5th Gear Overdrive

Joecool85 · January 13, 2006, 12:41:16 PM

This is my newly designed pedal schematic. It gives a pretty mean distortion when cranked, and a good strong regular OD when turned down. Tell me what you guys think if you build it. I've put about 3 hours of play time on mine.

DDD · January 13, 2006, 12:59:47 PM

1. 1N914 simply shunt LEDs, so LEDs are absolutely "closed" all the time. Fell free to cut the LEDs out of the cicuit.
2. Two similar trannies in parallel - why? To have more noise? One BJT is enough for the circuit.
3. Put 5k pot in emitter of Q1 Instead of R1 500k pot in the input path - it will give you less noise and more posibilities to vary sound coloration.

Joecool85 · January 13, 2006, 02:04:16 PM

I tried having a 5k linear pot off the emitter of Q1 and didn't like how it shuts down the circuit around 1/4 turn of the knob...I think this could be solved by connecting lugs 1 and 2 together though. As far as the LEDs go, it gives it a stronger sound, more grunt. I'm no electrical engineer, so I couldn't tell you why. I just like it. And as far as having two trannies in parallel, I did it because I thought it was an interesting idea and I hadn't seen it done before.

David · January 13, 2006, 02:11:02 PM

Quote from: DDD on January 13, 2006, 12:59:47 PM
1. 1N914 simply shunt LEDs, so LEDs are absolutely "closed" all the time. Fell free to cut the LEDs out of the cicuit.
2. Two similar trannies in parallel - why? To have more noise? One BJT is enough for the circuit.
3. Put 5k pot in emitter of Q1 Instead of R1 500k pot in the input path - it will give you less noise and more posibilities to vary sound coloration.

I believe that MPSA13s are Darlingtons. IIRC, they are BJT as you state. The gain on this thing must be outrageous!

Joecool85 · January 13, 2006, 02:55:12 PM

Quote from: David on January 13, 2006, 02:11:02 PM
The gain on this thing must be outrageous!

It is

chaddhamilton · January 13, 2006, 03:21:21 PM

Joe, how's this circut work with other trannies like 2n50xx? Or will it? I don't have anything in my parts bin but 2n5457's and 2n5089's

Sounds like a real screamer!

Joecool85 · January 13, 2006, 03:32:36 PM

Should work fine with the 2n5089s, I haven't tried it yet though.

Connoisseur of Distortion · January 13, 2006, 10:02:08 PM

holy hell. a one resistor circuit. is nayone else seeing this!!??

that's actually really cool. it looks liek it would have a decent amount of distortion, so i might slap one together.

Joecool85 · January 14, 2006, 08:58:33 AM

Cool, I'd love to have some other people put them together, its an easy build and has tons of usable distortion. Or at least I think so. Of course I've really only played it with 2 different guitars and one amp...the amp being a dean markley k-20 and the guitars being a Hamer "strat" and a Lyon LG-4.

chaddhamilton · January 14, 2006, 03:32:59 PM

Joe, I breadboarded it last night and used the 2n5089's. It's a cool distortion/fuzz sound, but I get alot quick decay and splatter when letting single notes ring out... Any idea on the voltages for each pin? Joe, do you get the splatter with the trannies you are using?

I goofed around with it a bit. I sub'd the led's with 1n914's and also bypassed the 1st diode section. I agree with you joe, the sound of the extra diode section sounds good. Nice work, Joe.

Chadd

Joecool85 · January 14, 2006, 04:41:44 PM

It might just be the 2n5089s. When I had only one diode in each section I got poor decay, after I added in the second one in the opposite direction, it was fine. I would check and make sure you have one going each way. Also, if you turn down the guitar's volume too much, or the 500k audio pot too much, it will have crappy decay.

Awesome that (for the most part) you like it!

