Little Labs STD (Guitar Buffer) replacement

[DaxLiniere]

Heya guys, the new forum layout looks nice!

Little Labs has a product which is essential a guitar buffer, designed for "long" distance cabling between guitar and amplifier:
http://www.littlelabs.com/std.html

The included purple lead houses part of the circuitry inside the jack plug.

As stated on the website, it's a single-transistor device, so surely we can DIY this for less than us$150! Even with Elna & Dale products.

If I were electronically smart enough, I could probably work out what to do with these pages, (But I'm not  :-[ )
http://web.telia.com/~u31617586/#simple%20FET%20impedans%20converter
http://www.muzique.com/lab/buffers.htm

What are some high quality JFETs that would be suitable for this role?

Thankyou all for your time & expertise.

All the best,
Dax.

 

[DaxLiniere]

Okay, so further research provides these:

http://www.till.com/articles/PreampCable/index.html
http://www.uwm.edu/People/msw/ActivePlug/BootStrap.html

I don't like the idea of the second link, because the first thing in the circuit is a capacitor. Don Tillman's design seems simpler and to me that means probably cleaner and more truthful to the original tone of the guitar.

He does mention a list of future improvements:
1) lower noise FET
2) 2x9V battery instead of just one (for increased headroom)
3) Use of a FET differential amp to reduce hum and noise and also be more compatible with the AES XLR spec.


How would we achieve those goals? (I re-iterate that I'm not electronically smart enough to solve this myself)

 

[DaxLiniere]

Bump?

 

[PRR]

> I don't like the idea ... because the first thing in the circuit is a capacitor.

So? There are capacitors EVERYWHERE in an audio chain.

And FWIW, you can leave this one out.

> more truthful to the original tone of the guitar.

Who knows what the "original tone" is? Electric guitars MUST be amplified, and the true instrument is the combination of axe and amp, just like a violin is a string and a box.

> 1) lower noise FET
> 2) 2x9V battery instead of just one (for increased headroom)
> 3) Use of a FET differential amp to reduce hum and noise

Why, why, why?

Guitar tone is almost never noise-limited. Guitar output can easily fit under a 9V rail. Two-FETs have nigher hiss, and if battery-powered, what hum?

http://www.till.com/articles/PreampCable/ is a fine plan. Just do it.

 

[zebra50]

http://www.muzique.com/lab/buffers.htm

Haven't tried the others but the buffers on the musique.com site work just fine. I've used the 4th circuit down for several applications - works just fine with unselected J201 jfet.

 

[Gus]

Google Aron's stompbox and freestompboxes

Also read up on loading of a pickups and the tone change.  Guitars and basses are a mess pickup inductance, pickup resistance, series or parallel switching/mixing of pickups tone controls......

When you use a high input resistance circuit like a fet one with a >1meg input the tone can change,  the sound can become brighter.  Have you ever used a 1meg volume control vs a 250K in a tele. and noted the sound change?

At Aron's stompbox forum the beginner project is a circuit of mine that was built as a a what can I do with one transistor that is a bit different than what is out there.  The input resistance is controlled by the hfe of the transistor and the position of the gain control (bootstrapped) min gain about X2
http://www.diystompboxes.com/smfforum/index.php?PHPSESSID=a2d03c2d7e29f4ab6cb86ee0d48fbfb7&board=6.0

Simple fast build can use a lot of different number transistors.

Also the added cable capacitance of a long cable "can be your friend"

EDIT I read the first site, single transistor could be as simple and easy as a MPSA18 emitter follower.  Lets make a guess a 10K emitter R, Lets guess a 47K and 68K resistors as voltage divider(offset for a reason) a cap from the center node to ground a 1meg resistor to the base and the other side to the divider node(I guessed 1meg because it is a common tube amp input resistance) a .1uf cap to the tip and to the base the output cap can be in the box.  Why two 9VDC battery s with a unity gain stage like PRR posted?
Did they add a cap from tip to ground to sim the cable cap?

That posted.  I think unless you are going down a long cable(what is a long cable?), buffers are not needed and if you are going that long a distance why not a wireless?

It has a ground lift and not a transformer for one of the outputs?