Ultra Low Impedance Pickups

[tbryanh]

http://www.stewmac.com/shop/Bridges,...c_Saddles.html

The Stewmac string savers look like they will work good.

I am in the middle of planning a vacation, and I will be on vaction for a couple of weeks starting on 03/23, but I am going to pursue this when I get back.

I saw some ribbon mic transformers at
http://www.cinemag.biz/mic_output/mic_output.html
See the CM-9887 and CM-9888.

I couldn't find a price on them.

I will try with the small 8 ohm output transformers as you mentioned.

[bbsailor]

http://www.stewmac.com/shop/Bridges,...c_Saddles.html

The Stewmac string savers look like they will work good.

I am in the middle of planning a vacation, and I will be on vaction for a couple of weeks starting on 03/23, but I am going to pursue this when I get back.

I saw some ribbon mic transformers at
http://www.cinemag.biz/mic_output/mic_output.html
See the CM-9887 and CM-9888.

I couldn't find a price on them.

I will try with the small 8 ohm output transformers as you mentioned.

The impedance of the guitar strings vary from about 1.6 ohms (high E to about .6 ohms (low E) so plan on getting a transformer with a 4 ohm tap. This will match the strings better.

Joseph Rogowski

[tbryanh]

Why do you need a string ground ?
http://music-electronics-forum.com/s...ead.php?t=4887

It appears from this post that grounding the strings to the amp might be important.

I suppose the common on the primary of the ribbon mic transformers could be connected to the common of the secondary of the ribbon mic transformers and then the commons could be connected to th amplifier ground.?

It might be that the noize you were getting is partly because the stings are ungrounded.

Your noize reduction method was to alternate the phase in the primary from string to string.

This is an interesting method. Any idea how your method works?

[bbsailor]

Why do you need a string ground ?
http://music-electronics-forum.com/s...ead.php?t=4887

It appears from this post that grounding the strings to the amp might be important.

I suppose the common on the primary of the ribbon mic transformers could be connected to the common of the secondary of the ribbon mic transformers and then the commons could be connected to th amplifier ground.?

It might be that the noize you were getting is partly because the stings are ungrounded.

Your noize reduction method was to alternate the phase in the primary from string to string.

This is an interesting method. Any idea how your method works?

tbryanh

The noise on the string transducer guitar was typical of a single coil pickup. I could simulate it with a soldering gun to hear the 60 Hz noise generated by the soldering gun when brought near to the guitar. Then, I had a brainstorm. Why not make the strings like a humbucking pickup, so I alternated the phase of each other string and when I brought the soldering gun near the guitar, the 60 Hz hum was much less.

Grounding the case of the transformer also helps minimize noise.

Yes, the strings do pickup noise as it re-radiates that noise into any nearby pickup. I put a Lace Alumitone on one of my acoustic guitars in the sound hole just behind the end of the fingerboard. I got noise from the strings until I placed a piece of thick copper foil with a ground wire under the saddle inside the acoustic guitar with rubber cement. I poked holes through the pin holes to allow the string ball to contact the copper foil. The noise is now gone when I touch the strings.

Read up about ribbon microphones as each string functions as its own ribbon. The string has much more movement than the microphone ribbon has with just air causing the vibration. Using a transformer with about a 1:30 turns ratio, you should be able to get about 200mv P-P out of this setup and more if you use some strong neo magnets along the string length.

Make sure that the load on the transformer is at least 5 times the transformer output impedance. If it is the same impedance as the transformer, you will have a 6db or half signal loss.

Joseph Rogowski

[tbryanh]

Let me make sure I understand.

1. You replaced the non-metallic nut on the acoustic guitar with a brass nut to electrically connect one end of each of the 6 strings together to a common point. (Lets call this Point A.)

2. You connected one end of each of the primaries of the ribbon-mic transformers to Point A.

3. You connected the free-ends of the primaries to the free-ends of the guitar strings to form 6 single-turn non-humbucking ribbon-mic-type pickups.

4. You connected one end of each of the secondaries of the ribbon transformers together and grounded them to the mixer such that the transformers were in-phase with each other.

5. You did not ground Point A to the mixer.

6. You connected the free-ends of the secondaries of the transformers to the inputs of the mixer, each free-end to its own channel.

7. You noted noize in the ribbon pickups.

8. The noize content and level was not unusual; i.e. it was typical of any non-humbucking pickup.

9. You reversed the phases of the ribbon pickups on every other string.

10. You noted that the noize was reduced.

11. You added a Lace Alumitone pickup, a type of single coil pickup.

12. You noted that the noize in the ribbon pickups did not change after adding the Lace Alumitone pickup.

13. You noted that the Lace Alumitone pickup was noizy.

14. You grounded Point A to the mixer.

15. You noted that the noize in the Lace Alumitone pickup was reduced.

16. You noted that the noize in the ribbon pickups did not change; i.e. they had the same amount of noize regardless if Point A was grounded or not.

