Tuesday, April 1, 2014

BitMo Trio Mod Install

I got the BitMo Trio Mod in today, and I started working on installing it. It has a a scary copyright notice on the front saying I can't say what it does, blah blah blah, so I will only describe what it does and how, rather than describe the components it comes with and the direct connections.

This mod consists of two parts: a DPDT switch and a push/pull potentiometer with a DPDT switch attached to the back. If the pot is in the down position, it uses one set of the DPDT's poles, and if the pot is in the up position, the other set of the DPDT's poles are active.

The first mod only uses the DPDT switch, and works as follows.

First of all, DO NOT BREAK THE DPDT SWITCH. I have done this twice already. Make sure not to overheat the switch, and only solder it when in the "Off", or middle position. There is an option for both a Version 2 and Version 3 Valve Jr. Mine is the Model 2, but I have changed R1 to 1 Mega ohm, so it has the same affected component as the Model 3 amp. However, I chose to use the Model 2 schematic. To do this, cut R1 off from the main board and make two connections on to the end of R1, and to the place on the board where R1 previously was. If you did the Model 3 mod, you would keep R1 soldered in and solder these connections in parallel.
  • Option 1: "Bright." Straps a small "bright" capacitor in parallel with the volume pot output. Fender imitation sound. This setting has great gain. When you hit the strings hard enough, you've got a good classic rock tone already. 
  • Option 2: "Brit." British style sound, increases impedance for great mids. My favorite setting as of now, super clean and mellow, no matter how hard you pluck. 
  • Option 3: "Brat." Straps an extremely small capacitor with the volume pot output. Cuts the lows. So much treble. 
At first, I couldn't notice any difference, and just more hum. After playing a few chords on each setting, I noticed a major difference in each channel. I think the hum could be cut by using some insulation for the two long wires I used, shown below.

I covered the two long thin, orange wires with yellow electrical tape, and pulled two wires from the insulated wire that came with the kit that I did not use. So now, all wires should be insulated, and there are no unused wires floating around. Result? No less hum. It might be interference, since the DPDT switch is right next to the volume pot. That was advised against. I might build some sort of smallmouth Faraday cage to isolate the issue.

Notice the long orange wire to R1 from the DPDT.
Current front of the amp. New DPDT switch is far right, and new push-pull pot will be above the input (hole already drilled).

No comments:

Post a Comment