This audio cable business is getting out of hand...

[HammerSandwich]

Now here’s a guy I’d like to see participate in this forum.

Nelson's quite active at DIYAudio, where there's a dedicated Pass Labs section.

 

[NTomokawa]

Nelson

Nelson Pass also states that measurements do not fully describe how an amplifier sounds.

 

[xr100]

Nelson Pass also states that measurements do not fully describe how an amplifier sounds.

Taken at face value, where non-linear behaviour is audible, that could be considered to be correct--"qualia problem" etc.

 

[xr100]

Maxim MAX98307/8 ICs -- "fully differential mono Class DG multilevel power amplifiers with integrated inverting charge pumps offer highly efficient, high-power audio solutions for portable applications."

 

[anmpr1]

Taken at face value, where non-linear behaviour is audible, that could be considered to be correct--"qualia problem" etc.

When Nelson can demonstrate that he can tell the difference between his super duper class A amp and a Pioneer receiver once the brands are hidden and the levels are matched and they are not overdriven, then I'd be happy to take his objections seriously. If he can't, and he can't, then I'm inclined to believe that he's just saying that because he knows that what's selling his amps is his 'special magic', and not anything reality based.

For a laugh (or a cry) here's a link to a Pass amp test by one of his erstwhile dealers:

https://www.audiosciencereview.com/forum/index.php?threads/catalogue-of-blind-tests.8675/post-217462

 

[Not Insane]

FWIW, I am pretty sure Class G was (initially) mostly a Hitachi thing, and Class H was Soundcraftsmen's.
Not sayin' there might not have been Class H Hitachi hardware... but I am skeptical

HitachiSR2004 by Mark Hardy, on Flickr




View attachment 45305
source: https://www.americanradiohistory.com/Archive-Audio/80s/Audio-1986-Equipment-Directory.pdf (multipage ad section)

Thank you! I actually have that very soundcraftsman amp (the one in the middle). I just temporarily retired it because it picked up a REALLY bad hum.

On a side note, A friend of mine still has that Hitachi receiver. I'm guessing this may be why I was confusing the two designations (G vs H).

 

[xr100]

When Nelson can demonstrate that he can tell the difference between his super duper class A amp and a Pioneer receiver once the brands are hidden and the levels are matched and they are not overdriven, then I'd be happy to take his objections seriously. (snip...)
For a laugh (or a cry) here's a link to a Pass amp test by one of his erstwhile dealers:

https://www.audiosciencereview.com/forum/index.php?threads/catalogue-of-blind-tests.8675/post-217462

To be clear, my reply wasn't actually about Mr. Pass (but rather the word "describe")...

Interesting test. The Yamaha A-S700 used measures well, whilst I have no idea about the Pass Labs Aleph 1.2 that it was compared to.

At the end of the day, the goal is to figure out what products to acquire based on given resources, requirements and constraints. Unless one is very wealthy, $12000 for 2 channels of power amplification for domestic use is patently an extremely poor allocation of resources.

On the other hand, given the choice between a Yamaha A-S30x/50x/70x/801 and a random (?) Pioneer receiver, I'd sooner use one of the Yamahas--even if it meant some added cost, as available measurements imply a high level of transparency and so it would substantially fall out of concern as a system performance "bottleneck."

I think that makes my general view of the "high end" audio industry pretty obvious!

 

[anmpr1]

On the other hand, given the choice between a Yamaha A-S30x/50x/70x/801 and a random (?) Pioneer receiver

If it was free (LOL) I'd pretty much rather have almost any high end amplifier over a generic Pioneer receiver, even if I can't tell a sonic difference. Unless it is one of the mid to late '70s SX monsters refurbished, in which case I'd take the Pioneer over almost anything else.

 

[xr100]

If it was free (LOL) I'd pretty much rather have almost any high end amplifier over a generic Pioneer receiver, even if I can't tell a sonic difference. Unless it is one of the mid to late '70s SX monsters refurbished, in which case I'd take the Pioneer over almost anything else.

Hmm, but if there is no audible difference, doesn't that relegate your amplifier(s) to "ornamental" status?

There are quite a few examples of badly engineered "high-end" amplifiers that I would sooner not use over a "generic Pioneer receiver."

Ethan Winer's converter test is interesting.

(Acoustic recording with A/D conversion simultaneously through "a Lavry Blue converter and an M-Audio Delta 66 sound card," and DAW mixed (level/balance only.) Three files are available, one for the Lavry, another the M-Audio, and the third with the stereo mix D/A converted by the M-Audio and A/D converted back by a SoundBlaster X-Fi card. Filenames are mixa.wav, mixb.wave, and mixc.wav--the idea being to download, listen and guess which is which... and then E-mail Ethan Winer to find out.)

When I downloaded the files a while back, and performed a somewhat casual comparison, one of the files sounded worse, and so I chose that as being the one that must have gone through additional D/A and A/D conversion.

I wasn't quite sure if I could tell the difference between the remaining two.

