The Amp Garage

Well not likely since your power transformer will need to supply 1.200 more amps of heater current since a 5881 pulls .900 amps and a 34 needs 1.500 amps. Also pin 1 needs to be jumped to to pin 8 and a 34 will need about 8 volts less bias voltage which may be out of range of your bias pot without ...

martin manning wrote: ↑Mon Dec 18, 2023 2:46 pm You should be ok. The B+ will drop with the current draw. Just bias them conservatively. What primary impedance do you have?

Primary impedance is 6k6. What about EL34's?

Sorry, I meant 457v.

I'm building a JTM45. Well technically a Dirty Shirley, but the power section is a JTM45. I'm ready to power it up, but the 5881 tubes that I ordered won't arrive until late this week. I've gone through all the initial testing with the GZ34 rectifier tube and 3 preamp tubes installed. It's reading a...

bepone wrote: ↑Fri Dec 08, 2023 3:49 pm vintage 30 is not ok speaker, it is very irritant, only good for loud heavy metal ..

I like my Vintage 30 with my other amps.

Is it OK to have the OT primaries right near the heater wires? Would this cause any issues?

Well, I finished rebuilding it back to Express specs. I don't know, maybe I just don't jive with this circuit. There's something about the frequencies that I'm just not liking. I'm not sure if it's something in the midrange or the treble frequencies. Could be my cabinet, which is a Suhr 2x12 with a ...

Reeltarded wrote: ↑Sun Dec 03, 2023 11:16 pm Try it on either or any, but it is a good place. You can moderate it and hammer the amp gain or volume for a huge array of textures.

And you said you made it foot switchable?

Reeltarded wrote: ↑Sun Dec 03, 2023 8:35 pm The ground end.. to a pot that goes to ground. It just increases the cathode value on the stage, like if 1k5 then 26k5 total at full rotation with 25k pot.

Ahh ok, that makes sense. Would you do that on the 2nd stage?

Reeltarded wrote: ↑Sun Dec 03, 2023 7:14 am So, you simply add 25k pot on cathode tail to ground. It is that simple and you dial in how much fire overall.

Maybe I'm just dumb but I'm not sure what you mean by cathode tail.

Reeltarded wrote: ↑Sun Dec 03, 2023 3:10 am It is rarely something worth doing. That variable cathode tail I described is hundreds of times more useful for a similar but better action with infinite degrees.

Yeah, can you explain that variable cathode tail thing?

Silver micas have a reputation for one in many being shit. Possible. FLY the switch wires ALL THE WAY to the deck of the headbox. That situation is not great, there are also some safety reasons to use the Farady coil instead of shield there depending on wire prep and voltage capacity. I'm probably ...

I found a pic I took before I started ripping it apart. Ignore my attempt at the split load switch, and the few component additions. That was my attempt at converting the preamp to a Komet 60. That odd noise was happening before and after those changes.

Littlewyan wrote: ↑Sat Dec 02, 2023 11:51 pm It’s normal to hear some sound without a speaker. I think it comes from the OT.

Use Silver Mica, don’t use Ceramic.

Are you rebuilding it as an Express again?

Yeah, I think so. I liked the Komet 60 sound, but it's not all that different from a few of my Marshall type amps.

What type of caps are recommended for the treble cap and the bright caps? Right now I'm using mica. Would ceramic be better?