F5 power amplifier

labjr said:
Maybe wait for the B3 preamp.

When connected directly to the source (no attenuator) F5 offers the level of resolution I didn't experince before, adding any line stage, even passive, spoils the fun;)


EUVL said:
Firstly answer to Peter,

Thanks for sharing the info. I understand you run the amp balanced. Did you experience more body and improved dynamics comparing to single channel? At least that was my experience with GC amps.
 
The one and only
Joined 2001
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EUVL said:
Firstly answer to Peter, I have not tried IRF Mosfets for the F5, so I have to pass on this one. It is difficult to describe the difference btw Toshibas and Fairchilds. The bandwidth for both device types are similar, but the Toshibas just sound more natural.

I tried to increase gain to 20dB as this is what I have for my reference amps. I did mention earlier in one of my posts in this thread that the particular configuration of my balanced F5 was a touch on the bright side. Increasing the gain made it sound even thinner. But then I cannot speak for Nelson's version as published. I guess either you have to wait for his comments, or just try for yourself.

I increased gain by increasing the feedback resistor. This has probably the least consequence.

I haven't tried the Toshibas, but the IR's have a softer characteristic,
and more 2nd harmonic, either at low or high frequencies, depending
on how you balance the circuit. If you find the stock F5 a little
zippy, the IR's will tend to remove this.

The Fairchilds measure better and so I use them, but this is a
relatively trivial issue.

:cool:
 
Ok fellas I have a problem... or to correctly state it, you may have a problem.


A while back I posted a BOM from mouser for the F3 and F5. Quite a few people have asked me for it or downloaded it from the Peter Daniel F3/F4/F5 thread. There is an issue though that should be noted.

1) The 1/4W resistors won't lie completely flat against the PCB - you would need much smaller ones to do that. Not mission abort stuff, but be aware that you may need to stand them up, which is what I did.
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Also, somehow I ordered 47k instead of 47R for R13 and R14. The BOM is correct so no biggie there. I have only some very crappy carbon film 1/8W 47R here or a good number of nice Dale 100R. Which should I go with?

An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.



Fran

(PS: I'll post this on the F3/F4/F5 thread as well to hopefully let everyone know)
 
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Joined 2006
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woodturner-fran said:
Ok fellas I have a problem... or to correctly state it, you may have a problem.


A while back I posted a BOM from mouser for the F3 and F5. Quite a few people have asked me for it or downloaded it from the Peter Daniel F3/F4/F5 thread. There is an issue though that should be noted.

1) The 1/4W resistors won't lie completely flat against the PCB - you would need much smaller ones to do that. Not mission abort stuff, but be aware that you may need to stand them up, which is what I did.
**************************************************
Also, somehow I ordered 47k instead of 47R for R13 and R14. The BOM is correct so no biggie there. I have only some very crappy carbon film 1/8W 47R here or a good number of nice Dale 100R. Which should I go with?

An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.



Fran

(PS: I'll post this on the F3/F4/F5 thread as well to hopefully let everyone know)



Mounting soldier style for those dales is no biggie.

For the gate resistors, parallel 100ohms would net about 50 ohms. Close enough I would think. I would solder one on top of the other real tight, and then only try to stuff one lead through the PCB.

I order the wrong parts fairly consistently. Your not alone.
:D
 
labjr said:
I was actually surprised the boards were so compact. I Would have to liked the outputs a little farther apart.

Looks can be deceiving, the output devices are actually spread further apart than with the other boards: http://www.diyaudio.com/forums/attachment.php?s=&postid=1684454&stamp=1229205342

Besides, there are 4 mounting holes that allow board installation without mosfets attached and you can spread them as you wish, using wires. And that's what I call truly universal board, as some people might actually prefer it more compact, and I made it as compact as physically possble ;)

That format is specifically convenient when you want to install the board between two heatsinks set approx 3" apart; in that case the distance between 2 mosfets (like in F5) doesn't matter at all, only placement on a heatsink.

An externally hosted image should be here but it was not working when we last tested it.
 
Official Court Jester
Joined 2003
Paid Member
woodturner-fran said:
......
Also, somehow I ordered 47k instead of 47R for R13 and R14. The BOM is correct so no biggie there. I have only some very crappy carbon film 1/8W 47R here or a good number of nice Dale 100R. Which should I go with?
.....


there is a big chance that you'll like difference - with dreky carbon ones ;

under condition that you can hear difference , at all ....

( just look what Papa is constantly putting in his baaad amps - nothing more than plain industrial quality .......... :rofl: )
 
> I understand you run the amp balanced. Did you experience more body and improved dynamics comparing to single channel?

It is difficult to say, as I only tried single briefly, but with the same increased bias and reduced voltage. There is no lack of dynamics even in single, but it changes the characteristics of the sound just a touch, like you change from Aleph to Aleph-X (or 2nd vs 3rd harmonics, that sort of change).

Peter is known for optimisation with PSU and passive components. So I am among all the others looking forward to your experimental findings. Pls keep us posted.

(I am using PRP 0.25W and 1W resistors, and MPC74s for source resistors, as in earlier photos).


Patrick
 
f5 pcb

hi..my friend draw this for me..i wanna build f5 amp to 50cm of heatsink..for good cooling we decided to put the mosfets far eachother..what do you think about this?thanks
 

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Re: f5 pcb

umut1001 said:
hi..my friend draw this for me..i wanna build f5 amp to 50cm of heatsink..for good cooling we decided to put the mosfets far eachother..what do you think about this?thanks

Putting the MOSFETs far from each other isn't a bad idea (depending on your heatsinks), but why not use wires instead of making the board so large? It would at least be cheaper to make smaller boards...

-j