carver gear
Well, I said in the original post I wanted to keep the amp discussion out of this, as it tends to get ugly. Let's just say that the amp is a "black box" for this discussion and fits whatever driver(s)/speaker(s) you're using just fine.
That being said, I just can't help saying that I'm baffled (npi) that there are some non-Carver fans out there. I'll be the first to admit that some of the models didn't hit the mark and i wouldn't even buy used off Ebay today, but for the most part, they're a downright steal in terms of $ per watt: cool running, and very clean in/output. Now, I also have to caveat this by saying there are a LOT of various models / years of Carver amps out there, and as someone who has owned at least 20 (currently got about 12 or so) individual amps and having used at least 10 of the various "models", I'll say they do vary greatly by model/year.
Also, a lot of the ones you find today on Ebay and such have been "fixed" by hacks who have no idea what they're doing (slap a cap here, a resistor here, and voila, it works!), so you have to be careful and make sure to qualify before you buy. But if you can get an un-touched Phase Linear 600W per channel for $300 (I usually go lower), you'll end up a VERY happy listener. You may have to do some balanced to unbalanced conversion (I would even suggest some of the boxes that will allow you to still get rid of the noise a balanced run should, then pass it cleaned up right over to the RCA in -- very handy if you have long cable runs as may happen in active xover situations). Anyways, that's JUST MY $.02, please let's not get off on an amp-war -- except as it applies to what you might consider using in different sections of an active xover configuration (how it was brought up, and thanks, it's a very good point).
Well, I said in the original post I wanted to keep the amp discussion out of this, as it tends to get ugly. Let's just say that the amp is a "black box" for this discussion and fits whatever driver(s)/speaker(s) you're using just fine.
That being said, I just can't help saying that I'm baffled (npi) that there are some non-Carver fans out there. I'll be the first to admit that some of the models didn't hit the mark and i wouldn't even buy used off Ebay today, but for the most part, they're a downright steal in terms of $ per watt: cool running, and very clean in/output. Now, I also have to caveat this by saying there are a LOT of various models / years of Carver amps out there, and as someone who has owned at least 20 (currently got about 12 or so) individual amps and having used at least 10 of the various "models", I'll say they do vary greatly by model/year.
Also, a lot of the ones you find today on Ebay and such have been "fixed" by hacks who have no idea what they're doing (slap a cap here, a resistor here, and voila, it works!), so you have to be careful and make sure to qualify before you buy. But if you can get an un-touched Phase Linear 600W per channel for $300 (I usually go lower), you'll end up a VERY happy listener. You may have to do some balanced to unbalanced conversion (I would even suggest some of the boxes that will allow you to still get rid of the noise a balanced run should, then pass it cleaned up right over to the RCA in -- very handy if you have long cable runs as may happen in active xover situations). Anyways, that's JUST MY $.02, please let's not get off on an amp-war -- except as it applies to what you might consider using in different sections of an active xover configuration (how it was brought up, and thanks, it's a very good point).
Re: carver gear
Not many untouched Phase Linears out there... look at them sideways and they blew up. Just another horrid sounding 1970s monster amp, mind you it was way better than a Crown DC300, but still i'd say suitable for gutting and using the chassis. $300 is WAY too much to pay for one.
dave
Not many untouched Phase Linears out there... look at them sideways and they blew up. Just another horrid sounding 1970s monster amp, mind you it was way better than a Crown DC300, but still i'd say suitable for gutting and using the chassis. $300 is WAY too much to pay for one.
dave
Well, I'll have to disagree with our esteemed colleague Dave from Canada regarding Phase Linear gear. No doubt some of the PL gear has been modified. However, to say there are “not many untouched Phase Linears out there” is a gross exaggeration. In the case of the PL400 you’re talking about a 750 watt amp. Thirty years ago you could count on the fingers of one hand the number of companies who made a competitive product. People who bought the amps used them to drive huge systems. They were pushed hard and run hot. Of course some of them cooked. It’s unreasonable to compare the failure rate of this type of amp to someone’s thirty watt Pioneer. We all know the PL amps did not have a DC protection circuit to isolate the speakers in the event of a transistor failure (bad design flaw). This is easily corrected with a $15 Velleman kit. The bad rep, for the most part, was the result of the first generation amps being used by commercial users. You have to remember it was designed for home use. However, they were a generation ahead of anything the rock bands were using. For this reason they were extensively used in concert applications. The amps weren’t designed to be run at those levels for extended periods of time. They overheated and cooked the transistors, then fried the speakers. When Phase Linear realized what was happening they created the Series Two amps. These held up, but still didn’t have DC protection.
