Yet another 12B4 line stage, or is the 12B4 better than the Grounded Grid..... - Page 13 - diyAudio
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Old 24th December 2005, 06:33 AM   #121
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Brian & "Mr. Tube"

Thanks for your insights . I'll try the CCS both above and below the tube, but not both.

Ho, Ho, Ho! And, Merry Christmas to all!
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Old 24th December 2005, 08:45 PM   #122
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it is a real must to paralel few capacitors in the cathode of the tube in the paralel of the LM317.... otherwise - no good sound... i have learned that now....
best regards and merry chritmass for everyone
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Old 26th December 2005, 09:33 PM   #123
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Here is yet another great article with design plans for what appears to be a very good tube regulator circuit. Starts off very basic and then ends up pretty darn complicated!

Link

Mark
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Old 29th December 2005, 12:21 AM   #124
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Default 300V B+

If using the Brian Beck circuit with a 300V B+ would this degrade the sound much and/or will the circuit need to be changed?

Hope some one can help.

Thanks
Martin
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Old 29th December 2005, 02:33 PM   #125
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If you're asking about dropping the B+ from 320 volts to 300 volts, then I think it will still work OK. The plate-to-cathode voltage will drop to about 100 volts, but the plate curves still look fairly linear at that point assuming line-stage voltage swing levels (2 volts rms or so). You could back down on plate current a bit by putting a larger resistor in the LM317 circuit (say, a 47 ohm value) and use the freed-up voltage to split between a larger plate load resistor and/or a larger plate voltage operating point. How much all this is audible is debatable. The point is that, within limits, this circuit is not THAT critical.
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Old 29th December 2005, 02:59 PM   #126
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Default Brian Beck

Thanks for the answer I was talking about dropping the B+ from 320V to 300V. I think I will try this circuit whenever I get all the other things that are lined up finished.

Martin
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Old 30th December 2005, 03:52 AM   #127
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Hi,

A 300VDC PSU you said?

Here you go:

Cheers,
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File Type: gif psu_300v_supply.gif (9.4 KB, 1931 views)
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Old 30th December 2005, 06:09 PM   #128
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Quote:
Originally posted by fdegrove
Hi,

A 300VDC PSU you said?

Here you go:

Cheers,
Quite fun it was actually this PSU I wanted to try at some time as I also would like to try your 12bh7a circuit with it. Though I wanted to be able to try the 12b4a aswell as I am not sure if I can live without the gain, but only a test will show me that.

Martin
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Old 30th December 2005, 08:48 PM   #129
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hi guys----happy new year first of all -

i would like that somebody here explains nice and easy what will happen if i accidently pull out the 12b4 while preamp and amplifier are working......

also - another thing.....
i have made my 12b4 preamp with 26mA and 130V on the anode of the tube... i have 4k7 resistor in the plate.... this is not quite the line stage from our Brian but it is working nice... also i have got no strange treble i was having problems with (before i have paraleled the cathode capacitor with the smaller one MCap-Mundorf 1uF/400V).... - - - - BUT - - - , i have perceived big humming when the preamplifier is turning on... this humming is gone after arround 20 seconds..... what is happening.... probably the tubes but i am not sure and this is not comfortable to listen to when i turn the preamplifier on....
best regards and have fun during new years evening......
sunny
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Old 30th December 2005, 09:14 PM   #130
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Hi,

Quote:
i would like that somebody here explains nice and easy what will happen if i accidently pull out the 12b4 while preamp and amplifier are working......
Nice and easy, he?

I don't think I'd call "accidentally" pulling a tube with the gear up and running errrrr........An accident.
Apart from some noise nothing much will happen but I'd advise seeing some kind of doctor if you have habits like that.............

Quote:
i have perceived big humming when the preamplifier is turning on... this humming is gone after arround 20 seconds..... what is happening....
Mute switch ring a bell?

Maybe you heard about tubes needing a little time to warm up? Like about twenty seconds perhaps?

Sunrise, maybe you should put that Tequila bottle back where you found it........

Ciao,
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