thing called a 2N2102. Does anyone know what it is? Are they still made? Any better suggestions?", I hope that we could help out.
What if someone asked "Hey, which op-amp sounds better-741 or 1458? And which brands?", I bet we would howl with laughter. Then help the guy out. The same should go for old semiconductors of ALL types, not just obsolete op-amps.
Diceman:
I don't claim to be a master of human communication. Although I will point out my last boss (who thought I was a nut.....wait.....he KNEW I was a nut [joke]) always felt I was the best at written communication of all the engineers there. Bet you are glad you didn't work there [joke]. Wish I didn't either [also joke].) I have a warped sense of humor that comes from 30+ years of working with this stuff. And getting told I can't use a plastic transistor even though TI doesn't make it in a metal can anymore. (Very long story......not germane here......sorry.......[pseudo-joke]. Although the story itself is funny.)
Sorry you don't have the same warped sense of humor I have, and that my jokes evade you. I don't get yours either. So then the joke is now on me. Which is fine. And don't stop on my behalf, either.
I didn't intend to break-open already open doors. I do love lively debate. I don't like flame wars, and have no intention of starting one. If so, I could have a flame war with the last boss I had [joke]. Just trying to wake some people up and see who is paying attention.
Nor do I want to drive this debate in some obtuse direction. Like how to derate the operating voltage of tantalum caps. But I am curious, what factor(s) besides linearity do you consider important? Email me direct if you like. (Anyone else who has a specific question or need may also email. I do answer it all. Advice is free, just laced with snide remarks [joke].)
So let me now close with:
Let's stick to the original topic. Thank you. |
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| paulb |
Hey JH,
I'm guessing you have no use for vacuum tubes... |
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| traderbam |
Harry! That's not you is it Harry?
:eek:
(PS who was taking the photo?) |
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| alvaius |
| I can think of some really really good reasons for using 2N2222, 2N3904, etc., etc. It is called my pocket book. They make these things by the billions. Lot of people make them and make lots of them. They are dirt cheap. Are they the best? Heck no, but for many applications, they absolutely work. And if they do the job, they will be the cheapest, easiest to obtain, etc. |
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| djdan |
Mr. HarryHaller,
I like you becouse you are a funny guy. I agree with your point of view . Yes, your beautiful dog have a much better hear than you.
PS. I have one identical dog. When I make experiment with my power amps he run far away . |
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| Jocko Homo |
We used to have a cat here that would run for cover every time I played "Eat that Question", on "The Grand Wazoo" by Frank Zappa. We never could figure out why.
Keep that sense of humor!
Back to the point.......
No, I don't care for tubes, but some of my best friends make their living building tube gear.
I have a pair of RCA 810s in my stash. Never used. Carbon plates, grid and plate caps, ceramic socket. Used mainly for modulators in AM transmitters. Would make a nice grounded-grid linear amp for some ham radio types.
Any takers? |
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| dice45 |
| quote: | Originally posted by Jocko Homo
.... Diceman:
...
Sorry you don't have the same warped sense of humor I have, and that my jokes evade you. I don't get yours either. So then the joke is now on me. Which is fine. And don't stop on my behalf, either.
|
my sort of humour also can be warped, mischievous, macabre, but in any case humour is not generally compatible , besides that irony requires the receiver brain to have its floating point unit running (let's hope anyone of us has one :) ), so i care to label my humour, just to protect my environment from me. Has served me well on the web where few have English as mother tongue or seen some Gerhard's or George W's or Aaron's last goofs in the news or the current soap.
| quote: | I didn't intend to break-open already open doors. I do love lively debate. I don't like flame wars, and have no intention of starting one. If so, I could have a flame war with the last boss I had [joke]. Just trying to wake some people up and see who is paying attention.
|
You don't like flames? that's great, so do i. Was not sure, to be honest :)
| quote: | Nor do I want to drive this debate in some obtuse direction. Like how to derate the operating voltage of tantalum caps. But I am curious, what factor(s) besides linearity do you consider important? ...
|
1st, i am not an amp guru at all (i pester my friend Manfred who is a tube amp guru every other day with questions :) ), i come from mechanical design. Have a look on my website, it is terribly untidy but there are some nice pictures.
I am a listening animal rather than a measuring one, but i ensure by measuring i do not compare apples and oranges. Andi try to marry my measuring with my listening results to find out which measured parameter has which significance to the amp making music.
Linearity is a static thing, or atleast it is not easy to measure if linearity is maintained dynamically in the presence of more than one frequency.
Music OTOH requires a lot of frequencies to be handled simultaneously and each amplitude change to be processed properly.
To me, dynamic behaviour of an amp is one of the most vital things, correct, lifelike dynamic behaviour, to be particular.
One thing i learned from Manfred: hook a headphone amp with differential AC inputs, high commonmode rejection and adjustable gain to B+ and GND of your amp's PS and let the amp under test play music into an appropriate load. And then listen to the music on the B+ ! Provided enough gain, there always is music. If the music is sounding distorted (the PS then facing a complex load and not being able to handle it), the amp is **** and will sound like ****. Dynamics are wrong then, too.
A very important thing, for tube amps more an issue than for SS amps, is what Allen Wright calls downward dynamic range and some other folks descibe it as blackness of background from the listening point of view. Or should i call it dynamic signal2noise ratio?
An amp should have enough headroom to handle the required signals with ease. Being linear but clip hard 1 W or 1 V above the specified rating is a no show to me.
An amp can have all sorts of nastinesses not or not easily measurable but audible in a way they prevent the listener from enjoying his music, or worse, make the listener escape. Magnetic resistors and capacitors are a cause for such , TME, and that's why i was initially lurking the thread, seeking for other "coiincidences" :) . I have not yet fully understood how this works, but not understanding doesn't keep me from avoiding magnetic stuff AFAP.
