Design for a buffer

J Fletcher · Post by **J Fletcher** » 19 Mar 2002 9:32 am

I'd like to build a buffer to go between my steel and my volume pedal. Something active to help bring out more highs, and reduce the loading on the pickup from the volume pedal, and cable. Maybe a variable input impedance and a high frequency cut or boost. Any ideas? Thanks...Jerry

gary darr · Post by **gary darr** » 19 Mar 2002 12:46 pm

I used to run a floor buffer but I would'nt recomend using it around your steel guitar[sorry I could'nt help myself]

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Sho-Bud proII custom,Session 500,American standard Strat,Shecter tele,Peavy Classic 50,Fender Vibrolux

ajm · Post by **ajm** » 19 Mar 2002 12:49 pm

Unless you really like tinkering with electronics, why don't you just buy one?

Almost any effect pedal with active switching will do just what you want (except for varying the input impedance). A Boss (among others) graphic EQ pedal will give you buffering and tone control at the same time.

J Fletcher · Post by **J Fletcher** » 19 Mar 2002 1:43 pm

I like building my own gear, that's why I'm looking for ideas. My Boss Delay pedal does have a buffered input, but the steel overloads it. I guess I could modify it, but I'd like a stand alone buffer. I'm looking for some ideas like a "Little Izzy", that was built 20 years ago, or so....Jerry

Keith Hilton · Post by **Keith Hilton** » 19 Mar 2002 7:03 pm

Jerry, here is some good books loaded with buffer designs:"Projects For Guitarists", by Craig Anderton, "Electronic Projects For Musicians", by Craig Anderton "The Stomp Box Cookbook", by Nicholas Boscorelli. Just about any bookstore in your area should be able to order these for you. Some of the things you said in your last post were interesting. You said, "My Boss Delay pedal does have a buffered input, but the steel overloads it." Don't know how a guitar pickup alone could overload a Boss Delay input? You do know a buffer 'boosts' signal strength. If you are already overloading your Boss Delay, why do you want a even stronger signal? That's what the "Little Izzy" did, make more voltage and current. You also said this concerning your Boss Delay pedal,"I guess I could modify it." Wouldn't try that, as it is loaded with SMT devices 'wave' soldered. If you don't know how to build a pre-amp, I wouldn't attempt to modify a complex digital device. Just my opinion.

Bill Crook · Post by **Bill Crook** » 20 Mar 2002 6:56 am

ditto to Keith's post !!

Steve Feldman · Post by **Steve Feldman** » 20 Mar 2002 7:05 am

Don't know how a guitar pickup alone could overload a Boss Delay input?

I don't want to beat a dead horse, but in light of your comment above, Keith, do you have any thoughts regarding a similar question I raised in another thread? - e.g., about why a Boss DD-3 gives a distorted signal when placed before the vol. pedal and no distortion (but also with noticable loss of highs) when placed after the VP. I just figured that the guitar PU was overloading the box.

All other factors being equal, all I was doing was relocationg the delay box. Thanks.[This message was edited by Steve Feldman on 20 March 2002 at 07:07 AM.]

Michael Brebes · Post by **Michael Brebes** » 20 Mar 2002 8:04 am

You can make a simple non-inverting buffer amp with an opamp. Using something like a TL071, NE5534, or some of the other low-noise, high slewrate opamps. I would recommend using higher voltage, if possible, since a lot of pedal steel pickups have pretty high outputs. + and - 15VDC will give you plenty. Variable input impedance is easy. Just take a 1 meg pot tied from the input to a 10K ohm resistor which is tied to ground. You now have variable input impedance from 10K to 1 meg. I wouldn't bother with adding any other kind of tone altering circuitry. Use a 50 ohm resistor from the output of the opamp to the connector and will protect the opamp against a short but still keep it very low impedance.

