F5 power amplifier

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#7,661
Just to be clear on this. No one is suggesting using A/S without an insulator like mica or a Silpad.

Yep, very thin layer. We use a razor blade to scrape (gently) off the excess, it's only to fill in the micro pores of the heatsink / heat generating device.

Ron
 
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#7,663
tinitus said:
Being capacitive means its conductive at very high frequency, no?
Click to expand...
no, it may act as a dielectric and factor up the capacitance between two adjacent conductors.

I am not trying to keep this argument going, but I believe the point is some of these silvery looking pastes are electrically conductive and some are not.
How can we tell them apart?

I think it's far simpler and easier to avoid the silvery type where electrical conductivity will cause a problem.
 
#7,664
AndrewT said:
no, it may act as a dielectric and factor up the capacitance between two adjacent conductors.

I am not trying to keep this argument going, but I believe the point is some of these silvery looking pastes are electrically conductive and some are not.
How can we tell them apart?

I think it's far simpler and easier to avoid the silvery type where electrical conductivity will cause a problem.
Click to expand...

Andrew T,
I couldn't agree more.
I have NOT used it on my F5, I was just trying to find out the "source" of the earlier comments against using it. As it has performed flawlessly for 100s of CPUs. (personally)

Tinitus,
"Being capacitive means its conductive at very high frequency, no? "

that's way beyond my expertise............If I had any.

Ron
 
#7,667
CPUs are electrically insulated whithin their case and the silver (which we all know is a very good conductor of electricity) is also a very good conductor of heat and is used for this purpose. The same company, Arctic Silver, also makes a thermal greese without silver for power mosfets and other electrically sensitive computer components. It is advised to use the proper compound for its designed application or you risk serious problems. It may be safe when used carefully, it may blow your amp if it creates an electrical short. Doesn't make since to risk your amp over a couple dollars worth of thermal greese. My 5 cents worth...inflation ya know🙁



Tony
 
#7,668
I use Ceramique for CPUs because it's a little thicker than traditional grease, so the heatsink won't slide around. However, I still use Thermalcote for almost everything else. Works fine for me. It costs less and is rated at higher temperature than all the Arctic Silver products. I think Nelson uses Thermalcote. So I'm guessing it's probably not necessary to use a boutique product for this particular application.
 
#7,669
I use Thermalcote for the usual reason - I have a large case of
it. The heat sinks on FW products are bead blasted, and the
result is that the surface is not smooth enough for really good
heat conduction without grease.

Another interesting factoid, the Drain of the Jfet in the F3 does
not use an insulating pad - the part is insulated by the grease
and the anodizing.

😎
 
#7,670
Renron said:
Just to be clear on this. No one is suggesting using A/S without an insulator like mica or a Silpad.

Yep, very thin layer. We use a razor blade to scrape (gently) off the excess, it's only to fill in the micro pores of the heatsink / heat generating device.

Ron
Click to expand...

otherwise you get a direct short from drain to ground, like me😱

(measured and confirmed all your suspicions)
 
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#7,671
It might work safer with device clips
Its tempting

I dont know if black anodizing are made in different ways
The only one I have tried to grind smooth with sandpaper showed a white and VERY tough layer of something between the black anodizing and the alu profile
Im sure that white layer isolates very effectively
Somehow I expect silver anodizing to be different

But the mounting screw may change things
Doing the needed thread can cause various things
Like material rise around the thread hole, etc
 
#7,672
Pblossom,

Thank you for your input, yours is the only direct response from the "horses' mouth". They should know their products strengths and weaknesses.

Papa bought a case of Thermalcote for a reason.......Yes? Good enough for me!

Anodization is a great insulator, but fragile and prone to scratching.

I'll save the Arctic Silver for the CPUs, YMMV.

Ron
 
#7,676
The gain of the F5 is ~6times (~+15dB)
the max signal from a cdp is ~2.1Vac.
The max signal from the F5 will be ~12.6Vac
This is equivalent to ~20W into 8ohms. Not quite full power.
The F5 sensitivity is just slightly more than most CDP and considerably more than lower voltage sources. A pre-amp with gain may be required depending on the voltage from your sources.

Now let's look at what SPL you can get.
20W is 13dBW.
The speakers are 94dB/W@1m.
The maximum SPL is ~107dB @1m
If your average level is 20dB below your maximum then your average listening level with zero attenuation from a 210mVac signal (-20dB ref 2.1Vac) will be ~87dB @ 1m. That is getting pretty loud for most listeners. But that requires a high maximum voltage source. Maximum average level will depend on your source voltage.
 
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