GoodSoundClub - Romy the Cat's Audio Site - Class D

Audio Discussions
Topic: Class D - right on target

Page 1 of 1 (22 items)

Posted by Paul S on 01-25-2012

This question is posted as I ponder an audio future without ML2s. It looks like my speakers will be around 92/93 dB, with plenty of large motors to drive. Yes, it will be multi-channel (5); but still each channel needs more power. Since I am not a habitual shopper, I really have no idea what is out there. It has been almost 25 years since I owned SS amps. For the past 12 years or so I have used SETs.

What turns out to be a big issue is the back EMF (or something) from the large drivers. It seem like even when volume/loudness is not an issue, most amps either "over-tighten" or they "let go" when there's serious work to do.

I realize that context is important, but I have only heard the big class D amps in the "pro" installations, and I am not interested in this sort of sound for my "playback".

Please do not suggest the ML3s. I will not be spending that kind of money, at least not for a while. Also, I suppose I need yet more power.

Paul S

Posted by Romy the Cat on 01-25-2012

Surely with 92/93dB sensitivity you are out of SET loop and I have no idea what you were listening over your last 12 years. To drive 92/93dB you need at least 50-70W SET, unless you built your listening room in a large “Sub-zero” refrigerator.

Paul, if you go multi-channel then it is absolutely irrelevant what amps you buy, the multi-channel recordings/setups are so bad that it does not worth to be bothered with better amplification.

Rgs. The Cat

Posted by JJ Triode on 01-25-2012

Paul,
Rather than go SS, perhaps you should consider push-pull tube amps for each of your five 92-93 dB-efficient channels (I assume "channels" means frequency bands, not HT5.1 or similar.) Along with that, consider using a modest amount of global negative feedback ("modest" means maybe 6-9 dB for pentode or ultralinear operation, or 2-4 dB for triodes or triode-connected pentodes, not the more typical 12-25 dB.) Making the feedback adjustable (you can put a pot in the loop, and another at each input to give independent control of overall gain and damping) will give you a lot of control over the resulting Sound. Having multiple impedance taps for each amp will help too.

You could start by buying five "Dynaco" Stereo 70 or Stereo 120 kits from Bob Latino and build each one differently for the targeted channel. Later on if you need something different, you could rebuild any of them to his stock circuit (the front end is different from the original Dynakit btw) and sell them at little loss. Sure it is a lot of labor but there is no escape from that anyway. Or you could rebuild a bunch of different vintage amps for different bands. There are plenty of options in PP.

Cheers,JJ

Posted by Paul S on 01-25-2012

"Five Channels" in this case is still "normal" stereo, with a blended center channel and stereo subs; 5 channels. And each channel will have multiple large drivers. I actually know the original "Dr. Dynaco" guy; he bought my old Fulton speakers for re-building...

Basically, I dunno yet what it will take to make nice with several large drivers, but right now I'm guessing SS...

Best regards,
Paul S

Posted by decoud on 01-27-2012
fiogf49gjkf0d Paul, you might want to take a look at the parallel GM-70 amps here: http://www.sacthailand.com/ You can get 5 of them for the price of a used ML2, and, well, it is a high power SET.

Posted by Romy the Cat on 01-27-2012

An interesting amp, thanks, decoud.

http://www.sacthailand.com/AmpGlowMasterGM70.html

I never have seen or hear it but it might be interesting. Chinese makes nowadays a lot of pretentious high-end products and they are mostly horrible crap. Here is Thailand put itself in the map. It also might be a “horrible crap” but it very much might be a perfectly viable amplifier. It is all depend from what in the head of the guy who make them in Thailand and sine we have absolutely no idea who he is and what he is it is hard to say anything.
Let to see some circumstantial evidences that he can get. The amount of distortions he promises is believable. The response at 60W is very reasonable as well; even I would like to see it not at 60W but at full 70W rated power.

