You are here

How to use pro line level rack effects in guitar rig (properly)?

For all things relating to guitars, basses, amps, pedals & accessories.

How to use pro line level rack effects in guitar rig (properly)?

Postby DC-Choppah » Tue Sep 29, 2020 5:46 am

I really like the rack mount studio style effects units that I use in my guitar rig. But I fear I may be doing connection to the amps in a less than good way. It is quite noisy, and if there is a better way to do this I'd like to get it right. Doing a lot of recording with this.

The issue is that these rack mount effects use pro line level signals so I have to convert that output. But that leads to problems.


Guitar -> Preamp (Out to power amp) -> Rack effects (pro line level in/out)


So my guitar goes into a guitar preamp (with effects loop). The preamp has an output called (Out to power amp). This is a pro line level signal and is able to drive the rack effects directly.

I go through the rack effects, and at their output I now have a stereo pro line level signal.

Since the guitar amps are not happy with that pro line level signal (it would drive too hard and sounds terrible), I run into a stereo reamp box.

I then send the output of the reamp box to the amps.

Rack effects -> Reamp box -> Guitar amp


The sound is wonderful.


But here's the thing: The reamp box has level controls on it. https://artproaudio.com/product/dual-rdb/

When I turn DOWN the levels say below 50%, the rack effects start to clip. When these rack effects clip they are very harsh. SO I have to keep them from clipping. To do that I have to crank up the reamp all the way up. When I do that the noise goes up.

There must be a better way to do this.

I would prefer to run where the noise is low, but not have the rack effects clipping.


Any thoughts on why the rack effects clip when I turn DOWN the reamp box? Any ideas would be appreciated as to a better way to hook this up.
User avatar
DC-Choppah
Frequent Poster
Posts: 1622
Joined: Fri Jul 20, 2012 12:00 am
Location: MD, USA

Re: How to use pro line level rack effects in guitar rig (properly)?

Postby Hugh Robjohns » Tue Sep 29, 2020 10:45 am

DC-Choppah wrote:Guitar -> Preamp (Out to power amp) -> Rack effects (pro line level in/out) .... Rack effects -> Reamp box -> Guitar amp

When I turn DOWN the levels say below 50%, the rack effects start to clip.

This makes no sense! How can adjusting the output level cause the input level to rise?

Something is either not connected as you suggest, or the problem is not what you think it is.

Could it be that the effects unit is not 'clipping' -- as in an input overload -- but that its output stage is being loaded in a way it doesn't like and is distorting in complaint?

Are you using balanced cables to the ART reamp box or standard TS cables?
User avatar
Hugh Robjohns
Moderator
Posts: 28695
Joined: Fri Jul 25, 2003 12:00 am
Location: Worcestershire, UK
Technical Editor, Sound On Sound

Re: How to use pro line level rack effects in guitar rig (properly)?

Postby DC-Choppah » Thu Oct 01, 2020 6:22 am

Hugh Robjohns wrote:
DC-Choppah wrote:Guitar -> Preamp (Out to power amp) -> Rack effects (pro line level in/out) .... Rack effects -> Reamp box -> Guitar amp

When I turn DOWN the levels say below 50%, the rack effects start to clip.

This makes no sense! How can adjusting the output level cause the input level to rise?

Something is either not connected as you suggest, or the problem is not what you think it is.

Could it be that the effects unit is not 'clipping' -- as in an input overload -- but that its output stage is being loaded in a way it doesn't like and is distorting in complaint?

Are you using balanced cables to the ART reamp box or standard TS cables?


As I bring down the level controls of the Art reamp box, the guitar volume coming out of the speakers goes down as expected. However, the meter on the Lexicon MX200 begins to rise. As the level is turned down further, the meter starts to show clipping (red) and the quieter sound becomes very harsh and indeed digitally clipped sounding.

The two rack effects units that I use is series are

Aphex 109 eq
Lexicon MX200

Both units are clipping when I bring the volume down. The Aphex has no meter, but it does have a clipping light that starts to glow red. The Aphex has a level switch for the inputs and is set to +4 dBV (instead of -10 dBV). The Lexicon has no choice, it only runs at +4.

The guitar signal comes out of the (unbalanced) 'Out to Poweramp' of the Art Powerplant preamp. This drives the +4 dBV effects properly. I split this mono signal with a Y cord and feed the unbalanced L and R inputs of the Aphex.

The output of the Aphex uses balanced TRS cables (Left and Right) and feeds the balanced inputs of the MX200. Balanced cables take the output of the MX200 to the balanced inputs of the Art Re-amp box.

From the Re-amp box, the cables are unbalanced and go to the amps. One amp for left, one amp for right.

Clipping is happening in both of the rack effects units as the levels of the Re-amp box are turned down. But the sound gets very quiet at the same time. As the levels are brought up to maximum on the Re-amp box, the guitar gets very loud, the noise level goes up, but the levels shown on the MX200 only light up the first bar. At this setting there is no harsh clipping.

