SOLSTICE: Even easier PT2399 reverb!

[MrStab]

that's just it, though, Merlin - everyone's saying it's labelled wrong in the schematic, but upon removing that diode, it works as per the schematic!

for the record, replacing R14 with a pot is awesome - so much more flexibility. i used a 50k pot, but had to limit the minimum resistance to about 15k with a fixed resistor to stop runaway feedback.

[Jdansti]

Check the output voltage of your 78L05 during cut outs. Some of us have had problems and have gone to the bigger brother 7805. You won't need a heat sink if you do this mod.

[merlinb]

that's just it, though, Merlin - everyone's saying it's labelled wrong in the schematic, but upon removing that diode, it works as per the schematic!

I don't know what you're doing wrong, but apart from FSb and FSc being labelled back to front, everything is correct. Nothing wrong with the diode.

[MrStab]

there don't seem to be any cut-outs, John. although i have noticed you reported your problems after 10 mins of use, and i've only had one or two jams that long with it so i'll test more extensively. apart from a few annoying batches of lock-up chips, i've been lucky in so far as Little Angel & several Small Time Delay uses.

for all intents and purposes, this is the Equinox switching system with a JFET instead of a BC337. should it work? probably not. but it does! lol. tails and everything. if it ain't broke, right..?  i'm just expecting some catastrophic consequence to doing this.

btw, talking of catastrophe: if anyone tries the R14 feedback pot mod, it seemed to necessitate a 100R resistor in series with the trimpot (just a regular pot in my case) else it catches fire (this was before i got my clandestine switch working). although that may not be the case after the feedback pot is limited to 15k min resistance. as i mentioned i still need to test all this for extended periods to make sure it's safe.

[MrStab]

ah, not so great - when the amp's turned up loud, some of the verb bleeds through in the Off state. lame. i had it all boxed up and ready to give away, as well - totally didn't notice till i put it through the FX loop. might just true bypass it as i can't seem to work this switching out at all, dunno what i've done wrong. or i could try a NPN like the Equinox. unless anyone can think of a simple fix to kill the bleed? apart from that diode lol. maybe a diode across the Drain & Source of the  JFET, with the cathode facing towards the reverb section? unless, ofc, it's bleeding from the mixing side.

Edit: diode across the JFET didn't work. absolutely 0 voltage is getting through to it in the bypassed state anyway, not even on the lowest setting of my multimeter - so i think the switching is okay, it must be coming from somewhere else. i've heard of this before on delay-type circuits, maybe i should look up fixes. it's not the pot i added either, as it's the same when you set the resistance to what R14 would've been. hmm. unsure how i'd go about diagnosing this one.

[MrStab]

from the Equinox thread:

I read somewhere (on this forum, I forget where) that it's actually better to connect the digital ground to the main circuit ground through a small choke, which filters out the nasty digital crap from your normal ground.

maybe grounding the PT2399 pins 3 & 4 is behind this? it's a crashing waves kinda sound, affected in various ways by all the pots, present in both on & bypassed states. or intuition tells me it could be buffer-side.
sorry for excessive posting!

(LAST) update: because i'm a true deviant, i used the spare lugs of my DPDT to ground the Reverb pot when bypassed. problem solved... possibly. none of the horrendous popping you usually associate with passing DC and audio through a switch. a kludge indeed.

[Jdansti]

^ Good idea! (I think ) like you said, if it works it works!

[merlinb]

(LAST) update: because i'm a true deviant, i used the spare lugs of my DPDT to ground the Reverb pot when bypassed.

Doesn't that defeat the tails?

[MrStab]

i didn't think to look for that actually, i just tested it and you're right - no tails. i mentioned this possibility to the friend im making it for, though - they seem fine with it & didn't expect tails to begin with. it's an unfortunate compromise, but i guess it's a way to retain buffered bypass. this thing's really growing on me, i don't really wanna give it away! weirdly, i find it more enjoyable as an "overt" kinda reverb than the spring tank on my gigging head. you may have out-done Marshall! lol

it's for a friend who's into "glitch" type stuff but is dabbling more with guitar lately. it was hard convincing them that the runaway feedback from a non-limited feedback pot really wasn't a good thing. it makes sense to label that "Room size", i think. maybe the trimpot-turned-regular pot could be "Reflections". potifying R14 made the guy go from not wanting it to really wanting it, & personally i can't recommend it enough - totally blew the unit open. i didn't leave room for a battery, as i'm guessing this thing uses at least 60mA which would make it impractical anyway. but i will give them a DC plug wired to a battery clip, because i'm just nice like that.

