I'm getting interested in building this preamp. It's a very long thread so maybe this question has been answered before. I'm interested in building a tube rectifier version of it. I haven't seen the 6CA4 indirectly heated rectifier brought up. It has a 6.3 volt filament which I like. It's supposed to be appropriate for preamps and has a 150ma dc current maximum.
Is there any lore about this rectifier that would make it a bad choice. Or for that matter is there anything special I should know. I've never really understood the whole directly heated tube thing very well and would just like to avoid them if possible. I think the whole preamp should use about 85 ma including 2 each hv regulators.
Is there any lore about this rectifier that would make it a bad choice. Or for that matter is there anything special I should know. I've never really understood the whole directly heated tube thing very well and would just like to avoid them if possible. I think the whole preamp should use about 85 ma including 2 each hv regulators.
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Direct or indirect heating makes very little difference on a rectifier... If you want to use a tube rectifier, go ahead, it sounds like fun!
In general the IH rectifier types have less forward drop & better regulation properties than the directly heated types. And if properly connected, a smaller power frequency component in the resultant ripple (hum) on the DC.
AZ1 or AZ11 mesh plate is the creme de la creme, but that's European. I use them everywhere. Be aware that you can also use a hybrid or Graetz bridge if your secondary winding has no centre tap.
Looking at their respective spec sheets I fail to see anything special about these rectifiers. Aside from the European base & odd filament voltage, they are pretty much like any other DH vacuum rectifier.
Its obvious to many that each manufacturer built their own unique version of a tube in order to control their replacement market. Luckily not so much here in North America, standardization was a wise move forward.
Pls advise.
Looking at their respective spec sheets I fail to see anything special about these rectifiers. Aside from the European base & odd filament voltage, they are pretty much like any other DH vacuum rectifier.
Its obvious to many that each manufacturer built their own unique version of a tube in order to control their replacement market. Luckily not so much here in North America, standardization was a wise move forward.
Pls advise.
Too simple? https://www.mouser.ca/ProductDetail/STMicroelectronics/STPSC10H12CWL/?qs=u4fy/sgLU9PSqdYUwTSJjg== (Yes, I know OP wanted a tube but IMHO there's no good reason to use a vacuum diode unless it's a 6AL5 for the lack of drop) [I don't even use these - HER*08 is plenty fine and much less money].
Too foreign? https://frank.pocnet.net/sheets/095/6/6Z4.pdf 70mA current is probably enough for a 6V6 preamp. Get two and parallel the plates and save your money - 6CA4 are getting expensive!
Too foreign? https://frank.pocnet.net/sheets/095/6/6Z4.pdf 70mA current is probably enough for a 6V6 preamp. Get two and parallel the plates and save your money - 6CA4 are getting expensive!
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Seems odd we would hear the rectifier at all given that the PS filter section has a very low frequency cutoff. It has to, otherwise PS hum gets thru to the amp. The PS filter is bidirectional. Don't want to hear noise like that in my amps.
Maybe the rectifier 'sound' gets thru but only at a frequency elephants respond to. Don't let any in the house with those rectifiers running.
Perhaps coveted for their weird appearance??
It can have an offset cycle until the heaters come up, slowly changing the output capacitor's DC standing level until settled. Turning on the main amp last or including a delayd output relay circuit can overcome that inconvenience. But not a continuously present situation. There's no reason to have that unless there is a B+ up and down periodic cycle or unsteady heating. Is the Maida steady over time in this build? What about the heaters supply, any periodic change there?
The problem is always there. I can actually see the woofers pumping in and out in very slow motion when it happens with no music going through. The Maida seems pretty stable as the measured voltage varies milli to tenths of volts. Is that stable enough? The heaters are run on a constant current source and vary 0.002volts max.
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Yes it's stable. You are looking for a cycle in sync with that pumping. In something like B+ or heaters supply. Such pumping is usual with passive B+ supplies for instance if the circuit is susceptible because they are following the AC mains ups and downs only slowly filtering without regulation.