F5 power amplifier

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#3,323
Hum on F5

Just finished my F5 DIY clone and it sounds fantastic. Small problem though as I hear a low level 60hz hum when both right and left audio cables are plugged in. no hum if only one side plugged in, either side.

The power supply is built to the schematic on PassDIY/Firstwatt site (F5 OM manual), and I am using a CViller cap board (very nice board by the way), and my own one-sided amp pc boards (artwork posted on earlier thread).

I tried multiple combinations of preamps, battery operated diskman, different cables, etc. but can't seem to lose the hum when both right and left input cables are attached.

Has anyone had a similar problem or could suggest where to look to get rid of this hum? Thanks, Joe
 
#3,325
power supply capacitor recommendations

Hello ,I am looking for recommendations on power supply capacitor brand and sources 22,000 uf for aleph 3 and 15,000 uf for F5 and also transformer recommendations [anteks any good?]or stick with piltron?.thanks for any input,peter
 
#3,327
hi all
a quik suggestion for all you guys needing powersupplys for your pass amps

i just use either the aussie amplifiers or greg ball ska kits for all my amp projects which are pre built and can be fitted with up to 60,000 mf per rail ,these work great and best of all come assembled so you just plug them in

with the aussie dollar the way it is at the moment over seas buyers will get a great price

regards sheafer
 
#3,331
I think thats just the mosfets and the rest of the parts produce an additional 25 watts for each side. He should consider that extra heat when working out his heatsink requirements. They will have to help dissipate some of that heat and the heatsinks will not work with perfect efficiency as one side will be in the hot box. Perhaps he could get away with 2 of those heatsinks and a fan for the inside.

Jim
 
#3,332
Re: Hum on F5

increek22 said:
Just finished my F5 DIY clone and it sounds fantastic. Small problem though as I hear a low level 60hz hum when both right and left audio cables are plugged in. no hum if only one side plugged in, either side.

The power supply is built to the schematic on PassDIY/Firstwatt site (F5 OM manual), and I am using a CViller cap board (very nice board by the way), and my own one-sided amp pc boards (artwork posted on earlier thread).

I tried multiple combinations of preamps, battery operated diskman, different cables, etc. but can't seem to lose the hum when both right and left input cables are attached.

Has anyone had a similar problem or could suggest where to look to get rid of this hum? Thanks, Joe
Click to expand...

Is the loudspeakers ground connected to star ground in the power supply board? is the input cable shielded? Can you post photos?
 
#3,335
bubba177 said:
i have 2 F5's ---one with plitron transformer and 15,000uf xicon caps---second with antek transformer and 22,000 uf panasonic caps, ever thing else equal....second is marginally better
Click to expand...

Interesting. I wonder what makes the difference? The Panasonic caps, the extra capacitance or the transformer itself?
 
#3,336
Re: heatsink question

khundude said:
would they dissipate enough heat for a F5 with 20C ambient room temp? As far as I can tell, it should give me around 50C heatsink temp.
Click to expand...
make sure you fit a latching temperature sensor that cuts the mains supply if it runs hotter in the warmer weather.
A 70degC switch located near one of the devices would probably do.
 
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