if it works and you are looking for a elevation useable for cathode and fixed bias mode ... dividing the bleeder-resitor is one chance

That should be standard in any modern amp...

hello, what do you guys suggest to attach the chassis to an amp in a marshall like format (controls to the front of the head of the cabinet)

it has to be something that you can just tighten from outside the cabinet without holding it from the inside while you tighten from the outside.

thanks

ganz Klassisch ist ja ein 5E3....

Hi,

if you are still chasing hum in these amps then try connecting the ends of the two 100R resistors that are currently going to the star ground t o the cathode of the output tubes. It is sufficient to connect them to the cathode side of R23 on the board.

This results in a modest heater elevation (poor man's heater elevation, even Valco did it) when the amp is operated in cathode bias mode. You can easily compare the result by switching between the cathode and fixed bias mode, as in the fixed bias mode this elevation is rendered ineffective.

If this helps, a permanent heater elevation working in both modes is also not too hard to implement.

cheers,

max

hello, i've tried this method but didn't noticed any difference between fixed and cathode bias

some pictures of my diy cabinet

Nice ! :topjob:


Can you make some soundfiles?

here's some noodling, not a proper demo but hey, better then nothing right

Some pedals in the beginning (klon, velvet fuzz and octaves from an eventide pitchfactor), then, without any pedals i pushed one channel and then both channels. after i also maxed the master still without any pedals. (just some seconds with octaves)
in the end i added some reverb from a line6 m9

the guitar is a tokai MIJ strat with a warmoth neck, pickups are original. the cab is a 4x10 orange

recorded with cell phone so: compressed and bad audio

https://youtu.be/vpUzMYm8Ppk

Hallo allerseits,

bevor ich bestelle: was sind denn das für Chickenheads auf den Originalfotos? "Gewölbt" oder "mini"? @Dirk

besten Dank im Voraus!

Hi folks,
I just got my 5Ä3 ready. Pentode mode works nice, in fact very nice, no hum or other interference. Sound options are great. But... when I switch to triode mode the scream is enormous. As Master and other volumes are at zero, no guitar plugged in, the reason must be in power amp. After reading this conversation I swapped the OT input wires, but this didn't have any effect to the oscillation. Any ideas how to go further?

Hi folks,
I just got my 5Ä3 ready. Pentode mode works nice, in fact very nice, no hum or other interference. Sound options are great. But... when I switch to triode mode the scream is enormous. As Master and other volumes are at zero, no guitar plugged in, the reason must be in power amp. After reading this conversation I swapped the OT input wires, but this didn't have any effect to the oscillation. Any ideas how to go further?

Hello
Have you tried exactly like posted before?
Like this:
http://www.tube-town.de/ttforum/index.php?action=dlattach;topic=21726.0;attach=55215;image

Hello, i have one question.
Anyone tried to shield the amp wooden enclosure and connect the shielding to ground? Or you just put the amp inside the wooden enclosure without shielding?

I always do the shielding. In your cabinet I would use aluminium or copper foil. I prefer very thin sheet u-metal which is very easy to handle and you can cut it with ordinary scissors.

To my problem. I swapped the wires which come from OT, no else. My connection is such that the OT cables come to the tube sockets, pin 3, and from the tube socket the wiring goes to the switch.

I always do the shielding. In your cabinet I would use aluminium or copper foil. I prefer very thin sheet u-metal which is very easy to handle and you can cut it with ordinary scissors.

To my problem. I swapped the wires which come from OT, no else. My connection is such that the OT cables come to the tube sockets, pin 3, and from the tube socket the wiring goes to the switch.

thanks, when i have time i'll try it with some sort of sticky aluminium or copper sheets.
but i'll have to find a way to make continuity from the amp ground to the shielding, correct?

regarding the OT cables, if i remember correctly, my solution was just that, swapping the blue and brown wires that come from the OT

As the chassis is in ground you don't need any special connection. The weight of the amp takes care of the connection between the chassis and the shield foil (unless your chassis is "hanging in the air")