Design Challenge #2

zgrav

Well-known member
Anyone built there CDB cd4007 overdrive yet?

I still have several boards available, don't be shy about asking! (Also: I think I'm going to make a revision that additionally has space for a surface mount Q1, allowing you to use either a through-hole or SMD transistor. If you're not afraid of SMD soldering, the SMD J201 seems to be readily available.)

Looks like I have band rehearsal on Thursday, so hopefully I'll soon have a report on using it in a live mix.
Hey Matt G - if you can send me a board I'd like to give this a try as well. I'lll send you a message.
 

zgrav

Well-known member
MattG was kind enough to send me a couple of the PCBs and I put one together this week using the suggested alternate values. Easily blows away any of the 4049 fuzz boxes I have built in the past. Very smooth the the three tone controls are very responsive. Haven't had much time to experiment with the tone controls because I try out a setting and leave it there for a while.

Here are a couple of build pics. Since I had a nice Bismuth color box I called it the PeptOverdrive.

peptoverdirve pic2.jpg peptoverdirve pic1.jpg
 

Chuck D. Bones

Circuit Wizard
Great design, great board, great build! ;)

The tone controls are different from the standard Fender/Marshall tone stack. First and foremost, the tone controls do not interact like they do in the Fender/Marshall tone stack. The BASS control works like the Bass control on the Timmy or the Tight control on a Thermionic. The MID is an active cut/boost. The TREBLE control is a bass/treble balance control much like a BMP Tone control or the Fender/Marshall Treble control.

Did you have an issue dialing in the JFET bias? What is the drain voltage?
 

Sturdag Lagernathy

Active member
Great build! I've got a few projects to finish ahead of this, but I can hardly wait!

I was looking through some old breadboards the other day, and one had 3 4007's on it! I think it's a sign!
 

zgrav

Well-known member
Great design, great board, great build! ;)

The tone controls are different from the standard Fender/Marshall tone stack. First and foremost, the tone controls do not interact like they do in the Fender/Marshall tone stack. The BASS control works like the Bass control on the Timmy or the Tight control on a Thermionic. The MID is an active cut/boost. The TREBLE control is a bass/treble balance control much like a BMP Tone control or the Fender/Marshall Treble control.

Did you have an issue dialing in the JFET bias? What is the drain voltage?
Drain voltage is 4.33 I liked the sound as is and did not change anything from the alternate values in the build.
 

MattG

Active member
MattG was kind enough to send me a couple of the PCBs and I put one together this week using the suggested alternate values. Easily blows away any of the 4049 fuzz boxes I have built in the past. Very smooth the the three tone controls are very responsive. Haven't had much time to experiment with the tone controls because I try out a setting and leave it there for a while.

Here are a couple of build pics. Since I had a nice Bismuth color box I called it the PeptOverdrive.

Looks great, thank you for posting! I like the name, too - definitely more family friendly than some of the earlier suggested names! ;)

One small thing I noticed though - on your enclosure, the bass and treble labels are swapped (treble should be on the left, bass on the right). I know that's probably an atypical ordering of tone controls. I was trying to keep the PCB traces as short as possible, and I think I saved a few mm of traces by doing it that way.

I still have a few boards left if anyone else wants to join in on the fun.

I've now used this pedal in a band setting a few times - so far so good! Though to be fair, I'm using it as my "medium-high" gain pedal (drive knob set around 1:00), and not currently doing a lot of songs that call for that. But I certainly don't plan on removing it any time soon.

Chuck, are there other transistors that would work for Q2, the 2n5089? I'm flirting with the idea of doing an all-SMD version, and at least Mouser doesn't have an SMD 2n5089. The PCB fab house I use (JLCPCB) also offers SMD assembly, so I'm thinking maybe this would be a good trial run for that service. I could design the board to work with e.g. Tayda's pre-drilled enclosures, and radically cut down build time.
 

Chuck D. Bones

Circuit Wizard
Any low-noise NPN with HFE > 200 should be fine. A JFET would also work, but we'd have to adjust the resistor values. I just noticed on the schematic there are two Q1's. The BJT should be named Q2.
 