The input tube, the Russian 6N1P is garbage tube; very bad sounding and it certainly need to be replaced with something different. Thankfully there are plenty of similar tubes and it might be an hour-long job to fit the amp with some kind of better sounding tube with similar characteristics.
My main question in this amp would be the 6BL7 driver that pushed the output stage. The guys who make the amp are very diplomatically provided response at 60W but they did not stress it further. To me, the key to thinking about this power amp will be to see what this amp does at 75W, I want to see HOW it clips. Will it be the driver? The 6BL7 is 10W on plate, usually 8W, so it will be 16W driving a pair of GM-70. It is a bit not enough current. Since GM-70 is DHT and can easily run on the negative side of the curve then I would like the driver be able to handle the GM-70’s grid current if called upon it. I think that two plates of 6BL7 is a bit shallow buffer. After all the purpose of the amp like this to driver non-sensitive load and to throw power…. So, as clipping will take play on the amp I would like to see what kind clipping will it be and will be and the most important what element will clip first: drives, PS, transformer, etc….

Somebody need to make own business to scavenger Far East, to collect those amps and to bring them to US. During the last 20 years there were a number of reps who did very good living by importing European amps to US, I do not see why nowadays the right people do not do it with Asian products.

Tne Cat

Posted by Paul S on 01-28-2012

JJ, I would consider PP or anything else if I could hypnotize myself into believing it works.

Decoud, I agree that those GM70 amps are interesting, and they might be a reasonably inexpensive platform, if nothing else. Funny that the site is much less annoying than "domestic" sites... I consider this a +! Romy is right that there is still $$$ to be made by "screening and buffering" this stuff for the western markets.

I am trying to recall various listening "sessions" that I paid very little attention to at the time. For instance, a couple of years ago I was invited to join a local audio group for a session that turned out to be sponsored by a shop. Sure, all the people were/are nice, but who can take this sort of thing seriously? Anyway, this sort of thing is the only "listening out" I have done in years.

Again, one thing that sticks with me from the Lamms (and everything else, for that matter...) is the "back EMF" thing with the larger drivers, and/or X/Os. I keep trying to imagine an amp that could effectively "make the speaker part of its circuit", which means maintaining its sonic bearings with a reactive load. Yes, I know that amps that can do this sound like arc welders; or, they used to...

Paul S

Posted by decoud on 01-28-2012

I suppose the key question in this situation is this: if you are going to have a single amplifier is the advantage of any departure from a SET topology ever likely to compensate for its shortcomings? If the answer is by and large no, as it seems to me, then the list of SETs with the kind of power you need is relatively short, no?

For what it is worth, sacthailand have a UK distributor (http://acousticperfection.co.uk) so someone in the west has a connection with them, and they will customize to request (e.g. single rather than parallel, +/- feedback etc). What they will not do, though, is build a full range Melquiades...

Posted by tuga on 01-28-2012

Paul S wrote:
This question is posted as I ponder an audio future without ML2s. It looks like my speakers will be around 92/93 dB, with plenty of large motors to drive. Yes, it will be multi-channel (5); but still each channel needs more power. Since I am not a habitual shopper, I really have no idea what is out there. It has been almost 25 years since I owned SS amps. For the past 12 years or so I have used SETs.

What turns out to be a big issue is the back EMF (or something) from the large drivers. It seem like even when volume/loudness is not an issue, most amps either "over-tighten" or they "let go" when there's serious work to do.

I realize that context is important, but I have only heard the big class D amps in the "pro" installations, and I am not interested in this sort of sound for my "playback".

Please do not suggest the ML3s. I will not be spending that kind of money, at least not for a while. Also, I suppose I need yet more power.

Paul S

How about a pair of Tom Evans Linear Bs?
http://www.audiolimits.com/html/tom_evans.html
Ric

Posted by Paul S on 01-28-2012

Ric, I sheepishly admit that at this point I remain entranced with the idea of a Class A behemoth. Probably my suicidal tendencies at work... Think of the last big tower that Tesla was working on when he died; now match current to voltage...

Before I jump (or fry...), I hope to read some of the SS Bible ideas about differential power and power regulation, since most "high-end" amp companies tout these as plusses. Everyone seems to know about the "complimentary" clash of distortions that "cancel" each other out; everyone but me, that is... As for feedback, I guess it's really only a question of how they do it...

Tom Evans seem like a smart company, with well-spoken friends in the British audio press. I like that they do stuff in-house to suit their own needs. I "heard" an early Groove phono stage, under the usual conditions, but that's it for the marque.

One way or another this is shaping up to be another expensive lesson...

