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Stingray aftermarket 2 band pre
- Thread starter blmeier7
- Start date
Just completed one of these boards last night, using a free sample of an OPA704PA. It sounds killer! The only issues I'm having is it doesn't seem to like my 18v Godlyke charge pump, and it distorts at 9v with my Ibanez GSR206 (with custom pickups). Other than that, it works great.
Thanks UncleFluffy for an awesome project and pcb!
Thanks UncleFluffy for an awesome project and pcb!
Glad to hear that we've got a working build, I was starting to get worried. They should be electrically the same as the last batch, but ...
I take it that the distortion is just a headroom issue? Does it go away when you play a little softer?
I take it that the distortion is just a headroom issue? Does it go away when you play a little softer?
Pretty much, and it only happens on the B. The pickups in the GSR are pretty high output as well. Once I figure how to do 18v, I'm sure the headroom will improve. I just haven't isolated whether it's the charge pump, or the circuit itself.
The absolute maximum supply voltage for the OPA704 is 13.2V so running it at 18V might have fried it Invalid Link Removed I would swap it out and see if it still distorts with a fresh opamp running at 9V
Oooppps! Missed that! It actually still works at 9v, so I don't think I fried it. I guess I'll have to find an opamp that works at 18v. Any other suggestions other than the LM4250?
there are a bunch like the TLE2071, LT1028, LT1115, LT1351, LF441A. Also the OPA1611 & OPA1641 with adapters since they are surface mount. I personally like the LT1351 and it only has a 200uA current draw. If you use the LT and OPA chips you might want to change both 2M2 resistors to 220K to allow more current to the chip. You will notice some of the chips are real bright and/or bassy and you'll have to roll back the bass and treble knobs a little
This might be a crazy question ... but what's wrong with the LM4250?
- Feb 16, 2008
- 21,240
- 23,638
- Disclosures
- John K Custom Basses
IME, original Musicman, Seymour Duncan's SMB-4a, and Nordstrand's MM pickups, all are fairly low output pickups if used passive, so if you're having distortion issues with other 'normal output' passive pickups, just install a higher value preamp input resistor (the 220K on the schematic). you can try a 330K or a 470K resistor to 'pad' the pickup's output, rather than trying to run the preamp at 18V or using a different chip. IMO, the LM4250 sounds great and exactly like the original EB 2 band.
Absolutely nothing, in fact it is perfect for that Stingray sound.
I ran a few tests a while back using different opamps. They are on an old computer somewhere but I remember that if you don't use a 4250 then the bandwidth and hence noise (hiss) increases dramatically. The 4250 limits the bandwidth due to it's minuscule power requirement.
Nothing really, I've just not been able to get one yet. I believe a local store has them in stock, so I'll hopefully be able to buy one soon. More curious on what different ones will work.
Passinwind
I know nothing.
- Dec 3, 2003
- 23,084
- 46,056
- Disclosures
- Designer/Toaster Tech @ Passinwind Electronics
Thanks to your posts I started with an LT 1351 sample, and am very happy with the results. I think I used 270K resistors for the input float, but I'll have to double check. Linear Technology sent me a bunch of other free samples (1028, 1128, 1115, and some 1124 duals for other projects), and quickly to boot. Frankly, I probably won't bother subbing in any of the higher current consumption types until I get around to another board build, LT1351 is plenty quiet enough and sounds perfect for my needs. I do want to try the LM4250 eventually as well...
Hello ppl!
After reading through all this topic, I decided to give it a try myself and maybe build a small "stompbox" if it's worth it - I always liked how a MM sounds (but still don't have one) so I've gone for the cheap way, building the preamp
Well, it's worth it! I used the Bajaman layout for the PCB, minus the strain-relief holes for the wires, to keep it a bit simpler, holewise
. It sounds great, and although it won't instantly turn your bass into a MM, it still significantly colors the sound towards that way. Here's the outcome, warts and all
I used a LM4250. The box is about 11 X 6 cm and the board is something like 5.5 cm X 2.5 cm. A 9v battery will fit in nicely, but there won't much room (if any) for a bypass switch this way.
Now, for the "not so cool" part
I noticed that, when turning the bass volume control down, the noise increases noticeably, as if there was some kind of treble boost. Also, when switching the bass from passive to active (I have a Lakland 44-01 with a pair of Big Splits and an OBP-3 preamp) there's an insane increase in the highs. Looking at the schematic again, IMO I think I know why; there's no separation (buffering) between the pickup and the treble control circuit, so the pickup itself plays a significant role in this filter. By turning the volume on the bass down or by switching to active, there will be a different (lower) impedance between the input capacitor and ground which, in turn, will modify the upper range of the treble circuit. Well, at least that's what I think
This is IMO normal behavior, since the pre was designed for the MM pickup, hooked to the input directly, with no other stuff in between. It's worth noticing if you plan to build the project not as a onboard pre, but as a box hooked after the bass volume control (and another possible onboard preamp).
Thanks to all that built the preamp and shared the experience!
Peace to ya'll !
After reading through all this topic, I decided to give it a try myself and maybe build a small "stompbox" if it's worth it - I always liked how a MM sounds (but still don't have one) so I've gone for the cheap way, building the preamp
Well, it's worth it! I used the Bajaman layout for the PCB, minus the strain-relief holes for the wires, to keep it a bit simpler, holewise
. It sounds great, and although it won't instantly turn your bass into a MM, it still significantly colors the sound towards that way. Here's the outcome, warts and all I used a LM4250. The box is about 11 X 6 cm and the board is something like 5.5 cm X 2.5 cm. A 9v battery will fit in nicely, but there won't much room (if any) for a bypass switch this way.
