Input buffering question

[catalin gramada]

Hello. I was happy to try a signal buffer ( 1M in/ 100 ohm out) between bass guitar and amp. My goal was to preserve the guitar tone whilst I rolled off the volume from guitar pot. Well I found the solution involve at least two components : First aspect is related by frequency response - the tone is consistent with attenuation and high frequencies well preserved. The second aspect is related by "comportment" - the new impedance coupling modify the transients perhaps and the sound get more sustain in all range. I don't want to get more sustain, especially in bass and mid bass, the sound lost its initial character. My question regard how to preserve the frequency response whilst I use volume pot of guitar but to not modify the transients please ? Thanks.

[catalin gramada]

The buffer I used is a tc electronic. Did not found any schematic about it. Anyone please ? Thx
I checked with square wave the output of device and the signal is absolutely identical. So, why I get more sustain in sound using the buffer in respect with more "dry" sound on direct plug in, please ?

[bbsailor]

The buffer I used is a tc electronic. Did not found any schematic about it. Anyone please ? Thx
I checked with square wave the output of device and the signal is absolutely identical. So, why I get more sustain in sound using the buffer in respect with more "dry" sound on direct plug in, please ?

What cable length are you using between your bass and the Bonafide buffer?

To see more details about the buffer concept, visit this web site, till.com. Scroll down to see a buffer that he designed that will fit into the plug housing on the guitar end of the cable. This eliminates all the pickup seen capacitance of the coax. A common coax capacitance is between 25 pf to 30 pf per foot of coax.

With your Bonafide buffer with 1 meg ohm input you are placing a 1 meg ohm load in parallel with your bass volume control value. A 250K pot with a 1 meg ohm buffer input load places a 200K ohm load on the pickups. A 500K ohm pot will put a 333K ohm load on on the pickups. If you are using a 10 foot coax between your bass and your new Bonafide buffer, the pickups are still affected by the cable capacitance. However, if you used a Tillman buffer in the jack plug, your pickups would not see any cable capacitance.

When a buffer takes in a signal from a high impedance inductive source, like a pickup and produces an output at a much lower impedance in the 100 ohm to 1000 ohm range, the cable capacitance has a very limited effect on the sound quality change. This is why active pickups are used but a battery must be installed inside the instrument to power the buffer. The Tillman buffer provides the benefits of a buffer inside the guitar or bass but the power feeding it is external with no fear of the battery going dead while using it.

Try using a short coax between your bass and the Bonafide buffer and reevaluate your initial question.

I hope this helps.

Joseph J. Rogowski

[catalin gramada]

...Allright. I was focused more what is happen with the output line between buffer and input of the amp and using a random cable with 325 pF capacitive loss I didn't noticed any difference till I drived the input of the amp with a impedance ratio of 10x order of magnitude or less, making the input of the amp 10k or 1k which is a ridiculous low of course. A typical 1 M input don't have any effect in our frequency of interest
But it seems is more important what is happen with the pickup signal in respect with capacitive load it see which put me in situation to reevaluate my question, of course. Thanks.

[Jon Snell]

Why not do it properly.