MartyMart · January 16, 2006, 06:35:26 AM

Congrats !!
Well it doesn't "look" right, but it works for me

Has to be MPSA13 though, nothing else seems to work "right"
The darlington arrangement "somehow" makes this work and it's
quite a "high gainer" from HB equiped gtr !!
MODS :
You dont need the input pot, gtr vol works fine here, I just placed a 1M to ground here and
also used 33n I/O caps, with a small roll off cap off Q2's collector - 2n2
this just lost the "fizz" for me and is fine.
The LED's dont seem correct, but without them it's a different type of crunch ?
Cheers,
Marty.

EDIT :
Voltage reading for both Q1/Q2
C 1.26
B 1.12
E 0.00

Paul Perry (Frostwave) · January 16, 2006, 06:57:37 AM

Putting transistors in parallel should DECREASE noise (ignoring what may happen because of changed input impedances) because, the signal adds at each output, while the noise (being random & independant on each transistor) cancels to some extent.
The back to back diodes must give some interesting distortion (think of the bias changing with the signal level..).
I don't personally think the doubling would do much, but I guess it is up to people who build it to say!!
Congrats, unless we get more weird stuff tried out, there isn't anything new going to turn up.

MartyMart · January 16, 2006, 07:40:52 AM

Well, you can "remove" either Q1 or Q2 and it works 98% as well as with both !
If you leave just Q2 in place, Dist seems a tad softer
If you leave just Q1 in place, there's a tad more "hard spank" to the Dist ....
So, make it with one MPSA13 and switch between diodes

In both these cases the LED's and the 4148's are still in circuit ...

WIERD ?

MM.

Joecool85 · January 16, 2006, 09:03:21 AM

Wow, this is great stuff guys, good to here you are trying out my stuff/modding it. I've been thinking about ditching the input pot, its not amazingly effective anyway. And thank you Paul, I purposely did something strange/out of the norm just to see what would happen, and it came out pretty cool. I just wanted to add a little something to the community, and when I came up with this, I had to share. Now I'm going to have to try some of your mods on my pedal

DDD · January 16, 2006, 11:24:26 AM

Wow!
Actually weird thing!

pyrop · January 17, 2006, 02:51:16 AM

NICE!!! I just threw it together on a breadboard and it sounds great, good stuff Joe!!

I didn't use the pot on the input but added a 1M resister from the input to ground before the input cap which i changed to 0.033uf other than that is as per your schem.
I'm gunna try some other mods then it's off to the perf.
Maybe add a 3way switch ie. Q1 on Q2 off, Q1 off Q2 on, Q1 & Q2 on?

pyrop

Joecool85 · January 17, 2006, 11:24:50 AM

Thanks pyrop. I haven't tried it with .033uF caps, but I did try it with .1, .047, .022, and 0.01. The difference between 0.047 and 0.022 was relatively minor, but I liked the smaller cap sound.

Good to see people actually building this, I figured a few people might look at the schematic and comment, but to actually have people build it is a big thing for me :-) And the fact that you guys like it helps too!

I'm working on designing a metal effect, but so far only have it sketched out on paper. When I finish drawing it and test it a little I'll release that schematic too.

MartyMart · January 17, 2006, 11:53:48 AM

Quote from: Joecool85 on January 17, 2006, 11:24:50 AM

Good to see people actually building this, I figured a few people might look at the schematic and comment, but to actually have people build it is a big thing for me :-) And the fact that you guys like it helps too!

I would re-draw this as a 1 transistor version, use two 1N4148's ( like second stage )
Having played wirh it for a while, this is about 98% of the sound, with half the parts
That makes a quite special "tiny" circuit, you could fit it in almost any small box !

Cheers,
Marty.

Joecool85 · January 17, 2006, 02:17:55 PM

I might redraw it as that for a simple version, but I like the full version, it just don't have the same bite with one tranny (to me.)

Also, did you use 1n4148s? I had listed using 1n914s in my schematic, so I'm not sure, maybe those sound different.

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5th Gear Overdrive