Piazza Mod Wiring
Greg I have a crystal mic with a 5meg volume pot that I would like to try installing the "Piazzo Mod" on. This means puttting a capacitor in there to preserve treble as you roll the volume down. Googling around I found a message from you where you said you didn't think this mod actually made any difference. I'm sure you're right but I'd like to try it anyway. I have several capacitors to try ranging in value from .100pf to .600pf.
My question is where do I solder in the capacitor? Referencing this diagram here: http://www.jt30.com/harp-mic-volume-control-wiring, do I put it in the green wire, between the "center of the pot" and the center of the connector? Or in the red wire, between "Hot (+) side of element" and the 'left' or upper in this diagram lug on the pot?
Thanks,
Steve
Thanks Greg. So I do this:
1. Clip the wire going from the mic connector to the volume control (the red wire in the wiring diagram I linked to above).
2. Solder one end of the capacitor to the vc.
3. Solder the other end of the cap to the "red" wire going to mic connector.
Is this correct?
Thanks,
Steve
HI, Steve
No - you don't need to clip any wires. Just solder the cap between the element + and the wiper (center terminal) at the potentiometer.
/Greg
Greg,
Thanks for your instructions. I finally installed the capacitor, and I think it does work as advertised. I don't notice any difference with the volume full on, but it doesn't get as dark when I turn down. From what I've read on "treble bleed" circuits in guitars, I think it's a bass frequency filter that only kicks in as you turn the volume down. All the treble passes through all the time, but as you turn down more of the bass gets filter out. The bass frequencies gets softer quicker.
I like that, others may not. But in truth I usually have the volume full on most of the time with my crystals, so I might not get much benefit from this mod. I used a 150pf capacitor. I have other values but haven't tried them yet.
Incidentally, I managed to jam a 10meg ohm volume pot into my JT-30 shell for use with a crystal element. Previously I had a 5 meg pot, which sucked just a bit of tone and volume out. With the 10 meg pot I can't detect any loss. But it's a rube golberg mess of of silicone and stuff holding it in place. But it works well so far.
Steve
P.S. Do you make inline on/off controls?
If my memory is correct - I made someone an on-off control once and I think I still have some of the switches I found that fit. But I'd have to look and I can't - I'm on my way out the door and on vacation for a week. Feel free to get in touch with me Feb 1.
Because I don't believe in the mod (tried connecting/disconnecting the cap in a Hohner Blues Blaster while listneing, couldn't hear a diff), I don't do them. But I did a little research and found this schematic for you:
http://www.jt30.com/jt30page/oldsite/piazza.html
Let me know what you find!
FYI - Rod didn't invent this. You can find it on some early electric guitar vollume controls