The Passinwind Open Source Preamp

[Passinwind]

The black knobs you see on my gold (post 1192) box are about 14.6D x 16.7H (Tayda A-6491) .
The white knobs in post 1163 are KN1611 style but have a set screw, 16.5D x 14.5H (Tayda A2818)
If I was good enough to play on a dark stage then I would have to go for something like a Davis 1510 clone 19.2D x 14.5H (Tayda A-6792), this size covers some of the text on my fascia and half the dots as well.
Davies 1400 style could be used but it also covers some of the text and dots on the fascia.
Marshall knobs are ok as well but covers the graphics slightly.

I think 16mm diameter is a good fit, but if the fascia graphics are made for bigger knobs then up to 20mm.
For the best look I like the black ones you have used before, that's why I bought the black ones that are similar.
Best for dark rooms I think the Davies 1510 type, or KN1611 style knobs if you can find them with T18 shaft.

Thanks, I will just print up a few different iterations and play with test fitting the various knobs I have on hand. I already have some solid shaft dual pots with angled PC pins here that should fit your board design, in which case KN1611 with set screws would probably be my go-to as far as visibilty. 1510 is great that way, and readily available for both solid and split shafts, but it seems likely to be an awfully tight fit for this job.

I think I've hit the wall on graphics design for a few days now, so off to domestic chores and some soldering fun.

 

[Bemo9]

Sorry to be so late to the party. I think the tick marks are essential on this design. Ultimately if the settings you use sound good to you then they are good. But having the reference is super helpful.

 

[Passinwind]

Sorry to be so late to the party. I think the tick marks are essential on this design. Ultimately if the settings you use sound good to you then they are good. But having the reference is super helpful.

Good timing, as I am about to submit a Tayda order this morning. I did up nine graphics versions yesterday and will submit two of those as testers. I may avoid yellow this time around just because Ive used it so much lately, but here's the general idea:

 

[dcoyle]

"I did up nine graphics versions yesterday"

"I think I've hit the wall on graphics design for a few days now"

IMO, you've got a nice looking result, in post 1203. The 16mm knobs look nice, neither fiddly small nor too big for the package. The logo and model name script is wider than, say, post 1195, and is now not so much narrower than the individual pot labels. That's my (very personal) notion of how things should be.

You mentioned that some version has a variable recovery gain. Not that you wanted it, and existing layout aside, is there a reason why that gain trim pot couldn't be accessible from the outside?

Oops, edited to say, have I goofed and the leveling gain is in the WTHPF?

 

[Passinwind]

"I did up nine graphics versions yesterday"

"I think I've hit the wall on graphics design for a few days now"

IMO, you've got a nice looking result, in post 1203. The 16mm knobs look nice, neither fiddly small nor too big for the package. The logo and model name script is wider than, say, post 1195, and is now not so much narrower than the individual pot labels. That's my (very personal) notion of how things should be.

You mentioned that this version, V4, has a variable recovery gain. Not that you wanted it, and existing layout aside, is there a reason why that gain trim pot couldn't be accessible from the outside?

To clarify, the one in post 1203 is a v2 mockup (through hole Tayda parts, no HPF, no adjustable gain leveler), and those are 15mm knobs. With very nearly the same graphics layout, but in a different color ink, using the 1611 knobs which are 16.4mm things look like so:

......................................................................................................................

I can broaden the flat postition ticks as needed as an option for these bigger knobs, but since I'll likely be using 15mm knobs this ^ is one of the Tayda prints I ordered today, using their Champagne Metallic finish:



................................................................................

And then I went for "Glimmer Brown Sugar" using another of three subtly different yellow treatments, back to 15mm this time:


..................................................................................................................................

....................................................................................

I am in fact working on a new v4 build at the moment too, and I think I've found a better solution to wrapping and securing the three SMD modules, which had been a big time suck up to now.

 

[dcoyle]

I kinda realized my mistake and edited my post while you were answering the original post.

I said "The 16mm knobs look nice, neither fiddly small nor too big for the package." Thanks for pointing out they are 15mm, not 16mm. The 15's look right.

 

[Passinwind]

I kinda realized my mistake and edited my post while you were answering the original post.

I said "The 16mm knobs look nice, neither fiddly small nor too big for the package." Thanks for pointing out they are 15mm, not 16mm. The 15's look right.

Luckily thare are quite a few 15mm knob options available. FWIW, if we did away with the battery capability there would probably be room to do a WTHPF v3 or v4 in a 125B case with through hole parts, but let's not get ahead of ourselves!

 

[Passinwind]

Update,

I ordered two v2 boxes as pictured in post #1205 and they are in final production right now. Meanwhile, five v2.8 (my revised take on @Tassieviking's v2 layout) PCBs shipped yesterday:

Unlike the Tassie all from one source (Tayda) mantra, I've gone through a few different US vendors to procure various value right angle pots that will be direct fits, and I've now worked up what should be a pretty cool starter tuning spec:

Nominal frequency sweep range is 240-7.2kHz, with up to about 15dB of resonant gain available. Easy build, with no oddball resistor or cap values needed. And overall polarity is now non-inverting.

