Guitar to amp wiring

Guest · Post by **Guest** » Fri Aug 13, 2004 3:28 am

I have been wondering for some time now how to connect my electric guitar to my . Simple instrument cable ? Yes, but... with the guitar either in the live or control rooms and the amp in an iso booth, that won't do it. And running an instrument cable down to a socket in the room, then through a fixed cable through the walls to another socket in the booth, and down a small cable to the amp -it seems to me too long not to loose a lot ot the guitar's personality.

Any advice on this ?

Thank you!

Gwen

Post by **Aaronw** » Fri Aug 13, 2004 4:12 am

I've seen this done a couple of ways.

Let me ask this...is the amp head near the cabinet, or can the amp be located near the gtr player?

Often times the player wants the head near them to adjust any tone controls, etc.

Here's one idea...if this is the case as above, you can use the large monster cable to run from room to room w/ a 1/4" female jack T/S (Tip/Sleeve) connected on both ends (CR/LR & iso room).

From the Iso room jack, plug in another cable (also monster cable) from the 1/4" plug on the wall to the cabinet.

The head where the CR/LR plugs the output of the amp to the plug on the wall (which goes to the iso room).

The gtr player plugs in and starts jammin'

Now, unless you're parked under a broadcast tower, you shouldn't have any issue's w/ RF. A studio I worked at in Seattle was at the bottom of a hill w/ broadcast towers, and at 4pm every day, we got to listen to Dr Laura come through the cabinet...

Aaron

Guest · Post by **Guest** » Fri Aug 13, 2004 6:35 am

Thank you ! I understand that you are using Monster Cables to minimize the loss.

However, I should have stated that my problem is mainly for small combo amps - like this small Fender Pro Junior or my old Fender Vibrochamp. Of course I could be using one another's speakers (as a cabinet) in the booth while the other amp (being actually used as an amp) remains in the CR. But I would feel like Dr. Frankenstein...

My question is more like : how to run longer lengths of guitar-to-amp signal without too much loss (around 15m which is like guitar to patch bay to CR wall to ISO wall to ISO socket to amp) ? Is it enough to use higher grade cable or should the signal be symmetrical on part of the trip ?

emtee · Post by **emtee** » Fri Aug 13, 2004 6:51 am

Try using a Boss (or similar) pedal in bypass mode.

Short guitar cable --> pedal --> long cable (or tie line) --> amp.

Low impedance output of the pedal is good for driving long cables without losing high end.

Post by **Aaronw** » Sat Aug 14, 2004 4:43 am

How is your control room and studio layed out? Are you running conduits, etc? Are you running through double wall construction, etc. Will you have a plate on a rack mount or a jack in the wall in the control room? How and where are you running your existing wiring?

You can still do the same method as I mentioned above. It would be worth while to use good cable.

The only point where you will have connections would be:

One from CR to Iso
Another from LR to ISO.
Maybe another from CR to LR.
Run each wire separate (one jack for each run...no daisy chains)

So you'll have two 1/4" jacks in the Iso room on a plate on the wall. ( one from CR and one from LR)

The LR, you'll also have two jacks. (one from CR and one going to ISO room)

The CR, you'll have 2 jacks. (one going to Iso room, and one to LR)

knightfly · Post by **knightfly** » Sat Aug 14, 2004 12:01 pm

This is never an easy subject - one thing that seriously affects the tonal result of a guitar/cable/amp combination is that some guitar pickups have impedances that exceed 100 kOhms - when you start to load that output down with the input of an amp, it changes the reactance of the RLC network that comprises the guitar pickup, cable, amp input circuitry, etc - all this BEFORE you even get to speakers, drive levels, room acoustics, mics, etc - this is why so many different tones can be had by just changing any one of the components or even a setting.

This interface between the guitar pickup and the amp input circuit is also what makes it difficult to compensate for cable lengths when running the guitar signal to a remote amp - if you use DI boxes, you've just added yet another variable - now, the guitar pickup is looking into a DIFFERENT input circuit, whether a passive transformer box or an active fet input - it's still DIFFERENT. And this loading is a large part of tonality as I mentioned earlier.

For cable distances of less than about 50 feet, I tend to agree with Aaron about using the best quality cable you can and just running direct into the amp. Choosing cables is one place where a multimeter with capacitance measuring capability comes in handy - you can, for example, play with different cables til you like the sound - then, remove that cable, measure its capacitance, and try to match that with your longer cable by buying lower capacitance cable so the total capacitance of the (longer) cable comes out the same as your favorite shorter cable.

Wire resistance would also come into this, but should be really minor (inaudible) since the guitar pickup (passive, not active) will dominate the R part of the RLC network that is your pickup, cable, and input circuit... Steve

Guest · Post by **Guest** » Sat Aug 14, 2004 2:56 pm

Well - my studio is still in the design stage. Not enough space in my main room to split in three rooms so the LR will have to wait and will probably be in another, distant room. But the way I plan things the ISO and CR will be separated by a double wall construction (using the inside-out wall construction), at the back of the CR, and I will be running conduits between the two rooms for the cables - in the ISO there will be a plate with sockets (4 XLR, 4 phantom powered XLR, 4 stereo jacks for headphones and 4 mono jacks for electric guitar). In the CR, the cables will be running along the wall in those platic boxes, to the patch bays on the side off the desk (with the XLRs to an XLR patch bay). The goal of going through the patch bayis to make it easier to swap guitars and basses, insert a DI box for both "unamped" and amped recording on separate tracks, or use the DI box as a splitter for the Johnson J-Station and H&K Tube preamp.

I hope you get a better idea of my setup. The total length of cable will probably be : 2 or 3 meters from guitar to patch bay, then 3 meters from patch bay to CR wall, then 2 meters to cross the wall (the conduit path cannot be straight for isolation) then 1 or 2 meters from the plate to the amp. That's around 10 meters to me (30ft).

