Tag Archives: circuit

DOD FX55B SupraDistortion – BigBuff Mod


Here’s another in a line now of DOD pedal mods. For this FX55B, I decided to go for more of a BigMuff sound. Playing around with this pedal initially, I found it to be like most mass-produced distortion/fuzz effects. It had a very thin sound and that notorious volume drop that you may have heard on a high-school band’s first album. The lows were almost non-existent when the effect was engaged. I found the following schematic and, with a few simple changes, came out with a distortion pedal with considerable gain, massive lows, and a smoother, more rounded square wave.


Overall, the idea here was to get more from the pedal by employing some germanium to smooth out the harshness and to increase the overall output. The output is now considerably higher as long as the tone knob is set closer to 10 o’clock. At noon, the mixing is practically useless. At the 4 o’clock position, you get more of a thin, trash punk type of sound with an excessive noise floor. The sound sample demonstrates the effect with the tone set at about 10:30-11 and first contrasts the distortion setting. The third set shows off the tone below 10 o’clock. The last set shows what the tone does when you sweep through it.

Class AB amplifier test


this was an attempt at designing a simple transformer-less class AB amplifier using two BJT power transistors. i setup the USB fan to protect against thermal runaway and cool off the transistors during operation. it took me looking over several schematics to realize that the the emitters of both the PNP and NPN transistors were tied together. the collector of the PNP (TIP32C) is grounded which is obvious! the synapses just weren’t seeing the PNP symbol as upside down. it’s definitely something i’ll have to work on. i’d like at some point to have a nice 40W amp based on a similar configuration.

LFO modulated simple VCF


this is a rough draft of a circuit i’ve been working on based of the Simple VCF circuit floating out there. a big thanks to the original author for that. i’m sure there are some mistakes in here. it’s an odd one for sure, but it works on the breadboard. the opamp is a TL072. square-wave input from the generator comes out pretty sine-wave like which is what is desired. the output is a little noisy, but i will work that out with time.

MOSFET baritone (guitar/bass) preamp

ok, so here’s a preamp design that i’m working on at the moment. it’s meant to be an amplifier simulator for my Gretsch Baritone G5265. i was impressed with the AMZ Booster using a single transistor and used a ’59 Bassman simulator (which uses J201s) as a loose guide. i’m looking to use it as a pre so i can run the baritone through an SS amp without it sounding dinky. it’s pretty experimental still, and i’ll most likely add a tone stack after Q2.

since the schematic post, i wanted to point out some potential sources of change. Q3 should be marked as a 2N4401 and not a 2N3904. both will probably work, but i originally used a 2N4401 (thinking it was a 2N2222A). i also did try out a 2N2222A but didn’t really like it as much (more beefy and less definition). i’ve been experimenting with MPF102s in the Q3 position today which definitely have a more pronounced high-end sparkle which is probably better suited for guitar. i’m going to try it out in the Q1 and Q2 positions as well just to see.

also, D1 is a 1N914. to be honest, i don’t hear any tonal effect with or without it. i saw a similar connection in the AMZ Booster schematic, but i’m not sure of it’s function yet.

initial test of a modulated PT2399 circuit…

a breadboard version of some PT2399 modifications i’ve been working on. there are a lot of DIY schematics that utilize the PT2399 (Magnus Modulus, Echo Base delay, Rebote, etc.). i’ve been interested at trying my hand at modulation techniques recently. i made a simple LFO circuit based on the findings mentioned in a previous post. i used some techniques out lined in some of the schematics floating out there to attempt to modulate the delay time of the chip. i wouldn’t say i’ve got it to work perfectly, but it’s definitely doing what i had hoped.

PT2399 build…

this is an older build now, but i wanted to post it while i’ve been on the subject to record the process. believe it or not, i still have some work to do on this one. i used a TL082 as a buffer for the mixing circuit. getting the gain set to my taste has been the toughest part. this one (unlike the last) is a bit low. it will all come in due time though. i’ve produced two solid builds this week (though really just debugging this one and one from scratch), and i’ll consider that a productive week.

ngSpice: single frequency FM modulated signal generation

ever wanted to see how that 2N2222 might hold up as a linear RF amplifier? here’s a handy feature of ngSpice that i found recently. i’m rather new to ngSpice and at first was somewhat frustrated by its differences from other SPICE variants. however, i’ve earned a deep appreciation for it and its integration with the gEDA suite.

V1 n1 0 sffm(2 24 10k 5 1k)
.tran 0.01ms 2ms
.plot n1

the above code generates the waveform seen above. the corresponding values in the sffm() function run something like this.

Parameters Default value Unit
Vo (offset) Ampere or Volt
Va (amplitude) Ampere or Volt
Fc (carrier frequency) 1/Tstop Hz (Hertz)
Mi (modulation index)
Fs (modulation frequency) 1/Tstop Hz (Hertz)

Boss Tremolo TR-2 w/ C4 Mod +Gain Boost

This little guy is currently on eBay. I always thought that this tremolo wasn’t bad, but the volume drop was insatiable and drove me nuts sometimes. I thought I would try modding this one by cutting out the C4 cap (a 0.1uF bypass cap) which is the alleged cause of the gain loss. It is, but not without good reason. It does keep the effect sounding smooth and really clean. Removing the cap also opens up those capped frequencies which some people report a more warm and/or harsh tremolo tone. I enjoyed the more dramatic effect of the pedal myself, and decided to make it even more so by substituting the 10k ohm resistor before the non-inverting terminal of the first opamp for a 4.7k. This added a nice volume boost which gives the tremolo more cut especially when combined with heavy reverb or a washy delay. We’ll see if anyone decides to buy it. I think it’s a huge upgrade from the original sound.

5E3: Schematics and Ideas

I’m hoping this will clear things up for the night. Practical matters have brought about the decision to build a tube amplifier. In this case, I’m going to get a WeberVST kit as not to go it solo on the first attempt. The winner of much debate as to which circuit to start with is the ever popular 5E3, a Fender ’57 Tweed Deluxe circuit.

Unfortunately, this circuit isn’t quite ideal. The goal for our prototype is going to be about balancing loudness with clarity and transforming its bluesy rock tone into something a little smoother and less aggressive. We’re going to attempt lowering the gain in the preamp by using tubes with a lower gain factor and increasing wattage in the output stage which will include substituting some 6L6 variety for the standard 6V6s. The use of two separate volume controls seems to be pointless for our purposes as well. I think I’ll probably wind up setting up a treble and bass tone stack by dumping one of the volume pots.

Anyone care to buy a Marshall 2×12 4102?