I didn't bother E-mailing Ethan Winer, because on loading the files in iZotope RX and looking at the spectrograms, one file has an obviously worse noise floor than the other two, and that was indeed the one that I guessed had been through the additional stages of D/A and A/D conversion.

Two of the files also have spurious tones above 10kHz...

Of what relevance is this to amplifiers? Well, at least one could say that the A/D sections of SoundBlasters for which measurements have been posted on this site don't measure very well at all--and the same is true of certain power amplifiers...

 

[xr100]

Stereophile measurements of the Pass Labs XA2008 monoblock power amplifiers. ($42000 for two.)

Needless to say, these do not show "blameless" levels of performance.

 

[anmpr1]

Hmm, but if there is no audible difference, doesn't that relegate your amplifier(s) to "ornamental" status?

Yes. But what an ornament it is!

 

[Julf]

Yes. But what an ornament it is!

"If you like that kind of things, that is the kind of thing you would like"

 

[thefsb]

Yes. But what an ornament it is!

View attachment 45452

I miss the old times when a good stereo included a disembodied hand.

 

[anmpr1]

"If you like that kind of things, that is the kind of thing you would like"

My current amp/preamp-DAC will fit in a large shoebox, could be carried together with one hand, has much less distortion and about as much power (more into 4 ohms), and will translate digits. But it doesn't look as cool, nor does it have a radio or integral phono input. It's all a trade-off, I guess.

 

[xr100]

Yes. But what an ornament it is!

I tend to prefer a "minimalist" clean look but they certainly don't make 'em like that anymore! Really like that old-school "wordy" advert copy...

Obvious question is whether having one of those "on show" means that you have a "lo-fi" or "hi-fi lifestyle"?

 

[Julf]

My current amp/preamp-DAC will fit in a large shoebox, could be carried together with one hand, has much less distortion and about as much power (more into 4 ohms), and will translate digits. But it doesn't look as cool, nor does it have a radio or integral phono input. It's all a trade-off, I guess.

My amps are hidden in the speaker bases, the DAC/DSP in a cabinet...

 

[Rene]

No, it is a good thought, and in fact in practice is a requirement, but it is a necessary but not sufficient condition. You would use that "foreknowledge" to control switching but at the output need something that carefully coordinates and controls the transition to prevent adding undesired signals at the output. Feedback can help, and feedforward (more likely for something like this), but it's tricky.

A normal output stage haas decent power-supply rejection plus feedback to make it great, so when you change the power rails it does not get through to the output signal. For class D, changing the rails directly hits the output of the amp, so isolation is a major issue.

Remember that in class D the output switching waveform is removed by a lowpass filter - switch rails while switching duty cycle and you are done.
Keep in mind that the applications for even higher efficiency power amps (>90%) are cell phones and other battery powered equipment where fidelity is not the major concern.

 

[DonH56]

Remember that in class D the output switching waveform is removed by a lowpass filter - switch rails while switching duty cycle and you are done.
Keep in mind that the applications for even higher efficiency power amps (>90%) are cell phones and other battery powered equipment where fidelity is not the major concern.

Have you built one? Curious, not a challenge, I'd like to know if it has been done successfully. When I tried it the charge storage of the output devices and output filter led to low-frequency (in my case remembering it was an RF design) amplitude modulation of the output. It would have been a problem in a wideband system but not a big deal in my application. The few articles I have seen (not something I track) all switched on an edge (which can be tricky itself) but still had amplitude modulation of the output. Many (RF again) were for FM or PM systems so amplitude modulation was not a big deal. For audio it seems challenging.

Since it is not something I am doing or tracking now I would not be surprised to hear it has been achieved. The few cell phone amps I have seen (friend in the area) are "normal" class D amps, not switching the rails.

 

[jhaider]

My Tag finally broke last year. 22 years of service. I’ll try to get it fixed but hopefully at reasonable cost. If it’s more to fix than an Apple Watch, then I’ll go for the Apple Watch. So yes, I get it! An automatic would probably still be running.

I had my quartz S/el serviced by the company last summer. Including sandblasting and a new crystal it was about $350.

That is objectively not worth it, but I've had the watch since high school (about as old as yours) so it has sentimental value.

 

[Rene]

Have you built one? Curious, not a challenge, I'd like to know if it has been done successfully. When I tried it the charge storage of the output devices and output filter led to low-frequency (in my case remembering it was an RF design) amplitude modulation of the output. It would have been a problem in a wideband system but not a big deal in my application. The few articles I have seen (not something I track) all switched on an edge (which can be tricky itself) but still had amplitude modulation of the output. Many (RF again) were for FM or PM systems so amplitude modulation was not a big deal. For audio it seems challenging.

Since it is not something I am doing or tracking now I would not be surprised to hear it has been achieved. The few cell phone amps I have seen (friend in the area) are "normal" class D amps, not switching the rails.

I have not built a class DG amp. What I have come across is this one from Maxim: https://www.maximintegrated.com/en/products/analog/audio/MAX98307.html
They use charge pump generated tracking supply rails, so the rail voltage changes are slow relative to switching frequency.