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My 6AQ5 Princeton with tweaks
My 6AQ5 Princeton with tweaks
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Old 18th February 2019, 08:18 AM   #1
snaarman is offline snaarman  United Kingdom
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Join Date: Dec 2004
Location: Southern UK
Default My 6AQ5 Princeton with tweaks

In another thread I detailed my 8W dual 6V6 build. That drives a 12 inch Greenback in an old Fender cabinet that I covered in tweed. It sounds great to my ears and certainly hits the spot. However it weighs a ton and I need a trolley to move it. So the search started for a smaller version of the same thing.

I had the empty cabinet from a Champ 600 and some metalwork from a Fender BX15 transistor amp, so that's a good place to start. I modified the woodwork to take an 8 inch Celestion and chopped the metalwork to make it more valve friendly.

At this point I came across the EL90 or 6AQ5 and decided I could rework the original design with down sized valves and lower B+. The result is a 3W dual pentode single ended "Princeton" driving 8 ohms though a 1959 radio output transformer. Lovely...

This has all my usual tricks: Its a plain and simple no reverb two knob amp. It gets my asymmetric soft clipper in the preamp for low level breakup with a push button. I added some LED feedback bending to bring on soft breakup in the output stage and CTS pull switches to give mid and bass lift if desired. The amp has a built in kick back stand.

This has a slight tweak to the larger amp circuit. There is the usual L pad attenuator to bring the output down to 0.3W - but the feedback is taken after the pad. So when you drop the power, the amp also runs with less feedback and tends to break up more.

This also has most of the sound I like, soft blues breakup for late night playing, but that 8 inch speaker needs a larger box really. If you back the amp into the corner of the room, then the two three inch rear ports add a bit more bass.

My usual "gig" is in church. Some weeks I end up in front of the drum kit and next to the Sax. Under those conditions 3W maxed is only just enough to hear what I'm playing. Saxaphones and trumpets are loud things. I wonder if their owners realise...


Mini princeton front.jpgMini princeton rear.jpgMini princeton side.jpgMini princeton cct.jpg

Last edited by snaarman; 18th February 2019 at 08:21 AM.
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