1981 Inventions LVL

Here's the new boost from Matt Hoopes. Cornish buffer up front, so like the DRV, not a true bypass effect unless you want to wire it that way. Signal is then amplified by half of a 1458 op amp, and then back to back inverting and tone shaping op amp stages with the LM833. Schematic below. If you're going to wire it for true bypass you can omit C4, and R7-8. Also note that D1-2 aren't acting as clipping diodes, but as (I think?) a limiter to prevent clipping or at least too much of it. 

Greer Amps Soma 63 Preamp

Cool JFET preamp circuit from Greer. Its supposed to sound like a Brownface-era Fender amp. I'd be curious what it sounds like without the transformer. Should fit just fine in a 125B with top mounted jacks. Schematic for reference.

DOD 210 FET Preamp

Got a little simple boost/preamp for your Thursday. Should be a pretty easy fit in a 1590A. J113 alternatives would be J201, 2N5457, and probably a couple other JFETs that are obsolete. 😑

BK Butler Tube Driver

Apparently it's tube week. Here's the Tube Driver made famous by David Gilmour. It uses a 12AX7 which is pushed by a dual opamp followed by a Fender-style tone stack. I kept the power section from John K's version of the Blue Tube. Fits easily in a 1590BB. Here's the schematic for reference.

Tube Works Blue Tube

Came across John K's vero of this circuit with a few mods (Mid pot, bipolar charge pump) and figured we needed a layout for it as well. Runs on 9-12v. Pots are all board mounted with the tube off board. Here's John's original layout.

Boss FA-1 FET Amplifier

Originally a bit of a flop from Boss, the FET Amplifier was made famous by U2's The Edge. It features a 2-band Baxendall tone stack and the Volume control is more like a gain control. Originals use 2 single opamps that are pretty hard to come by these days, so they've been replaced by a dual opamp. Pots are board mounted and it should all fit in a 1590B.

Benson Preamp

This one just traced over on FSB. It's essentially a modified Wampler Plexidrive with an added bass control. Unless you're really sure any through-hole J201s you have on hand are in spec/authentic, I'd suggest using MMBFJ201s, which are the SMD version which are still in production and much easier to get in spec than the discontinued through-hole version. SMD to through-hole conversion boards here.

Update August 19, 2019:

Corrected a few values that have now been confirmed by Benson. The traces haven't changed however.

Music Man Sabre II Guitar Preamp

Apparently the guitar players were feeling left out with the all the old Music Man bass preamps, cuz I got a ton of requests for the Sabre II Guitar pre. So here you go! Nice and small like the others with active bass and treble controls.

Music Man Sabre II Bass Preamp

Lot of requests for this one after I posted the Stingray pre a few weeks ago, so here's the Sabre II. Pretty similar the the Stingray but with a few value differences and extra resistor in the feedback loop, and the added bright switch.

Diezel VH4

Gotten a lot of requests for this one and I finally bit the bullet and laid it out. It's the pedal version of the 3rd channel on Diezel's VH4 amplifier with loads of tonal control and tons of gain on tap. Originals are buffered effects, with the input jack wired to the In pad, and a DPDT footswitch selecting between the Out and Buffer Out pads (footswitch wiring diagram below). You can also wire it for true bypass if you prefer and just ignore the Buffer Out pad. The pedal can also be used as a standalone preamp with the Power Out going to the input of a power amplifier (the return jack of an amp's effects loop). It's designed to run off a 12 or 18 volt supply, but it will apparently work just fine of a 9 volt supply (and if planning on going that route, I'd omit the regulator and jump its in and out pads). Also, the indicator LED can be hard mounted to the board, and the whole layout will fit nicely in a 1590BB. Schematic and discussion on FSB here.

Music Man StingRay Preamp

Had several requests for on-board bass preamps and what better place to start than the original StingRay circuit? Simple 2 band-EQ with low current draw and should be small enough to tuck into the control cavity of whatever bass you're wanting to add it to. Other single opamps can be used, but the current draw may increase, draining your 9v battery quicker. For example a TL071 draws 10x the current of the LM4250. A good replacement would be the LT1351.

Barcus-Berry 3000A

Stumbled across this schematic on FSB. It's a buffer/EQ/preamp for peizo pickups, specifically all Barcus-Berry electret microphone systems. I figured most would be building this into an instrument and not a pedal, so all the pots are off-board. If you're planning on running it only off a 9v battery, you cab get away without the power filter cap (47uF) or the polarity protection diode (1N4001).

EWS Tri-Logic Bass Preamp II

Here's a pretty simple but effective bass preamp from EWS. It's a 3-band EQ being pushed by a MOSFET gain stage. Looks like EWS made a version for Xotic with the same name. Not a lot different between the two other than some value changes laid out in this schematic on FSB. I've laid it out for a 125B with top mounted jacks. It runs off an 18v supply so use your favorite charge pump if you want to include that in the pedal.

Sunn 200S Preamp

Here's a simple bass preamp circuit derived from the Sunn 200S using JFETs. It's pretty similar to the Bassman Preamp, but with the EQ section at the end of the circuit instead of the middle. Original S200S amps didn't have the Mid control, but it's kind of necessary IMHO. Bias the JFETs to 4.5v and adjust to taste. Not sure if the BAT85 diodes are necessary as they're not in the Bassman Pre, but I left them in just in case. Also not 100% sure if the below demo follows this schematic exactly, but it should be in the ballpark. Should fit nicely in a 1590B.

Ashbory Bass Preamp

The Ashbory bass was first introduced in 1986 and is/was a half scale (18") fretless travel bass with a piezo pickup and built in preamp. That preamp is essentially a Baxendall tone stack feeding into the volume control, into an op amp based gain stage. I stumbled across the schematic and thought it would be a good addition to the library. Should fit nicely in a 1590B, or you could wire it into a bass.

Catalinbread VariOboost

Here's an older design from Catalinbread, but an interesting design as usual. It's a preamp/boost with a wide range of tone shaping capabilities. Schematic can be found here.

TC Electronic Integrated Preamp

Here's a loud one for you (I am not responsible for any blown speakers that may happen as a result of you building this thing! haha)! It's a popular preamp and used as a booster by the metal band Meshuggah. It apparently sounds best run at 18v. I didn't include an onboard charge pump since I know a lot of you prefer different methods for that. Should be plenty of room in a 1590B for a daughter board with your preferred charge pump. Schematic can be found here.

iRig Preamp

Got several requests for this one. Basically, it's small preamp to plug into a mobile device for use with apps like iRig. Pretty simple circuit. Shouldn't be hard to fit in a 1590a or even smaller since you don't need to include a footswitch.

Tiger Pre-Amp

If you're a Dead Head, you'll probably be interested in this one. It's the pre-amp from Jerry Garcia's Tiger guitar used from '79-'89 and built by Doug Irwin. It's a unity gain buffer to prevent signal loss with long cables. It can be built into a guitar like the original or into a 1590A. Other single op-amps can be used instead of the LF356N (TL071, NE5534, etc).

EchoPlex Preamp

The EchoPlex Preamp emulates the input stage on the old EchoPlex EP-3. It provides up to 11dB of gain and is mostly used as an always on pedal to sweeten the user's tone. If you want to add the volume control, use a 500k pot and connect lug 1 at the junction of the 100n cap, 220k and 100k resistors, and run lug 2 to ground. This also works really well when running at 18v. Schematic for reference can be found here.