| r_s_dhar |
"Any day, Any Time, the time honoured 2N3055 designs are better than chip amps." My friend tells me this; and people and prophets from the 70s seem to agree with this. How much of this is the prejudice of a generation? Do graphs, bode plotts, and all such instruemnts under the solar system corroborate? Is there some truth in this?
The cognoscenti are coaxed for a reply!?!!@@##$$%%^^&&** |
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| UrSv |
Now that is a very easy question to answer:
It depends. They can easily be. They very often are not. |
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| millwood |
| quote: | Originally posted by r_s_dhar
"Any day, Any Time, the time honoured 2N3055 designs are better than chip amps." |
Having built more than a few SS amp and a couple of vaccum amps, and played with the stk's and tda of yesteryear, my experience is that the majority of chip amps suck, the stk's in particular, :).
with a SS amp, you have more freedom at its design, and you can easily add or subtract building blocks to suit your own needs: more power? higher voltage; want to drive low-impedence speakers? use more output devices or beefier transistors, etc.
you don't have that with a chip amp. for the most part anyway.
however, chip amps are a lot easier to build, and presummably have better internal consistencies: I rarely match my transistors for my SS amps.
so to me if your application doesn't call for high power and super high performance, go with a chip amp. |
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| moamps |
| quote: | Originally posted by r_s_dhar
[B]"Any day, Any Time, the time honoured 2N3055 designs are better than chip amps."
|
Hi,
2N3055 is very old transistor.
IMHO, can be better against my HGC only in some class A configuration. :cool:
Regards |
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| JOE DIRT® |
| I kind of like 2n3055 because I have amps that sound good that I built from years ago utilising them and never a failure yet! |
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| ACD |
I go for Solid State amp instead of Chip Amps, as you have the possibility to control and select each component....
Chip Amps does not offer much freedom! |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by r_s_dhar
"Any day, Any Time, the time honoured 2N3055 designs are better than chip amps." My friend tells me this; and people and prophets from the 70s seem to agree with this.
|
Well, even in the 1980's this was not any longer quite true. Chipamps have specific issues. Due to thermal issues they tend to be problematic if you really push power. On the good side, IF WELL IMPLEMENTED (LM3875 is a good example) they can offer perfomance comparable to ANY discrete, though power remains limted by the small case.
Given the choise between a "cooking" 2N3055 Amp or something with the LM3875 (and a few other qualifying chips) I would not even have to think, assuming the Chip was well implemented of course.
In the last decade at least for both small signal and medium power circuits I would be VERY HARD pressed to find an Audio application where I could materially (sonically and measured) better the best Chips with a discrete solid state circuit. It's possible, but increadably hard work, work IMHO better applied to get the best from the chips.... ;-)
I had a nice exchange with Walt Jung on this topic, around the time he was running his "Walts Tips" column in EDN and published on "Op-Amp" audio.... Worth a serious read.
Sayonara
BTW, most most monolithic integrated Amp's (op or power) when used for audio are utter dreck, as are most discrete circuits, but that should go without saying (STURGEON'S LAW: Ninety-five percent of everything is dreck.) |
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| millwood |
| quote: | Originally posted by Kuei Yang Wang
BTW, most most monolithic integrated Amp's (op or power) when used for audio are utter dreck, as are most discrete circuits, but that should go without saying (STURGEON'S LAW: Ninety-five percent of everything is dreck.) |
that especially goes for those early STK's (they are hybrid or thick film chip amps where the power devices are actually co-packaged transistors).
Not sure where they are today. I thought Sanyo made most of those STKs. |
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| fedde |
I own an old Technics amp with a STK???? module. I personally fried the module once by playing errr... too loud. :(
The modules were not available anymore. Now I don't care anymore, because I'll built a nice (and free!) gainclone with it. It has a 2x25 V transformer and a large heatsink. I have some old resistors, caps and OPA541's laying here. Let's see if I can build a good sounding amp under $10 :bigeyes:
'Love this hobby... :)
Fedde |
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| millwood |
I remember they being used in a lot of large screen (20"+) TVs and portable stereos back in the 80s.
That reminds me of something else. Wasn't there a chip amp with MOSFET power devices? possibly a TDA. |
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| JOE DIRT® |
I have 2 STK 4042`s sittin here...brand spankin new and I am going to waist my time building an amp with them and its going to sound terrible but what the Hell I`m deaf in one ear and can`t hear out of the other....I grew up with sub standard equipment and I thought it was good at the time..haha
DIRT® |
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| millwood |
we all grew up with substandard parts. Which of us hasn't built a crystal radio?
:) |
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| mrfeedback |
One aspect is overload behaviour.
Chip amps like the 3875 series sound bad when driven into clip or current overload.
TDA chip amps are better in this respect.
STK modules are variable according to the model.
Discrete amps can be anywhere in between.
Most modern amplifiers are close enough to perfect at normal levels, but IMO it is overload behaviour that more strongly distinguishes different amplifiers.
Eric. |
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| fdegrove |
Hi,
| quote: | | Most modern amplifiers are close enough to perfect at normal levels, but IMO it is overload behaviour that more strongly distinguishes different amplifiers. |
And that's precisely where valves really make all the difference...
Seriously, Erik, with your interest in live amplification and related fields you should consider this feature.
Just telling you as a friend with your best interest in mind...;) |
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| mrfeedback |
Hi Frank,
Modern PA systems nowadays typically run oversize amplifiers such that clipping is avoided, or at least allowed to hit clip only momentarily.
It is considered very un-kosher to blow expensive high power drivers, and any live sound engineer who does usually has some explaining to do, and if it happens too often a bad professional reputation is the result.