The Phase linear amps are no more unstable than any other amp. They were just pushed harder so the second generation (Series Two) were improved. The fact that they blow speakers is true – so add a DC protection card. This is standard fair in most amps today.
To belabor the point: The first generation product failed because they were ridden hard and put away wet. And, they did destroy speakers due to a lack of a DC protection circuit (easily corrected) when a transistor failed.
To hear them referred to as “horrid sounding” astonishes me. I would be willing to put my system (one of the amps is a PL400 Series Two) up against any other (costing under $15K) and defy a listener to point out the horrid sounding Phase Linear amp. Take a look at the spec. sheet, or put a scope on a PL400 and show me the horrid looking output signal. I’m not suggesting they are the greatest amp ever made. I am suggesting they are an excellent sounding amp that earned a reputation thirty years ago because the first generation product was used in a way for which it wasn’t designed, and they didn’t have DC protection. Also consider they are over thirty years old. There have been advancements in transistor technology during that time.
Presently I have five amps (one is in pieces – two of Anthony Holton’s AV400 boards) in my system. As well as a PL400, I also use a PL4000 Series Two preamp. The Autocorrelation circuit that Carver designed is nonsense, but all other aspects of that preamp are outstanding. I don’t have these two pieces because I’m on a budget. I use them for their qualities! I have $3K into a pair of tube mono-blocks. I’m not going to supplement them with horrid sounding gear.
The fact that we can have this debate is testimony to the marvel of the internet. This DIY forum and others like it are such valuable assets to hobbyists and professionals alike!
Dave, this is not meant as a personal attack, or in any way disrespectful. I just want to take the opportunity to share my opinions and experiences.
Don
The Phase linear amps are no more unstable than any other amp. They were just pushed harder so the second generation (Series Two) were improved. The fact that they blow speakers is true – so add a DC protection card. This is standard fair in most amps today.
To belabor the point: The first generation product failed because they were ridden hard and put away wet. And, they did destroy speakers due to a lack of a DC protection circuit (easily corrected) when a transistor failed.
To hear them referred to as “horrid sounding” astonishes me. I would be willing to put my system (one of the amps is a PL400 Series Two) up against any other (costing under $15K) and defy a listener to point out the horrid sounding Phase Linear amp. Take a look at the spec. sheet, or put a scope on a PL400 and show me the horrid looking output signal. I’m not suggesting they are the greatest amp ever made. I am suggesting they are an excellent sounding amp that earned a reputation thirty years ago because the first generation product was used in a way for which it wasn’t designed, and they didn’t have DC protection. Also consider they are over thirty years old. There have been advancements in transistor technology during that time.
Presently I have five amps (one is in pieces – two of Anthony Holton’s AV400 boards) in my system. As well as a PL400, I also use a PL4000 Series Two preamp. The Autocorrelation circuit that Carver designed is nonsense, but all other aspects of that preamp are outstanding. I don’t have these two pieces because I’m on a budget. I use them for their qualities! I have $3K into a pair of tube mono-blocks. I’m not going to supplement them with horrid sounding gear.
The fact that we can have this debate is testimony to the marvel of the internet. This DIY forum and others like it are such valuable assets to hobbyists and professionals alike!
Dave, this is not meant as a personal attack, or in any way disrespectful. I just want to take the opportunity to share my opinions and experiences.
Don
Understood... none of the amps we saw came out of pro work, and there are no SS amps from that era that sound even as good as a well-implemented chip amp... back then i couldn't listen too them... and amps are so much better today there is no comparison.