Now, for the "not so cool" part
I noticed that, when turning the bass volume control down, the noise increases noticeably, as if there was some kind of treble boost. Also, when switching the bass from passive to active (I have a Lakland 44-01 with a pair of Big Splits and an OBP-3 preamp) there's an insane increase in the highs. Looking at the schematic again, IMO I think I know why; there's no separation (buffering) between the pickup and the treble control circuit, so the pickup itself plays a significant role in this filter. By turning the volume on the bass down or by switching to active, there will be a different (lower) impedance between the input capacitor and ground which, in turn, will modify the upper range of the treble circuit. Well, at least that's what I think
This is IMO normal behavior, since the pre was designed for the MM pickup, hooked to the input directly, with no other stuff in between. It's worth noticing if you plan to build the project not as a onboard pre, but as a box hooked after the bass volume control (and another possible onboard preamp).
Thanks to all that built the preamp and shared the experience!
Peace to ya'll !
Thanks for the great pics of the stompbox, as my first board will go into this configuration. Congrats on an awesome job.
Now, for the "not so cool" part
I noticed that, when turning the bass volume control down, the noise increases noticeably, as if there was some kind of treble boost. Also, when switching the bass from passive to active (I have a Lakland 44-01 with a pair of Big Splits and an OBP-3 preamp) there's an insane increase in the highs. Looking at the schematic again, IMO I think I know why; there's no separation (buffering) between the pickup and the treble control circuit, so the pickup itself plays a significant role in this filter. By turning the volume on the bass down or by switching to active, there will be a different (lower) impedance between the input capacitor and ground which, in turn, will modify the upper range of the treble circuit. Well, at least that's what I think
hmm thats weird. my pre in the enclosure is quiet as a mouse no matter the knob settings and I run it at 18V. might be due to the LT and OPA opamps I use. I also used metal film input/output caps since I had more room in box. I dont know if that contributes to less noise. when you run the OBP-3 preamp through it the highs are going to be insane because the signal is being EQ'ed and boosted twice before it hits the amp.
Hi!
@BassLife77
In passive mode and the volume knob on the bass set to zero, there's a noticeable ( not huge, though ) increase in treble output (a moderate hiss can be heard). Otherwise, it's very quiet, like you said.
With the OBP-3 engaged, if set to flat or even with it's treble fully cut, there's even a more generous amount of highs in the output; I think that's because OBP-3 has a significantly lower impedance than the pickups themselves (100ohms vs. a few kohms) so it's almost like a short between the input cap and the ground. That's why I suspect it modifies the treble circuit response. It's not like it's unusable, just much too trebly for my taste
Mind you, when I plug the bass directly in the amp, there's no difference (at least not one that I can hear) between passive/active output.
@praisegig
Thanks man! Good luck with your project!
@BassLife77
In passive mode and the volume knob on the bass set to zero, there's a noticeable ( not huge, though ) increase in treble output (a moderate hiss can be heard). Otherwise, it's very quiet, like you said.
With the OBP-3 engaged, if set to flat or even with it's treble fully cut, there's even a more generous amount of highs in the output; I think that's because OBP-3 has a significantly lower impedance than the pickups themselves (100ohms vs. a few kohms) so it's almost like a short between the input cap and the ground. That's why I suspect it modifies the treble circuit response. It's not like it's unusable, just much too trebly for my taste
Mind you, when I plug the bass directly in the amp, there's no difference (at least not one that I can hear) between passive/active output.
@praisegig
Thanks man! Good luck with your project!
Reading through and interested, as I was just looking for a pre to drop in the Robin Freedom I just picked up (a little too noisy)...found this in a separate search but the parts list looks very similar. Has anyone looked at dropping these components onto UncleFluffy's board?
DIY Ref Music Man Stingray Bass Guitar Preamp Component - eBay (item 110661573933 end time Mar-21-11 16:29:51 PDT)
I'd like to give it a shot but of course being the king of unfinished projects I'm always saying that...
DIY Ref Music Man Stingray Bass Guitar Preamp Component - eBay (item 110661573933 end time Mar-21-11 16:29:51 PDT)
I'd like to give it a shot but of course being the king of unfinished projects I'm always saying that...
As an eBay Associate, TalkBass may earn a commission from qualifying purchases.
Being new to the DIY world, I need all the help I can get. I'm in the middle of my preamp build and would like some suggestions on the 120pf cap. I purchased the one from the parts lists on the forum and it is way too large in this installation. I don't like the way it looks on my board, and wondering if anyone has a smaller/compact replacement. In using the cap above, I also had to clean the mounting holes out to .032 with a pin vise drill, to allow for the large leads. I really don't want that to be a problem in a build.
I've seen other pics in the topic that look a lot better. Any help on part numbers and sources would be appreciated. Something more to these in post #320 on page 16 and post #265 on page 14.
My board
1752945[/ATTACH]"]
I've seen other pics in the topic that look a lot better. Any help on part numbers and sources would be appreciated. Something more to these in post #320 on page 16 and post #265 on page 14.
My board
1752945[/ATTACH]"]
