F5 power amplifier

[tinitus]

speaker terminal ground goes nowhere else, other than the speaker negative

but the signal RCA shield connects to other electronics grounding 'point'
I think that should be the main 'concern'

[jacco vermeulen]

Originally Posted by WalterW

My dual mono F5's

Fast operator.

[WalterW]

Hahaha Jacco, I must say I haven't seen my wife a lot lately...
Building this amp sure takes some time...

[WalterW]

Originally Posted by 6L6

Walter -

Use only one bridge as the resistance between chassis earth and audio ground... having two seems like it will only add a potential loop.

Take the speaker return (black or negative speaker connection) from the amp PCB, not the PSU - it's much quieter that way.

Also, if possible, please draw a schematic of your wiring, it will help us understand your connections.

Nice work, by the way - neat wiring, good layout, I'm looking forward to seeing more photos of your amp!

Hi 6L6,

I don't know if I can use only one bridge, cause I have two separate main audio grounds. Or should I connect those first and then go through one bridge to earth? Hmm...
The schematic is attached, it's from the F5T. Only twice in my case; for each ampboard one PSU.
Thanks for the compliment ! I will post more.

Grtz, Walter

[slungu]

Originally Posted by Nelson Pass

There is too much concern about these particular Jfets for the front end
of the amplifier. Yes, the 2SJ74 and 2SK170 are really superb, particularly
on the noise front, but this is not as important when we are already dealing
with line level volts instead of millivolts.

You can still get the Fairchild J174, J175, P1086 P channel devices from such
places as Digikey and Mouser, and they are cheap.

The N channel are even easier to get, such as the Fairchild J111. Worst
case you might have to parallel two, but even that is unlikely. You might
have to select them, but at prices like $0.11 for quantities, you can hardly complain.

Better buy them before I do....

Well, I can not find any P-channel J-FET, the Toshiba is available, but at a high price and is operating outside the specification if I am using 32V rail voltage. I also noticed that both J111 and 2SK170 have no problem with the higher voltage, but the 2SJ74 is specified for lower voltage, and none of the other types seem to be available at the usual suppliers around here. Was hoping to do a Turbo V1 with .8A/device.

[Nelson Pass]

Build it with cascoding. Easy to do.

[tinitus]

any reason why the diode bridges diodes are connected in paralel as one bridge, instead double bridge ? (or am I seeing it wrong)

[Nelson Pass]

Originally Posted by tinitus

any reason why the diode bridges diodes are connected in paralel as one bridge, instead double bridge ? (or am I seeing it wrong)

The special audiophile rectifiers come in pairs with 3 pins and only one polarity.
You can't configure them as a standard 4 connection bridge, so you use them
in parallel.

[WalterW]

Haha Tinitus, and I'm using those 'special audiophile rectifiers'
You can see them in my picture, the ones with little heatsinks on them...

Initially I bought the 35A/200V rectifier bridges, untill someone told me to use the special diodes. That's why I'm having 2 ground loop breakers

[tinitus]

ah, ok, thanks
I have used 8 of them per mono amp
but never noticed each consisted of two diodes in paralel