Bass Valvecaster Build and Schematic

[swamphorn]

...

almost, the orange wire should be connected to the other side of the 1M resistor and should have its own 1M resistor in its path.

A series resistor shouldn't be necessary since the bias point is going to the bottom of the pots and the op amp.

[lake_land]

Got it! Thank you.

Well, I've got it all wired up now, and it sounds great! My only issue is that there seems to be a bit of a lag in the overdrive kicking in on each note. Like, I will play a note and I hear the dry sound, then a few milliseconds later I hear the wet, overdriven sound join in. Is this normal behavior? Or can it be modified somehow?

EDIT: this seems particularly pronounced when both tubes are engaged and the first one is set to a really high gain setting.



Cheers,

Luke

[rankot]

Have you tried this "presence"? I tried to simulate this, and it doesn't do what it should.

[anotherjim]

Grid blocking? Try fitting a resistor in series with the first tube grid. 33k is common.

Dry sound 1uF is better fed from the input opamps output directly  - not from the tube grid side as drawn.
The 1uF cap into the first tube grid must not ever have leakage. It can be smaller to avoid using an electrolytic. The same goes for all coupling caps into the tube grids.
The size of the coupling caps can be calculated using the load resistance that follows after it to find the corner frequency of the hi-pass RC filter formed. I have a simple cheat for a starting value for the caps.
Resistance Cap
1M           10n
100k         100n
10k           1u
These values suit guitar. Doubling the cap value gets another octave down for bass.

Your grid resistors are 470k so 100n has to be a big enough coupling cap. Although 1uF film caps are easy to find, it's cheaper to avoid them. Not having an electrolytic cap should mean it's unlikely to pass leakage current which will mess with the tube grid bias.

[iainpunk]

Have you tried this "presence"? I tried to simulate this, and it doesn't do what it should.

yeah i just noticed that my suggested capacitance is 10 times to large, tis a high cut now, not a presence, am i correct when i say that it corners at about 500Hz, i originally meant it to corner at 5kHz...