Had some health issues. Will get back to you as soon as I can. I bought from two or three different vendors as I recall just to hopefully get some that worked well, which I did.
Enjoy the benefits of a premium membership!
Upgrade Account
-
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 LT1097, and similar, will NOT give you the same sound and, possibly more important, will not give anywhere near the same battery life. Leo "designed" the sound, based on the COMBINATION of preamp and pickup, one without the other won't give you the authentic Stingray tone. Within the preamp, the poor high frequency response and slew rate of the 4250 is part and parcel of the design. Again, without the 4250, you won't get the authentic tone. Other components can be easily substituted but if you do a real time analysis of the boards, in connection with the pickup, the differences are both visual (on the response curves) as well as audible. When you use the 4250, battery life will be measured in years, essentially the shelf life of the battery. There was a reason the original battery cover of the Stingray was screwed down. I only changed my battery twice during the over 40 years I owned my '79 Ray. I knew it was time to change when the bass started sounding like it had a built in fuzz tone. Also, Leo didn't even use a TRS jack to turn off the battery. It wasn't necessary. The battery was on all the time whether or not a cable was plugged in.
No worries, take your time. Were you buying ones with 18mm shafts, with 6mm being the knurled end and the rest threads?
Hi everyone, I'm new here and joined the forum because of this topic. I'm from Portugal and want to buy a Harley Benton MB-4 or even an MB-5; those are passive MM-style basses. I got interested in this DIY Preamp to install on the bass. But when I went to Mouser, it says that the Link Removed, Link Removed, and Link Removed are not available/obsolete. I don't have so much knowledge about electronics in general, and I'm worse at electronics for music, but I'm looking for to being able to build it. I wonder if you could support me by indicating which components I can use as substitutes.
The 1uF and 10uF electrolytic capacitors can be substituted for alternatives - they're generic. I'd suggest getting 25V or higher components, though 10V or higher is all that's required.
As far as the LM4250CN goes, that part is no longer manufactured. They are getting scarcer but can be found on eBay (be careful of counterfeits) and some other online retailers. The USA or European based suppliers are more likely to have authentic ones. It is, however, the most important component and is key to the sound. Others have used LM4250CN clones like the NJM4250D with success.
Some of us sell pre-made replicas on eBay and Reverb. Good luck!
As far as the LM4250CN goes, that part is no longer manufactured. They are getting scarcer but can be found on eBay (be careful of counterfeits) and some other online retailers. The USA or European based suppliers are more likely to have authentic ones. It is, however, the most important component and is key to the sound. Others have used LM4250CN clones like the NJM4250D with success.
Some of us sell pre-made replicas on eBay and Reverb. Good luck!
I agree with what Boscoe said. I will add that the NJM4250 is an exact clone of the original LM4250 and works like a champ. If you don't use a 4250, you will NOT get the same results. Substituting other ICs will result in different tone and in some cases drastically less battery life. When used with a 4250, the current draw is something like 40 microamps (millionths of an ampere). In other words, a 9V battery will last as long as would if you kept it disconnected on the shelf, usually five years or so. Also, as Boscoe said, a number of folks on eBay, Reverb, and GearExchange sell the preamp all ready to go. If you don't know electronics, you might be better off buying something that you know in advance will work.
Thanks to all for the support.
I know that I could probably buy the preamp already assembled, but I'll use it also as a experience to get more knowledge about the bass electronics.
I know that I could probably buy the preamp already assembled, but I'll use it also as a experience to get more knowledge about the bass electronics.
@TriumphRider99,
Do you have any recommendations for a good MM pickups as GFS MM Pro? This one is currently out of stock.
Do you have any recommendations for a good MM pickups as GFS MM Pro? This one is currently out of stock.
So I found a store in Spain and bought 4 LM4250.
2x IC-LM4250CNNational Semiconductor LM4250CN, DIP8 case.
1x IC-LM4250CN-NOSLM4250CN / LM4250, NOS National DIP8
1x IC-NJM4250DJRC4250D / NJM4520D DIP8
Now I'm just waiting for the Mouser and OSH Park packages to start my building.
