Bottlehead Forum
Bottlehead Kits => Legacy Kit Products => Stereomour => Topic started by: jimiclow on June 05, 2012, 02:08:14 PM
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Hello all!
I'm one and a half month away from receiving my Stereomour kit. I will be building it as a stock first then slowly upgrade later, starting with the parafeed and coupling caps.
I started with a Decware Zen, Taboo/CSP. They're all tube-rectified and I'm wondering whether the Stereomour can be tube-rectified. Supposing I have another transformer that has a tap for the 5-volt rectifier filament, can it be done? Are there any advantage/disadvantage/s with using tube rectifier?
I have stopped tube-rolling in my current set-up as I cannot hear (or hear only very little) difference between tubes. Maybe it's just the idea of an "all-tube" amplifier.
I just built a stock crack last month and was very pleased with the result.
Thank you.
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It can be done, and I'm sure that a different transformer will be key. The question is whether it will improve the sonic performance. The SS diodes that Doctor and Paul chose were selected for their quiet performance.
It will definitely give a different presentation and might be preferred by taste.
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My advice would be to build it stock and listen first. I don't know how much voltage overhead the stereomour has and whether it will be enough to leave sufficient B+ after the forward voltage drop of the common tube rectifiers, but I'd suspect there would at least be some loss of dynamic response due to the greater voltage overhead of the rectifier and the typically higher output impedance of the power supply as a whole. Probably will be somewhat noisier too, though whether that will be audible or not is an unknown.
Not trying to discourage you but the voltage is the unknown for me at this point and that could be the deal breaker.
HTH,
Jim
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You could recover a good bit of wasted voltage using a hybrid bridge. The tube(s) closest to the filter circuit and two diodes back to ground. Eli Duttman pointed me to this configuration.
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Thanks for all the replies. I will update this thread once I start building the kit.
I already have different schematics for tube-rectified 2A3's.
I have no luck finding 45's on ebay.
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The power supply uses two diodes in a voltage doubler, so you'll probably want a rectifier with independent cathodes, not directly heated. You'll also want a low voltage drop, since the doubler has twice the drop of a regular center-tap configuration. A pair of damper diodes would be ideal, or a dual damper like 6BY5.
A 12DF5 looks interesting. It can be powered from the Stereomour power transformer. Not enough current for the 2A3, but enough for a pair of 45s. The extra voltage drop might suit the 45 just fine - no need to increase the PSU resistor to make the correct voltage. I haven't checked the peak current or heater-cathode voltage requirements yet.