The sonic merits of late '70s SS amps

[tlparker]

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).

[planet10]

Originally posted by tlparker
I just can't help saying that I'm baffled (npi) that there are some non-Carver fans out there

In the late '70s, early '80s the hifi shop i worked in brought the Carver stuff in... after playing with it and evaluating, i won't touch the stuff... all fluff with no substance. (well maybe if it was cheap enuff to gut and use the chassis).

dave

[planet10]

Originally posted by tlparker f 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.

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

[BobEllis]

In the 70s I thought Crown named their amp models after the number and type of amps that they would put into your speakers.

[HipoFutura]

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

[planet10]

Originally posted by HipoFutura 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.

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

[tlparker]

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.

Originally posted by planet10


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

[DougL]

Dave, lets split this off.

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.

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.

"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!

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.

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!").

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.

The DIY segment used to be about what was real and measurable (aka "science")

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

[planet10]

Originally posted by tlparker
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?

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

[planet10]

Originally posted by tlparker
The DIY segment used to be about what was real and measurable (aka "science")

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