Tube Amp Archive

I have a 100W Mesa Boogie Mark III Reverb head and the overall gain level that the amp delivers seems quite low to me, so I'm going to replace the preamp tubes. Is it worth changing the V4 12AX7, i.e. the tube that is associated with the reverb of the amp, if my goal is an increase of the overall ga...

I recently wanted to use a Fender Twin Reverb blackface reissue for reamping purposes and with reactive loads, but I soon noticed that it only has 4 ohm speaker outs whereas the two reactive loads that I use (Suhr Reactive Load / St. Rock React:IR) are both rated at 8 ohm. Knowing that the Twin Reve...

Thanks for all the helpful answers! I'll definitely trust the new tech then. Hopefully the recap wi'll turn out alright.

I talked to a new tech (old one is in retirement now) about the filter cap replacement job that my Mesa Mark III amplifier needs. He told me that these amps have very intricate PCB connections and paths and he doesn't want to mess with them due to potential cold solder joint possibilities. Instead o...

I've been playing with my 50W Fender blackface clone head and noticed that the amp decreased in power output all of a sudden and the tone got a little bit fuzzy. I swapped the preamp tubes but they don't seem to be the problem, so I assume it has to be the powertubes. I want to test the amp with ano...

I recently encountered a problem with my Mesa Quad and it happened overnight. I'm using the Quad on the first lead channel and a 750 Hz scoop on max on the graphic EQ and, without changing my signal path and settings one bit, the Quad started to sound much more mid-focussed and not as tight as it di...

The insulator is melted. It's dead. This transfomer needs to be replaced 100%? What would happen if I would rewire the input wires correctly and then turn it on again? Would the transformer melt again or worse? What about the safety hazards inside these preamps: Are there any lethal voltages left a...

I have a guitar preamp with a toroidal transformer that was wired incorrectly for the European wall outlets. As I fired it up, the sound was there for mere seconds, and then smoke came out of the preamp. Parts of the transformer insulation melted: https://i.imgur.com/xCVmR8d.jpeg Would you say that ...

Well, I thought the switch would be off if it's facing down, at least that's what the amp builder told me. You're telling me now that it's exactly the other way around? I'm a bit confused to say the least. The picture doesn't lie, so it has to deactivate the mod in the up position, like this picture...

This is how the GNFB switch looks inside the amp: https://i.imgur.com/oHISFhz.jpg SPDT function dictates that the upper and middle parts of the switch are activated when the switch faces up. These upper and middle parts are connected to the rest of the amp, whereas the lower part is not, which means...

Well I can only think of the opposite being an issue. If the GNFB is engaged and you're hearing odd noises, then you've got the OT leads reversed phase so you're creating PFB instead of NFB. That can sometimes be a horrid howling noise, others be a more subtle sound like you're getting. Have you co...

That part is very easy. You need a spst switch you put it inline between the source of the feed for the negative feedback and it's next point, and connect the two leads of the wires to either side of the switch. toggling it either completes the circuit or disables it. If you're talking the GNFB on ...

I already saw that schematic. What I'm interested in are the local and global negative feedback mods that can be engaged via switches. Are there any schematics for that?

Does anybody have the schematics for the standard global and local negative feedback mods for Robben Ford style Dumbles?