Mod your cheap pickups

[Jim Williams]

Them was "The Days of Lines and Noses". I was working with Rex Bogue back in the mid seventies during the time of Alembic, Rick Turner and Ron Wickersham. We would meet up at the Namm show at the Disneyland hotel. Rex would plumb competitors with cocaine for information. Rick and Ron were world class consumers. I would watch with amazement.

We were building custom guitars and electronics, Mahavishnu John McLaughlin had a Bogue double neck. We marketed on board guitar electronics that I designed.

We did weird stuff like Frank Zappa's Hendrix strat we rebuilt from pieces. It was featured on the cover of Guitar Player and had preamps with piezos glued into the headstock. You can hear all that stuff on Frank's 1970's releases. We used coils made in a local aerospace company to create individual output pickups. We built stereo guitars with string pan pots.

I use an acoustic bridge pickup system that sounds very natural compared to piezo pickups. It's a condenser/capacitor element, not a piezo. It's made by B-band and it's a very thin strip that fits under the saddle. I used a new low noise AD CMOS chip and it's very clear and quiet. It does the acoustic sound well without the piezo clack.

[douglas baldwin]

Oh boy oh boy oh boy. This is some of the most exciting stuff about pickups I've read in a long, long time.

Re. Michael Joly's description of

"string return" acoustic guitar pickups (a single Alnico magnet under the strings, the strings wired in series and fed into a current amp, best amplified acoustic sound I've ever heard).

I am wondering: okay, I place a magnet near a string and I wire one end of the string to a positive lead and the other end to a negative or ground lead (or I wire two or more strings in sme kind of series/parallel combination). I wire these leads up to some kind of transformer like a turntable pickup transformer. I am a dense guitarist with some decent soldering skills but little formal engineering or electronics background. Could you tell me a Mouser part number, or specs for this transformer - just a clue as to where to look? If I can get that much going on, then I'll look at adding a preamp... (clues, anyone?)

I just want to build this, and hear this, and experience this. So. Bad.

Unfortunately, my parents weren't rich diplomats so I missed that particular boat....

[Jim Williams]

Any current to voltage conversion scheme should work. Something as simple as an inverting opamp would do it. You will need to feed the signal into the inverting input pin and let the feedback resistance create the voltage/gain from it. An inverting opamp with a pot as the feedack resistor should do it.

A bootstrapped jfet would probably be best for current noise specs. You would need a real quiet jfet and a quiet opamp to work with a decent s/n ratio. Since the signal is weak, don't expect world class noise specs from this topology.

[ubertar]

Oh boy oh boy oh boy. This is some of the most exciting stuff about pickups I've read in a long, long time.

Re. Michael Joly's description of

"string return" acoustic guitar pickups (a single Alnico magnet under the strings, the strings wired in series and fed into a current amp, best amplified acoustic sound I've ever heard).

I am wondering: okay, I place a magnet near a string and I wire one end of the string to a positive lead and the other end to a negative or ground lead (or I wire two or more strings in sme kind of series/parallel combination). I wire these leads up to some kind of transformer like a turntable pickup transformer. I am a dense guitarist with some decent soldering skills but little formal engineering or electronics background. Could you tell me a Mouser part number, or specs for this transformer - just a clue as to where to look? If I can get that much going on, then I'll look at adding a preamp... (clues, anyone?)

I just want to build this, and hear this, and experience this. So. Bad.

Unfortunately, my parents weren't rich diplomats so I missed that particular boat....

I had transformers specially made for this purpose from the same company that makes the transformers for my hexaphonic turbo boxes and the ubertar ribbon mics. There's no need for a preamp.
PM me.

[Michael_Joly]

As Ubertar noted a ribbon mic transformer will work. With a transformer this pickup has a much better signal to noise ratio than your typical ribbon mic. Because, think about it - the aluminum ribbon is responding to air velocity changes while the coil in a string return pickup is actually getting whacked by a pick. So the signal portion of the equation is huge compared to a ribbon mic.

Do this - buy an Apex 205 and a Lundahl LL2913. Put the Lundahl in the mic and take the cheap ribbon transformer from the 205 and use it for the string return pick up. You'll have a great ribbon mic and a new acoustic pickup for under $200. Or get the Lundahl from Kevin Carter for $65 and you're good.

[ashcat_lt]

Being impatient for a reply re: the string return pickup, I posted about this over on the GuitarNuts2 forum hoping somebody over there had some insight. In response I was asked to address something else that was mentioned earlier in this thread: specifically the capacitor in place of the string ground.

