Another VP jr buffer question

[AntKnee]

Hey, everyone! I've been on hiatus from pedals for a while. I've actually been playing more and building less. Crazy!
Anyway...
I want to add a buffer to my VP jr, but for some reason, I can't understand where to put the buffer or how to split the buffered signal. I've seen where some have said to put a buffer before the pedal, but I don't understand how that would help if its sucking volume/tone at the output? Do I need to put it in line with the output after the signal splits for the output and tuner? Could someone please explain how to wire it in? (I'm trying to use a klon buffer, fwiw.)
Thanks!

[midwayfair]

It's not "sucking volume/tone at the output." Well, it's sucking volume if you're using it to attenuate the volume, but that's not what you mean. Nothing interesting happens at the output of most devices. It's all about the interaction of the source (driving device, starting with your pickups) and the next device in line. You have to look at input points.

There are two problems:

1) The impedance of the potentiometer in the VP loading the guitar pickups (which are a high-impedance source) and
2) The nature of loading and large resistances affecting high frequencies first.

The first is a problem with the value of the potentiometer in the VP Jr. primarily. Guitar pickups simply are too high of an impedance source to effectively drive a 25K load. You end up with losing total volume (with the pickup source and potentiometer load forming a voltage divider and losing signal) and a filter (because of cable capacitance) that attenuates high frequencies first.

This is less of a problem with the full-sized VP, which has a 250K pot. With a short and low-capacitance guitar cable, you might not find the 250K load objectionable. You still lose some signal and some highs, but it's possible that the bandwidth you lose is above the audio band.

The second is a problem with both types of passive volume pedals. Big resistances interact with capacitance elsewhere in the whole shebang and you end up losing high frequencies first (and your signal:noise ratio also gets marginally worse, but you're unlikely to notice given how noisy guitar stuff is). It's the same reason your volume knob on your guitar sounds muddy when you turn it down. This is why treble bypasses exist. It's worse if you don't have a buffer in front. The capacitance seen at the grid of a tube (or the next transistor or whatever in line) may be unhappy when the resistance gets really high, like when you're almost all the way heel down.

A buffer before the pedal will cure problem #1 because your pickups are no longer driving the pot. The buffer is a low-impedance source and can drive any value of pot (10K, 25K, 250K, whatever) happily and you can probably get away with a hundred feet of cable without having to worry unless the buffer isn't very good.

A buffer in front will also cure the part of #2 that you're likely to notice.

With a VP Jr., you should never have to worry about buffering the output. You're highly unlikely to have any guitar device that cares about seeing a max of 24.9K Ohms of series resistance, and at that point you're -30dB on raw signal anyway, so you can't hear it.

[sonnyboy27]

I've been writing a blog post about how the standard Ernie Ball mod works for a bit now. I've been holding off until now just to take some pictures and verify my math and understanding, but now seems as good a time as ever to post it and get some feedback about anything that might be wrong.

More importantly to you it has a step by step on how to do the standard mod that most people do. I like using the 1776 buffer board if you want to put the buffer inside the pedal since it's so small.

https://prentisseffects.blogspot.com/2017/01/ernie-ball-vp-jr-tone-suck-mod.html

Midwayfair: I would actually really appreciate any feedback you have on it as writing it has really been to help me personally understand what's going on. I believe I'm getting there in my understanding, but I think I'm missing some aspects of it. So anything you could add would be greatly appreciated. I may be mixing up power transfer optimization with voltage transfer.

[AntKnee]

Jon,
Thanks for your very explanatory and educational type of reply that we've all come to know and appreciate!

Stephen,
Thanks for the write up link!

Helpful info, guys. Much appreciated.

[cajone5]

Cool -- looking forward to photos in the tutorial on your blog site sonnyboy27