Is 1 through 16 correct?

[tbryanh]

How strong of a magnet is required?

Will a bar magnet found in the typical humbucking pickup work when placed in its typical location in the guitar?

This is a crucial question.

If an unusually strong magnet is required, the strings will be damped too much. This will shorten the sustain and affect the tone.

[tbryanh]

This is a crucial question.

This is a crucial question as far as electric guitars are concerned (which is what I am interested in). It may not be crucial as far as acoustic guitars are concerned.

[bbsailor]

Let me make sure I understand.

1. You replaced the non-metallic nut on the acoustic guitar with a brass nut to electrically connect one end of each of the 6 strings together to a common point. (Lets call this Point A.)

Yes, That is the common ground return. You need to try and use the truss rod as a ground return if you want individual control of each string by making an electrical connection between the brass nut and a washer with an extended finger to attch to the brass nut. Then, at the heel of the guitar you need to retrieve the other end of the connection to extend that common ground into the body of the guitar. I mentioned an acouistic guitar just to exeriment with different magnets and transformers to do quick experiments, not do the final installation. In fact, my first experimental guitar 30 years ago was an acoustic but I used an iron to heat and remove the fingerboard. I the placed a copper strip over the truss rod in a shallow groove on the back of the fingerboard and reglued it. I had the copper strip go under the brass nut and I soldered it behind the nut. The tail end of the copper strip came out in the guitar body near the heel block where I mounted the six individual transformers. The copper strip is connected to the strings so you only need to connect all the grounds of the transformer secondary together and to the common copper strip. Since all guitars have a truss rod, there is no need to remove the fingerboard to do this but find a creative way to use the metal truss rod as a ground returnconnecting at the top to the nut and at the heel of a removable neck for the extended ground return inside the guitar body for the transformer connection point.
2. You connected one end of each of the primaries of the ribbon-mic transformers to Point A.

One end to the common ground, point A, as you call it and the other end to the hot connection behind the bridge at the tailpiece on the copper rivet where the ball end of each string rests. One transformer is connected to each string. You could also use three transformers and go up one string and back to the string next to it, with the strings being in series. You need to short the machine heads together to make an electrical connection but you loose individual control of the strings. However, you do not need to fuss with the truss rod being the ground return either. Design alternatives!
3. You connected the free-ends of the primaries to the free-ends of the guitar strings to form 6 single-turn non-humbucking ribbon-mic-type pickups.

Yes. There is a however, however. Each string is non humbuckung, but by alternating the phase of the strings a sort of humucking effect can be obtained to minimize picking up external hum.
4. You connected one end of each of the secondaries of the ribbon transformers together and grounded them to the mixer such that the transformers were in-phase with each other.

I alternated the phase of each other string so that any noise picked up in one string was 180 degrees out of phase with the string next to it. Since the strings are totally independent and only play one note at a time, the phase of alternate strings is of no musical signal consequence but is a consequence to common noise signals from the outside.
5. You did not ground Point A to the mixer.

Point A is ultimately connected to the common ground. I used an 8-pin mic connector, using only 7 pins. I uses a common ground and the 6 hot signals, one from each string. If you have traditional pickups, you could use the 8th pin for that with the common ground.
6. You connected the free-ends of the secondaries of the transformers to the inputs of the mixer, each free-end to its own channel.

Yes. I made a breakout cable with all grounds tied together and six individual hots, one for each string. I went into a six channel mic mixer and could eq, adjust volume and L-R pan each string. For this you need a common ground return as in using the truss rod.
7. You noted noize in the ribbon pickups.

On my first attempt 30 years ago I noticed noise when I got close to my amp power transformer because the strings were long exposed antennas. That is when I experimented with the alternate phasing to minimize this problem. I simulated the power transformer hum field using a soldering gun to do my experiments and tests. What I told you about alternate string phasing is the result of those expiments and tests.
8. The noize content and level was not unusual; i.e. it was typical of any non-humbucking pickup.

If I stood in a particular direction about 8 to10 ft from the amp is was not too bad but needed to be fixed. When I got too clsoe to the amp, it was annoying.
9. You reversed the phases of the ribbon pickups on every other string.

Yes.
10. You noted that the noize was reduced.

Yes. I tested it before and after with my solering gun to simulate a 60 Hz noise source. I did this about 30 years ago when I first started playing with alternative pickups.

