A friend of mine just build a Valvecaster: https://i.pinimg.com/originals/73/c0/6f/73c06fc64c2cfbc65eb390c60f303284.jpg
It is a 12au7 tube overdrive pedal designed for guitar.
I tried it whit harp and it sounded good. It is dark (in a good way, not muted) and woorks good as a preamp in front of a SS amp.
The thing that I dont like it was that the gain is too much. When you use just a little, barely moving the gain knob, it is great, good overdrive tone, but once you go up a little it gets very compressed.
We reduced R2 from 220k to 100k and that help a bit. But it is still to compressed as soon as you get the gain knob higher.
Any of you know a way to reduce even more the gain? or a way to make this pedal more harp frindly?
It would be greatly apreciated. ---------- Sorry for any misspell, english is not my first language.
I have built a number of tube pedals for the same purpose. It is difficult as these are essentially boost pedals for guitar. The best success I have had is with a Valve-e-tizer pedal based on a pcb by TH customs from Germany. I use this all the time now for playing through a PA via a DI box. I have put away my amp cab simulator pedal. As you say, it takes very little gain. The Valve-e-tizer seems to give me more latitude than a Valvecaster, decent tone control as well!
You could always try an in-line volume control before the Valvecaster to reduce the input...it helps a bit.
---------- Tom "Bad Paw" Lauten Loch Ness, Scotland www.nimbacreations.com
Last Edited by Tom Lauten on Aug 17, 2018 12:19 AM
I’m not totally familiar with them so I can’t comment from a knowledgeable point of view but a I suspect you could achieve the same sort of results with a simple volume pot with a treble bleed in line. ---------- Tom "Bad Paw" Lauten Loch Ness, Scotland www.nimbacreations.com
Try cutting the bus bar connecting c2 and r4, and then re-connect that spot with a 2mohm resistor. This will cut the drive to the second stage by 80%, allowing much more use of the gain pot. If you want to go one step further, try changing c1 and c2 to .1uF caps, allowing more bass through the circuit.
That is my friend playig whit his version of the valvecaster. He reduced the gain and the switch goes from stock (in order to use a simple vocal mic) to mod (less gain).
I have played it live and it works. ---------- Sorry for any misspell, english is not my first language.
