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Winter project: Pilot AA-920 conversion to power amp

Sounds very cool,,, Painted my last chassis a silver-gray,,, really looks good with black transformers,,, I put Oak side panels on it, and stained them black with ink,,, It was a recycled old Heathkit chassis, and some holes covered...
Keep the pics coming...

Regards.
John
 
Looking good, stamped the chassis also... 6L6s look close to the transformers, mine were about that close, because I recycled a chassis and used the existing holes... ended up putting a metal shield between them...
 
It may work out OK, and the metal shield I made just fastens to the PT, in my case,,, but even with the growing pains, I'd rather build something from scratch then repair existing stuff!! That amp should really sound good...
Keep teh pics coming!
 
I'm working on it now,it will be mostly the same, more capacitance,a little feedback fine tuning -(subtract) the 5Y3. I'm not going too crazy on this one.
I have a few more projects to do: A Scott 290 clone and a Conn (Mullard 520 build) before spring.and a Seeburg selector unit to rebuild.
 
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Keeping the 5Y3? I thought the plan was SS PS,,, Seems like you have a full plate!!
This one will be a very cool amp...
 
I would like to try various output tubes in it. If I connect pin 1 & 8 together I should be able to use EL-34's in it correct?
I would also like to use pin 6 as a tie point, does any other common output tube use it for something(except for 7027,8417 I don't plan to try these)
Should I use a 300 ohm cathode resistor for the most flexibility?
Thanks!
 
s-petersen said:
I would like to try various output tubes in it. If I connect pin 1 & 8 together I should be able to use EL-34's in it correct?
I would also like to use pin 6 as a tie point, does any other common output tube use it for something(except for 7027,8417 I don't plan to try these)
Should I use a 300 ohm cathode resistor for the most flexibility?
Thanks!
Click to expand...

1 and 8 will tie the 6CA7 K & G3 together, like the 6L6,,, if that's how you want to run it... 6V6, 6BG6, 6550, KT88...don't use pin 6,,,can't think of any other common octals off hand...
 
My pleasure, glad to contribute,,, 6F6, 6K6 also use those pinouts, if you want some old guys! Not sure they will all bias the same, tho... Maybe a switch to select different Rk? however, that may not be teh only difference between em...
 
There are still a few mismatched parts in it for testing,but it plays well for now. The output transformers don't get overly warm after 3 hours,
so I will not need shields.The power gets warmer, but not too hot after 3 hours as well.
The only thing that bothers me a little is the startup voltage exceeds the cap rating voltage by about 40 volts (490 vs 450)before the outputs start drawing current(about 10 seconds)then all is fine.
P1010029.JPG P1010031.JPG
 
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A new amp for Christmas!! Its getting there, I like the ground bus, should be very quiet... do you have inrush protectors, they may help the cap surge....
 
I have some here someplace, I'll try one when I find them. I installed a 100k
resistor to ground from the last cap, that helped lot. I've been listening to it since yesterday, right now in fact(classic Christmas music)
Have a Merry Christmas!
 
Nice little amp you have there , i alway have the problem it looks crowed on the top and empty underneath the opposite of yours .

Most Electrolytic caps have a 20% surge rating and 450 volt cap would be + 90 volts or 540 volt for 10 to 20 second warm up time , if they don't get hot your not hurting them .
 
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