A few weekend ago I was in a local second hand music store and came across an Ernie Ball Volume Pedal Jr, this is a passive VP that uses a 250k pot to foot control volume from the guitar.....for 25 bucks it was a deal.
I connected it up with just the guitar to the pedal to the amp and it did everything nicely until......I used the tuner out jack it has, hooked up my TU3 and all of a sudden the highs were gone.
Of course I spent some time looking for the wrong solution, but Google knew....
Seems the tuner out and input are parallel, this make the input impedance real low and that knocks the highs out of the signal path (simplified explanation).
The solution is to modify the passive pedal to be active with a dual buffer, one on each output...lots of people have kits, or send in your pedal to be modded.....but me being DIY, that got me to thinking.....TUBE BUFFERS!!!!!!
I have a multi isolated output power supply that can power a pedal up to 18 VDC (8 @ 9 VDC 150 mA and 2 @ 18 VDC 400 mA).
All we need to do is design the buffer circuit, yes I said we because I think this would be a fun crowd source design exercise.
Is it practical, nope...do tubes belong "under foot", nope.....are there easier ways to do this, yep.......so why ..its just fun to do.
Starting with the power supply:
We have 18 VDC at 400 mA available, we could use a step up power supply to make a more usable voltage. Honestly any of the Fleabay Chineasium DC to DC converters will do.
Or are there any tube choices that would not need this, say 6GM8, 6DJ8, 12B4, or 12B4A
What ideas do any of you have......???
I connected it up with just the guitar to the pedal to the amp and it did everything nicely until......I used the tuner out jack it has, hooked up my TU3 and all of a sudden the highs were gone.
Of course I spent some time looking for the wrong solution, but Google knew....
Seems the tuner out and input are parallel, this make the input impedance real low and that knocks the highs out of the signal path (simplified explanation).
The solution is to modify the passive pedal to be active with a dual buffer, one on each output...lots of people have kits, or send in your pedal to be modded.....but me being DIY, that got me to thinking.....TUBE BUFFERS!!!!!!
I have a multi isolated output power supply that can power a pedal up to 18 VDC (8 @ 9 VDC 150 mA and 2 @ 18 VDC 400 mA).
All we need to do is design the buffer circuit, yes I said we because I think this would be a fun crowd source design exercise.
Is it practical, nope...do tubes belong "under foot", nope.....are there easier ways to do this, yep.......so why ..its just fun to do.
Starting with the power supply:
We have 18 VDC at 400 mA available, we could use a step up power supply to make a more usable voltage. Honestly any of the Fleabay Chineasium DC to DC converters will do.
Or are there any tube choices that would not need this, say 6GM8, 6DJ8, 12B4, or 12B4A
What ideas do any of you have......???