Trying to get this verified but I'm having issues. I'm getting sound, it just doesn't sound good. Have to crank the volume to get anything. I think my problem lies in my jfets. My remaining through holes may be junk so I soldered up some smd's and its better but still not right. One thing I know is that the Normal gain is wired backwards. I'll keep checkin for mistakes on my end.
Do you have any PF5102 lying around? They're my"to go" J FETs ever since J201 dissapeared. Works really good in most higher gain amp emulator circuits.
Tried 5102's. Same issue but worse. Have to crank the volume to get anywhere near unity and setting the trimpots in the "best position" still sounds like a unbiased mess. Dunno. Gonna take a step away and look it over again after a break. Maybe I'll find an error but so far I can't. Frustrating one.
Sounds like a good idea to pause to get some fresh eyes. I've been over the schem and I can't find any issues. https://4.bp.blogspot.com/-D6inZrGI75w/Whx10_gxOxI/AAAAAAAAE8A/Qjntz3_fRUQ_uqHKsBbFt2MT2nwWV6HRACLcBGAs/s1600/Sunn-Model-T-preamp.gif
Does both of the channels sounds misbiased? Does the boost section work?
Check out the Sun Model T Preamp over at tagboard, the notes say to bias Q1 and Q2 to 6.5V and Q3 to 5V. It's the only way I was able to get the Laney Supergroup emulator working properly. This is a similar design.
I didn't feel like messing with those pain in the ass smd 201's again so I just used 5457's. They're biased to 4.5v. I see that you said 5102's are a nice sub, I've got some of those as well. I'll check them out and report back. I reused an old enclosure that had 10 pots, that's why there are double LED sets. The output is flirting with unity, might be right at it or slightly below. I'm going to tuck in an LPB-1 to help it out. Sounds damn good though. Nice work on the layout.
The 100k trimpot on the top right is a pot called "Boost" on the schematic, lug 2 of which is routed to Boost SW 4. That might be a remnant from when that was offboard.
I think the 1M resistor on the input to the Boost stage (R81) is missing. That might lower the input impedance, but that may affect the sound (depending on your pickups).
If anybody is having problems with the switch popping, it might be worth adding a 1M resistor to ground off Boost SW 1.
Built this today, but I'm not getting any sound through. I can bias Q1 and Q2 fine, but not Q3. I've been over the board a few times, making sure all my cuts, links, and parts are in the right place, and haven't found any solder bridges. I noticed on the pictures MTK shared that his 22uf capacitor seems to be flipped from what the layout shows, could this be a problem?
I tried a few different ones, same problem. Q1 and Q2 bias fine, but Q3 does not. The voltage reads 9V on one end of the trimmer turn, and between 8.5 and 8.3V depending on what JFET I have there. I've gone over it multiple times, but I really can't see what/if I did anything wrong. I must have done something wrong because MTK's works...
Yeah, I never got mine working right and I tried a bunch of different through hole and smd jfets. I still have it, I'll dig it up and go over it again when I get some time.
It looks like at least one other guy had problems with this so you may not have done anything wrong. Sometimes there may be a miscommunication or a tiny error that screws everything up. The schematic is listed by fuzzhead above in the comments. I looked at the stuff around Q3 and didn't see a fault but I just glanced at it. I know how frustrating it is when you can't get a circuit to wake up.
So it turns out, I'm an idiot... After cutting the tracks several times, I finally tested continuity, and lo and behold, there was an unseen connection between rows 3 and 4 somehow. I went over that area again, and ended up having to go fairly deep before continuity was finally lost.
tl;dr This layout is perfect, and this pedal is a firebreather.
I was getting lackluster results until I saw a comment above stating that the connection between Boost Switch 2 and 4 was wrong. Now it sounds like MTK's demo. Pretty crazy circuit. I biased by ear when the recommended voltages didn't sound so great. Oh, and the 100K trim controls boost volume. Thanks.
I see 9 links, right? Starting this, hopefully I'll be able to verify it.
ReplyDeleteYep, 9 links it is. Layyout updated.
Delete👍
ReplyDeleteTrying to get this verified but I'm having issues. I'm getting sound, it just doesn't sound good. Have to crank the volume to get anything. I think my problem lies in my jfets. My remaining through holes may be junk so I soldered up some smd's and its better but still not right. One thing I know is that the Normal gain is wired backwards. I'll keep checkin for mistakes on my end.
ReplyDeleteScratch that. Wiring is fine, my mistake. Still can't find fault in my build. Gonna order some more jfet adapters and see if I can get this goin.
ReplyDeleteDo you have any PF5102 lying around? They're my"to go" J FETs ever since J201 dissapeared. Works really good in most higher gain amp emulator circuits.
DeleteI actually have a bunch. Gonna try em right now.
ReplyDeleteTried 5102's. Same issue but worse. Have to crank the volume to get anywhere near unity and setting the trimpots in the "best position" still sounds like a unbiased mess. Dunno. Gonna take a step away and look it over again after a break. Maybe I'll find an error but so far I can't. Frustrating one.
ReplyDeleteSounds like a good idea to pause to get some fresh eyes. I've been over the schem and I can't find any issues.
