Baja Music Man guitar and bass onboard preamps [documentation]

[Dix]

Regarding these pickup models done in Spice, etc. They are close, but never really on the mark. Pickups are complex impedance devices. You can do high inductance and low resistance, and get a nice clear tone, or higher resistance and low inductance for a similar tone.

That may be true (again, I'm not a pickup winding expert by any stretch), but in my experience the StingRay preamp doesn't react well to high anything, inductance and/or resistance... it wants both low inductance and low resistance... nature of the beast it seems.... my best guess is that they were designed to complement each other & specifically around each other... at least that would seem to make some logical sense... given what I've found... there may indeed be other ways to skin the cat... but for that classic "StingRay sound" that was all over rock radio in the late 70s & early 80s I haven't been able to make it come out of one with anything but having the pickup coils wired in parallel... giving a low inductance and low DC resistance.

The modeling I've done recently with Bajaman's circuit just confirms & makes some sense out of my experience... not the other way around.

In the last decade I've had a couple of 'em brought to me that didn't sound "right"... none with original MM pickups... where they went and why is anyone's guess.

One with a pickup in it much like the one Jay is working with... a 4-wire copy that was wired in series... rewired it in parallel & that cured it.

Another where the owner thought it sounded "OK", but not all that deserving of the hype he'd read about (he'd bought it off eBay).. told him it didn't sound right to me so he told me to check it over... found a cheap knockoff 2-wire pickup that measured about 8.5K DC resistance... he stuck a Duncan replacement in it & was a happier man as he then "got it".

Then there was a 3rd one that was found (no lie) at a yard sale with no pickup in it, no strings on it, & no case (but otherwise in decent shape actually), purchased for the whopping sum of $20 & brought to me to see if it could be brought back to life (this one was just last summer)... owner opted to buy the EMG pickup (which I found had to be rewired for parallel), I replaced the battery connector & fixed a couple bad solder joints on the board... then after a few tweaks to the bridge height & intonation it was the 1980s all over again.

The only thing I really knew about the MM pickups until recently was that they were a dual coil wired in parallel & it's pretty common knowledge that parallel wired coils sound different than series... so I was just copying the MM format of making sure the coils were in parallel... not realizing until recently that the pickup wasn't the only trick up the SR's sleeve.

I didn't realize until I've had the chance to play with the circuit (again, thanks loads to Bajaman for that) how much the preamp's output is affected by it... or more correctly, ill-affected by a series configuration with it's higher resistance and inductance... all I knew was that it sounded like a SR when the pickup was wired in parallel... in series, not so much.

[deltafred]

I found that the main reason for the cheap pickups sounding 'dark' was because of the mild steel pole pieces that were used (instead of silicon steel that has a lower magnetic hysteresis).

As I mentioned in a previous post I replaced the bar magnet and mild steel pole pieces (on a JHS Vintage MM style pup) with 8 individual neo magnets and it made the world of difference.

I would not recommend that on an OLP pickup because the windings are straight onto the magnets (rather than on a former) so you stand a good chance of breaking the wire when you press out the pole pieces.

I own a Stingray 5 and a (USA) SUB 4 so know what sound I was aiming for. The modified MM pickup is a lot closer to the sound now than it was before I modded it.

[DavidRavenMoon]

The real pickups don't have steel poles. They are alnico magnets. Steel would have higher inductance. Generally pickup poles are low carbon steel. Harder steel has a brighter and somewhat harsher tone. The steel used in things like PAF screw poles has lead in it.

I'm a pickup maker. I've also been making these preamps for several years. An interesting aspect is the preamp is as much a part of the Stingray tone as the pickup. I have one of these preamps in my '87 Ibanez 5 string with neodymium j style humbuckers (dual blade) that I make. If I cranky the treble control it sounds very much like a Stingray.

The main thing with the pickup is keep the bobbin dimensions the same, use the big alnico 5 magnets, and don't wind the pickup very hot. In parallel it's a medium/low impedance pickup.

They aren't hard to copy... If you can get the parts.

We can analyze pickups, but Leo didn't do that when he created it. He just wound the number of turns he felt would get what he wanted based on his experience as a pickup maker. Plus he was going deaf! So his pickups got brighter and brighter as time went on!

[JayGunn]

Really good news that my pickup is in the ball park of an original. I looked online and discovered what you guys have been saying. There are Asian 2-wire pickups as well as 4-wire. For under $80 you see "wound to 11K", "13K", even one that claims "8 henries", which if re-wired in parallel would be 2H, more than double the 0.7H you guys are reporting in a stock pickup. These budget pickups are meant to produce reasonable output without a preamp.

