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Old 26th January 2009, 09:22 PM   #2481
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Would someone explain to me what the advantage is of this amplifier having a bandwidth to 500 khz. Is there a potential sonic improvement in the music? I know bandwidths to 60-70 khz are supposed to effect the high end dynamics, but 500 khz.

Thanks Tad
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Old 26th January 2009, 10:23 PM   #2482
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Quote:
Originally posted by labjr
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


Quote:
Originally posted by EUVL
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.
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Old 26th January 2009, 10:25 PM   #2483
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Quote:
Originally posted by EUVL
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.

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Old 26th January 2009, 10:29 PM   #2484
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Quote:
Originally posted by EUVL
>

Yes, but IMHO it does nothing to improve the richness of sound, which is already not its strongest point.

Hi Patrick
Have you tested local rail decoupling?

I'm not complainig about low richness in sound but it could be a bit better.

BTW, I'm running the amp as an integral... no preamp.
Fairchilds on P channel IR on N
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Old 26th January 2009, 11:29 PM   #2485
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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?

Click the image to open in full size.

Click the image to open in full size.


Fran

(PS: I'll post this on the F3/F4/F5 thread as well to hopefully let everyone know)
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Old 26th January 2009, 11:36 PM   #2486
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Quote:
Originally posted by woodturner-fran
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?

Click the image to open in full size.

Click the image to open in full size.


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.
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Old 26th January 2009, 11:53 PM   #2487
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Just to add:

Boards are really neat - and small. These will be quite easy to fit in a chassis. I know now I'm gonna have quite a bit of room to spare in there when I'm done.


On a brighter note my PS fired up AOK tonight with lovely 25.2VDC unloaded. Just right I would think.


Fran
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Old 27th January 2009, 12:33 AM   #2488
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Quote:
Originally posted by woodturner-fran
Just to add:

Boards are really neat - and small. These will be quite easy to fit in a chassis. I know now I'm gonna have quite a bit of room to spare in there when I'm done.


Fran
I was actually surprised the boards were so compact. I Would have to liked the outputs a little farther apart.
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Old 27th January 2009, 12:41 AM   #2489
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F3 board will accept regular size resistors. With F4 and F5 I'm using Dale CMF50: http://dkc3.digikey.com/PDF/C091/P1890.pdf

If you want to fit regular size resistors, just install them vertically, that shouldn't make any difference.
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Old 27th January 2009, 12:51 AM   #2490
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Quote:
Originally posted by labjr
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/attac...amp=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.

Click the image to open in full size.
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