Thermally coupled JFETs

[Osborn]

Please, can someone describe the need for JFETs to be thermally coupled (seen done with a zip tie) on projects such as the DIY Audio F6, where when I look at the Pass F6 (6moons.com) board, they are not thermally coupled. Many thanks.

 

[cbdb]

Fets change there parameters with temperature. If they need tobe matched ( which depends on the circuit) they should be the same temperature. if they arent using much power ( they dont warm up) they will be close ( both around room temp) and if they burn exactly the same power and are close together they will be close, But to ensure the same temp they are coupled, or you buy matched pairs on the same die ( same IC).

 

[Zen Mod]

that's we just being superanal , substituting competence with tidiness




if you want to see what's proper engineering , just look at Pa's

not saying that's sole possible way, of course

 

[Osborn]

OK then. Thank you. I knew there had to be some reason, just wondered what I was missing. I do have matched FETs, new stock from DIY Audio.

 

[egellings]

Basically, parameters of 2 devices track with temperature when they are thermally connected together.

 

[adason]

make sure you use audiophile zip tie

 

[2 picoDumbs]

Yeah they have to be Teflon.
Hahahaha

 

[UserAbuser]

The zip tie is a bad way of doing this.
If you do it to tight it will strangle the sound.

For the best results you put a smear of heat sink compound between the faces, then you use heat shrink to 'bond' them as it gives a nice uniform clamping tension.

 

[6L6]

The zip tie is a bad way of doing this.

If you do it to tight it will strangle the sound.

 

[tsmith1315]

That's why you should use wooden zip ties, the natural porosity lets the JFETs breathe.

 

[gadut]

if you use zip tie, you'll get plasticity sound
using wood will deaden the vocal because it's porous

to make a smooth sounding Jfets, a silk band is the best choice. it will give you warm and smooth sound with less reverb because already absorb by silk surface

 

[2 picoDumbs]

Yeah silk is even better than teflon, this is a very much under appreciated fact.

 

[rgregg3]

Add color silk to suite your musical taste!

 

[UserAbuser]

I always serious..... Or am I ?

Problem with using silk is the GF getting mad at you for cutting up her undies.
Plus side is she gets more g-strings

 

[Osborn]

Heat sink compound for sure. I’ve seen the heat shrink tubing used but wondered if it woundn’t Give way as the fest got warm. One way to find out.

 

[DualTriode]

Thermally Conductive Potting Compounds | Electrolube - The Solutions People

 

[Osborn]

I had always wondered about this stuff. I've got some transformers that need to be potted. We digress.