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In Reply to: RE: Thanks, and one clarification question posted by JoshT on March 16, 2023 at 07:29:25
...but that's only because this ST-70 with the VTA driver board is one of my back-up amps, and only sees occasional use. If it were my main, best sounding amp, I'd opt for the octal board over the noval.
Regarding tube adapters in general, Jim McShane told me that they can sometimes cause somewhat diminished highs, depending on the particular tube and circuit. I didn't notice that in my system. but eliminating them with the proper octal socket(s) for the 6SN7(s) would really be the best way to go.
Follow Ups:
I bought one based on a link from Roy and received an email from the seller - screen shot below.
Is this just a generic warning about putting a 6 volt tube in a 12 volt tube socket? I assume it would be a concern if I were replacing all three tubes but isn't where I'm just replacing the center tube?
Thanks for your input on this.
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"If you are the owner of a new stereophonic system, this record will play with even more brilliant true-to-life fidelity. In short, you can purchase this record with no fear of its becoming obsolete in the future."
All tube filaments in a Dynaco ST-70 (including the VTA version) use 6.3 VAC, other than the 5AR4 rectifier. So the 6.3 V adapter is the one you want, even if you were adapting all three driver tubes.
I'm going to assume that you have a continuity function on the meter you use to check tube bias. If so, above is a crosscheck I came up with from the data sheets of the two tubes, to be certain that the adapter is wired correctly before you use it in your amp. I wasn't willing to leave the adapter to "It's probably OK", and it only took a minute to test.
The column on the left are the 12AU7 pins, and on the right are the corresponding 6SN7 sockets.
Good luck with it, and I strongly suspect you'll soon be a member of the 90% Club (who prefer the 6SN7 over the 12AU7 in the VTA). Please keep us posted.
Now to order a tube, most likely from Jim, Brent or the Tube Depot. Or an Inmate, lol. I've had good luck in the past with all four sources. :-)
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"If you are the owner of a new stereophonic system, this record will play with even more brilliant true-to-life fidelity. In short, you can purchase this record with no fear of its becoming obsolete in the future."
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