Master of the Master

What Does That Mean? 

Maybe I should start by telling the story about an amp that I built.  It started with a JCM 800 2204 kit and a chassis from Triode Electronics.  It was a hand-wired kit, with a turret board and silver connectors.  Triode Electronics sends a box of parts (excellent quality, high end parts), with instructions and a layout diagram.  The builder sorts through all of the parts, including a pile of resistors and caps, and a boat load of different colored wires, knobs, transformers and a bunch of other stuff.  

I built a custom cabinet for the kit and branded the head, HEAT.

So anyway, after putting the kit together I made a few modifications to the standard grounding circuit and dropped the white noise level down quite a bit, and changed the values of some resisters and caps in the preamp circuit to give it just a little more gain (not much more, just a touch). 

After playing the HEAT amp for a few weeks I quickly learned that the amp sounded absolutely amazing.  When I was in North Carolina I let some of the people use the amp in my studios.  People raved about the sound of the HEAT amp.  It was a relief and a rush to know that my hand-wired point-to-point amp had turned out great.   Several people asked me if I would build one for them.  They lost interest when I told them the price.

There was one small problem with the amp.  Even though it was 50 watts, it was extremely loud.  I mean, really freaking loud.  Blow your ear drums out loud.  Rarely was the master volume ever turned over "2" and was usually between "1/2 and 1."  

Fast forward several years, the studios are sold, and my wife and I have moved to Oregon.  Along the way, I picked up two Marshall DSL combos: a DSL15c and a DSL 40c.  Of course, I did mods to the amps and upgraded the speakers.  I have used the DSL15c more than the DSL 40c.  Because of its crazy volume, I've rarely used the HEAT.

A New Master Enters The Room

Lately, I've been thinking about the HEAT amp and how it was sitting around and not being used.  Considered how amazing it sounds, not using it started to seem like sacrilege.

The JCM-800 2204 is a 50-watt Master volume amp, that has a pre-amp volume and a master volume.  That was all well and good, but as you know, I could only turn the master volume to "1."

After some research, I decided to try a PPIMV mod (Post-Phase-Inverter-Master-Volume).  The PPIMV mod added a third volume, which enters the circuit after the phase-inverter, which is right before it hits the power section.

With the PPIMV mod in place, I can turn both the Pre-Amp Volume and the Master Volume to around 2 o'clock (little past half-way).   That is the sweet spot for me on this amp.  At those volume settings without the PPIMV, the amp could be heard at least a block away.

Now with the PPIMV, I call it the Master of the Master, I can dial in the overall volume to any level needed to fit the venue. 

SWEET!

Enjoy the Music! 

Jimmy