And then there are those completely unmeasurable but clearly audible things like soundstaging, body, air between sound sources, 3D imaging from only 2 speakers. I am a hedonist :), i want to feel the vibrating air column of Sonny Rollins' saxophone and to "visualize" the grand piano of Maurizio Pollini playing the 1st Chopin Ballade.
Distortion: a tricky issue. Special sorts of distortion like produced by single ended triode amplifers can sound utterly pleasant and seducing and very open and detailed, but tricky recordings demanding detail resolution just to hear through the material (Coltrane's "Ascension" e.g. or orchestral music from Arnold Schoenberg) show that a SET amp's subjectively experienced detail resolution can be quite a fake; that's why i tend to prefer 1st class PP tube amps.
Exceptions exist, of course, there are exceptionlly good SET amps. I have several vocal recordings demanding in speech understandability. If and to which degree i understand the sung text is a criterium quite easy to distinct for me. Those SETamps mentioned excel in that and i doubt my PP design will reach that level of speech understandability.
Although, if i increase the number of used interstage transformers, maybe!? :) ooops, they are reputed to be non-linear ..... but ..... hmmmhh ... i don't care :) they can sound gorgeous!!
I am VERY curious how Hugh Dean's AKSA amp will behave in those respects, ordered it yesterday. Rumours have it that the amp sounds tube-like :) while maintaining SS virtues.
Several friends of mine prefer their tube amp's sonic colorations to a neutral sound, they are aware of the lack of neutrality and use it to their taste. As we say over here, allowed is what pleases :) . I doubt this sort of coloration can be measured in a way that we can say "this peak in th FFT spectrum causes the oboe sound like an English horn or a clarinet"
And, to community, sorry for bothering you with tube %age of content in a SS thread :) |
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| SteveG |
Just kidding- just my sense of humor, get it?
Well, anyway... You jumped all over my use of one of these antiquated transistors in my post on a current sourced zen balanced line stage. If you had taken the time to even read through the previous posts, you would have seen that it was only used in the schem. because it was one of the models in my freeware software. The circuit was put together just to learn and see what could be done, and to stimulate conversation.
So, what's my point here? Just that this forum has been a place where people with less experience (such a myself) can go to learn and talk about circuit theory. Why the burden of policing the DIY community for part correctness has been placed on you, I don't know. Maybe it's some kind of curse that falls on the the few all-knowing transistor gurus of the electrical world. Who the heck knows! Anyway, I appreciate the info, but you can shove the attitude (I assume you know where, or are you not as adept with biology as you are with transistors?)
Steve G. |
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| Jocko Homo |
Signoro Dice:
There is nothing for me to disagree with, and much to recommend. Just because some of it came from tube design does not matter. The principles are the same. Only the topologies have been changed to protect the innocent [joke]. (You didn't really think I could go far without at least one, did you?) You and your friend are definitely on the right track.
I use a real-time analyzer to look at the modualtion on the rails. Gives me more insight as to what is going on. But sometimes I do take the output and listen to it. Yes, I measure stuff to death, but only to understand what is happening and why. Measuring for the sake of "well, this number better be such-and-such or this thing will never sound right" is fruitless. Measurements are a tool, not the goal.
I have to say that I am constantly amazed by how well some many non-Americans can converse in our bastardized English. Makes it too easy to forget that they are not all of us are. My Italian is terrible, and what little I know is......well........something we can't use here!
Back to linearity:
I was only refering to the device itself. I don't see the sense in using a lousy part, that can not be helped by all the feedback in the world when there are better parts available. Parts that do not cost much more than generic ones. Yes, I started out picking parts out of someone elses scrapheap. If that is all you can afford, well..........fine. But buying heat sinks and filter caps for your next amp project will be a tall mountain to climb.
So for all of you in the USA:
Digi-Key
MCM
They sell all manner of parts, relatively cheap. Since you can afford to buy a computer, be online, figure out how to participate in this forum, then it would seem logical that you can order a 2SC2240 online from MCM instead of some ancient part. Try it sometime.
Signoro Giacouomo |
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| Jocko Homo |
SteveG:
If you really need any help, I am more than willing to help. Even with parts......I have tons. All new. All quality. And not a politically correct one to be found.
I got a D in biology. [no joke]. |
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| traderbam |
Jocko,
May I ask what you do for a living and for whom?
BAM |
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| subwo1 |
Jocko Homo,
I am a big fan of new tecnologically advanced parts too; that is simple analog ones. But I doubt that I am the only one dreading the day when everything only comes in small surface mount packages! Maybe I am just an old fuddy duddy or something.:) |
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| grataku |
Jocko,
irreverent, with a passion for DIY audio, funny username (maybe one day I will disclose what mine means), solid-state tendencies, love for Japanese transistor...
if I didn't know better I'd say you sound like one of my alter ego s...
MY GOD HERR DOKTOR, I do have multiple personalities disorder!
Though I think I can account for most of my day today, I can't racall posting anything.
You are on the fast track of being ostracized by the some of the 'founding fathers' of this site.
Let the good times tRoll!;) |
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| Jocko Homo |
Not at all [joke].
traderbam:
I used to work in the advanced technology lab of a major telecom company in the US. Then one day they decided that they really didn't need one anymore. (Some say it was a thinly veiled excuse to get rid of the company's biggest trouble maker. Guess who! [no joke.....especially to all of the other engineers thrown out too.] Careful.......there are more than one us here. Some of them like tubes, though.)
Anyway.....irreverent, probably, but always willing to help.
I answer all my email and help whomever asks. Except for the guy who asked what brand of tape should he use to record CDs with.
