F5 power amplifier

[umut1001]

i have no chasis and it sounds very well on the table..maybe it will be better with chasis

 

[woodturner-fran]

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

 

[Tea-Bag]

R11 and R12

Can R11 and R12 be 2 Watt resistors, assuming I use default settings and power supply?

 

[Nelson Pass]

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

Any heatsinks

 

[woodturner-fran]

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

 

[Studley]

JFETS

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?

 

[labjr]

Re: JFETS

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?

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

 

[rhysh]

Re: Re: JFETS

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

Thanks labjr!

 

[Nelson Pass]

That is our own member Jackinnj. I regard him as trustworthy.

 

[Studley]

Many thanks

 

[rhysh]

How much buffer capacitance are people planning on using in the power supplys? I was thinking somthing like a 100,000uf capacitor per rail? or maybe 2 x 47,000?

 

[AndrewT]

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.

 

[rhysh]

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.

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

 

[AndrewT]

I use 5off 15mF per supply rail on my KSA100 Klone.
I see little wrong with the high ripple capacity of 2off 47mF per supply rail.

 

[rhysh]

Thanks andrew!

 

[labjr]

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.

 

[woodturner-fran]

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

 

[labjr]

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

Probably more than enough.

 

[dhole]

Hope this isnt offensive but I have some F5 parts I dont need...

I have some spare FQA12P20 for sale here:

http://www.diyaudio.com/forums/showthread.php?s=&postid=1704679#post1704679

 

[rhysh]

Mr Pass, would you happen to have any high res versions of the schematics please? Need to print onto A3 paper. - Cheers