Bob Cordell Interview: BJT vs. MOSFET - Page 105 - diyAudio
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Old 18th April 2007, 08:30 PM   #1041
PMA is offline PMA  Europe
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Quote:
Originally posted by Nelson Pass


You can make any amp look bad if you clip it into 4 ohms.
The amplifier is rated 400W/4ohm. Spectrum shown at 268W/4ohm.
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Old 18th April 2007, 08:41 PM   #1042
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Quote:
Originally posted by Nelson Pass
Use Class A, someday you will.
Hi Nelson,

I don't think Bob will risk losing one of his ears

Cheers,
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Old 18th April 2007, 08:55 PM   #1043
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Hi Es,
If JC is not listening or does not want to repeat himself, I seem to recall he said 9pair.
That 10W of ClassA in an optimised ClassAB output stage implies Iq~=800mA. About 90mA per device. Re=0r27 would achieve this with Vre=24mV. If one wanted to use Vre=19.5mV then Re=0r22 would get close.
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Old 18th April 2007, 09:06 PM   #1044
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Quote:
Originally posted by SY
Wow, that's interesting and kinky- I'd love to see a 10W spectrum, and intermods at the same level.
The bumps you see are the OS leaving Class A around 30W into
4 ohms and 15 watts into 2 ohms.

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Old 18th April 2007, 09:14 PM   #1045
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Quote:
Originally posted by PMA
The amplifier is rated 400W/4ohm. Spectrum shown at 268W/4ohm.
Indeed the amplifier delivers that at 1%, but you are still
portraying Hansen's fine amplifier in an unflattering light in
order to make a point.

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Old 18th April 2007, 10:31 PM   #1046
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Actually, I use about 150 ma per device.
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Old 18th April 2007, 11:00 PM   #1047
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For completeness, I use a .15 ohm emitter resistor in the JC-1. However, I first used a .1 ohm resistor in the prototype, but it became thermally unstable, so I moved it up. Actually, about .13 ohms would be about right.
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Old 19th April 2007, 12:26 AM   #1048
GK is offline GK  Australia
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Quote:
Originally posted by SY


Well, we're even, you did the same for mine. Unless, of course, you were serious and think that a low static THD at one frequency into a test load is a sufficient criterion.


Huh? When on earth did I say that? Firstly, I specifically cited 20Hz through to 20kHz THD as a general criterion to generalise on.


Quote:
Load tolerance, stability, source impedance, IM, bandwidth, noise, overload recovery, clipping characteristics, none of that (or anything else) seems to be taken into account.
I specifically mentioned the importance of other distortion mechanisms such as TIM, IMD, etc, but simply pointed out the fact that all these distortion mechanisms are related to a degree and that 20Hz-20kHz THD is a rather good figure of merit.
As for bandwidth, if an amplifier has very low THD-20, then the bandwidth is clearly sufficient.
And of course things such as overload recovery and clipping characteristics are important. That is which I deliberately said a well designed SS amp.

What do you expect a single post from me to summarise my views to be? A 50 thousand-word essay concisely covering every important detail of SS amplifier design?

Cheers,
Glen
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Old 19th April 2007, 12:40 AM   #1049
SY is offline SY  United States
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Please reread my question. For your convenience, I'll restate it:

Quote:
Could you outline what you'd consider a sufficient test regime to remove the amp as an audible defect in the electronics chain?
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Old 19th April 2007, 12:41 AM   #1050
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Quote:
Originally posted by mikeks
Just use good tone controls, and forget all this "sonics" nonsense.
Innaresting... I can't tell if this is satire or smugness. Doesn't add anything to the discussion.

Must be an inside joke, that would make it OK.
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