Power amplifiers that excel with very low impedance - and low efficiency loads

Enough off-topic arguing about who said what when. I look forward to a new thread when Ralph unveils the new amplifier.
 
a.wayne said:
Ralph,

I have been on the brakes very hard with you over this , you are the one doing the personal attacks , I’m only responding to your attacking rants ..

We have had many audio discussions over the years , most recently at the fla audio show in 2020, in your room, as well as numerous other times over the years in many different forums. In forums its your usual strawman arguments basically to support your limited power high impedance only driving amplfiers of choice, now I'm not going to use my time to search the WWW to prove any and everything about your class D amp rant , i don't care , But to say never Outside your company until recently is a joke Ralph, I’m guessing to protect your patent, well for the record no details were ever disclosed , you only mentioned in discussion you were looking into a class D design, it was some years ago ..

Here are a few mentions by others Of (going back a few years, first pic 2018 easily found) your no discussion until recently class D amps,

is 2018 recently Ralph ..?

We have had these and many discussions over the decades Ralph, so if not 7 or 8 on your class D ,maybe 5 ? it was some years back, again you mentioned you were looking into it and that it looked very promising,
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2018 is not '8 years ago'; by my reckoning that's more like 3. Please see your prior statement; this is what I mean by hyperbole yet somehow you were docking me for memory failure. 2018 is about right for when I started talking more openly about class D.

Are you saying you know of a comment where I've attacked you personally as opposed to a comment you've made? I'd like to see it. Being a moderator elsewhere, I'm very aware of the difference.

Regarding feedback: Feedback does its job by feeding some of the output signal back to the input of the amplifier, out of phase with the input signal. In this way it acts as a correction voltage to compensate for the non-linearities of the amp. But because it is out of phase with the input, bifurcation of the input signal can and does occur. This results in the generation of higher ordered harmonic distortion. This is well-known and I'm sure you know that; I've included this for others that might be following along.

If the amp has phase margin issues, if it lacks enough gain bandwidth product or any other limitation meaning there is insufficient feedback, the result (whether the amp is tube, solid state or class D) will be higher ordered harmonics that are not masked- and so will cause the amp to sound brighter and harsher than the actual signal (meaning that its not neutral). Since the ear assigns tonality to all forms of distortion and because the ear uses the higher ordered harmonics to sense sound pressure, I've felt for a long time that feedback is probably not a good idea unless you can add enough so that the amp can clean up the mess. Most amps made in the last 70 years suffer brightness and harshness on this account. Put another way, brightness is a coloration and because its caused by distortion you can't fix it with a tone control or putting a sock on your tweeters.

If you get over about 35dB of feedback, you can get around this problem. But in order for the amp to sound musical, the distortion signature (what I saw you describing as the amplifier's 'sonic signature' on a different thread on this site) remains important. On this thread this seems to be the bone of contention between yourself and me.

So none of what you've heard me say in the past is about feedback inconsistent with my position now (because you didn't get all of my thoughts on the matter); I'm simply taking advantage of the fact that class D offers a means of applying large amounts of feedback, enough that it can clean up most of the mess that it makes; something difficult to do with other topologies. On top of that, I can get the amp to have nearly the same distortion signature as our OTLs with considerably less overall THD (this is because the non-linearities in class D are mostly caused by deadtime issues and non-linearities in the encoding scheme, both of which can result on lower ordered harmonics). In comparisons we've done, its hard to tell the midrange and highs apart between our OTLs and the class D amps. There are several takeaways from this; first is that it's very nice to find that we were on the right track as a method of obtaining neutrality with our OTLs since they sound nearly identical. The second is the apparently if you have the right distortion signature ('sonic signature'), the amount of distortion becomes less important. This is because the lower harmonics of that signature can mask the higher orders, causing the amp to sound smooth.

But what you want is not just smoother, but also more detailed. You get the latter by reducing the overall distortion, hopefully without messing up the distortion signature.

As far as I'm concerned the graphs and like as we've seen here have been consistent with my position on all this. I do rely on my own experience as a designer and manufacturer of 46 years which may or may not carry weight with others than myself. But the press has made many comments about the sound of our amps over the years and while that too is anecdotal, at some point you have to admit that its very hard to be truly objective when it comes to audio. I don't know anyone that is. So I invite you, if you feel I'm incorrect in my comments, perhaps you could get out there and show us all how its done. Go ahead and build an amplifier designed by you from the ground up and see how well you do and perhaps see if I'm really telling it like it is.

@Dizzie
I look forward to a new thread when Ralph unveils the new amplifier.
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On most sites the latter would be a violation of site rules. Its not when something comes up in the context of a thread, for example if someone asks about an amp we make or something like that.
 
atmasphere said:
@Dizzie


On most sites the latter would be a violation of site rules. Its not when something comes up in the context of a thread, for example if someone asks about an amp we make or something like that.
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I am sure someone will ask.:thumbsup:
 
Hey Ralph,

One thing I would like to know is what Class D amplifier module are you planning on using?