I have had people that I know nothing about, in places like the backwoods of South Africa, about ask me "Hey, I hear you may a have a copy of such-and-such book. Can you copy Chapter ## and send it to me?" The answer was yes on all counts. Did so at my expense, and was pleased to receive a postcard from some place in South Africa I still couldn't find on a map.
I once received a nice homemade gift from a guy in the Netherlands who needed some Sanken data sheets.
But I will settle for a simple "thanks", and the knowledge that someone out there actually was able to benefit from my expertise. And that they could proudly point to their system and proclaim "Hey, just try that with your Bose!"
Does that help answer your question?
subwo1:
I recently shoved a 24-bit Burr-Brown digital filter/DAC into an old Philips CD player. Parts were so small I needed a magnifier to build it. And we won't even duscuss how many times I burned my fingers.
Next one will be on a PCB. Won't be fun, but I hope to have less burns.
Roll Tide! [College football cheer] |
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| dice45 |
| quote: | Originally posted by HarryHaller
I got both ears in the shot....
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Nice alien dog, Harry!
green eyes are impressive!
at which speed does he take off? 7 km/h? :) :) |
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| SteveG |
Hey, since you are the transistor know-it-all guru, why don't you write up some kind of article on current production GOOD transistors to use. I konw I would be interested.
SteveG. |
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| dice45 |
hello Jocko,
i am living in Monaco di Bavaria, not the state Monaco on the Italian peninsula :) not that it matters much regarding distance, only pedants complain about that :)
| quote: | Originally posted by Jocko Homo
There is nothing for me to disagree with, and much to recommend. Just because some of it came from tube design does not matter. The principles are the same. Only the topologies have been changed to protect the innocent [joke]. (You didn't really think I could go far without at least one, did you?) |
Noone having gotten that far like us is innocent :) . Iron man Thomas Mayer feels quite comfortable with the voltages in his 211-driven 211 amp, 1200V= at the plate is still handlable, he thinks. Just not wise to be careless with 1200V. Real thin the air gets with this 4kV= SET amp a guy named Orin Block built (did i remember the name correctly?)
| quote: | You and your friend are definitely on the right track.
I use a real-time analyzer to look at the modualtion on the rails. Gives me more insight as to what is going on. But sometimes I do take the output and listen to it. Yes, I measure stuff to death, but only to understand what is happening and why. Measuring for the sake of "well, this number better be such-and-such or this thing will never sound right" is fruitless. Measurements are a tool, not the goal.
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RRRight. Told you Manfred is a tube guru. Although i'afraid he will not like to read himself adressed as such. Suggestion: you build yourself a headphone amp as descibed and then marry what you see on your spectrum analyzer with what you hear with the headphone amp.
And come back with results :)
Any audible distortion spots a complex load behaviour where maybe a resistive should be.
| quote: | | I have to say that I am constantly amazed by how well some many non-Americans can converse in our bastardized English. Makes it too easy to forget that they are not all of us are. My Italian is terrible, and what little I know is......well........something we can't use here! |
Thank you for the implicite compliment.
My Italian too is terrible, close to being nonexistent. Having had Latin at school, this helps me a lot if i have to read Italian, but listening to an Italian, just forgetaboutit, they talk *speed-of-light* fast :)
But my German is fair to good, i guess.
Latin is a wonderful language to learn how a language works (or should i say "should work"). It is completly consistent and logical and has VERY few exceptions (exceptions are the PITA of every beginner). It is what Italian has developed from but today i guess it is closer to English as far as grammar is concerned.
Italians, please correct me if necessary :) .
English grammar is utterly powerful and effective when it comes to describing causal relations. English texts describing technology are atleast 35% shorter than a German text describing the same. Yet the English text is usually clearer and easier to understand.
English also is powered if not boosted by having a mighty vocabulary with mighty concepts. I have collected about 12 German words non-translatable to English because no concept exists there. Collecting English words non-translatable to German i have given up to collect, too many.
The human brain has to learn early (during childhood) how to learn languages and how a language works. Otherwise learning a foreign language as an adult person will be a very hard job. IMO, most English speaking countries which do not force their children to learn foreign languages do them no favour by this.
| quote: |
Back to linearity:
I was only refering to the device itself. I don't see the sense in using a lousy part, that can not be helped by all the feedback in the world when there are better parts available. Parts that do not cost much more than generic ones. ... |
I wish this would be the case with vacuum tubes. Although there still are some nice unknown beauties out there not yet hunted by the crowd of tube collecting maniacs. The #46 tetrode e.g, it still is dirt cheap, one gets 2.5Watts out of a pair triode-wired, 2.5 Watts of sonic heaven.
It took me a hard and expensive learning curve to find out that from 2A3 single plate an ordinary guy like me will never get some decent matched pairs for a decent PP amp. Now i decided to sell the 7 perfect but unmatchable samples i got and forgetabout the 16 tubes i had to buy to get 7. Sooo ****ed off! Learning fees.
But living in AD1-land, i was able to collect some AD1 (better equivalent of the mentioned 2A3) of a less sought-after hence cheaper brand and later to -- surprise, surprise -- find out that this brand has the nicest sonics of all AD1 avaialble. This is the crux with a zeroFB tube amp as with any simple topology: any component has its clearly audible sonic footprint. For an exotic beast like the AD1 with its exotic side contact base, even the pot sockets cost $$. And then there are input transformers, IS transformers, output transformers, plate chokes, grid chokes, huge foil caps having not much capacitance but lethal voltage ratings ....
be happy with your heatsinks, not a tall mountain to climb , a gentle hill maybe :)
Question: how would you substitute a power tube by one or more semiconductors (for testing and measuring purposes)? I want to have a "tube dummy" for checking that the amp is healthy and not killing tubes before i plug the $$$ AD1 in. I already tucked 4 unknown pentodes aside having the same 8 pin side contact base to slaugther the bases of.
