Author Topic: question about loop lengths  (Read 1175 times)

Bardkin

question about loop lengths
« on: March 12, 2021, 09:40:30 AM »
So I have an external loop with some effects. Problem is the loop length is too long.- my snake is 20 ft. This means that to use the external effects I have to walk over to my amp and switch the pedals on and off by hand.

What I'd like to do is to modify them so that the on/off switches are on the pedal board. Is that too long of a loop length for the pedal to power up? What is the best way to handle this?

Thanks!

BJM

Re: question about loop lengths
« Reply #1 on: March 12, 2021, 10:07:07 AM »
Hi,

I don't really understand the question but something like this?

http://www.geofex.com/article_folders/fxswitchr/fxswitchr.htm

Picture nr. 10, remote control for the effects loop switcher. I suppose you can keep the effects close to your amp and put the remote where you want it.

Bardkin

Re: question about loop lengths
« Reply #2 on: March 12, 2021, 11:00:13 AM »
no.
The issue is that I can not have my external effects loop 20 ft away from my amplifier. The sound is being swallowed by capacitance. (It is barely audible at all). Remember, this is an external fx loop- the audio signal would have to travel 20 ft to the pedals, then another 20 ft back to the amp. That length is too long.

By placing these pedals closer to the amp I get a crisp clear sound. But I am not at my amp when playing. I am 20 ft away and can not get my foot that far no matter how much I stretch. and it is not at all convenient to walk back and forth all the time.

Now, say I take the push button on / off switch out of the case. I extend the 2 wires 20 ft. (The audio signal doesn't travel those wires so it is not changed.)
I wire the on off switches to work on my pedal board, NOT the actual pedal all the way back at the amplifier.

Now the pedals can be at the amplifier, and I can turn them on and off at my pedal board, at 20 ft away.

The question is weather or not the actual on / off switch is too far away for the pedals to work properly.

garcho

Re: question about loop lengths
« Reply #3 on: March 12, 2021, 11:11:15 AM »
No offense, but I think you're coming at this all wrong. You need a buffer to drive your cables properly, and perhaps you need new cables. If "The sound is being swallowed by capacitance. It is barely audible at all", then something is seriously wrong with your rig. Yes, 40' of cable can attenuate high end frequencies, but "barely audible"? Perhaps you're exaggerating?
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Mark Hammer

Re: question about loop lengths
« Reply #4 on: March 12, 2021, 12:01:23 PM »
Jack Orman has thought deeply about this and provided an excellent solution:  http://www.muzique.com/lab/superbuff.htm

Keep in mind that cables behave more or less as lowpass filters.  There is a series resistance, and a capacitance between hot-lead and shield.  The capacitor in that configuration acts like a hall monitor, saying "Not so fast there, buddy!"  But, in the same way that being a foot taller and 50lbs heavier than the hall monitor will get you waved on through, pushing more current through the cable overcomes the cable capacitance and filtering effects thereof.

Jack parallels 4 op-amps to deliver more current to the buffer output.  Perfect for feeding long cables from the stage to the soundman at the back of the hall, or via 20ft cables to an amp behind you.

idy

Re: question about loop lengths
« Reply #5 on: March 12, 2021, 12:53:18 PM »
To address the original (clarified) question: no, there is no problem with 20 ft of cable  and remote switching. Relays or "boss style FET momentary switching" would be fine with a long distance "remote switching" system. You would add a "control" jack to the pedals in question and then run cable(s) to a box with momentary contact foot switches.

If the boxes in question are "boss style" switching then it really can be as easy as wiring a jack in parallel to the existing switch.

ElectricDruid

Re: question about loop lengths
« Reply #6 on: March 12, 2021, 01:09:53 PM »
Now, say I take the push button on / off switch out of the case. I extend the 2 wires 20 ft. (The audio signal doesn't travel those wires so it is not changed.)
I wire the on off switches to work on my pedal board, NOT the actual pedal all the way back at the amplifier.

Now the pedals can be at the amplifier, and I can turn them on and off at my pedal board, at 20 ft away.

The question is weather or not the actual on / off switch is too far away for the pedals to work properly.

This is a good solution. It's generally much better to ship control signals all over the place than audio. After all, they're mostly digital, so even if they got a bit degraded, you could run them through a Schmitt trigger at the far end and you'd have nice sharp on/off signals again. Not that I'm suggesting such a thing will be necessary, because I don't think it will.

