The Passinwind Open Source Preamp

[dcoyle]

"I recently acquired a Peavey Grind 5 string, passive electronics, and the PO had replaced the original pots w CTS pots and rewired the controls from the original vol/vol/tone/tone to vol/tone/PUblend, leaving the fourth pot an unused dummy."

I have one of those from the era with the slap cutout, and while it's a very nice feeling bass, those pickups are pretty dark, IMO. You might consider buffers after the pickups, before the passive volume and tone, to keep what little treble it has from being eaten by the passive controls. Might only be a marginal improvement as there is only so much treble coming out of a 16K series humbucker.

 

[dcoyle]

Just ordered a set of caps, fixed resistors, and IC's from the three BOM's for Mouser that Charlie has posted at GitHub, Passinwind. (I increased the number of .01 bypass caps from 9 to 10 to get a price break.) Total was $55, shipping another $8. All parts were in stock.

 

[Passinwind]

Just ordered a set of caps, fixed resistors, and IC's from the three BOM's for Mouser that Charlie has posted at GitHub, Passinwind. (I increased the number of .01 bypass caps from 9 to 10 to get a price break.) Total was $55, shipping another $8. All parts were in stock.

Cool. Thanks for all the proofreading on the schematics and BOMs, as it's just a bit too much for me to deal with on my own right now.

Not sure what's going to become of v2, none of the versions I've built have been quite up to snuff and I have zero play money left for this year to mess with revisions, much less any time!

 

[Snert]

and I have zero play money left for this year to mess with revisions, much less any time!

Good to see I'm not the only one...

 

[LowWay]

I’ve read through some recent posts in the thread and am not sure I’m up to speed. Is this currently diy only? Is anyone out there willing to assemble one for me (for pay)? Are there any printed enclosures left?

 

[dcoyle]

It is DIY. The resistors and IC's are SMD size. The caps are small through-holes.

The enclosure is made to your order. Buy a painted 1590BB2 size box and have the vendor drop ship it to AmplyFun. The have a file to drill the holes. They have a file to print Passinwind label art. You can choose the color. AmplifyFun then ships it to you.

 

[Passinwind]

It is DIY. The resistors and IC's are SMD size. The caps are small through-holes.

The enclosure is made to your order. Buy a painted 1590BB2 size box and have the vendor drop ship it to AmplifyFun. They have a file to drill the holes. They have a file to print Passinwind label art. You can choose the color. AmplifyFun then ships it to you.

The ones you and I got are actually the taller 1590BBS, I haven’t tried cramming everything into a 1590BB2 yet. Both of those sizes have the same footprint on a pedalboard, and Stompbox Parts offers a number of nice powder coat finishes for 1590BBS.

 

[dcoyle]

Thanks for pointing that out, I'm about to order another.

 

[claudel]

Anybody gonna be assembling these for the electronically challenged?

 

[MoireBass]

Not sure what's going to become of v2, none of the versions I've built have been quite up to snuff

The V2 is still the latest version without surface mount components, right?

 

[Passinwind]

Anybody gonna be assembling these for the electronically challenged?

Yep, probably a few people actually. For right now I'd recommend PM'ing @AudioTaper, who I know can do a great job. I won't be gatekeeping or making any money on whatever happens on that end, but I haven't ruled out setting up some sort of modest production entity myself sooner than later.

The V2 is still the latest version without surface mount components, right?

Correct, but the constraints of using a pre-determined Tayda 125B drilling template have been kind of bugging me, plus the through hole opamps I'd prefer have gone sky high on pricing now. And my ancient computer has become a real bottleneck in way too many ways, so I ordered a new one last night. I'm prioritizing putting my best foot forward at NAMM, hopefully if that works out then the rest takes care of itself organically.

 

[Tassieviking]

Not sure what's going to become of v2

If I was going to build one now I would go for the V4 one, it just offers a lot more than V2.
I have only soldered a handful of 1206 SMD LED's but it was a lot easier then I thought, everyone should give it a go.

 

[Passinwind]

If I was going to build one now I would go for the V4 one, it just offers a lot more than V2.
I have only soldered a handful of 1206 SMD LED's but it was a lot easier then I thought, everyone should give it a go.