In a Ratheon engineering data book i found a circuit of two N-channel J-Fets in series with the lower device's drain connected to the upper device's source and the lower device's source connected to the upper device's grid and serving as the "cathode", the lower device's gate serving as a "grid" and and upper device's drain serving as "plate". The data book claims this SSVTR circuit to be a pentode substitute but gives no hint how to dimension it to substitute a given tube. Those circuits must have been available as integrated or hybrid devices.
Do you know of triode substitutions or how to realize them? If not, a pentode substitution will do for testing. |
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| Jocko Homo |
SteveG:
Might be easier, and faster, for all of us if I emptied out my parts bin, and listed what was there. Acceptable ?
I notice in my MCM catalog that Motorola/ON 2N2222s are more expensive than what I use! The 2N3904s are cheap though, but big deal. Pennies difference.
I know more than one high-end manufacturer that buys ALL their parts from MCM and Digi-Key. Availablity is the name of the game, and they have mnost every thing you should need. Except big heat sinks. (I used to buy extrusions direct from Thermalloy, and machine them at work. No idea what I will do now.)
dice45:
I would hope your Italian is worse than mine [joke]. My grandparents came from there about a century ago. But I don't speak it. Rather hard to learn, but I occasionally give it a go. Keeps me form going nuts after working with those SMT digital filters.
I suspect that one reason us "ugly Americans" have little skill in foreign languages, and anything else foreign, might have something to do with my parents' generation (the WWII crowd) being embarrassed that their parents were [dirty, smelly] emigrants that weren't welcomed with open arms in the flood of immigrants in the late 19th and early 20th centuries.
Enough of Sociology 101.
What you are describing is the concept behind dual-gate MOSFETs, something RCA did a lot of in the late 60s/ early 70s. I have books on that, but they are packed away right now. The transfer curves roughly followed a pentode, but they were pretty much useless, except as a front-end transistor in receiver circuitry. The used the second gate for AGC control.
Back in the "good old days", designers were struggling with ways to make SS circuits act just like tube circuits. Tubes were all they knew, and our wonderful education system wasn't much help in moving students foward. The texts of the time droned on and on about "hole" and electron movement, the valence bond, and garbage like that. Things that did nothing to enable you to build a single-transistor amp. So they constantly came up with circuits like you found. It was all very empirical, and largely due to their heads being stuck in the wrong place. (Another reason why early SS amps had interstage coupling and output transformers.)
I imagine some SPICE devotee can model it, but trial and error might be your best bet. At least you have access to some good, rugged MOSFETs where you are. Biggest problem I suspect will be the bias voltages needed will not be compatible. You are definitely on you own here! |
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| Jocko Homo |
You forgot:
2SA1038
2SC2389
2SA1145
2SC2705 |
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| SteveG |
| quote: | | Might be easier, and faster, for all of us if I emptied out my parts bin, and listed what was there. Acceptable ? |
Go for it! But, I was hoping you would tell why these parts are superior. I really would like to know how to go about choosing a part- that is something that no one ever seems to talk about. It's almost completely arbitrary, from what I've seen. |
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| HarryHaller |
No....... parts selection is anything but arbtirary! The parts on this list are there on the basis of listening test, use by designers in good sounding designs, and quaility of the manufacturer. Toshiba and Zetex make great transistors. Go to Nelson Pass's website and see what he is using. Go to Erno Borbely website and see what he is using. Go read the construction articles in The Audio Amatuer and audio electronics and see what they are using. Go to
the resources mentioned on this forum and see what they are using. There are so many resources on the Web that this is almost a no brainer......... I believe that pricing and where to buy most of these has even been mentioned in this forum.
H.H. |
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| SteveG |
| quote: | | There are so many resources on the Web that this is almost a no brainer |
My apologies. I must have left it at home.
So, if there are so many resources telling why a particular part is used, how about giving me a few links instead of telling me I'm sitting on my brain. Of course anyone can read through an article and see what someone is using, or look at a schematic. I want to know what the criteria is for selecting these parts. It has to go beyond the simple voltage/current/beta/current producton, etc. How do you know what to look for when designing?
You see, instead of coming off like some egotistical jackass and assuming that I know everything, I like to learn from other people and what they have to say. I'm obviously barking up the wrong tree here, as some people like to speak more about a topic than what they fully understand, and run for cover behind insults when their ignorance is showing. I guess the challenge to offer something more than "so and so used this" must be more than you can handle. |
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| Damon Hill |
SteveG:
I share your frustration with the learning process.
Problem is, it does take time to accumlate knowledge and
experience. I pick up clues from as many sources as I can
discover, though I've found Doug Self and G. Randy Sloan's
amplifier design books to be especially helpful sources of information with concrete design examples. The Audio Amateur
and some other electronic hobby magazines were occasionally
helpful, though lately the Internet itself has been my biggest
source of news and information.
Most of my practical experience has been with Marshall Leach's
design, and the companies I worked for; that may have given
me a bias in favor of Motorola/ONSemi transistors. Nevertheless,
I simply don't have much information on other transistors, so
I go with what I know and hope to turn up new information,
however randomly.
After I lost my career in electronics in 1990, I also lost access to
engineering magazines, up to date data books, and just plain
hands-on-the-hardware experience. I had to pick up what I could
on my own through reading, building and modifying, and some
occasional communtity college classes.
I still want my career back, but it's looking grimmer every year that slips by. Best I can do is what I'm doing now.
Keep reading, building, and paying attention to the various threads here; that's the best general advice I can give. |
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| HarryHaller |
Hmmmmm....... I will try again. Here's how to determine which transistors are good for audio.
