How do Pre amp pedals work

[stretch2011]

I imagine your basically taking the first gain stage off an amp and putting it inside a pedal box. Wouldn't you need a voltage reducer for the 6.3v heating element and something to produce high voltages?

[LOUDthud]

What's usually does is that the pedal is connected to 12VAC from a wall wart. The 12VAC connects to a 12AX7 and also a 12V filament transformer connected backwards to produce 120VAC or 240VAC to derive the high voltage.

[vibratoking]

I imagine your basically taking the first gain stage off an amp and putting it inside a pedal box. Wouldn't you need a voltage reducer for the 6.3v heating element and something to produce high voltages?

There is no usual here IMO. Some designs run high B+ and get it a variety of ways. Like external AC wall warts or internal power transformers. Some use low B+, like 25V, and design with starved plates. Pick your poison.

[martin manning]

Here is one (EH English Muffin) that puts an entire Marshall-type preamp in a box, complete with CF-driven TMB tone stack.

[sluckey]

Hoffman has a preamp pedal that has a lot of Marshall flavor. Scroll down about 2/3 of the way on this page for lot's of info...

http://el34world.com/schematics.htm

[stretch2011]

Those are pretty cool. So here's a question that will have very opinionated answers. Which way will give the best sound

[RockinRocket]

High b+.

Im working at a 12ax7 boost pedal and need to figure out what volts would be ideal for a boost. So if I can figure out a good power supply ill post it here.

[DonMoose]

For even more fun, I saw a 'HiFi' item featuring one 12ax7. It was _glued_ in place and had an orange LED below it to make it LOOK like it was doing something.

[surfsup]

Those are pretty cool. So here's a question that will have very opinionated answers. Which way will give the best sound

The sound will be determined by the operating point of the stage(s) and voltages, as well as the guitars/power amp you are plugged into. I would assume if this was the same the sound would be same - aside from any hum or wiring issues that would cause noise.

One advantage is building separate preamps and power amps and connecting them together to get different capabilities.

[stretch2011]

I've decided on a matchless hotbox. Picked up a transformer cheap and just need A few parts and I'll be good to go.

[matt h]

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[Eric_BK]

You could build the Valvecaster. I built two, which use 12AU7 tubes. They're great in front of tube amps without a dedicated gain stage. I have an old Univox, which is basically a clean amp, even at higher volume (albeit a little breakup). After engaging the VC pedal, it gives it that overdriven push I'm looking for. It also works well with other pedals. I have a 9 - 12V power on it as well.