Best option for running dual guitar amps in studio

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Best option for running dual guitar amps in studio

Postby Text_Edifice » Thu Jun 15, 2017 11:41 am

I have an album I'm working on and need to run two amps simultaneously. I don't have anything in my studio to do this without hum / other weirdness.

Can isolate one amp with a couple of DI's to deal with the hum but doesn't quite sound right and the amps in question are old oddities with no real tone controls.

Radial Twin City a/b/y seems like a good option but wondering what you guys use?
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Re: Best option for running dual guitar amps in studio

Postby walding » Thu Jun 15, 2017 3:30 pm

Are you going for stereo or just 2 different amps for tone/sound?
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Re: Best option for running dual guitar amps in studio

Postby Text_Edifice » Thu Jun 15, 2017 3:46 pm

Bit of both, 2 amps running manually syncd (so not really) trems.
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Re: Best option for running dual guitar amps in studio

Postby Paul Maybury » Thu Jun 15, 2017 4:52 pm

Hi, I use one of these when I have a noise and/ or polarity problem.
http://www.radialeng.com/bigshotaby.php
It very rare that it's needed, but really comes into it's own when running two bass amps. The polarity switch is a gem in that situation.
Most of the time I use a passive split, or if they are old amps with two inputs per channel, I just gang them together from the unused input to the second amp. Never had a problem doing this with guitars.
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Re: Best option for running dual guitar amps in studio

Postby Text_Edifice » Thu Jun 15, 2017 6:08 pm

Thanks Paul,

do you run into any level / other issues with the radial?

I hadn't thought about just jumpering the inputs - I may be overthinking the problem.
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Re: Best option for running dual guitar amps in studio

Postby Paul Maybury » Thu Jun 15, 2017 6:30 pm

Hi Dave, I haven't noticed any level problems but the amps I have used it with have volume controls....
Another way to do it is to use a tuning pedal with two outputs. They are usually buffered and work fine.
I bought the Radial for one live show where the bass player wanted to use an SVT and a Marshall stack. The polarity switch was needed in this case, and the galvanic isolation dealt with any ground loop issues. Since then I've only used it rarely, mainly for the polarity flip. I'm very glad I have it in those instances, such as an old organ running into a Leslie and a guitar amp.
The unit has a transformer in it and is passive (psu only needed if you want the status LEDs to work), the ability to polarity flip an unbalanced signal depends on the transformer, as does the isolation. Everybody loves transformers don't they? Makes everything more betterer.
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Re: Best option for running dual guitar amps in studio

Postby Text_Edifice » Thu Jun 15, 2017 6:40 pm

I guess the concern I have with losing level is that the old odd tube amps I am using are inherently noisy.
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Re: Best option for running dual guitar amps in studio

Postby Paul Maybury » Thu Jun 15, 2017 6:48 pm

Hi Dave, I'd try a buffered dual output pedal of some kind then. Most guitarists have a tuner like that in their kit.
Any passive split is going to drop the level. Of course the loading of the guitar pickup will change too. But if it sounds good...

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Re: Best option for running dual guitar amps in studio

Postby Text_Edifice » Thu Jun 15, 2017 9:24 pm

Have tried a buffer split and it doesn't work so good in my room / with these amps.

I'm probably overthinking it - I could also reamp I guess to get the second amp.

The thing is the amp sounds are going to be very exposed / prominent + there's an interesting interplay that happens between player / amp with the trems pushing / pulling the tempo that I want to capture as a perfromance, not jury rig later.

It sounds like one of the radial thingo's is the go.
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Re: Best option for running dual guitar amps in studio

Postby tunetown » Fri Jun 16, 2017 9:37 am

I use one of these http://www.littlelabs.com/pcp.html . Not cheap but works great.
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Re: Best option for running dual guitar amps in studio

Postby Chris H » Fri Jun 16, 2017 10:06 am

I use the direct out on my electro harmonix memoryman for this.
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Re: Best option for running dual guitar amps in studio

Postby Text_Edifice » Fri Jun 16, 2017 10:14 am

I've looked at the PCP before as I like using guitar pedals on mixes. It's too expensive for this use for me (and I ended up just running a couple of DI's and DIY reamp boxes to similar effect).

The circuit looks like an active DI into a series of transformer isolated outputs with phase + ground lift? So a buffer stage into a couple of daisy chained DI's looks like it would produce a similar result (also the radial).

Must be an odd enough thing to do that the market is small so margins need to be a bit higher?
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Re: Best option for running dual guitar amps in studio

Postby Text_Edifice » Sat Jun 17, 2017 11:42 am

So I've been thinking about this a bit more and I reckon it's almost easier just to build something (famous last words).

