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September 24, 2020, 11:35:28 PM

Author Topic: Change 6922 to 5670  (Read 1205 times)

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Offline galyons

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Change 6922 to 5670
« on: March 08, 2017, 06:19:58 AM »
I have a Seduction Tape amp that is redundant, long ago replaced with an Eros Tape.  I want to put it back in service for phono.  Since I will making circuit changes, I am considering replacing the 6922's with 5670's.  Although many folks consider just changing the base pinouts, would there be benefit in changing the cathode resistor? If so, recommended value?  Any other changes?

Cheers,
Geary
VPI TNT IV/JMW12.7i/FR1 MkII Soundsmith retip >Eros TH+ Otari MX5050 IIIB2 > Eros + ANK Dac2.1 > BeePre >Paramount 300B 7N7 > EV Sentry IV-A

Crack 7N7 > Sennheiser HD650 & AKG K240 Sextetts

Thorens TD124/Ortofon RMG-212/SPU >Seduction > Smash^Up> Paramour 45 MQ >K12's

Offline Paul Birkeland

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Re: Change 6922 to 5670
« Reply #1 on: March 08, 2017, 12:33:45 PM »
The 5670 has about half the transconductance that the 6922 has.  While this allows the 5670 to operate at higher plate voltages than a 6922, it also makes it more noisy, and therefore not a particularly suitable choice of tube for a Seduction, especially considering how inexpensive some 6922's can be!
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline galyons

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Re: Change 6922 to 5670
« Reply #2 on: March 08, 2017, 03:16:59 PM »
Thanks PB!  I will leave the 6922's.  I thought that the 5670 might be a bit quieter, based only on the net chatter.  I like the 6922/7308's in phono, so that just makes the repurposing easier!!

Cheers,
Geary
VPI TNT IV/JMW12.7i/FR1 MkII Soundsmith retip >Eros TH+ Otari MX5050 IIIB2 > Eros + ANK Dac2.1 > BeePre >Paramount 300B 7N7 > EV Sentry IV-A

Crack 7N7 > Sennheiser HD650 & AKG K240 Sextetts

Thorens TD124/Ortofon RMG-212/SPU >Seduction > Smash^Up> Paramour 45 MQ >K12's

Offline Paul Birkeland

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Re: Change 6922 to 5670
« Reply #3 on: March 09, 2017, 09:16:04 AM »
You could scratch build a phono stage and use several 5670's in parallel, then you'd get them quieter.  This, of course, would require something a bit more complicated than what the Seduction has for power supplies, but it's certainly possible.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man