Plan A.
1. Get a BSEE in Electrical Engineering or a B.S. in Physics.
2, Read everything that you can get your hands on about audio circuit design. This would include everything written in The Audio
Amatuer and Audio Electronics. This would specifically include articles by Nelson Pass, Erno Borbely, and Richard Marsh. Read all the articles by Ben Duncan in Hi- Fi News.
3. Spend 15 years modifying, repairing, and designing audio circuirts.
4. Look inside some of the best sounding amps and preamps to see what parts the best designers are using. They have also probably been through steps 1 to 3.
5. Listen, listen and listen some more.
6. Share the fruits of this lengthy labor for free on audio forums, for free because you love the hobby, and prepare to be insulted.
7. Compare notes with other people who have done steps 1 to 5.
Plan B
1. Whine and moan because it takes more than a week to learn to become an audio designer.
2. Insult graduates of plan A. Expect even more effort on your behalf after you insults, maybe even an apology!
3. Refuse to use www.altavista.com search engine with cryptic entries like "Erno Borbely", "Nelson Pass" and "DIY amplifiers".
4. Ignor links posted in other forums on diyAudio.com and on resources at diyaudio.com
5. Expect sympathy from other forum members who want to learn and build good sounding audio equipment because you were not spoon fed and didn't want to put any effort into learning.
H.H. |
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| dice45 |
Hello Harry and SteveG,
| quote: | Originally posted by HarryHaller
No....... parts selection is anything but arbtirary! The parts on this list are there on the basis of listening test, use by designers in good sounding designs, and quaility of the manufacturer. ... |
yes, agreed, but we rarely know why the designer chose a particular component. It his design and his sonic choice for this location and selection sometimes happened subconsciously, based on practical experience. Unfortunaltely you may have different prefences, Steve, and so you must build your own experience database. I am afraid, your question is an unanswerable one except by yourself or by an experineced buddy demonstrating sonic changes influenced by component choice.
One of my friends , a real SS guru, knows quite a row of transistors by their sonic footprints in differing circuit situations. Being almost a neophyte in respects of SS amp design, i often ask him what to choose and he can tell me which transistor in which circuit will suit my expectations or his expectations, but he cannot explain why, just report experineces. And i have to decide then whether i like it. He certainly selects devices suiting the needs of the circuit, voltage rating, SOA, max.current, temperature coefficient, beta, whatever. But he lately admitted to me that he sometimes uses stuff bad suited but sounding right and that he cannot tell why except saying "sonics".
But, Steve, i can understand you get lost in following Harry's advice, it is not helpful to get confronted with redundant advanced knowledge and the not having the "why" questions explained; this is frustrating.
I get lost, too.
| quote: | Go to Nelson Pass's website and see what he is using. Go to Erno Borbely website and see what he is using. Go read the construction articles in The Audio Amatuer and audio electronics and see what they are using. Go to
the resources mentioned on this forum and see what they are using. There are so many resources on the Web that this is almost a no brainer......... |
To learn from a master requires you to stay in his close proximity.
But i disgress.
Harry, methinks your hint is not of much help except to those few who already have a considerable experience-knowledge base. It rather is maintaining the huge distance between pupil and master. Wouldn't it have helped more, if you posted e.g.
"2sk147 has that'n'that sonic footprint when used at X mA quiescent current in a longtailed pair. It also adds no SS-like coloration when used as lower system together with an ECC88 in cascode."
"2sk43 makes an almost sonically invisible gain=10 amp (wonderful MC-headamp) when used in single-ended topology with 3.5 mA and 2k as drain resistor but please use NiCD battery as supply." ?
Methinks the lists posted by Harry and Jocko are a very good start but near to useless for learners w/o additional "environmental" like in my example.
Steve went angry and i didn not even consider your post offensive on first glance, maybe the "no brainer remark" was unnecessary. But on a 2nd glance, i can understand why Steve went angry, he did ask and got answers in return unprocessable to him. I observed this very often in seminars, make people swallow knowledge they cannot process and they get anrgry if not violent, no, the do not leave, the get violent.
On some fields i have some competence, on others i do not even know what i do not yet know, so i read heaps of books. If a book forces me to swallow unprocessable knowledge, giving obscure, not easily trackable references, incomplete explanations, equation sequences where i get lost in tracking the algebraic simplifications because toooo many lines in between were skipped, i trash this book (even if the author is Barkhausen, Self, Giacoletto, Jones, Tietze-Schenk or some other demi-god) and am proud of myself doing this as i eliminated something preventing me from progressing. Same topic as above, think about it.
So, please folks, let's be friendly and helpful and cooperative again and launch another try :) |
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| SteveG |
Damon,
Thanks for the sane reply. I think you understand what I am after. Unfortunately, some people read everything through tinted glasses, and instead of volunteering helpful information to admitted newcomers to this hobby/profession, they use their extensive knowledge to get off on being a DIY guru. It's a sort of mental masturbation, I think.
I was fortunate in that I have been able to get an entry level position in electrical design, and I have learned a lot and have access to a lot of info and great minds. My description of parts selection being arbitrary comes from the fact that all the engineers that I work with tend to have their favorite parts, and they use them because that is what they are familiar with. I am trying to get to the core of the issue and understand why certain parts are better in certain circuits, and how the great ones like Pass and Borbely choose their components. I think that is what sets the real trend-setters apart from the average follower. Sure there is a lot of info on the net, and I constantly sort through it and read everything I can get my hands on. I find much of it to be re-hashed opinions with little new information. It is great to study other people's designs, but I want more!
