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Old 4th March 2004, 01:01 PM   #11
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trancy, I forgot

You have to put the volume pot in front of it,
obviously.

reference curves at

http://www.audiomatica.com/tubes/6dj8.htm

Federico
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Old 4th March 2004, 02:45 PM   #12
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Quote:
Originally posted by fscarpa58
JojoD

what is the input resistance of the amplifier?
( I am supposing that this is a preamplifer
which will drive an amplifier)

ciao
Federico

My Leach amp input resistance is 20K ohms. I would like to use a 100K pot but 50K, 250K, 500K are also available. My tubes are 6N1P. Available B+ is 150V @ 100mA regulated.

Please, Thanks!
JojoD
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Old 5th March 2004, 08:04 AM   #13
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JojoD

B+ 150 V is very low for the 6N1P.
However, I'll try something.

see you later

Federico

P.S. I wiil use the duncan model. If you prefer
something different send it to me.
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Old 5th March 2004, 11:13 AM   #14
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Quote:
Originally posted by fscarpa58
JojoD

B+ 150 V is very low for the 6N1P.
However, I'll try something.

see you later

Federico

P.S. I wiil use the duncan model. If you prefer
something different send it to me.

Federico,

That is the psu I already have setup, duncan model is fine with me. I would love a unity gain but if not possible, your smallest gain design would be fine.

Thank you very much!

JojoD

P.S. Already have ceramic tube sockets, will look for suitable aluminum casing tomorrow. Will be waiting...
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Old 5th March 2004, 11:45 AM   #15
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Excuse me, jojod

but if you want a unit gain cir then
schematic in post #6 is not good.
you need a simple CF.

Federico
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Old 5th March 2004, 12:04 PM   #16
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However

this has about 25 db of gain.

I really do not like it.
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Old 5th March 2004, 12:05 PM   #17
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this has a gain of -0.5 db (about 0.95)

and, in my opinion, it is better
( if you don't need gain)

bye
federico
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Old 5th March 2004, 12:28 PM   #18
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however

if you can have your supply to float,
I strongly recommend the following.
better PSRR, smaller caps.

bye
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Old 5th March 2004, 01:37 PM   #19
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Federico,

First of all, thank you very much for your time!

May I ask why you don't like the one with a 25db gain? I ask because I am really interested in that topology. BTW, those resistors are 2W right?

Regards,
JojoD
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Old 5th March 2004, 01:55 PM   #20
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2W for 20k e 30k res

for the other ( 200, 1meg, 270k) also 0.2 W.

I like the topology very much but, in this case,
and with 6N1P, we need 300 V to have it working properly.

Owing to the constrain due to the rigid connection
between plate of 1th tube and grid of the 2nd, the working
point is not very good, that is high distortion
( 0.4% at 5Vrms out) and not very great max swing.

However it works and maybe you will like its
sound.


If you don't need gain the CF is advisable.

Federico
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