F5 Turbo Builders Thread

Heatsink or no heatsink is solved or irrlelevant..... Just make sure you got an adequate heatsink. Here is my question. PLease explain this statement and how it relates to the ouput power of the amp.

"What if you remove the Source resistance altogether?
First off, you get the 44 amps. In addition, with Fets you get an output stage
that will deliver more Class A power at a given bias figure due to the square​
law character of the Fets."

"The result is that the amplifier can now deliver 38 amp peaks"

First statement seems to suggest a cheat for more pure Class A, but the second seems to slip into the A/B category. Funny that he has addressed this very topic in another article, but equally funny that he has chosen to take his Pass amps in the dircection of more true Class A power.
 
So Class A is still Class A and diodes just allow full acces to given fets abilities, even if it is of a hybrid nature. Funny, all this talk of power, I was uncomfortable listening to single pair version:D. Of course i do not have proper multiway speaker and lsiten to silly FR stuff with woofers.

Buzz,

Which Maggie do you have?

I'm using 3.6's driven by AX100J's. Although I really like the sound I'm getting, you guys are starting to make me wonder, in an expensive kind of way, how an F5T would compare.

Let me say that I appreciate the encouraging way you all are sharing your results. Great work!

Graeme

1.6, but not mine.
 
Last edited:
I don't recollect hearing about these diodes being used in any Pass main line product. But then they haven't been including the "Fun Hardware Facts" section in the manuals for a long time. So who knows.

That being said the diode idea is particularly clever and is a real plus for smaller amps that need the ability to produce extreme current peaks.

Graeme
 
i can't see any advantage over external or main heatsink

On the MUR3020W datasheet, the Vf axis is linear, but the vertical axis is logarithmic scale.
10-15 degrees doesn't make a significant difference in Vf, so mounting the diodes on one heatsink or the other doesn't make the diodes kick in a lot sooner.

But a 15 degree jump in diode die temperature does make a difference current wise.
Take the example of my previous post : 40C or 50C diode temperature means ~0.865A or 1.25A diode current at a Vf of 0.6
One MOSFET would do ~2A drain current, the other nearly 2.5A

10C temperature difference between one location of a heatsink and another isn't that round the bend.
(e.g. EUVL's heatsink measurements in the latest LinearAudio fagazine)
 
buzz

context is very important .

Absolutely. I am not in need of the power, but just trying to help with the parameters for those that are, since i have the amp built and can test and talk. Too much talking, sure. Whats that among friends? Diode heat discussion was roundabout way of introducing the importantce of adequate sink. Don't want anyone to underestimate what 4 pairs of oututs @1A with 32V rails will do to a heatsink. Normal amps are sensitive to proper sinking, but in this one, even more so, as we have added another variable that introduces possible instablilty directly related to temperature. It is of great help when you, Andrew, Jacco, FLG and others chime in to help as many of us are just wading in with much less experience. To that i have a :cheers:
 
Everything I can find has a minimum order of around $30-$40.

Still sounds fair to me.

I can buy disc spring washers by the piece if i drive up to a Fabory store, nearest to my place is 15 minutes by car.
If i order them online from Fabory, i'd have to buy a hundred minimum, plus mailing cost, company account.

For Belleville washers in the US, you likely need a similar fastener supplier, local, they're not run off the mill parts a general hardware store will have.
(Fabory e.g. has stores only in Grand Rapids and Houston)

trivia : Jean Francois Belleville in France patented these washers +150 years ago
 
Official Court Jester
Joined 2003
Paid Member
:eek:


:clown:


Papa is pullin' ya leg (with stat)

that's thermoswitch

normally On
 

Attachments

  • ts.jpg
    ts.jpg
    22.9 KB · Views: 875