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Old 25th January 2013, 06:30 PM   #31
bcarso is offline bcarso  United States
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Second harmonic distortion is the same note as the fundamental, but one octave higher, so it's always an enhancement. It sounds really good. One of the ways to produce this is with an asymetric distortion mechanism, such as a minimalist tube circuit or a non-biased polarized electrolytic in the signal path. The tradeoff is Intermodulation Distortion, which is rarely desirable. In a guitar amp where you want distortion it can be argued that this is desirable. In a hi-fi amp where there will be many sounds mixing (heterodyning), there is a very fine line between enough and way too much. I've done the research. 1dB of symetry offset should be the max limit in hi-fi land. I would never choose to generate 2nd with an electrolytic... Pfffff!!! (Behringer has a non-biased polarized electrolytic in the input signal path of some of their DSP units, which is why I redesigned and rebuilt all their analog circuitry in my DEQ2496 - see my website).
I find that a lot of aficionados of second listen to rather sparse textures as their music of choice. One famous speaker designer has a system of which he's very proud, and I finally said enough of the right things, and had an occasion that provided an excuse, to be allowed to audition his stuff.

And it sounded fine, with unlimited SPL (horns and tube amps, big old Levinson amps driving multiple woofers). A whole wall of CDs. So I looked for something familiar, having not thought to bring any source material myself. Surely I'd find something.

Almost nothing was familiar, all was female vocals. I finally dug up a pops orchestral sampler so I heard some symphonic material, and then as well Bela Fleck's Flight of the Cosmic Hippo, which I wanted to hear for how the system handled the lowest frequency material on the title track.

The system sounded fine, if just the tiniest bit abrasive in the lower treble to my ears (was it second?). But I'd conjecture that the individual probably is somewhat dismissive about 2nd, as are some other audiophile friends.
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Old 25th January 2013, 06:39 PM   #32
TheGimp is offline TheGimp  United States
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Originally Posted by Bob Richards View Post
My experience with Tantalums is that they are low reliability. If they ever get reverse voltaged, you can just about count on failure.
They are also subject to ESD damage, and over voltage spikes. Either can set them up for failures later on.
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Old 25th January 2013, 06:41 PM   #33
bcarso is offline bcarso  United States
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They are also subject to ESD damage, and over voltage spikes. Either can set them up for failures later on.
And to add to the excitement, some parts are labelled with a stripe on the positive terminal, in contrast to standard Al electrolytics with the stripe on the negative!
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Old 25th January 2013, 06:47 PM   #34
SY is offline SY  United States
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Originally Posted by bcarso View Post
One famous speaker designer has a system of which he's very proud, and I finally said enough of the right things, and had an occasion that provided an excuse, to be allowed to audition his stuff.
Hmmm. GT or DD, I'll bet.
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Old 25th January 2013, 06:53 PM   #35
bcarso is offline bcarso  United States
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Hmmm. GT or DD, I'll bet.
You win, numero uno.
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Old 25th January 2013, 08:18 PM   #36
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Originally Posted by bcarso View Post
I find that a lot of aficionados of second listen to rather sparse textures as their music of choice. One famous speaker designer has a system of which he's very proud, and I finally said enough of the right things, and had an occasion that provided an excuse, to be allowed to audition his stuff.

And it sounded fine, with unlimited SPL (horns and tube amps, big old Levinson amps driving multiple woofers). A whole wall of CDs. So I looked for something familiar, having not thought to bring any source material myself. Surely I'd find something.

Almost nothing was familiar, all was female vocals.
[....]
Hey, Aphex made a very nice business selling second harmonic distortion enhancers for vocal sweetening.

Whether post-processing was the Right Thing to do instead of correcting studio practices deadening the sound to the point where it needed it, well, that's another discussion.
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Old 25th January 2013, 09:29 PM   #37
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Hey, Aphex made a very nice business selling second harmonic distortion enhancers for vocal sweetening.

