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  #11  
Old 25th March 2018, 11:05 PM
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Greg. Greg. is offline
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Default Re: Disappointing Audiolab

But if you alter the operating temperature of mosfets, my understanding is you interfer with their optimum operating point. I thought designs incorporating mosfets include the consideration of operating temperature to establish the values of corresponding components to allow them to work optimally. Sorry, this is probably a bit simplistic, even inaccurate, but I would have thought the addition of external after cooling of a mosfet design would require an understanding on how much hotter than designed the unit was trying to operate at and then a regulation of external fans for cooling to bring them back into their intended operating range. Of course, as I am pretty much an ignoramous on this, what I have written may be absolute rubbish. I’d be interested in any thoughts from someone who knows.

Last edited by Greg.; 25th March 2018 at 11:41 PM.
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  #12  
Old 26th March 2018, 12:10 PM
Black Stuart Black Stuart is offline
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Default Re: Disappointing Audiolab

Greg,
I've seen loads of posts about on different forums that state - mosfets are best when run hot. What I've never seen is any empirical evidence to back this up or any empirical evidence to show that when run 'relatively' cool the resulting sound is bad.

It was my Dutch mate Harry that first suggested using a computer fan beneath our hybrid h/amps with the base plate removed.

We listened to the sound of our amps run conventionally and with fan cooling. We both found that the fan assisted cooling gave a slightly liquid sound difference that we both liked.

Just as important it also meant that all components in the amps were operating at a lower temperature. If casings were made to create convection currents then operating temperatures would drop considerably and components would last a lot longer. Of course it's not in their interests to have equipment that lasts and lasts but the diy community should be experimenting.
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  #13  
Old 27th March 2018, 12:37 AM
Black Stuart Black Stuart is offline
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Default Re: Disappointing Audiolab

Just tonight saw that Massdrop is doing an Alex Cavalli designed h/amp @ $250. and designed in - convection cooling,it's about time. It has an ss and a valve section and uses a single 6992 valve.
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  #14  
Old 27th March 2018, 01:17 AM
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Default Re: Disappointing Audiolab

Stuart, your post supports what I say. This Massdrop has ‘designed in’ cooling. I hope it has been done taking into account the optimum operating temperature of any transistor being used. My point is that simply using fans to cool an amp where this was never intended in the design does not necessarily cause the amp to operate optiminally. Living in a warm country, adding fans to an amp not designed to work in higher ambient temperatures may well work, but there is no science in it and it certainly does not ensure optimum performance, albeit might prevent the amp from breaking with the immision of magic smoke.

Last edited by Greg.; 27th March 2018 at 02:29 AM.
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  #15  
Old 27th March 2018, 02:20 AM
colin.hepburn colin.hepburn is offline
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Default Re: Disappointing Audiolab

Each to their own here I think
If an amp is designed correctly it will have the correct heatsink sizing and work as intended without fans at the powers Wattages. we use in a home inverment and fans will always inject noise across the power rails this is why I donít use a pc for music anymore but that another story

I Use my pioneer amp as headphone amps with my HD650s but I run them a little hotter running them in Class A for a bit longer before they go into class B and they sound very good indeed only topped by my 5751/12BA4 single ended h/amp no fans
Pioneer SA-500A Quasi Complementary and the pioneer SA-6200 both recapped of course
Just my view others may differ
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  #16  
Old 27th March 2018, 10:21 AM
Black Stuart Black Stuart is offline
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Default Re: Disappointing Audiolab

Both of you are missing the point - the audio world, especially analogue are trapped in the past. Active cooling didn't exist in any form as little as 15 years ago and now it does.

Greg - the h/amp in question was designed by Alex Cavelli, not Massdrop, they are just an internet retailer, mainly driven by consumer polls.Check out his work.

Richard brought up the point that as early as the 1950s it was known that dropping the operating temps by 10C doubled the life of components. What a shame that listening tests weren't carried out at the same time.

Neither of you have ever used equipment that was actively cooled so your both talking from theory not practice. Isn't it time for the analogue boys to climb out of their self made boxes and experiment. Can either of you point me toward actual tests carried out on actively cooled equipment to back up your arguments, well can you?
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  #17  
Old 27th March 2018, 01:31 PM
bob orbell bob orbell is online now
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Default Re: Disappointing Audiolab

Stuart, I don't think Greg or Colin are arguing, you posted to me, that I should change my attitude, maybe you should practice what you preach, . BOB
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  #18  
Old 27th March 2018, 02:07 PM
colin.hepburn colin.hepburn is offline
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Default Re: Disappointing Audiolab

Quote:
Originally Posted by bob orbell View Post
Stuart, I don't think Greg or Colin are arguing, you posted to me, that I should change my attitude, maybe you should practice what you preach, . BOB
Hi all
BOB is right Greg and I are not arguing on anything
I just posted my views on my preferences on Amplifiers that I prefer i.e. for me which are older solid-state and my Valve amps single ended headphone and my JE.labs single ended 6SL7/KT66 with back loaded horns
thatís how I like my music played sorry but donít want fans in the system but thats me
PS. I have used many actively cooled systems but this was back in the day when I worked with Band PA systems using In excess of 5k by that brings back fun memories
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