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Old 29th August 2011, 04:45 PM   #1
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Default 6922 pin i.d.

hello, i'm trying to mod my dac that has 6922 output. could you tell me which pin i'm suppose to wire 300ohm to as a grid stopper? and i'm suppose to rewire the output cap to the plate of the bottom tube. which pin would that be? thanks in advance.
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Old 29th August 2011, 05:18 PM   #2
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TDSL Tube data [6922]
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Old 29th August 2011, 05:39 PM   #3
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thanks but i'm such a noob that i still don't know how to read that. am i correct in assuming that 4,5 are the pins for bottom plate?
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Old 29th August 2011, 06:19 PM   #4
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Quote:
Originally Posted by PreSapian View Post
am i correct in assuming that 4,5 are the pins for bottom plate?
Not correct. The plate pins are 1 & 6. (3 & 8 cathode) (2 & 7 grid) (4 & 5 filament)
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Old 30th August 2011, 03:24 AM   #5
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can both 1 & 6 be considered as a plate of 'bottom tube'?
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Old 30th August 2011, 04:59 AM   #6
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Either one could be. But not both at the same time of course. "Bottom tube" refers to the way the schematic is drawn. You will have to figure out which applies by studying the unit's wiring along with the schematic. Hopefully you have the schematic diagram. I'm guessing that if you have a diagram, there is no pin numbers on it.
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Old 30th August 2011, 05:05 AM   #7
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Quote:
Originally Posted by PreSapian View Post
can both 1 & 6 be considered as a plate of 'bottom tube'?
No..
Triode 0 cathode 8 Grid 7 Plate 6
Triode 1 cathode 3 Grid 2 Plate 1

You should probably pick up a copy of Morgan Jones "Valve Amplifiers 3rd Edition" read it, and also read the safety and high voltage thread here.
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Old 30th August 2011, 05:32 AM   #8
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here's the diagram

Click the image to open in full size.

and this is the only description i have to go by

'I wanted to post my final mod that has left me not wanting to change anything else. First I tried the Grounded-Cathode / Cathode follower mod. Very clear and detailed and measured better than most any SS DAC. However it sounded too much like SS. So on a whim after putting the SRPP back I decided to hook the output cap to the plate of the bottom tube (instead of the cathode of the top tube.)

This increases the output impedance to 3.5 kOhms, high - but fine for amps with 50 kOhm or higher input impedance.

This mod makes the DAC-60 have the same configuration as the first stage of the Aikido. It is single ended not push pull (like the SRPP.) The sound is very natural and full of life. I used 200 ohms for the cathode/plate resistors.'

the thread of this post has been buried for years and the poster no longer around. is r1 the cathode/plate resistor he's referring to?

so for this mod, i would take the leg of the output cap to go before r1 and change it's value to 200ohm, correct?

Last edited by PreSapian; 30th August 2011 at 05:45 AM.
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Old 30th August 2011, 06:04 AM   #9
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^i'm sure that would be wrong... on my circuit the inductor and 200uf cap run into pin 2 and 3 respectably. so tying that togather, would pin 1 be the one for the bottom tube?

Last edited by PreSapian; 30th August 2011 at 06:17 AM.
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Old 30th August 2011, 06:29 AM   #10
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nope that did not work. i get no sound out of the dac and now am completely lost...
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