All the pickups I have seen that claim to match original specs are quite pricey, beginning with Seymour Duncan, then Bartolini, Nordstrand, Aguilar, Delano. Out of my budget unless I become desperate.

I am sticking with my GFS and hope to hear it play in a week or two. Just have to breadboard the preamp. You guys are great!

[deltafred]

The real pickups don't have steel poles.

Yea I know that (I own 2 MM basses), but most of the cheap clone pickups are a bar magnet and mild steel pole pieces rather than alnico magnets.

Years ago when I was playing around with pickups I did look up the spec for the steel used for pole pieces (when a bar magnet is used) but the number escapes me now, as do a lot of things I used to remember!

[bajaman]

The steel used in things like PAF screw poles has lead in it

Well that is interesting news David - 12L14 perhaps ? I have noticed that nickel screw poles give noticeably brighter response than unplated 1018 and 1022
Lindy Fralin uses plated screw poles in his P90 and PAF style pickups - Angela Instruments sell these on Ebay ( https://www.ebay.com/itm/310318130888?_ ... EBIDX%3AIT ). It sure would be interesting to know what composition they are
cheers
bajaman

[Dix]

I have one of these preamps in my '87 Ibanez 5 string with neodymium j style humbuckers (dual blade) that I make. If I cranky the treble control it sounds very much like a Stingray.

Ditto what I can get out of the Gibson Victory Artist... which then relegated the SR to backup status... is it a "perfect" SR match?... well, not really... but for a few hundred drunks in a club it was close enough & the Victory is more versatile.

If I'm following what you've been getting at regarding pickup construction (which is always questionable)... in general, more magnetic mass equals higher inductance.... correct?

Just wondering out of curiosity with regard to the 2 versions of the pre-EB pickup... the 1st version had longer magnets & a lower DC resistance... now, if we assume the higher DC resistance of the 2nd version was done by simply adding more windings, would the shorter magnets (less magnetic mass) bring the inductance back down closer to the original's than would otherwise be the case if the same magnets were used?

[Dix]

These budget pickups are meant to produce reasonable output without a preamp.

Which actually makes a little sense in all reality... likely the biggest reason for someone wanting a cheap replacement pickup would be due to the preamp calling it a career... & since the pickup has such a low output you can't just bypass the preamp & wire it passively (although, if you rewired the original pickup in series you might get away with it... never tried it)... this includes EMG's replacement I guess... if you check the instruction sheet that comes with it, that details wiring it passively without the preamp.

I own a Stingray 5 and a (USA) SUB 4 so know what sound I was aiming for.

Unfortunately I think guys like you & I are a minority these days... all 3 of the above used/abused SR owners I mentioned weren't even born by 1980... well, maybe the last one, I think he was almost 40.

For those who have never had the pleasure, forget the YouToob garbage, listen to a good quality copy of Michael Jackson's "Billie Jean" (& NOT on your crappy computer speakers)... for one example of the StingRay's most famous hits... Louis Johnson recorded his "Thriller" tracks with a SR.

If Michael Jackson isn't something that's in your wheelhouse, how about something by Journey off of "Escape" or "Departure" (Stone in Love, Don't Stop Believin', Separate Ways) or Forienger's Head Games/4/Agent Provocateur era (Head Games, Juke Box Hero, Waiting for a Girl Like You, That Was Yesterday).

All of the above were recorded with a StingRay.

SR users of the late 70s/early 80s reads like a "Who's Who" of pop/rock radio of the time period... John Deacon (Queen), Ben Orr (Cars), Tom Hamilton (Aerosmith), Cliff Williams (AC/DC), John Taylor (Duran Duran/Power Station), in addition to the above noted Johnson, Valory & Wills is the SR "short list".... all of 'em recorded some of their biggest hits of the era with it.

In fact, the SR all but replaced the Fender Precision as the "go-to" pop/rock bass from 1979 to about 1985-ish... & the reason (IMO) was pretty simple... you could take a direct feed from the bass to the mixing desk & unless the engineer was a complete idiot you could lay down a decent bass track that sounded good & cut through even the "busiest" of mixes with minimal fuss & added processing.... something that can't be said of most other basses of the era... including "that one" mentioned above that everyone else fawns over, & I learned to hate... go ahead, call me a heretic. (when you go to Baskin-Robbins do you order vanilla?)

Believe it or don't, that's exactly how many of the above famous tracks were recorded... The SR's reputation & place in rock history is well deserved... even if I do happen to think it's something of a "one trick pony"... still, at the time it was a pretty damn good trick.

If that sounds a bit schizophrenic... well.. it is... I look back at the SR like the 1st girl that ever let you go "all the way"... sure, it felt great & you thought you were in love... but you eventually broke up with her & then met someone that knew what she was doing & how many other pleasureable things could be involved.

