Any chance you could help me with setting my voltages? Mine sounds spitty/ weird depending on the EQ and I assume the drain voltages have something to do with that. My Q4 stays right around 9 no matter what I try. Does that line up with your experience?
Hello! I am having a few issues with my build and was hoping for some help. I am curious if all the j201 should be set to 4.5 or something else - on mine Q4 seems to stay right around 9v no matter what I turn. The trim by the vol 3 seems to control volume - which I assume it should? Aside from setting the drain voltage I do get signal through and some settings sound ok. Sometimes it’s a bit spitty? Seems like the EQ doesn’t work quite right for me. Sorry to unload all this - just wanted to get some ideas. I think it’s wired up right it’s just acting really funky.
I think you need an overall check, but I can tell you that Q4 is directly connected to the 9v, so that's is right. And the trimpot close to the Volume is a tone control.
Aye! Thanks for the confirmation on those. Any idea what the other drains should be set to? I feel like when I’m sitting with a project it’s hard for me to see what’s wrong... if I would’ve looked for 2 seconds at the power I would’ve noticed it was tied to Q4. Silly me! I may need to come back to it tomorrow and maybe something will jump out at me.
Well, shoot. I finished mine today and I too am getting some weird spitty sounds. I am going to begin by taking some J201s out of a couple of builds where I know they are good and try them here. If that doesn't help,I'll have to get out the fine-toothed comb and go at it. Fairly certain all the components are at least what they should be - I test each component with a DMM before I solder them in just to avoid having to troubleshoot after the fact.
Can you tell me if you used the schematic from FSB? I'd like to just compare against the layout. Not saying its bad since it has been verified but I just wanted to go over it.
There is several schematics with some very small variations out there. I think I used this schematic for the layout: https://www.pedalpcb.com/docs/M800.pdf
Cool. I was going to go to pedalpcb and see if they had a version there. Their schematics are usually ( always? )good. Thanks again. I'll update when I get it fixed. Out with the 10x loupe.....
Fixed! I was missing the small link from F11 to G11. That made it to where the trimmer would not function on Q5 - never moved from 9V. I even replaced the trimmer thinking maybe it was bad. Was comparing the layout to pedal again and I noticed the missing link. Added that and I could bias Q5. It's been a few months since I built anything. I normally have a very strict process where I do the links first, then count them. Then the sockets. Then the resistors, then count them, on with the caps, etc. This time I missed counting the links. I would've caught it had I done my normal count after each section. Everything seems to be working as expected.
I biased all jfets to 4.5 but at that bias setting, the distortion doesn't sound very good throughout the range. I think I am just going to have to bias by ear. Hopefully that will help the sound. I'll let you know after I have time to do that. But the layout is good. I went through that this morning with the schematic - it was a good exercise to see how things come together on these layouts.
Keep at it heartben. Make sure you have that link at F11 to G11 - its easy to miss. When I was comparing my pedal to the layout, I took a high res pic of the pedal so I could enlarge it and look at it side by side with the layout. While I as doing that comparison I noticed the missing link. Maybe that will help.
Well....I tried biasing by ear. I still can't get it to be non splatty. If the gain is maxed out, it sounds kind of ok, but nothing like the youtube demos. Now that was only after 20 minutes of biasing. I may try a little more. And maybe my j201s are spotty. I have several hundred so I may try a few more just to see if it is the jfets - it very well could be. If I can't get this one to sound ok, it's probably something in my build - heck, I already found my one mistake - there may be more. I'll just rebuild it at some point and report back.
And forgot to mention, the tone controls are kind of ok but they just seem to interact with the splat. I will definitely try a few more jfets just to see if they make any difference. Nothing to lose. Sorry to not have better news. I'll keep working on it.
Ok. So I kept working on this but could never get it biased so that it didn't have a farty note decay. I even built the JCM Emulator from Sabro's site to see if it acted any differently - basically the same circuit with an added "master volume" between Q4 and Q5. Same issue.
