I've been thinking, what's the difference between a differential pair and common cathode sigle ended circuit + shunt regulator?
Ultimately, the current flows in them form a seesaw - one high/the other low, don't they?
I only followed this thread loosely. Sorry if that would've been brought up.
Ultimately, the current flows in them form a seesaw - one high/the other low, don't they?
I only followed this thread loosely. Sorry if that would've been brought up.
When I had made that build I had not developed the HVSS yet. It will normally be recommended over the Maida. It takes a 400V driver PNP for over 300V that we need here.
http://www.diyaudio.com/forums/powe...stic-mosfet-hv-shunt-regs-50.html#post1909446
I always do this. In the Mœbius heater supply I use a 4.7μF NP electrolytic across the circuit before any dropping resistors, In the Machine supply (with its greater draw and thus lower effective Z), a 10μF. The sonic result is that any residual hum from cathode coupling is now a very soft, rounded sound, with little or no 'buzz' left in it, and so much less conspicuous at any level. I try to keep Xc of the capacitor at least 50 times that of the heater circuit at 60Hz, to make sure the blue smoke stays in the cap.
Aloha,
Poinz
AudioTropic
Thanks for the input....I can see your design has transcended time and this is a good thing for anybody into this hobby.
Someone said that 6v6 round plate tubes sounded better, is this something you agree with?
I let everyone know about my ramblings and sparkles I’m about to produce with my unsteady pulse.
Someone said that 6v6 round plate tubes sounded better, is this something you agree with?
I let everyone know about my ramblings and sparkles I’m about to produce with my unsteady pulse.
Such anecdotal info comes from using 6V6s in power amplifiers. In our case you would need the quieter ones. This is weird what we do here, using a power tube for a line preamp, changes things. The Tungsol 6V6GT (Russian made reissue) proved both good for vibrations and sonics IMO. Suspend or soft rubber decouple the tubes on a small sub chassis, it pays off. If you have enough gain for your amp in the chain, utilize the bootstrapped cathode follower, much less susceptible to vibrations or for heaters & anodes heating up noises.
P.S. Here are some check points for you as for DC bias. Having measured it with enough 6V6GT I can say that the LT Spice model kindly provided by Robert McLean absolutely complies for bias and gain. Most tubes measure ''well near there'', some are spot on. R1 is substituted by the volume pot in the real preamp of course.
Attachments
~200 Ohm. Teflon 0.1uF/200V input capacitor is highly recommended. Even 0.022uF will work due to the extra high input impedance of the bootstrap (post#144).
The bootstrapped CF offers one other benefit.
There is a DC bias across the input coupling cap which means that the dielectric stress is never reversed (with audio signal) and therefore there is no hystersis to worry about. That means that the performance of any good polypropylene cap will equal that of a Teflon or (sweeping generalization) any other piece of audio jewellery cap.
Cheers,
Ian
There is a DC bias across the input coupling cap which means that the dielectric stress is never reversed (with audio signal) and therefore there is no hystersis to worry about. That means that the performance of any good polypropylene cap will equal that of a Teflon or (sweeping generalization) any other piece of audio jewellery cap.
Cheers,
Ian
Hello Salas.
Do you think that your preamp will work properly with these tubes:
6P14P, 6P14P-V, 6P14P-EV
These are russian equivalents of el84 which is very similar to 6v6 (like I heard).
Do you think that your preamp will work properly with these tubes:
6P14P, 6P14P-V, 6P14P-EV
These are russian equivalents of el84 which is very similar to 6v6 (like I heard).
Was looking thru the thread and didn't see this mentioned...
Has anyone tried a string of LED's to get cathode bias voltage? (Like SY's Red Light District amp.) Five white LED's all in a row should get 15V or very close. Only a few ohms effective resistance. That would get the cathode bypass cap out of the circuit.
Or maybe a zener string? (High wattage zeners needed.) I calculate less than a half of a watt dissipated across cathode load (15V * 0.025A = 0.375W).
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Has anyone tried a string of LED's to get cathode bias voltage? (Like SY's Red Light District amp.) Five white LED's all in a row should get 15V or very close. Only a few ohms effective resistance. That would get the cathode bypass cap out of the circuit.
Or maybe a zener string? (High wattage zeners needed.) I calculate less than a half of a watt dissipated across cathode load (15V * 0.025A = 0.375W).
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Did try on different preamps (12B4 & 6SN7). But I preferred the classic R//C tone, so I did not try again in this one. An easy and maybe worthwhile test for those who will make this pre non the less. Its a system synergy and preference area the tone thing should we not forget. Same goes for the tubes brand choice, output cap choice, etc.
P.S. Don't know about white LEDS, but red, green, yellow, IR, are surely the low noise ones.
P.S. Don't know about white LEDS, but red, green, yellow, IR, are surely the low noise ones.