Tube Amp Archive

I think there would be too much gain hitting the stock S.O.B. phase inverter for it to even work without adding those extra 220K resistors in parallel with the master volume pot to ground. Adding the stock Mark 1 phase inverter to the S.O.B. shouldn't be an issue at all as long as you add the negati...

From what I recall in an interview that Earnie Bailey did, he said that he found an old toasted Marshall amp in a dumpster and got a hold of a Fender Dual Showman schematic and a JCM800 schematic to create a hybrid clean amp that sounded like a tube version of the Roland Jazz Chorus. I would assume ...

Just in case anyone comes across this with a similar issue, sometimes it's a damaged reverb transformer and cathode circuit that has gone bad if someone tried to use a 12AU7 driver in place of the 12AT7 or a 12AT7 failed at some point causing damage. In some cases the voltage that hits the plates of...

Hey guys, just thought I'd share this fun project with anyone who is interested in modding their Mesa S.O.B. 60 into the Boogie Mark 1 to get those Weezer Blue Album tones. A buddy of mine brought this Son of the Original Boogie head in and we got it sounding awesome. The Sprague 715P caps need to b...

Xenrelic, Thanks for posting that. Billy Howerdel has killer tone. So, no feedback resistor? Just the capacitive divider 1n->10n/4k7? Do you know if this is on the 4R tap, as shown? Thanks. No feedback resistor, just the 10k/4.7nF to GND with the 1nF straight to the speaker jack tip. It's not conne...

The Naked MK1 amp is different from the long form schematic posted here. I'm assuming that is a schematic of a variant of the OD channel that someone made up. These are the specs you need to change for MK1. Power filtering: C1 & C22 16uF 500v Preamp: Add .01uF from ground of input to chassis Delete ...

Posted some updates to the schematic in the original post attachment if anyone wants the latest schematic of the Vibroverb Dumble Hybrid.

Here's a different version of the mod that was applied to a similar Fender Red Knob Dual Showman Reverb Head. It's a bit less involved and for people that don't want to mod their clean channel, because they're pretty happy with it. I'd say this mod is more for people who like the stock clean channel...

You will always have pop when switching cathode resistors, one for another with a mechanical switch. You should try the J175 P-Channel switch as they work great for silent cathode resistor and capacitor switching, when you have the larger value cathode resistor always in circuit and switching in ano...

Yep, that was a typo. C305 for the series screen supply filter was supposed to be C306. It was difficult to read from the schematic I was using. I fixed the O.P. above to reflect that change.

Here's the Triad R-2C power transformer spec sheet with dimensions for the Dumblelator.

Thought I'd share some excellent sounding mods for the Fender 'The Twin' Red Knob Combo. The amp stands up to high dollar boutique amps after the following mods. - Power Supply Section: Bias supply filter C303 = 100uF 100v F&T C304 = 100uF 100v F&T C305 = 100uF 100v F&T C202 = 100uf 100v F&T Series ...

Here ya go.

Here's a '63 Vibroverb Reissue with some Dumble Hybrid modifications. For those that love the AB763 style circuit with the clean channel capability of the ODS. This amp sounds amazing with the mods! The normal channel is set up with a little extra drive for nice pushed singing driven tones. Feel fre...

Here's one: http://www.ebay.com/itm/Vintage-CTS-USA ... 2c7dfff1f1