Subject: Inverted Passive Heatsinking 'Detrimental'?
By: Zeruel (IP: 203.134.137.*)
Written on: 15-10-2005 13:17

Not PC related, but definately Heatsink related.

I own a headphone / pre amp. It has no external heatsinking of any sort, (unless you count the textured metal enclosure. It produces a fair amount of heat for its size. I've been told this is normal for amps in its class (ie, Class A) Coming from a PC background, I sought to lower operating temp.

I've put some Thermaltake Copper Ramsinks on its underside. There is not much clearance between desk and and the heatsinks. I've raised the amp just a little bit.

Can the use of Passively cooled heatsinks (inverted / upside down) as they are, actually have a detrimental effect? ie. Trap heat, or work in ways not intended?

By: Tillmann (IP: 146.140.7.*)
Written on: 15-10-2005 23:38


yes, it is normal for Class A amps to get very hot. However, they're designed to handle that (I mean, a class A preamp isn't something you buy for $19.90 at your local electronics superstore; typically they're expensive units and a lot of engineering work went into them :-)).

Trying to improve cooling might only make sense if you're running the amp beyond its specifications, e.g. with headphones that have lower impedance that the amp is designed for. Or if you are running it under extreme environmental conditions.

If you're running it within its specs, additional cooling might even have a negative effect on sound quality. Many transistors sound better when warmer.
Additionally, if you don't consider the internal placement of components when placing the heatsinks, you might provide more cooling to the one channel of the amp than the other, resulting in different characteristics of each channel.

BTW I'm an audiophile guy myself. My class A headphone preamp is an early 1980s FM Acoustics model, - i use it with beyerdynamic BT550 headphones, and I usually listen to electronic music, mostly Ambient and Psytrance. It's fun to see other ppl interested in audio show up here in the forum!

By: Zeruel (IP: 202.138.30.*)
Written on: 18-10-2005 05:56

Thanks for the reply, Tillman.

I don't believe I'm running the amp beyond spec. First, a bit of added info.

It's a Talisman Audio T-35hp ( Its rated for loads of 30 to 600 ohm. I use it to drive a pair of Beyerdynamic DT880's which are only 250ohm nominal. (My first setup, )

I was also using PRE OUT to go to my (powered) PC's speakers. Hardly a challenge for pre-amp i would think. (I think they may even have sounded better, considering adding poweramp and speakers)

The amp is permanent powered and has no 'off' switch. Apparently this to maintain 'optimal electrical and thermal conditions'. Suffice to say, its never 'stone cold' when idle

I made the following post over at Head-Fi not too long back.

Following the thread. I did put aforementioned ramsinks on the underside. The effect of these appears to be minimal (overall) compared the large heatsink i have sitting loosely on top.

The hottest area of the amp is front centre on the underside. And thats where i have the ramsinks, as close to symmetrical as possible. (Its a Dual Mono design)

Would you recommend I remove the heatsinks and put faith in the skills of it's designers? (I thought i could maybe extend life a little by sucking excess heat off the casing)

Apologies for length.
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