Also nowadays many modern PA amplifiers incorporate internal soft limiting stages and this can help to idiot proof live systems.
Reasonable quality tube mic and instrument preamp stages are becoming more affordable and more available, and this is where tubes are most relevant for live sound.
FOH tube amplifiers are not an economic proposition for modern live music unfortunately - digital amplifiers are making quite strong inroads but I have heard differing opinions of these.
Perhaps tube amp mids/highs would be worth a try.
I can lend suitable 0.1% tube amps and Turbosound TMS-4's (105 dB/W) for the heck of it and try it out sometime.
The tube amp design that I speak of can be expanded out to 400 RMS - that might be some good loud fun.
Eric. |
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| fdegrove |
Hi Erik,
| quote: | | The tube amp design that I speak of can be expanded out to 400 RMS - that might be some good loud fun. |
400W RMS for mids and highs only would surely make it into earbleeding levels...
If ever you'd try it out , pls let us know how it went.
Cheers,;) |
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| mrfeedback |
350W version (sorry 400W info was wrong) has not been built and likely won't, but the design can be extended to this.
The existing version is conservatively rated at 60W RMS, but even this into 105dB/W will make a decent racket, but still not loud enough for serious PA usage.| quote: | | 400W RMS for mids and highs only would surely make it into earbleeding levels... |
I thought the benefit of tube amplifiers was no ear bleeding ?.
In the near future (a month or two) I will be making new crossovers for a whole bunch of TMS-4's (the originals have been BURNT) so this will be a good opportunity to give them a go with with a nice tube amp - I'll let you know what the result is.
Eric. |
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| millwood |
one thing I really liked about (some of) the STK chips is the separation of output stage from the rest of the chips. If you want, you can hook up your own output devices and use the input, vas and driver stages of the chip. I wish National can do the same with its class ab chips - not to integrate the output devices on the chips - much like their Class D offerings.
That way, you just go find your own power BJTs and you have one wonderful, versatile, and powerful amp.
we can all dream, cannot we? |
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| carlosfm |
Guys, I assume this thread was started with a domestic point of view.
50 watts RMS is more than enough for your room.
Anyway, thinking of an ideal amplifier (when are we going to have a wire with gain?:bawling: ), I will point out two main advantages of chip amps:
1. Short signal path.
2. Much less components.
These should theoretically make very hard for you to make a discrete design to be as good as the best chips.
In practice, since I first switched on the first GC I built, I've got a bug in my head.:devily:
My god, it's fantastic!
And it would be very hard for anyone to make a discrete design for a preamp with the technical specs and sonic excellence of an op-amp like the OPA627/37.
BTW, Kuei, your pre was reviewed in Hi-Fi World.:cool:
They say it's very good.:D |
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| mrfeedback |
STK3082II and some others are driver stage only modules, and their specs are pretty good from memory, and economic too.
Precaution - good heatsinking is mandatory for reliable long term operation of these.
Eric. |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by millwood
I wish National can do the same with its class ab chips - not to integrate the output devices on the chips - much like their Class D offerings.
That way, you just go find your own power BJTs and you have one wonderful, versatile, and powerful amp.
we can all dream, cannot we? |
Hmmm. I think I prefer NS doing what they did. As they did their homework and implemented the quasi complementary output stage properly, with correct thermal tracking and equal speed devices for both halve waves, plus minimised crossover distortion it is very hard to do better discrete.
You will do usually much worse due to problems with thermal coupling at low levels unless you run a significant class A current and should you be deluded enough to use complementary devices you will have added assymetrical timing in the output stage, which matters if there is no NFB but ballses up things royally when there is NFB around the Output stage.
I'd prefer to have the Output Stage of the NS Chip as Power chip and the ability to have a choice of drivers.... :devily:
Sayonara |
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| phase_accurate |
Eric wrote:
| quote: | | Also nowadays many modern PA amplifiers incorporate internal soft limiting stages and this can help to idiot proof live systems. |
You who do make a living of servicing equipment should be aware that it is impossible to make anything idiot proof since idiots are much too inventive !!! ;)
A friend of mine is doing P.A. work for a living. He is in the sales and rental busines. He once had a customer (small music club) he had sold a processor P.A. (Audio Performance, something like a Swiss made Meyersound P.A.) to.
Some day one of the guys there found out that he can remove a specific cable and that he would have much more bass (it was the control line from the LF poweramp's output to the processor). It didn't last very long though.......
Regards
Charles |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by carlosfm
Guys, I assume this thread was started with a domestic point of view. 50 watts RMS is more than enough for your room.
|
This is a little too blanket. If your speakers are 97db/W/m and your amp's have > 6db dynamic headroom (subjectively not distorted with music) you need only 5 - 6W RMS. Now if your Speakers are 87db/W/m and there is NO or little dynamic headroom (most SS Amp's) you need around 200W....
So, the 25W gaincard with it's around 3db dynamic headroom (very soft supply, sustains only 25W RMS, but handles short peaks of > 50W RMS equivalent) needs at least (in my estimation) 93db/W/m speaker efficiency to allow sufficient dynamic range.
A 50W RMS Amp with no dynamic headroom BTW also needs 93db/W/m speakers....
BTW, this not to say that Gaincard/Gainclone are not good Amp's, HOWEVER, they do not like low impedance speakers or low sensitivity speakers (but then, who apart from Don D'Agostino does and he likes them only because they make him sell his Amp's).
| quote: | Originally posted by carlosfm Anyway, thinking of an ideal amplifier (when are we going to have a wire with gain?:bawling: ), I will point out two main advantages of chip amps:
1. Short signal path.
2. Much less components.
[/B] |
Ahhhm. Actually, most chip amp's have many more parts than most discrete, but of course, you don't see these parts as they are inside the "black box".