This cap will not block AC leakage current. It might attenuate it somewhat. Maybe even enough to stop the sparks flying when you step up to the mic for your talkbox solo. Please don't count on it to save your life!

To the extent that there is any "isolation" from this cap, it will only apply (as described) to the strings and bridge. Especially on a Tele (properly shielded and wired), there are plenty of other metal things you can touch which are connected to the amp chassis: the neck pickup cover, the control plate and knurled steel knobs, pickup and pickguard screws... It is possible to wire it so that all of these things are also on the "safe" side of the cap, but that still leaves the jack, jackplate, and the cable itself.

On top of that let's look at the less likely but far more dangerous situation where the "death cap" blows shorted and drops an extremely large DC voltage onto the amp chassis. Being DC, it should be blocked completely - less any leakage current through the cap. Unfortunately, this voltage is likely to exceed the 250V rating specified for the cap by quite a bit. So it's likely to blow shorted, and connect the player directly to the amp chassis. AFAIK there aren't any documented cases of death caused by this particular fault, but it could happen.

The only way to be completely safe from all shock hazards while playing your guitar (won't help you when touching the amp itself) is to completely remove the conductive path between guitar and amplifier. That means going wireless. If that sounds too much like big hair and spandex for you, there are things you can do to minimize the risk.

First - "destroy the resale value" of your vintage amplifier by having a professional replace the two pronged devil's tail with a three pronged AC plug and properly wired safety ground.

B - keep your amp maintained. Replace old capacitors and such to avoid the fault mentioned above.

III - Carry an outlet tester and GFCI power strip everywhere you go. Use the outlet tester first. If it indicates a problem with the wiring pack up and go home. If it says things are okay, plug in the power strip and plug the amp into that.

Here's a pretty good article re: Shock Hazards from the original GuitarNuts site, and here's a supplemental post from the forum.

And another thing about that capacitor. Remember how I said it attenuates the AC flowing between the strings/bridge and the amp? Well this works both ways. That is, it will also attenuate the low frequency noise signals which we want to follow this path to ground so that they stay out of our pickup signal. In a well-shielded guitar this might not be so much of an issue, but it's something to keep in mind.


Back on the String Return Pickup. I'm still having a little trouble visualizing this. I can't really see how the strings could be wired in series. What happens when you fret more than one string at a time, or - worse yet - bust out your big brass slide? Seems this would short across the strings, no?

[ubertar]

Back on the String Return Pickup. I'm still having a little trouble visualizing this. I can't really see how the strings could be wired in series. What happens when you fret more than one string at a time, or - worse yet - bust out your big brass slide? Seems this would short across the strings, no?

To connect them in series, you have some foil at or behind the nut that connects the strings together electrically. It doesn't have to be foil-- just anything that makes an electrical connection between all the strings. Then you connect every other string to positive, and the remaining strings to negative. Each adjacent pair of strings makes a circuit-- E and A, D and G, B and E. When you use a metal slide, or press down at the frets, it does short the circuit, but all you lose is the part of the string you're not using musically, so it's not an issue.

[ubertar]

As Ubertar noted a ribbon mic transformer will work. With a transformer this pickup has a much better signal to noise ratio than your typical ribbon mic. Because, think about it - the aluminum ribbon is responding to air velocity changes while the coil in a string return pickup is actually getting whacked by a pick. So the signal portion of the equation is huge compared to a ribbon mic.

Do this - buy an Apex 205 and a Lundahl LL2913. Put the Lundahl in the mic and take the cheap ribbon transformer from the 205 and use it for the string return pick up. You'll have a great ribbon mic and a new acoustic pickup for under $200. Or get the Lundahl from Kevin Carter for $65 and you're good.

While a ribbon mic transformer will work, it's not ideal for plugging into a guitar amp-- unless you use one from a high impedance ribbon mic, and as far as I know, nobody makes those anymore. If you're planning on plugging into a mic preamp, a regular ribbon mic transformer will be fine. The transformers I have were designed for plugging into a guitar amp. If anyone wants one, let me know. They're brand new, and I'll let them go for $10 each.

Another tip: use brass end pins and you can solder leads from them to your transformer-- that way everything can be inside your guitar and out of sight. Elderly instruments has them for cheap ($9 a set, last I looked).