But what matters is that you can enjoy yours.
As to specs & a scope those are pretty much meaningless when in comes to determining what an amp sounds like.
dave
amps - the not-so-great debate
This pretty much exemplifies why I didn't want to include the amp component as part of the discusssion re active xover's and "total separates" (BTW, I just noticed one of the Linn AV designed speakers had front floor-standing models which could be tri-amped and xover bypassed, very interesting).
However, the statement re amp specs having little to do with how good they sound (they shouldn't "sound" at all, ideally they should just amplify) from someone who is apparently a moderator really took me for a loop.
Um, if you're going to ignore little things like THD (+N) and/or S/N ratios when comparing amps, then what criteria would you use to determine which one(s) to begin listening to in order to decide what you like? You listen to all 1000+ models individually?
I truly find such a statement baffling and hopefully not a sign that "subjectivism" (as defined in many of Stone's and Self's books) has made further in-roads into the DIY segment (perhaps that's what happened to Stone, he finally threw his hands up in disgust and said "here, pay $4000 for what you can make for $1000, I'll put it in a pretty box with a nifty name like "ZUS" if you will!").
The DIY segment used to be about what was real and measurable (aka "science") not what had "warm undertones that are felt more than heard". Unfortunately, as I get "back into" (after a 20 year or so absence -- ah yes, I still had a Heathkit catalog up until not long ago) I see that's exactly what's happened. Now we have DIY "ultra cables" that you can make for a mere $50 a piece on your own, a fraction of what they'd cost retail! Part of me laughs myself silly when I see such things, and part of me sags and watches unfettered commercialism creep into every nook and cranny of our lives, even the parts that are supposed to be "cheap hobbies".
"Pretty much meaningless"??? I really have no response except slapping my forehead for owning such silly tools as signal generators, RTA's, and 'scopes. Shoot, what an idiot I am. Tell me how many watts/channel you want and with one coil (wound to order with secondaries separated by a helium-gas filter barrier) and a handfull of resistors, transistors, and some heatsink and I can I build you all the watts you'll ever need for a home system for about 10 cents a watt! I know, I'll call them Zen Minimalist Mark IV's and make a killing!
[Rant Mode OFF] Sorry, it's been building up for the last few months. For more info, google "Cashebo effect", that's all you need to know.
This pretty much exemplifies why I didn't want to include the amp component as part of the discusssion re active xover's and "total separates" (BTW, I just noticed one of the Linn AV designed speakers had front floor-standing models which could be tri-amped and xover bypassed, very interesting).
However, the statement re amp specs having little to do with how good they sound (they shouldn't "sound" at all, ideally they should just amplify) from someone who is apparently a moderator really took me for a loop.
Um, if you're going to ignore little things like THD (+N) and/or S/N ratios when comparing amps, then what criteria would you use to determine which one(s) to begin listening to in order to decide what you like? You listen to all 1000+ models individually?
I truly find such a statement baffling and hopefully not a sign that "subjectivism" (as defined in many of Stone's and Self's books) has made further in-roads into the DIY segment (perhaps that's what happened to Stone, he finally threw his hands up in disgust and said "here, pay $4000 for what you can make for $1000, I'll put it in a pretty box with a nifty name like "ZUS" if you will!").
The DIY segment used to be about what was real and measurable (aka "science") not what had "warm undertones that are felt more than heard". Unfortunately, as I get "back into" (after a 20 year or so absence -- ah yes, I still had a Heathkit catalog up until not long ago) I see that's exactly what's happened. Now we have DIY "ultra cables" that you can make for a mere $50 a piece on your own, a fraction of what they'd cost retail! Part of me laughs myself silly when I see such things, and part of me sags and watches unfettered commercialism creep into every nook and cranny of our lives, even the parts that are supposed to be "cheap hobbies".
"Pretty much meaningless"??? I really have no response except slapping my forehead for owning such silly tools as signal generators, RTA's, and 'scopes. Shoot, what an idiot I am. Tell me how many watts/channel you want and with one coil (wound to order with secondaries separated by a helium-gas filter barrier) and a handfull of resistors, transistors, and some heatsink and I can I build you all the watts you'll ever need for a home system for about 10 cents a watt! I know, I'll call them Zen Minimalist Mark IV's and make a killing!