For example, contrary to most discrete Amplifiers the NS LM38XX series Amplifiers use current source loads EVERYWHERE possible. Contrary to most dicrete Amp's the NS LM38XX series Amplifiers use Emitter followers (usually current-source loaded) in front of EACH AND EVERY amplification stage, killing (okay, drastically reducing) the effect of the nonlinear Beta (current gain) of the Bipolar trasistors. They also cascode a few things.... All measures that enhance the inherent circuit linearity NO END.
Few discrete circuits can afford that kind of attention to detail and consequent dealing with problems. Also, any "differential pair" in a chip amplifier tends to be tightly matched and tightly thermally coupled....
| quote: | Originally posted by carlosfm Anyway, thinking of an These should theoretically make very hard for you to make a discrete design to be as good as the best chips.
[/B] |
Practically too, for the reasons listed above.
| quote: | Originally posted by carlosfm Anyway, thinking of an BTW, Kuei, your pre was reviewed in Hi-Fi World.:cool:
They say it's very good.[/B] |
Yes, thanks to both MF Audio for making my ideas into products and to HFW for accepting a "hairshirt" passive pre.
Sayonara |
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| nobody special |
| quote: | Anyway, thinking of an ideal amplifier (when are we going to have a wire with gain? ), I will point out two main advantages of chip amps:
1. Short signal path.
2. Much less components.
|
This cracks me up...
As was pointed out, there are many times more components internally in the "little black box".
Minimalist chip amps are a contradiction of terms.
In my opinion, there are two schools of thought when it comes to amplifier design:
1- True minimalist- as in the fewest series gain devices possible, and minimal feedback.
The point being that the fewer gain devices (which, as Nelson Pass says, are most responsible for distortions in the amp) the least amount of damage to the signal.
2- Lowest measured distortion- This school of thought uses all the tricks- current sources, mirrors, active loads, etc. If another stage will lower the distortion, go for it! Feedback in whatever amount gets the job done is acceptable.
Op amps fall into this category, no matter how much (or little) wire you use to hook them up.
I won't be the one to say which is the right way. I guess it depends on who you are, and your preferences. Maybe the truth is somewhere in between?
I fall into the first category, which is inherently discrete by nature. My reasoning is:
1. I believe that greater amounts (but not ridiculous amounts, of course) of low order distortion is preferable to smaller amounts of higher order distortion.
2. I believe that feedback, which is a subtractive process, tends to subtract more than just distortion when overused.
With these "I believes" it sounds a little like religion, and that might not be far from the truth.
Anyway, if I were to build a "type 2" amp, I would probably not bother using discretes, because it is pointless. If you're going to use multiple gain devices, etc. you might as well go with those with the best matching (and all the other benefits mentioned before).
So, my vote is- discretes are better for minimalist techniques, and chips are better when the numbers matter more than the sound.
Just my opinion, of course. |
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| mrfeedback |
| quote: | Originally posted by phase_accurate
Eric wrote:
You who do make a living of servicing equipment should be aware that it is impossible to make anything idiot proof since idiots are much too inventive !!! ;)
A friend of mine is doing P.A. work for a living. He is in the sales and rental busines. He once had a customer (small music club) he had sold a processor P.A. (Audio Performance, something like a Swiss made Meyersound P.A.) to.
Some day one of the guys there found out that he can remove a specific cable and that he would have much more bass (it was the control line from the LF poweramp's output to the processor). It didn't last very long though.......
Regards
Charles |
Yeah, who was it that said there is an idiot born every minute !!!.
Live sound guys are usually pretty responsible so long as the drinks rider is after the show (most live engineers know not to drink on the job - bad for the rep) and DJ's are the worst - if there is a way to overdrive and break a system they will find it - cloth ears and too much chemical enhancement is the cause as I understand it.
Eric. |
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| carlosfm |
| quote: | Originally posted by Kuei Yang Wang
If your speakers are 97db/W/m and your amp's have > 6db dynamic headroom (subjectively not distorted with music) you need only 5 - 6W RMS. Now if your Speakers are 87db/W/m and there is NO or little dynamic headroom (most SS Amp's) you need around 200W....
|
Don't let the specs fool you.
I was very sceptic too, before doing my GC, that they would drive my Epos 11 speakers properly. (8 ohms, 86~87db).
I read the datasheet of the LM3875 and wasn't convinced.
I can tell you I never thought it was possible that these speakers could deliver such an impressive dynamics.
My Nad amp (about the same power) wasn't man enough.
My LM3875 GC is.
I think that more important than power is current delivery.
But even than, the LM3875 is nothing special in this field.
Strange animal...
How could he drive some tiny Tangent 3 speakers (10cm woofers, 87db, 8 ohm) on a 25 square meter room in a way that it made us (I was not alone) preffer their sound to a pair of Tannoy (91db) and a pair of Allison (90db) speakers?
I can't explain this by maths or physics, you really have to listen.
I repeat: it's a strange but beautiful animal.
| quote: | Originally posted by Kuei Yang Wang
Ahhhm. Actually, most chip amp's have many more parts than most discrete, but of course, you don't see these parts as they are inside the "black box".
|
I know:dodgy: .
But still, it's a shorter signal path, isn't it?
It would be impossible to make today a Pentium 4 processor as they did CPUs until about 30 years ago: discrete, on big boards.
