• TalkBass has been independent since 1998. Add your voice.
    Create a free account to reply to discussions, view embedded media, and browse with fewer display ads.
    Join free Log in
    Want zero display ads or expanded classifieds tools? Compare plans.

The Passinwind Open Source Preamp

#441
-Asdfgh- said:
I'm tempted to try this. An external option on a strap mount might be interesting. Is there a definitive version of the schematics, or when can I just buy one :)
Click to expand...

The schematic is linked in the first post. If a consensus ever emerges to change it I'll make it so. Someone actually has approached me recently about doing a stompbox version that he could market, and I intend to take a good look at that in the next month or two.

And to follow up on post #436: the alternate opamp testing has been going pretty well in my two band design and I'll build up one of the open source boards that way ASAP. There were clear differences apparent both on my oscilloscope and in (sighted) listening tests, but no clear winner has emerged yet. But cheaper up front and more frugal on battery life is likely to be fairly compelling, I think.
 
  • Like
Reactions: rufus.K and BadExample
#443
Passinwind said:
The schematic is linked in the first post. If a consensus ever emerges to change it I'll make it so. Someone actually has approached me recently about doing a stompbox version that he could market, and I intend to take a good look at that in the next month or two.

And to follow up on post #436: the alternate opamp testing has been going pretty well in my two band design and I'll build up one of the open source boards that way ASAP. There were clear differences apparent both on my oscilloscope and in (sighted) listening tests, but no clear winner has emerged yet. But cheaper up front and more frugal on battery life is likely to be fairly compelling, I think.
Click to expand...

Thanks, Passinwnd. I'll have to see if my tech (my wife, as her soldering is so much better than mine) can read the schematic. I'd look to do a guitar strap version. I wonder if an RPi type case would work for that.
 
#444
12bass said:
As far as op amps go, I lean toward better sounding parts, even if that means higher current consumption and a small price premium.
Click to expand...
In this case, with the two band preamp, sound quality is probably best described as a crossgrade, so those other factors are maybe not hugely important, but still nice to have. If I'm going to do a stomp version of the LPF preamp then I will definitely try a slew of other opamps, since most people will presumably use outboard power anyway.
 
#445
-Asdfgh- said:
Thanks, Passinwnd. I'll have to see if my tech (my wife, as her soldering is so much better than mine) can read the schematic. I'd look to do a guitar strap version. I wonder if an RPi type case would work for that.
Click to expand...

Your wife will probably prefer just using the standard circuit board, I'm guessing. For someone with experience stuffing and soldering will probably take a couple of hours max if done in one shot, but of course many of us don't always work that way.

It might be helpful to others if you post links to prospective strap mounted cases. I have some ideas too and will post them once I sort through my collection of saved links.
 
#446
Passinwind said:
Your wife will probably prefer just using the standard circuit board, I'm guessing. For someone with experience stuffing and soldering will probably take a couple of hours max if done in one shot, but of course many of us don't always work that way.

It might be helpful to others if you post links to prospective strap mounted cases. I have some ideas too and will post them once I sort through my collection of saved links.
Click to expand...

I was hoping something the size of : Invalid Link Removed but that has far too many holes in, so I might need to think a bit more
 
#447
I realise I have some 3mm birch left over from another project, so I could build a wooden box, with extensions to pass a couple of bolts through, through which the strap could pass. It would naturally slide down to the guitar end. I will have to diagram it, and in the spirit of these things, contribute back a plan if I get that far!
 
#448
Passinwind said:
Your wife will probably prefer just using the standard circuit board, I'm guessing. For someone with experience stuffing and soldering will probably take a couple of hours max if done in one shot, but of course many of us don't always work that way.

It might be helpful to others if you post links to prospective strap mounted cases. I have some ideas too and will post them once I sort through my collection of saved links.
Click to expand...