I think a passive splitter itself is easy, just needs a transformer + ground lift + phase switch + jacks. It looks basically like a DI circuit with an isolating 1:1 transformer for the second output.

I am thinking about adding a variable resistor to ground on the output of each side of the split tingo allow for lower the ouptut impedance on each side. This last bit might be unnecessary as I'm borrowing the idea from the way some boost pedals try and offer impedance mathcing into older fuzz pedals. It may not make sense without the boost up front.

Whadya reckon brains trust?
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Re: Best option for running dual guitar amps in studio

Postby Text_Edifice » Sun Jun 18, 2017 11:08 am

ok so...

after a bit more thinking I'm going to try and build a design a bit like this http://www.jensen-transformers.com/wp-c ... /as014.pdf

But with a different buffer stage (tl071, single 9v), ground lift to the xformer and phase reverse as per the radial and only one split.

I have some AWA 1:1 transformers (600:600) that I think will work ok post-buffer. Apparently EDCOR make suitable 10k and 15k 1:1 and I wonder if they'd work better. Will use what I have first I guess and see...
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Re: Best option for running dual guitar amps in studio

Postby rick » Wed Jun 21, 2017 3:57 pm

IMG_2469.JPG
I have a little labs pcp intrument distro
This IS the droid your looking for
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Re: Best option for running dual guitar amps in studio

Postby zenelectro » Fri Jun 23, 2017 10:56 am

Text_Edifice wrote:ok so...

after a bit more thinking I'm going to try and build a design a bit like this http://www.jensen-transformers.com/wp-c ... /as014.pdf

But with a different buffer stage (tl071, single 9v), ground lift to the xformer and phase reverse as per the radial and only one split.

I have some AWA 1:1 transformers (600:600) that I think will work ok post-buffer. Apparently EDCOR make suitable 10k and 15k 1:1 and I wonder if they'd work better. Will use what I have first I guess and see...


Opamp:

For high impedance guitar pickup the opa627 on +-9V is about the best choice as it has a bootstrapped front
end that has very low capacitance. They also sound very good. TL071 on a single supply is about the worst choice
but at the end of the day if you cant hear a difference... well the 627 is pretty expensive. Bottom line
put an opamp socket in so you can have a swapsy session.

Supplies:

+-9V is the best option and if you want to switch power with IP socket just use an isolated double switched IP
socket. Running +- supplies with a 627 or equivalent OPA will allow you to direct couple the opamp to transformer(s) and flick the OP coupling cap.

Transformers:

Personally I would want transparent transformers as I want my guitar sig to get to the amp as pure as possible -
However maybe you could have 1 x Nickel core and 1 x Steel core for options. I recommend Cinemag, they
will help you with the right choice. They are fantastic people to deal with, the transformers sound great and are
cheaper than Jensens for similar quality. Whatever transformers you use, put a 10k square wave through the unit
and look at OP. If it's ringing all over the shop snub it (with R//C) to get cleanest square wave.

Having said all of the above, you may find that a sigle supply 071, cap coupled to an Edcor tranny is fine for
you, it just depends how fussy you (and your ears) are.

T
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Re: Best option for running dual guitar amps in studio

Postby Text_Edifice » Fri Jun 23, 2017 12:20 pm

Thanks Terry,

that's really useful.

The TL071 was spec'd in another buffer design and I have a pile of them to hand - the other option I was tossing up was using both sides of a TL072 ala http://www.muzique.com/lab/superbuff.htm as I also have a bunch of ne5532's and tl072s.

I hadn't considered cinemag but I'll take a look. The AWA's were used for distribution in an ABC install so I'm hoping they'll be ok / reasonably transparent. If I build the thing and it doesn't do the job I'll start looking at swapping components out for newer / higher spec but by the time I've paid for an opa627 + cinemag transformer the radial looks very cost effective.
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Re: Best option for running dual guitar amps in studio

Postby zenelectro » Mon Jun 26, 2017 12:06 pm

Text_Edifice wrote:Thanks Terry,

that's really useful.

The TL071 was spec'd in another buffer design and I have a pile of them to hand - the other option I was tossing up was using both sides of a TL072 ala http://www.muzique.com/lab/superbuff.htm as I also have a bunch of ne5532's and tl072s.

I hadn't considered cinemag but I'll take a look. The AWA's were used for distribution in an ABC install so I'm hoping they'll be ok / reasonably transparent. If I build the thing and it doesn't do the job I'll start looking at swapping components out for newer / higher spec but by the time I've paid for an opa627 + cinemag transformer the radial looks very cost effective.


I have a couple of spare 627's here with dodgy legs. If you decide to build this and want one (free) pm me your
details. Just straighten the legs and solder some small wires to them, they'll be fine.

cheers

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