Which watts are the right watts in SS amps?

Wolcott Audio tube amp:
http://www.wolcottaudio.com/WA_Pres_why.htm
http://www.wolcottaudio.com/WA_Pres_specs.htm
Best tube amp?

I'm not sure I've ever seen any transformer coupled amp show damping over 100 into 8 ohm. I'm also not convinced that the drawbacks of feedback are so bad it should be completely avoided. I feel like thats a knee jerk reaction like many people have about guns. It's just a tool to be used.

The thing about feedback is there are more variables than the formula taught in school! You have to deal with RFI being injected into the amp via the speaker cables (and most designs don't...) and the amp has to have sufficient phase margins prior to application of the feedback... here is a great article about how to apply feedback properly:
http://www.normankoren.com/Audio/FeedbackFidelity.html

Since feedback is rarely applied with this sort of care, its incorrect to say that eschewing it is a 'knee jerk' reaction. Its misapplication is audible!

With regards to speakers, there is never a need for 100:1 (or more) damping; almost any speaker made is overdamped with a damping factor that high. Here is another great article that despite its age has stood the test of time, written by the head engineer of Electro Voice:
http://www.dissident-audio.com/Loudspeakers/CriticalLSDamping.pdf

Note that at the time of this article, there were speakers that needed far less damping than even 5:1, and there are still speakers around today that barely need that or even less (as an example, Nelson Pass demonstrated a small yet very impressive open baffle speaker at RMAF about 10 years ago that was driven by a current source amplifier, so the damping factor in that system was less than 1:10 and you did read 1:10 correctly, yet it played bass quite well).

It was Electro Voice and MacIntosh that led the way in championing the idea that the amplifier should be a voltage source and the speaker voltage-driven, back in the late 1950s and into the 1960s. But the simple fact is that this model simply did not and does not encompass all speakers and speaker technologies (any speaker that does not employ a cabinet would be an example, as well as many speakers that do have cabinets..). In addition, all amplifiers that are capable of acting as a voltage source are push-pull, and such amps (with rare exception) have distortion characteristics wherein the distortion actually **increases** below a certain minimum power level, typically about 5-7% of full power. So if you use a speaker that is too efficient for the amp, you will not be getting the best sound out of it.

The voltage model is intended to eliminate equipment matching issues, and if you are only interested in box store mid fi, none of this is a problem. But in high end audio there is quite a bit of diversity such as planar speakers, horns, full range devices as well as more conventional designs, SETs, OTLs, class A, class D, etc. because everyone is approaching the goal of electronics sounding like real music in a different way. So if you apply a generalization such as 'all amps should be voltage sources' right away it is belied by very notable exceptions!

The bottom line is that equipment matching is still very much with us and won't be going away anytime soon.

I’m also not convinced that the drawbacks of feedback are so bad it should be completely avoided.

A little story about feedback.

An output transformer "GOD" wound up some very nice massive cores for a friend of mine who was his buddy cost no object, interleaved to the hilt. I ended up with these cores when he passed away.
The transformer "GOD" I got in touch with and he got me to get some special C-Cores from Egypt where apparently is the best silicon. These transformers could be changed via the separate interleaved winding tabs for 16,8,4,2,and even 1ohm.

They sounded magnificent on a big pair of 150w tube monos I had, and I decided that maybe because the transformer were that good that there was maybe no need for feed back to help them have a lower output impedance. So I put on a variable feedback pot that could be changed from 30db down to zero. Adjusting the volume for the change in gain, it was clear as a bell that zero feed back was by far the best and because the transformers were that good the bass remained tight and dry.

So that proved to me, feedback is good in tubes to get better bass with lower output impedance, but it does have a negative effect on the rest of the music.

Cheers George 

Go ahead and spend gobs of money on those pure class A amps that burnout after 7-10 years

Any truth to this? (i.e. is a class A amps life span known to be less than other designs)

If so, is there anything that can/should be done from a practical perspective to prolong the longevity of a class A amp?

Thanks.

If so, is there anything that can/should be done from a practical perspective to prolong the longevity of a class A amp?

Thanks.

Keep them biased right, Pass recommends palm hand test on the hottest part of the heatsinks being able to keep them pressed for at least 6 seconds (no brickies hands) any shorter and it’s running too much Class-A, and also keep them in a well ventilated spot.

