In my past build (5w powered preamp) I installed my master volume pot across the OT secondary and ground, with the wiper feeding the output. There is an 8ohm 5w resistor across the pot/output. (8 ohm because of the OT secondary impedance and because a speaker may or may not be hooked up).
What would be the safe practice for accomplishing this trick with a higher wattage amp (speaker permanently connected), say 40w?
What would be the safe practice for accomplishing this trick with a higher wattage amp (speaker permanently connected), say 40w?
The original design was based on the herzog (guitar FX...single ended 6V6) but i've also been using it as a combo and for driving a tube Leslie speaker - It turned out really well.
I wanted to mesh the design with a Deluxe or Bassman style push-pull 6V6 or 6L6 output but I've read about people experiment with adding Masters to these style of circuits without outstanding results. My latest compromise was to build both designs into one box separated by that master volume. I know the herzog isn't widely enjoyed, but the circle I run with really digs the sound.
I wanted to mesh the design with a Deluxe or Bassman style push-pull 6V6 or 6L6 output but I've read about people experiment with adding Masters to these style of circuits without outstanding results. My latest compromise was to build both designs into one box separated by that master volume. I know the herzog isn't widely enjoyed, but the circle I run with really digs the sound.
Okay okay, so I take it there was little interest in this idea... I have since had another one:
Build the fx unit as one channel; input/preamp, 6V6, OT, which is then fed into CH 2 (which is the regular guitar amp clone) via my master vol and dummy load for the first OT. That way I can get the Master vol in the position that I love so much, and don't have to mess with a tried & tested clone circuit that wouldn't like a master volume much anyway. The Fx can be bypassed via footswitch or with a switched input jack.
I have a cheap source for the fx OT's, so not factoring cost, am I going the long-about way of building this?
Thanks!
adam
Build the fx unit as one channel; input/preamp, 6V6, OT, which is then fed into CH 2 (which is the regular guitar amp clone) via my master vol and dummy load for the first OT. That way I can get the Master vol in the position that I love so much, and don't have to mess with a tried & tested clone circuit that wouldn't like a master volume much anyway. The Fx can be bypassed via footswitch or with a switched input jack.
I have a cheap source for the fx OT's, so not factoring cost, am I going the long-about way of building this?
Thanks!
adam
Posting to the right forum where the guitar guys hang out would probably help, and since it is forum policy I'll move it there.Put a resistor in series with the pot (signal - resistor - pot - ground) with the wiper still as the output.
A 40 watt amp will have a signal of about 18Vrms at full tilt, so a 150k in series with a 10k pot will give a little over 1Vrms max on the pot as a starting point.
Thanks for your reply. Here is the output section of the champ clone:
In the 5W amp, this works wonders, I find.
Would this work in a higher-power, push-pull application? Would the method you describe accomplish the same thing? Would the only difference in my version need to be a (i.e. 30W amp) a 30W resistor?
Thanks!
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In the 5W amp, this works wonders, I find.
Would this work in a higher-power, push-pull application? Would the method you describe accomplish the same thing? Would the only difference in my version need to be a (i.e. 30W amp) a 30W resistor?
Thanks!
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Very Interested.....
Thanks for your reply. Here is the output section of the champ clone:
Hey Cancon...
I'm very interested in your findings / experimentation with the modified Champ circuit as a preamp for a Leslie. I've recently started on a Hammond B3 / Leslie 147 resurrection project for a friend. I've got the B3 and the Leslie 147 back to original spec and working well (both had been hacked badly by "techs" over the years). Now I need an appropriate preamp to drive the Leslie with the B3. I'm a guitar guy myself but I've always been fascinated with the B3/Leslie Mojo and I'm a huge fan of this classic sound.
My goal is to build a Tube preamp that will get fat cleans and grinding overdrive tones out of this Hammond / Leslie Combo (IE Deep Purple). I've used a 5F1 Champ that I built a while back to power it up and test the combo and it sounds pretty good, but it gets noisy just at the point when the clean tone starts to fatten up and way too hissy and noisy when pushed into that Jon Lord type overdrive.
I've read about the Champ/Herzog design on many forums but have yet to find anything really descriptive about it's modifications let alone being able to find a schematic.
anyway... 2 things. 1) i'd like to know your opinion regarding the noise threshold when driving a Leslie with your modded champ circuit and 2) do you have schematics that you'd be willing to share or point me to on the web?
Thanks!
Bluto1
In the 5W amp, this works wonders, I find.
Would this work in a higher-power, push-pull application? Would the method you describe accomplish the same thing? Would the only difference in my version need to be a (i.e. 30W amp) a 30W resistor?
Thanks!
Yes, a higher wattage resistor - but that's a poor example, look at the circuit from Jedmar, that includes the important resistor in series with the pot - and that series resistor should also be increased for higher power.
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