MattG

Active member
Any low-noise NPN with HFE > 200 should be fine. A JFET would also work, but we'd have to adjust the resistor values. I just noticed on the schematic there are two Q1's. The BJT should be named Q2.

Awesome, thanks!

Finally got around to the front panel graphics, such as they are...

Note that Chuck's build is with the v1 PCB, so his bass-mid-treble labels are correct. The v1 PCB was the prototype (also has some of the pots wired backwards). My two builds I posted in this thread, and all the PCBs I sent out, are v1.2, and the position of the treble and bass pots was swapped from v1.

I'm still working on improving the process.

I think it looks really good! I assume that's some kind of stamping process? The (commercial) Fairfield pedals have a similar aesthetic. Certainly looks better than what I did with the label maker!
 

Chuck D. Bones

Circuit Wizard
Thanks, Matt.
Yup, hand-stamped with steel stamps, engineer's mallet and a home-brew anvil. About 1/2 way thru the top row I improved the anvil and clamped the box in place so it didn't jump around between whacks. This one was good enough, next one will be better.

As Matt said, this was a v1 board, had to work around some minor issues that were all fixed in v1.2.
 
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MattG

Active member
Bump... anyone else built theirs yet? @zgrav - any thoughts on the one you built?

Also, I still have a few boards left if anyone else wants them!

I've used mine in several practices now, one backyard party, across several different amps. I'm still enjoying it!
 

zgrav

Well-known member
Bump... anyone else built theirs yet? @zgrav - any thoughts on the one you built?

Also, I still have a few boards left if anyone else wants them!

I've used mine in several practices now, one backyard party, across several different amps. I'm still enjoying it!
I have left my "PeptOverdrive" on my board and usually leave it on at a relatively low gain setting to fatten the signal. It has tons more character than any 4049 IC fuzz I have made over the years.
 

Sturdag Lagernathy

Active member
Built mine! Only played with it for an hour or so, so I'll have more to say soon. First impressions are great! Definitely a great drive. I'd say more British than American sounding? Great range on all controls. Lots crunch if you want it. I used the modified components.
 

MattG

Active member
I finally got to play this overdrive through my own amp at volume this past weekend... Thus far I've been using my amp at "family friendly" volumes, or various other random amps at rehearsals. I like how it sounds across all amps, but my own amp cranked up a bit - I feel that's the best sound yet. My main amp is a Trinity Triwatt, which is essentially a Hiwatt DR103/DR504 preamp with a more modest 2x6v6 (22ish watts) power section (I built it from the kit, in a 1x12 combo, using the Reeves Vintage Purple speaker). Of course it could just be "baby bias" - I fully admit to having a preference for the stuff I built myself. But whatever the reason, it sounded great to me!

@Chuck D. Bones - when you were designing this, did you happen to generate a frequency response graph via simulation, perhaps a few with the tone knobs at various locations? I'm kind of curious how my aural perception meshes with the actual sonics.
 

Chuck D. Bones

Circuit Wizard
Bass control sweep. Mid at noon. This is observed at the output of the 2nd stage, going into the distortion stage.
5-knob version - bass control sweep.png

Mid control sweep. Bass at noon. This is observed at the output of the 2nd stage, going into the distortion stage.
5-knob version - mid control sweep.png

Treble control sweep. This is the freq response of the treble control only. In other words, it's the difference between the distortion stage output and the pedal output.

5-knob version - treble control sweep.png

Gain control sweep. The Gain control affects the freq response a bit. This is the end-to-end freq response with Bass, Mid and Treble all at noon.
5-knob version - gain control sweep.png

The max gain is 56dB, making this is a low-to-medium gain pedal. It can push an amp pretty well, increasing the overall distortion and compression.

If you want more gain, then you need to build the CMOS Distortion Deluxe, AKA Harmonic Overdrive Experience.
 

lrgaraujo

Member
Hey Chuck, that's a super nice design! Are you familiar with the Lab Series L3 amp? The preamp shares some similarities with your design (jfet input, cd4007 gain), but runs on -15V, positive ground. Do you have any idea why the negative voltage would be preferred?
 
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