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Old 23rd June 2004, 07:48 PM   #1
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Default Massive Parallel Operating

If amplifier fidelity---the ability of an amplifying device to faithfully amplify an input signal---depends on linearity in every respect of the device's operating parameters, and if any given single device (here, tube) has what might be called a non-linear finger-print---ie, departs from linearity differently than any other given single device---would paralleling not reduce, by the law of averages, any non-linearities peculiar to a given individual device? And wouldn't these "finger-print" non-linearities be greater reduced the larger number of devices operated in parallel?

Conrad-Johnson uses massive parallel operation in their ART preamplifier to seemingly excellent effect. Perhaps part of the OTL magic is explained by this massive paralleling effect?

Here's an idea (forgive my tendencies to SE design): massively parallel small-signal tubes on the output to achieve what is effectively a massive-PSE?

Ideas anyone?
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Old 23rd June 2004, 08:03 PM   #2
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Default Oh ....

.... and *if* massive paralleling creates desireable sonic effects, why not triple or quadruple things up, or more, in a PSU regulator circuit?
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Old 23rd June 2004, 08:49 PM   #3
EC8010 is offline EC8010  United Kingdom
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But you're assuming that the valve was designed to be perfectly linear in the first place. Otherwise, you will simply get a better approximation to the (not necessarily perfect) theoretical design.
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Old 23rd June 2004, 08:59 PM   #4
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Quote:
massive paralleling creates desireable sonic effects

I wouldn't call it that at all. A single tube always sounds better to my ears than two in parallel. If paralleling has a sonic signature it is one of blurring and obscuring details.

If commercial amps indeed use parallel tubes it is usually for a particular purpose like higher output power/lower output impedance/ noise but seldom because of better perceived sound.
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Old 23rd June 2004, 09:09 PM   #5
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Quote:
Originally posted by EC8010
But you're assuming that the valve was designed to be perfectly linear in the first place. Otherwise, you will simply get a better approximation to the (not necessarily perfect) theoretical design.
Hmmm, let's say I was assuming the valve was designed to be as close to perfectly linear as possibly could be, which is to say I was assuming no valve can be or is perfectly linear, which is to say the target point for the best linearity achievable is some value less than perfect.

But there's less than perfect and there's less than perfect. If Tube 1 departs from linearity in a way Tube 2 does not and Tube 2 departs from linearity in a way Tube 1 does not---we can fairly assume this happens---and if certain of those operating differences between Tubes 1 and 2 are themselves variable---variable or non-linear non-linearities---paralleling Tubes 1 and 2 will linearise the overall operation of a parallel-tube-stage closer to the operationally achievable ideal.
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Old 23rd June 2004, 09:11 PM   #6
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I agree with the logic of your argument - it's just that not many valves were specifically designed to be linear. Linear costs money, you see.
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Old 23rd June 2004, 09:27 PM   #7
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Default > 2 Tubes

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Originally posted by analog_sa
A single tube always sounds better to my ears than two in parallel. If paralleling has a sonic signature it is one of blurring and obscuring details.
I've heard opposing opinions on the sonic effect of paralleling two tubes. Some like the effect, some don't. One view of this difference of opinion---difference in value judgment?---is that those who like two-tube paralleling feel more is gained by paralleling than lost, while those who don't like it feel more is lost than gained. But what *is* gained, if anything? And how might one maximise benefit vs detriment in this regard?

My question thus goes beyond paralleling-a-deux to ask whether paralleling three, four, five ... ten tubes---a menage a dix!---might hold ground to single-tube operation. OTL amplifiers running multiple tubes on the output are anything but blurry and obscuring, so I don't think parallel operating per se is the culprit. Two-tube paralleling might be an exception.
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Old 23rd June 2004, 09:50 PM   #8
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If you operate multiple tubes of the same type in parallel ... what have you gained in linearity? All tubes will display the same nonlinearity.
That is why we use inverse feedback in our designs.
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Old 23rd June 2004, 10:34 PM   #9
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Quote:
Originally posted by Frank Berry
If you operate multiple tubes of the same type in parallel ... what have you gained in linearity? All tubes will display the same nonlinearity.
Precisely. Variable non-linearities of individual tubes will be averaged (ie, linearised).
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Old 23rd June 2004, 10:46 PM   #10
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Quote:
Originally posted by serengetiplains


Precisely. Variable non-linearities of individual tubes will be averaged (ie, linearised).

Averaging only works if the errors are random. This is not the case here where the tubes are nonlinear in a similar way.

You will average the small differences in nonlinearity but this will most likely lead to higher order distortions instead. You can't get rid of the fundamental nonlinearity.
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