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The Passinwind Open Source Preamp

#1,301
You're right, the higher pot value does get me in that direction.

I fit A500k pots for volume and 1M for tone, as well as a bypass switch to lose the passive volume pot and tone cap shunt to ground, when I want to. It also allows me to use a bigger cap to ground than I would if I couldn't disconnect it, .047uf in my case.

The buffer card I mentioned is a bypass-able perfboard and 8 DIP voltage follower, built into a J bass cavity, not the PW3B enclosure, put there to get rid of the same type of effects, the shunt capacitance of the 1/4" guitar cable.
 
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#1,302
@dcoyle I may have misspoke when describing turning the EQ off on my amp.
My testing with Charlie's boxes have been exclusively with this crazy little Traynor he turned me on to (SB500), an SVT-CL, a SWR SM400, and just a little bit with a GK MBF800.
None of these amps have an EQ off control but I nearly always test with the EQ set flat. But of course it's really not flat as all of my amps have some internal voicing.
Basses have been mostly passive Fenders with a Sting Ray too.

I was just thinking that I've never plugged the pre into the effects return and will try that tomorrow. I believe the pre has plenty of gain for this.
What type of gear have you used to listen?
 
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#1,303
I need to correct something I said in post 1297 re. bass extension of the HPF stage.

Me: "The in/out-of-circuit bypass switch helped me notice that the lower frequencies of the E string were lessened by the HPF, although, because of the boost just above the rolloff, it didn't sound bass shy. Just the thing for playing loudish."

Charlie pointed out that with the FREQ full CCW, on a four string, the bass should not be diminished and that's what I hear from my box.

So why did I notice a lack of deep bass?

I now realize that I hadn't taken into account where I had set the HPF FREQ control, which was above full CCW when I had compared the in/out of circuit. So of course it was bass shy, I was dialing it away paying attention to the type of resonance I wanted.

Sorry to misstate what was going on.

Me: "I came to wish there were an option to set the HPF to a lower frequency, so I could twiddle the fat/lean thing without losing the deeper extension of having no HPF in circuit."

I'm still interested in building a new HPF board with a lower F3, for the above reasons, but this is personal taste, not that the HPF doesn't pass 40 Hz as is.

Jim C, My comment that I prefer a flat EQ on the amp and to dial up what I want on the PW3B is based on my use of Fender type tone stacks in front of a 6x 6l6 tube amp or with a Crown bridged PA amp. I found flat on the tube pre by twiddling the controls till the it passed a square wave intact-ish.

While you mentioned how interactive you found the PW3B's controls, and I know what you mean as demonstrated by my snafu above, my subjective reaction is still to find the PW3B controls wonderfully specific. I've never liked how the Fender tone stack handles bass. I was rebuilding my Fender type tube bass pre as a Bax when I stumbled onto this thread. I find Bax's like the MXR M81 too muddy. I super value being able to adjust all the parameters available in the PW3B, without mud.

I happily note that Passinwind at github now has posted schematics for v4 and links to buy the boards at Oshpark.

Thanks, Charlie.
 
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#1,304
dcoyle said:
I happily note that Passinwind at github now has posted schematics for v4 and links to buy the boards at Oshpark.

Thanks, Charlie.
Click to expand...

The new DIY boards are all good to go but the schematics still may change a litttle, especially the mid frequency tuning choices. There are no 0805 SMD parts any longer, just the SOIC-8 opamps and 1206 resistors. I also have a lot of work left to do on build documentation, and all the Mouser BOMs of course. But this would be a great time to have a look and tell me what other info is going to be most helpful to future builders when ready tech support may no longer be available: Release Passinwind PW3B-LPF v4.0 · Passinwind/PW3B-LPF

I ran RTAs on three of my own WTHPF pedals ths weekend, just to double check HPF tunings. Nice to finally get some utility from my rack mount interface that I traded a nice cab for for several months ago! All were within 10% or better of my models' predictions, trending slightly higher than modeled. I'd expect your build to measure 3dB down at ~30Hz with the control full clockwise. Full CCW gives the most low bass cut if the pot is wired as intended. The HPF in the current Github schematic will give -3dB at approximately 25Hz (models at 22 and change), if that might work better for you. But all these numbers don't account for whatever native HPF the rest of you gear has built in, even just a simple coupling cap will skew things a little higher. This can be quite apparent when I try most commercial amps, for instance. But hey, it's DIY and with a little effort we can often modify overall response to our tastes and whims. ;)
 
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#1,305
Charley emailed me, re the HPF pot:

"That should be full clockwise, not counterclockwise. Same as the Broughtons, fdecks, etc. If you have that pot wired backwards the taper will be all wrong. Clearly I need to post pictures of the breakout board orientations!"