2x IC-LM4250CNNational Semiconductor LM4250CN, DIP8 case.
1x IC-LM4250CN-NOSLM4250CN / LM4250, NOS National DIP8
1x IC-NJM4250DJRC4250D / NJM4520D DIP8
Now I'm just waiting for the Mouser and OSH Park packages to start my building.
I wonder if there really is any difference between the LM4250 and something with better bandwidth (like the TL071). The bandwidth on the 4250 at the set-current used (a little over 10µA) is around 200KHz, according to the data sheet. This means roll off shouldn't occur at audible frequencies. I don't have a 4250, so I can't do any FFT's on real signals to compare. If the slew rate is about 0.2V/µs, then full swing at 1V output (so 2V p-p) should take about 20 µs. We have to cover this twice to make a full sin wave, so that's about 25KHz, max (at 1V output), before we start getting some type of distortion. 1V output is not unreasonable, and slightly more than what a strong humbucker will produce on its own , though it turns out that for frequencies above 4 or 5KHz, that the circuit can easily go above this for high treble settings. Probably why it starts to roll off at those settings.
Anyway, I did a simulation of the circuit with an LM4250 and a TL071 (since I have some of TL071's and they're cheap and that's what I'm using. I don't have any 4250's and they are really expensive and who knows if you get real ones). The plot I've attached shows what I got. Essentially, we don't see much difference until we get past about 97% treble, where the 4250 starts to roll off around 8 or 9 KHz, and the 071 has a slightly more gradual roll off. It doesn't really make much difference at all until about 98% or 99% (shown) treble, and at 100% the curves start diverging already at around 2KHz. My conclusion is that if you just put a 47KΩ (common value, 50K is fine too) resistor between the C2 (1.8 nf) and the treble pot (I tried it, it did what I expected), you'll never go above 95% treble and never experience any difference (at least not any bigger than you would get from just the natural variation in component values when you're ordering 10% or 20% caps, and 1% resistors from mouser).
As far as power consumption, the TL071 absolutely uses lots more power (like 3 or 4 times as much), so battery changes will be required. BTW, the SubRay4 uses the TL071, so if that's the bass you have (like me), it should be about the same battery life you already get.
As far as pickups making a difference, they most certainly do. I don't know the inductance or DC impedance of original Stingray pickups (I have a sub ray 4HH), nor the parasitic capacitance. That being said, most pickups usually have a peak where they resonate somewhere in the 3 or 4, or even up to 10KHz range (so, lots of variation!), after which they roll off. The low-pass filter formed by the parasitic capacitance and the DC impedance usually starts the roll off near the top of, or above audible frequencies (so above 20KHz), so probably not much effect from that. There is also parasitic capacitance in your guitar cable (patch cord), so that would bring it a little lower (longer the cord, the worse it'll be. If you can't tell the difference with longer cords, than it means the difference is not audible, so don't sweat it).
Simulations were with bass pot at 50% (varying this makes NO difference in the comparison, since it only affects lower frequencies), input is at 500mv. Frequency sweep is 20Hz to 20KHz.
My advice: try the TL071 or something similar with lower current draw if that bothers you about the 071 (use an 8 pin DIP socket where the opamp goes and plug it in after you solder, you can change out opamps that way without having to desolder). You probably won't be able to tell the difference, and if you can, put in a 47KΩ resistor between the 1.8nf cap and the treble pot.
Anyway, I did a simulation of the circuit with an LM4250 and a TL071 (since I have some of TL071's and they're cheap and that's what I'm using. I don't have any 4250's and they are really expensive and who knows if you get real ones). The plot I've attached shows what I got. Essentially, we don't see much difference until we get past about 97% treble, where the 4250 starts to roll off around 8 or 9 KHz, and the 071 has a slightly more gradual roll off. It doesn't really make much difference at all until about 98% or 99% (shown) treble, and at 100% the curves start diverging already at around 2KHz. My conclusion is that if you just put a 47KΩ (common value, 50K is fine too) resistor between the C2 (1.8 nf) and the treble pot (I tried it, it did what I expected), you'll never go above 95% treble and never experience any difference (at least not any bigger than you would get from just the natural variation in component values when you're ordering 10% or 20% caps, and 1% resistors from mouser).