HH,
Not everyone is able to go get that EE degree... sometimes, as Damon has found out, life gives you a kick in the teeth, and you have to dig your way out, sometimes over a period of years. That was me after high school- I won't go into the details, but things were not right for me to go to school. I had to find a job right away to support myself.
I will admit it: I use this board to gain knowledge from those with more experience, at the risk of bothering some who are easily frustrated with "newbie" questions. I will admit that I don't usually give back as much as I take in.I thought that was what this was all about! I appreciate all the open-minded thought here. Obviously knowledge and wisdom are two different things, as you seem to have much knowledge, and are totally lacking in wisdom. No one with any character would react the way you have in the previous posts to someone who is seeking an honest answer. Your attitude is an insult to those who visit this board. |
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| SteveG |
Bernhard,
Thank you for summing it up and trying to make peace. I am done with my rant. You have answered my questions in a clear and understandable way- I appreciate that. So, to summarize, it's all about experience! I can accept that answer.
I don't expect anyone to write a personalized book for me explaining everything they know about transistors. I was sincerely looking for an answer as to the how and why.
As far as seeing red because of what I did not understand- I don't think that is so much it. I can accept that I don't understand some things yet. I just don't see the point in posting a message to say "go read a book or something". How is that helpful?
Well, anyway, I apologize for going off the deep end if I misunderstood the intent. Please accept my sincere apology if I misunderstood, HH.
<end rant> |
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| PassFan |
Steve:
Yes a lot of designers choose the components they are familiar with. Best buy and circuit city are full of examples designed by SOME of them. People like Erno and Nelson have a passion about them that makes them dig a little deeper and ask your question "Why". They go the extra mile in building smaller circuits and running a bunch of different ones in order to obtain data for comparison and evaluate by listening. This is tedious and time consuming and bores me to death, but they enjoy it. Hence the passion. Four or five years ago Audio Amateur got me into this hobby but I didn't have any place like this to go for answers. So I had to find out for myself (god I bought a lot of books). Occasionally I would call Nelson or Erno for an answer and was surprised to find them willing to take the time to help. Not wanting to become a pest I kept those calls to a minimum. This is a great board with a lot of info and it is very easy to go off the deep end. The only thing that sets this forum apart is civility towards each other. Always bear in mind not everyone does background on a post before they let fly with their reply. I have seen some members here for a month or two wind up in some conversations that would make one think they did this for a living when I know they could'nt possibly have picked up that much. When we start asking deep questions or using correct terminology a certain level becomes expected of you. Sometimes we must be careful how much we ask of those who know, and slow it down a little bit. DIY isn't going anywhere, and I'm still learning too just like you.;) |
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| HarryHaller |
I have been accused of expecting people to read between the lines before so I will try to be more explicit this time.
1. I don't know all the answers. Never did, never will.
2. The transistors I have listed are mainly ones familiar to me and the core of designers I work with. Trying to pick a transistor by specification alone will not insure a good design. I listen. I talk to other people who design. I listen to other people's designs.
3. The Toshiba transistors sound good. They make low noise and high transconductance jfets that no one elses parts match in my experience. I also have been happy with the Zetex bipolar and mosfet parts. I believe this two companies have excellent semicondutor fabrication plants and good designs. I have heard many amps that use them that sound good.
4. Read the articles by Nelson Pass and Erno Borbely go into how some of these parts measure in particular mosfets and jfets.
5. I don't think this stuff is quite as cut and dried as people think. If it was, there wouldn't be so many bad sounding circuits out there. The good circuits I have heard are from realitively simple topologies using conservative amounts of feedback and the best
semicondutors and passive parts that the designer could aford at the price level for his product. Power supplies are as important as the "signal path", maybe more so in some designs
6.The main point is that I wanted to make is that there is lot of imformation out there and sorting through it is based in a large part on personal experience. Go build the DIY circuits. Form clubs and share info with other hobbiest. Audition different parts. Listen!
7. I only get annoyed because I have done a tremendous amount of work to get to where I am and what I know and am stiil learning. Maybe as much as I did getting my BSEE. (which was a ***** for me and not easy!) Most of the research was before the ease of the web by the way. I don't throw this out there to get my ego reinforced but because of my passion for the art. When you get far far enough into it it becomes much more than a hobby and is very satisfying and frustrating.
I once read in a book where someone asked how to become an art critic. The answer " Go look at a million paintings." My advice is to go listen to as many circuits, parts, semiconductors as you can.
It is the jorney and not the desination that is important.
H.H. |
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| sonnya |
| quote: | Originally posted by HarryHaller
The Toshiba transistors sound good. They make low noise and high transconductance jfets that no one elses parts match in my experience. I also have been happy with the Zetex bipolar and mosfet parts. I believe this two companies have excellent semicondutor fabrication plants and good designs. I have heard many amps that use them that sound good.
H.H. |
I would go as far to say that if you choose the right Zetex BJT you will parts wich have better perfomance than what any other manufacture can come up with..
Sonny |
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| traderbam |
Steve,
I can add a few thoughts about choosing transistors. I would suggest the most important thing is to understand the circuit surrounding the device and really get it clear in your head what the important characterisitcs are that the device should exhibit. Not device is ideal so you have to get clear in your mind which compromises are the least hurtful. This is the hardest thing.
One way you can do this is on paper if you are good at reasoning and have rules of thumb from experience. Another is to use a simulator and create a circuit with ideal transistors (variable current sources) and then degrade them in realistic ways and see which degradation the circuit is most sensitive to. Another is to build parts of the circuit and try different devices and try to correlate measurements with device differences published in the datasheets. All approaches require determination and perseverance.
