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The Passinwind Open Source Preamp
- Thread starter Passinwind
- Start date
- Dec 3, 2003
- 23,049
- 45,913
- Disclosures
- Designer/Toaster Tech @ Passinwind Electronics
Everything onboard. First two knobs are neck pickup volume and bridge pickup volume. Pick shaped knobs are bass pup resonance, bass pup freq, neck pup freq, neck pup resonance.
Didn't notice the pick shaped knobs.
Anything particularly non-intuitive in the two filter set up?
Anything particularly non-intuitive in the two filter set up?
- Dec 3, 2003
- 23,049
- 45,913
- Disclosures
- Designer/Toaster Tech @ Passinwind Electronics
The thing that probably stands out most so far is how cool the bridge pickup sounds just on its own. I’m also finding some great upright vibes, which are always welcome.
I only got to play through the v2 pedal briefly yesterday, but it sounded really good as well.
I want to force dual filters into this thing so badly (one for the MM, one for the J set). So, if you decide you want a guinea pig for further experimentation just let me know! I'll gladly route the back out of it in a heartbeat to make it so.
Thanks! I'll try not to derail further, but that was me botching the bridge position and intonation after swapping necks. It's normal now.
@Passinwind suggested this might be of interest to readers of this thread, where I ultimately tame overly bright pickups and add passive HPF and LPF onboard filters around a stock shelving pre-amp to make it more functional: Jackson Spectra: details, electronics, and some fixes/upgrades
It is of interest, both to see how far you've pushed passive networks and your description of how you went at it.
It's also a primer, of sorts, for how to use LPF and HPF, something I hope to explore in the not too distant future. Thanks.
It's also a primer, of sorts, for how to use LPF and HPF, something I hope to explore in the not too distant future. Thanks.
- Dec 3, 2003
- 23,049
- 45,913
- Disclosures
- Designer/Toaster Tech @ Passinwind Electronics
Random update: my third try on the v2 boards should be up and running by week's end, and I will then hand off the build spec to @Tassieviking and let him work out the Tayda-friendly final version. @dcoyle will be beta testing a v4 build similar in format to what a partially assembled board set from JLCPCB would look like. I'll be going into summer shutdown mode in my shop pretty soon, but it's been unseasonably cool here lately and I've been grinding away on some clone guitar pedals from PedalPCB to get a little more familiar with how that whole culture operates. Hope to have the first of those builds done in a day or two as well, but the graphics I'm planning are not quite TB safe. 
Charlie am I reading it right that you're looking at offering a pedal kit? I'd definitely do at least one if so.
- Dec 3, 2003
- 23,049
- 45,913
- Disclosures
- Designer/Toaster Tech @ Passinwind Electronics
Probably still more like a turnkey online "kit" with no more than two or three vendors and hopefully one click ordering at each one, but never say never! @dcoyle mentioned that the SMD components I'm using look a lot less daunting to work on now that he's seen the partially assembled boards up close. But still, if JLCPCB wants to do that work for about a dollar a board, it's something I have to look into.
" @dcoyle mentioned that the SMD components I'm using look a lot less daunting to work on now that he's seen the partially assembled boards up close. "
Yeah, the solder pads of the (3mm x 6mm?) resistors are as large as the pad on a smaller through-hole. I had seen really tiny SMD in production boards when I went to mod them, and concluded I couldn't.
" ... a partially assembled board set from JLCPCB would look like." "But still, if JLCPCB wants to do that work for about a dollar a board, it's something I have to look into."
Is JLCPCB a service that fabs the boards and then automates the soldering of the SMD resistors?
That would be useful.
Are you considering using art on those boards that would allow either a SMD IC or a 8 DIP IC (or socket) in the same real estate? I ask because that would allow home construction without having to solder IC SMD traces, which are considerably closer together than the SMD resistors. Nice SMD-only IC's like the OP 1642's, etc, are available pre-soldered to 8DIP pins on fleabay. Art for both, if it didn't compromise anything else, would also allow markedly easier troubleshooting, to be able to sub an IC in a socket rather than resoldering.
Yeah, the solder pads of the (3mm x 6mm?) resistors are as large as the pad on a smaller through-hole. I had seen really tiny SMD in production boards when I went to mod them, and concluded I couldn't.
" ... a partially assembled board set from JLCPCB would look like." "But still, if JLCPCB wants to do that work for about a dollar a board, it's something I have to look into."