[Rant Mode OFF] Sorry, it's been building up for the last few months. For more info, google "Cashebo effect", that's all you need to know.
planet10 said:
Dave, lets split this off.
I understand that you have a different world view than I do, so I am only asking you to understand others perspective, not necessary embrace it.
First, a history lesson. THD was a moderately good predictor of sound quality in Williamson style Tube Push Pull amps with about 20 db of feedback. This also extended to the tube preamps of the day (1955) , to a lesser degree. So far, so good.
When the first generation solid state amplifiers were designed, some of the possible distortion mechanisms were not well understood. This was partially because the output transforms limited the feedback possible. Freed of this limitation, the solid state designers were free to apply large amounts of feedback.
Basically, this caused issues that were audible, but not measurable using a THD meter. No disrespect, but my personal belief is that the PL400 was the worst commercial amplifier ever built. If I understand correctly, the PL400 was run in "near class B", and had rising THD at low power, due to severe crossover distortion. I heard one in traverse City in 1977 with a Klips horn that drove me from the building. In retrospect that was a worst case pairing.
The last 30 years some engineers have looked for a new figure of merit, to replace THD. Along this road, there have been several discoveries of distortion mechanisms. TIM, or transient intermodulation comes to mind. None have been widely adopted.
Go read the Firstwatt F1 manual Here
To Obi Wan you listen.
By the way, Dave is an excellent engineer with a well deserved reputation. Its not about subjectivism as much as determining what is used by marketing, but is no longer a reliable indicator of sound quality.
They were referred to as "fresh outs" and were generally laughed at, mostly behind their backs.
I suggest that anyone with an interest in the science of amplifiers could do a lot worse than to hang out on the DIYaudio Solid State, Tube and Pass Labs forums and get an idea what the community consider important.
Doug Lockwood
I understand that you have a different world view than I do, so I am only asking you to understand others perspective, not necessary embrace it.
First, a history lesson. THD was a moderately good predictor of sound quality in Williamson style Tube Push Pull amps with about 20 db of feedback. This also extended to the tube preamps of the day (1955) , to a lesser degree. So far, so good.
When the first generation solid state amplifiers were designed, some of the possible distortion mechanisms were not well understood. This was partially because the output transforms limited the feedback possible. Freed of this limitation, the solid state designers were free to apply large amounts of feedback.
Basically, this caused issues that were audible, but not measurable using a THD meter. No disrespect, but my personal belief is that the PL400 was the worst commercial amplifier ever built. If I understand correctly, the PL400 was run in "near class B", and had rising THD at low power, due to severe crossover distortion. I heard one in traverse City in 1977 with a Klips horn that drove me from the building. In retrospect that was a worst case pairing.
The last 30 years some engineers have looked for a new figure of merit, to replace THD. Along this road, there have been several discoveries of distortion mechanisms. TIM, or transient intermodulation comes to mind. None have been widely adopted.
Go read the Firstwatt F1 manual Here
To Obi Wan you listen.
By the way, Dave is an excellent engineer with a well deserved reputation. Its not about subjectivism as much as determining what is used by marketing, but is no longer a reliable indicator of sound quality.
When I worked for Motorola as a test engineer in the 80's, recent graduates from engineering school had the same beliefs.
They were referred to as "fresh outs" and were generally laughed at, mostly behind their backs.
I suggest that anyone with an interest in the science of amplifiers could do a lot worse than to hang out on the DIYaudio Solid State, Tube and Pass Labs forums and get an idea what the community consider important.
Doug Lockwood
Re: amps - the not-so-great debate
The single number THD commonly published is pretty much useless in determining the sonics of amplifiers... i'm surprised people are still clinging to it.
