F5 power amplifier

I used PBJ interconnects which is 3 twisted wires, 2 - earth, 1 + , (only type of shielding used when I was a kid and still works,)

But out of preamp all 3 connected, into F5 only "+ red" to "SIN " on F5 board and 1 " -- blue" wire to GND on F5 board, "unconnected Black" then is a twisted shield that goes all the way back to pre amp and connected at that point only.
 
An externally hosted image should be here but it was not working when we last tested it.

From PSU
Green +24
Yellow -24
Black G


at last, i manage to make it almost zero hum(at least i cant hear anything even i put my ears near to the drivers) with above connections. The picture might too blur to read, but just for simple reference. Thanks andrewT, thanks all. Appreciate yours helps.
 
Looking good, sounds good to hey ! and will only get better.
you will never find a gainclone to soud as good as this,
match it up with some high end yesteryear gear as you can afford it, buy it off ebay, Tannoys etc and you wont want another amp.:wave2:

Try and get your cables looking tight like this pick.
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.

From PSU
Green +24
Yellow -24
Black G


at last, i manage to make it almost zero hum(at least i cant hear anything even i put my ears near to the drivers) with above connections. The picture might too blur to read, but just for simple reference. Thanks andrewT, thanks all. Appreciate yours helps.

Do you use fans ? If not, is the temp. of the heasink ok ?
 
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Joined 2002
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To give you a perspective, I use a 16 Ampere (100A surge) mains switch to turn on my F5 at the wall, and every time I flick the switch on, it lights up - literally. You can see the spark jump the gap through the thick white polycarbonate, as a gazillion amperes charge up the 160,000 uF capacitor bank (no inrush protection on mine) . I wouldn't trust anything less than a 30 ampere mains-rated industrial relay with a good surge rating, simply because of the huge inrush current.
 
I would never use a single relay contact to switch most anything. Multiple contacts for me.

If one uses a big cap bank one would do well to do a step-start consisting of a series resistor (~8-10ohm typically is good) to limit the inrush current, and then something to shunt the resistor for operation. Again I prefer multiple contacts in parallel.

Some people like "globar" thermistors for this function - I'd shunt them out too, if I was going to use such a thing...

Ymmv.

_-_-bear
 
Ex-Moderator R.I.P.
Joined 2005
Getting closer, and ready to order more parts :)
 

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  • F5 kabinet layout x2, DIY.JPG
    F5 kabinet layout x2, DIY.JPG
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As the amp has to "set up" on feet to clear the h/sinks, add the power input socket underneath between the transformers on an angle to get the IEC power cord into it - saves a lot of hassle.
Instead of all those big caps, consider a pair of Cmultipliers, like the F3, as you have room and plenty of spare h/sink area.