[SET Man]

From a post of mine from Jul '07:

And for one last thing - Has anyone noticed an overall sence of being ill-at-ease whan listening to UcD amps? I can't put a finger on it, but I would find myself kinda clenching my jaw, even when listening to the tuner. Not in response to anything directly audible, but just that feeling of tenseness. This feeling is completely gone with the VAC.

Maybe similar to what you describe?
-Mike

Anyway, Russ have you heard other Class-D, T and etc amps beside the one you have now?  How do you feel about them?

I have had a 100 wpc Tripath and a Panasonic XR55 receiver in my system in the past.  Both drove me from the room screaming and really aggravated my ears.  I really like listening to the Hypex.  It's the after-effect that bothers me.  I've heard ICE, Spectron and Nuforce amps in other systems, but not long enough to know if they would bug me in the same way.

This is a curiosity issue for me, not a crisis issue.  I'm more than happy sticking with the tube amp and enjoying the music.  Going forward, I will note listening levels with the two amps to see if there's a significant difference.

Hey!

   Wow! I guess I'm not the only one

   I have SET amps in my system but I have no problem listening to regular SS amps, some actually sound excellent.

   If you ask me to explain why on this Class-D things I have to say I just can't. I tried to explain to some of my audiophile friends from NY Rave and I don't think I can really get to it.

   But when it come to this Class-D, T and similar I just can't seem to live them them 

  And I thought it was just me. 

Take care,
Buddy

[Russtafarian]

A few days have passed.  My ears have calmed down.  The tubes are glowing.  The music is flowing.  And all is well.

If I decide to make another run at comparing the Hypex amp and the tube amp, any ideas on how to more "scientifically" approach it?

Is anyone in the SoCal area interested in borrowing the battery Hypex amp to see if it has the same effect on them?  I'm not going to ship it, but if someone is interested in picking it up from me and listening to it for a week, let me know.

Russ

[jon_010101]

I'd try to verify your prior about levels being equal when listening to the two amps.  Like the above poster mentioned, the lower the distortion the quieter it subjectively sounds.  This can cause one to believe they are listening at lower levels then they really are.

I agree - This should definitely be confirmed.  I can listen 10dB louder with my Citation II than I can with my Bogen tube amp, and not even notice.  That's a tremendous difference, and enough to make my ears ring.

Some of our sensation of how loud something is comes from the production of distortion in our ears.  With an amp that has slightly increased low-order (2nd, 3rd, 4th) harmonic distortion, similar to that generated by one's ears, the apparent volume level will be louder.  With a lower-distortion amplifier, it may be tempting to turn it up to result in the same level of distortion - this time with your ears distorting more than the amplifier or speakers.  This is when it gets dangerous.

I see some have suggested bandwidth as a concern.... With switching amplifiers, the actual bandwidth is almost certainly *lower* than a typical solid state or tube amp - the output stage filters are designed to pass only audio signals.  There may be high frequency noise problems, however, but it should be beyond the range which is reproducible by your speakers.

[AmpDesigner333]

From a post of mine from Jul '07:

And for one last thing - Has anyone noticed an overall sence of being ill-at-ease whan listening to UcD amps? I can't put a finger on it, but I would find myself kinda clenching my jaw, even when listening to the tuner. Not in response to anything directly audible, but just that feeling of tenseness. This feeling is completely gone with the VAC.

Maybe similar to what you describe?
-Mike

Anyway, Russ have you heard other Class-D, T and etc amps beside the one you have now?  How do you feel about them?

I have had a 100 wpc Tripath and a Panasonic XR55 receiver in my system in the past.  Both drove me from the room screaming and really aggravated my ears.  I really like listening to the Hypex.  It's the after-effect that bothers me.  I've heard ICE, Spectron and Nuforce amps in other systems, but not long enough to know if they would bug me in the same way.

This is a curiosity issue for me, not a crisis issue.  I'm more than happy sticking with the tube amp and enjoying the music.  Going forward, I will note listening levels with the two amps to see if there's a significant difference.

Hey!

   Wow! I guess I'm not the only one

   I have SET amps in my system but I have no problem listening to regular SS amps, some actually sound excellent.

   If you ask me to explain why on this Class-D things I have to say I just can't. I tried to explain to some of my audiophile friends from NY Rave and I don't think I can really get to it.