Cheers George

Go ahead and spend gobs of money on those pure class A amps that burnout after 7-10 years

Any truth to this? (i.e. is a class A amps life span known to be less than other designs)

No. We've been making class A amps for the last 41 years, and recently serviced one that had been in the field since 1988.

Just make sure that they can get adequate cooling and they are fine.

I'd like the process of component pairing to be less guess work and more analysis.

Me too- but its not going to happen unless the audio industry cares enough about quality of reproduction to address the shortcuts (including measurement issues) that have been taken so often in the last 50 years. Until then, equipment matching is a thing :/

The right watts are what you hear in the showroom that impressed you enough to buy the amp in the first place.  The rest of the watts are what you hear at home when you try to get the amp to sound as good as when you laid out that hard-earned cash.

Imhififan > Wolcott.

Blindjim > Thanks. Nice thoughts.
I thought they quit making these amps. I looked hard at it many years ago as a choice. I think then however, the cost was out of reach very likely as they seldom if ever appear on the used pages for sale.
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@stfoth > I often tell them not to overthink it and just order a decent Champagne, especially on a date or in a group. 95% idiot-proof.

Blindjim > thanks much. I tend to agree. I suspect this should be the ‘default’ answer for anyone who is either in doubt as to which way to upgrade, update, or just start a first audio build in terms of which amp to go with, keeping budgetary considerations in mind.
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@atmasphere > all amplifiers that are capable of acting as a voltage source are push-pull, and such amps (with rare exception) have distortion characteristics wherein the distortion actually **increases** below a certain minimum power level, typically about 5-7% of full power. So if you use a speaker that is too efficient for the amp, you will not be getting the best sound out of it.

Blindjim > thanks for the links and observations. outstanding.
Ralph, why do you have to make this affair harder,? Lol

First 5 – 7%? I’ll presume this initial area pertains directly to the scenario you presented, otherwise, isn’t the first 10 – 20% of a class AB amp where one finds Class A functionality, and many adore that area of operation.

As for Damping, referring to another article from a JBL rep I saw online written some time back, the idea of rated damping factors is nearly fantasy when viewed practically vs rated given so many factors can and do intervien altering the amps ability to actually perform damping.
I read another one from a different source but a likewise quite technically oriented soul which is more recent but collaterally confirms damping ratings as nearly superfluous when put to practice. IOW picking amps based on damping ratings is not a true key spec one should lean on too heavily or at all.

Atmas > The bottom line is that equipment matching is still very much with us and won't be going away anytime soon.

Blindjim > lovely. And after all that great technical data, it comes to that? Super. ;-))
Many thanks.
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@gdhal > anything that can be done to extend Class A amp longevity?

Blindjim > as was said, ventilation.
Better still…. control the ambient temperature better immediately about the amp. Make the joint sweater wearing listening, or place the amp into an area where its quite cold via a dedicated AC. Heat kills. Especially extensive, and extended applications of it. Also, running it only in advance of listening sessions seems a prudent course of action, and in the interim keep a signal passing thru it as no signal allows it/them to produce their excessive temps given the way they operate in signal vs no signal eff.

I mean, if a pair of class A mono is gonna run ya $20K to God knows K, maybe spending a grand or two for extra cooling aint’ such a bad idea.

It is also why I like and use the idea of placing amps into an area apart from the listening room and cooling that area independently, and use remote extenders for operation.

I simply used an adjacent room and used longer speaker cables.

Later, I enclosed off a section of the listening room so a space was allowed for everything to be in that walk in closet like area accessed by bi fold doors in the middle of a false wall.

In either case, AC cools things quite well.
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IMO The number one issue with any and all of this speculation, rhetoric, and suspense is due to the lack of proliferation of the products sought, and the likely bigger attribute deeply set into the being of the audio possessed psyche who constantly notices the grass is, or might be greener on the other side.

Often we can’t just waltz across town to listen to the apple of our eyes. Usually the ??? piece is far far away making it more a dream or fantasy than a real option.

Distance however, does not prevent one from thinking, or believing that logistically out of reach piece either ‘is’ or could be the solution!

The mind is a terrible thing!

The scenario changes drastically and becomes a real quagmire when this same fool (meaning ‘me’) decides he wants to reroute his path from the SS highway and take a more scenic glass powered state road byway instead.