As far as power consumption, the TL071 absolutely uses lots more power (like 3 or 4 times as much), so battery changes will be required. BTW, the SubRay4 uses the TL071, so if that's the bass you have (like me), it should be about the same battery life you already get.
As far as pickups making a difference, they most certainly do. I don't know the inductance or DC impedance of original Stingray pickups (I have a sub ray 4HH), nor the parasitic capacitance. That being said, most pickups usually have a peak where they resonate somewhere in the 3 or 4, or even up to 10KHz range (so, lots of variation!), after which they roll off. The low-pass filter formed by the parasitic capacitance and the DC impedance usually starts the roll off near the top of, or above audible frequencies (so above 20KHz), so probably not much effect from that. There is also parasitic capacitance in your guitar cable (patch cord), so that would bring it a little lower (longer the cord, the worse it'll be. If you can't tell the difference with longer cords, than it means the difference is not audible, so don't sweat it).
Simulations were with bass pot at 50% (varying this makes NO difference in the comparison, since it only affects lower frequencies), input is at 500mv. Frequency sweep is 20Hz to 20KHz.
My advice: try the TL071 or something similar with lower current draw if that bothers you about the 071 (use an 8 pin DIP socket where the opamp goes and plug it in after you solder, you can change out opamps that way without having to desolder). You probably won't be able to tell the difference, and if you can, put in a 47KΩ resistor between the 1.8nf cap and the treble pot.
Attachments
Last edited:
Thank you so much for the post. I was inspired by it to finally pull out one of the SBMM Ray4 preamps I have and trace it since this debate keeps coming up.
Normally when I upgrade a Sterling by Music Man Ray4 with one of the Boscoe Music MMSR77 replica preamps I sell I also replace the pickups. But on two separate occasions I kept the existing ceramic pickups. Both times I noticed quite the improvement in the sound. I always thought it was the TL071CDR opamp, but based on your post I thought I'd trace out one of the SBMM Ray4 preamps to see how far off from the original circuit they are in case I was mistaken.
The result: the SBMM preamps are almost identical to the original late 1970s circuit. There are only a few differences:
* They add a S1M diode (labeled LSE S1M) between BATT+ and pin 7, C9 (1uF electrolytic), R5 (2.2MΩ). I measured a .63V drop across the diode (9.4V at the pads, 8.77V delivered to pin 7). I'm not sure why they don't use a Schottky here.
* There is the 1kΩ protection resistor between the volume wiper and the output jack at R8. This was incorporated externally by Music Man starting in the early 80s but not on the original late 70s preamps. Started appearing on the PCBs in 1986. It can be bypassed on the SBMM preamp by soldering V2 to OUT directlly should someone somehow want to.
* C1, C6, C7, C8, C9 are all electrolytics, a mix of 16V and 50V. C7 and C9 have 50V electrolytics, so I think 18V would work? I defer to others with more experience here. The rest of the capacitors are ceramic.
* The input resistor (R1) is 200kΩ instead of 220kΩ from the late 1970s circuit as traced by Bajaman and the mid-90s two band traced by Howmuch.
* There is an additional 10kΩ resistor marked as R2 between R1 and the treble potentiometer wiper.
* Instead of the LM4250CN they use the TL071CDR
* C3 (treble cut) capacitor is 470pF instead of 510pF. Very minor difference.
* For some reason I'm not able to get a good reading on C4 (connects pin 2 to pin 6 on the opamp). It's somewhere from 100pF to 900pF. My understanding is that this cuts high frequencies and helps with RF interference, so I don't think this would be significant.
That's it! Unless somehow C4 is very important to the tone there are no significant differences between the 1977 preamp and the modern SBMM 2 band preamp - other than the opamp. That makes me think that the LM4250CN is the important factor. But I'm also not as experienced as many in this thread so please let me know if I'm missing something.
