F5 power amplifier

[tinitus]

Originally Posted by cyclecamper

Not true if the heat conduction of the electrical insulator is relatively poor.

with classA, I hope its not

are you forgetting that with added heat spreader you have yet another material, and yet another connection
that itself would result in loss of heat transfer

this have been debated for year now
I'm surpriced noone haven't shown any data to prove efficiency of heatspreader
shoudn't be too hard

[h_a]

Not true if the heat conduction of the electrical insulator is relatively poor.

See it as electrical circuit - if you use a single small resistor or many large ones in parallel does not matter.

Think in terms of flow, if you impede small flow with a large area with little resistance it's the same as impeding it a strong flow with a small area and high resistance. Because in the end, what matters is only the amount of power (power density times area) and heat resistance (constant value). Changing the power density by changing the area does not affect the product of the two.

Anycase, discussion is academic, copper always looks better

Hannes

[AndrewT]

Originally Posted by tinitus

are you forgetting that with added heat spreader you have yet another material, and yet another connection

That is exactly what the manufacturer does inside the power package to improve heat transfer and reduce thermal impedance.

that itself would result in loss of heat transfer

this conclusion is complete rubbish.

[AndrewT]

Ha,
I am struggling with your various thermal terms and trying to get the logic to fit my understanding of heat flow.
Could you define what your terms are/mean?

[erpiii]

This is what I'm doing with my F5 copper to aluminum heat sinks. I have decided to isolate the output transistors so I am using 2 of these on each of my monoblocks. I am using diamond paste to attach the sinks to the copper bar. I will also be using diamond paste at the transistor on the copper bar as well. The heat sinks are mounted in compression using valve springs at around 180 psi on the inside of the heatsink. This should cancel out any thermal expansion differences between the copper and the aluminum. I also don't know too much about about thermal dynamics so I went for the brute force approach; not to mention getting a price break on the qty of heatsinks I purchased...

[peafarmer]

Hi, I hope I am posting in the right place.

I'm getting ready to start a diy build from nothing. So, I have no limits whatsoever in selection of my project (speakers, too). I have been lurking for quite a while, and it looks like the Pass amplifiers are very well supported and liked on this forum. So, I think I am going to build one.

My dilemma is matching the preamp to the amp. I see in a number of threads that the pass F4 is commonly matched with the Impasse tube amp and the Pass Pumpkin preamp.

I am also considering building an F5, I think I would actually prefer to build the F5. However, I don't see any consensus on which preamp is optimum for it. Maybe it is not a big deal...just use any old preamp? B1? Impasse? Pumpkin? Heretical?

Thanks in advance for any advice.

Andy

[h_a]

Could you define what your terms are/mean?

Sure;

power density=heat flow/area=amount of heat energy** per second per m^2
heat resistance=1/thermal (heat) conductivity -> heat transfer equivalent term of a resistor, defines the temperature difference created when a unit heat flow is conducted (unit: degree Celsius per Watt). From the unit one can see that this property does not depend on the area or power density, only on the heat power transfered. It does not bother wether its a large area with low power density or a small area with a large one.

Hope this helps! Hannes

**heat energy=power dissipation of the fet in this case

[regiregi22]

Originally Posted by peafarmer

Hi, I hope I am posting in the right place.

I'm getting ready to start a diy build from nothing. So, I have no limits whatsoever in selection of my project (speakers, too). I have been lurking for quite a while, and it looks like the Pass amplifiers are very well supported and liked on this forum. So, I think I am going to build one.

My dilemma is matching the preamp to the amp. I see in a number of threads that the pass F4 is commonly matched with the Impasse tube amp and the Pass Pumpkin preamp.

I am also considering building an F5, I think I would actually prefer to build the F5. However, I don't see any consensus on which preamp is optimum for it. Maybe it is not a big deal...just use any old preamp? B1? Impasse? Pumpkin? Heretical?

Thanks in advance for any advice.

Andy

Quite some people like to match it with the Pass B1, or its improved DC-coupled version DCB1.
There may be no such a thing as a best preamp for it, some people like a tube flavour, others like whatever-is-it while not having OPAMPs...

[Marra]

Originally Posted by peafarmer

Hi, I hope I am posting in the right place.

I'm getting ready to start a diy build from nothing. So, I have no limits whatsoever in selection of my project (speakers, too). I have been lurking for quite a while, and it looks like the Pass amplifiers are very well supported and liked on this forum. So, I think I am going to build one.

My dilemma is matching the preamp to the amp. I see in a number of threads that the pass F4 is commonly matched with the Impasse tube amp and the Pass Pumpkin preamp.

I am also considering building an F5, I think I would actually prefer to build the F5. However, I don't see any consensus on which preamp is optimum for it. Maybe it is not a big deal...just use any old preamp? B1? Impasse? Pumpkin? Heretical?



I can certainly recommend Salas excellent DCB1; even better when used in conjunction with an LDR type attenuator.

Salas hotrodded blue DCB1 build

Lightspeed Attenuator a new passive preamp
Thanks in advance for any advice.

Andy

[regiregi22]

I use the same arrangement, DCB1 with an LDR attenuator

I'm a happy user