THD measurements themselves can be an indicator of amplifier quality, but you have to look at the amplifiers full spectrum. This is a chart not a number. The relationship of the harmonics is critical. An amplifier that has only 2nd and 3rd harmonics with 2nd higher than 3rd, is very likely to sound better than an amplifier with measureable quantities of 4th, 5th, and higher harmonics even if when the spectrum is collapsed into a single number the 1st amp has 1% distrotion and the 2nd 0.001% distortion. If the spectrum is not published then the THD measurements are meaningless.
Measurements as they are currently done will only tell us if there is something grossly wrong. 1st off most of them are made with steady state periodic signals -- usually sin waves. There is a lot of places to hide if all you have as a torch are sin waves. Tests done with more complex signals can be much more revealing, but you won't find many of those on the spec sheet. Something like the 5-cycle burst. You still have to be able to interpret the results -- you won't fins a single number.
Also since these tests are all steady state, they tell us little about what is happening 40 dB (or more) down from the test signal level -- this is the area where the good is separated from the excellent.
And yes, i have probablu listened to 1000 amplifiers.
dave
tlparker said:
The single number THD commonly published is pretty much useless in determining the sonics of amplifiers... i'm surprised people are still clinging to it.
THD measurements themselves can be an indicator of amplifier quality, but you have to look at the amplifiers full spectrum. This is a chart not a number. The relationship of the harmonics is critical. An amplifier that has only 2nd and 3rd harmonics with 2nd higher than 3rd, is very likely to sound better than an amplifier with measureable quantities of 4th, 5th, and higher harmonics even if when the spectrum is collapsed into a single number the 1st amp has 1% distrotion and the 2nd 0.001% distortion. If the spectrum is not published then the THD measurements are meaningless.
Measurements as they are currently done will only tell us if there is something grossly wrong. 1st off most of them are made with steady state periodic signals -- usually sin waves. There is a lot of places to hide if all you have as a torch are sin waves. Tests done with more complex signals can be much more revealing, but you won't find many of those on the spec sheet. Something like the 5-cycle burst. You still have to be able to interpret the results -- you won't fins a single number.
Also since these tests are all steady state, they tell us little about what is happening 40 dB (or more) down from the test signal level -- this is the area where the good is separated from the excellent.
And yes, i have probablu listened to 1000 amplifiers.
dave
Re: amps - the not-so-great debate
But what goes for measurements on the spec sheets is pretty shallow, and far from complete science.
Maybe an analogy will help... take water... science is knowing that this is 2 hydrgen atoms & an oxygen atom, how it reacts chemically, what the electron cloud looks like, etc, not it looks bluish-green in the sea, but clear in the glass, it is wet, good to drink if from a stream, not so good to drink if from the sea... the current state of measuremnet as seen on spec sheets is analogous to the latter.
A simplier analogy. The world must be flat because it looks flat.
I am not against measurements, but one must very much keep in mind that measurements (as usually seen) are very limited and hardly scratch the surface of what is there. Real science is recognizing those limitations and forging ahead to develop techniques that do correlate with what we percieve. What you see on the spec sheets are not that far removed from a state of advancement akin to when barbers were starting to be disqualified from the doctoring business.
dave
tlparker said:
But what goes for measurements on the spec sheets is pretty shallow, and far from complete science.
Maybe an analogy will help... take water... science is knowing that this is 2 hydrgen atoms & an oxygen atom, how it reacts chemically, what the electron cloud looks like, etc, not it looks bluish-green in the sea, but clear in the glass, it is wet, good to drink if from a stream, not so good to drink if from the sea... the current state of measuremnet as seen on spec sheets is analogous to the latter.
A simplier analogy. The world must be flat because it looks flat.
