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Old 15th September 2003, 12:29 AM   #11
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It has been brought to my attention that there is a similar schematic here in a post that uses a 12sn7 tube with a 300v B+ supply. I would like to use a similar schematic and adapt it to the 5692 tube only since it is more delicate that the 6SN7 is.

I would like a 250 volt B+ maximum I believe. I think that is the limit on the 5692 or close to it. I would like some help with the other values involved. As Frank was good to point out I have several missing R values and several C values that are incorrect.

Frank

I assume that R7 might be around 47K and C2 might be better at 1mfd. I think that R6 and R4 would have to be refigured also.

I will need to drive the 100K input of my Quicksilvers. I'm starting to believe what I was told months ago about not needing much gain.

Joe
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Old 15th September 2003, 09:59 AM   #12
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Hi,

Quote:
I assume that R7 might be around 47K and C2 might be better at 1mfd. I think that R6 and R4 would have to be refigured also.
Here's what I came up with this morning...

Let's hope I didn't make any mistakes:

Cheers,
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Old 15th September 2003, 10:46 AM   #13
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Frank

Wouldn't pushing 7.15mA out of the tube be at the limits for this tube?

I don't have the electrical data for this tube that is why the question.



Joe
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Old 15th September 2003, 10:53 AM   #14
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Hi,

Quote:
Wouldn't pushing 7.15mA out of the tube be at the limits for this tube?
Max. cathode current is given at 15mA so that should be safe.

Quote:
I don't have the electrical data for this tube that is why the question.
I'll e-mail the datasheet of the Red Octobers if the file isn't too big.

Cheers,

EDIT: The file seems to have passed O.K.
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Old 15th September 2003, 11:10 AM   #15
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This schematic is suppossed to work with a 6SN7 as well?? I have a bl**dy hell lot of them...5687s as well...a friend in the states sent them over...and a couple of USAF 6888s...wonder if there is any use for em...
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Old 15th September 2003, 11:31 AM   #16
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Hi,

Quote:
This schematic is suppossed to work with a 6SN7 as well??
Absolutely.

Quote:
and a couple of USAF 6888s...wonder if there is any use for em...
Those are computer penthodes.PA max. 8W...
Could probably be used for audio and related circuits.

Cheers,
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Old 15th September 2003, 11:38 AM   #17
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Frank

Any rough guess as to the output voltage?



Joe
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Old 15th September 2003, 11:50 AM   #18
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Hi,

Quote:
Any rough guess as to the output voltage?
A rough guess would be about 8V/9V out for 1V in.

I deliberately didn't optimise it for gain since you'll be throwing it away most of the time anyway.

If you need more gain, decouple the first cathode R with a good quality cap and live with the colourations...

Do you need a PSU to go with it?

Cheers,
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Old 15th September 2003, 11:20 PM   #19
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Default Franks 5692 line amp

Hi Frank

Thanks for the help. With regard to gain... I have finally become a believer. Mega gain isn't needed in a line amp.

With respect to the power supply... I was going to use a 5Y3, a 370-0-370 transformer, 2) 50 mfd capacitors, 2) 30H chokes@ 40mA 595 ohm and a VR150 and VR90.

I would value your opinion on the usage of the above. I'm kinda stuck on the chokes and regulator tubes now. Its the same supply I am using on the 5687 line amp I have so I assume its beefy enough for the 5692's.

If you would like to help here please go for it.

Thanks
Joe
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Old 16th September 2003, 12:08 AM   #20
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Hi,

Quote:
Mega gain isn't needed in a line amp.
And you'll still have ample gain to burn...wich will give you lots of dynamics either way of the scale...

Quote:
With respect to the power supply... I was going to use a 5Y3, a 370-0-370 transformer, 2) 50 mfd capacitors, 2) 30H chokes@ 40mA 595 ohm and a VR150 and VR90.
Use a tube rectifier if you like but with the advent of the Cree Sics diodes I tend to prefer those, money no object.
Granted the tube rectifier + choke may still win sonically but probably not economically. (Who cares?)

Provided you make this a dual mono PS, I'm confident it has everything to be a world-class pre.

You can still adopt chokes in the PS, I like them there; they make for good isolation between stages but here's the everyman's PS:

The P.S. can be redrawn for choke use, hey, you need to get rid of them 150H Hammonds, right?

Cheers,
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