In The Dark

Andy Alford · Post by **Andy Alford** » 2 Mar 2003 7:00 am

I have a Supro Valco tube amp that I do not understand.The tubes are two 6v6s,6sc7,6sq7 aND A 5Y3gt.The right section contains all metal tubes.I know the 6v6s are the power tubes and the 5y3 is a rectifier but where are the preamp tubes?The amp has a real good sound but its beyond me.Can you explain the amp to me.Are there any tubes that I can change or will it have to go to the shop everytime to have the current set?

Andy Alford · Post by **Andy Alford** » 2 Mar 2003 9:54 am

Karlis Abolins · Post by **Karlis Abolins** » 2 Mar 2003 2:35 pm

Andy, The 6sc7 was used as a preamp tube in the "early" Fenders. Princeton, Deluxe, twin all used trhe 6sc7. I couldn't find a link to the 6sq7 but I assume it is similar to the 6sc7. Both tubes are available from Antique Electronics supply http://www.tubesandmore.com/
and probably elsewhere as well.

Karlis

Donny Hinson · Post by **Donny Hinson** » 2 Mar 2003 5:06 pm

Andy, as Karlis stated, the 6SC7 was a preamp tube...a dual triode, kind of an octal base version of the 12AX7. The 6SQ7 is a diode-triode combination, usually found in radio and TV sets, with the triode as used as an amplifier and the diode acting as a detector. (Since there's litle use for diodes in a musical amplifier, those two pins just wouldn't be used.) The miniature (all glass) 9-pin and 7-pin tubes didn't get real popular until the '50s.