Master volume on Musicmaster amp

[isaac_teller]

Hello. How would I put a post phase inverter(interstage transformer) master volume on this amp(Lamar type)? There are no grid leak resistors. I tried a cross-line 1 meg pot but it's only really effective from 0-1.5. Thank you.
https://music-electronics-forum.com/filedata/fetch?id=871806&d=1636912611

[Latole]

I don't know.

Fender MusicMaster :

https://el34world.com/charts/Schematics/files/Fender/Fender_musicmaster_bass_schem.pdf

[Leevi]

I tried a cross-line 1 meg pot but it's only really effective from 0-1.5.

Try 250K Audio pot

/Leevi

[Latole]

Pot must be a A audio not B.

I did not say a pot will work !

[isaac_teller]

Thanx. I'll give it a try.

[sluckey]

I wonder if that PI transformer will be happy when that crossline MV puts a short across the secondary.      

[pdf64]

I really don’t see the point of a master volume here. There’s only 2 common cathode gain stages in cascade feeding it, the second inly has a 15k anode load.
That boils down to ‘unless using an external pedal, there won’t be much if any preamp overdrive available’.

Whatever, a LarMar / type 2 master is just a volume control potential divider across each leg of the interstage transformer.
Imagine the winding is a guitar pickup and consider how a volume control is arranged there.

[isaac_teller]

How about adding another gain stage(100K/1.5K) before the interstage in addition to the master?

[dwinstonwood]

How about adding another gain stage(100K/1.5K) before the interstage in addition to the master?

This preamp has worked great for me. It has the "extra" gain stage, and an extra gain/volume pot. You don't need the full TMB tone stack, if you don't want it.
Bypass the third cathode if you want more gain.

[PRR]

The 15K on the IT primary. Replace with 25K Audio wired as rheostat so "10" is 25k, "5" is a few K, and "0" is of course near zero.

However I don't think this is a good amp to hack up. It is what it is, is unique, and may eventually be recognized as "not just another Fender Champ/Deluxe/Twin".