That said, I agree with other posters that it sounds like the problems you're having currently are out of proportion to the cable length you're using. With a decent buffer to drive them and some decent cables, 20 feet isn't that far. Think about the front-of-house desk at an arena concert! Much further than 20 feet away from the stage! Nowadays, that's all digital of course, but it wasn't always.
« Last Edit: March 12, 2021, 06:13:36 PM by ElectricDruid »
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BJM

Re: question about loop lengths
« Reply #7 on: March 12, 2021, 01:42:44 PM »
no.
The issue is that I can not have my external effects loop 20 ft away from my amplifier.

OK, I understood the question but you're looking for another solution for the four-cable method :). Personally I wouldn't like to open up pedals to take out footswitches (if they're true bypass to begin with....) but that's because I'm not very good at this and would probably end up with some pedals no longer working...... So I would go for some remote switchin system as on the Geofex website. I suppose with a midi-cable you could wire op to five switches, which should be more than enough. Some time ago I put together a simple parallel looper, two loops with an extra pedal to ground the inputs. Only used at home with three meter cable but it  did work to turn the effects on/off remotely.

FiveseveN

Re: question about loop lengths
« Reply #8 on: March 12, 2021, 02:17:07 PM »
with a midi-cable you could wire op to five switches
While you're at it, why not use MIDI?

Like others have mentioned, 20 ft should not be an issue, even with the 4-cable method. If it is, something is either broken or all of your effects are true bypass and/or your amp's loop is unbuffered and you're getting the worst-case scenario. Even then, a buffer or two would be a simple and cheap solution.
Setting all that aside, there are many players who have found themselves in your situation. Nowadays you can find commercial units for all needs and budgets (e.g. from GigRig to RJM). Or you can make one yourself.

The question is weather or not the actual on / off switch is too far away for the pedals to work properly.
But with true bypass pedals the audio signal does have to travel to the switch and back. That's why people mentioned relays. By "the 2 wires" from the pushbutton, are we to understand that the effect(s) in question use BOSS-style bypass? In that case yes, you can probably just extend it a hundred feet with no issues. But how many effects are there? Are you removing 2 wires to add a dozen more? And if they have buffered bypass, why the signal loss in the first place?!
So please check your cables first. Then tell us the details of your situation (if you only need to switch one loop, use your amp's loop bypass if it has one). Then what you're willing and able to do (if you'd rather gut your pedals and put them in an integrated box or you're looking for something off-the-shelf).
Does the circuit sound better when oriented to magnetic north under a pyramid?

akmenpi

Re: question about loop lengths
« Reply #9 on: March 12, 2021, 04:41:42 PM »
It's barely audible because you're 20 ft away!

All jokes aside, I think you should do a little more investigating before tearing into your pedals.

What does it sound like without FX loop?
What does the FX loop sound like with a jumper from out to in?
What does it sound like with different cables?
Does a buffer help?


antonis

Re: question about loop lengths
« Reply #10 on: March 12, 2021, 05:09:29 PM »
The issue is that I can not have my external effects loop 20 ft away from my amplifier. The sound is being swallowed by capacitance.

That leads to outrageously high cable dielectric constant value..

"I'm getting older while being taught all the time" Solon the Athenian..
"I don't mind  being taught all the time but I do mind a lot getting old" Antonis the Thessalonian..

ElectricDruid

Re: question about loop lengths
« Reply #11 on: March 12, 2021, 06:38:05 PM »
TLDR: The cable itself can't possibly be that bad. :icon_biggrin:

iainpunk

Re: question about loop lengths
« Reply #12 on: March 12, 2021, 06:51:11 PM »
TLDR: The cable itself can't possibly be that bad. :icon_biggrin:
yes it can be, if there are fractures in the strands of wire inside, the resistance increases, and the filtering would be worse.
half man - half snail - 6 feet to scale - Snail man's - not frail - He's been - to jail - snail man is fuccing real
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Rob Strand

Re: question about loop lengths
« Reply #13 on: March 13, 2021, 03:24:22 AM »
No offense, but I think you're coming at this all wrong. You need a buffer to drive your cables properly, and perhaps you need new cables. If "The sound is being swallowed by capacitance. It is barely audible at all", then something is seriously wrong with your rig. Yes, 40' of cable can attenuate high end frequencies, but "barely audible"? Perhaps you're exaggerating?

Agreed.    Threre's a problem and it's not being fixed.  It's being stepped around with a lot of fancy boots.

What's the amp?   Find a schematic and checkout the effect loop circuit.