And today CPUs are much faster.
Impossible to get with discrete components. |
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| millwood |
| quote: | Originally posted by nobody special
Minimalist chip amps are a contradiction of terms.
|
I agree. my experience with gainclones has not been exactly stellar but I wasn't expecting more to begin with.
However, I do think as a DIYer, discret amps are much fun to work with and give more freedom to the builders.
But if you don't need tons of power, I don't think you can tell the two apart. |
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| nobody special |
| quote: | Originally posted by mrfeedback
Yeah, who was it that said there is an idiot born every minute !!!.
Live sound guys are usually pretty responsible so long as the drinks rider is after the show (most live engineers know not to drink on the job - bad for the rep) and DJ's are the worst - if there is a way to overdrive and break a system they will find it - cloth ears and too much chemical enhancement is the cause as I understand it.
Eric. |
Funny you should mention that...
I had a really interesting experience when my band was playing out one night. The lead singer's friend's band asked us to open for them, as kind of a favor. We showed up, and there were no soundguys anywhere! They had a massive system, made up of mostly JBL stuff, and it was a huge system! We got everything set up, and finally the sound guys show up- drunk off their asses, of course.
We had NO monitors... it sounded completely AWFUL! They were able to make great equipment sound like the worst garbage. It was so bad that the other bands packed up their stuff and left before they were supposed to go on!
I'll never forget that, hehe. |
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| millwood |
| quote: | Originally posted by millwood
But if you don't need tons of power, I don't think you can tell the two apart. |
the other advantage for chip amps is that you are more likely to get consistent results from them. For a 4-channel discret amp, it is much harder. |
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| mrfeedback |
| quote: | | We got everything set up, and finally the sound guys show up- drunk off their asses, of course. |
This is a really good way to ensure that you don't get any live mixing work !.
BTW, it is quite normal for the support act to be intentionally made to sound inferior to the main act.
A muso friend of mine did a support act for a big international touring show and sounded so good that the main act production guys cut him off early half way through his show because he was sounding too good.
Eric. |
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| nobody special |
I had an idea that was the way it was, but the sound was so bad- to the point of being unbearable.
The lead singer of the band we were opening for knew what we were capable of as musicians, because he had just finished recording our demo... I think he was afraid they would sound as bad as we did.
What a night! :bigeyes: :bigeyes: :bigeyes: :bigeyes: |
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| mrfeedback |
In this town turning up late and blind drunk and pulling a bad mix is a guaranteed way to blow your rep bigtime - reports like that travel faster than sound and are pretty much impossible to undo.
A hot babe coming up to the desk and giving you a drink, or going outside for a smoko break during intermissions are fine, but pulling a bad mix because you had too much is considered VERY unprofessional and gets your **** kicked.
Getting sozzled on the job and blowing drivers is unforgivable and the worst rep possible.
Eric. |
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| carlosfm |
| I see you're in shape, Eric.;) |
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| IanHarvey |
It's pretty obvious that the more components in a design, the more opportunities your average constructor has for getting it wrong.
Many components in an amp have a secondary function (such as improving stability, or PSRR, or open-loop linearity) which means they can be wrongly fitted in some way, and the amp will still function, but it just performs poorly. Unless you have decent test equipment and an understanding of each component's function, you'll have a hard time telling apart bad design from bad construction.
If you're asking because this is the first amp you've built, going for a Gainclone or similar is a really sensible idea. It will let you play around with volume pots, layout, wiring, power supplies, connectors etc, safe in the knowledge that most of the hard-to-test bits have been done for you.
If you don't like it, for whatever reason, you can always keep the expensive bits like the PSU and case/heatsink, and replace the LM3875s with something discrete.
Cheers
IH |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by carlosfm
Don't let the specs fool you.
I was very sceptic too, before doing my GC, that they would drive my Epos 11 speakers properly. (8 ohms, 86~87db).
|
Note, I wrote db/W/m and NOT db/2.83V/m. Many modern speakers that show a higher "paper" sensitivity do so by lowering impedance. The ES11 is a pretty Bona Fida 8 Ohm Speaker. However, on any amp I could think on (including NAP135 and NAP 500) it stands no chance to match my Tannoys (Monitor Red 15", 230 Liter Corner Reflex Box) driven by 5 - 6 Watt in terms of maximum loudness (never mind dynamics and LF).
| quote: | Originally posted by carlosfm
My Nad amp (about the same power) wasn't man enough.
|
NAD Amp? Is that Short for "Not A Decent Amplifier"? The 3020 in it's day may not have been exactly bad but other than a cheap favourite was not much to cop. What came after was poorer sound for more money in many cases.
| quote: | Originally posted by carlosfm
How could he drive some tiny Tangent 3 speakers (10cm woofers, 87db, 8 ohm) on a 25 square meter room in a way that it made us (I was not alone) preffer their sound to a pair of Tannoy (91db) and a pair of Allison (90db) speakers?
|
Maybe because the Tangents have a much higher impedance and are less reactive?
| quote: | Originally posted by carlosfm
I repeat: it's a strange but beautiful animal.
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Agreed.
| quote: | Originally posted by carlosfm
I know:dodgy: .
But still, it's a shorter signal path, isn't it?
|
As in physical length of the involved current loops? Yes, of course and that is usually a good thing as well, something I agree upon with Kimura San wholeheartedly.
Sayonara |
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| millwood |
| quote: | Originally posted by Kuei Yang Wang
NAD Amp? Is that Short for "Not A Decent Amplifier"? The 3020 in it's day may not have been exactly bad but other than a cheap favourite was not much to cop. What came after was poorer sound for more money in many cases.