[Nathangrn]

One of these plates from Stewart MacDonald or something like it would work well also.

http://www.stewmac.com/shop/Bridges,_ta ... _Mate.html

[ubertar]

One of these plates from Stewart MacDonald or something like it would work well also.

http://www.stewmac.com/shop/Bridges,_ta ... _Mate.html

Actually, no... that would connect all the strings together. You want to do that at the nut, but not at the bridge. At the bridge, every other string goes to positive, and the rest to negative. You could make that plate work if you connected your E, D and B to it, then covered it with double sided tape with copper foil on top, and connected A, G and E to that, with the plate going to positive and the foil to negative (or vice-versa) but that's more work than you really need to do, and the connections are then outside the guitar, while with the brass pins they're inside and invisible.

[ashcat_lt]

Back on the String Return Pickup. I'm still having a little trouble visualizing this. I can't really see how the strings could be wired in series. What happens when you fret more than one string at a time, or - worse yet - bust out your big brass slide? Seems this would short across the strings, no?

To connect them in series, you have some foil at or behind the nut that connects the strings together electrically. It doesn't have to be foil-- just anything that makes an electrical connection between all the strings. Then you connect every other string to positive, and the remaining strings to negative. Each adjacent pair of strings makes a circuit-- E and A, D and G, B and E. When you use a metal slide, or press down at the frets, it does short the circuit, but all you lose is the part of the string you're not using musically, so it's not an issue.

Forgive me if I seem dense on this. The idea intrigues me, but I?m still having a little trouble with the series wiring thing. I?ll try to explain what I?m seeing, following from your description here and maybe you can show me where I?m going wrong.

For this example, let?s start at the bottom. We connect the low E string at the bridge end to the ? output. This connects (via nut, fret, or slide) to the A string which is connected on its bridge end to the + output. Now we connect the bridge end of the D to -. From what I?m seeing, the D string is connected (via nut, fret, or slide) to the A string. Seems this connects the + and ? of the output together. If there were a significant amount of resistance through the strings it might not be such a big deal, but since it?s pretty close to 0 Ohms, I?m seeing here a dead short and a silent guitar.

What am I missing?

[ubertar]

Forgive me if I seem dense on this. The idea intrigues me, but I?m still having a little trouble with the series wiring thing. I?ll try to explain what I?m seeing, following from your description here and maybe you can show me where I?m going wrong.

For this example, let?s start at the bottom. We connect the low E string at the bridge end to the ? output. This connects (via nut, fret, or slide) to the A string which is connected on its bridge end to the + output. Now we connect the bridge end of the D to -. From what I?m seeing, the D string is connected (via nut, fret, or slide) to the A string. Seems this connects the + and ? of the output together. If there were a significant amount of resistance through the strings it might not be such a big deal, but since it?s pretty close to 0 Ohms, I?m seeing here a dead short and a silent guitar.

What am I missing?

The A in your scenario is connected to the D the same way it's connected to E... at the nut, not the bridge. The signal has to go through two strings to complete the circuit, regardless of which path it takes. Trust me, it works... I've done it a number of times. The guitar I posted a pic of on the first page of this thread works that way.

The + and - of a regular pickup are also connected-- the same way you describe. The difference is that here, instead of a 13k or so coil, you've got about a one ohm pair of strings. It's low resistance, but it's not zero. It might seem counterintuitive, but it does work.

[ubertar]

Also-- think of it this way: the resistance of a 1 to 2" long, 2 micron thick strip of aluminum is significantly less than the resistance of a pair of guitar strings connected in series, yet ribbon mics still work.

[Nathangrn]

You can also put a pickup on the tremolo springs on a strat and make a sort of built in spring reverb. I blocked off the bridge, put in some lighter springs and mounted a buzzer piezo on a Squier strat iI have. It's way too microphone for live use but can be kind of cool for recording.

[ashcat_lt]

OK, I think I've finally got my head around this. Thanks for your patience. In case anybody else was stuck like I was, here's how I sorted it out:

I took the pickup analogy and got to thinking about something like an HHH Strat. This would be a total of 6 coils wired into 3 series pairs, with these pairs connected in parallel. If we use N for North Coil, S for South Coil, + for parallel and * for series, we've got (N*S)+(N*S)+(N*S).

Now we take the "series connections" - the two wires of each pair that connect together, which we would short to ground (or shunt to hot) in order to split the HB - and connect all 3 of these together. This does leave all 6 coils functioning just fine. It's a little tough to tell who's in series with who. I'd call it (N+N+N)*(S+S+S).

I'm still having a bit of trouble accepting the fact that there's enough resistance in a guitar string (or even two) to keep it from creating a dead short, but you've got one that works and I'll take your word for it. I am going to try this soon.


As for piezo buzzer type pickups: there's all kind of different places you can stick these things. I've heard that the neck pocket can be cool.