I looked back at the thread on FSB and saw something that I had passed over previously. Someone had posted drain voltages from an actual unit. I biased both to these voltages and the farty decay is 99% gone. Here are the voltages - save yourself some heartache and use them for biasing the drains on this circuit:
Not sure why this circuit is so unforgiving for other values closer to 4.5 - 5V. I've built many of these J201 cascading gain stage circuits and they usually sound fine if you get them close to the 4.5V value.
So use the values above and you will get a great non-farty decay emulator.
Now, the qualification. It really only sounds really good at or near full gain. When I lower the gain to lower settings, the farty decay comes back. I've watched the demos and they often play the pedal at lower gain settings and there is no decay weirdness. So maybe someone else can address that. Going to post this question at FSB and see if anyone has an idea there.
And I tried multiple sets of J201s from different sources and they all exhibit the same behavior.
I would be curious if the original poster who verified this experienced anything close. Maybe he'll read this.
With all that said, I'm glad I built it. Even without the capability to turn down the gain on the pedal, it sounds really good at the top gain setting - and you can lower the volume on your guitar and it cleans up pretty well. Thick and full distortion - I did swap the 680n for a 1uf for a bit more gain - made a pretty big difference. I would recommend that change.
btw, the person who posted the drain voltages on FSB for this was bmxguitarsbmx. I didn't want it to seem like I was taking credit for that. Thanks bmxguitarsbmx on FSB.
Hey man! Just add a cut under P 7 (the input is being fed straight into q3 like it is now) and tag it! Sounds great
ReplyDeleteTop, man! Cut added and layout tagged.
DeleteAny chance you could help me with setting my voltages? Mine sounds spitty/ weird depending on the EQ and I assume the drain voltages have something to do with that. My Q4 stays right around 9 no matter what I try. Does that line up with your experience?
DeleteHello! I am having a few issues with my build and was hoping for some help. I am curious if all the j201 should be set to 4.5 or something else - on mine Q4 seems to stay right around 9v no matter what I turn. The trim by the vol 3 seems to control volume - which I assume it should? Aside from setting the drain voltage I do get signal through and some settings sound ok. Sometimes it’s a bit spitty? Seems like the EQ doesn’t work quite right for me. Sorry to unload all this - just wanted to get some ideas. I think it’s wired up right it’s just acting really funky.
ReplyDeleteI think you need an overall check, but I can tell you that Q4 is directly connected to the 9v, so that's is right. And the trimpot close to the Volume is a tone control.
ReplyDeleteAye! Thanks for the confirmation on those. Any idea what the other drains should be set to? I feel like when I’m sitting with a project it’s hard for me to see what’s wrong... if I would’ve looked for 2 seconds at the power I would’ve noticed it was tied to Q4. Silly me! I may need to come back to it tomorrow and maybe something will jump out at me.
DeleteWell, shoot. I finished mine today and I too am getting some weird spitty sounds. I am going to begin by taking some J201s out of a couple of builds where I know they are good and try them here. If that doesn't help,I'll have to get out the fine-toothed comb and go at it. Fairly certain all the components are at least what they should be - I test each component with a DMM before I solder them in just to avoid having to troubleshoot after the fact.
ReplyDeleteCan you tell me if you used the schematic from FSB? I'd like to just compare against the layout. Not saying its bad since it has been verified but I just wanted to go over it.
I'll try a few things before I give up.
Thanks for the layout
There is several schematics with some very small variations out there.
DeleteI think I used this schematic for the layout:
https://www.pedalpcb.com/docs/M800.pdf
Cool. I was going to go to pedalpcb and see if they had a version there. Their schematics are usually ( always? )good. Thanks again. I'll update when I get it fixed. Out with the 10x loupe.....
DeleteAnd thank you again!