I am not against measurements, but one must very much keep in mind that measurements (as usually seen) are very limited and hardly scratch the surface of what is there. Real science is recognizing those limitations and forging ahead to develop techniques that do correlate with what we percieve. What you see on the spec sheets are not that far removed from a state of advancement akin to when barbers were starting to be disqualified from the doctoring business.
dave
Re: amps - the not-so-great debate
Of course they cost a fraction of the cost of retail... you have to consider the realities of business... lets say i want to retail a cable like you built. I'm buying in bulk so you $50 worth of parts costs me $20. But labour isn't free, add (at least) $20 to that, packaging, packing, rent, capital (soldering irons etc), rent, someone to keep the books, R&D, promotion, warranty, add another $40... so the cable costs me $80 (probably low). I need to make a profit, so make it $20. That is pretty skinny, and i'd have to sell lots & lots so lets make it $125 so i can stay in business. Often there is a distributor, he needs to make at least 20 points, so wholesale price to the dealer is at least $160. Cables are a point-of-sale item (ie the little things that mean the difference between staying in business or not), so retail on these is going to be at least $320.
This analysis applies to almost everything you buy in a store.
Now cables are a particularily contentious area because there is a lot of snake-oil and people taking advantage of the (largly male) mine is bigger than yours, keeping ahead of the jones kinda attitude to life. Some of them are worth the tariff, some aren't and it is often very hard to tell which is which because there is a huge amount of system interaction.
dave
Of course they cost a fraction of the cost of retail... you have to consider the realities of business... lets say i want to retail a cable like you built. I'm buying in bulk so you $50 worth of parts costs me $20. But labour isn't free, add (at least) $20 to that, packaging, packing, rent, capital (soldering irons etc), rent, someone to keep the books, R&D, promotion, warranty, add another $40... so the cable costs me $80 (probably low). I need to make a profit, so make it $20. That is pretty skinny, and i'd have to sell lots & lots so lets make it $125 so i can stay in business. Often there is a distributor, he needs to make at least 20 points, so wholesale price to the dealer is at least $160. Cables are a point-of-sale item (ie the little things that mean the difference between staying in business or not), so retail on these is going to be at least $320.
This analysis applies to almost everything you buy in a store.
Now cables are a particularily contentious area because there is a lot of snake-oil and people taking advantage of the (largly male) mine is bigger than yours, keeping ahead of the jones kinda attitude to life. Some of them are worth the tariff, some aren't and it is often very hard to tell which is which because there is a huge amount of system interaction.
dave
Doug, there are multiple opinions on the "sound" of amplifiers. Self's has the signal advantage of having some verifiable evidence behind it, but there's certainly no definitive answer.
John Atwood gave an interesting talk at ETF05 on correlating subjective preference with measurements, which included a late '70s Pioneer receiver. I'll see if I can dig up a link to it.
My own opinion is that the standard set of test measurements used in magazine articles is highly incomplete, and the "no clipping" restriction on amp comparisons is more onerous than most people think. Important factors often omitted include the distortion spectrum, overload and recovery issues, and performance into various reactive loads. They're all doable tests and yield useful information, but don't fit into the neat format that manufacturer spec sheets have conditioned us to expect.
Don't worry about voodoo and BS over-running the diy community- that happened decades ago.
edit: link to John's presentation:
http://www.one-electron.com/etf5_talk.ppt
John Atwood gave an interesting talk at ETF05 on correlating subjective preference with measurements, which included a late '70s Pioneer receiver. I'll see if I can dig up a link to it.
My own opinion is that the standard set of test measurements used in magazine articles is highly incomplete, and the "no clipping" restriction on amp comparisons is more onerous than most people think. Important factors often omitted include the distortion spectrum, overload and recovery issues, and performance into various reactive loads. They're all doable tests and yield useful information, but don't fit into the neat format that manufacturer spec sheets have conditioned us to expect.
Don't worry about voodoo and BS over-running the diy community- that happened decades ago.
edit: link to John's presentation:
http://www.one-electron.com/etf5_talk.ppt
well i can hardly believe the predudice here we were all learning in the 60s and 70s the technology was new and affordable! Mr joe average was luckY to have a single el84 and a cheap output transformer prior to these amps .
Some of the finest sounds I heard were from these amps
the early Leaks when paired with a sensistive speaker could sound very nice.
The QUAD 303 still hold its own even today!
Some of the early Radfords were good my personal fav was the Rogers Ravensbourne
I have just imported a Phase linear 400b from the states and with my B+W speakers it is a wonderfull sounding amplifier !!!