Deletehttps://4.bp.blogspot.com/-D6inZrGI75w/Whx10_gxOxI/AAAAAAAAE8A/Qjntz3_fRUQ_uqHKsBbFt2MT2nwWV6HRACLcBGAs/s1600/Sunn-Model-T-preamp.gif
Does both of the channels sounds misbiased? Does the boost section work?
Yeah, boost works and so do both channels. Im sure its my mistake somewhere. Hopefully it'll become obvious.
ReplyDeleteHey mulekicker! Did you ever figure your issue out?? I feel like I’m experiencing the same problem!
DeleteCheck out the Sun Model T Preamp over at tagboard, the notes say to bias Q1 and Q2 to 6.5V and Q3 to 5V. It's the only way I was able to get the Laney Supergroup emulator working properly. This is a similar design.
ReplyDeleteTag it, man. It jams!
ReplyDeleteI didn't feel like messing with those pain in the ass smd 201's again so I just used 5457's. They're biased to 4.5v. I see that you said 5102's are a nice sub, I've got some of those as well. I'll check them out and report back. I reused an old enclosure that had 10 pots, that's why there are double LED sets. The output is flirting with unity, might be right at it or slightly below. I'm going to tuck in an LPB-1 to help it out. Sounds damn good though. Nice work on the layout.
Demo - https://www.youtube.com/watch?v=GGqgVS54RGQ
Build - https://imgur.com/a/oCfpx7Q
Top man, I'll tag it. That sounds really good, especially with bthe booster kicked in. Good to know that 2N5457's works as well.
DeleteDude... Running the Megalith into the Model T is magical. Heavy as hell and super quiet. Solid combo.
Deletehttps://www.youtube.com/watch?v=nHIRtkQN9IU
Went with the Black Eye Galaxy for the T graphic.
https://i.imgur.com/xmD6ruZ.jpg
https://i.imgur.com/XMqKeAV.jpg
Just built this and found a mistake in the layout.. there’s no connection between boost sw2 and boost sw4.
ReplyDeleteThere shouldn't be a connection between sw2 and sw4, it will bypass bosst section in both switch settings.
DeleteUnless I understood ‘boost 2 to boost sw4’ incorrectly?
ReplyDeleteThe 100k trimpot on the top right is a pot called "Boost" on the schematic, lug 2 of which is routed to Boost SW 4. That might be a remnant from when that was offboard.
DeleteSchematic: https://4.bp.blogspot.com/-D6inZrGI75w/Whx10_gxOxI/AAAAAAAAE8A/Qjntz3_fRUQ_uqHKsBbFt2MT2nwWV6HRACLcBGAs/s1600/Sunn-Model-T-preamp.gif
There should be no connection between Boost SW 2 and Boost SW 4.
I think the 1M resistor on the input to the Boost stage (R81) is missing. That might lower the input impedance, but that may affect the sound (depending on your pickups).
ReplyDeleteIf anybody is having problems with the switch popping, it might be worth adding a 1M resistor to ground off Boost SW 1.
Built this today, but I'm not getting any sound through. I can bias Q1 and Q2 fine, but not Q3. I've been over the board a few times, making sure all my cuts, links, and parts are in the right place, and haven't found any solder bridges. I noticed on the pictures MTK shared that his 22uf capacitor seems to be flipped from what the layout shows, could this be a problem?
ReplyDeleteAs I learned recently, FET's are very temperamental. If you have some more, or other similar JFET's you should try them.
ReplyDeleteI tried a few different ones, same problem. Q1 and Q2 bias fine, but Q3 does not. The voltage reads 9V on one end of the trimmer turn, and between 8.5 and 8.3V depending on what JFET I have there. I've gone over it multiple times, but I really can't see what/if I did anything wrong. I must have done something wrong because MTK's works...
DeleteYeah, I never got mine working right and I tried a bunch of different through hole and smd jfets. I still have it, I'll dig it up and go over it again when I get some time.
DeleteIt looks like at least one other guy had problems with this so you may not have done anything wrong. Sometimes there may be a miscommunication or a tiny error that screws everything up. The schematic is listed by fuzzhead above in the comments. I looked at the stuff around Q3 and didn't see a fault but I just glanced at it. I know how frustrating it is when you can't get a circuit to wake up.
ReplyDeleteSo it turns out, I'm an idiot... After cutting the tracks several times, I finally tested continuity, and lo and behold, there was an unseen connection between rows 3 and 4 somehow. I went over that area again, and ended up having to go fairly deep before continuity was finally lost.
ReplyDeletetl;dr
This layout is perfect, and this pedal is a firebreather.
Good to know. I gotta figure out where mine went wrong.
DeleteI'd like to try this myself. I might try it next time have a chance.
ReplyDeleteI was getting lackluster results until I saw a comment above stating that the connection between Boost Switch 2 and 4 was wrong. Now it sounds like MTK's demo. Pretty crazy circuit. I biased by ear when the recommended voltages didn't sound so great. Oh, and the 100K trim controls boost volume. Thanks.
ReplyDeleteCan this be modded to give line level output?
ReplyDelete