Keith Hilton · Post by **Keith Hilton** » 20 Mar 2002 5:45 pm

Steve, it was good getting to meet and talk with you at Scotty's Convention last year.
Every music show where Scotty is at he always asks me to get him hooked up. He always uses a DD3 delay with my pedal. I notice lots of posts on this form with guys using Boss DD3s.
Because so many people seem to be using this unit, I bought one. I didn't buy one to use, I use a Peavy ProFexII, but bought a DD3 to know about it. I havn't had time to actually hook up the DD3, that I bought about a year ago. I just did. Here is my opinion; I never heard such a noisy unit. My old analog stomp box delay sounds much better and doesn't have all the noise I hear in the DD3. If my pedal had that much noise I couldn't sell any. I really can't understand why I am getting all the noise, even with a old pot pedal. Scotty doesn't get noise when he uses his fry pan with the DD3. I do remember when I hook up Scotty, I always put the DD3 first, then run the out of it to my pedal, then out of my pedal to two amps. In my earlier post I was going from what I heard out of Scotty's guitar. Then again, Scotty's guitar is a lap steel, not a pedal steel guitar. Steve, from what I just heard, I will have to agree with you. I even tried the DD3 with a pot pedal and there was still loads of distortion and noise. I'm like you Steve, I wonder what is going on with this DD3? I have stock single coil Zum Pickups in my guitar.
Must be something we are overlooking Steve.
Michael, it would be best if the buffer was a chip design,not discrete transistor design, like you mentioned. The chips you mentioned are good sounding chips. I totally disagree about the protection. I can tell you all about protection from bitter down in the trenches experience. You have to have a capacitor on the input, and output, for DC voltage protection. You also need resistors on the input and output for protection. You also need boot strapped diodes on the input, and output, for protection. If you use a power supply instead of batteries, you need voltage regulation. Most wall warts don't have voltage regulation. Nowdays guys have several pieces of equipment in line to their amp, and everything has it's own power supply. When these different units power up and power down you get all kinds of surges, and different ground potentials. Unless you have the basic protection I mentioned, the transistor junctions of the chip will soon be
ruined. Take it from me and Hartley Peavey, guys who learned the hard way.

J Fletcher · Post by **J Fletcher** » 21 Mar 2002 6:18 am

Thanks for all the replies. Just for clarification, my Boss Delay pedal is an old analogue device, and when I mentioned that it overloads, that was in reference to a previous post that suggested that I use a stompbox as a buffer. I don't use the delay pedal normally, it sits on a shelf in my workroom. Has for about 15 years.
I have the Craig Anderton's, "Electronic Projectcs For Musicians" so I'll have a look at it tonight. Years ago I built his "spluffer" which is an active buffer/splitter.
I was hoping, actually, for something that was optimized for pedal steel guitar and used discreet transistors as opposed to IC's, but perhaps there's no advantage to this....Jerry

Keith Hilton · Post by **Keith Hilton** » 21 Mar 2002 8:26 am

Jerry, discreet transistor designs are really from back in the early 1960's. Why not use a modern, easy to use, integrated chip? One tiny chip can contain a hundred transistors already designed for you. I'm sure you are aware the book you have has designs for standard guitar electronics. Steel guitar is not that different. All you have to do is experiment with slightly different capacitor and resistor values to get the sound you want on steel guitar. The tragic thing about "all" these "how to" music electronic books is that none of them tell you how to protect the devices against failure. In addition to this all of the designs operate off of batteries. Building a regulated filtered power supply, with dual polarity, that won't destroy your electronis, that has no noise, is a tall order for the hobbist. By the way, just about all the designs require dual polarity-plus,minus and ground. Without protection any device you build is guaranteed a very short life. I will be happy to give you any advise I can on protection schemes.

Glenn Austin · Post by **Glenn Austin** » 21 Mar 2002 9:06 am

Jerry, you might want to check out the Jensen Transformer web site. They have schematics and designs for preamps using their great 990 class A op amp.

Michael Brebes · Post by **Michael Brebes** » 21 Mar 2002 4:00 pm

I'd stick with good quality standard opamps like those from TI, Burr Brown, Signetics. The main thing you want is low-noise and a slewrate of atleast 9 or 10. I wouldn't bother with the Jensen 990 opamps. They are made of discrete parts and cost you over $100 apiece. You can get a good quality opamp for your needs in the $1-2 range. You might want to consider buffering the output of your volume pedal as well. That's a 500K pot that can reek havoc with the impedance going down that cable to your amp.

Steve Feldman · Post by **Steve Feldman** » 22 Mar 2002 6:21 am

FWIW, Keith, I really like the DD-3. Mine's silent, but it was noisy when I used a 'generic' wall wart. Once I got hold of the Boss wall wart, it was great. I

Bill Crook · Post by **Bill Crook** » 22 Mar 2002 6:59 am

I too, use a DD-3 with a "Nashville 400", modified with John Lemay's mod. It is very quite, I am really suprised at all the flap about noise with these stomp-box devices.

I (after a number of trials) figured out that most of the noise is comming from volumne pedals that don't have a medal cover on the bottom !!

I also use (from time to time)a rack-mount "Profex II" system that has very little noise and hum in it. With just a little planning, one can get rid of most problems by just thinking about what he is attempting to accomplish.

Keith Hilton · Post by **Keith Hilton** » 22 Mar 2002 7:31 am

Steve, when I tried my DD3 it was powered with a battery. At the time, tried it with a Zum pot pedal to a Nashville 400, with nothing else connected. I'll try to see where the noise is coming from in the DD3, it may be as simple as a low 9 volt batttery.