   But when it come to this Class-D, T and similar I just can't seem to live them them 

  And I thought it was just me. 

Take care,
Buddy

Some of our customers have told us that they love the sound of our digital (technically "Class-D") amps, but they don't like the sound of other digital amps (from other companies).  It might be the output filter or feedback design.  People often criticize me for saying that feedback wrapped around the output filter of a Class-D amp can have a negative impact on the sound.  Actually, this could be your answer!

By the way, fake class designations like "Class-T" or "Class-Z" are actually Class-D.  The definition of "Class-D amplifier" is "an amplifier that uses its output devices as switches".  This is a per peeve of mine.

Thanks for hearing me out.

[Brian Cheney]

Why not publish some scope photos of the output waveforms of your amplifier?

This should include sine waves at 1W, 10W, and full rated output at 20Hz, 200Hz and 20 kHz, a 1 kHz square wave at 1W and at clipping, and any out of band artifacts.

You can include distortion and noise measurements if you like.

[stereocilia]

Consider also the phenomenon related to tinnitus called "residual inhibition,"  where some noise which masks tinnitus can continue to mask it even when the noise disappears.  If this is happening, then the tube amp might be giving you more sound which is the opposite of what other contributors assumed.

I also agree with jon_010101.  If signal A is exactly the same intensity as signal B, but signal A has distortion, then we almost universally judge signal A to be 'louder.'  I know, I'm begging the question of exactly how much distortion and of what type equals a perceived vs. real change of what amount, but still...it's basically true.

[stereocilia]

I just thought of another variable: compression.  If the tube amp is compressing more then I suspect it would sound smoother.  Compression effectively makes the quiet parts of music louder and the louder parts of music quieter.  So, your ears may get a more uniform signal which could generate a larger "residual inhibition" effect.  Just brainstorming.

[AmpDesigner333]

Why not publish some scope photos of the output waveforms of your amplifier?

This should include sine waves at 1W, 10W, and full rated output at 20Hz, 200Hz and 20 kHz, a 1 kHz square wave at 1W and at clipping, and any out of band artifacts.

You can include distortion and noise measurements if you like.

Sounds like a good idea.  Please do me a favor and post this request on my thread:
http://www.audiocircle.com/index.php?topic=58526.msg524196;topicseen#new

I'd like others that follow my thread to see it.  Also, there are specs for the DAC4800A and Cherry amps here:
http://www.digitalamp.com/DAC4800A%20standard%20measurements%20v3.pdf
http://www.digitalamp.com/cherry%20measurements%20v6.pdf

Do you have similar scope shots of another Class-D amp design?  It would be nice to compare.  We take great pride in our design and love to show it off.  Thanks for your kind thread.

[bummrush]

For me class d worked or sounded fine at first but after a few months,it was apparent something wasnt right,can i pin it down in audiophile jargon no.Sure the sound was clear,but it something hard to pin down,i suppose you could call it some type of uneasiness,who knows.But what was clear was that it totally interfered with the enjoyment of the music.

[jon_010101]

Do you have similar scope shots of another Class-D amp design?  It would be nice to compare.  We take great pride in our design and love to show it off.  Thanks for your kind thread.

You can find some in Stereophile test results for various products, and can refer to their reviews online.  The early ones measured appallingly bad!  Fuzzy crooked square waves and .1% THD+ in the form of ultrasonic noise at small signal levels.  Yours should look quite a bit better.  I'm interested to see a 10kHz 1W square wave, given that your website distortion and noise specs are quite good for a switcher

edit -- just checked Stereophile, and Sharp SM-SX100 and Bel Canto eVo 200.2 are early examples which (IMHO) measure a bit squirrely.  A typical McIntosh tube amp, for example, would beat the snot out of these in a comparison of measurements at reasonable power levels.  Not sure about the newer amps - I'd hope they should be better!

[JoshK]

[facilitator hat on]

AmpDesigner333, please tread lightly.  Your two posts are in the gray area, since you brought up your amps (commercial offering) when they were not mentioned in the thread prior.  This is generally against forum policy. I realize that you were offering your experience to help understand, which is why I deem it "gray area", but I don't want the lab turning into commercials for retail products.

[facilitator hat off]