I find my part SMD builds to go a lot faster and be a lot easier in general, by now. If we want to use the best, most cost effective opamps it's becoming nearly mandatory to use SMDs at this point, IMO. But still, I'd like to give people the option to do something cheap and cheerful, just have to find the right sweet spot to make it worthwhile.

 

[MoireBass]

plus the through hole opamps I'd prefer have gone sky high on pricing now.

What are you looking for with your preferred op amps? Other than GBWP, noise, current consumption, and output drive, what else is important? Do you see stability issues with some op amps with your resonant filter?
Other than a very large reduction in supply current, what makes an OPA207 work better in the circuit than something like an ancient cheap μPC4572?

Good luck and good fortune at NAMM.

 

[Passinwind]

What are you looking for with your preferred op amps? Other than GBWP, noise, current consumption, and output drive, what else is important? Do you see stability issues with some op amps with your resonant filter?
Other than a very large reduction in supply current, what makes an OPA207 work better in the circuit than something like an ancient μPC4572?

Good luck and good fortune at NAMM.

Thanks. I have seen stability issues occasionally, v2 actually seems to be suffering a bit from that in the LPF section at the moment with both OPA2134 and TL072, and the v4 Bax section really doesn't like OPA1656 for whatever reason. Current draw isn't too much of an issue with a 7 opamp pedal oriented circuit, but graceful clipping behavior with no latchup is definitely important. Noise figure is not as always as big a deal as many seem to think, IMO and IME, especially if we're already hanging something inherently noisy like a 1Meg input resistor and high impedance signle coil pickups in front. Anyhow, it mostly seems to come down to the ever elusive "play feel", which I try to stay agnostic about and let others tell me what works best for their wants and needs. Just did a six pedal test with my primary luthier client last weekend, it was uncanny how well he could parse subtle circuit tuning and component differences. At the end he liked everything he tried, but the least bass centric build was his favorite. Go figure!

 

[AudioTaper]

Update:

Mouser BOMs are up for the v4 boards on GitHub now, so on to the pots, switches, jacks, enclosure, etc. next. A lot of that stuff is going to come down to individual builder preference, but I want to make sure we at least have the basics covered decently.

Also, it looks like another NAMM trip is pretty likely. Not sure exactly what form my involvement may take this time around, but I'm hoping to have at least a few v2 and V4 pedals in booths where they will actually be easily accessible and not an afterthought. A lot of the usual suspects have been biding their time on booking, but January isn't all that far away! I'm sure there will be a few legacy onboard installs at the Marco Bass booth, and maybe one or two new ones if things go right. But I've mostly moved on to pedals for now, and also to other applications than just bass guitar, so...

Could you (or someone) post a link to the GitHub page?

 

[dcoyle]

GitHub - Passinwind/PW3B-LPF: Open Source Filter Preamps for Bass, Guitar, Mandolin, and other musical instruments

 

[dcoyle]

I continue to slowly collect parts for my v4 build.

I bought two painted 1590BBS enclosures at Stomp Box Parts, and had them drop ship to AmplifyFun. The price was $34.47, or $17.24 each, shipped.

Spencer, at AmplifyFun, just invoiced me for drilling the 11 holes and painting the Passinwind labels, per Charlie's supplied art, "PW3BLPF_Rev5_88". It was $9 for drilling and $5 for the UV graphics per box. So $21 each, with shipping, for drilled and pretty.

Charlie, I was wondering if your single channel buffer board was near where you might make them available at Osh Park? I was thinking of using one on a switch to allow the input to jump the HPF into the Bax or into the LPF. I don't know that I need this, but I want to explore it. If your board is not available, I'll build a perf board 8DIP unity voltage follower, copying your power supply treatment on the HPF.

To set the input Z for active or passive PU's, I expect to put a 1 meg SMD resistor at R2 of the HPF board, and a shunting R of 287K on a switch by the input jack to get the stock 220K input. Is this likely to cause any problem other than thermal noise?

Thanks

 

[Tassieviking]

I would love to get my hands on the graphic files to get the V4 boxes drilled and painted, it might be a bit expensive to send them to the US and then to Australia to get them done.

 

[bowthing]

Thanks for this tip! I hadn't noticed they had started making the OPAx205 in SOIC. Looks like they are about $12-$14 CAD for the 2205 so... yeah, more than "a bit" more expensive.

I see there is an OPA2206 in SOIC8 for around $3. Looks to be pretty much identical...