Tube Amp Archive

Indeed the OT was doctored with.
It turned out not being original either as the chassis cutout was altered as well along with additional mounting holes.
I did replace it with a replacement OT from Modulus as suggested (thanks Roe).
It is again a wonderful amp now with lots of low end.

Thanks.
Modulus is UK based which is convenient since I am in The Netherlands.

Indeed. This seems to be a 6K transformer rather than 3k5

Thanks.
Yes, it does connect to the other secondary leads.
I probably need do some measurements to see how it is connected internally

Hi all, I have a VOX AC50 (serial 3317) on the bench. It is functional but weak and noisy. Most caps are end of life and resistors are out of spec. It is a version without the infamous brimistor. I have a question about the output transformer. It has a loose wire which seems to have broken off from ...

Luckily for all the amp builders /electronic engineers here, the universe is electric.

Thank you Mr. Dumble.

Yes, that is the case.
Everything between 0 and 3dB is debatable.
I found a site where you can test it.
https://www.audiocheck.net/blindtests_level.php?lvl=3

Best,
Eric

I must warn you that I have never build such a circuit.
I guess if you just replace that valve for a set of MOSFET's and keep the same resistor values that the current is not that high.
-280V over 220K gives about 1.2mA / 356mW.

Merlin states that a MOSFET can be used instead of a valve in case you don't want the CF to contribute towards any tonality of its own.
Contribution towards tonality in case of the valve CF is due to clipping of the CF (top) and grid-current limiting (bottom) of the gain stage in front of the CF.

When making choices about applying VVR I guess one must take in consideration: * Where in the amp the distortion is generated (preamp/power amp) * What volume levels are required (-20dB/Bedroom level) * If tone consistency is important (PPIMV's can change tone ) * The required easy of use (how many ...

@Colossal, thanks for helping out
@Phil, a swift recovery

Looks great. Congratulations.

@alkuz1961 Yes, you are right regarding the grill cloth. This is an old picture from before I put the amp in. Currently the grill cloth is tight and does not have any waves. I might even have have put new grill cloth on. But thanks for the tip. This was my first cabinet. I learned a lot from buildin...

I have been where you are now. Indeed with a bit of routing, sanding and tolexing you will do just fine. I would pay special attention to the sanding. Take care of dents. Tolex can cover up a lot but not everything.