Exotic Amplifier Technologies

The VCE of the output stage is constantly changing, anyway. Bipolar transistors have high collector impedances which mean that they tend to reject the effects of changes in VCE.

The possibility of changes in VCE due to rail switching affecting the performance of the amplifier *is* the "feedtrhough" that Graham was mentioning.

Hmm, didn't you just say that one such amp used rail switching to achieve

400 wpc?

You're being deceptive again Trevor, by not admitting that with the rail-switching active in high-power mode, the amps output was considerably greater.

The modern Crown amps I've tested have had breathtakingly good performance. Sound great, too.

Is that the Crown K series or Macro Tech, Arny?

We have a K2, and also two old but incredibly reliable DC300A.

They seem to be highly regarded

Iain

Neither.

There's been a lot of good Crown amps since the DC300A.

**Yep. I would assume the situation is the same here. IME, Crown have built some very good amplifiers (Macro Tech) and some absolute shockers (DC300A).

--
Trevor Wilson
www.rageaudio.com.au

Thanks for this comprehensive reply, Trevor. I love all this background stuff. I'm not at all sure you answered the apparent inconsistency I pointed out in your original post (how a company can lose "significant sales to competitive products" when people are buying their product as before); indeed I think you supported the opposite viewpoint, that a company can ride on the back of its former glory for a long time thanks to people not bothering to listen before purchase. It's also interesting that you modified "sounded like crap" to "extremely average sound quality". Given the vagaries of component matching, I can well imagine very average sound quality passing muster with most non-enthusiasts, whereas "crap" one would expect to be discovered as such relatively quickly. I do still feel that you have a tendency to hyperbole that undermines your credibility and sometimes causes friction; given the extent of your experience and knowledge I'd rather you curbed that and gave us the less extreme version of your opinions in the future (just a thought). I still don't buy it that NAD went downhill during the 90s due to some obscure design flaw in their products ("PE"). They did probably lose some ground with the relatively uninspiring 302/304--312/314 amp line, but then quickly made up for that with the 320/340 line, on up to the current 320BEE.

Not sure I understand your anecdote of the NAD2200. "Customer turns amplifier up to the point of clipping (400 Watts)." Why would anyone in their right mind do that? And why would anyone who did, not deserve whatever they got? "The listener, whose ears are suffering from continuous high level audio, cannot hear the massive clipping and the tweeters are destroyed." Indeed, along with the listener's and most of the neighbours ears as well, I'd imagine. I don't see that NAD can be in any way to blame for idiotic users--I certainly wouldn't have fixed their speakers under warranty. I would have given them a good dressing-down, but after all that they probably wouldn't have heard me.

**My pleasure.

I love all this

**Not really. There is a time lag between when people finally work out that a company has gone 'off the rails' (and most do).

It's also interesting that you modified "sounded like crap"

**Mea culpa. I am guilty of hyperbole every now and again.

Given the vagaries of component

**Good point. I guess what I was attempting to get it is that NAD was building genuine 'budget high end' products, before the introduction of their Power Envelope stuff.

I do still feel that you have a

**Er, yes and no. I am perfectly consistent with my comments. I don't see that damaging credibility at all. If I were to start selling (say) SET amps, then THAT would damage my credibility.

given the extent of your experience and knowledge I'd

**Fair point. I may just consider that as a reasonable idea.

I still don't buy it that NAD

**And yet, they've ceased building PE technology into their products. If it was such a brilliant idea, they'd keep doing it. **Not all listeners are sane.

And why would anyone who did, not deserve

**We al listen at different levels. Many times I've had to leave the room during a demo, because the music was too loud for my tastes.

"The listener, whose ears are suffering from

**You missed the point. KEF 104.2 tweeters almost never failed during warranty. The only time they did, was when connected to a NAD 220 amplifier. The problem is that gross clipping can occur without warning, with the 2200. Regular amps provide warning of distress, before gross clipping occurs.

--
Trevor Wilson
www.rageaudio.com.au

I can think of several reasons why not. All technology moves on. They may simply have found a better way of achieving the same end, or decided such minor power boosting was superfluous. The question is, if PE amps sounded so bad and NAD discovered this, why did they not discover it during the design stages? Also, why has no one but you ever suggested PE amps sound bad? And why do they continue to enjoy such a fine reputation with vintage gear enthusiasts who are usually very knowing about these things (check Ebay prices). And why did the PE amp I had sound so good (pretty much on a par with the much later, and much celebrated, Rotel 931 Mk11. I was able to directly compare them over several weeks).

You should know that there's a secret prize for answering these questions satisfactorily. :-)

**Not necessarily. GOOD technology remains.

They

**NAD do not achieve the same end, using different technology. They are now using the same technology they were using prior to the introduction of PE topology. And further: The "Minor power boosting" was hardly minor. The NAD 2200 amplifier was capable of FOUR TIMES the power on transients.

The question is, if

**Not necessarily. NAD just lost it's way. They forgot their roots.

Also, why has no one but you

**I'm not the only one. The people who chose products like Rotel instead of NAD voted with their wallets.

And why do they continue to enjoy

**See previous discussion about PERCEIVED quality. Also see my previous comments about the large amount of transient power, vs. Dollars and packaging size.