I will say that the SBMM 2 band preamp is a lot less forgiving on battery life than the original 1977 design. Not only are you using an opamp that draws about 4 times as much power, but with the .6V drop off from the diode the battery will get below the usable voltage a lot sooner. This fits with my experience as I had to change the battery in my SBMM Ray4 before but I've never changed the battery in the basses I've upgraded with my own preamps.
Note: the SBMM preamp has an unsoldered pad marked R7 that connects ground and pin 8 on the SBMM preamp. This would allow one to desolder the TL071CDR and replace it with an LM4250CN, along with a 1.5MΩ resistor at R7. You would then have a (close to) vintage spec preamp. I wouldn't recommend it though, as there's not a lot of room there to work in (you'd need a tweezer style iron for R7) and you'd expose the opamp to a lot of heat. But it's possible.
Attached are pictures of the SBMM 2 band preamp as well as the schematic I made. Feedback is welcome - others here are much more knowledgeable than I so please point out any mistakes I've made.
Attachments
I've just get my Mouser items, I'm still waiting for the Osh Park delivery. But I noticed that the current Link Removed I bought, has an ceramic capacitor (Link Removed) not a film capacitor like :
but
Would it impact on the sound? Should I buy the film capacitor?
but
Would it impact on the sound? Should I buy the film capacitor?
A film 47nF capacitor would be slightly better than ceramic, but you probably wouldn't be able to hear the difference.
Awesome that you traced that! Now I think we can finally answer this old question about why the new preamps don't sound right. The culprit seems to be R2 in your schematic, the new resistor they added (probably when they switched to TL071). It looks like they were trying to get the thing to roll off above 10KHz like it did with the 4250, so they threw in that 10KΩ resistor and called it a day. But look at that, it really starts to fall on its face above 97% Treble, as far as behaving like the old setup. It got me thinking, we need something that only kicks in the R2 as frequency climbs, so I added an inductor in parallel with R2. Initially, I just replaced R2 with an inductor (I'm referring to Boscoe's schematic here unless otherwise noted). I wanted something that would be around 10KΩ at 10KHz, which works out nicely to 1/(2pi), so about 150mH. That didn't look quite right, so I ended up putting R2 back in parallel with the inductor and tweaking the values until I liked it. In the end, I got 90mH, with R2 at approximately 6.5KΩ (in the end I used 6.667KΩ because that's 10K in parallel with 20K, so easy to do with stuff in my drawers, and no noticeable difference). Here are some simulation results (I'm still just leaving the bass pot at 50%, changes to it don't really make a difference as far as traces matching each other goes):
The SubRay4 (as Boscoe traced for us) vs. the original with 4250. Note the bass response of the SB4 is slightly higher than the original.
The SubRay4 modified with R2=6.67KΩ in parallel with a 90mH inductor. I'm liking that treble curve... but the bass of the original (mnats schematic) could be matched better.
So, let's try the mod (R2 || 150mH) on mnats original with a TL071. I'm liking that.
Here's all of it at once.
So what can we learn from this little rabbit hole we've gone down? I think I will try the mod of adding 6.67KΩ in parallel with 90mH of inductance between the wiper of the treble pot and the board, along with a TL071 on mnats' PCB, which I have from OSH Park.
Also, thanks to Boscoe, we finally know what the amp on the subrays is doing. We also know now that we can just reuse the pots that are already in the bass (I like the little detents they have, and damn if getting the knobs off doesn't seem worryingly difficult). I think one could bodge together a parallel combo of a 20KΩ resistor and a couple of inductors in series to add up to 90mH and install it across R2 on the subray's board, but those little smd components are tight, and it sounds like a lot of fussing just to make a mess in the end.
I'm a little worried that adding inductance into the feedback path could cause some shenanigans, since the feedback is to the input and there's a big pickup sitting on the other side of that 1µf cap. That's why, in general, I don't like to do feedback to the input if I can help it, you can end up with oscillations you weren't expecting. I suppose I should mock up the pickups and run everything again, but I also kind of want to get out of this rabbit hole. I can post schematics if someone is interested.