This is very strange :sick:


Please understand I don't like the constant noise coming from the amps. I know that if I could turn the reamp gain down, the noise I hear would go down to being just a normal amp hiss.

But with the knobs at max, the noise is louder (hum and hiss both). This is fatiguing to listen to when I am doing long sessions, and makes we not want to practice with the amp on. Recording, you would not hear it. But it is a tiring kind of noise.

I feel that something is wrong and I should be able to lower this noise.

The weird backward clipping problem is some kind clue I hope.

This is a mystery.
User avatar
DC-Choppah
Frequent Poster
Posts: 1622
Joined: Fri Jul 20, 2012 12:00 am
Location: MD, USA

Re: How to use pro line level rack effects in guitar rig (properly)?

Postby resistorman » Thu Oct 01, 2020 2:17 pm

:beamup:
User avatar
resistorman
Frequent Poster
Posts: 1076
Joined: Sun Nov 22, 2015 1:00 am
Location: Asheville NC

Re: How to use pro line level rack effects in guitar rig (properly)?

Postby DC-Choppah » Thu Oct 01, 2020 4:08 pm

The configuration of the guitar amplifiers is causing this mysterious, backward clipping effect.


The way the amplifiers are normally set up is this:


Output of re-Amp box (Left) -> Fender Deluxe Reverb

Output of re-Amp box (right) -> A/B/Y switch set to Y -> Polytune Mini Brute and Hiwatt Combo amp

I get the backward clipping effect. By that I mean that when I turn down the re-Amp knobs, the MX200 starts to clip.


But when I turn off (but leave plugged in) the two amps on the right side, the backward clipping doesn't happen anymore. The levels seen on the meter of the MX200 stay the same regardless of the position of the knobs on the Re-Amp box.
User avatar
DC-Choppah
Frequent Poster
Posts: 1622
Joined: Fri Jul 20, 2012 12:00 am
Location: MD, USA

Re: How to use pro line level rack effects in guitar rig (properly)?

Postby resistorman » Fri Oct 02, 2020 3:29 am

This is such a strange problem. You’ll need to keep trying to narrow it down for us.
User avatar
resistorman
Frequent Poster
Posts: 1076
Joined: Sun Nov 22, 2015 1:00 am
Location: Asheville NC

Re: How to use pro line level rack effects in guitar rig (properly)?

Postby Hugh Robjohns » Fri Oct 02, 2020 3:37 pm

DC-Choppah wrote:The guitar signal comes out of the (unbalanced) 'Out to Poweramp' of the Art Powerplant preamp. This drives the +4 dBV effects properly. I split this mono signal with a Y cord and feed the unbalanced L and R inputs of the Aphex.

The output of the Aphex uses balanced TRS cables (Left and Right) and feeds the balanced inputs of the MX200. Balanced cables take the output of the MX200 to the balanced inputs of the Art Re-amp box.

From the Re-amp box, the cables are unbalanced and go to the amps. One amp for left, one amp for right.

The implication and only logical explanation I can think of from the symptoms you describe is that the amp input signals are getting back into the signal path somewhere prior to the 'Out to Power Amp' socket.... possibly with a polarity inversion along the way!

Are there any other connections between the right channel amps and the preamp?

And have you checked the mains grounding arrangements of all the amps?

Since you have proven that the problem lies with one of both of the right channel amps and/or the ABY switch, I suggest you simplify that part of the signal chain by connecting one amp at a time for starters...
User avatar
Hugh Robjohns
Moderator
Posts: 28695
Joined: Fri Jul 25, 2003 12:00 am
Location: Worcestershire, UK
Technical Editor, Sound On Sound

Re: How to use pro line level rack effects in guitar rig (properly)?

Postby DC-Choppah » Fri Oct 02, 2020 10:19 pm

Thank you Hugh and Resistorman. I appreciate that you believe me. I can understand that some might think that what I heard was impossible and leave me to wallow. That you for sticking with me on this one!!


I found two things.

1) The physical location of the Dual Reamp Box (DRB) actually matters!

Normally, I had the DRB sitting on top of the rack which puts it about 1-2" above the Art Preamp.

I have moved things around and now have the reamp box sitting on the floor. I no longer can duplicate the backward clipping problem with the DRB box on the floor! The levels behave normally.


BTW This is actually my Reamp box: https://artproaudio.com/framework/uploa ... ualrdb.pdf

It is slightly different than the model I linked to above. But this one is exactly mine.


My original issue, please bear with me, was simply extra noise coming at me from the amps which is tiring. That was my problem and why I am still in need of help.

2) I have found that one of the channels of the Fender Reverb is very noisy. This is the 'Reverb' Channel. The channel on the right of the Deluxe reverb, with extra controls.
Even if I unplug completely from the Fender Amp, the noise is fairly extreme on this channel. Sounds like radio static from an old fashioned radio. This noise is not present on channel 1 of the Fender Reverb.

