UP Bassman Main Board Layout

[dorrisant]

Ok... I was inspired by conversation on Bepone's post about this amp. I know he had a slightly different layout, but it got me thinking about how HAD did it.

I have this picture saved, don't remember where I got it... Does anyone have a link to this image? I'd like to revisit the surrounding discussion.

UP Bassman Board Detail.jpg

I circled the cap in red. My question is, what is this cap for. I can see, maybe incorrectly, how the 470ks could be connected for the voltage divider feeding V2. If that's so, what's this cap for. Is it between the center of the voltage divider and the grid for V2. If so, why? If not, then what?

Here is another pic that looks like a clone attempt:

24E1E01E-2795-40F6-B006-00E24258CBA4.jpeg

This layout only begs for more questions about this same area of interest.

Thanks for taking a look!

[pompeiisneaks]

That image comes from the dumble modded bassman I built.

https://ampgarage.com/forum/viewtopic.php?t=33721

so far the schematic has been pored over by a lot of people in that thread fixing what I got wrong etc.

let me know that's what you're looking at. I don't honestly know if that's the UP mods or not either. It has a very marshally sound to it. I just did a demo too if you haven't seen that.

~Phil

[m.alexander]

VID-20230201-WA0009.mp4

my build in 77 bassman 100 , KT77 master ppimv , bass channel

[m.alexander]

IMG-20221128-WA0062.jpg

[dorrisant]

Thanks for that, both of you! My personal mystery solved, I will read and digest your build, Phil.

Thanks many times over!

[jelle]

That amp is not an Ultraphonics amp, this is a high gain deal, the UP amps were revoiced clean amps instead. jelle

[dorrisant]

That amp is not an Ultraphonics amp, this is a high gain deal, the UP amps were revoiced clean amps instead. jelle

Do you have any more info on this particular type of circuit?... The high gain?

[WhopperPlate]

That amp is not an Ultraphonics amp, this is a high gain deal, the UP amps were revoiced clean amps instead. jelle

Do you have any more info on this particular type of circuit?... The high gain?

Isn’t this the rockphonix?

[m.alexander]

my bass reworked channel is amazing sound , ppimv master, but other channel not work in good way

i use schematic in TAG previne post.

[dorrisant]

Can you post your schematic?

[bepone]

the other channel is fender clean, this works good by default

[amplifiednation]

That amp is not an Ultraphonics amp, this is a high gain deal, the UP amps were revoiced clean amps instead. jelle

Some of them have a real gnarly high gain channel

[WhopperPlate]

That amp is not an Ultraphonics amp, this is a high gain deal, the UP amps were revoiced clean amps instead. jelle

Some of them have a real gnarly high gain channel

Kenny Wayne Shepherd describes how he has an amp with both channels, ultraphonix and rockphonix

[dorrisant]

I wish Jelle would let us know exactly what this is... bee bee ba dee dee dee dee... Calling for Welegen...

Anyway, here is what I have to this point: A Bugerra V55 as a donor headshell and chassis. It's pretty close in size to the original Bassman chassis anyway. I cut the top/bottom out of the chassis and installed a reconfigured aluminum plate. I have a Super Reverb PT and an old Twin OT, both Shumacher (606). Ordering a choke and some vitals later. I had a few chokes but nothing was close so I am getting a Hammond 4H 90mA. I had an old filter cap tray here so I'm using it... why not?

I'm gonna use the 5v filament winding for my relay supply. Two relays will control channel switching (one input jack) and the associated LED.

Off to finalize a parts order that includes this amp. Gotta make the plates too. Stop me if you see anything wonky.

[bepone]

nice!