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Phase problem with VT Bass and Shutle 9.0

Overdrive777

Overdrive777

May 29, 2006
379
435
Stockholm, Sweden
Disclosures
Endorsing Artist: Mesa/Boogie
#1
Hi!
I am trying to to use my Shuttle 9.0 and my VT Bass Deluxe.
My goal is to blend a distorted signal from the VT Bass and a clean signal from the Shuttle separately mixing both together in my cabinets using the poweramp of the Shuttle.
Sending signal from the bass to the VT Bass Deluxe, then the VT output to Aux In on the Shuttle meanwhile from the parallel out of the VT to the input of the Shuttle.
When the signal from the VT Bass is too similar to the clean Shuttle they almost phase out eachother.
Anyone knows why? Is there a possibility to shift the phase on one of the signals? If so how do I do that?

All help is appreciated!
 
#3
I have observed what you have described (using a Shuttle 6 and a VTD), and suspect that your theory is correct regarding a phasing issue between the front panel input and the rear panel AUX in.

But, I can't prove it. The Tech21 and GB guys post here a lot. Between the two of them, maybe they can perhaps offer some insight.

Brian
 
#5
This is not how the aux input was really intended to be used, though it is possible. Depending on the polarity of the signal coming into the aux in relative to the main signal path, it is possible to have an unintentional polarity flip. Looking at the schematic, it looks like the main and aux signal paths polarity are the same, but there are also filters and eq that will shift phase that can cause some of the same issues either with the VT Bass or the Shuttle (or anytime 2 identical signals that contain different filtering are combined.

Try flipping the polarity (if possible) on the VT Bass and see if that resolves it, otherwise it's probably submmed phase shifts causing the problem.

This is something we are very aware of when designing things with parallel paths like mixing consoles and effects. The aux in on the shuttle was not intended to be a parallel path return.
 
#9
Ah, I see...a clean blend + VT. Sorry...I'm a little thick today and didn't read as close as I should. I just saw "out of phase" and suggested the path of least resistance ;) Well, wish I could help you, but this one's beyond my scope. I'm sure someone will tell you what you need soon enough, though.
 
#10
Overdrive777 said:
Thank you Agedhorse for your answer.
Yes, I'm trying to mix two separate channels.
It is not possible to flip the phase on the VT. Do you know if there's a special cable or a small box to flip the switch with?
Click to expand...

Not that I am aware of. It can be done with a 1:1 ratio transformer, or with an active circuit, but not with a cable due to the ground reference.
 
#11
You could have your VTD modded with a clean blend knob. www.putnamguitars.com does great mods on Tech 21 stuff. Or you could get a small mixer and premix it into the front of the Shuttle. But the clean blend mod would be less unwieldy. I think since both signals are going to the same place anyway it'd be just as effective, eh?
 
#12
JimmyM said:
You could have your VTD modded with a clean blend knob. Link Removed does great mods on Tech 21 stuff. Or you could get a small mixer and premix it into the front of the Shuttle. But the clean blend mod would be less unwieldy. I think since both signals are going to the same place anyway it'd be just as effective, eh?
Click to expand...

It's a good idea. The thing is that I thought that EQ only the clean channel with the Shuttle would be good to have clean lows and mids mixed with distorted mids and and highs from the VT...
Maybe I'm just overthinking it and just put the VT in the input of the Shuttle:D
I just love the clean sound from the Shuttle so much!:)

I just recorded my band's new album with one channel clean Shuttle and one distorted VT for a fantastic Eddie Jackson of Queensryche-ish sound. I was just thinking of reproducing it live...:)
 
#13
I hear ya...that's why you see some folks using two rigs or taking a clean DI and micing an amp. I used to do it using two channels of an SVT. It does sound very good to blend distortion and clean tones. But with this phase problem you're having, I really think your only real solution is a compromise. Unless of course you buy a second Shuttle ;)
 
#14
JimmyM said:
I hear ya...that's why you see some folks using two rigs or taking a clean DI and micing an amp. I used to do it using two channels of an SVT. It does sound very good to blend distortion and clean tones. But with this phase problem you're having, I really think your only real solution is a compromise. Unless of course you buy a second Shuttle ;)
Click to expand...

I am not the OP, but I did encounter his problem, and I thought seriously of getting a Shuttle 3 to go with the 6, running dirty to the 3 and clean to the 6.

Brian
 
#15
JimmyM said:
I hear ya...that's why you see some folks using two rigs or taking a clean DI and micing an amp. I used to do it using two channels of an SVT. It does sound very good to blend distortion and clean tones. But with this phase problem you're having, I really think your only real solution is a compromise. Unless of course you buy a second Shuttle ;)
Click to expand...

I could buy another Shuttle but then I need to have two cabinets right? I would realy like to use one 8x10. I think maybe the best compromise would be, like you suggested Jimmy, to let Putnam put a blend in the VT so I could use the VT in the Shuttle input.

If it is the Aux In that is the problem, would it be possible to take the Shuttle signal from the Effect send and then have like a "2 to 1-pedal" to blend in the VT and then back to Effect return on the Shuttle with both signals? I then need to split the signal from the bass before the Shuttle. I don't know if I will have the same phase problem then...
 
#16
I see you figured out my misspelling of Putnam in that link ;) Oh well, sorry bout that, but at least it didn't direct you to spyware.

I think you'd still have the phase problem if you did that new plan. And you would need two cabs if you got a second amp. I think a blend pedal or the Putnam mod is the way to go. Especially when you consider you'll only get one line for the bass on a lot of gigs. It's quick and easy and will in all likelihood sound pretty much the same, at least enough for live work.
 
#19
Overdrive777 said:
If it is the Aux In that is the problem, would it be possible to take the Shuttle signal from the Effect send and then have like a "2 to 1-pedal" to blend in the VT and then back to Effect return on the Shuttle with both signals? I then need to split the signal from the bass before the Shuttle. I don't know if I will have the same phase problem then...
Click to expand...

It could be either the VT or the aux in routing that's the problem, can't tell without testing with the VT.

The effects send to effects return with a blend pedal would eliminate any possibility of a polarity issue with the Shuttle however, and this is how the signal routing was intended. Then, you are left with whatever is presented by the VT.
 
#20
There can be two things that may be causing this issue. Phase shift or phase flip or reverse. When you use EQ the phase will always shift and it could be that the two EQ's of the units are fighting with each other and flipping the phase may not fix this.

Our products are designed to be phase coherent from input to output as I'm sure the Genz Benz products are as well.

What you can try to see if it's a phase shift vs phase reverse issue is to get an xlr to 1/4" cable. The cable will need to go from the XLR out of the VTBD to the aux in of the amp. To reverse the phase you need to change pins 2 and 3 on the XLR. You can also buy an inexpensive adapter as well. This way you can see if reversing the phase solves or helps your problem.
 

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