So I got that going for me!

Edit: Whoops, didn't stop to look to see Charlie's post above.
 
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#1,306
dcoyle said:
Charley emailed me, re the HPF pot:

"That should be full clockwise, not counterclockwise. Same as the Broughtons, fdecks, etc. If you have that pot wired backwards the taper will be all wrong. Clearly I need to post pictures of the breakout board orientations!"

So I got that going for me!
Click to expand...

Yeah, let's make sure things are working as designed, although my motto is "if it ain't broke fix it anyway."
 
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#1,311
T-34 said:
Hey looks like you know me very well :D
Click to expand...

If you were involved in enterprise level IT systems and services there’s a very good chance we share similar scars and horror stories. :laugh:


BTW, didn’t Avco Lycoming manufacture a gas turbine engine dubbed the T-34 - or is your handle maybe referring to the T-34 tank?
 
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#1,315
Passinwind said:
The new DIY boards are all good to go but the schematics still may change a litttle, especially the mid frequency tuning choices. There are no 0805 SMD parts any longer, just the SOIC-8 opamps and 1206 resistors. I also have a lot of work left to do on build documentation, and all the Mouser BOMs of course. But this would be a great time to have a look and tell me what other info is going to be most helpful to future builders when ready tech support may no longer be available: Release Passinwind PW3B-LPF v4.0 · Passinwind/PW3B-LPF
Click to expand...

I am a retired electronics tech with over 50 years modding basses and amps. I am VERY interested in building your preamp. Is it ready to go at this point? I would certainly appreciate a Mouser BOM for it, so it sounds like it's not quite ready for prime time?
 
#1,316
BQFS said:
I am a retired electronics tech with over 50 years modding basses and amps. I am VERY interested in building your preamp. Is it ready to go at this point? I would certainly appreciate a Mouser BOM for it, so it sounds like it's not quite ready for prime time?
Click to expand...

I'm still cleaning up the schematics, @Tassieviking kindly pointed out a few minor errors this morning. I just fixed those, but a few more sets of eyes on the schematics might be useful. Frankly, my head is no longer in this at all and I just want it to be finished. ;)

The Mouser BOMs are a substantial PITA, mainly due to having to watch what's in stock and/or likely to be there long term. And there are at least two or three other vendors in the mix, none of whom have project management software like Mouser offers. Hopefully I can knock the rest of this out in the next few days, but we're already at least six months beyond the expected release date, so who knows?
 
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#1,317
Passinwind said:
The Mouser BOMs are a substantial PITA, mainly due to having to watch what's in stock and/or likely to be there long term. And there are at least two or three other vendors in the mix, none of whom have project management software like Mouser offers.
Click to expand...

I have lots of free time, so if there is anything I can do to help you with the BOM, I would be happy to do so. As far as parts out of stock, etc. I wouldn't be too concerned. I build copies of the original Stingray preamp from a BOM that was created several years ago, and LOTS of parts are no longer available. Most of us DIY folks are quite capable of doing research for equivalent parts so long as the original part is in the BOM, we can find equivalents from either Mouser or places like Digikey or even Jameco.
 
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#1,318
BQFS said:
I have lots of free time, so if there is anything I can do to help you with the BOM, I would be happy to do so. As far as parts out of stock, etc. I wouldn't be too concerned. I build copies of the original Stingray preamp from a BOM that was created several years ago, and LOTS of parts are no longer available. Most of us DIY folks are quite capable of doing research for equivalent parts so long as the original part is in the BOM, we can find equivalents from either Mouser or places like Digikey or even Jameco.
Click to expand...

Thanks, I'll have to take a look at what I already archived on the Mouser project manager. It's not so bad for pedals, but during The Plague finding decent low current opamps for onboard builds was very dicey for a while.
 
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#1,319
TriumphRider99 asked:

"I would certainly appreciate a Mouser BOM for it, so it sounds like it's not quite ready for prime time?"

Nah, it's ready for prime time. :)

I just ordered a set of bare boards from Oshpark for the v4: three main boards, all breakout boards, which are particularly useful for the double pots and the gain pot, (and in my particular case, not the switch breakout board) and the total , shipped, was $36.15, for three complete sets of boards for three PW3B's, only about $12 per unit!
 
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