awesome work once again, Merlin! thanks for all the help guys. fingers crossed i won't be back with another disaster. lol

[mremic01]

What are you guys using for the jfet? I don't think I've ever come across another pedal that calls for a J112, so I don't have any in my parts drawers. Would a J201 work?

[garcho]

from Merlin:

You need a FET with a low Vgs(off) rating, not greater than -3V really, unless you're willing to hand-select some that happen to be better than the data sheet maximum.

from the J201 datasheet:

min Vgs(off): -0.3V

max Vgs(off): -1.5V

[mremic01]

Well, the J201 didn't work, so  I decided to try bypass it. I ran the input into the 10k resistor after the jfet (R9), and I only seem to be getting the wet signal as output. The voltage regulator gets pretty hot, but puts out a consistent 5V. With the pot dimed, it's much quieter than unity gain. It seems to act more like a volume control than controlling the amount of reverb, and I get no output when it's turned all the way down. I'm at work right now, but I'll post voltages when I get home. Does anyone have any ideas what could be wrong?

[bluebunny]

If you've removed the FET and injected your input just before R9, then all your signal is going into the PT2399s.  You don't have a "dry route".  Which is why it's wet.  If you meant something else, then I'm talking b0ll0x...  (Long day!)   

[mremic01]

That would be it then. I actually clipped off the jfet leads and wrapped the input wire around what was left of the one that was soldered to R9, cause I was too lazy to unscrew the PCB to get under it. If put a J201 back in there, would it work or would there be a better spot to run the input into?

[bluebunny]

If you put the J201 back (and assuming it works), then wouldn't you put the input into the op-amp input buffer, as per the schematic?  This buffer drives both the wet and dry routes.

[Jdansti]

Another Solstice board etched and ready to drill and populate.

I spread the non-polar cap pads out a little because I found on my first build that my box caps have a larger lead spacing than Merlin's cute little blue caps.

[Jdansti]

Onboard Solstice/Amp Application

I just wanted to share some information about using the Solstice as a onboard reverb for a practice amp. My application is a Murder One amp, but this would work with any other 9-12VDC amp such as a Smokey, Ruby, Noisy Cricket, etc.

The Murder One uses a 12VDC power supply, so I tapped the power from the amp's power switch to supply 12VDC to the Solstice. The op amp on the Solstice can handle more than 12V, and it sounds great at 12V. I'm using a 7805 regulator instead of the smaller 78L05, and it easily drops the voltage from 12 to 5V for the PT2399s without getting hot.

Since I'm not using the specified bypass switch for the Solstice, I simply jumpered the SPDT switch connections on the board. If I don't want reverb, I just turn P1 completely CCW and I get a clean signal. There's no need for a bypass switch when embedding the Solstice, and the main switch for the amp kills power to it when I switch the amp off.

I like to have P2 as an offboard pot instead of a trim pot, so the other thing I did was minimize the number of wires going to the offboard pots as shown in the drawing below. There's no need to run multiple ground wires to the pots.

Anyway, I hope this helps those who want to add reverb to their practice amps.

[mremic01]

So I can't find any jfet that gets this thing to switch. The voltage regular seems to read fine. I get clean signal through when wired up as per the schematic. Is there a way to measure a fet's Vgs(off) so I can go through my stock and find one that's in spec?

[psychedelicfish]

Well, since I see you've tried a J201, which should have worked but didn't, I suggest you check the rest of the wiring around the gate of the FET (unless your J201 was fake and way out of spec). You might, for instance, have the diode round the wrong way.

In terms of measuring VGS_off check the Fetzer Valve article, there's a FET tester at the bottom which will give you the FET's VGS_off. Be aware that they call VGS_off "VP" in that article.

[Jdansti]

As a quick test, disconnect the switch and place a temporary jumper across FSa and FSc. This should switch the reverb on if all else is ok.