Input buffer/Output splitter

[Buffalo Tom]

Hello. Can I do like this to split the signal after the Cornish buffer? Output 2 is going to a VU meter circuit.

[iainpunk]

if you use op amp buffers like that, you could just as well leave out the Cornish buffer and just split the signal passively before the op amps and then use those op amp buffers as the main buffers

[Buffalo Tom]

if you use op amp buffers like that, you could just as well leave out the Cornish buffer and just split the signal passively before the op amps and then use those op amp buffers as the main buffers

Yes but I really like the sound of the Cornish buffer with the BC549 transistor. So I want that to be the main buffer for the guitar as this is the first pedal input stage. But I need to split the output... And looking for a good way to do it. 

[antonis]

I really like the sound of the Cornish buffer with the BC549 transistor. So I want that to be the main buffer for the guitar as this is the first pedal input stage. But I need to split the output...

If you want to split the output just after the buffer, via any spitter configuration, you'll loose the sound you like.. 

IMHO, it should be better to have 2 identical Cornish buffers with signal splited on input..

[intripped]

please excuse me for the intrusion,
i have a question:
what if you just split the signal at the output of the Cornish buffer?

[Ben N]

Where in your signal chain do you figure to use this buffer/splitter?

[PRR]

You don't really have a 1939 VU meter.

It actually would be fine on the buffer's 200 Ohm output impedance (was designed to bridge a 300r terminated line), but only the loudest guitar peaks would rise half-scale.

When folks today say "VU" they usually mean some contraption with electronics in it. Show us YOUR part.

[PRR]

If you are happy now, you do not want to add stuff to your Precious Signal.

You do want additional buffering to "nasty loads" like meters, tuners, PA systems.

Any audio-suitable OpAmp can drive any reasonable number of typical loads. A padless VU is 3k, electronic VU "should" be higher. Most loads are over 10k. A good opamp can drive 1k (at guitar level) so even a true-VU and three others is well within limit. The secondary concern about driving multiple loads on one output is: cables SHORT! If you add isolation resistors (always good when driving cables) you can plan so a short on one will not leave the others dead. I've been a little brave assuming 150r isolation resistors: one short may demand 10mA from the opamp but they mostly are good for >20mA. So tuner shorts, you still have feed to meter and PA.

I've also simplified the DC biasing.

[tubegeek]

Hidden pitfall with LED level meters: "zipper" noise coming into audio via power supply as the lights snap on and off. Need additional filtering and thoughtful +V and ground routing to the LED device. At least according to Self and when is he ever wrong?

[Buffalo Tom]

If you are happy now, you do not want to add stuff to your Precious Signal.

You do want additional buffering to "nasty loads" like meters, tuners, PA systems.

Any audio-suitable OpAmp can drive any reasonable number of typical loads. A padless VU is 3k, electronic VU "should" be higher. Most loads are over 10k. A good opamp can drive 1k (at guitar level) so even a true-VU and three others is well within limit. The secondary concern about driving multiple loads on one output is: cables SHORT! If you add isolation resistors (always good when driving cables) you can plan so a short on one will not leave the others dead. I've been a little brave assuming 150r isolation resistors: one short may demand 10mA from the opamp but they mostly are good for >20mA. So tuner shorts, you still have feed to meter and PA.

I've also simplified the DC biasing.

Thanks!! 

[Buffalo Tom]

I open up my LD-3 that has a tuner output. Here is what I found. Looks like a simple Y split on the output with just an extra resistor on the tuner jack (R11). There is also a resistor across the mute/play switch. Whats the function for R12? Anti pop? The board is covered in black paint so I don't know anything about those R values.. But there is 9 resistors on the board and that matches with the available LD-1 schematics online...

[Ben N]

$300, eh? Dang!