A good article about the human ear and tubes (1 Viewer)

[Lee Scoggins]

Chu yes I would be interested in statistical analysis of cap audibility claims. You can send that in PM if you dont want to here.

I understand that Hovland Company has done some blind tests here that do indicate caps are audible.

 

[Lee Scoggins]

How does an engineer go about designing in "soul"?

An audiophile (like myself) would answer the question as follows:

Design the most neutral and accurate sounding gear as possible and play transparent recordings.

Some nefarious designer might design in a "hump" in the midrange so the sound is more forward-I don't like this approach which is why I have focused on Audio Research amps for a neutral sound.

 

[Chu Gai]

Pearson must be deaf by now

 

[Lee Scoggins]

Chu,

Have you done a double blind test to see if he is deaf?

Maybe objectivists think he is deaf due to perceptual biases...

 

[Chu Gai]

How old is he?

Grab a beer and some wings Lee...this round's on you for a change!

 

[Michael R Price]

Pass Labs sounds good? I agree, except for their pricing. I can't wait for Nelson to finish his Zen Variations series, so I can apply Supersymmetry to my Zen V4.

So Lee, you think that any really accurate amp sounds good, and tubes are just generally more accurate (maybe not in the ways we usually think of) than most solid state?

(Hmm... too bad I am not legal drinking age yet. )

 

[Chu Gai]

Well we can drop you off here Michael

 

[Michael R Price]

I haven't been there in about... darn, only 8 years or so!

 

[Pete Saunders]

My reply on the tubes versus SS debate:who cares!!!

I'll go for whatever brings me closest to the enjoyment of music. Tell me what piece of high-end audio gear transmits pre-recorded sound 100% perfectly. None that I know of.

The best high-end designers do their fine tuning by ear and most listen to live music quite often. Just ask Vicktor Khomenko of BAT.

Now, I'm not negating accuracy or transparency, but some distortion ( odd order harmonics of tubes) may sound more pleasing and thus more musical to some ears.

Regards

 

[Yogi]

Now, I'm not negating accuracy or transparency, but some distortion ( odd order harmonics of tubes) may sound more pleasing and thus more musical to some ears.

You mean even ordered distortion of tubes? Odd ordered is in SS gear and can be quite fatiguing.

 

[Michael R Price]

Speaking of different distortion types... I can't get my stereo to sound the same two days in a row! My current experiment is playing with the bias current in my SS amps (4-pair Mosfet follower outputstage)... there appears to be a noticeable difference in sound. When the bias is too low (incidentally I feel like the designer's recommended amount is too low) there's a little "dry" distortion and the sound seems brighter and more powerful but a little fatiguing. When it's way higher than normal the sound becomes a little dull and more "calm" or effortless sounding. In between a window of maybe 280ma to 350ma, it's like trying to pick out the best lenses at the eye doctor: after each adjustment it sounds a little different, but I can't remember well enough to tell if it is better or worse. This is really interesting because I had assumed the distortion is reduced to a very low "inaudible" level by feedback (spec: THD=0.005%). And the output stage bias current is only a small aspect of the amplifier design. (Nelson Pass, I think, just makes his amplifiers single-ended and pushes the bias as high as the hardware can handle.)

I know many tube amps have adjustable bias, do you know if there are similar effects to be found with those?

 

[Pete Saunders]

Yogi, I stand corrected. I was just feeling really odd tonight!

Regards

 

[Chu Gai]

I don't know about the distortion of BAT's tube amp, but it's got a not insubstantial output impedance suggesting it'll interact with a speaker's impedance curve giving you a non linear frequency response into a real load. As far as the listening to real music and designing accordingly, just what the heck does that mean other than it sounds like nice advertising copy?

And really, if the distortion is at inaudible levels, who cares what it is?

Well Michael, if you overbias your tubes you'll shorten their life among other things.

 

[RichardHOS]

You mean even ordered distortion of tubes? Odd ordered is in SS gear and can be quite fatiguing.

That's not a valid generalization. Even order distortion isn't attributable to tubes, but rather to the designs often used with tubes (single ended). Tubes can produce just as much odd-order distortion as SS, and SS the same even order distortion of tubes, simply by using the relevant circuit topology.

 

[Brett DiMichele]

Well Michael, if you overbias your tubes you'll shorten their life among other things

Ain't that the truth.. Overbias them enough and thier life
will be quite short, trust me I speak from experiance!

 

[Lee Scoggins]

So Lee, you think that any really accurate amp sounds good, and tubes are just generally more accurate

I believe that the better tube amps are more accurate than solid state, particularly in the midrange. With things like soundstaging and tonality of instruments, I think they are very accurate. Some of the Pass Labs amps and the Halcro amps are also accurate, but this idea that tubes are less accurate or that they put in too much second order harmonics is a myth or dated thinking. Tube designers have learned how to create neutral sound since the late 90s.

I got into tubes purely because I heard them accurately recreate some recordings I worked on in the 90s. We would have early test pressings of acoustic musicians that we would sometimes get in the middle of sessions. I could take these home or go to Sound By Singer (before I bought the ARC amp) and listen. I just felt the tubes sounded best at capturing what I heard in the studio that day.

The key is finding something that you like and that sounds good on all the music you listen to-the good recordings anyway.

 

[Yogi]

The key is finding something that you like and that sounds good on all the music you listen to-the good recordings anyway.

Well I like my new CJ gear as it makes every recording pleasant without any listener fatigue and without sounding inaccurate. It has a fairly low impedance of 0.4 ohm (damping factor of 20@8ohms) across the whole bandwidth and tests don't show it interacting it with Quad ESLs, Monitor audio, Wilson and Splendor speakers so saying that a modern well built tube amp interacts with the load is dated thinking at best. It has all the attributes of my B&K ref amp plus a healthy dose of sweetness and air. I would hate to have a top notch SS amp in my system which only sounds good with a handful of reference recodrings and call it Hi-Fi. Nada...thats not me.

 

[RichardHOS]

Then why continue to attribute a certain behavior to either tubes or MOSFETs, when it is solely a behavior of the amp topology?

 

[Yogi]

Then why continue to attribute a certain behavior to either tubes or MOSFETs, when it is solely a behavior of the amp topology?

And where did I say that tube or SS sound is 'solely' a behaviour of amp topology? The sound that comes out of any amp is due to a combination of the device's properties and the design topology. One without the other has no meaning. Look at the big picture Richard dont get bogged down by individual elements of the picture.

 

[Michael R Price]

Brett, If you overbias a Mosfet you can shorten its life to a few seconds, as I once found out! (I think I've destroyed about $40 worth of those. :frowning

And Yogi... I think some SS amps (both of mine are good at this to a different extent) can be a lot of fun even with some pretty terrible recordings. You hear all the distortion in the recording clearly, but it's not all bad distortion! (And I think I am able to shift the distortion spectrum around a bit, by playing with the biasing.)

http://www.dself.dsl.pipex.com/ampins/dipa/dipa.htm#5 (Section 3 especially. There are graphs of the distortion waveform for BJT amps with too little, the "right" amount, and too much bias [the scale is expanded on that one]. I wonder what the distortion waveform of a Pass amp looks like...)