The most likely parameters that will matter to sonic performance in semiconductors are the dc transfer characteristic (eg: Ic vs Ib vs Vbe OR Id vs Vgs vs Vds), capacitances (Cbe vs Ic, Ccb vs Vcb OR Cgs vs Id, Cdg vs Vdg) and Ft. The circuitry surrounding the device will guide you as to which are most sensitive and what ranges are acceptable. For example, Cdg is not so important if you are using a cascode topology. I don't think device noise matters much in power amps; it matters a lot in phono stages of pre-amps.
Once you know what balance of characteristics you are seeking you then have the difficult job of searching thorough datasheets. Even on the web the mfrs only provide very noddy search facilities and this can be frustrating.
Clearly an easier method is to copy the devices that others have used as Harry suggested. This presupposes that they had the same design goals and circuit requirements as you and that they chose well. Don't take this for granted.
Personally, I don't judge devices by their covers - plastic, metal, TO3, TO220 whatever. I cannot definitively recommend parts because it depends what your circuit needs. I often use AD SSM2210 matched npns for LTPs but your circuit may prefer a couple of discrete npns to eliminate the collector to collector capacitance caused by the shared die. I have found MJ15022/23 to have low distortion in push-pull configuration, but they have fairly high capacitances and are not so suitable to high feedback topologies. I can say that in push-pull designs the choice of output devices is likely to dominate the sound. At the end of the day there are lots of choices and you must decide.
Finally, please don't become superstitious. Electrons laugh in the faces of the superstitious. It's all engineering and there are real reasons for everything you hear and the "art" is not so black for those who understand the engineering.
BAM |
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| Jocko Homo |
I get the flu, and look what happens.........
Now I know how Samuel Clements must have felt.
SteveG:
I don't know that I can explain to your satisfaction why a certain device has properties that I think are good, especially the physics behind it. The original point wasn't what transistors I think will sound good, but which ones I KNOW will NOT sound good.
Basically a 2N****.
I have to disagree with Hairy Holler somewhat. A degree in engineering will do very little to help you build good sounding audio gear.
Engineering school is basically boot camp for engineers. Plain and simple. They throw as much **** at you in 4 years to see who has what it takes to get even more (but different ****) thrown at you for the next 40 years. If anything, it is a hinderance to building audio stuff. You have to clean your head out of all the debris they fill it with. Maybe that is why 2 of the best known designers to people here are both physicists.
There is no substitute for experience. You will learn more by doing, even if it is just perusing other stuff than you will in boot camp. A famous audio designer friend (who I don't think will allow me to quote him) likes to say: "Steal the best, invent the rest." Engineers do not design in a vacuum; they are constantly taking bits and pieces of things they have accumulated over the years and turning them into something different.
And as for this nonsense on how life kicks you in the teeth, or wherever, and how hard:
I don't think anyone wants to get in a contest with me about that. You will lose.
As Joe Bob Briggs, the Drive-in Movie Critic of Grapevine, TX likes to say:
"I don't want to have to 'splain this to you again." [joke]
Jocko |
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| HarryHaller |
I am glad to see Jocko is still with us. Okay.....you can omit part 1. from plan A. I will confess that both Jocko and I have BSEEs. It doesn't hurt anything as long as you listen and are willing to not let theory dominate things. Still....knowing how to design and measure things sure doesn't hurt when it comes to building circuits that don't misbehave at R.F. or blow up. I have been trying to provide a gentle hint (with a slegehammer sometimes) at some of the work done by some talented individuals that is available online. Steal the rest? Well, only the best.
H.H. |
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| traderbam |
"You have to clean your head out of all the debris they fill it with. Maybe that is why 2 of the best known designers to people here are both physicists. "
I suppose if you are saying that physicists are more open-minded because they graduate having learned very little that is applicable to audio design then I suppose I could agree. :D
These sort of generalisations are not helpful nor informative. There are people who can think and those who are challenged in all disciplines and besides it also depends on the content of your degree and the quality of the teachers.
BAM |
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| Jocko Homo |
I don't think physicists are necessarily more open-minded. Just a lot smarter. They have to actually understand the entire realm of physics, not just a small niche that goofballs like me and Hairy Holler have apparently figured out.
Speaking of physicists.......read Bob Pease's articles in the online version of Electronics Design magazine. (No, I don't know the URL....)
Buy and read his book "Troubleshooting Analog Circuits". It belongs in everyones library. Borrow it if you can't buy it.
More useful stuff than you will get in 4 years at any US engineering bootcamp. |
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| Nelson Pass |
I like Bob Pease a lot, but I haven't gotten the impression
that he has any patience for the subjectivist viewpoint ;) |
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| jduncan |
| Just to throw my 2 cents in here, I'm a little disposed to object to the statement that you won't learn anything from any US engineering "bootcamp". Believe it or not, there are actually schools still left which aren't bootcamps for EEs....I know mostly because I go to one, and those who say you don't need any theory to design good amps will never have the satisfaction of doing anything great that's really their own. You CANNOT (almost by definition) get very far just by copying/modifying others designs and to do anything else you need to know what's going on. |
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| haldor |
Try complete and utter disdain. Bob's work has had an influence on my development as an engineer and is probably a big part of the reason why I usually end up on the objectivist side of arguments. Everything I have read of his that I understand is totally right on the money. I reread his book every year or so and devour his columns every month.
I tend to give his opinions the benefit of the doubt plus probably a little bit more. Heck, sometimes I just push my I-Believe button like everyone else and go on.
I spent a day with him at a design conference last year and really loved it. I love the way he derives circuits in his columns too. It is such fun to watch a gifted analog designer iterate into a good solution to a tricky problem.
Bob is quite an iconoclast. There are few things he likes better than bursting somebody's bubble, especially when it's full of hot air. If you want a some real heat, just get him started the quality programs corporate leadership likes to inflict on the troops.
