ampage Tube Amps / Music Electronics	For current discussions, please visit Music Electronics Forum.

ampage archive

Vintage threads from the first ten years

previous: Joseph Futral I recently acquired this Alamo Elec... -- 11/18/1999 3:34 AM

Re: Alamo amp

11/18/1999 9:52 PM
Doc	Re: Alamo amp I'll try to help you with the first part of your question. The 7199 was popular for a time because the triode part was employed as a split-load phase inverter (which had a gain slightly less than unity), and the pentode part was used as a high gain voltage amplifier just ahead of it. So this one tube and a pair of 6L6s made up the entire power amp portion of the circuit. It's just another way to do it, and typical of amps from the '60s, both guitar and home audio. Other circuit designers chose to use a matched pair of triodes in a Schmitt/differential/long tail type PI, which had a higher voltage swing capability. I don't have a schematic for that Alamo, but you could take a look at the Ampeg B25 schematic over on Joe Piazza's site. That shows a similar circuit with the 7199 and a p-p pair of 7027s (big 6L6s). It should at least help you in reverse engineering your circuit to make up a diagram.

11/18/1999 9:52 PM

Doc

Re: Alamo amp

I'll try to help you with the first part of your question. The 7199 was popular for a time because the triode part was employed as a split-load phase inverter (which had a gain slightly less than unity), and the pentode part was used as a high gain voltage amplifier just ahead of it. So this one tube and a pair of 6L6s made up the entire power amp portion of the circuit. It's just another way to do it, and typical of amps from the '60s, both guitar and home audio. Other circuit designers chose to use a matched pair of triodes in a Schmitt/differential/long tail type PI, which had a higher voltage swing capability.

I don't have a schematic for that Alamo, but you could take a look at the Ampeg B25 schematic over on Joe Piazza's site. That shows a similar circuit with the 7199 and a p-p pair of 7027s (big 6L6s). It should at least help you in reverse engineering your circuit to make up a diagram.

Replies:

Joseph Futral Thanks for the 7199 info. This is p... -- 11/20/1999 5:55 PM