Best regards,
Paul S

Posted by Stitch on 01-29-2012
fiogf49gjkf0d :-) Lamm 1.2R

Posted by Paul S on 03-27-2012

No surprise, the biggest problem when shopping for "suitable" amps is getting a bead on the sound using systems featuring the truly BAD "high end" speakers and ancilliaries. Still, I actually found something that might be acceptable; but units are currently in pre-pay/order mode, 5 weeks out. GAAAH! Not to mention that these amps MAY sound like crap immediately when their "limits" are exceeded, and I don't know yet where those limits are, in my own room. Chicken/Egg/Chicken/Egg... Obviously, I have to get the amps in my own room - for a while - but how to do it...

As for the big, powerful amps I actually want to find, nothing promising so far. So far, anything with "power and control" sounds just like that, a sort of "wet blanket" effect that I just HATE! I also hate the "creamy", "velvety", or "wet" sound! The sad truth is, basically, I like SETs operating in their comfort zone, including the bass! In fact, the "funniest" thing so far is that the best bass I have heard came from triode PP amps, and this was almost as good as the bass from the ML2s (as far as it goes...)... To tell the truth, the little 2A3s have wonderful bass (as far as it goes...). Too bad the penalty for SS bass "extension" is so high!

I can't emphasize enough how much I HATE the audiophile speakers!!! I can pretty much say, the bigger and more expensive they are, the WORSE they sound! And when I think of the "name" "reviewers" using these speakers to make proclamations about amps and other audiophile gear, it is sooo obvious how ridiculous this whole "system" is!

Some time ago I wrote that if your speakers don't work with ML2s, then change your speakers! And there is still part of me that thinks I blew it selling the ML2s... Very certainly, nothing I have heard so far gets as much right in terms of what matters most to me in Sound.

Paul S

Posted by JJ Triode on 03-27-2012

Paul, you wrote:

the best bass I have heard came from triode PP amps

Which PP triode amps, using which output tubes?

the little 2A3s have wonderful bass (as far as it goes...)

Which 2A3s? The Wright 3.5s, other single-ended, or PP?

I am mostly using PP again after about 5 years with the Wrights, but only EL84 and related types in a little amp I bought 2 years ago and extensively tweaked. I am now thinking I need another 3-6 dB more power myself (at least if I want to play Mahler...). But I have WAY less sensitive speakers than you.

Posted by Paul S on 03-28-2012

JJ, I not only loved the bass from the ML2 (SETs) but I loved the bass from the little Wright WPA 3.5 SETs! In fact, I loved everything about those amps, as long as they were "comfortable". Too bad that wasn't FR, etc. with my speakers...

in my own situation, WAY less sensitive speakers would call for WAY more power, especially if large drivers are included in the mix. Like I said, it may be that the PP triode amps I want to hear more of were breaking up on tutti, the noise heard from ~ 5" "mid-range" drivers in ridiculous audiophile speakers of unkown "efficiency". And these amps are far too expensive to just take a flyer...

FWIW, for context/comparison, when I first listened to my own ML2s there was NO DOUBT in my mind that I had made a good decision, despite they had not been used for >5 years...

As for the bass from the recently-heard PP triodes, I mean it is the best bass I've heard in this era of shopping (as opposed to "ever"...), and compared to the SS and other tube PP "bass" heard during this time.

As I "recall", Wright (RIP) also made PP 2A3s...

Shoot me a PM for small talk...

Best regards,
Paul S

Posted by Paul S on 04-15-2012

OK, I have one foot back in the water again, a hand-me-down monoblock from a "well-respected movie sound producer", to whom I am connected through dear friends. Like most "sound professionals", he is fairly dismissive of the way "we" hi-fi nerds go about sound reproduction, and I have to confess that his $200k system actually confuses me. FWIW, his present "hobby" is recording large swing bands live and mixing them down - at home. Not a promising lead, on the face of it. Still, I think I may have something.

Let me begin by saying - emphatically - that I am NOT "recommending" anything at this time. I have not worked with this amp enough yet that the sound I am getting from my speakers is the sound I am after. That said (and I hope it is well understood), this candidate for my main, center channel is the Marantz MA-9S2.