And why did the

**What speakers did you use?

**After you tell me what speakers you used, I should be able to answer your question.

--
Trevor Wilson
www.rageaudio.com.au

Oh Trevor, you are forgetful. Why would I listen to speakers when I can listen through my trusty Sennheiser HD 595s?

And yes, I know you're now going to say, "Oh well, all bets are off as amps aren't made to drive headphones." Whatever, I'm convinced headphones are the great leveller as they remove the power factor and the inevitable reactive load. I've been listening to amps through headphones now for 30 years and getting similar results to what others report using speakers. The only complication is when an amp uses a separate HP amp, but almost none of them do save the odd NAD pre-amp.

**Precisely! I already knew the answer to my question. **Nope. Amps ARE made to drive headphones. The trouble is there are a wide variety of schemes to accomplish this. They do so, with varying degrees of quality. In some cases, the output stage (for speakers) has absolutely nothing to do with the headphone circuits.

Whatever, I'm convinced

**Your assumption is faulty. You don't mention which NAD amp you owned, so I can't tell you how the headphone outputs are configured. I can, however, tell you that the Rotel RA931-II uses a series resistor of 330 Ohms for the headphones. If the NAD uses a lower value resistor, or, even better, a dedicated headphone amplifier, the difference in sound quality could be substantial. Moreover, your logic is flawed. Although headphones, generally, will expose minute differences in source and amplification more readily than most loudspeakers, their impedance curve is more benign than most speakers. As such, they will place relatively minor demands on amplifiers. Additionally, I presume you are comparing similarly priced amplifiers?

I've been listening to amps through

**Not so. Many decent quality amps use a headphone amp. Which is EXACTLY the kind of amp you should be using. In your situation, a power amp stage is wasted. You would be better off using a dedicated headphone amplifier, or a preamp which has adequate drive for headphones.

--
Trevor Wilson
www.rageaudio.com.au

"Trevor Wilson" wrote> And yes, I know you're now going to say, "Oh well, all bets are off as

**Nope. Amps ARE made to drive headphones. The trouble is there are a wide variety of schemes to accomplish this. They do so, with varying degrees of quality. In some cases, the output stage (for speakers) has absolutely nothing to do with the headphone circuits.

Whatever, I'm convinced

**Your assumption is faulty. You don't mention which NAD amp you owned, so I can't tell you how the headphone outputs are configured. I can, however, tell you that the Rotel RA931-II uses a series resistor of 330 Ohms for the headphones. If the NAD uses a lower value resistor, or, even better, a dedicated headphone amplifier, the difference in sound quality could be substantial. Moreover, your logic is flawed. Although headphones, generally, will expose minute differences in source and amplification more readily than most loudspeakers, their impedance curve is more benign than most speakers. As such, they will place relatively minor demands on amplifiers. Additionally, I presume you are comparing similarly priced amplifiers?

I've been listening to amps through

**Not so. Many decent quality amps use a headphone amp. Which is EXACTLY the kind of amp you should be using. In your situation, a power amp stage is wasted. You would be better off using a dedicated headphone amplifier, or a preamp which has adequate drive for headphones.

--
Trevor Wilson
www.rageaudio.com.au


***** Please dont cross post and take your audiophoolery away from 
aus.electronics.

Brian Goldsmith.

**Take your complaint up with the original poster. Further, if you would care to elucidate what the f*ck "audiophoolery" (WRT this particular part of the thread) is, I'd be happy to discuss whatever you want in more technical detail, if you wish. Not one word I wrote is incorrect, WRT headphones and amplifiers.

--
Trevor Wilson
www.rageaudio.com.au

Sneaky, Trevor. We'll have to watch you.

In very few cases, certainly where budget products are concerned. Inevitably it's much easier--and quite satisfactory--to run the headphone socket from the output via a resistor. Where there's a separate HP amp involved, as in say NAD's 160 pre-amp, the manufacturer usually crows about it.

NAD 7225PE receiver.

I know. I changed it to a higher value as it didn't allow enough movement of the volume control. I detected no change in sound quality afterwards.

Which relates to what I said about a non-reactive load. Thus taking the vagaries of speaker load out of the equation.

Exactly; that's the point I'm making. Where the same amp will react differently to different speakers...well, you get what I mean.

Yep. All >$500.

Disagree. I've listened to several HP amps. I have one now. None of them sound half as good as my Marantz PM8200. Yes, I know there's a lot of power wastage and I regret that, but ultimately it's the sound that matters. Whatever may apply in theory, if one's ears tell a different story.....

Because your speakers were actually worth a darn?

**Not so sneaky, really.

**True.

**True.

Where there's a

**Nope, but sometimes they do.

**I have no service manual for that model.

**Uh huh.

**Except that speakers are precisely what most users want from their amplifiers. **I did not say that ALL headphone amplifiers are equal, nor are they necessarily superior to the amplifier in your Marantz.

--
Trevor Wilson
www.rageaudio.com.au

Brian Goldsmith.

**You're not getting much smarter, are you?

IF you have a problem with crossposting (or top posting, or whatever you imagine is a problem), then take it up with the original poster.

--
Trevor Wilson
www.rageaudio.com.au

"Trevor Wilson" wrote >

You're not getting much smarter, are you?

IF you have a problem with crossposting (or top posting, or whatever you imagine is a problem), then take it up with the original poster.

**** As far as I'm concerned,YOU are the original poster!

Brian Goldsmith.