Sayonara |
Well, with a few tweaks, y ou can get excellent sound out of that amp, including that woeful NAD. start with gold-plated resistors, plentium coated caps, tungsgen reinforced heatsinks, 14K white gold jacks, and silver-plated cover, you don't have to worry about those sucky transistors anymore.
BTW, don't forget about using aluminum oxide insulation pads.
:)
As they say in banking, there is no bad amp, just with the right resistors, :) |
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| moamps |
| quote: | Originally posted by millwood
BTW, don't forget about using aluminum oxide insulation pads.
|
Hi,
I saw first time in my life alu-oxid pads in CROWN DC300. Good sounding amp (because of alu pads?:rolleyes:). One ch was dead, I changed output transistors..MJ15003, I guess.
But, 1/4'' jack on input... :(
Regards |
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| fedde |
| quote: | Originally posted by millwood
Well, with a few tweaks, y ou can get excellent sound out of that amp, including that woeful NAD. start with gold-plated resistors, plentium coated caps, tungsgen reinforced heatsinks, 14K white gold jacks, and silver-plated cover, you don't have to worry about those sucky transistors anymore.
BTW, don't forget about using aluminum oxide insulation pads.
:)
|
Sounds like a good start for an amp! Only add some LM3875's and good 1000 uF caps! :nod:
Fedde |
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| janneman |
| quote: | Originally posted by nobody special
[snip]
2. I believe that feedback, which is a subtractive process, tends to subtract more than just distortion when overused.
With these "I believes" it sounds a little like religion, and that might not be far from the truth.
[snip]. |
Steve,
That's OK, as long as you realise that there is no reason why you should only "believe" this. Feedback is quite well known, and anything you want to know about it is either available or can be deduced with a little bit of intellectual effort.
But, as they say, have it your way.
Jan Didden |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by millwood
Well, with a few tweaks, y ou can get excellent sound out of that amp, including that woeful NAD.
|
While I am the first one to admit to using very esotheric military surplus resistors (BTW - as surplus they are around $ 1 each - non inductive wirewound, endcapless construction with the resistor wire welded directly to the leadouts and the leadouts in most cases silver/silver alloy), in case of NAD and many other manufacturers I feel that some basic "common sence" design features (high inherent linearity prior to applying NFB, open loop bandwidth between 1 octave to 1 decade higher than the nominal signal bandwidth, no "sticking" after momentary overload) may actually pay more sonically dividends at much lower cost.
I prefer to get the basics right, before I start fishing at the edge.... BWTFDIK.
Sayonara |
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| millwood |
| quote: | Originally posted by Kuei Yang Wang
I prefer to get the basics right, before I start fishing at the edge.... BWTFDIK.
Sayonara |
I respectibly disagree. As you long as you pay >$1K for your cap and $2K for your resistors, your amp will sound fabulous, regardless of its topology, or build quality.
:)
Oh, don't forget about damping, :) |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by nobody special
2- Lowest measured distortion- This school of thought uses all the tricks- current sources, mirrors, active loads, etc. If another stage will lower the distortion, go for it! Feedback in whatever amount gets the job done is acceptable.
|
Actually, much what you mention helps INHERENT LINEARITY, meaning it stops or reduces alterations to the wholey, holey and only signal. It does so, if well applied without resort to either local or global positive or negative feedback.
| quote: | Originally posted by nobody special
Op amps fall into this category, no matter how much (or little) wire you use to hook them up.
|
Note anything with a positive and negative input plus an applied feedback loop is a "Op-Amp", even the single FET in the PassZen or a single triode with Anode to grid loop feedback.
| quote: | Originally posted by nobody special
I fall into the first category,
|
You mean the category which uses "bad" op-amps with feedback?
I belong to the zeroeth category which regards feedback as a tool to get certain results, which like any tool needs application with care. Feedback is no pankea to solve all problems and in my own system at home I prefer to do without.
From MC Pickup to Speaker Output I have 4 active devices, no feedback, not even "local" feedback, all supplies are unregulated. Of course, most of the time I add a digital equaliser via it's analogue inputs into the mix, which has at least 100's of active stages (real or virtual), loads of Op-Amp's, negative feedback etc.
But of course, I did not design the EQ (I did modify though) I just find it works.
| quote: | Originally posted by nobody special
1. I believe that greater amounts (but not ridiculous amounts,
of course) of low order distortion is preferable to smaller
amounts of higher order distortion.
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Of course. That is 1950's stuff, read Shorter, Olson and Crowhurst from those days when the JAES was not "just toing the party line". There are plenty more publicatiosn. Including some which suggest higher degrees of "ear congruent" distortion can enhance audibility by a process best translated as "residiium hearing"
| quote: | Originally posted by nobody special
2. I believe that feedback, which is a subtractive process, tends to subtract more than just distortion when overused.
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Actually, feedback is NOT a subtractive process. It is ALLWAYS additive.
Secondly, feedback does "subtract" distortion, it redistributes it into different domains (PIM/TIM) and spectrae, hencemy insistence on INHERENT linearity. If nothing goes wrong to start with there is no fallout from fixing it.
Of course, on the additive nature of feedback, the sign of some of the added components may be negative, but the feedback node is ALLWAYS and INHERENTLY additive.
So, at best feedback only adds the signals with signs and magnitudes.