By 1985 or so other options came along that not only duped the SR's trick, but were more versatile & had better preamps that were less "wonky" so it's popularity faded somewhat.

Sorry this turned into a somewhat lengthy rant & trip down memory lane.... I get carried away sometimes.

[DavidRavenMoon]

The steel used in things like PAF screw poles has lead in it

Well that is interesting news David - 12L14 perhaps ? I have noticed that nickel screw poles give noticeably brighter response than unplated 1018 and 1022
Lindy Fralin uses plated screw poles in his P90 and PAF style pickups - Angela Instruments sell these on Ebay ( https://www.ebay.com/itm/310318130888?_ ... EBIDX%3AIT ). It sure would be interesting to know what composition they are
cheers
bajaman

Yes, 12L14, or similar, as they were just off the shelf screws. A few years back some of the guys at the Pickup Maker's Forum had an old PAF screw analyzed and had a bunch of them made. It was some slightly different formula of steel. I got a bag of them, and they do sound different from the typical pole screws you get. But would you actually tell the difference in a band setting? Probably not.

Otherwise the usual steel used is 1018, etc. Nickel is ferromagnetic. But is nickel plating actually pure nickel? Nickel 5 cent coins are nickel silver, so they are 75% copper and 25% nickel, so they aren't magnetic (even though dimes and quarters are, and only have 8% Ni). Also odd that adding nickel to steel to make it stainless steel renders it non magnetic.

[DavidRavenMoon]

If Michael Jackson isn't something that's in your wheelhouse, how about something by Journey off of "Escape" or "Departure" (Stone in Love, Don't Stop Believin', Separate Ways) or Forienger's Head Games/4/Agent Provocateur era (Head Games, Juke Box Hero, Waiting for a Girl Like You, That Was Yesterday).

Didn't Ross Valory play an Ovation Magnum bass on that stuff? I can't find a single photo of him with a Stingray, although later on he had a 2 pickup Musicman. Before the Ovation he played a P bass.



And Rick Wills plays a P bass. Here he was on stage with FOREIGNER January 1979.



Don't forget the amazing Bernard Edwards! That's his bass that John Taylor from Duran Duran has.

[Dix]

What gets played on the road was not always what was used to record the album.

On the road for the Head Games tour, Willis did use a P (remember, we were all still a little skittish about batteries going dead while playing live back then)... but recording up through Agent Provocateur was a SR... not sure about Inside Information & beyond.

I screwed up on Valory though, you're partly right... Escape was the Ovation & I meant "Frontiers" (1983) not "Departure" (1980).... The Ovation was auctioned off, it's in the UK now.... somewhere after the SR & Frontiers there was a Steinberger period in there somewhere... recent pics show him using the Sabre.

Incidentally, the Steinberger "craze" (as I like to call it) was likely one of the biggest reasons for the SR's wane in popularity.... if you could get past the feeling that you were playing a "plastic stick" it had low impedence pickups like the MusicMans & a better preamp.

[DavidRavenMoon]

I always liked the Steinbergers just because they were so different. I've met Ned, he's a nice guy, and sharp as a tack. I played a Rick 4001 for years, so I wasn't a Fender guy, even though I had a '74 P bass. The misconception about EMGs is they are not low impedance pickups. They are pretty much the same as the HZ passive versions. Only the two coils are wired into the preamp in a differential fashion, so they aren't in series. So for the EMG split coil humbuckers in the original Steinberger, it was about 5k DC resistance. They were essentially P bass pickups, but of course they sound much brighter. The original Steinbergers had Bartolini pickups.

I used to use EMGs in the basses I built, since we used them at American Showster when I worked there in the mid 80s. I used them precisely because I assumed they were low Z like Alembic pickups. But after about 10 years I got tired of the way they sounded. Every bass you put them into sounds like it has EMGs. So I made my own true low Z pickups. Now I could hear what the bass sounded like! Incidentally, the EMG DC was intended to sound like a Musicman. It does a good job if you place it in that same position on the bass. It's to edgy sounding in the usual bridge position.

I always liked Stingrays. I like G&Ls too. Leo took that pickup concept and went even brighter! But I was playing Ricks, so I never felt the need to get one. I had a preamp in my Rick in 1976. Back then you had to take all the screws off the pickguard to change the battery! lol Probably why Leo made the Stingray's preamp to consume so little current. They didn't even switch the battery off in the beginning.