I do use both channels of the Fender Amp. One channel is direct from the guitar, the other channel is through the preamp and effects. Basically dry and effects channel.
User avatar
DC-Choppah
Frequent Poster
Posts: 1622
Joined: Fri Jul 20, 2012 12:00 am
Location: MD, USA

Re: How to use pro line level rack effects in guitar rig (properly)?

Postby resistorman » Fri Oct 02, 2020 10:28 pm

Could be the reverb return tube?
User avatar
resistorman
Frequent Poster
Posts: 1076
Joined: Sun Nov 22, 2015 1:00 am
Location: Asheville NC

Re: How to use pro line level rack effects in guitar rig (properly)?

Postby Hugh Robjohns » Fri Oct 02, 2020 11:49 pm

DC-Choppah wrote:I found two things.

1) The physical location of the Dual Reamp Box (DRB) actually matters!

Ooh! What fun! I dont know if the preamp uses audio transformers, but I'm thinking magnetic coupling between transformers in the reamp box and preamp (or even geetar pickups)?

2) I have found that one of the channels of the Fender Reverb is very noisy. This is the 'Reverb' Channel. The channel on the right of the Deluxe reverb, with extra controls.
Even if I unplug completely from the Fender Amp, the noise is fairly extreme on this channel. Sounds like radio static from an old fashioned radio. This noise is not present on channel 1 of the Fender Reverb.

Sounds like a well identified faulty amp channel to me. A trip to the menders is called for.
User avatar
Hugh Robjohns
Moderator
Posts: 28695
Joined: Fri Jul 25, 2003 12:00 am
Location: Worcestershire, UK
Technical Editor, Sound On Sound

Re: How to use pro line level rack effects in guitar rig (properly)?

Postby DC-Choppah » Sat Oct 03, 2020 12:03 am

Hugh Robjohns wrote:Ooh! What fun! I dont know if the preamp uses audio transformers, but I'm thinking magnetic coupling between transformers in the reamp box and preamp (or even geetar pickups)?

Thank you for that Hugh. I was beginning to doubt myself on this one. But now that you mention it, when I was doing my testing and seeing the 'backward clipping' problem, I was sitting, with guitar, directly in front of the whole rig, with the DRB inches from the guitar's pickups (high output kind too!) . I mean I am playing while tiddling knobs. When I move the DRB to the floor it is maybe 4 feet away from the guitar. In that position no more ghosts!
User avatar
DC-Choppah
Frequent Poster
Posts: 1622
Joined: Fri Jul 20, 2012 12:00 am
Location: MD, USA

Re: How to use pro line level rack effects in guitar rig (properly)?

Postby resistorman » Sat Oct 03, 2020 3:28 am

Maybe there's a bad ground on a transformer cover. Magnetic coupling is a distinct possibility. For instance, you can't use a single coil pickup in a theater with a loop hearing aid system.
User avatar
resistorman
Frequent Poster
Posts: 1076
Joined: Sun Nov 22, 2015 1:00 am
Location: Asheville NC

Re: How to use pro line level rack effects in guitar rig (properly)?

Postby DC-Choppah » Sat Oct 03, 2020 10:50 pm

Fender Amp is with the tech to fix the noisy channel.


With DRB on the floor, everything is acting normally now. The gain setting of the DRB have no effect on the levels seen on the rack effects. I can dial in the gain stages to get good levels and low noise.
User avatar
DC-Choppah
Frequent Poster
Posts: 1622
Joined: Fri Jul 20, 2012 12:00 am
Location: MD, USA

Re: How to use pro line level rack effects in guitar rig (properly)?

Postby Hugh Robjohns » Sat Oct 03, 2020 11:58 pm

:thumbup: good plan -- and keep the guitar away from things with transformers inside!
User avatar
Hugh Robjohns
Moderator
Posts: 28695
Joined: Fri Jul 25, 2003 12:00 am
Location: Worcestershire, UK
Technical Editor, Sound On Sound

Re: How to use pro line level rack effects in guitar rig (properly)?

Postby DC-Choppah » Sun Oct 04, 2020 1:12 am

resistorman wrote:Maybe there's a bad ground on a transformer cover. Magnetic coupling is a distinct possibility. For instance, you can't use a single coil pickup in a theater with a loop hearing aid system.

I don't think the DRP is defective. It seems to just radiate an aura that the guitar picks up. I bet they all do that since the audio signal is transformer coupled in the DRP.

There are no transformers in the preamp, except for the power supply.

The problem appears to be DRP to guitar pickup coupling.

I moved the DRP back on top of the preamp. As long a I walk away from it with the guitar, the backward clipping problem doesn't happen.

But I do want to tuck the DRP back into the rack and forget about it. I wish where was a way to shield the DRP some how So I don't have this problem again.

Or perhaps a way to convert the +4 dB signal to guitar amp without using transformers?
User avatar
DC-Choppah
Frequent Poster
Posts: 1622
Joined: Fri Jul 20, 2012 12:00 am
Location: MD, USA

Next