Pete Cornish doesn't like true bypass: http://petecornish.co.uk/case_against_true_bypass.html
So inside all of his pedals he includes a buffer to aid the switching process and act as a line driver for the remainder of the pedal chain. He sells these individually as the LD-1 (and LD-3 with the mute switch and tuner output).
Here's a description from the Cornish Website:
"Our low noise discrete component Class A pre-amplifier has been specifically designed to overcome the problems often encountered with amplification of Electric Instruments fitted with magnetic transducers.
A frequent cause of these problems is the mismatch of the impedance in the electrical circuit between the pickup and subsequent equipment: this mismatch has been completely eliminated with the introduction of our LD-1™ Line Driver.
The input impedance is identical to a high quality tube amplifier and our Class A Pre-amplifier also features a highly effective RF filter which will help prevent interference from nearby radio transmitters.
The pickup output should be connected directly to the LD-1™ input with a low loss, screened cable; the LD-1™ output can now be fed to any effects or volume pedals (if used) and then on to the amplifier, using fully screened cables throughout.
A further use of the LD-1™ is to isolate long cable feeds which can cause signal and tone losses at the end of an effects chain, particularly if the final effect has a high impedance output (for instance a 250KW foot volume pedal). When using many effects it can be beneficial to add a LD-1™ mid way along the chain thus preventing a build up of signal losses that can occur with mismatched impedances between effects."
Well, someone's taken a few Pete Cornish pedals apart and here's the schematic for the buffer:
And here's a vero layout from IvIark (http://tagboardeffects.blogspot.com):



Hey, could I use bc550 transistor instead of bc549 for this buffer? I've check the data sheet and it looked like the only differences between these two transistors is That bc549 max volt for E and B is 30v, while bc550's E is 50V and B 45V. Would that make any difference for the buffer?
ReplyDeleteIt wouldn't make that much difference, any silicon npn transistor with decent HFE should work..
ReplyDeleteThanks! So what's a good range for decent HFE?
DeleteWell the BC549 and 550 will have hfe's around 500ish...
DeleteCool thanks. I've also noticed that all your replies to comment ends with multiple dots...
Deletelol haha but yeah, thanks for replying. Love this site!
HEhhh, I'm a dot addict! Glad you like the site :-) ...
DeleteWow! You will not BELIEVE how much the LD-1 goes for - $399!
ReplyDeletehttp://www.massstreetmusic.com/store/show_item/2364
For a single transistor emitter follower circuit! Holy cow!
Hi Fred, very cool buffer layout! Just a question: do you use a 3pdt switch wiring? If not, what's correct wiring to use?
ReplyDeleteThanks!
Works pretty well! It adds a bit of top end back to my bass.
ReplyDelete