Here's my wooden concept (I'm doing a wooden external preamp in a box for my EUB project, so I thought I'd do a wooden one for ease of working, and just because... wood).

preamp box.jpg

P.S. It's external for the EUB build as I was concerned about having too many wires inside when an extending end pin has to pass in and out of the main body of the instrument. So taking the piezo straight out seemed simplest, and obviates the need for a battery box, as long as the connection to the external preamp is kept short. I will test this before I finalise the build, though.
 
#449
-Asdfgh- said:
Here's my wooden concept (I'm doing a wooden external preamp in a box for my EUB project, so I thought I'd do a wooden one for ease of working, and just because... wood).

View attachment 3039568

P.S. It's external for the EUB build as I was concerned about having too many wires inside when an extending end pin has to pass in and out of the main body of the instrument. So taking the piezo straight out seemed simplest, and obviates the need for a battery box, as long as the connection to the external preamp is kept short. I will test this before I finalise the build, though.
Click to expand...

If you're doing this for a piezo pickup we should really tweak the design, the input impedance is going to be too low otherwise. PM me and I'll run over some options for you. I can also try one of my stomp box versions with my BSX EUB to see if I can get a little smarter about this.
 
#450
Passinwind said:
If you're doing this for a piezo pickup we should really tweak the design, the input impedance is going to be too low otherwise. PM me and I'll run over some options for you. I can also try one of my stomp box versions with my BSX EUB to see if I can get a little smarter about this.
Click to expand...

No, no, for the piezo I have a preamp specifically for a piezo pickup to go in a box.
 
#452
Passinwind said:
Cool. So are you doing a mag pickup on the EUB too, or is this for a different project?
Click to expand...

Your preamp would be for general use. A strap mount means I can transfer it to another bass pretty easily, by changing the strap over, although I like spares, so I might end up building two in that case.

I am intending to put a magnetic pickup on the EUB as well, though. I need to conclude my experiments on extremely staggered alnico pole pieces to determine if I can use a pre-exsting bobbin and coil, or will need to build my own quad coil pickup with sufficient stagger. I suppose I could ultimately build a box for the piezo preamp, magnetic preamp, and a simple blend. That I am expecting to be a floor mount, though.
 
  • Like
Reactions: Passinwind
#454
Passinwind said:
It's been quiet here for quite a while now. Any new builds, questions, or comments?
Click to expand...

I thought you were a German guy in a helmet?

More seriously, I've been preoccupied with refinishing a Strat and a Les Paul kit and working out 72 pickup combinations and a preamp... to run a sustainer circuit. I should do a build diary (not for here, as it's all guitars).

Then... the EUB and the preamp.
 
  • Like
Reactions: EasyMudd, Gfkfloyd and Passinwind
#455
I'm still sitting on another preamp board, just waiting to be soldered. Would it be possible to chance a few component values to extend the freq and resonance range? These preamps are too flexable and interesting to not try to mod it!
 
  • Like
Reactions: Passinwind
#457
Gfkfloyd said:
I'm still sitting on another preamp board, just waiting to be soldered. Would it be possible to chance a few component values to extend the freq and resonance range? These preamps are too flexible and interesting to not try to mod it!
Click to expand...

Which way do you want to go with the frequency? We can readily change it either way, the downside typically being progressively less linear scaling at the higher frequencies if we use a higher value pot. Adding a frequency range switch is a definite possibility as well. I've been meaning to try both those approaches, many people have asked for that.

You have to be a little careful with increasing resonance, since this circuit makes a dandy oscillator when given half a chance. But I'll revisit the schematic in the next couple of days and see what I can suggest.
 
#458
I love the switched frequency option you've been considering; would you just switch between 2 different pots or switch in a resistor inline with the freq. pot? As far as frequency range, it would be interesting to see how the filter responds down to around 800 hz.
Very curious to see what can be done to prevent oscillation.

Once I've got a free weekend I'm going to get the parts on order and build one of these into an outboard test bench to try some of these modifications and report back to ya'll
 

Latest posts

Top Bottom
Back