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In Reply to: RE: 100-ohm or 220-ohm will be fine. posted by kylealers@gmail.com on August 13, 2015 at 02:31:50
Beer always makes my fingers "looser" and the ears "better."
8^)
Follow Ups:
Where will be best to earth this artificial centre tap?
Tie one end of the two resistors together. Solder this pigtail to a lug which is bolted to the chassis. You can do this at the power lamp (which is the first to get the heater line tap from the PT, in most Fender amps). Or anywhere close to the tap point off the PT.
See the two 100-ohm resistors tied to ground, after the power lamp in this Super Reverb? The clipped, heavy green lines come from the PT.
I've downloaded PSU designer and I want tweak this power supply a bit how do I calculate the load resistance? and how do I know what resistance a capacitor holds?
There are ways to improve the PSU, without re-designing the unit from scratch. Is this mod going into the bass pre-amp or the main bass DIY amp you wish to construct?
Better diodes, better filter caps, stable rail resistors are all good starting points.
So I decided to run my heaters in ac just for now I will hear how much the noise is. When my heater transformer doesn't have a centre tap is it important to make a artificial centre tap? Like in the pic?
Yes, artificial center tap is the way to go... if no actual CT.
Wrap the two heater lines together and with the two resistors making an artificial CT --- you'd be surprised how quiet the line is. Keep the heat lines above the socket surface and away from signal lines.
Like this:
This is the diagram exactly like I have it now any tips or hints before I test?
You sure you want to run the 12AX7 after the 5670? I thought you wanted one line with no TS and the other one with a TS. I think the gain stage with one 12AX7 as input tube is sufficient for your needs.
Just run another input into the 68k-ohm resistor before the first half of the 12AX7. OUT #1 from the 5670 to the bass amp input --- not connected to the 12AX7. OUTPUT #2, into a separate input of the bass amp.
Have each input jack ground out, when not in use. Then, plug the bass guitar into whichever gain stage that you want (no stack or tone stack).
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