Is JLCPCB a service that fabs the boards and then automates the soldering of the SMD resistors?
That would be useful.
Are you considering using art on those boards that would allow either a SMD IC or a 8 DIP IC (or socket) in the same real estate? I ask because that would allow home construction without having to solder IC SMD traces, which are considerably closer together than the SMD resistors. Nice SMD-only IC's like the OP 1642's, etc, are available pre-soldered to 8DIP pins on fleabay. Art for both, if it didn't compromise anything else, would also allow markedly easier troubleshooting, to be able to sub an IC in a socket rather than resoldering.
- Dec 3, 2003
- 23,049
- 45,913
- Disclosures
- Designer/Toaster Tech @ Passinwind Electronics
Thanks for you thoughts Dan. Unfortunately it looks like would substantially compromise the way I do board layouts. Here's how Pete Millet has implemented that idea:
Now I will have lost all the top side real estate under the opamp, essentially, and that space is often where I put the most critical power supply and/or signal traces. So I think there will just be the v2 pedal for SMD-wary builders and the modular v3 and v4 builds for the rest. No problem putting SMD opamps on an adapter and using a socket, so as you say troubleshooting and repairs wil be easier for v2 . SMD opamp failures have been very infrequent for me, but when they do occur my success rate subbing in new ones is probably well over 50%.
JLCPCB in Shenzen is the current source for the v2 boards, and once you buy varying minimium quantities of components from them it's dirt cheap to have them assemble small runs (20-30 boards) with their robotic process. The primary cost is for a human to load the component reels, about three bucks per component value and then it's a penny per solder joint, or something along those lines. Their Uniroyal 1% SMD resistors cost something like a penny too, whereas the Susumu 0.1% ones I'm using are 42 cents apiece in qty. 10 from Mouser. So assembly would need to be coordinated as group buy (no single board assembly per builder) and someone over here would need to warehouse and ship. Or someone could use the Pedal PCB model and make a business of it, which any of you all are more than welcome to go for.
- Dec 3, 2003
- 23,049
- 45,913
- Disclosures
- Designer/Toaster Tech @ Passinwind Electronics
Third try’s the charm, everything tests as expected now. This build spec is probably a bit too aggressive though, and OPA2132/2134 didn’t like it at all. I’ll play with some other Tayda-available chips as soon as I can find that stash, but I don’t think it going to be a problem. I love how easy these builds are compared to the modular ones, and I think we can still improve on that a little.
"Now I will have lost all the top side real estate under the opamp, essentially, and that space is often where I put the most critical power supply and/or signal traces. "
Glad you know what to do.
Glad you know what to do.
- Dec 3, 2003
- 23,049
- 45,913
- Disclosures
- Designer/Toaster Tech @ Passinwind Electronics
"Now I will have lost all the top side real estate under the opamp, essentially, and that space is often where I put the most critical power supply and/or signal traces. "
Glad you know what to do.
There just aren't all that many routing options when you're doing modules as small and component dense as I am, and I've been trying to avoid going to 4 layer PCBs. But I'll file away your idea for that one rainy day that may come along sooner or later.
There just aren't all that many routing options when you're doing modules as small and component dense as I am, and I've been trying to avoid going to 4 layer PCBs. But I'll file away your idea for that one rainy day that may come along sooner or later.
I will add that I have had generally good experience using FreeRouting, and it's free!
Hand routing is prettier for sure, but an autorouter can test so many more routing options than would be possible by hand that it may be worth a try when your layout starts to get very busy/tight.
Happy to help out if you have questions.
- Dec 3, 2003
- 23,049
- 45,913
- Disclosures
- Designer/Toaster Tech @ Passinwind Electronics
Does it handle component placement and understand audio nuances such as keeping inputs and outputs physically separated as much as possible?
Those are the most challenging aspects for me, and where I see many pedal layouts failing pretty badly.
Does it handle component placement and understand audio nuances such as keeping inputs and outputs physically separated as much as possible?
No, it doesn't do placement and doesn't have any specific knowledge about audio nuances. However, that's not as bad as it sounds and there are some workarounds:
- You can hand route important stuff (ex: grounds) yourself, then let it autoroute the rest
- It does try to optimize trace length and vias, which means component placement plays a large part in determining the routing. Putting related audio components next to each other will usually result in sane routing.
Like I said, it may not always be pretty but may be worth experimenting with.
