F5 power amplifier

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#2,402
Early chassis work:

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.



Pretty conventional I know. Paint and polish yet to be applied. The heatsinks are mounted with a spacer between them and the sides of the case. The plan is to mount the devices directly to the heatsink through a hole in the side wall of the case. The idea is to keep some of the heat out of the case and hopefully there will be a bit of a chimney effect in the gap between the heatsink and the case.

What about heatsinks for the diodes? I am using some T03P diodes - what sort of heatsinking can I expect these to need?

Fran
 
#2,405
Many thanks. I kinda got concerned cos the heatsinks (2" thermalloy ones for T0220) get upto nearly 60 deg C on my mini aleph. So thinking that this might have a bigger current draw, I thought maybe it might need bigger heatsinks. Should have explained that.....

I have some fairly substantial ones lined up anyway.


Fran
 
#2,407
Re: JFETS

Studley said:
I'm trying to find somewhere to buy the Toshiba JFETS. There some ebay sellers based in HK and Taiwan but I've heard that there are lots of counterfeit copies being sold. I'm looking for some advice or the name of a pukka seller, anyone?
Click to expand...

I think this guy has authentic parts. I ordered some chip amps a while back with no problems.

http://www.tech-diy.com/Store/SmallSignal.htm
 
#2,413
AndrewT said:
Hi,
smoothing capacitance for a ClassA amplifier needs to be big.
You may find that 47mF is a bit low. Most would be happy with 100mF.
Click to expand...


And using 1 100mF capacitor per rail would be more effective then using 2 47mF capacitors per rail? I have allways heard people say using two is better, even if the overall capacity is slightly less.

Cheers
 
#2,416
I've always felt it would be better with more smaller value caps.

However, I don't know what the difference would be with several lower value caps. Maybe, lower ESR? Better reliability?

I just remember drooling over Threshold brochures 20 year ago and they always described a lot of capacitance in the power supply.
 
#2,417
Yep, and Peter Daniel has done the PS for the F5 with 2 caps each side. I think he mentioned using 2 x 15000uF for each of the + and - supplies - although the board spacing will allow for bigger I think.

I intend going dual mono and using those 4 x 15000 per channel giving 60000uF total for each channel.

Do you guys think its enough?

Fran
 
#2,418
woodturner-fran said:
Yep, and Peter Daniel has done the PS for the F5 with 2 caps each side. I think he mentioned using 2 x 15000uF for each of the + and - supplies - although the board spacing will allow for bigger I think.

I intend going dual mono and using those 4 x 15000 per channel giving 60000uF total for each channel.

Do you guys think its enough?

Fran
Click to expand...

Probably more than enough.
 
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