Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: AcornHouse on March 01, 2018, 06:09:18 pm
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Hi all, new to the forum, and just finished a Stout TMB build. I’ve been using a very vintage 5y3 in it, and it’s sounds great, although the low end can be a little TOO strong when it’s cranked. With the old rectifier, my B+ voltages are a little low (315-20 instead of 354), so I want to experiment with a solid state rectifier plug in to try to tighten things up.
The one that I’ve seen from AES say that you shouldn’t use one without a standby:
Note: Because there is no warm up of a rectifier tube when using this solid state device, it is critical that a standby switch is used that will allow the power tube filaments to warm up before high voltage is applied. This will prevent 'cathode stripping' in the power tubes.
True? Over caution?
Tks!
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Total BS.
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So, 320 divided by 1.1 (5Y3) maybe gives a PT with 290-0-290?
290 x 1.4 (solid state rectifier) is going to give 407v and if you are using EL84's, I think you will kill your tubes.
290 x 1.2 (5V4) = 348v which is probably max what you'd want on EL84's if that is what you are using?
290 x 1.3 (GZ34) = 370v which will probably toast your EL84 tubes if that is what you are using.
Look at the Tube Data Cheat sheet attached.
I will be surprised if changing the voltages tightens up the low end? I would probably try to accomplish that goal in some other ways such as increasing the value of the EL84 cathode cap such as increase the 47uf to 100uf maybe? You could experiment carefully by using another 47uf in parallel with the one you have using insulated alligator clipped wires.
With respect, Tubenit
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Many a Matchless Spitfires have been built and they have 348v on the plates. 285-0-285 PT