Depot Fuzz (EQD Terminal Fuzz)
- Thread starter Kroars
- Start date
Robert
Reverse Engineer
The person who traced the board listed 2N222A not 2N2222A. They were in a TO-92 package and the pinout was backwards compared to a 2N2222A....
So, they are listed as traced, 2N222A and the pinout is printed on the board because of the uncertainty.
I had no luck finding a "2N222A" so I used 2N2222A installed backwards for prototyping and it worked great.
This will be noted in the build docs.
So, they are listed as traced, 2N222A and the pinout is printed on the board because of the uncertainty.
I had no luck finding a "2N222A" so I used 2N2222A installed backwards for prototyping and it worked great.
This will be noted in the build docs.
DigitalZombie
Member
I noticed what might be a couple errors with the Schem/BOM. The Depot/Terminal is basically the Shin Ei Companion With Booster from GGG with the addition of a "Voice" control in the notch filter (which running though the Tone Stack Calculator on the web doesn't seem to do all that much). I believe C3 should be 47n, not 4n7. Also C9 is flipped from how it looks on the GGG schem, but I'm uncertain how much impact this will have. I don't have Terminal in front of me to trace but I'm suspicious that EQD would bother to make those changes.
Robert
Reverse Engineer
The circuit was traced from the photos in this thread on FSB. The capacitor in question was listed as 472, so unless that was an error it's correct.
I've built it and the Voice control definitely works.
I've built it and the Voice control definitely works.
Last edited by a moderator:
DigitalZombie
Member
I still have a hunch that 472 is an error. You can't read the marking in the photos provided, but you can see the massive physical difference compared the the 222 next to it. Just a hunch, though.
chongmagic
Well-known member
Here is the plastic version of the transistor on Small Bear.
smallbear-electronics.mybigcommerce.com
Transistor ATP2222A
Guitar pedals, pedal parts and electronics.
smallbear-electronics.mybigcommerce.com
Chuck D. Bones
Circuit Wizard
I look forward to seeing the schematic.
When you say ‘installed backwards’, do you mean the leg closest to the little tab on the component should be in the collector hole on the PCb and not the emitter? I just completed the build and it doesn’t sound even close to the Terminal, so I must have made a mistake. Thx in advance.
ferdinandstrat
Member
Hey dude, I built the pedal with the 4n7 and it just sounded off, weak and lacking gain all around. Switched the 4n7 to 47nF like DigitalZombie suggested and pedal was brought to life
Gonna +1 this, I also think the OG Terminal may have a 47nF and not a 4.7 - I had a Depot Fuzz I never boxed because it was lacking in gain and body until about 9 or 10 on the “Fuzz” knob (tried with metal can 2N2222s and flipped plastic 2N2222s, same results), but after reading @ferdinandstrat ‘s post I tried it with a 47nF and all of a sudden it’s gainier and properly thick and what I was expecting this thing to sound like based on the demos.
EffectsLayouts also has a 4.7nF on their BoM and schematic, but I’m assuming they’re working from the same FSB trace
giovanni
Well-known member
If I understand the schematic correctly (the first two stages are both collector feedback biased), the cutoff frequency of the high pass filter coupling the output of the first stage to the next is dominated by R3 and C3. If we pick 4n7 for the cap, this leads to something around 1.5KHz, i.e., most low frequencies are cut off. If we pick 47n, we get a more reasonable 150Hz. So once again, based on my understanding of the circuit, 47n seems to make more sense. Also makes me wonder if an event higher cap would improve the frequency response on electric bass.
Last edited:
DigitalZombie
Member
I played around with the values of different caps quite a bit before boxing one up. Going higher than 47n for C3 didn't really do much. Increasing C5 from 3n3 however made quite the difference. I found a 5n6 to really give it some "umph" but anything larger sounded too boomy. I gave it to a friend to try out and the extra low end sounded great through a Fender but didn't play too well on a AC15. Going to try putting the two different values for C5 on a switch.
peatpatrick
New member
I bought this pedal November 2020. It didn't sound right and I realized the resistor values that were silk screened on the board are different then the values listed in the build document. Which is correct? for example r11 in the build document shows 47k but the board says 1M.
peatpatrick
New member
I pulled them all out and put them back in according to the BOM and now it doesn't work at all, so I think your right.