Almost forgot to mention the diode in the new boards. Maybe they wanted to protect it from someone putting the battery in backwards?
Also, I couldn't find any 90mH inductors on Digikey (didn't try mouser). There are 22mH and 68mH available, and indicators add in series. They list the DC impedance on them, you can get them below 100Ω. I added that in to the simulations, no effect.
Update: I couldn't leave it alone. I simulated it with pickups, assuming 700mH (2X1.4H in parallel), 2KΩ, and 120pF. The frequency response is definitely different, but the modification still does the trick. The inductor was changed to 120mH. The tldr is that the added inductor doesn't cause any troubles, and matching the 4250 is fairly robust against changing pickup parameters. I'll post some plots the next chance I get. If anyone knows good values for L,R,C, of the original and subray pickups, I'd love to know.
I opened up my subray and measured the pickups. I have the HH model, and the coils are broken out individually to the selector toggle, but they are indeed wired in series. It would be easy to change them to parallel, though I've read that for some other models, the coils are wired in series and it's all sealed in epoxy, with only two leads coming out.
Anyway, 3.2KΩ per coil, that's 6.4KΩ in series. C is about 140pF, and due to the physics of how parasitic capacitance works in this situation, it adds in parallel regardless of whether your pickups are wired in series or parallel. I took the inductance to be 1.4H per coil, as per the wisdom of the internet (dubious, I know, but given the values for R and C, not unreasonable). So that's 700mH in parallel and 2.8H in series. Plots follow:
This is 85% treble:
85% treble, wired in, parallel
85% treble, wired in series.
90% treble, parallel
90% treble, series
95% treble, parallel
95% treble, series
100% treble, parallel
100% treble, series
The purple lines here are because the LM4250(blue) and the TL071, compensated with R||L modification between treble wiper and input to opamp (red) are on top of each other or on adjacent pixels for the most part, making magenta. Plots are log/log. The biggest takeaway for me here is that the series vs. parallel gives a shift in resonance from about 2KHz (series) to about 4KHz (parallel). That's probably the biggest difference people hear between the subray and the old stingrays.
I also measured where the wiper on my treble pot was W.R.T. its adjustment position.
Detent (1/2 way 'round): 90% treble.
3/4 of the way 'round: 95%
7/8 of the way 'round: 99%
So, we're spending most of the time (at least I am when I'm playing) in the range where subray preamp (and the original with a TL071, but not shown here) starts to really stray from the original amps with original pickups (i.e. it falls on its face here).
I feel like I pretty much understand what's going on now, and what the contributions are of the different pickups and preamps are. I for one, like the way my stock subray sounds actually, but I did order some inductors and some 6.65KΩ resistors from Digikey that I will wire up (in an easily swapped out way) to the board that started this thread to begin with, along with a TL071 in place of a 4250. If anyone would be interested, I think I would enjoy making up a PCB to submit to OSH Park with holes and traces for the new components, and for the 1.5MΩ resistor that the 4250 requires. One could just jumper holes that take the compensation bits, and plug in a 4250 (and add the 1.5MΩ resistor) if they don't like it with TL071 with compensation.
And just a last thought, and I'm surely not the first person to think it: The fact the the subrays can get clippy with the volume all the way up is probably because of the series wiring in the pickups. It's not portrayed in the simulations because I didn't change the input driver for the different pickup values, which loses the amplitude changes across those differences. I would say that the series pickup is probably a lot hotter than the parallel.
Anyway, 3.2KΩ per coil, that's 6.4KΩ in series. C is about 140pF, and due to the physics of how parasitic capacitance works in this situation, it adds in parallel regardless of whether your pickups are wired in series or parallel. I took the inductance to be 1.4H per coil, as per the wisdom of the internet (dubious, I know, but given the values for R and C, not unreasonable). So that's 700mH in parallel and 2.8H in series. Plots follow:
This is 85% treble:
85% treble, wired in, parallel
85% treble, wired in series.