Peace,
Phil |
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| Jocko Homo |
Nelson is right......Bob has no patience for the weirdness in subjective audio. But he is brilliant, and his insights are a lesson to all. Get the book, read it, then come back and tell us what, and how much, you learned.
I'm glad someone is enrolled in a good university. Although some of the worst engineers I have worked with were from GA Tech and MIT. True story, no joke.
Jocko |
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| dice45 |
| quote: | | Steal the best, invent the rest. |
:) fully agreed.
| quote: | | You have to clean your head out of all the debris they fill it with. |
This could have been said by a musician, in fact it has been said by a famous classical musician (sorry, forgot who it was) concerning how to do Mozart right:
"First you have to learn all the stuff, Quintenzirkel, harmony theory, pianistic technique, all the heavy load, and then you have to get rid of it again to access Mozart, to play it right".
Since school i had lenghty discussions with musicians about right performances, and there were objecitvists among them like among engineers, objecting to certain famous musicians performances. Claiming they played it not by the book ()and of course claiming i had no right to judge as i have no musical education) And there were subjectivists adoring Clara Haskil playing Mozart with one of her hands crippled and sometimes maybe making small mistakes now and then but successfully having gotten rid of anything in the way to accessing Mozart. Playing Mozart like a master-degree-skilled child, with the soul of a child.
Or Solomon playing Beethoven maybe not as technically flawless as he was able before his series of small strokes finally paralyzing his hands but doing it idiomatically right, and detailed so, without stepping on any of the countless landmines hidden in Beethoven compositions, delivering a whole, bringing the listener close to Beethoven's divine insanity.
Those musicians do intuititvely right what they do (and not necessarily by the book) and so do gifted engineers, designers. Sometimes the textbook stuff stands in the way of seeing a smart, not-so-orthodox solution.
But: one only can get rid of it after one had had it. One has to pass it, to have it in the repertoire, the textbook stuff can be terribly useful (and a PITA if not at hand), but doing it by the book is not a mental state one has to stay in.
However, text book models are simplified models of reality. How much simplified? that is what we learn by doing it, by experience. And so any objectivist still mentally growing is in permanent danger to become a subjectivist :) |
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| Jocko Homo |
Thanks, diceman, for coming up with the word on the tip of my tongue.
Pease's writings will teach you how to think intuitively about analog circuits. Something you will not gather at "bootcamp". (Yes, I admit some of you may actually something there, but not much. At least don't count on it.)
The irony is that one of the things that they try to impress upon young minds there is how to think. But most fail miserably at it. One does not need to sit through an entire semester of solid-state physics to get lectured at length as to why the capacitance of a reverse-biased diode changes with voltage. You can figure that out by looking at Cob vs. voltage. You do not have to understand all of the theory to put it to use. |
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| HarryHaller |
Cob.......Isn't that something you bite corn off of? Before getting too carried away by intuition:
1. You have to know what a reversed biased diode is.
2. You have too know how transistor looks like a reversed biased diode and a forward biased diode.
3. Once you figure out what Cob is and how to find it on a data sheet, what do you do about? Mark Twain once said "Everyone talks about the weather, but no one does anything about it."
4. Once we understand Cob (output capacitance) for a transistor, we investigate Collector Emitter voltage, the effect of choice of load resistance on bandwidth and bias conditions. Should we cascode? Should we buffer with a follower stage? Should we select a different transistor?
Sounds like some of those Electrical Engineering fundamentals could come in handy about now.........
H.H. |
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| Jocko Homo |
Fundamentals, yes. Theoretical drivel, no.
Understanding it is one thing. Deriving it is problably an exercise one does not need. |
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| jduncan |
Jocko:
The way people generally come up with *anything* new at all is NOT by just following directions on how to make a certain type of design, or copying others. It requires understanding really what's going on in these circuits and beyond a basic level thats impossible without the education.
Also, anyone who ever wants to do anything other than build amps (ie, DACS, digital filters, all kinds of things like that) doesn't have a hope in hell without some serious knowledge. |
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| HarryHaller |
It is possible to build a very good amp without an engineering or
physics degree. I good basic understanding of transistors is very helpful though. Lots of bad sounding amps have been designed by EEs. Lots of great sounding amps have been built by non EEs. An interesting example is the trend to designs using no global negative feedback. I wonder if the popularity of this approach might have been brought about by non EE types having difficulty
designing stable negative feedback loops. Interestingly this lead to a critical examination of negative feedback by the academic community. Again I really advise reading the articals by Nelson Pass and Erno Borbely for an excellent overview of amplifier design.
H.H. |
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| Jocko Homo |
You do not need to have gone to engineering school to be able to design stuff.
You do know have to know what you are doing.
I do design "serious stuff", and I can't think of a single thing I learned in "bootcamp" that has ever helped me. Hell, DACs, micros, and stuff like that weren't even invented yet when I was there.
Books.......they are out there.....read them. Afterall, isn't that what you do in college? Who can tell me the last time they used their Gray & Searle?
OTOH, how many engineers say they read their Bob Pease at least once a year to make sure they haven't forgotten anything. |
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| traderbam |
Education or not. Who cares?
Let's hear some more laws Jocko. Spread your wisdom. :) |
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| HarryHaller |
Jocko.....can I have your autograph!?!
H.H. |
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| sdman |
If HP, National, Tektronix, Motorola, TI read this thread, they will
be laying off their engineers and be hiring off the streets. |
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| jduncan |
| i really dont want to keep arguing about this but its really irrelevant that your bootcamp didnt teach you anything because im talking about places that aren'y bootcamps. yes, you can design without a phd in EE but there's a lot of stuff you'll never really know......anyway forget it, no need to argue about this here :) |
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