11. You added a Lace Alumitone pickup, a type of single coil pickup.

No. I only mentioned this because the strings on my new acoustic (not the one I modified 30 years ago) was picking up noise like mentioned in the posts in this forum. The Lace Alumnitone pickups are all humbucking, even the single coil size that fits a Strat. They use two primary loops of an aluminum shell and two magnets, one N and the other S. The magnets only go under 3 strings so as to give a single coil sound but the low Z loops are still in a reverse phase to outside noise.
12. You noted that the noize in the ribbon pickups did not change after adding the Lace Alumitone pickup.

13. You noted that the Lace Alumitone pickup was noizy.

Not unusually so. In fact, once the strings were grounded, it was quieter than my traditional humbuckers.
14. You grounded Point A to the mixer.


Yes

15. You noted that the noize in the Lace Alumitone pickup was reduced.

Not related to the ribbon transducer pickup.

16. You noted that the noize in the ribbon pickups did not change; i.e. they had the same amount of noize regardless if Point A was grounded or not.

Point A needs to be grounded!

Is 1 through 16 correct?[/QUOTE]

My answers are above.

Also go to this web link. http://www.record-producer.com/learn.cfm?a=3457

Joseph Rogowski

[bbsailor]

How strong of a magnet is required?

The fun part about playing with this using alligator clip leads to a tarnsformer and hand held magnets is that you can easily find out for yourself. Placing the string in a longer magnet field seems to increase the output as seen on the scope but it also changes the character of the sound. Moving the magnets nearer to the bridge emphasizes the higher harmonics.

Will a bar magnet found in the typical humbucking pickup work when placed in its typical location in the guitar?

Yes, both across the strings as well as in parallel with the strings.

This is a crucial question.

If an unusually strong magnet is required, the strings will be damped too much. This will shorten the sustain and affect the tone.

I even used used weaker ceramic magnets that I placed on a wood bar that fit on my acoustic, looking like an acoustic pickup but only had magnets on it. This worked.

Joseph Rogowski

[tbryanh]

You could also use three transformers and go up one string and back to the string next to it, with the strings being in series.

How about connecting all 6 strings in series and using one ribbon-mic transformer?

I think I would like to try it this way first.

If the strings were connected to each other in a zig-zag fashion, it seems there might still be a humbucking effect.

[tbryanh]

How about connecting all 6 strings in series and using one ribbon-mic transformer?

It seems that the frets might short the strings together and prevent the strings from being connected in series,

Connecting the strings in parallel is probably not possible because the strings would load each othe down too much?

[bbsailor]

How about connecting all 6 strings in series and using one ribbon-mic transformer?

This would work with only one transformer.You could use thin copper foil in the nut between adjacent strings to short them together between the E-B, G-D and A-E and shorting the B-G, and D-A at the bridge.
If you make a plexi bridge, you could build the transformer into the bridge and even put a stereo mini 1/8" jack to connect to an amp with minimal guitar mods for a balance output to feed a mic mixer rather than a guitar amp.

I think I would like to try it this way first.

Good plan!! You could quickly build a mock up and play with it this way.

If the strings were connected to each other in a zig-zag fashion, it seems there might still be a humbucking effect.

I don't think so, but give it a try.
This puts all the strings in series and you could use an 8 ohm 70 volt line matching transformer 1 or 2 watt is about a 1" cube. MCM part number 555-7117 for $2.52 VIP price in catalog #SC12.

Have fun.

Joseph Rogowski

[bbsailor]

It seems that the frets might short the strings together and prevent the strings from being connected in series,

Yes, there is some tradeoff for doing it the easy way with the strings in series. Tht is why I chose to do it with each string acting independly. Play with it first and see which way you want to go. All strings in series...easy or all strings in parallel...more control but more complex.
Connecting the strings in parallel is probably not possible because the strings would load each othe down too much?

Good observation. If one more string were loaded in parallel with a vibrating string, assuming that the strings have the same impedance which is not so since the B string is thicker than the E string, but a quick analysis indicates that you would have a minimum of a 6db or half the unloaded string signal.

Now, add additional strings in parallel and the losses get pretty high.

A web site www.electronicplus.com has a transformer 3.2 ohms to 500 ohms part# 45-709, 3/4" X 5/8" X 5/8", $6.75 each. The turns ratio is 12.5 so any voltage generated on the string will be 12.5 times higher out of the transformer. You could mix the outputs of each of these transformers either on-board the guitar or externally in a mixer.

Joseph Rogowski

[tbryanh]

It seems the strings cannot be connected in series because the frets will short them together. Is this correct?

It appears that if the strings were connected in parallel, the frets would not cause a problem. Is this correct?

Would the strings load each other down too much if they were connected in parallel?

[tbryanh]

I think I will try doing it the way you did it with 6 transformers.

Instead of connecting the strings in series, I will connect the secondaries of the transformers in series (as I think you already mentioned was possible) and send the signal to a guitar amp.