Hexaphonic Pickup Project

[cycfi]

Thanks!

Sure, but I hope I have not mislead you into thinking this is for inside the guitar; my intent is to keep the guitar completely passive (25K or lower vol. pot.); this circuit is not low current.

Oh I see. But then why not just use something like the LME49990 with 0.9 nV/√Hz ?

The link: http://arxiv.org/pdf/0811.2866.pdf

I realize now that this is from the Cornell library. It appears to be public access, but if you have trouble, I can send you a copy.

I got that. I just realized I've seen this before, but didn't quite pay attention. I'll study this some more
for possible future use. Thanks for the links and info! Much appreciated.

The circuit is briefly discussed here as well: http://www.gellerlabs.com/JCan 20References.htm. Apparently there is a very similar circuit, which I have not yet seen, that uses ac rather than dc coupling of the FET to the op amp inverting input. There is a statement that the dc coupling is used to stabilize the drain current. It appears to me that only the drain source voltage is stabilized. By the way, this is accomplished with a battery (from which essentially no current is drawn). A reference is provided showing that batteries are very quiet. Also this analysis questions where the operating point is set. I think it is very clear that the battery voltage puts the drain source voltage on the flat part of the curves, and the FET goes to IDSS (VGS = 0). This is a reasonable way to operate for very small signals, usually why one needs a very low noise amplifier. However, for guitars, even medium impedance pickups, the signal is not that small, but the high gain is needed for non-linearity in the guitar amp. The FET preamp therefore probably should be operated with better linearity or you will lose the possibility of a clean signal. Looking at typical curves (Field Effect Transistors), one would choose a current of about 80% of IDSS. (I have not tried this yet, but soon, since I have received FETs from Linear Systems.) A source resistor bypassed by a tantulum capacitor could be used to achieve this. Tantalum Cs are noisy at sub audio, but the noise falls off very fast with increasing frequency, and there should be no problem at guitar frequencies.
(downloads.hindawi.com/journals/apec/1987/010769.pdf
TANTALUM CAPACITORS. D.T. SMITH. University of Oxford, Clarendon Laboratory, Parks Road, Oxford OX1 3PU. Noise has been measured in a number of ...)

[cycfi]

Outside of the casual nerdy interest I had with this topic originally, you now have my full attention from a musician's standpoint. Keep up the good work. I look forward to any further progress and hopefully building these once the design is finalized.

Thank you! Kind words make this project a lot more invigorating and motivating :-)

[Mike Sulzer]

Oh I see. But then why not just use something like the LME49990 with 0.9 nV/√Hz ?

Current noise. The LME49990 is a marvelous device, but it has 2.8 pA/rtHz of current noise. Multiply that by just 1000 ohms and get 2.8 nanoV/rtHz. A FET with 1 nanoV/rtHz voltage noise is a marvelous thing because the current noise is so low, and so it is very usefu with an inductive source such as a pickup or a varying source such as a volume control. Almost as good as a really good vacuum triode (not a 12AX7), except you cannot see inside.

[Rick Turner]

Mike, the Alembic pickups that I designed in the early 1970s were really medium impedance units with a resonance above 20K but not by much. We were going for a balance between pickup output and getting the resonance out of the audio band. Then there was onboard buffering, some gain (user adjustable), the active humcanceling circuit, and then the switchable Q low pass filters.

I'm currently using high impedance pickups, but they're buffered after about 8" of cable. Why? Simply because it works, and my customers like how they sound. It's certainly not the only way to go, but on these current models of guitars, I'm pretty much sticking with what my customers expect at this point. I am trying to make a living at this!

[Mike Sulzer]

Absolutely, the guy who who pays has to get what he wants. But I bet you could get very, very close to the same sound with medium impedance by using a C across the pickup and Rs across and maybe in series. Then the cable length would be less critical, and the buffering could provide the gain to make up for the missing signal level. Just another way to go.

I'm currently using high impedance pickups, but they're buffered after about 8" of cable. Why? Simply because it works, and my customers like how they sound. It's certainly not the only way to go, but on these current models of guitars, I'm pretty much sticking with what my customers expect at this point. I am trying to make a living at this!

[Rick Turner]

Mike, fully understood, but I've got consistent (that word and concept keeps coming up!) winds count, consistent DCR thanks to pretty consistent tensioning, consistent cable length from pickup to first buffer stage, and it all works. I'm not changing it for that model of pickup and guitar. I only wish the wood were as consistent as the pickups!

[Mike Sulzer]

I only wish the wood were as consistent as the pickups!

Maybe the scientist who grew beef in his lab (without the steer) and ate the resulting hamburger will learn to grow wood without the trees. Lacking that, most woods will be very scarce in a few decades, and consistent wood a mere dream. Maybe one could simply grow the whole solid body guitar, eliminating most of the wood work and giving new meaning to the term "neck through".

[David Schwab]

Maybe one could simply grow the whole solid body guitar, eliminating most of the wood work and giving new meaning to the term "neck through".

Or you do something like this:

[big_teee]

Or you do something like this:

I had one of those come through here about a year ago.
It was routed PJ, was a slick little bass that a lady in a local band played.
T

[Steve Conner]

I think this is the first time on MEF that a Steinberger headless has appeared in the same post as a .

For the record, I love cycfi's carbon fibre guitar. I just don't like the shape of the Steinbergers.

[David Schwab]

I had one of those come through here about a year ago.
It was routed PJ, was a slick little bass that a lady in a local band played.
T

Was it a wooden body? This one is all composite materials.

Can't imagine how they would have routed it for a P/J. But there are a lot of similar instruments on the market.

I always wanted one of these basses.

[David Schwab]

I just don't like the shape of the Steinbergers.

I think it was quite daring at the time. I still like them.

I almost bought an M-series guitar when they first came out. I wish I did now. Those were the ones with the Strat looking body.

[cycfi]

Maybe the scientist who grew beef in his lab (without the steer) and ate the resulting hamburger will learn to grow wood without the trees. Lacking that, most woods will be very scarce in a few decades, and consistent wood a mere dream. Maybe one could simply grow the whole solid body guitar, eliminating most of the wood work and giving new meaning to the term "neck through".

That's the main reason why I designed and built Cycfi Alpha, Carbon-Fiber-Bamboo Guitar:

[cycfi]

I think this is the first time on MEF that a Steinberger headless has appeared in the same post as a .

For the record, I love cycfi's carbon fibre guitar. I just don't like the shape of the Steinbergers.

Oh, thank you, Steve! It's carbon fibre-bamboo, BTW. The middle part is thru-neck Bamboo reinforced by an adjustable CF truss rod.

[Rick Turner]

Historical note: Ned Steinberger licensed the carbon fiber neck patent from Modulus Graphite. I was the inventor of record on that...I assigned production rights to Modulus, and I eventually sold my share of the patent ownership to Music Man in 1989.