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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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In Reply to: Phase inverter tube choice question posted by airtime on May 8, 2020 at 09:05:53:
For me the magic came with the 12AU7 in the centre and 12BH7s on the outer positions. For the former I used an old stock US brand and the latter the Electro Harmonix which I have found repeatedly to be a great sounding 12BH7.
Note that this driver board uses more current from the HV, (I think around 26mA) so will push the transformer and rectifier tube to the limits. The board supplier has suggested that the output tubes be run at 40mA vs the stock 50ma to extend their life but really I think it is to offset the extra loading from the board. I compared the sound of 40mA to 50mA and found the 50mA to be significantly better. So there becomes the issue - best sound equals overloaded transformer and rectifier.
My solution was to put the amp in a wooden chassis box with an adjacent bay which houses two 5AR4s, a bigger choke, additional capacitance and install a reissue power transformer which has slightly more capacity and is better matched to today's higher line voltage. The result is a superb sounding amp and power transformer that runs slightly hot (63C).
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Follow Ups
- RE: Phase inverter tube choice question - sayntjack 23:46:17 05/10/20 (1)
- RE: Phase inverter tube choice question - airtime 07:10:14 05/11/20 (0)
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