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previous: nic maybe the design is like a Magnaton... -- 9/5/1999 4:51 PM

Re: Weirdest amp yet?

9/6/1999 12:01 AM
Farrow	Re: Weirdest amp yet? Nooooo.... Upon closer inspection, the amp is definitely NOT Magnatone. But here's what I figured out so far... Stereo power amps - 2 separate OTs. One's big for better LF response (Super Rev. size) and the other's small (Deluxe-sized.) Each set of 7591s has a different fixed bias (one set at -22, the other at -25.) Ext. speaker jack disconnects internal 8" speaker. "Bass" power amp fed from middle leg of bass control pot from CH1 preamp and also from volume pot of CH2. "Treble" power amp fed from reverb return, vol. pot of CH2 and treble pot of CH1. Tube reverb (capacitor coupled) uses the pentode half of a 6GH8 to drive the pan and a transistor for return. True Vibrato uses 4 transistors and a 2-LDR arrangement for pitch-shifitng effect. Reverb and Vibrato only amplified by "Treble" channel. 2 input channels, "Ultraflex" and "Normal" Each uses 1-7025. "Normal" sends signal to both power amps and is mono, 1-vol, 1-tone. "Ultraflex" has 'verb and vibrato as well as Treble and Bass controls. "Dual Input" jack is switchable between CH1 and CH2. Here's what I've done to it -- replaced lousy speakers with a 12" EVM and the 8" out of a Vox Pathifnder reissue. Removed 2-47uf caps from across the output of the "Bass" OT. Removed 4700pf treble roll-off cap from the input to the "Bass" PI. CH1 sounds like an Ampeg and CH2 sounds like AC/DC. Pretty cool amp - Except one thing, it's bigger than a Twin! BUT it beats lugging 2 amps, which is what I do now (Ampeg Reverborocket and Fender Pro-Jr.) Farrow http://surf.to/pharaohamps PS Bill, I'm so busy working up for my 2nd build of 'Cheetahs that I haven't had time to work on the Fire box project. Plus I don't need anywhere near that many tubes. Thank you, I'll be in touch!

9/6/1999 12:01 AM

Farrow

Re: Weirdest amp yet?

Nooooo.... Upon closer inspection, the amp is definitely NOT Magnatone. But here's what I figured out so far...

Stereo power amps - 2 separate OTs. One's big for better LF response (Super Rev. size) and the other's small (Deluxe-sized.) Each set of 7591s has a different fixed bias (one set at -22, the other at -25.) Ext. speaker jack disconnects internal 8" speaker. "Bass" power amp fed from middle leg of bass control pot from CH1 preamp and also from volume pot of CH2. "Treble" power amp fed from reverb return, vol. pot of CH2 and treble pot of CH1.

Tube reverb (capacitor coupled) uses the pentode half of a 6GH8 to drive the pan and a transistor for return.

True Vibrato uses 4 transistors and a 2-LDR arrangement for pitch-shifitng effect. Reverb and Vibrato only amplified by "Treble" channel.

2 input channels, "Ultraflex" and "Normal" Each uses 1-7025. "Normal" sends signal to both power amps and is mono, 1-vol, 1-tone. "Ultraflex" has 'verb and vibrato as well as Treble and Bass controls. "Dual Input" jack is switchable between CH1 and CH2.

Here's what I've done to it -- replaced lousy speakers with a 12" EVM and the 8" out of a Vox Pathifnder reissue. Removed 2-47uf caps from across the output of the "Bass" OT. Removed 4700pf treble roll-off cap from the input to the "Bass" PI.

CH1 sounds like an Ampeg and CH2 sounds like AC/DC. Pretty cool amp - Except one thing, it's bigger than a Twin!

BUT it beats lugging 2 amps, which is what I do now (Ampeg Reverborocket and Fender Pro-Jr.)

Farrow

http://surf.to/pharaohamps

PS Bill, I'm so busy working up for my 2nd build of 'Cheetahs that I haven't had time to work on the Fire box project. Plus I don't need anywhere near that many tubes. Thank you, I'll be in touch!