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Old 8th April 2008, 05:54 AM   #1
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Default 6922 transformer coupled

I'm going to upgrade the analog board in my DAC by changing from capacitors coupled to transformers coupled with the below schematics. Please advise me if it is ok. I will use one 6922 tube for each channel i.e. I will parallel the 2 triodes in a 6922 tube.

Thanks a lot and regards.
Andersen
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Old 8th April 2008, 05:56 AM   #2
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Please ignore the volume control in the above schematics.

And here is the schematics of the current analog board in my DAC.
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Old 8th April 2008, 06:45 AM   #3
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Hi,

6922 has a low output impedance. You can use lower than 10K primary, no problem. You could probably go as low as 2K5:600R if you wanted to.

Cheers!
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Old 8th April 2008, 06:48 AM   #4
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Quote:
Originally posted by Geek
2K5:600R
Some Japanese R-R with funky Japan only output pentodes come with 2.5k->600 (+8) SE OPTs ... would they be suitable?

dave
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Old 8th April 2008, 06:52 AM   #5
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Quote:
Originally posted by Geek
Hi,

6922 has a low output impedance. You can use lower than 10K primary, no problem. You could probably go as low as 2K5:600R if you wanted to.

Cheers!
Thanks a lot for your advice. Actually, I have a spare pair of Tango NP-126. Therefore, the lowest primary impedance I can use is 10K. Please advise if there is any problem with it.

Thanks and regards
Andersen
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Old 8th April 2008, 07:01 AM   #6
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Quote:
Originally posted by planet10


Some Japanese R-R with funky Japan only output pentodes come with 2.5k->600 (+8) SE OPTs ... would they be suitable?

dave

certainly "funky Japan" will be good for that ;

for 2K5 use one bottle per channel , and make'm bleed ;

that way they sound so good , nothing like usual wimpy 6922 projects
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Old 8th April 2008, 07:08 AM   #7
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Quote:
Originally posted by Zen Mod



certainly "funky Japan" will be good for that ;

for 2K5 use one bottle per channel , and make'm bleed ;

that way they sound so good , nothing like usual wimpy 6922 projects
Are you recommending 2K5 primary even in the case of paralleling the 2 triodes in one 6922 tube for each channel?

Thanks and regards
Andersen
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Old 8th April 2008, 07:35 AM   #8
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Quote:
Originally posted by Andersen


Thanks a lot for your advice. Actually, I have a spare pair of Tango NP-126. Therefore, the lowest primary impedance I can use is 10K. Please advise if there is any problem with it.
It's will work fine. Lower Z means more power (higher level here) and higher distortion. With the 10K:600 transformer, you will lose amplification but get lower distortion, but if you have a preamp you'll be fine. If you need the gain, use a step up transformer between the DAC and tube -- the Lundahl LL1674 works well here.

Also, if you have enough heater current, try a 6n1P here instead.
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Old 8th April 2008, 07:43 AM   #9
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Quote:
Originally posted by dsavitsk


It's will work fine. Lower Z means more power (higher level here) and higher distortion. With the 10K:600 transformer, you will lose amplification but get lower distortion, but if you have a preamp you'll be fine. If you need the gain, use a step up transformer between the DAC and tube -- the Lundahl LL1674 works well here.

Also, if you have enough heater current, try a 6n1P here instead.
Well, yes, I have a pre-amp. Thanks a lot for your advice.
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Old 8th April 2008, 08:51 AM   #10
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Quote:
Originally posted by planet10


Some Japanese R-R with funky Japan only output pentodes come with 2.5k->600 (+8) SE OPTs ... would they be suitable?

dave
I don't see why not, unless the winding interleaves and core material lead to objectionable BW limitations or LF distortion respectively.



Quote:
Originally posted by Andersen

Therefore, the lowest primary impedance I can use is 10K. Please advise if there is any problem with it.
OK, no problem. Use what you have

Dsavitsk's advice about lower distortion/lower output is true though. I was more concerned for lower output, as the increased distortion could be moot compared to other factors in this setup.

If you intend on spending coin, colleagues have highly recomended the Lundahl LL1674 suggested.

Cheers!
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