The Amp Garage

Raising this post from the dead I know , but is there a way to get this turret board layout once again since the link in the first "page" is dead ? Hey, it’s been close to 15 years since I even thought about this amp. I’ll look through my old folders and see what I can do. I don’t believe I made an...

Joe B says the original Tweedle Dee’s he had come into contact with were “a bit gainy” for his taste, so yea maybe. Could be some circuit mods and/or a different speaker. Then there’s the other two-thirds of the equation, the guitar and the player,,, Tweedle Dee plans here always show a 12AX7 first...

Hey all. Chris Fantana at Rift Amps got hacked on YouTube and his entire channel was wiped out. I have no personal connection to the guy, but I’ve always enjoyed my daily dose of his videos about amp servicing and his own line of amplifiers. Whether you’re an amp nerd or just generally curious about...

I've worked on a few of these, I would say "bedroom amp" if you happen to sleep in an army barracks. :D I'd hold off on replacing tubes until you see how it works. I just finished repairing an 88-year old car radio, which all 6 tubes were original Philco from 1936 or 1937. Every single tube was sti...

Hi all, I recently picked up an early Mesa Blue Angel combo (4×10), with a three-digit serial number. As far as I can tell, this is one of the first production units. The amp is roughly 30 years old and, according to the previous owner’s family, has never been serviced. It spent the last 10+ years i...

Thank you, Martin.

Legend

I went with 10k pot with 4k7 + 2k7 in series. With a pair of STR440 grey rank I get the ranges in 43% - 88% on 50w settings. On the 25w it runs a way cooler. Really happy with the amp, and grateful for the advice.

Stock is 22k1//33k2 = 13k27 For reference I'd guess a reasonable range might be half to twice the stock value, 6k6 to 26k5. A 6k6 and a 10k pot might be good choices. Using a 25k pot, you might make the fixed resistor a 4k7 to get a range of 4k7 to 29k7. Thank you. I have both the 10k and 25k (mode...

Hi,

After having success adding the bias mod to a Fillmore, I’ve decided to do the same modification on my Express 5:50+. The bias supply is similar in topology, but the component values are different.
Could you offer some guidance on an appropriate value range for R1?

Thank you.

Thank you, Martin, for taking the time to explain and for the graphs. I might still go ahead with the three-way cathode switch in the future. Yet, the urge was too strong, so I already made some modifications to the third stage this afternoon. It’s a simple mod: I clipped off the 680nF cathode bypas...

Martin, thoughts on arrangment in schematic 2? Thank you

Thanks, Martin. The plate resistor in my 3534 is 100k, just like in the larger models. Looking at the schematic, the third stage always had a 10k cathode resistor paired with the 100k plate resistor. They later added a 2.7k resistor in series with a 220nF capacitor in parallel with the 10k cathode r...

Initial idea, thoughts?

I might be on a bit of an amp modding spree, and I need your help again. I have a Bogner 3534, the 35W version. I don’t want to change anything about channels 1 and 2, but the third channel is just too hot for my taste. I tried to tame it by using a 5751 in V2, which affects both the second gain sta...

I have settled with 25k pot and 18k resistor for 29mA at 432v plate voltage = 40%, to 61mA at 410v plate voltage = 85%. Thats with the stock gray rank mesa STR440's

Some pictures FWIW. Thanks for your help