‘to thine own self be true’.Nice to hear perhaps, lots harder to do. ‘Once bitten, twice shy’ comes to mind during that wrestling match with being true to myself. The shoulders which get pinned to the mat are always the ones appealing SS power. despite their simpler nature and how they can be amended, they keep losing the match.

Return bouts with SS vs Tubes are perpetuated ONLY from what is being noticed by way of a desired loudspeaker’s demands for I/E from the amp. Either in reality, or in my head.

One example that keeps turning in my head is a user account of a particular speaker and how they decided that seemingly, watts alone made the speaker perform best.

This account said on pages right her that it worked well with 300wpc. Then better with 400, much better with 500 and then its very best with 600wpc!!

Along that way, nothing was said of the better build of each amp used in that trek. Merely an annotation of the power level, or available power itself was given the ‘spotlight’. I’ve found as have many here, when an amp retials for $60K vs an amp that retials for $6K, there is usually some disparity in the quality of the sound iself, not merely their possible power outputs.

Regardless, the note on power alone keeps revolving saying look to more power… and maybe quality too. But power first!

Its very disconcerting.

Throw in the fact many amps will indeed power what ever speaker, albeit to what ever degree of efficiency or optimization, and the apparent formulae for amp selection gets twisted and convoluted a bit more.

Wanna make the selection process still more difficult? Up the ante on the purchase prices. A lot. A whole lot. To the point where you’re actually playing with, or about to play with scared money.

For the uninitiated scared money is a gambling term. It means you should not be playing in that game if you’re using the mortgage, rent or child support funding, or simply can’t afford to lose the bet. Or such a cost puts you way out of your comfort zone. This is why ya need to know the players more than the cards most of the time and one of the ideas behind this thread.

Mapman said it and so has Atmas. Despite the actual values, specs, and ratings, synergy seems to claim numerous avenues which end up at its doorstep. Synergy, like beauty is in the ear of the listener.

I will whenever possible opt for the item whose quality I perceive is greater, if the electrical compatibility needs are even close. If I can swing it financially. Even if it hurts a little at first. Even for a while. When possible.

In the end, this is all about perception, which is indeed reality, then the sound, not the optimization is key. Argue it any way possible and it always comes out the same way.

I believe with all due considerations, a set of quality amps running a set of quality speakers will yield an ‘as’ commensurate presentation.

My hat is in the ring of best sounding amp, over that of the reputed ‘right’ electrically matched amp within reason, of course for one simply can not ignore outright, the factors amps and speaker marriages need for compatibility..

First 5 – 7%? I’ll presume this initial area pertains directly to the scenario you presented, otherwise, isn’t the first 10 – 20% of a class AB amp where one finds Class A functionality, and many adore that area of operation.

@blindjim  Well they do say its all about that 1st watt, but in the case of less efficient speakers it might be about the first 5 watts in the case of some behemoth amps.

(If you've ever heard the maxim that lower powered amps tend to sound better, this is one of the reasons why. IMO, there are some fairly musical low- and mid-powered solid state amps, but there aren't any that are really high powered. As for tube amps, there are very few high powered amps that sound like real music either!)

Class A is helpful for reducing distortion. Most AB solid state amps go from class A to AB within the first watt or so. But even class D amps which operate on a different principle (as well as many push-pull tube amps) have this quality of increased distortion at lower power levels. So even if they were all perfect voltage sources, you would still want to match the efficiency and power handling of the speaker against the low power distortion issues of the amp.

For this reason, I suspect our grandchildren will still be talking about equipment matching- we're not seeming to be solving this issue anytime soon.

I am curious about the peak/transient power approach to the topic. Apparently
peaks/transients can demand 5-7 times the power of continuous (RMS?) power demands. Hence if an amp is capable of  100 wpc continuous delivery it should muster 700 wpc for those short-time events. How is this realized in practice?
Which amplifiers are built to this spec and how?

I know about one solution, curious about other.
Hypex Ncore500 are rated 100 watt continuous with the thermal limit of 200 watt.
Peak power is 700 watt into 4 ohms.The peaks can be fairly long, measured in seconds, the limits are thermal.  Some Hypex UCD units go up to hundreds of watt continuous. Those have big radiators both on power supplies and amp modules.