Bottlehead Forum

Bottlehead Kits => Stereomour II => Topic started by: gstitt on November 27, 2016, 07:33:58 AM

Title: 12AY7
Post by: gstitt on November 27, 2016, 07:33:58 AM

Will a 12AY7(6072) work as a substitute for the 12AT7 in the Stereomour II? I know it has less gain.

Title: Re: 12AY7
Post by: Paul Joppa on November 27, 2016, 11:36:49 AM

It might. The plate voltage for a nominal-spec tube will be a bit higher - you can check, it should be in the range of 170 to 230 volts. There is a chance that the increased source impedance at the plates will compromise the highest treble a bit. The effect would be difficult to measure; hard to say without listening.

A small decrease in the 365-ohm bias resistance would probably correct the excess high voltage, if any.

Title: Re: 12AY7
Post by: gstitt on November 27, 2016, 02:07:54 PM

Thanks Paul. I will check on the specs.

Title: Re: 12AY7
Post by: Paul Joppa on November 27, 2016, 03:50:49 PM

I thought about it some more, and if you don't have the shunt reg upgrade, you don't need to worry about high driver plate voltage. It should be good up to 275 volts.

(The SR upgrade regulates to 300v, so you need at least 70v of swing, hence the 230v maximum in that case.)

Title: Re: 12AY7
Post by: gstitt on November 28, 2016, 04:18:41 PM

Thanks again Paul. I'll probably stick with my 12AT7's, as I'm pretty sure I won't be able to resist the SR upgrade  ;D