F5 power amplifier - Page 1262

AudioSan · 18th October 2012, 01:55 PM

Quote:

Originally Posted by Abx74

I ordered and received F5 stock PCB few days ago, v2.20 and no P3 on board

Damien

you can hard wire the P3 without much problem.

Abx74 · 18th October 2012, 06:08 PM

My F5 will be a stock one in first time... Tweaks will come after if necessary.
Transformers will arrive tomorrow, I have ordered two 300VA 2x18V, one for each channel

Damien

labjr · 18th October 2012, 06:13 PM

Quote:

Originally Posted by AudioSan

you can hard wire the P3 without much problem.

I wanted to add P3 to my project. I'm a little worrried about causing extra noise, oscillation etc. if the pot is too far from the input FETs.

AudioSan · 18th October 2012, 06:21 PM

Quote:

Originally Posted by labjr

I wanted to add P3 to my project. I'm a little worrried about causing extra noise, oscillation etc. if the pot is too far from the input FETs.

solder the P3 direct to the legs of R1, R2? (10ohm resistors)

jackinnj · 18th October 2012, 09:09 PM

Here's the schematic to go with the revised board:

labjr · 18th October 2012, 10:50 PM

Jack, have you tried moving R1 to the other side of R2 as seen in the F5 Turbo manual?

AudioSan · 18th October 2012, 11:06 PM

is there a reason for the 47.5K input impedance? vs. 100K as Cviller's schematics?

labjr · 18th October 2012, 11:25 PM

Quote:

Originally Posted by AudioSan

is there a reason for the 47.5K input impedance? vs. 100K as Cviller's schematics?

The changes to the F5 circuit are in the F5 tubo manual. I just figured they are the latest therefore they must make it better.

jameshillj · 19th October 2012, 12:21 AM

John,
I see you haven't included the provision for the small value gate stopper resistors (47R & 68R) and filter capacitors on the input jfets, as in your early design with the double sided board?
Did you find these additions to be counter productive?

Is it possible to line the power resistors up "sideways" to attach the Caddock style (TO220/247 packages) power resistors to a common heatsink thru the centre of the board?

And perhaps adding a Cmultiplier/simple zener regulator onto the ends of the board with room for 25mm power supply caps?

jackinnj · 19th October 2012, 11:19 AM

Quote:

Originally Posted by labjr

Jack, have you tried moving R1 to the other side of R2 as seen in the F5 Turbo manual?

Good idea. The way i have it setup is as a voltage divider for no useful reason! My bad.

18th October 2012, 11:06 PM	#12617
AudioSan diyAudio Member Join Date: Feb 2009 Location: Trondheim	is there a reason for the 47.5K input impedance? vs. 100K as Cviller's schematics? __________________ aleph P1.7 pre. F5 power amp. CDpro2(need DAC). Vivaldi8 speakers

19th October 2012, 12:21 AM	#12619
jameshillj diyAudio Member Join Date: Feb 2005 Location: Melbourne, Aust	John, I see you haven't included the provision for the small value gate stopper resistors (47R & 68R) and filter capacitors on the input jfets, as in your early design with the double sided board? Did you find these additions to be counter productive? Is it possible to line the power resistors up "sideways" to attach the Caddock style (TO220/247 packages) power resistors to a common heatsink thru the centre of the board? And perhaps adding a Cmultiplier/simple zener regulator onto the ends of the board with room for 25mm power supply caps? __________________ ... jh

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18th October 2012, 06:08 PM	#12612
Abx74 diyAudio Member Join Date: Dec 2011 Location: Bourg-en-Bresse	My F5 will be a stock one in first time... Tweaks will come after if necessary. Transformers will arrive tomorrow, I have ordered two 300VA 2x18V, one for each channel Damien

18th October 2012, 09:09 PM	#12615
jackinnj diyAudio Member Join Date: Apr 2002 Location: Llanddewi Brefi, NJ	Here's the schematic to go with the revised board:

18th October 2012, 10:50 PM	#12616
labjr diyAudio Member Join Date: Apr 2003 Location: MA	Jack, have you tried moving R1 to the other side of R2 as seen in the F5 Turbo manual?