Question about cables

m7b52000 · January 28, 2021, 05:56:33 AM

Confused about this! Does this make sense to any of you wise people? What are the symbols on the sleeve sleeve connection?

GibsonGM · January 28, 2021, 06:04:23 AM

Looks like they're hacking the capacitance between tip & sleeve to lower the input Z....ya, what is that little dude on sleeve/sleeve doing?
Is it just implying that the barrel over the sleeve is connected by virtue of attachment?

It's..basically a jumper from where I'm sitting. That is doing nothing. Weird, I'd ignore it, LOL.

Rob Strand · January 28, 2021, 06:18:43 AM

I read it as a mono (guitar) to stereo (stereo input) adapter cable.

amptramp · January 28, 2021, 07:22:46 AM

From the description above the diagram, it sounds like there is a following stage that has a 10 megohm input impedance and the ring terminal connects to a 1 megohm resistor to try and bring the impedance down. this means you swap out the cable with mono jacks on both ends for this cable to bring the impedance down. With the ordinary mono jack, you just connect to the 10 megohm input impedance, which maximizes the low end coming out of the pickup.

iainpunk · January 28, 2021, 08:34:06 AM

that's a cable used to not turn on properly pedals if the cable in put in to the input jack. since the battery/PS (-) side is getting connected to the guitar's signal, and DC current is sent through the pickups.... that's not a great idea, don't make such a cable!!

cheers, Iain

duck_arse · January 28, 2021, 09:48:43 AM

Quote from: m7b52000 on January 28, 2021, 05:56:33 AM
Confused about this! Does this make sense to any of you wise people? What are the symbols on the sleeve sleeve connection?

"strain relief clamp" - I think they've just drawn the mechanicals as well as the electricals.

Phoenix · January 28, 2021, 10:46:59 AM

The K&K Pure Mini (great pickup BTW) is a passive piezo pickup with much higher capacitance than typical piezo pickups, designed this way to achieve good bass response with an ordinary 1Meg input impedance, without the need for a specialized high input impedance piezo preamp.

This document is for the Grace BiX preamp, which is a specialized piezo preamp, that has a nominal 10Meg input impedance. They are aware that this will result in excessive bass response for K&K Pure Mini users, so they implemented a 1Meg shunt on the ring terminal of the input to their preamp to make it compatible with the Pure Mini.

This is a bit of a janky work-around, I think a dip switch/jumper would have been a much more elegant solution than requiring a custom cable.

Point is, this only applies if you're mating a K&K Pure Mini with a Grace BiX preamp.

Quote from: iainpunk on January 28, 2021, 08:34:06 AM
that's a cable used to not turn on properly pedals if the cable in put in to the input jack. since the battery/PS (-) side is getting connected to the guitar's signal, and DC current is sent through the pickups.... that's not a great idea, don't make such a cable!!

Nope, the Pure Mini is a passive piezo pickup, no battery or DC involved.

Rob Strand · January 28, 2021, 01:51:26 PM

QuoteThis document is for the Grace BiX preamp, which is a specialized piezo preamp, that has a nominal 10Meg input impedance. They are aware that this will result in excessive bass response for K&K Pure Mini users, so they implemented a 1Meg shunt on the ring terminal of the input to their preamp to make it compatible with the Pure Mini.

So that's what's going on. About two 3rd's the way down the page,

" I/O Impedance
Instrument Input 10MΩ / 1M Ω with TRS input cable, tip and ring shorted"

QuoteThis is a bit of a janky work-around, I think a dip switch/jumper would have been a much more elegant solution than requiring a custom cable.

A switch seems far more sensible than having a special cable. What if that cable dies.

m7b52000 · January 28, 2021, 01:59:24 PM

Quote from: Phoenix on January 28, 2021, 10:46:59 AM

Point is, this only applies if you're mating a K&K Pure Mini with a Grace BiX preamp.

A violinist friend has asked me to look into this. That is his setup I believe.

tonyharker · January 28, 2021, 03:28:18 PM

The symbols indicate the cable is shielded and it connects to the common wire connected to the plug sleeves.

antonis · January 28, 2021, 03:36:01 PM

Quote from: Rob Strand on January 28, 2021, 01:51:26 PM
A switch seems far more sensible than having a special cable. What if that cable dies.

The cable is dead.. Long live the switch..

anotherjim · January 30, 2021, 11:11:04 AM

The amp is probably hardwired for 10M for the most common application. If you have a switch, an unwise customer might reckon it sounds crap with their guitar although only because somebody left the switch the wrong way. A separate input jack for 1M might be a better choice?

I made some cables like that. They turn mixer insert jacks into direct outs without silencing the channel.

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Question about cables