Whether post-processing was the Right Thing to do instead of correcting studio practices deadening the sound to the point where it needed it, well, that's another discussion.
When you have only one signal (vocal for ex.), that's the one situation where it could be argued that generation of even order distortion (especially 2nd harmonic), with it's inevitable accompanying I.M. distortion may be desirable. A tiny amount (1dB) of asymmetry will give you the even harmonics, but I.M. will go up fast if you add too much. With multiple signals, the I.M. will get ugly very fast. Choral music and piano are perhaps the best test for when I.M. is too high. You'll hear the difference beat frequency that gets generated (usually a few HZ, almost like a tremolo effect).
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Old 26th January 2013, 03:32 AM   #38
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When you have only one signal (vocal for ex.), that's the one situation where it could be argued that generation of even order distortion (especially 2nd harmonic), with it's inevitable accompanying I.M. distortion may be desirable. A tiny amount (1dB) of asymmetry will give you the even harmonics, but I.M. will go up fast if you add too much. With multiple signals, the I.M. will get ugly very fast. Choral music and piano are perhaps the best test for when I.M. is too high. You'll hear the difference beat frequency that gets generated (usually a few HZ, almost like a tremolo effect).
Aphex highpasssed the signal before the distortion unit, then highpassed the result before mixing it back into the full bandwidth original. The effect was mostly used on voices, as I recall, so IM audibility was kept fairly low by this technique.
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Old 26th January 2013, 04:52 AM   #39
gopib is offline gopib  India
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Default Amazing

Just happened to read this thread. Really amazing to know. I guess "audiophiles" are soft targets for this sort of thing...
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Old 26th January 2013, 05:32 AM   #40
morinix is offline morinix  United States
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Default A bit more.

I was the first tech Hovland hired to ease the load on Bob. Not one failed unit ever came in while I was there so every tech function was dedicated to new unit QC. Bob was finishing the design on a solid state amplifier called Radia and he was doing the QC on the Sapphire power amp. Also they had a plan to let Bob retire. I think he did about a year after I was there.

Hovland's assembly operation was all hand done. If you Google map the company address and scroll over to the side of the building now you will see two painted over windows at sidewalk level. When Hovland was there you could see through those windows. If you happened by you would see the assemblers all toiling away with magnifying visors on. Most would think that jewelery or watch repair was going on, but no. This was about half a dozen Hispanic gents building amplifiers the Hovland way. Of course this all done under the watchful eye of the Lead Assembler Lady and Mike.

There was no formal inventory control going on here; Just the Lead Assembler Lady checking plastic bins of parts. "Oops! this bin is getting low. Hey Mike order more of these!" Mike would respond "Ok, I will add those in the next order". They watched the parts and what the assemblers were doing with them like hawks.

One part they had constant trouble with was the stacked switch deck that made the volume control. The Lead Assembler Lady was very proud of herself as she whipped out dental tools to pull and prod the little contact points and springs on the deck.

The polished front panel was another source of pride for them. Their cost on that was $200.

Bob Hovland has a heart of gold. The nicest guy you will ever meet. Very unassuming and has a gentlemanly charm reminiscent of Edwardian times. He is a true product of the golden age of stereo. He is all analog and a very old school designer.

Mike Garges is a very opinionated, fastidious and egocentric fellow. Once I said "S#!t happens" he retorts "No, no! Excrement occurs" in a sarcastic, pragmatic tone. I think he attached himself to Bob during the time the MusiCap was being developed. Seems like he took more than his fair share of pride in his ability to to do tidy wire bunching and the like. Once he deduced his dowsing skills he self anointed a deity status that the others around him acquiesced to. He was really into indie music and once called the Loyola Marymount radio station KXLU and lambasted them for watering down their format. I can't help but wonder what became of him after the shuttering of Hovland.
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Last edited by morinix; 26th January 2013 at 05:51 AM.
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