The things that we are building now are nothing more than evolved designs from this early stuff,That is apart from the class D boys
Regards Trev
Some of the finest sounds I heard were from these amps
the early Leaks when paired with a sensistive speaker could sound very nice.
The QUAD 303 still hold its own even today!
Some of the early Radfords were good my personal fav was the Rogers Ravensbourne
I have just imported a Phase linear 400b from the states and with my B+W speakers it is a wonderfull sounding amplifier !!!
The things that we are building now are nothing more than evolved designs from this early stuff,That is apart from the class D boys
Regards Trev
Well, transistor technology has evolved a lot in the last decades ; just compare the old 2N3055 which was featured in more than a few poweramps of the time to modern power transistors...
Some of the problems of older models of power transistors :
1- slower to switch from blocked to linear mode (creates crossover distortion in non-class A amps)
2- hFe (ie. current gain) would decrease substantially when current rises high, which means the driver has to work harder, and the open-loop is less linear, ie. more distortion (this is called Beta Droop)
3- high capacitance and slow speed, meaning the open loop gain at 20 kHz was small and feedback couldn't correct the massive crossover distortion introduced at point 1
Hence, yeah, a power amplifier made with these old transistors will suck more than one made with recent, fast transistors which can sustain their gain at high currents. It's pretty logical.
And the opamps of the time sucked a lot more than that (remember the 741 ?), and there were a lot of them in tone controls and preamps...
Some of the problems of older models of power transistors :
1- slower to switch from blocked to linear mode (creates crossover distortion in non-class A amps)
2- hFe (ie. current gain) would decrease substantially when current rises high, which means the driver has to work harder, and the open-loop is less linear, ie. more distortion (this is called Beta Droop)
3- high capacitance and slow speed, meaning the open loop gain at 20 kHz was small and feedback couldn't correct the massive crossover distortion introduced at point 1
Hence, yeah, a power amplifier made with these old transistors will suck more than one made with recent, fast transistors which can sustain their gain at high currents. It's pretty logical.
And the opamps of the time sucked a lot more than that (remember the 741 ?), and there were a lot of them in tone controls and preamps...
Re: Re: amps - the not-so-great debate
My point was that a $500 cable is ridiculous. Name me one single double-blind, scientifically and statistically properly arranged test on one of these $500-in-a-wood-box cable vs. any Canare or similar I can make for $20 (I consider Canare's to be high-end "audiophile" -- I always test each one after making it, for many parameters as if you don't get it just right, you can make a lesser-quality cable than when it is done perfectly).
Again, just google "cashebo effect" and get back to me. I retired at 36 years old as CTO of an internet company. Had a lot of Ph.D's working for me. I never had a minute of college education. I went from engineering to product management (for a fortune 100 company whose name you'd instantly recognize) to CTO of a publicly traded internet company. I understand to the nth degree product management. When people refer me to go hang in the "tube amp" and "high end vinyl" areas to understand what The Community Thinks Is Important only tells me that there are a lot of companies and people doing good product management work. If I see another turntable review which mentions in the first paragraph how beautiful it LOOKS, I'll cry. None of them will win a double-blind test against my 20 year old re-built Pioneer with its scratched up cover.
Science is fairly simple. Do some double-blind studies. Go to http://www.badscience.net/?p=209 and begin to understand what I'm talking and concerned about. The DIY community used to have a fairly decent "firewall" between itself and the retail hucksters. Instead, now you see DIY stuff that talks about silver-wrapped low-dieletric home-made cables (which would never pass a double-double study). Of course, the site will sell you all the stuff you need to make these wonderful cables for several hundred dollars. Oh, the irony.
Back to amps on this all-over-the-map-rant. To suggest that THD (I notice you didn't dissmiss S/N ratios, which I also mentioned, or sensitivity, SPL's, etc.) is no longer a worthwhile measurement means you'd never used a signal generator and analyzer. Yes, values should be shown as a full graph, ideally from 10hz to 50khz or so (now that folks like Stone are saying that below 20 and above 25k COUNT, even though we can't hear them), but I do see many mfr's now showing THD's for at least 3-4 different freq's across the spectrum, which is certainly a move in the right direction. Maybe some day we'll see tone controls come back to amps (or, better yet, lpads on the back of speakers built into the xover, where they belong). "Huge amount of system interaction" -- all of which are measurable by complex things like resistance/impdence, THD, etc. If you can't get past the cashebo effect, then we'll just have to agree to disagree.
