DIY tube overdrive pedal

[jim p]

Still checking things out on the starved plate circuit. The stock setup on the ART has a heater supply of 5.7 volts so I shorted the diode in the ground leg of the three terminal regulator causing the control grid current to drop to 3uA from 5uA. So I may try reducing the heater voltage to the tube a bit more to see where the tradeoff between gain and grid current is. The gain of a single stage is looking to be approx 31 with the maximum signal at the control grid before distortion at 40mVolts peak to peak. So if you build your own box you will need to buffer the signal to the tube due to its low impedance and reduce its amplititude if you want a clean sound before going into distortion.

So you don’t need to boil off very many electrons with a plate current of only 60uA I have too look around but thought I saw a curve on heater voltage and electron emission.
If I can reduce the grid current more a higher value grid resistor can be used thus increasing the input impedance of the tube.

[duhvoodooman***]

I'm following your progress on this with great interest, Jim. A couple years back, I bought one of those $30 ART tube preamps on a whim and haven't done anything with it yet. If you get your project running well & sounding good (we're gonna need a clip or two here, as I'm sure you realize!), I may give it a go.

[M29]

Yes indeed this is very interesting Jim, I have an ART preamp setting around here too!

[Duffy]

I have one of the studio art mic preamps and can't figure out how to use it. I have been using it in a small room and it "squeals" like H!#! when I turn up the knobs over anything but about normal volume.

I am positive I am doing something wrong and don't know how to use the item.

I am looking for a nice tube warming of the vocal but when I try to apply some nice smooth overdrive I get howling squealing going on.

I'm sure you know what I'm talking about and what I'm doing wrong. Can you please advise me as what I should do to correct the problem, I'll check it out tonight if I get some good directions.

Thanks in advance.