DeleteFixed! I was missing the small link from F11 to G11. That made it to where the trimmer would not function on Q5 - never moved from 9V. I even replaced the trimmer thinking maybe it was bad. Was comparing the layout to pedal again and I noticed the missing link. Added that and I could bias Q5. It's been a few months since I built anything. I normally have a very strict process where I do the links first, then count them. Then the sockets. Then the resistors, then count them, on with the caps, etc. This time I missed counting the links. I would've caught it had I done my normal count after each section. Everything seems to be working as expected.
DeleteI biased all jfets to 4.5 but at that bias setting, the distortion doesn't sound very good throughout the range. I think I am just going to have to bias by ear. Hopefully that will help the sound. I'll let you know after I have time to do that. But the layout is good. I went through that this morning with the schematic - it was a good exercise to see how things come together on these layouts.
Thanks fuzzhead
Keep at it heartben. Make sure you have that link at F11 to G11 - its easy to miss. When I was comparing my pedal to the layout, I took a high res pic of the pedal so I could enlarge it and look at it side by side with the layout. While I as doing that comparison I noticed the missing link. Maybe that will help.
DeleteGreat!
DeleteAnd yeah, I never bias these J FET circuits at 4,5v...it usually sounds bad so tuning by ear works best IMHO.
Well....I tried biasing by ear. I still can't get it to be non splatty. If the gain is maxed out, it sounds kind of ok, but nothing like the youtube demos. Now that was only after 20 minutes of biasing. I may try a little more. And maybe my j201s are spotty. I have several hundred so I may try a few more just to see if it is the jfets - it very well could be. If I can't get this one to sound ok, it's probably something in my build - heck, I already found my one mistake - there may be more. I'll just rebuild it at some point and report back.
DeleteThanks
And forgot to mention, the tone controls are kind of ok but they just seem to interact with the splat. I will definitely try a few more jfets just to see if they make any difference. Nothing to lose. Sorry to not have better news. I'll keep working on it.
DeleteThanks for all your hard work on the layouts.
Ok. So I kept working on this but could never get it biased so that it didn't have a farty note decay. I even built the JCM Emulator from Sabro's site to see if it acted any differently - basically the same circuit with an added "master volume" between Q4 and Q5. Same issue.
ReplyDeleteI looked back at the thread on FSB and saw something that I had passed over previously. Someone had posted drain voltages from an actual unit. I biased both to these voltages and the farty decay is 99% gone. Here are the voltages - save yourself some heartache and use them for biasing the drains on this circuit:
Q1 - 3.742V
Q2 - 3.361V
Q3 - 3.362V
Q4 - 9.45V ( tied directly to 9V supply )
Q5 - 4.03V
Q6 - 3.115V
Not sure why this circuit is so unforgiving for other values closer to 4.5 - 5V. I've built many of these J201 cascading gain stage circuits and they usually sound fine if you get them close to the 4.5V value.
So use the values above and you will get a great non-farty decay emulator.
Now, the qualification. It really only sounds really good at or near full gain. When I lower the gain to lower settings, the farty decay comes back. I've watched the demos and they often play the pedal at lower gain settings and there is no decay weirdness. So maybe someone else can address that. Going to post this question at FSB and see if anyone has an idea there.
And I tried multiple sets of J201s from different sources and they all exhibit the same behavior.
I would be curious if the original poster who verified this experienced anything close. Maybe he'll read this.
With all that said, I'm glad I built it. Even without the capability to turn down the gain on the pedal, it sounds really good at the top gain setting - and you can lower the volume on your guitar and it cleans up pretty well. Thick and full distortion - I did swap the 680n for a 1uf for a bit more gain - made a pretty big difference. I would recommend that change.
Thanks
Tim
Sorry for the long post.....
ReplyDeleteNo, no! Super helpful information you provided. I'm sure it will help other builders who is going to tackling this.
DeleteCheers
Fuzzhead
btw, the person who posted the drain voltages on FSB for this was bmxguitarsbmx. I didn't want it to seem like I was taking credit for that. Thanks bmxguitarsbmx on FSB.
ReplyDeletewhere is presence 1?
ReplyDeleteIt's not connected to anything.
Delete