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Excuse for a class A DIY AMP build?

Fans make a huge difference! Not that the heatsinks on that case are ideally designed or placed for use with fan cooling. You can dissipate maybe 2-3 times as much power with a fan when compared to without for same heatsink size and fin area.
 
I’ve been scanning second hand sales for ages looking for dual secondary 18v transformers, no luck.

Today thought bugger it, time to buy new - scanning eBay I find some 225va Talema items. No dimensions on eBay so I go search the part number - they’re available to order direct for 40% less than eBay price direct from manufacturer! Two on their way to me now - Talema is Polish I think, no idea of quality, but at least let’s me get started...

Think I have most of the other bits now, only real question is if I should put some Avondale CAP6s I have As spares in front of the Rev2 boards I have, bypassing the rev2 onboard rectification - any ideas?

Thanks, Richard
 
question is if I should put some Avondale CAP6s I have As spares in front of the Rev2 boards I have, bypassing the rev2 onboard rectification - any ideas?

Perhaps I'm missing something, but have you read up on the theory behind the onboard supply? At first glance a conventional diode bridge looks like a step backwards. (Not that I've tried either, yet.)
 
Perhaps I'm missing something, but have you read up on the theory behind the onboard supply? At first glance a conventional diode bridge looks like a step backwards. (Not that I've tried either, yet.)

Not checked to be honest, hence the question really - you may we’ll be right though, need to dig the boards out and check the circuit.

thanks, Richard
 
From the stand-alone psu blurb on Etsy.com: 'Use of the LT4320 active bridge and low RDSon MOSFETs as the rectifiers means that there is almost no heat generated in the rectifier (a traditional source of large amounts of heat under heavy Class A loads). The active bridge also switches at zero crossover thereby minimizing noise generated by the rectifier. A carefully engineered CRC filter requiring only 2 x 15,000uF bulk caps followed by a complementary feedback pair (CFP) capacitance multiplier (Cap Mx) takes the traditional 100mV rms ripple CRC PSU down to in-audible 1mV rms ripple. You will hear the blackest of blacks in your amplifier’s background now.'

This is, of course, the vendor's description and I've yet to try one out (the boards + p&p + VAT are expensive) but 'almost no heat' sounds good for your application.
 
I think (but am not sure until I check my boards, which will not be for another couple of weeks) that my issue 2 boards have the dynamic PSU and bootstrap on the single PCB, so would just bypass the diodes/fuses on them and feed it with smoothed DC from the cap6s - that assumes the chassis has space to do so, need to check.

I need to also think about the fans I have, and I guess a copper heat Spreader will also be needed - for sure my heat sinks will not be up to the job by themselves I think (anyone have links for copper heat spreaders? Links in old Threads have expired).

Thanks, Richard
 
Transformers delivered today. Also had a very quick look at my issue 2 boards, they just have standard diodes and a 33k uF (85 degree) after them, so I could easily incorporate the cap6s if I wanted to/have enough space by bypassing the diodes. Need to spend some time and do a mock up in my chassis I think.
 


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