Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: adamG on December 30, 2015, 03:40:44 am
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Hi Guys,
I'd like to ask you for your assistance?
Silly question, I think of D'Lite build with russian tubes 6P1P on output stage.
6P1P is 6V6 equivalent contained in EL84 bulb. It's a good quality tube ,easly available in my place.
Iam not sure about voltage of power supply that I assume approx. 350VDC as power tubes plates' voltage ,not to overload/overheat them. Their maximum plate voltage is approx.280VDC.
What is your opinion about my project?
Iam not an electronic engineer ,so could you assist me with the proper selection of power supply resistors?
Thank you in advance.
Regards,
Adam
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Your challenge is going to be getting high enough voltages on the preamp tubes with low enough voltages on the power tubes.
The way I would approach that if I were using power tubes with 250v max rating would be to use a VVR. I would probably lower the voltages on the power tubes only.
http://el34world.com/Forum/index.php?topic=6899.0 (http://el34world.com/Forum/index.php?topic=6899.0)
In ARCHIVES, we have quite a bit of information about VVR's in cathode biased amps. Dana Hall makes a VVR that is quite affordable and I found it very easy to install. http://hallamplification.com/main.html?src=%2F#2,2 (http://hallamplification.com/main.html?src=%2F#2,2)
Since this isn't a purist D'Lite design, ............... you can consider making the D'Lite a cathode biased version. My Tweed BluezMeister (which is similar to a D'Lite) is cathode biased. My D'Mars is cathode biased also.
I also would recommend lowering the post LTPI coupling caps from .1 to .047 on your amp.
Hope that helps? With respect, Tubenit
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Boss,
Thank you!
That seems to be the best and most clever solution;)
I'll go this path.
Actually, I was going to provide VVR mod in the past, but always setting aside for some future build with no time limitation. But now, It is such moment.
Once again, big thanks Tubenit!
Recently, I've almost finished D'Lite 44. I think I'll share photos of it ,soon...
Best regards,
Adam
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6P1P is 6V6 guts on 9-pin base and the official specs say 250V maximum.
6V6 has a suggested condition for 250V, use that.
Your 325VAC power supply will make 455V. That's way more than you want, and a lot to waste-off.
I would look for a 210V-220V power transformer. This will give 300V DC. With cathode-bias (no reason to go fix-bias at only 250V) and other lost voltage, the tubes will be not far up from 250V, and I really think the sheet spec is conservative. (Also 6P1P are low-price, life is not critical.)
300V raw supply will be ample for any preamp and driver you would use with a 250V (even 280V) power section.