Guitar Gear Forum

Is there a way to put a master volume on a jtm 45. Mine is a handwired clone. It has a solid state rectifier mod that's switchable to tube and an immortal amp mod that protects the trannys if a tube blows or there is a problem. Nice build and quiet, but to get that sweet tone of overdrive I have to blast my windows out. Hahaha. Anybody that can help or she's some insight would e greatly appreciated. Thanks.

It's been done quite a bit. If it's a clone, you may as well do the mod.

http://vintageamps.com/plexiboard/viewt ... f=1&t=5171

http://metroamp.com/wiki/index.php/Lar/Mar_PPI-MV

edited to add link

I've installed the LarMar many times and always gotten great results.

yup. do that ^

Zombie thread much??

JTM45's aren't that loud in the first place (at least compared to a 50 or 100w marshall).

Those amps are loose anyways, so LarMar would be best.

FYI, the position of the MV in the circuit causes the negative feedback (and presence) to be reduced when using the master, so it makes the amp woolier than it already is.

I added a Trainwreck Type 3 post phase inverter master volume (PPIMV) to 5F6A Bassman. It's a very simple addition and it works well. It's just a 1MA pot that mixes the two phase inverter streams together which cancel each other out.

This graphic is from a 5E3 but it works the same way in the 5F6A or JTM45. The two wires are connected after the phase inverter coupling caps at the power tubes' 220k grid leak resistors:

I have always enjoyed the simple Lee Jackson pre phase inverter mv. Easy and clean. Another way to control the volume is to insert a "insertion Effects Loop" which is Zero Loss as there are no component buffered boards like the Metro Zero Loss board. The insertion loop will allow rack mount effects to work ( not sure about pedals) and you may attenuate by using the effect as a master volume. Sometimes there are added advantages to this approach as well such as studio class Effects but an added saturation such achieved by Joe Holmes etc...

I JUST got a tube rectified JTM45 that sounds great, getting that tone at a lower volume would be cool. Will check the mods out. REALLY like the tone, sounds killer for that Gary Moore type blues tone,

My 2 cents fwiw.

The older Marshalls lack a conventional master and PPIMV both. They can ALL make good use of them. What i´m saying is that to get the most out of a PPIMV install on such an amp it needs to be combined with a "conventional" master as well to be able to control resolution of the phaserinverter and how it´s shoved into orbit.

Ditto it might be a real good idea to replace the 100nF coupling caps within with 22nF ones if you tend to push the amp even further with a pedal.

clipless bumper wrote:Zombie thread much??

Most ironic post in GAB history.

TurboPablo wrote:

clipless bumper wrote:Zombie thread much??

Most ironic post in GAB history.