PS: DISTRIBUTORS making AT LEAST 20 points?!?!? If anything ever showed a lack of real business knowledge. And EVERYTHING is "point of sale" that is being sold (good grief, it used to refer to the type of terminal). It's the IMPULSE items (you know, the ones on the end-caps, if you know what that means) that are the little things that make the margin, depending on your business model. A high-end AV boutique does not have the same model as Best Buy, but that's obviously too complex for this discussion.
PPS- Is there a way to change my user id to Cashebo-killer.
My point was that a $500 cable is ridiculous. Name me one single double-blind, scientifically and statistically properly arranged test on one of these $500-in-a-wood-box cable vs. any Canare or similar I can make for $20 (I consider Canare's to be high-end "audiophile" -- I always test each one after making it, for many parameters as if you don't get it just right, you can make a lesser-quality cable than when it is done perfectly).
Again, just google "cashebo effect" and get back to me. I retired at 36 years old as CTO of an internet company. Had a lot of Ph.D's working for me. I never had a minute of college education. I went from engineering to product management (for a fortune 100 company whose name you'd instantly recognize) to CTO of a publicly traded internet company. I understand to the nth degree product management. When people refer me to go hang in the "tube amp" and "high end vinyl" areas to understand what The Community Thinks Is Important only tells me that there are a lot of companies and people doing good product management work. If I see another turntable review which mentions in the first paragraph how beautiful it LOOKS, I'll cry. None of them will win a double-blind test against my 20 year old re-built Pioneer with its scratched up cover.
Science is fairly simple. Do some double-blind studies. Go to http://www.badscience.net/?p=209 and begin to understand what I'm talking and concerned about. The DIY community used to have a fairly decent "firewall" between itself and the retail hucksters. Instead, now you see DIY stuff that talks about silver-wrapped low-dieletric home-made cables (which would never pass a double-double study). Of course, the site will sell you all the stuff you need to make these wonderful cables for several hundred dollars. Oh, the irony.
Back to amps on this all-over-the-map-rant. To suggest that THD (I notice you didn't dissmiss S/N ratios, which I also mentioned, or sensitivity, SPL's, etc.) is no longer a worthwhile measurement means you'd never used a signal generator and analyzer. Yes, values should be shown as a full graph, ideally from 10hz to 50khz or so (now that folks like Stone are saying that below 20 and above 25k COUNT, even though we can't hear them), but I do see many mfr's now showing THD's for at least 3-4 different freq's across the spectrum, which is certainly a move in the right direction. Maybe some day we'll see tone controls come back to amps (or, better yet, lpads on the back of speakers built into the xover, where they belong). "Huge amount of system interaction" -- all of which are measurable by complex things like resistance/impdence, THD, etc. If you can't get past the cashebo effect, then we'll just have to agree to disagree.
PS: DISTRIBUTORS making AT LEAST 20 points?!?!? If anything ever showed a lack of real business knowledge. And EVERYTHING is "point of sale" that is being sold (good grief, it used to refer to the type of terminal). It's the IMPULSE items (you know, the ones on the end-caps, if you know what that means) that are the little things that make the margin, depending on your business model. A high-end AV boutique does not have the same model as Best Buy, but that's obviously too complex for this discussion.
PPS- Is there a way to change my user id to Cashebo-killer.
planet10 said:
latala said:
I agree, I had a Leak Stereo 70 for many years, a lovely little amp - it had some power as well, I used it as a disco and guitar amp at times as well as home stereo. In fact I've even seen Stereo 70's used as in-house PA in clubs (in multiples).
Saw a band once that had a stack of Quad 303's for the PA, certainly well over ten of them - and they had been GIVEN to them! - (I can still remember one had all the top caved in where it had been dropped)
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