Voltage follower, buffer circuit , active circuit

[cenizasblancas]

Hi, i want to build an active circuit for my strat for cancel the high capacitance of the chord of my guitar and i don´t know want circuit do i need, here is a circuit that i have what do you think?




Thanks

Juan Motta

[eschertron]

Hi Juan, good luck to you with your experimenting and building!

Let me give you my input:
1 - What makes you think that the capacitance of your cord is an issue? Is it very long (>>8m)? Is it poor grade? Could a different cord solve your problem?
2 - Be sure to think about space requirements when laying out the design. The space required on a circuit board for a few components, if this is not something you have had much experience with, plus the space required for the 9v battery may be an issue inside the control cavity of a strat. I have a store-bought preamp (the circuitry is built onto the volume pot) and the 9v battery alone is hard to squeeze into my strat.
3 - The circuit you have posted is quite rudimentary - it does not even specify which IC op amp to use - and variations or modifications to the circuit can mak a world of difference for you. Be sure to do as much research on different ideas and techniques as you can. For example, the buffer you have posted is unity gain. The volume control can reduce the signal amplitude, but cannot increase it past the volume currently available from the passive electronics. A little op amp theory and some basic math would allow you to design a modification that gives you a boost to your signal, if that's what you want. IMHE the 9v battery is just begging to give you 6 to 12dB of gain!
4 - Make a list of the things that you want this active buffer to accomplish for you. Some may not be achievable (due to space constraints inside the cavity, or whatnot), but you can do more than what the posted schematic would provide.

[bbsailor]

Hi, i want to build an active circuit for my strat for cancel the high capacitance of the chord of my guitar and i don´t know want circuit do i need, here is a circuit that i have what do you think?




Thanks

Juan Motta

Juan,

Look at this web link. http://www.till.com/articles/PreampCable/

When you place the buffer in the guitar cable plug you eliminate the cable capacitance and this will raise the resonance of your pickup and make it sound very bright.

Joseph Rogowski

[cenizasblancas]

Thanks for your answers, i´m going to read the till article!! my cable is 5m and is poor grade... first, i know this circuit is rudimentary but it was an excuse for learning electronics because my knowledge is basic. The cavity space is not a problem, if I have to enlarge, i´ll do it. The thinks that i want in the circuit: cancel capacitance of the cable (i thinks i´m going to do the fet preamp cable), 5 band eq and hum canceling for single coils pickups.... maybe is too complicated?

[Mark Hammer]

The easiest way to determine if cable capacitance IS a problem is to plug your guitar into your amp directly using your normal cable, and then using the shortest cable you have, such as a pacth cord for a pedalboar. Some of these can be very short, so you may have to put the amp on a chair or position it so you can plug in with a very short cable and still play.

The difference in tone between the short cable and the long one will be entirely due to cable capacitance. If you have bright but higher-impedance (>7k) pickups, with lower-value (250k or less) pots, the effect of the cable change will be more noticeable than if you have smoother-sounding lower-impedance pickups with higher-value pots.

It is easy to imagine some circumstances (specific pickups, amp, speakers, etc.) where there will be very little audible difference, or where the cable capacitance might even provide a benefit (Jimi Hendrix used a higher-capacitance cable that tamed much of the harshness from a Strat going into a Marshall). But in most cases, when you switch between the short and long, you will notice a loss of brightness.

As Joseph pointed out, any simple JFET preamp will do the job nicely. The advantage of the Tillman "amplified cable" is that it behaves like an onboard preamp, but you never have to take your guitar apart to change batteries.

In fairness, most low-gain single-JFET preamp/buffers draw so little current that you don't have to change batteries more than maybe once every 6-8 months. On the other hand, that may be more often than you want (getting into a Strat control cavity is a BIG nuisance), or the battery may not fit easily or snugly. So I can see many rationales for wanting to keep the power outside the guitar. Although note that if one uses a stereo jack in the guitar, the preamp can be internal, and the power supplied externally via the additional jack/wire conductor. A simple DPDT toggle would let you bypass the preamp, and the guitar would function as a traditional passive instrument should you have no power to supply the guitar.

I would strongly recommend not having more than 3-4x gain. There are a great many effects pedals that expect a certain signal level, and don't behave well if you feed them much more than that. For example, you may have a harder time getting acceptable functioning from anything that uses a sidechain (compressor, noise gate, autowah) or that lacks a compander to prevent sensitive parts clipping (delays, chorus, some kinds of phasers). A little bit of gain is fine for optimizing S/N, but too much causes problems.

[eschertron]

Thanks for your answers, i´m going to read the till article!! my cable is 5m and is poor grade... first, i know this circuit is rudimentary but it was an excuse for learning electronics because my knowledge is basic. The cavity space is not a problem, if I have to enlarge, i´ll do it. The thinks that i want in the circuit: cancel capacitance of the cable (i thinks i´m going to do the fet preamp cable), 5 band eq and hum canceling for single coils pickups.... maybe is too complicated?

The Tillman preamp cable is pretty sweet! It's cool that it solves the available space problem INSIDE the guitar, and that it can be plugged into any phantom-powered microphone input without the power supply box. It also is not part of the guitar so it can be used on ANY guitar, and not used (bypassed) when the situation requires.

5-band EQ is do-able, but will take more electronics knowledge and some more parts. Maybe there's a multi-band EQ on a chip project somewhere?

Hum canceling for single coils

...has been the holy grail among guitarists for over 50 years... but you know that, you've been on the pickup builder's forum!

[cenizasblancas]

Yes, you are right i´m going to build the till cable preamp,

band EQ is do-able, but will take more electronics knowledge and some more parts. Maybe there's a multi-band EQ on a chip project somewhere?

Maybe i can find some circuit

...has been the holy grail among guitarists for over 50 years... but you know that, you've been on the pickup builder's forum!

Ja, ja you are right,

Thanks

Juan

[cenizasblancas]

(Jimi Hendrix used a higher-capacitance cable that tamed much of the harshness from a Strat going into a Marshall). But in most cases, when you switch between the short and long, you will notice a loss of brightness.

I was thinking about this... and was wondering if I could use some passive circuit within the pickup, for treble or bass atenual as Fender Greasebucket circuit but independent and unable to adjust, what do you recommend?

Juan

[David Schwab]

I was thinking about this... and was wondering if I could use some passive circuit within the pickup, for treble or bass atenual as Fender Greasebucket circuit but independent and unable to adjust, what do you recommend?

Juan

The grease bucket is just a modified tone control that eliminates the resonant boost you get with the control on zero. To me that's the best part of a tone control. Every guitar I have heard with the grease bucket sounded bland when the control was turned down.

You can fine tune your pickups with small value caps, as shown in that scan from the book you posted. What book is that?

Here's another good buffer, the Alembic Stratoblaster, with a boost function if you want.

[cenizasblancas]

You can fine tune your pickups with small value caps, as shown in that scan from the book you posted. What book is that?

"building electric guitars" Martin Koch, a German luthier and thanks!!!

Juan