merlin: If you have 2x tubes with both sections of approx 7.5mA then, its simple 4x7.5mA + 20mA (always just add 20mA up to 25mA if you want to be on the safe side), which means 50-55mA total current on the SSHV.
This is without calculating the actuall current of the first tube, but anyway you probably have those calculations yourself - else you can just put a current meter before the tubes to measure actual current yourself.
This is without calculating the actuall current of the first tube, but anyway you probably have those calculations yourself - else you can just put a current meter before the tubes to measure actual current yourself.
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Measure over 47k on the first CC tubehalf, use ohms law, measure over 10k on the CF tubehalf, us ohms law. Add them and multiply with the number of channels. Add 20 mA. Done.
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between the first and second triode . use one section per stage per channel and elevate the heater on the first stage and adjust the voltages to produce the bias of the second stage .
It is about skipping the coupling cap between T1s anode and T2s grid and let T2 self bias.
If filament elevation is necessary it should be done on the tube that holds the CF stereo pair for T2.
Sorry left out part of it elevate first section heater to cathode voltage plus 45 volts and second section cathode voltage plus 45 volts . RCA teck manual spec for reduced noise it does help . Need for grid stop resistor on the cathode follower does help but is not always needed. If self biasing first cap after volume control can be removed and lower the resistor from 1M to 100k to 470k . Some thing like this . http://upload.wikimedia.org/wikiped...-Cathode_follower_constant_current_1000px.png
Yes. That circuit has one flaw though that can be interveined. The grid and cathode of T2 can arc at startup due to high voltage differences. I killed a ECC81 recently like that. SY solves this with a neon bulb.
http://www.diyaudio.com/forums/diya...oise-thoroughly-modern-tube-phono-preamp.html Figure 5: Signal Circuitry and text below.
http://www.diyaudio.com/forums/diya...oise-thoroughly-modern-tube-phono-preamp.html Figure 5: Signal Circuitry and text below.
I've recently finished breadboarding a phono stage tube circuit (the muscovite mini II here at diyaudio) for which I'm using the SSHV2. The signal circuit isn't conducting (not much anyway) so the plate voltage ends up close to the same as my B+, which is 300v. The SSHV2 was working fine, with current and voltage adjustable. Since tubes weren't conducting, I didn't leave the power on for very long - just enough to ensure the tube heaters were able to turn on conduction.
Then I tried it again last night to do more testing, only this time I got a faint "pop" right away and the red LED went out, no voltage at the output.
I've checked the LED and it works fine. I did the low v checks per our earlier conversation and the ccs seems to work fine. (short F+ to F0, disconnect S+ and S0, attach 9v and measure TP while varying R4). Current varies nicely. DN2540s measure about 2v as they should. But Q5 measures <1R between e and b and virtually no voltage when under the low v test. Q4 measures 1.4M or so between e and b and about 0.1 or 0.2v under low v test. I assume Q5 is shot and will replace it. But is there a way to check Q6 in-circuit? Is it likely to also be fried? It's not an easy part to find so I'm hoping not to have to replace it. But I will if need be.
Thanks!
Then I tried it again last night to do more testing, only this time I got a faint "pop" right away and the red LED went out, no voltage at the output.
I've checked the LED and it works fine. I did the low v checks per our earlier conversation and the ccs seems to work fine. (short F+ to F0, disconnect S+ and S0, attach 9v and measure TP while varying R4). Current varies nicely. DN2540s measure about 2v as they should. But Q5 measures <1R between e and b and virtually no voltage when under the low v test. Q4 measures 1.4M or so between e and b and about 0.1 or 0.2v under low v test. I assume Q5 is shot and will replace it. But is there a way to check Q6 in-circuit? Is it likely to also be fried? It's not an easy part to find so I'm hoping not to have to replace it. But I will if need be.Thanks!
Thanks, Salas!
Another question. On the Muscovite Mini II, the heater supply is supposed to float, using a voltage divider between the + and - legs tied to the signal ground. That's how I understood it. If I do this, the signal ground ties back to the SSHV2 at F0/S0, and the SSHV2 builds to just under my target B+, then drops to under 200v over a minute or two. I didn't let it stabilize as the heater circuit regulator LT1084 was getting hot. The heater schematic and discussion are at post 85 and 87 of the muscovite mini thread (http://www.diyaudio.com/forums/anal...-mini-6-9-6z9p-phono-stage-9.html#post3840116).
Another question. On the Muscovite Mini II, the heater supply is supposed to float, using a voltage divider between the + and - legs tied to the signal ground. That's how I understood it. If I do this, the signal ground ties back to the SSHV2 at F0/S0, and the SSHV2 builds to just under my target B+, then drops to under 200v over a minute or two. I didn't let it stabilize as the heater circuit regulator LT1084 was getting hot. The heater schematic and discussion are at post 85 and 87 of the muscovite mini thread (http://www.diyaudio.com/forums/anal...-mini-6-9-6z9p-phono-stage-9.html#post3840116).
Thanks. The heater floating reference was designed to be tied to signal ground using the original tube-based PS for the muscovite mini. That PS was beyond my abilities and finances and Kevin suggested I consider the SSHV2 as an alternative. I'll ask him if there's another way to accomplish the floating reference that doesn't interfere with the SSHV2 and doesn't put the heater beyond it's rating (k-h = +90, -180, tying to 320-350v would put it well beyond 180v above the cathode). I agree it does seem odd that it could have any effect, tied at one (ground) point, but clearly something dramatic was happening to the B+ that DIDN'T happen when the heater was NOT referenced to the signal ground. I tried it twice and the falling B+ happened both times. Note the failure of Q5 occurred AFTER I disconnected the heater reference and powered on again.