B&O (ICE Power), Ncore, Purifi, or are you designing your own module from scratch? I know EJ from Wyred 4 Sound has designed his own from scratch but has yet to release it in a production product. He did actually use it at a show a few years ago and it seemed to go over well. As far as I know he is still using ICE modules in his production amplifiers.
 
Randy Myers said:
Hey Ralph,

One thing I would like to know is what Class D amplifier module are you planning on using?

B&O (ICE Power), Ncore, Purifi, or are you designing your own module from scratch? I know EJ from Wyred 4 Sound has designed his own from scratch but has yet to release it in a production product. He did actually use it at a show a few years ago and it seemed to go over well. As far as I know he is still using ICE modules in his production amplifiers.
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We're using a module of our own design.
 
Randy

EJ has his own W4S branded GAN amplifier that's to be released any day now. The other two models of the amp that he was a part of developing have already been released by Walter under his LSA brand and Peachtree. You might want to see if you can get a listen either at the shop or at home.
 
Thank you Jack. I have not been in touch with EJ through these crazy times.

I am surprised that he did not release it under his W4S brand... but then again he has been doing a lot of OEM work for a bit of time now. Probably more money for him :dunno:.
 
Randy

I got the impression that it was a three company joint effort and Walter started it almost two years ago. He got to release first and then Peachtree a couple of weeks later. EJ may be waiting to release his and finally the Aura preamp at the same time. The prices on the three amps are all the same with the other two offering to take trade-ins. I suspect Walter's with go to The Music Room. I thought about ordering one from Walter just for fun as I don't need it but will wait for now to see what EJ's version looks like. You can see the guts of the first two on Walter's website as they are supposed to look the same. Not sure if EJ will do anything extra on his release but he could. And the OEM idea is probably correct on the other two in terms of the guts as casework is different.
 
Of course Walter is not a designer. I have spoken with him when I was helping EJ out. A nice enough guy and it was funny listening to EJ and him going back and forth :). EJ has been designing and building much of the Peachtree line for sometime now. I would not doubt that Walter was involved in the design discussions for an amplifier to go along with his LSA line that he had purchased.

EJ has been working on his own line of speakers (he showed one model at the LA show) and has been building a huge amount of this one brand of subwoofers that I believe are used mainly in custom applications (I have never seen them for sale at any of the usual sites, but I know he built a ton of them for the distributor). I also spoke with him at the LA show and he is not at all happy with the Carver line. He thought the name would have a bigger draw, but what really bothers him is trying to service older pieces. There are no schematics and he said he has been forced to reverse engineer pretty much every piece that comes in. There also seems to be a consistent hum in some of the pieces. He feels the integrated he designed is probably the best piece.

I wish he would release the Aura pre. I feel the the STP-SE is getting a little long in the tooth, so to speak. I tried the Aura a couple years back and really liked the design. It sounded excellent, but I know EJ was a little surprised that I felt the Stage 2 was just a smidgen better. I gave him my hand written notes that I made when comparing the two, about 20 pages of notes. He thought the standard Aura would sound better, and it was indeed close. If he does offer a parts upgraded version (such as the stage 2 concept) all I can say is holy cow....
 
Randy Myers said:
Of course Walter is not a designer. I have spoken with him when I was helping EJ out. A nice enough guy and it was funny listening to EJ and him going back and forth :). EJ has been designing and building much of the Peachtree line for sometime now. I would not doubt that Walter was involved in the design discussions for an amplifier to go along with his LSA line that he had purchased.

EJ has been working on his own line of speakers (he showed one model at the LA show) and has been building a huge amount of this one brand of subwoofers that I believe are used mainly in custom applications (I have never seen them for sale at any of the usual sites, but I know he built a ton of them for the distributor). I also spoke with him at the LA show and he is not at all happy with the Carver line. He thought the name would have a bigger draw, but what really bothers him is trying to service older pieces. There are no schematics and he said he has been forced to reverse engineer pretty much every piece that comes in. There also seems to be a consistent hum in some of the pieces. He feels the integrated he designed is probably the best piece.

I wish he would release the Aura pre. I feel the the STP-SE is getting a little long in the tooth, so to speak. I tried the Aura a couple years back and really liked the design. It sounded excellent, but I know EJ was a little surprised that I felt the Stage 2 was just a smidgen better. I gave him my hand written notes that I made when comparing the two, about 20 pages of notes. He thought the standard Aura would sound better, and it was indeed close. If he does offer a parts upgraded version (such as the stage 2 concept) all I can say is holy cow....
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Who is EJ?
 
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