Buffer between effects

[manson]

Quote from the Pete Cornish site:

The inclusion of a custom designed and built tube pre-amp between one effect and the next ensured that each effect performed as if it were connected directly to the amplifier and completely eliminated the interaction and cross loading affects of multiple effects set-ups that are usually used without inter-effect isolation.

Is something like this DIY'able using small opamp buffers like the one at GGG? And does it make any sense at all?


http://www.generalguitargadgets.com/index.php?option=com_content&task=view&id=74&Itemid=26

[s.r.v.]

i dont think its necessary after each effect/ try them at the beginning and end, or one right before the amp or guitar. its cheap enough to build!

[Mark Hammer]

Think of buffers as providing an "introduction" and a "sendoff".  Under what circumstances would you need an appropriate introduction or an appriopriate sendoff?

• If the source of the signal tends to be on the high-ish impedance side.
• If the output device is designed around or alternatively is optimal when interacting with a particular type of input stage (think Rangemaster here).
• If the output signal is likely to face a lengthy hunk of cable to travel on the way to the next device.

Following this logic, if a pedal is the first thing in line and takes its input from a guitar with passive electronics, then it likely needs to have a buffer on the input.  Since the majority of pedals are designed to have a relatively low output impedance, anything after the first pedal will need necessary require a buffer on the input.  On the other hand, if preceding pedals are true bypass, then having, say, pedals A and B off, makes pedal C in the position of being the "first", so a buffer is needed in anticipation of that.  Additionally, since one never really knows where a given pedal might end up in a pedal-board or signal chain for user X, including a buffer is reasonable since it just might be the first one.

The Rangemaster would seem to be a special case since it seems to depend on facing a tube input stage from what I understand.  If you simply plug into one and then into your tube amp of choice, everything is simply ducky.  But what if you want a phased, or chorussed or echoed Rangemaster tone?  Sticking any one or more of those pedals after the Rangemaster essentially separates it from the love of its life.  Without Juliet, Romeo will surely die.  Hmmmm, we have a dilema here.  Pete Cornish suggests that a suitable tube stage between the Rangemaster and subsequent effects might be the solution, and perhaps he is right.  After all, the Rangemaster interacts only with the first tube stage of the amp's front end, and if we can replicate that we get to preserve the Rangemaster's "magic".

As for facing a length of cable, the ideal solution is something that can provide a high-current output, such as the paralleled op-amps buffer that Jack Orman has up on AMZ.  Though most pedals will provide a low-ish impedance output (and 1k is not uncommon) they do not all provide a high-current output.  So, a buffer that is comfortable with low output impedance sources, yet delivers a high-current output to take on the 50ft of cable between pedalboard and an amp or two situated somewhere in the backline, is a good idea, and entirely distinct from the buffer at the front-end of the signal path.

Do you need tube buffer stages between everything?  No.  Do you need all those input buffers in all your pedals?  Not necessarily.  If one had a master buffer after the guitar that was never bypassed, you could probably dispense with all those transistor input buffers in your Boss and similar pedals.  Of course, since you may well want to pluck ne of those pedals off the board and use it somewhere else, best not to tamper with the pedal and render the buffer unusable.  It may not be necessary now, but now isn't always.