Thanks Scotty. With an MXR distortion, Line6 Echo Park and Alfies Pazzzzar in from of it, it really has become my goto amp. I'm finally getting set up to record it properly. The sound on that video is awful.
So I was messing around with the Kalamazoo some more and a thought occurred to me. The R-14 voltage divider resister sets the amount of reverb to dry signal on this amp. Sort of a permanent mix control. My earlier mod was to add a push pull pot so the resister could be jumped out. This lowered the amount of reverb on the signal, drastically and removed a lot of the hum that this reverb circuit is famous for while doing it. The thought that came to me was simple. Why can't I replace the 470K (R14) resister with a pot and be able to dial back the mix instead of just having a switch for high and low?
To try out the idea I used a 500K mini pot. It worked well but I decided to use a push pull for the final install. This allowed me to move the switch wires from the back of the loudness pot to the back of the new mix pot. Then I moved the wires from the old boost switch to the back of the loudness pot.
And now we have a knobs that adjusts the amount of reverb to dry signal ratio. I installed the push pull in the hole for the #1 input jack where I previously had the boost switch.
While I was playing around with the amp I decided to see if I could slow down the rate on the tremolo a bit. It's not an effect I use much but when I use it I like the very slow kind of tremolo effect. So I took the 470K resister from the reverb voltage divider and installed it in series with the one on the rate potentiometer. This made it more to my liking but I may play around with this some more.
1. This is the NEW R-14 Mod which replaces the 470k resistor ("R-14") that the preamp is using as a voltage divider with a 500K push pull pot. Pulling out this knob and turning the "Reverb" knob all the way up removes the R14 pot from the circuit and provides a nice subtle reverb with no hum at all. Pushing the knob in allows you to dial in much more reverb.
2. The Boost switch that was activated by the toggle on the far left is now activated by pulling out the loudness knob. This seemed more intuitive to me and allows me to mod the amp without drilling more holes in it. What this switch actually does is jump the signal from the output of the Loudness knob all the way to the end of the tone stack. This makes the little Kalamazoo reverb 12 sound like a 12 watt amp.
3. The tone stack ground lift switch. Once the power switch had been relocated to position #6 I had this switch that no longer had a use. I decided to try to use it to lift the ground on the tone stack and see if I could get that sort of Epi Valve Jr one knob tone. While it does give a slight volume boost it also leaves the signal very bass heavy and it's not a very useful mod. Don't worry too much about trying this one.
4. All I did here was swap out the .01 "C-3" capacitor on the bass control with a .47 orange drop which bumped up the treble a tiny bit.
5. Increased the value of the resistance on the Tremolo Rate pot to slow it down some more.
6. Power Switch. As mentioned before I moved the power switch which is a MUST on these amps if you want to remove a lot of hum. Since I had to install a new switch any way I made it a SPDT 3 position toggle and am currently using the up position as a standby switch.
Steve Clark: I'd rather be playing guitar
Nov 12, 2015 5:38:31 GMT -5
Steve Clark: Counting down to my new guitar
Dec 22, 2015 2:51:07 GMT -5
Steve Clark: Happy new year!
Dec 31, 2015 16:00:56 GMT -5
tricky: Just passing by so thought I would drop in and say a big Hiya to the hard core keeping the board going. Hope you are all well, have a great 2016 and keep it real(ish)!!
Jan 19, 2016 18:21:19 GMT -5
rhod34: Richard, none of us are real. I'm my own imaginary friend
Jan 21, 2016 11:44:24 GMT -5
Steve Clark: I've never met Rhod. I assume he's just some Welsh computer 'bot'
Jan 22, 2016 4:53:37 GMT -5
rhod34: you leave my bottom out of this, ya perv!
Jan 22, 2016 15:25:24 GMT -5
Steve Clark: In Wales bot-net has a very different meaning
Jan 26, 2016 5:21:44 GMT -5
Steve Clark: My guitar is in the UK! Awaiting news from customs
Feb 9, 2016 6:30:31 GMT -5