With my present speakers, this amp has no trouble unravelling any "mix". It's all there, warts and all. In this respect, it is much "better" than the ML2s -with my present speakers. Bass is MUCH stronger, and it is better sorted out, as well; but it still does not have the LF "gestalt" of the best SET bass. Go figure, but pitch and timbre are excellent, as good (in a little different way) as the ML2s. Along with "sorting out the mix", this amp also lets me clearly listen to thermal noise and drift from the tubes in my hybrid phono stage. Otherwise, this amp is DEAD silent. Oh, yeah... it easily and cleanly drives both DEBZs, at once...

Now begins the real work, to train the amp and my growing pile of drivers to make Music together in my listening room.

Paul S

Posted by Paul S on 05-12-2012

No mistaking it, today I got The Sound using the MA-9S2. LF gestalt is here, too; it's just a matter of warming up the amp and getting the speaker(s) dialed in. This means I am good to go, to use this amp for a reference, and to make the most of it.

As for "methodology": Yes, I did do some "research" in order to come up with a list of candidates to "audition". Nonentheless, I am amused (and pleased) that a class A/B SS amp with boatloads of "feedback" can do what this one does (for me). Now, flush with this success, I have half a mind to try class D amps for side channels!

Paul S

Posted by Paul S on 05-19-2012

Or: Buy a new hammer and - for a while, anyway - everywhere you look, there's something that calls for a hammer.

The electricity today was shite (thanks, Smart Grid!), but I none the less enjoyed some of the music I played. While playing Brahms' PC2, the meter on the Marantz went 1/2 way repeatedly, on tutti and on the more-closely-mic'd piano at ffff. "Speaker" was my current "stack", about 94-95 dB "efficient", and it was loud-ish, but not especially loud. "1/2 way" on the meter equates to ~300W into 4 Ohms. The current stack is 2X 12" driver, 1X 15" driver, and a 4" tweeter, all direct radiators, plus 6 dB "networks".

An ML2 had no trouble getting the same stack just as loud.

Hmmm...

Paul S

Posted by Paul S on 05-25-2012

The recent TT measurement post reminded me that I tried Class D amps last weekend (with Wilson speakers). These amps are supposed to be the Class D for serious listeners, with PWM and Class D "switching" output stage, and large, conventional PS.

The amps showed power and control, and no "distortion" as we generally recognize it. Problems were "subtractive", smoothing everything into sound effects; perfect for audiophile extravaganzas.

I've heard class D amps that added terrible noise to ruined music. These amps just ruined the music cleanly and quietly.

Paul S

Posted by KLegind on 05-25-2012
fiogf49gjkf0d Hi Paul, I used to say that these class D amps presented music wrapped in a thin sheet of plastic film, but your description is more adequate. Ruined cleanly and quietly indeed. Kris

Posted by Paul S on 05-26-2012

OK, back to the meter on the Marantz: It actually reads +/- "exponentially", so "1/2 way" is more like 6 Watts, with the little spikes above "1/2" making it to 30 Watts. Not 300 Watts. This dispels the "mystery" of the ML2 playing the same stack at the same apparent SPL levels, albeit (of course) the ML2 is at the end of its rope at this point, while the Marantz is quite comfortable (as one would expect).

Paul S

Posted by Paul S on 06-28-2012
fiogf49gjkf0d The MA-9S2 center channel turned out to be good enough that I have gone whole hog and bought another (new) pair. I think Marantz (Japan) has discontinued the amp (at least for US distribution), and I did not want to let them slip away. I will write more in a specific thread once the new amps are broken in and I have a feeling for the sound via the DEBZs, in stereo. Paul S

Posted by Paul S on 09-01-2012

Since I "forgot" to mention it before, the very interesting amp I mentioned up the thread is the Nat Audio Generator monoblock, a Serbian PP triode/SS hybrid of some sort. Now that I have the MA-9S2s, there is no reason for me to check back on the Nat specs, but the sound - even through "high-end, audiophile" speakers - was pretty damned good, up to the the amp's "limits", whatever they may be. In other words, repeating myself, I think the amps may not "transition" well, whether into hyper-drive or clipping, I don't know. I think they are rated at 140W, and they seem to punch above their weight, which probably encourages the Morons to abuse them, like they did/do with the ML2s.

Anyway, I mention these amps not for the Morons to consume, rather I put them out there to be assessed on their merits by those who can hear for themselves and make rational decisions.

Paul S

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