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Old 19th October 2003, 12:35 PM   #11
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Are we to conclude then, that monster heatsinks are bad for sound then because they stop the amp from warming up very much???? I dare everyone to sidestep THAT question.
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Old 19th October 2003, 01:19 PM   #12
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Quote:
Originally posted by Circlotron
Are we to conclude then, that monster heatsinks are bad for sound then because they stop the amp from warming up very much???? I dare everyone to sidestep THAT question.
Real men don't use heatsinks.


Another interesting conclusion might then be that amps should
sound better in warm climates than in cold ones. Perhaps I
should consider moving south?
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Old 19th October 2003, 01:44 PM   #13
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Go towards the equator..come over to Singapore...VERY close to the hottest part of the Earth...
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Old 19th October 2003, 02:02 PM   #14
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The term 'warm up' when applied to an amp has nothing to do with equating high temperature to better sound.

Allowing an amp to warm up is just letting it reach thermal and electrical stability.

Critical operating conditions like bias and DC offset are/should always be adjusted when the amp is fully warmed up and for a big class-a amp this could take several hours. When the amp is cold, bias current could be a long way from its correct warmed-up value hence the amp may not sound so good.
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Old 19th October 2003, 02:26 PM   #15
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Ok...assuming the amp has an "suto" adjust for it's bias...what happens??
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Old 19th October 2003, 02:59 PM   #16
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I would say that the majority of power amps still use the traditional transistor and voltage divider approach to set the bias.

But even if bias is not an issue there may be matched differential pairs of transistors at the input stage that will warm up at different rates due to differences in power dissipation leading to higher distortion until they settle at similar temperatures and characteristics.

Things change a lot when an amplifier is warming-up, transistors are very sensitive to even quite small changes in temperature and it seems reasonable to expect that an amplifier may sound better once its operating points have stopped moving.

Or maybe it's just my ears that need time to warm-up
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Old 19th October 2003, 04:48 PM   #17
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Since transistors have a thermal coefficient it would be surprising if there was NEVER any change in sound for ANY amp when operating temperature changes. However, it does not follow that this is true for EVERY amp since there are a number of thermal tracking schemes in use to try to control this.

Thus, the initial question posted is slightly flawed in that it sought generalized advice regarding solid state amps in general rather than specific models or at least specific design topologies. I've not made a study of this. Has anyone? But I would expect that some benefit considerably from warm up while other exhibit little if any audible change. Most likely it depends on thermal efficiency (I would expect class A to be more suseptible - but who know?) and on the the success and accuracy of the thermal tracking technique used in specific layout.
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Old 19th October 2003, 04:58 PM   #18
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It's a fact. As I point out in the adjacent thread, devices such
as Mosfets reach higher transconductance figures at higher
temperatures, so it's not just a matter of getting the bias to
stabilize. Also, the higher the bias for Mosfets, the more
temperature stable, so there's your big heat sinks...
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Old 19th October 2003, 11:46 PM   #19
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Hi Nelson,
how long is the warm-up time then, for bjt's or mosfets? i guess we average users never noticed this as solid state amps can operate almost instantaneously....thanks and more power...

Hi sam9,
your comments makes a lot of sense to me, can you elaborate some more? ...thanks
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Old 19th October 2003, 11:54 PM   #20
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Default is there such an amp?

Hi RichardC,
you said, "Things change a lot when an amplifier is warming-up, transistors are very sensitive to even quite small changes in temperature and it seems reasonable to expect that an amplifier may sound better once its operating points have stopped moving."

i was wondering if there is such an amp....
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