Frackquake Preamp (Frog Preamp)

[Timko]

Now that cooler temperatures and shorter days are here, I've found myself getting back in the building game.  This was my first preamp pedal, and I only managed to shock myself once!  This is Mark Price's Frog Preamp, based on the Alembic F2B, which is based on the preamp section of the late 60's Fender Dual Showman.  It's got tons of volume, as well options for added brightness, less brightness, and clipping.  I have settled on one set of clipping diodes, the 1N270 (often used in peoples Klon Klones).  I'm still trying out the 2nd set of diodes.  It's got a traditional Fender tone stack, which seems to match my main Ampeg Rocket really well.  There's no footswitch as this is something I have sitting on top of my amp in an always on setup.

The name comes from a 5.0ish earthquake that I felt in my office while I was building it.  The earthquake originated in Oklahoma, most certainly due to fracking.

This is a remarkably simple build when comparing it to some of the other monsterous delays and modulation pedals I've built.  You need to make sure you order the right components, but once that's done, you can get it put together in a short amount of time.  However, I'll give people the advice to cut the flat parts off the bottom of the tone stack pots because they could potentially ground out the capacitors in the tone stack due to the circuit layout.  I had this problem, and spent a couple of days debugging it.  You may also have to cut down the heat sinks to make it fit (I had to cut the fins off the one I had in there), but they'll still dissipate heat enough to function.

The graphics turned out all right, but I messed up and put the control text too close to the knobs.  Aside from that small detail, I'm really happy with the way it turned out.  At some point in the future I am going to create a dual preamp pedal (more in the spirit of the Alembic) with a way to jump the channels.  I may also remove the mids tone pot from the chain, setting it to a fixed value.

[playpunk]

Fantastic! Are you using it on guitar or bass?

[Timko]

Guitar.  I'm running it into a '65 Ampeg Rocket at the end of my chain at the moment.  I've been through a couple of guitars for the perfect sound.  It makes my Gretsch feedback like a demon, but my G&L Legacy seems to sound nice.  I'm taking it to my guitar store later this evening to pair it with some different amps and instruments, so we'll see how that goes.  I need to try it with a solid body 'bucker guitar still.

[markeprice]

Timko, great work on the preamp enclosure!  I love the graphic, since I experienced the same earthquake!   I have been making these preamps for about a year now, and each one, including the sub-miniature tube versions have been solid as a rock.  I think if I ever create a new version of PCB, I may move the capacitors that caused your problem from behind that potentiometer.  The problem can be avoided, but there is that potential for shorting if that tab is not clipped off the potentiometer or, the cap leads are a bit too long.  Live and learn!  I agree that loading up the board components is fairly simple.  I think the boxing in the enclosure is the more complicated part.  Regarding using with the bass guitar,  I love it on my bass.  You can really eq the bass pretty easily.  This same circuit, (Alembic F2b) the one that David Gilmour uses, was borrowed from Roger Waters (bassist) by his guitar tech.  They are still used in his studio as far as I know.  I always wondered if Roger ever got them back or bought some more....

[Coda-effects]

Really cool graphics