Tweet
I have a Joyo compressor pedal that works fine with my acoustic-electric guitars, but produces audible treble loss when I plug in my electric guitars. The acoustic-electric guitars have onboard preamps and low output impedance; the electric guitars don't. Evidently, the input impedance of the Joyo isn't high enough to avoid the dreaded "tone suck".
So I needed a buffer. I happened to have a few old MPF 102 JFETs sitting in the parts box. And I wanted to build the thing quickly, since I hoped to use it the next day, so I decided to try the simplest possible circuit (attached). Keep in mind, I was looking for a completely transparent, always-on, clean buffer - this isn't intended to produce any sort of overdrive or audible coloration to the sound.
The price one pays for this super-simple circuit is that the bias point will vary considerably from one JFET to another, and that will affect how big a signal you can feed in before the buffer clips. (Clipping might not sound good - the circuit has 100% negative voltage feedback, and usually, lots of negative feedback equates to harsher clipping.)
To see if this would be a problem, I bread-boarded the circuit; with a 10k source resistance and 9V DC power supply, all the MPF 102 JFETs I had settled down with the source somewhere between 1.41 and 1.72 volts. That means even the worst of these should be able to handle a guitar signal up to 2.8 volts peak-to-peak, which is comfortably big enough for most guitars and playing techniques.
I built my final version on a little scrap of proto-board, using the JFET with the largest Vgs (1.72 volts). I added a red power indicator LED and (820 ohm) series resistor, which I forgot to draw in the LTSpice schematic. I power my pedals with a One-Spot wall-wart, so I did not include any kind of on-off switch or bypass capability in my little buffer. No controls of any sort, in fact.
I thought about adding a footswitch and output level pot, so the pedal could double as a rhythm/lead level adjustment switch. But I'm using it in front of a compressor, which is the wrong place to try and change the signal level. So I decided not to bother with the pot or switch.
I tested it out last night, and I can't hear any audible treble loss from any of my guitars now. I can't get it to clip with any of my guitars plugged in and strummed hard, either. Eureka, it works!
I should stress that there is nothing magical or mojo-tistic about this circuit at all. Its designed from the perspective of a lazy audio engineer (though I am not in fact an engineer, I've played that role a few times). This circuit simply does its job, using a minimum of components, no fuss, no muss, no magic. If you need a simple, completely clean and transparent guitar buffer, this one might suit you.
-Gnobuddy
So I needed a buffer. I happened to have a few old MPF 102 JFETs sitting in the parts box. And I wanted to build the thing quickly, since I hoped to use it the next day, so I decided to try the simplest possible circuit (attached). Keep in mind, I was looking for a completely transparent, always-on, clean buffer - this isn't intended to produce any sort of overdrive or audible coloration to the sound.
The price one pays for this super-simple circuit is that the bias point will vary considerably from one JFET to another, and that will affect how big a signal you can feed in before the buffer clips. (Clipping might not sound good - the circuit has 100% negative voltage feedback, and usually, lots of negative feedback equates to harsher clipping.)
To see if this would be a problem, I bread-boarded the circuit; with a 10k source resistance and 9V DC power supply, all the MPF 102 JFETs I had settled down with the source somewhere between 1.41 and 1.72 volts. That means even the worst of these should be able to handle a guitar signal up to 2.8 volts peak-to-peak, which is comfortably big enough for most guitars and playing techniques.
I built my final version on a little scrap of proto-board, using the JFET with the largest Vgs (1.72 volts). I added a red power indicator LED and (820 ohm) series resistor, which I forgot to draw in the LTSpice schematic. I power my pedals with a One-Spot wall-wart, so I did not include any kind of on-off switch or bypass capability in my little buffer. No controls of any sort, in fact.
I thought about adding a footswitch and output level pot, so the pedal could double as a rhythm/lead level adjustment switch. But I'm using it in front of a compressor, which is the wrong place to try and change the signal level. So I decided not to bother with the pot or switch.
I tested it out last night, and I can't hear any audible treble loss from any of my guitars now. I can't get it to clip with any of my guitars plugged in and strummed hard, either. Eureka, it works!
I should stress that there is nothing magical or mojo-tistic about this circuit at all. Its designed from the perspective of a lazy audio engineer (though I am not in fact an engineer, I've played that role a few times). This circuit simply does its job, using a minimum of components, no fuss, no muss, no magic. If you need a simple, completely clean and transparent guitar buffer, this one might suit you.
-Gnobuddy
Attached Files
Comment