In reality it adds many others... Simply killing the common mode element in this additive process (using inverting mode) helps tremendously, interestingly BOTH objectively and subjectively.
| quote: | Originally posted by nobody special
With these "I believes" it sounds a little like religion, and that might not be far from the truth. |
Actually, it sounds like a completely irrational religion AND it is very far from the truth. At least from where I stand.
| quote: | Originally posted by nobody special
Anyway, if I were to build a "type 2" amp, I would probably not bother using discretes, because it is pointless.
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Agreed. Valves sound much better and in the dark they glow much longer....
| quote: | Originally posted by nobody special
So, my vote is- discretes are better for minimalist techniques,
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Assuming your devices are "good enough", which sadly excludes solid state almost wholesale, Admiral Nelsons protestations ("It's only a fleshwound") nothwithstanding.
Solid state requires the added complexity that makes chips near mandatory to actually work well enough for music. Oh, it requires almost allways some for of (looped) feedback too.
Sayoanra |
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| janneman |
| quote: | Originally posted by millwood
I respectibly disagree. As you long as you pay >$1K for your cap and $2K for your resistors, your amp will sound fabulous, regardless of its topology, or build quality.
:)
Oh, don't forget about damping, :) |
I respectfully declare this total and utterly nonsense. First comes the topology, the type of components (FET? BP? Tubes?) the the detailed diagram, then the implementation. And then IF you get all this optimised, you can indulge in 100$ resistors, and convince yourself it really makes a difference. But make a non-optimal choice in one of the basics, and no amount of money thrown at it makes a difference (except on the price).
Jan Didden
(Yes I know you were only joking, but a lot of people here may actually BELIEVE you, for pete's sake) |
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| carlosfm |
| quote: | Originally posted by millwood
Well, with a few tweaks, y ou can get excellent sound out of that amp, including that woeful NAD. start with gold-plated resistors, plentium coated caps, tungsgen reinforced heatsinks, 14K white gold jacks, and silver-plated cover, you don't have to worry about those sucky transistors anymore.
BTW, don't forget about using aluminum oxide insulation pads.
:)
As they say in banking, there is no bad amp, just with the right resistors, :) |
Well, just for reference, my Nad is a Monitor Series Receiver 7000.
My money couldn't buy better about 12 years ago.
It's extensively tweaked.
Hey millwood, even with all those things you wouldn't go far if you didn't replace those nasty JRC op-amps on the preamp.:devily:
My Nad has OPA2132.:nod:
And it plays very well indeed, but still not enough current/PSU (?) to drive my Epos 11 speakers properly.
But let's say this amp, as it is now, is good hi-fi.
My GC is high-end.:nod: |
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| MarcelvdG |
One disadvantage of chip amplifiers I haven't seen mentioned explicitly yet:
I don't know for sure if this applies to the National Semiconductors chips (I would be surprised if it didn't, though), but with some expensive exceptions, most bipolar IC processes have only very bad lateral PNP's with a very low current handling available. This is in fact why quasi-complementary output stages are so popular in monolithically integrated amplifiers. Making a fully complementary output stage with lateral PNP's would be difficult to do and would require an enormous chip area. |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by MarcelvdG
One disadvantage of chip amplifiers I haven't seen mentioned explicitly yet:
I don't know for sure if this applies to the National Semiconductors chips (I would be surprised if it didn't, though), but with some expensive exceptions, most bipolar IC processes have only very bad lateral PNP's with a very low current handling available. This is in fact why quasi-complementary output stages are so popular in monolithically integrated amplifiers. Making a fully complementary output stage with lateral PNP's would be difficult to do and would require an enormous chip area. |
Actually, not only IC's have usually "bad" PNP Transistors. In virtually ANY "complementary pair" the NPN (or N-Channel) transistor has a higher Beta, better Beta linearity and a higher Ft.
That's solid state for you. There where good reasons why the old masters never made a "P-Channel" Tube....
Sayonara |
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| fdegrove |
Hi,
| quote: | | There where good reasons why the old masters never made a "P-Channel" Tube.... |
LOL...
Man oh man...
Good one Thorsten,;) |
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| Steve Eddy |
| quote: | Originally posted by Kuei Yang Wang
Actually, not only IC's have usually "bad" PNP Transistors. In virtually ANY "complementary pair" the NPN (or N-Channel) transistor has a higher Beta, better Beta linearity and a higher Ft. |
Aye, but then that could be seen as beneficial as it would produce an asymmetry between the pairs increasing second/even order distortion giving it a somewhat more "single-ended" characteristic. :)
se |
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| Kuei Yang Wang |
Konnichwa Eddy San,
| quote: | Originally posted by Steve Eddy
Aye, but then that could be seen as beneficial as it would produce an asymmetry between the pairs increasing second/even order distortion giving it a somewhat more "single-ended" characteristic. :)
se |
Sure.
So, you are saying that all the people who listen to fully complementary Solid State Amp's REALLY only like to listen to distortion? Works for me, Let's run with it....
Sayonara |
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| Steve Eddy |
| quote: | Originally posted by Kuei Yang Wang
So, you are saying that all the people who listen to fully complementary Solid State Amp's REALLY only like to listen to distortion? Works for me, Let's run with it.... |
No, what I said was:
Aye, but then that could be seen as beneficial as it would produce an asymmetry between the pairs increasing second/even order distortion giving it a somewhat more "single-ended" characteristic.
se |
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| SY |
| SE: In other words, the relative distribution of distortion products? 'Course, this doesn't speak to magnitude of the distortion... |
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| JOE DIRT® |
hahaha....been gone for a day...you guys crack me up....welcome to the DIRT club
Cheers!!The DIRT® |
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| Steve Eddy |
| quote: | Originally posted by SY
SE: In other words, the relative distribution of distortion products? 'Course, this doesn't speak to magnitude of the distortion... |
In other words, some prefer whatever distortion there is to lean more toward the second/even order flavor. That's all. I was simply pointing out that the asymmetry of a complimentary pair would produce just that.
se |
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| MarcelvdG |
Kuei Yang Wang,
Discrete PNP's indeed tend to be somewhat slower than discrete NPN's. I'm no device physicist, but I guess this has something to do with the lower mobility of holes compared to electrons.