[bajaman]

They didn't even switch the battery off in the beginning.

ha ha - i had a customer bring his bass amplifier and speakers in for me to check over - he claimed he was getting really bad distortion. i tested them both and found no problem so i asked him to bring his bass (a stingray) and cable over to check. First up I asked him if he had ever changed the battery in the bass (he had owned if for a few years) - his reply was that he never knew it had a battery fitted (it measured 2.5v ). Changed the battery and voila, all good again - lol.

[PaulBass]

If you have an OLP bass you don't have to pay $150 for a boutique pickup. The tone of the GFS Alnico is killer. They are 2K resistance which is close to the SR spec. GFS must have good quality control and really pay attention to the tone of their pickups. I have them in 3 basses with homemade SR and Sabre preamps. Then use better components in the signal path like metal film, silver mica and bipolar caps. I also use better chips like the LT1351 and LT1354 and run them at 18v

[Andy_]

I'd like to correct my posting above about measuring the inductance...

A better way would be, to first measure the dc resistance, than download the attached zip (pickup.zip) and load it with OrCad's free simulator. Change R1 to the value just measured.

1.png (3.99 KiB) Viewed 3062 times

Then find the resonant frequency of the circuit, start the attached simulation and find the trace that matches your frequency - this one will show your inductance.

Regards
Andy

[JayGunn]

I am close to getting the electronics finished for the P/MM bass I'm building. After lots of deliberation I decided to buffer the P pickup, create a variation of the MM 2-band pre dedicated to the GFS MM alnico pickup I just bought (and I'll compare it with their ceramic one later), then send the 2 outputs to a blend and a volume control.

Here's the prototype 2-band preamp with one cap missing (added it after the picture) it has 4 extra resistors which I'm using to reduce the +-12dB treble range and also reduce the bass range as well. I'm reasoning that if you like the sound of the pickup you should not need such drastic gain and cut, and by reducing the range the adjustment will be less wildly sensitive...



I'm hoping you guys who are familiar with simulations can help me with the other part of the project--a simple buffer for the P-bass pickup (it's actually the pickup from a Squire VM P-bass). Here's my sim that looks like I expect it to. Note that the feedback resistor is set for less than unity gain (R2 < R1) and output is around 0dB as expected:



BUT now I increase R2 to match (or exceed) R1 and see what happens to the output. I expect the output to go above 0dB. The Vout in both sims is at the point marked OUT, i.e, at the top of R5. Any suggestions? It isn't the op amp model I know because I have tried others, and this op amp is an LT part, so their model should work fine in their version of Spice.

[DavidRavenMoon]

Buffering any pickup with an impedance higher than the parallel MM pickup is a good idea. I use one of these MM preamps in one of my basses that use more conventional pickups. You lose top end because of the low input impedance. Of course that can be regained with the treble control, but it's not quite the same. I might be removing the preamp from my bass today until I can build a different preamp.

Also, the controls are not quite boost/cut. The bass control is mostly boost. And it's kind of mild. I leave it boosted about half way most of the time. The treble does a little cut, but not like a standard active tone control.

Why are you using a feedback resistor for a unity gain buffer? And why the 33k series resistor? Use a circuit like this. Or a JFET.

[JayGunn]

David, thanks for your quick response.

I went for the inverting buffer because the MM preamp is inverting. Seemed kind of rational and symmetrical that buffer and preamp outputs are in phase on their way to the blend control. Of course I could reverse the polarity of the P or the MM pickup wiring to bring the 2 pickups back in phase. So then I could use your non-inverting buffer, which I'm sure will work (but will it sim okay in LTSpice(?)

I can also use my own simulated inverting buffer and stick to the resistors that 'work' in the upper simulation, but I'm really hoping a sim expert can tell me why the second sim, which looks correct to me, loses 50dB. Maybe just a newbie misunderstanding, but almost every article about op amps starts with buffers as an example of op amp usage, and they all show the R1=R2 design as producing unity gain, not 50dB loss. Inquiring minds want to know...

[DavidRavenMoon]

I never thought about the fact that the preamp was inverting? I wouldn't really worry about it. How do you know if the pickups are in phase anyway? There are no standards set for that, only for two pickups together.

Are going to mix those two pickups together and into the preamp? If so, you can't just buffer the P. The output impedance of the buffer is low, so you'd have to buffer both pickups separately, and then mix those outputs. And the P has a lot more output.

I used to make low Z pickups that worked like that. I used a simple JFET buffer to also boost the level up. Of course buffering the MM will raise it's resonant peak.

I don't use sims, even though I have MacSpice. I prefer to just cobble together the circuit and see how it sounds.

Here's an inverting buffer. and many more types here: http://www.muzique.com/lab/buffers.htm

[Andy_]

@JayGun:

You forgot the input cap and now the pickup loads v/2
Just complete the circuit and the sim will show what you expected...

Regards
Andy