Monday, July 24, 2017
JHS Twin Twelve V1
Here's the original Twin Twelve from JHS. It's an emulator of the old Silvertone 1484 amp. Like a lot of amp emulators (including their Superbolt) it uses JFETs and an 18v charge pump. The schematic can be found here, and I added the charge pump from JHS's Superbolt. Set the trimmers to around 9v and the adjust as need be. Pots are board mounted as usual and it should fit in a 125B with top mounted jacks nicely.
If I would use a normal 18 volts ac/dc, wich part of circuit i've to remove?
ReplyDeleteIf you're using an 18v DC supply, you'd remove the MAX1044 chip, the 2, 10uF caps, and replace the 2, 5817 diodes with jumpers.
DeleteTnx :)
DeleteHi.Can i use LT1054 in plece of Max1044 (same pinout)?. Thanks for your brillant work!!
ReplyDeleteYeah that should work. And you're welcome!
DeleteOh, you'll want to leave pin 1 disconnected with the 1054.
DeleteI'll try, thanks!!
DeleteI have this populated on my bench right now.....and it is not quite working. I think the 10uF closest to Q2 should be connected to the strip side of the other 5817 diode (I think this is what happens in your superbolt layout and what the 1044 data sheet says). As drawn above I think the IC chip heats up and dies pretty quick.
ReplyDeleteI think something else is still wrong with the power doubler in at least my build though; I can get a pretty clean low output signal out of the effect without the IC in place (biasing the J201's to 4.5v), but when I insert the chip after moving the 10uF cap as I note above (and rebias the transistors) the sounds stops.
So, is it verified now?
ReplyDeleteYes, same with T-funk, the charge pump section is wrong. Now the charge pump section is working, and try to build the rest
ReplyDeleteDone! Except error in the charge pump section its verified. Nice one dude 🤘
ReplyDeleteClarify for me what's wrong with the charge pump. Either I'm having major brain farts or the schematic I used is wrong. haha
DeleteActually T-Funk spot it first :
DeleteI think the 10uF closest to Q2 should be connected to the strip side of the other 5817 diode (I think this is what happens in your superbolt layout and what the 1044 data sheet says). As drawn above I think the IC chip heats up and dies pretty quick.
Finally got around to fixing it. Should be all good now.
DeleteHi, is it verified?. Thanks!!
ReplyDeleteBump.is it verified? Thanks
ReplyDeleteIs there any proof that this is the real JHS Twin Twelve schematic?
ReplyDeleteThe schematic that you linked to comes from the TagboardEffects forum. If you do a search for "Silvertone," it's the thread titled "Silvertone 1485/Twin Twelve." That thread traces back to a post on freestompboxes.org titled "eighty seven percent - De Stijl."
That circuit is an individual's attempt at doing a tube -> FET conversion of a Silvertone amplifier circuit. I have seen no evidence that this is the actual schematic for the JHS Twin Twelve.
However, I'm glad to be proven wrong, if someone can provide a source.
It's not confirmed if this is the circuit JHS used, but at the very least it's a very well educated guess. It's close enough for me. YMMV
DeleteHello coul you please post the corrected version? Thanks in advance!
ReplyDeleteIt's has been updated. See above.
DeleteHello, I'm trying to bias the j201s but the trimmers just seem to be ruling nothing, the only thing I can do is going from 17.5 to 17, it doesn't go lower than that. What could be wrong? Thanks again
ReplyDeleteHi, I built it but bass is not working properly. It is too weak and bass pot doesn't help much either.
ReplyDeletehi ! It's verified with the update ;)
ReplyDeleteVery nice sounding, but first stage gain is a bit noisy, , anyone have an idea to solve it ?
Just finished this. Sounds great. Had an issue with the MAX1044, just squealed constantly then started smoking and fried itself. Biased to 9v. Replaced with LT1054 and works straight away
ReplyDeleteHi, I just built and sounds great! My remarks below:
ReplyDelete- this pedal is very sensitive for quality of power supply and charge pump 7600S was squealing and when I put there MAX1044 original one was fine besides low frequency noise which I removed by connecting better quality separate power supply. Maybe it would be good idea to make new layout where charge pump section is moved a bit from j201 and rest of components as it is in JHS Twin Twelve pedal.
- I replaced EQ pots linear 1m to logarithmic 1m as it is in original Silvertone amp. You can simulate this EQ section in online app http://www.guitarscience.net/tsc/james.htm and see difference between this two pot characteristics.
- Bass control seams to be weak but it's very similar to demo made by Pete Thorn about JHS Twin Twelve. To increase range you can lower value of 68k resistor connected to 1 pin of bass potentiometer, but all EQ components are identical as it is in original Silvertone amp.
- I had to put bigger value than 100k trimmer nearest charge pump to be able to go lower than 10V.
Hi, I builded this pedal without charge pump using 18V power supply and it does'nt work at all. I excluded 2 10uf caps and 2 5817 diodes which I replaced with jumpers. I checked every solder joint, connections, bridges, components orientation, etc... I also checked my JFETs and they are okay. Im only getting volt reading from bottom right trimmer. It only makes like 18v hiss noise or whatever. Please help! Im out of ideas.
ReplyDeleteYou need to have this capacitors and diodes in power supply section.
DeleteHi! Me once again. I built it one more time and Bass and Treble works better with 1m linear. Sorry for misleading. To have Bass range like in JHS you need to replace resistors connected to Bass pot 68k with 27k and 10k with 1k (original pedal has this values there).
ReplyDeleteHi! Thank you for the improvements! regarding the Bass pot it should changed both 100k to 1K (from lug 2 and 3) or from which lug should change to 1k ? thanks a lot in advance!
Delete