However, the differences between discrete PNP's and NPN's are totally negligible compared to the differences between vertical NPN's and lateral PNP's in a typical bipolar IC process. A factor of three difference in current gain, a factor of 100 in peak fT and a factor of 100 in current handling capability for devices with similar sizes is not unusual. |
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| carlosfm |
Some people like the distortion of valves.
I think they're good for guitar amps.:devily:
Hey, but that's me.
Deam, some amps in the 80's, before the CD boom, sounded very well with vinyl.
You connected there a CD player and things got very bad, harsh sound.
Then came the return of the valves.:devily: |
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| capslock |
Some of the more modern Sanken, Sanyo, Toshiba, NEC, Moterola devices are amazingly complementary. Sadly, many of these have already gone out of production (the evil influence of surround sound??).
How symmetrical can you get in a quasi-complementary configuration? My impression was always that quasi-complementary was bound to be less symmetrical than a good symmetrical pair.
Regards,
Eric |
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| capslock |
No comments on this? Hey Thorsten, you were the first one here to advocate quasi-complementary. Do you really feel these output stages are superior to a well-matched complementary pair?
Greetings,
Eric |
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| Steve Eddy |
| quote: | Originally posted by capslock
No comments on this? Hey Thorsten, you were the first one here to advocate quasi-complementary. Do you really feel these output stages are superior to a well-matched complementary pair? |
In a quasi-complimentary scheme, a PNP device is still the controlling device so I don't see how you really get away from the NPN/PNP issue.
Personally I've preferred the true complimentary hybrid power opamps over the quasi-complimentary monolithic power opamps that I've tried. Though there are a lot more differences beside the output stage topology so I've really no idea how much is due to the true complimentary nature of the hybrids I've used.
For example, the devices I use (the Apex PA-16 and PA-02) are also a bit unusual in that the output is driven from the collectors of the output devices rather than the emitters.
se |
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| jam |
Sorry to burst your bubble Steve........:D
Regards,
Jam |
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| Steve Eddy |
| quote: | Originally posted by jam
Sorry to burst your bubble Steve........:D |
Howdy, Jam!
Sorry, don't quite get it. Yes you can what? 'Splain. :)
se |
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| jam |
.................or this.
Both designed by Kaneda. |
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| jam |
Steve,
If you look at the schematics you don't see a comp. p and n channel (driver) as in typical quasi comp. designs. The outputs are of the same type and are driven by opposite phases of the second diff amplifier........maybe it is not a true quasi comp. but the goal is still the same.
Regards,
Jam |
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| Steve Eddy |
| quote: | Originally posted by jam
If you look at the schematics you don't see a comp. p and n channel (driver) as in typical quasi comp. designs. The outputs are of the same type and are driven by opposite phases of the second diff amplifier........maybe it is not a true quasi comp. but the goal is still the same. |
Ah, ok. Yeah, they're being driven differentially. Not sure I'd call that quasi-complimentary. At least not in the sense that the phrase is typically understood to mean.
My point wasn't that you couldn't build an output stage using the same polarity device, but that in what's typically understood to be a quasi-complimentary output, you still have a complimentary device controlling one of the output halves. So even if both of your final output devices are N-type, one of them is still going to behave as the P-type that's driving it.
So no bubble burst. But I do have this nasty blister on my thumb you can have a crack at if you'd like. :)
se |
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| thylantyr |
Are Discretes Better Than Chip Amps?
Post a link for a chip amp rated for 500w rms @ 8 ohms,
1 ohm stable, then I will consider it.
:dead: :devilr: :dead: |
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| Steve Eddy |
| quote: | Originally posted by thylantyr
Are Discretes Better Than Chip Amps?
Post a link for a chip amp rated for 500w rms @ 8 ohms,
1 ohm stable, then I will consider it.
:dead: :devilr: :dead: |
Here you go: Apex PA-03
:D
Oops. Sorry. That'll only get you to about 350 watts into 8 with its +/-75 volt rail limitation. However you could always bridge a pair. :)
se |
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| Steve Eddy |
| quote: | Originally posted by jam
I know better than to get into a debate with you..........:D :D :D |
Why you're no fun! :)
Oh, I thought YOU wanted to burst some bubbles. Fine, I'll take care of it myself. Don't say I never offered you anything though. :)
se |
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| Kuei Yang Wang |
Konnichiwa Capslock San,
| quote: | Originally posted by capslock
No comments on this? Hey Thorsten, you were the first one here to advocate quasi-complementary. Do you really feel these output stages are superior to a well-matched complementary pair?
|
Bear baiting, eyh?
Yes, I maintain that a Quasi complementary stage maintains better symmetry UNDER CERTAIN OPERATING CONDITIONS. For example, the slewing of the output stage will be symmetrical as will be the signal related beta drop, as all of these parameters are controlled by the power device.
Having had the chance to compare truely symmetrical N-Channel only Amplifiers against "complementary" ones in Pro Audio applications, plus also quasi complementary ones there is not the least doubt in my mind that the best solution is fully symmetrical (circlotron), followed by quasi complementary and then complementary. Of course, around 70% of the issue is still around implementation, not devices.... And of course, my experiences are 10 - 15 years out of date.