If it's a tube amp and the effects loop is being fed off the plate with a 100k resistor that's just asking for it.  The effect out needs a buffer.

If you have 100pF/m (30pF/ft)  cable and the entire run is 40'  then that's 40'*30pF/ft = 1.2nF.  A 100k plate resistor is 38k output impedance (https://www.aikenamps.com/index.php/designing-common-cathode-triode-amplifiers).   The HF cut-off is 1/(2*pi*38k*1.2n) = 3.5kHz  which is noticeable.   If the cable has a lot of capacitance then you could find that's a lot worse.
The internet:  answers without the need for understanding.

anotherjim

Re: question about loop lengths
« Reply #14 on: March 13, 2021, 04:41:00 AM »
Some amp FX returns are not high Z instrument inputs at 1M, they may be medium Z like 100k. The FX send may not be a low source impedance either. The send could be tapped off a class A amp stage which could be quite high impedance and definitely will be dulled by the capacitance of a long cable.

Really need to know the amp model.

Some FX cannot drive low Z inputs - you need a buffer or a buffered bypass pedal such as a Boss driving the cable back to the amp.
At the amp, I would suggest another buffer at the FX send if it turns out that the amp output doesn't have a buffer/driver to that jack.

For testing purposes, any buffered pedal can be used to act as the buffer with its effect bypassed.

If the 20' cables work ok for normal guitar to amp playing and don't crackle when handled, they are probably good.
Croeso i Diystompboxes.

If they didn't hear you then you didn't say it.

Bardkin

Re: question about loop lengths
« Reply #15 on: March 14, 2021, 01:01:45 PM »
Thanks for all the input, I appreciate it. So to answer a couple questions-

Amp- Is an old digitech GSP2101 (circa mid '90s. It has a send and two returns (L&R)  I do have the schems and am looking at them now.

When the pedals are hooked up close to the rig, they work just fine.  When they are on the pedal board I can hardly hear them at all.

The pedals are boss style with true bypass. Two delay/reverb and a stereo analog chorus.

I had asked some people about using a buffer but wasn't all that enthusiastic about the answers I was getting. They are kind of expensive just to test with an that's why I thought about moving the switches in the first place.

Replies:
As for sound man /concert hall settings- Your foot pedals really shouldn't have any connection what so ever with the mixer itself. You want to mike amplifiers, even if you can line out to the board. But either way your pedal board goes to your amp, not the mixing board.  Big name acts have the loops at the amplifiers and there is usually a tech that will switch them for you. Alas, I haven't ever been big enough to have a guitar tech that could do that for me.

My cables are fine, I have tried other cables with the same results and have tested line voltage and resistance on them, so it isn't the cables.

My thoughts have been geared more towards possibly removing the guts of the pedals, and getting them all inside an old rack mount line mixer with line in and 2 outs for the stereo output. Ive always hated having to stoop down to change rates and times. be nice to have them at eye level on a rack mount unit.

(And before anyone starts going off about that please note that I have 2 15 watt tube power amps that I built myself to provide a left and right output. (6v6 setup from the old 1960's Gibson GA 30 stereo amp. Plenty of sound for practice and can be miked for any size stage. The digitech is my pre-amp, and I can model just about any type of amp sound as I have control over both tubes and there is a 7 band EQ in the analog section of the pre-amp.


Anyhow, Thanks again for all the help



FiveseveN

Re: question about loop lengths
« Reply #16 on: March 14, 2021, 03:38:21 PM »
The pedals are boss style with true bypass.

No. "BOSS-style" means buffered bypass with JFET switching, that is not true bypass.
Why is the identity of these pedals such a secret?  :icon_biggrin:

Quote
[buffers] are kind of expensive just to test with
For commercial units sky's the limit, but for DIY they're some of the simplest and cheapest things you can make: http://www.muzique.com/lab/buffers.htm
Does the circuit sound better when oriented to magnetic north under a pyramid?

PRR

Re: question about loop lengths
« Reply #17 on: March 14, 2021, 04:55:13 PM »
The Return(s) from pedalboard to Digitech: what pedals drive it/them?
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Phend

Re: question about loop lengths
« Reply #18 on: March 14, 2021, 05:44:06 PM »
Not knowing,  how about wireless.
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Ya sure you Betcha.

Phend

Re: question about loop lengths
« Reply #19 on: March 14, 2021, 05:48:15 PM »
Know nothing about these, do they work  ?

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Ya sure you Betcha.