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The Passinwind Open Source Preamp

#262
40Hz said:
Thanks for that link. Some interesting things I'm reading there about microphonics that would make it a non-starter for my own tinkering too. I can mess with electronics without screwing things up (most times) too badly due to my haphazard electronics education and the sorry state of my "knowledge." (I'll really need to buckle down and do some structured courses some day.) But I'm not the world's best when it comes to mechanical engineering. So if I can't just mount and forget, it's not something I'm going to want to get into too much. Especially at $50 a pop when that'll get me a half dozen fineass ICs I actually do know a little about using already. :laugh:

PS - DigiKey just shipped the 1352s. Boards are still en-route. Maybe if I'm lucky I can find a few hours next week to put something together assuming that new Hakko 888D I ordered arrives too.
Click to expand...

I've had an 888 for a few years now and am very happy with it. It's well worth buying an assortment of tips for it IMO.

For the last tube preamp build I did I had to go all in on killing microphonics, especially for the 6SL7 front end. I started with this "cage", then added a big heavy 1/8" aluminum damping plate underneath, with grommets in between, and trick Teflon composite tube sockets. It's been going strong for the friend I built it for for a few years now, a good thing considering all the dweebing it took to put it together.

PW6B_TubeMounts.jpg
 
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#264
I'm in the same boat. I finally have all the parts. :hyper:

But now I'm waiting for my new soldering station to arrive. Arrggh!!! :banghead:

I think the fates are trying to tell me something. :rolleyes::eek::cautious:

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@Passinwind - those boards are really nice! Gonna have to remember the supplier. I even like the purple color. :thumbsup:
 
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#265
40Hz said:
@Passinwind - those boards are really nice! Gonna have to remember the supplier. I even like the purple color. :thumbsup:
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OSH Park provides a pretty killer service and if you look through various commercial EFX threads you'll notice quite a few of those purple boards. My last order was fulfilled in only eight days too.

BTW, I'm getting close to backing off the default gain recommendation. The next few early adopters might want to just tack solder in the peaking/gain setting resistors until they see for themselves where things are at. There's such a wide variation in pickup outputs and player dynamics that this is never going to be a simple one size fits all thing anyway though, really.
 
#267
Passinwind said:
BTW, I'm getting close to backing off the default gain recommendation. The next few early adopters might want to just tack solder in the peaking/gain setting resistors until they see for themselves where things are at. There's such a wide variation in pickup outputs and player dynamics that this is never going to be a simple one size fits all thing anyway though, really.
Click to expand...

Very good Idea. I wound up changing them in the mid and bass sections and in the LPF. Also, the wiring for the dual ganged pots can be a little tricky, but Charlie's working on the diagrams for those.
I don't want to jump the gun on the tweaks, so I'll let Charlie present the info in the manner he prefers. Once we all get to messing with them I'm sure we'll be sharing the info here or in the wiki pages on our particular tweaks and mods.
I'm pretty pleased with the results so far. I haven't decided if I'll be installing it onboard my favorite bass or keep it as a boxed unit with footswitch bypass so I can use it with my others basses too. Maybe both. I bought enough parts for 3 of 'em.
 
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#270
BadExample said:
A couple of pins snipped out of a good machined DIP socket is real handy for experimenting with resistor swaps. Most of the sub-watt leads fit well enough to leave the pins in forever.
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+1
That's what I did with the first one. Make sure you use good quality sockets though. I grabbed an unknown from my parts bin and the pins didn't hold the leads well after a couple changes.
 
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#276
A few thoughts:

You can use breakaway header pins like this: Invalid Link Removed

You could start with a higher value and parallel another resistor for fine tuning. Just adding a "U" bend between the resistor body and where the lead inserts into the board gives you an easy enough place to tack solder in the trimming resistor.

If using pots be sure to hand match resistance settings within 1 percent or better in order to preserve the designed alignment. I originally played around with asymmetrical values quite a bit though, and that's something that opens up many other potentially cool filter alignments. Yet another rabbit hole to map on the to-do list, I guess...
Or_wink.gif
 
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#277
Well, I thought I pulled all the trim pots while searching for caps and switches. I didn't. So they are in a area of the garage that requires a hazmat suit to enter.

I did find a lone 10K 20 turn in a bag of other stuff. That would be 500 ohms per turn or about 1/10th of a turn for 1% accuracy around 5K. That might work, but only one right now. Also found a few vertical 10K's but IIRC those would be 10 turn and might get a bit finicky to adjust within 1%. I have to finish the honey-do list and work on my Jeep's taillights before the boss wakes up... then who knows where the rest of the day will lead.
 
#278
BadExample said:
Well, I thought I pulled all the trim pots while searching for caps and switches. I didn't. So they are in a area of the garage that requires a hazmat suit to enter.

I did find a lone 10K 20 turn in a bag of other stuff. That would be 500 ohms per turn or about 1/10th of a turn for 1% accuracy around 5K. That might work, but only one right now. Also found a few vertical 10K's but IIRC those would be 10 turn and might get a bit finicky to adjust within 1%. I have to finish the honey-do list and work on my Jeep's taillights before the boss wakes up... then who knows where the rest of the day will lead.
Click to expand...

If you're just using the trim pots to spitball a final resistor value then ultra fine scale matching probably won't matter all that much anyway, I guess. I probably have some workable 10 turn trimmers kicking around here, but it'll probably be a little while before I get back to building up any more of these boards and have a chance to play with 'em.
 
#280
Probably your best bet. If you want something for R&D, and I have it, and it's tiny, it's yours (or anyone's). I have capacitors ahoy and a zillion C&K switches. The switches are meant for black knobs, "Bat handles" we called them. I don't have those, so they look a bit funny on the end. Many are PCB mount, long 90 degree pins, but with the gold plating I've had good luck snipping the bends off and soldering a wire like a butt splice. I have a bunch of funny ones, 3 position and maybe 6 or 8 poles. Handy sometimes. C&K's last forever and a day.

Edit: What the hell's a blast knob? Black knobs... dain bramage.
 
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