Sayonara |
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| r_s_dhar |
My original intention in posting this question was to get as much and as many practical tips as possible. But, as it always happens, the discussion has turned very technical. It is no ones fault, but less experienced members like me feel left out.
There is an interesting article by Doug Self in one of the issues of that British Journal (Wireless ... something) in which he actually discusses quasi- and fully complementary topologies. I remember him saying that most fully complementary schematics are only complementary geometrically and not much is achieved over quasi-complementary designs.
The proof of the pie is in eating it. So, at the end of the day, what does it hear if you played a musical piece with the widest possible dynamic range? |
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| peranders |
| quote: | Originally posted by r_s_dhar
My original intention in posting this question was to get as much and as many practical tips as possible. But, as it always happens, the discussion has turned very technical. It is no ones fault, but less experienced members like me feel left out. |
It IS very technical :att'n:
Two huge differences are monolithic and matched parts vs. not and good PNP transistors (discrete) or bad integrated.
Those two things are very important and complicated issues.
So the answer will be: No, but it depends what you are after. |
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| peranders |
| quote: | Originally posted by Steve Eddy
Here you go: Apex PA-03
:D
Oops. Sorry. That'll only get you to about 350 watts into 8 with its +/-75 volt rail limitation. However you could always bridge a pair. :)
se |
I read "Tranducer/Audio to 1000 W" in the datasheet (at 2 ohms I suppose) |
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| peranders |
| I have read even closer and the part isn't monolithic, it's a hybrid... and expensive. |
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| Steve Eddy |
| quote: | Originally posted by peranders
I read "Tranducer/Audio to 1000 W" in the datasheet (at 2 ohms I suppose) |
Yup. Thylantyr said 500 into 8 so when I realized it couldn't do that due to the voltage restriction, I amended my post.
But ya gotta agree, that's one mother of a power opamp! :)
se |
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| Steve Eddy |
| quote: | Originally posted by peranders
I have read even closer and the part isn't monolithic, it's a hybrid... and expensive. |
What? Didn't you read? It says "Prices now discounted when purchasing through eStore!" It's only $492.19 for the regular version and $639.86 for the A version! :) Oh, and thylantyr didn't say it had to be cheap. :)
As for it being a hybrid, I'm still not sure just how literally "chip amp" is intended to be interpreted here. Does the chip need to be silicon or can it be ceramic? They're both integrated circuit power opamps. Just add a few external parts, a power supply and you're done.
Can we get a ruling on this from the judges? :)
se |
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| SY |
| It's an IC. The ruling of the judges is final. |
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| fdegrove |
Hi,
| quote: | | It's an IC. The ruling of the judges is final. |
Wasn't too hard now, was it?
How 'bout if we'd put a serious buffer in front of it?
Say a 6C33C? That would kick its' behind, wouldn't it?
Cheers,;) |
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| PeteM |
Hey
Frank you tease.:--)))
Yeh iv'e though about those Russian bottles in the past,so are you cooking.
Peter |
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| PeteM |
Looks like I either build an OTL or a Mig jet then
Peter |
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| fdegrove |
Hi,
| quote: | | Looks like I either build an OTL or a Mig jet then |
Some people enjoy their 6C33C OTLs already...what's keeping you?
I wouldn't know how to build a Mig though...:scratch:
Clever little ****** though, thanks to the valves...
Maybe we should put that 2A3 amp under scrutiny first?
Beaten by a chip....???
Sure enough, I am teasing you...;) |
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| PeteM |
Hi
Frank
>>Some people enjoy their 6C33C OTLs already<<
Yeh I know
>>what's keeping you?<<
The Chip
>>I wouldn't know how to build a Mig though<<
Well I have given it some thought,it's probally esier to buy one already completed.
>>Maybe we should put that 2A3 amp under scrutiny first?<<
Ho thats nothing special.
>>Beaten by a chip....???<<
See Above
>>Sure enough, I am teasing you<<
Two can play that game..funny what the heat can do :-)
Peter |
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| fdegrove |
Hi,
| quote: | | Two can play that game..funny what the heat can do :-) |
Tell me about it...I'm melting...
Now politely returning the thread to the chipheads... ;)
Sorry folks...must be the heat.
Cheers,:drink: :drink: |
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| PeteM |
Your right Frank
Sorry Guy's
Peter
btw Frank I sent email about 2A3. |
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| Steve Eddy |
| quote: | Originally posted by fdegrove
Now politely returning the thread to the chipheads... ;) |
Chipheads? Wasn't that from a song that used to play on the Dr. Demento Show?
Chipheads. Chipheads. Rolly-polly chipheads. Chipheads. Chipheads. Eat them up. YUM!
se |
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| Steve Eddy |
| quote: | Originally posted by SY
It's an IC. The ruling of the judges is final. |
So, in other words, it qualifies as a "chip amp," yes?
se |
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| fdegrove |
Hi,
| quote: | | So, in other words, it qualifies as a "chip amp," yes? |
When it says I.C. and it does amplify, I'd call it a chip amp except when it says "Lays" on the package...
No?
Cheers,;) |
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| Steve Eddy |
| quote: | Originally posted by fdegrove
When it says I.C. and it does amplify, I'd call it a chip amp except when it says "Lays" on the package...
No? |
I see. Works for me. :)
se |
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| jam |
| .....don't forget the dip. |
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| Steve Eddy |
| quote: | Originally posted by jam
.....don't forget the dip. |
Ah, how thoughtless of me. Now we just have to get rid of those Lays and get some tortilla chips! :)
se |
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