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Old 9th January 2013, 08:37 AM   #32381
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Originally Posted by fas42 View Post
Ythe fact you ditched the RCAs, added ferrites, tells me you can hear these distortion artifacts.
Just precautions for better contacts and locked plugs. I do not like false connections
Ferrite, to reduce RFI/EMI returns in the feedback loops.
About vibration, well, i can believe that you could have some jitter effects with Quartz and noise some poor ceramic caps... what the level ?
An audiophile legend coming from the old age of tubes ?
Of course, some care has to be taken for transports and turntables...
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Old 9th January 2013, 08:42 AM   #32382
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Originally Posted by SY View Post
Got anything new since 1957?
Better modern resistances than those poor carbon ones used in the fifteens ?
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Originally Posted by MrRogers View Post
Are you a comedian or an audiophile, Esperado?
Why ? I asked, on an 'technical' point of view, what advantages to use aircraft machined aluminum for a preamp chassis that can justify the price increase. Got no answer.
God, save-me from being an audiophile or an hypochondriac :-)
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Old 9th January 2013, 09:06 AM   #32383
SY is offline SY  United States
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Originally Posted by Esperado View Post
Better modern resistances than those poor carbon ones used in the fifteens ?
Well, I was pointing out the obvious. Not only has this been well known since the '50s (read the article I linked), I can't think of any amp made in decades that uses carbon comps of that type in the feedback network. Looking inside the SS amps I have in house (Adcom, Crown, Bryston, Sunfire, some generic Chinese unit), it's film resistors. Ed is apparently flogging a horse that died when Eisenhower was president.

Scott's observation was accurate- modern amps (outside of some ultra-expensive fashion statements) that are designed by conventional engineering use inexpensive resistors and show vanishingly low distortion.
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Old 9th January 2013, 09:37 AM   #32384
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Originally Posted by SY View Post
Scott's observation was accurate- modern amps (outside of some ultra-expensive fashion statements) that are designed by conventional engineering use inexpensive resistors and show vanishingly low distortion.
I follow-you, SY. As i prefer CFAs, with low Z feedback resistances, (more current in them) i always found accurate to oversize the feedback resistance's power handling. Just another *none esoteric* good practice. A little overkill, as, in ordinary listening sessions, the average level is pretty low :-)
May-be it would be useful to list in a dedicated thread all technical good practices we can think about. Star grounding, interconnection arrangements, PSU noise filtering, Jitter correction, sens of the AC plugs (best position for low current leakage), prevention from EMI/RFI ( care of the feedback returns where a little serial resistance in output can change a lot) etc...
And help people to get rid of all the 'audiophile magic' snake oil around...
All those things we learned with time and experience.
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Old 9th January 2013, 09:44 AM   #32385
Bonsai is offline Bonsai  Taiwan
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George

I read those as saying the same thing! Pass the Ouzo. The civilized way to settle a non-dispute.

ES
I would have said pass th Uzzi

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Old 9th January 2013, 10:11 AM   #32386
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Originally Posted by simon7000 View Post
Scott

There is a 3dB increase in thermal distortion for each halving of frequency so that is 9

. N
Where was someone using 1/4 W CC resistors in the feedback of a chip amp? BTW Allen Bradley NOS ones measured much better than that. Walt and I published this stuff in 1982, we also did that app. this is old news.

EDIT - I guess Walt and I only updated that article from 1957.
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Old 9th January 2013, 10:47 AM   #32387
gpapag is offline gpapag  Greece
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Originally Posted by Esperado View Post
Why ? I asked, on an 'technical' point of view, what advantages to use aircraft machined aluminum for a preamp chassis that can justify the price increase. Got no answer.
Christophe
Amateurs in general and Comedians especially , don’t understand what materials are needed to build an audiophile product.

George
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Old 9th January 2013, 11:02 AM   #32388
gpapag is offline gpapag  Greece
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Originally Posted by scott wurcer View Post
Where was someone using 1/4 W CC resistors in the feedback of a chip amp?
Scott, you missed the photos of the gaincard’s internals.

I have asked again in the past but got no answer. What would be a good safety factor (multiplier) for the power rating of a feedback resistor?

Quote:
Walt and I published this stuff in 1982, we also did that app. this is old news.
Which one? AN-348 ?

George
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Old 9th January 2013, 11:26 AM   #32389
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Originally Posted by gpapag View Post
Scott, you missed the photos of the gaincard’s internals.

I have asked again in the past but got no answer. What would be a good safety factor (multiplier) for the power rating of a feedback resistor?



Which one? AN-348 ?

George
Actually it was stuff that didn't get in there, I'm not sure it's on the web now. Yes I missed the photos, hardly the chipamp's problem in any case.

EDIT - Wait a second, the 47 Lab's gaincard is only 25W. Another point a thermal distortion (if it existed) is by definition low order and vanishes at the origin so even .1% (-60dB) has virtually no chance of being audible. Besides the point that it shows up in the simplest THD measurements (no "as yet undiscovered" test required).
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Last edited by scott wurcer; 9th January 2013 at 11:34 AM.
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Old 9th January 2013, 11:31 AM   #32390
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Originally Posted by gpapag View Post
Amateurs in general and Comedians especially , don’t understand what materials are needed to build an audiophile product.
We are here to learn, George.
Gold, Silver, Diamonds (specially in buffers), anything aircraft or spatial, Teflon and Kevlar, carbon fibers.
Of course, the add of some species of rare wood and cotton fibers help to get a more natural sound.
All that need to be 'voiced' by audio gurus.
How can-we recognize a *real* audio guru ? They all talk with a very deep, convincing and quiet voice "Your eyes are heavy, your eyelids close..." usually after a little hypnotic music:
Wilson Audio Design Goals - YouTube
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Last edited by Esperado; 9th January 2013 at 11:38 AM.
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