Maybe I could put cable sockets at the back of the CR - but I found it less convenient than keeping everything centered at the patch bay. This way I would have : 2 or 3 meters to socket, if needed split through a DI to get to the patch bay, while the DI through goes through the wall to the socket plate. This keeps the guitar to amp cable length down to 7 or 8 m.

I came across this wiring setup that is called "semi-symmetric". Any interest in using this cabling for all intermediate guitar wiring ? Using this cabling would make it possible to use only symmetric patch bays, even with the non-symmetric IOs of my StAudio rack.

http://www.tubefreak.com/cablesw.htm

Post by **Aaronw** » Wed Aug 18, 2004 6:18 am

Do you have equipment racks where you can put a panel in w/ some connectors?

Guest · Post by **Guest** » Wed Aug 18, 2004 6:33 pm

Do you mean in the CR or in the booth ? in the CR, yes - equipment racks and jack patch bays - as well as an XLR board which groups together inputs of the various preamps and where the XLR cables coming from ISO and LR will be plugged.

In the LR and booth I thought there would be no equipment racks - but certainly a plate with XLR inputs for mics, guitar to amp connectors, a line out to a small headphones amp and phone connectors. Oh, and probably a phantom power box to make it easier (like which kind of mic is plugged into this preamp ? do I have to switch power on ? did I forget to switch it off ?)

Do you think it would be better to make all connections from CR to LR and ISO symmetric or even using balanced XLRs, and then use the cable setup in the previous post to plug non-symmetric devices ?

Thank you for your help.

Gwen

Post by **Aaronw** » Wed Aug 18, 2004 11:42 pm

But not all equipement provides us with balanced cables, most only have mono in- and outputs. In that case it is wise to wire your cables Semi Symmetric. For this you would need a cable with 2 cores and one shield, a typicle mic cable. Semi Symmetric cables are wired in the following way:
Core 1: connected to both tips
Core 2: connected to both sleeves
Shield: connected only to the sleeve from the OUTPUT device (for example the preamp side for a cable that goes to a poweramp)

That way the shield works as a true shield and the 2nd core functions as a connection between ground and allows a return signal to go through without any added noise. Because the growing use of mobile phones, etc. this is a good solution to prevent hum/noise in your signal and is used in all profesional applications. It's a simple trick, but it can help a lot.

If I read the info correctly, it's talking about using a shielded mic line. But you're using T/S unbalanced connectors. Basically tying the shield to the sleeve on one side and lifting it on the other.

So the side where you plug your guitar in would have the shield connected to the sleeve.

As Steve had mentioned, you may want to try a mock up of the setup to see if there may be issue's prior to doing a permanent install. This will give you an idea of any impeadance mismatches, hums, RF, or ghosts.

guitarguy · Post by **guitarguy** » Thu Aug 26, 2004 6:19 pm

Aaron hit it right. Keep the head by the guitarist and run the power amp cable to the speaker cabinet. If it's a combo just use something like a DI box, or a cable with a transformer (1/4 to XLR make sure it has a transformer) to change the line to a balanced signal so it can travel greater distances.

Guest · Post by **Guest** » Thu Aug 26, 2004 11:03 pm

Thank you for your input. What would be the impact of using a DI box on the sound/tone of the guitar ?

In this case, could I cable this way :
- guitar to DI
- balanced XLR for DI in CR to Amp booth
- XLR to guitar amp ?

Would it work that way or do I need another (matched) transformer on the amp side to "unbalance" the signal ?

I will be home for an extended length of time from mid-september on, and intend to play around with your ideas to find a correct setup.

guitarguy · Post by **guitarguy** » Fri Aug 27, 2004 5:07 am

A passive direct box should have no effect on your tone (less cheap components within).

At your patch point where you run the cable from the wall to the amp you would want a cable that was XLR back to 1/4", but the distance should be short enough to not need any boost from the point where you turn the balanced signal back to unbalanced.

knightfly · Post by **knightfly** » Fri Aug 27, 2004 7:40 pm

I disagree with your statement "A passive direct box should have no effect on your tone (less cheap components within)" - As I wrote earlier on,

"This interface between the guitar pickup and the amp input circuit is also what makes it difficult to compensate for cable lengths when running the guitar signal to a remote amp - if you use DI boxes, you've just added yet another variable - now, the guitar pickup is looking into a DIFFERENT input circuit, whether a passive transformer box or an active fet input - it's still DIFFERENT. And this loading is a large part of tonality"

I have a few different passive DI's, most of which typically have around 10k input impedance into the primary of the transformer - some guitar pickups have impedances of up to 150K, although about half that is more typical. When you feed a high impedance signal into a low impedance input, you load the signal down in level, and change the ratios of inductance/capacitance/resistance the pickup has to "look into" - this causes a noticeable change in tone; this is why better mic pre's have input impedance as a variable, so you can change the tonal characteristics of a microphone. Same thing with guitar.

Guitar amps tend to keep their input impedance high enough NOT to cause loading of pickups, and when you instead try to feed the guitar signal into a 10k direct box you change that relationship. You may decide that you LIKE this sound better or worse, but it WILL be DIFFERENT.

The main point I was trying to make is that you should at least be aware of the changes in tone seemingly innocent additions into the chain can cause, so you can watch for them and evaluate whether you like things better or worse... Steve

guitarguy · Post by **guitarguy** » Fri Aug 27, 2004 8:17 pm

I certainly will not argue with you on this. It's just things I've done and have had success with.. Although... I am constantly tweaking amps, so I may have failed to hear a difference. Regardless... I do believe you to have far more knowledge in this area, so I will pay greater attention to my comments.