 

[bowthing]

Update,

I ordered two v2 boxes as pictured in post #1205 and they are in final production right now. Meanwhile, five v2.8 (my revised take on @Tassieviking's v2 layout) PCBs shipped yesterday:

View attachment 5040298

Unlike the Tassie all from one source (Tayda) mantra, I've gone through a few different US vendors to procure various value right angle pots that will be direct fits, and I've now worked up what should be a pretty cool starter tuning spec:

View attachment 5040343


Nominal frequency sweep range is 240-7.2kHz, with up to about 15dB of resonant gain available. Easy build, with no oddball resistor or cap values needed. And overall polarity is now non-inverting.

State-variable?

 

[Passinwind]

State-variable?

Nope, still Sallen-Key. But I do have a state-variable build currently just set up for bandpass mode that I want to dive into using as a resonant LPF sooner than later.

 

[Tassieviking]

I got an Email from Tayda that the C20k dual pots are back in stock, but it's not showing up online yet.
If I could use dual pots that had right angle PCB legs I would use them instead, depending on the cost.
I was hoping Charlie would fine tune what I did, I'm sure the design will go through several changes eventually.
Cheers
Michael

 

[Passinwind]

I got an Email from Tayda that the C20k dual pots are back in stock, but it's not showing up online yet.
If I could use dual pots that had right angle PCB legs I would use them instead, depending on the cost.
I was hoping Charlie would fine tune what I did, I'm sure the design will go through several changes eventually.
Cheers
Michael

Right, this is still in proof of concept phase by my reckoning. Rearranging your layout a little was so much easier than starting from a white sheet, but there are atill quite a few little details that I left for later, let's make sure it all works as expected first.

My C10K angle mount pots shipped this morning and I already have plenty of C50K ones on hand. The good news is that both pot vendors are well known and useful for many other things, and in both cases the pots are not terribly expensive for those of us in the US. I should hopefully be able to convince at least one of the vendors to stock both eventually, but as I mentioned before I think I can also do adapters for the straight pin Tayda ones to accommodate you and others who for good reasons want to avoid shipping from the US. And of course your DIY solution looks to work just fine anyway!

Meanwhile the third v4 build is now up and running:

We did a direct comparison with the recent URB build on Friday night and this one has a much more "electric bass" vibe, as intended. All three builds in this series are pretty danged good sounding IMO, so deciding on a preferred default spec may be a bit challenging. I think it'll come down to control feel: which one is most intuitive and has the most useful range from 9 to 3 o'clock.

 

[Tassieviking]

That looks nice.
Maybe leave sockets in for the components that can be changed for different voicing or whatever.
In a Sunn Beta pedal I made for myself I used sockets on 4 capacitors, that was the only difference between a Beta Bass and a Beta Lead pre-amp.(And there is no reverb in a Bass version but it wasn't put in anyway)

 

[Jim C]

6 knobs and 2 switches is the perfect balance IMO.
It covers all of my requests and sounds beautiful.
Could V5 have an OD circuit?

 

[Passinwind]

6 knobs and 2 switches is the perfect balance IMO.
It covers all of my requests and sounds beautiful.
Could V5 have an OD circuit?

I actually have a few very simple single FET dirt appliances kicking around, but the FETs vary so much that you have to hand test and custom tweak each build. Feature creep...live it, love it!

Looks like my Tayda order may ship today, so the v2 test builds could be good to go in about a week or so.

 

[dcoyle]

That V4 rig sure looks good.

"We did a direct comparison with the recent URB build on Friday night and this one has a much more "electric bass" vibe, as intended. All three builds in this series are pretty danged good sounding IMO, so deciding on a preferred default spec may be a bit challenging."

Charlie, so nice to read they all sound PDG! I wonder if you could share what sound emphasis and circuit choices makes one more EB vibe and one SUB vibe? Is it how asymmetric the Bax range is on cut/boost? Where the mid is situated? Input Z? Stuff I don't know about yet?

Just my $.02, but I think it would be useful to keep a no-distortion version available, even if the circuit migrates onward.

 

[Bemo9]

Oh man that looks good Charlie. but the pedal is the wrong color scheme, lol. I'm serious that if you add that to a class D amplifier, you're all set. Dirt can always be added by a pedal.

 

[dcoyle]

"add that to a class D amplifier, you're all set"

Yeah, and you can lift it!

 

[Passinwind]

27429861[/URL], member: 359780"]Oh man that looks good Charlie. but the pedal is the wrong color scheme, lol. I'm serious that if you add that to a class D amplifier, you're all set. Dirt can always be added by a pedal.

The HPF and the Bax EQ in these preamps are actually derived from the circuits I previously used in a few DIY Class D amps, so it wouldn’t be much of a stretch!

 

[Bemo9]

I've currently got my amp set flat and use the pedal for all tone shaping, with the exception of a combo 5 band eq/compressor pedal. Honestly don't need much else.