90% treble, parallel
90% treble, series
95% treble, parallel
95% treble, series
100% treble, parallel
100% treble, series
The purple lines here are because the LM4250(blue) and the TL071, compensated with R||L modification between treble wiper and input to opamp (red) are on top of each other or on adjacent pixels for the most part, making magenta. Plots are log/log. The biggest takeaway for me here is that the series vs. parallel gives a shift in resonance from about 2KHz (series) to about 4KHz (parallel). That's probably the biggest difference people hear between the subray and the old stingrays.
I also measured where the wiper on my treble pot was W.R.T. its adjustment position.
Detent (1/2 way 'round): 90% treble.
3/4 of the way 'round: 95%
7/8 of the way 'round: 99%
So, we're spending most of the time (at least I am when I'm playing) in the range where subray preamp (and the original with a TL071, but not shown here) starts to really stray from the original amps with original pickups (i.e. it falls on its face here).
I feel like I pretty much understand what's going on now, and what the contributions are of the different pickups and preamps are. I for one, like the way my stock subray sounds actually, but I did order some inductors and some 6.65KΩ resistors from Digikey that I will wire up (in an easily swapped out way) to the board that started this thread to begin with, along with a TL071 in place of a 4250. If anyone would be interested, I think I would enjoy making up a PCB to submit to OSH Park with holes and traces for the new components, and for the 1.5MΩ resistor that the 4250 requires. One could just jumper holes that take the compensation bits, and plug in a 4250 (and add the 1.5MΩ resistor) if they don't like it with TL071 with compensation.
And just a last thought, and I'm surely not the first person to think it: The fact the the subrays can get clippy with the volume all the way up is probably because of the series wiring in the pickups. It's not portrayed in the simulations because I didn't change the input driver for the different pickup values, which loses the amplitude changes across those differences. I would say that the series pickup is probably a lot hotter than the parallel.
Last edited:
Wonderful work @mlrogers! As far as the clipping goes, I've also noticed that the clipping goes away once the pickup is rewired from series back to parallel.
Just now (like 1/2 hour ago), I puzzled out how to wire my HH to do parallel, with middle position as both. I've done away with the two intermediate spots, I never really liked the two inner and outer settings to be honest, and I don't want to wrack by brain figuring out how to keep it. Also, I made up a PCB to accommodate the compensation that I simulated, to use a TL071. It's designed so you can do the 071, or the 4250, and with or without compensation. I'll submit to OSH Park today and order some boards to try it. If it's good, I'll post the extra parts to order and the link to the board on OSH Park. Anyone who wants to try before I've proofed it, just say so and I'll post links to the board on OSH Park and the extra parts at Digikey.
As an aside, the middle position on a stock HH is a series parallel combo, and has lower inductance than either pickup alone. This brings the treble peak from about 2KHz to about 3KHz (original Stingray should be about 4KHz, according to my simulations). No wonder it's the only setting I really like. I will keep this combo for the middle position with my rewiring.
There's a great thread here on TB on how to rewire the HH StingRays to parallel. It worked great for me.
I recently modified my SBMM Ray4 HH with series/parallel switches, and because there didn't seem to be any wiring charts for this model or this modification, I thought that I'd make some for the benefit of others who might want to do the same thing.
Here is the stock pickup wiring diagram for reference:
And here is the modification wiring I decided to use, in order to disturb the existing wiring the least. In parallel mode for both pickups, the volume level is consistent across all 5 switch positions, which is great. Also, a bonus feature is that you can get a few lone...
Here is the stock pickup wiring diagram for reference:
And here is the modification wiring I decided to use, in order to disturb the existing wiring the least. In parallel mode for both pickups, the volume level is consistent across all 5 switch positions, which is great. Also, a bonus feature is that you can get a few lone...
Latest posts
-
-
Adding J pup to P bass, should I go 60’s or 70’s spacing?- Latest: Gianni "Orlandez" Orlati
-
-
-
