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Tube amp progress

Posted 21st September 2012 at 03:19 AM by wlowes

In the past few weeks I have made progress on by OTL amps. The wooden bases are finished, and I am very happy with the finish.

I reformed and tested all the big can caps. The Nippon Chemi Caps are fine. The big old Samgmo caps make me too nervous to consider using them. They may be serviceable, but have a high leakage current compared to the Nippons and do not seem to hold a charge. Perhaps I'll use them in some other project. I will buy 2 x 2200 caps for each rail. 4 per mono and 8 in total. This caused yet another redesign of the top plate. I have now got room to place a big heat sink on top. It will disipate heat from bridge rectifiers and big resistors used for soft start.

Finally I started to build. While all point to point wired, the amps will be modular. I am using wood blocks as the base for each power supply circuit. I laid out the supply for the small tube anodes and wired them up. This way the caps are well supported and vibration damped. Also I can test each supply outside the case which I think is safer and easier. If at some future point I want to change or upgrade, I can just swap them out.

They turned out really nice, and appear to have the target voltages when there is some load applied. Pictures show the build progress and the finished product in the reflection of the finished base. It's great to finally get a soldering iron on these beasts. Still have to place a final order for parts, tripple check the sizes prior to committing to CNC the top plates.

Another problem to solve.. I seem to have trouble hitting the target voltage for the filament supplies. Damn, I do not seem to know how to size a transformer. Oh well.. back to thedrawing board. At least I am sorting this stuff out BEFORE I build it.
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