Per request. A DIY project posted by Dylan159 at FSB a while back. It is based on Bajaman's EVH OD but tweaked and simplified. Schematic and more info HERE.
Per request. A DIY project posted by Dylan159 at FSB a while back. It is based on Bajaman's EVH OD but tweaked and simplified. Schematic and more info HERE.
Layout checked with the schem, should be good to go. I'll give it a try within a week or so, thanks Anders
ReplyDeleteI don't remember how you number the switch leg.
ReplyDeleteLike this ?
6 3
5 2
4 1
Ok checked with the schem, this is the right numbering.
DeleteI have to check my build, one position of the switch is dead silent, the other one buzzes (all controls seem to work fine)
Hey Denis, sorry for the late reply. Have a very limited acces to the blog due to lots of work...
DeleteYes, your numbering should work but I always look at the lugs like this:
1 4
2 5
3 6
Thanks, so they are the same ;-)
DeleteHi Fuzzhead
DeleteDo you number DPDT switches like that in all your layouts? I'm used to other sites using the numbering:
1 6
2 5
3 4
I built the Timmy v3 and assumed it was like I just indicated. So did you use the
1 4
2 5
3 6
there too?
Thanks
Yes, I always use this lug numbering:
Delete1 4
2 5
3 6
Ok. I'll go back to the Timmy and swap 4 and 6.
DeleteThanks for the reply!
Now that i think about it more, I think I was confusing the numbering of an opamp with switches.
Delete1 8
2 7
3 6
4 5
i think the switches are done elsewhere as you indicated here...
So...the switch leg numbering on the schematic is
ReplyDelete1 2
3 4
5 6
I made the modification and now the circuit works...or so
When the tone controls are bypassed, it sounds as it should, but when engaged, almost all the output is lost, I can barely hear the distortion and have to really push the volume on the amp.
I checked the layout 3 or 4 times and can't see anything wrong, as for my build
On a side note, the led lights in tone defeat mode even when the effect is bypassed. weird... (it never light when the tone is active)
I'm having trouble translating the schematic to the diagram, so I apologize if I'm missing this, but it seems there are some errors. If you trace the volume 3 back, it crosses the 10uF, and is tied to pin 7 of the IC. That's not necessarily a problem (the schematic uses pin 14, but it could be moved), but it looks like pin 7 is directly tied to one of the LEDs, which I believe it shouldn't be. There's no 1k resistor to the virtual reference voltage, and then I just get super confused from there.
DeleteIt may just need a cut between pin 7 and the LED? Like under the 1M resistor? That might be part of it.
DeleteYep, very well spotted ! Trace cut missing between pin 7 and LED
DeleteI added the trace on my board, put back the original switch wiring and everything works as it should, so this is verified with the added cut.
Only downside is that with the tone switch engaged, it squeals as hell !
Does it squeal all the time, or only with the gain dimed?
DeleteYes almost all the time
DeleteThis comment has been removed by the author.
DeleteI have a project that was doing that, and for me it was increasing the value of the power filter cap. It's definitely not a guarantee, and I see this design has filter caps on both the 9v and the reference voltage, which is good. It's possible that increasing the value might solve it, or you might need a different cap, as I've heard that identical value caps of different brands will handle oscillating sound differently. It's also possible that none of it will solve that, so I apologize. If you can, try running it off of a 9v battery. if the issue goes away, that makes it much more likely that it's a power filter issue. I could keep speculating, but it wouldn't be helpful.
DeleteThanks for the tip, always helpfull, I will try to play with these power filter caps.
DeleteBut meanwhile, I played with that 10µf output cap and tried a few lower values (it sounded a little too fat for my taste). Well, 1µf did the trick, exactly what I have in mind when it's about brown sound. I play it with the tone controls bypassed and with that modification it sounds fucking amazing, and honestly, no need for a tone stack, it nails that EVH sound !
So, I think I will remove the tone stack and its dedicated parts, the switch and box it with only volume and gain.
I think a simplfied layout like this would be totally worth it ;-)
You guys like this one? Pretty high gain?
DeleteThanks
Not a high gain pedal per say, but yes enough gain for what it's supposed to do, no need to boost it IMO (and I only played it at low volume)
DeleteCool. I find the older I get, the less gain I need/want. You can cover up a lot of bad technique with high gain ( speaking from personal experience ). So I try to keep the gain down from max and concentrate on form ( part of the time anyway....).
DeleteThanks for the reply
After taking some time tweaking the circuit, here is what I ended with:
ReplyDelete- Removed completly the tone stack with its parts (C3, C4, R3, R8). I put a 220k resistor between C2 and C7 (originally Tone 2-3)
- Changed the gain pot for a 5k log which gives a much better sweep (before it was like 0 or 1)
- When you roll back the gain pot, the sound brightens, which is nice, so I put that C9 output cap on a switch with 10µf and 2,2µf and that will be my tone control.
I will box it like that, it sounds great, no oscillations at all. It also cleans nicely with the guitar volume pot
Cheers
If you don't want the tone stack, you can remove c2 and the 220k altogether, just go from the diode node to the 100n.
DeleteThe gain pot value does a few things, including changing cutoffs or attenuation for all three filters in that part. I'd say the reduction in total gain and increased control are almost a side effect of it being in series with a 10k resistor (acts almost like a stopper). If you like the change that's good!
The output capacitor shouldn't affect the frequency response at all, it's usually big to give a nice and low output impedance at all audio frequencies. To be able to hear a difference with the 2.2u you'd have to plug into something with just a few k of input impedance! It's an unpredictable and suboptimal way to cut bass anyway, you can try instead to make the last recovery/buffer stage shelf some bass.
Would anyone send a demo ?
ReplyDeleteThanks for making a vero for it. Looks good! maybe a bit too wide to fit horizontally in a 1590B but it should be fine sideways. I hope it gets verified soon but I'll link to it in the thread anyway.
ReplyDeleteNitpicking time: since I've distributed the schematic under a share-alike license, I think you should use the same one for your layout since it's derived from it. No worries if you don't, especially if it's difficult to edit the post, since I can't think of many things that could go wrong with a vero layout, but I still think it's better for you too.
Thanks again!
I traced the layout with the schematic and it seems ok to me.
ReplyDeleteToday it's still tagged as unverified.
What did solve the squeal issue? Power filtering adding or the tone stack removing?
I built this without the tone stack, the board is smaller 2 rows now and was a simple and fast diy build. I can get really good tones, however there's a very loud noise. Maybe the tl074 is the problem as the original circuit was built round tl062? Any suggestions?
ReplyDeleteOk, it's my fault again, the circuit needs to be properly grounded as it's catching noise very easily. As a replacement of tl074 I could recommend low powered lm324n or possibly tl064 but I couldn't find and test the later one. It's nearly good as a bajaman pedal that I build before with much bigger effort. thanks Dylan for your time designing it. Is there any chance since it's called Mini EVH that the tonestack could be reduced to one knob? it's over my skills to design it. thanks
Delete