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Send and Return from Guitar Amp to Patchbay - Will I Explode??!!!

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Send and Return from Guitar Amp to Patchbay - Will I Explode??!!!

Postby paulsmusic » Mon Apr 26, 2021 8:51 am

Hi all, I've got a Victory Deluxe guitar amp that I'm using with an HX FX pedal, and a UAD Ox Top. I mainly use them in the studio, and would like to hook it all up to my patchbay. I've also got a UAD 7-10D preamp, and thought it would be cool if I could plug my guitar into the 710-D preamp first, and send the signal via the FX send to the patchbay.

I'm using the '4-cable method' of connecting my guitar into the HX-FX, HX FX send into the Victory input, Victory FX send to HX FX return, HX output to Victory FX return, Victory amp out to UAD Ox amplifier input, UAD Ox out (analogue L/R) to interface.

If I patched these connections individually into the patchbay, will it be safe? I'm mostly worried about the send/return from the Victory amp, as although I like a bit of noise, explosions aren't currently in my repertoire!!

I also wondered about what happens with phantom power, when you send it from balanced send / returns from preamps like the 4-710D to a patchbay (I'm not planning to use phantom power with my guitar input I hasten to add!)?
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Re: Send and Return from Guitar Amp to Patchbay - Will I Explode??!!!

Postby Hugh Robjohns » Mon Apr 26, 2021 9:38 am

paulsmusic wrote:If I patched these connections individually into the patchbay, will it be safe?

Yes... but obviously you'll need to take care not to patch outputs to inputs of the same devices and create howl-round loops! And be aware of potentially different signal levels for different devices, as well as balanced/unbalanced formats.

A patch-bay is just a way of collecting a bunch of existing connections together in one convenient place. There's nothing magical about it.

I also wondered about what happens with phantom power, when you send it from balanced send / returns from preamps like the 4-710D to a patchbay

Bad things happen! Or can happen... Phantom power and patchbays really don't work very nicely together and there is the potential to damage preamp inputs and mic outputs if patching via a patch-bay while phantom is switched on.
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Re: Send and Return from Guitar Amp to Patchbay - Will I Explode??!!!

Postby ef37a » Mon Apr 26, 2021 11:45 am

One thing to be aware of is the likely lower level of the FX loop signals. Assuming the rest of the gear going through the patchbay is running at the normal studio level of +4dBu (about 1volt) guitar amp loops generally run at 'pedal' level of -10dBV (about 300mV) and so patching FX out to other gear will give low levels*, no biggy but patching anything at +4 to FX return will be LOUD!

There is also the slight problem that the loop will be unbalanced whereas I assume the rest of the patched gear is balanced? If all that is needed is a 'remote' FX loop maybe just build two jacks in a box and have it handy?

*Some (cough!) amplifier manfctrs give you a choice of +4 and neg ten loop levels!

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Re: Send and Return from Guitar Amp to Patchbay - Will I Explode??!!!

Postby paulsmusic » Mon Apr 26, 2021 12:39 pm

Hugh Robjohns wrote:Bad things happen! Or can happen... Phantom power and patchbays really don't work very nicely together and there is the potential to damage preamp inputs and mic outputs if patching via a patch-bay while phantom is switched on.

Thanks Hugh! So should I not be using the FX send/returns on the 4-710D at all when I'm running phantom power? I don't have any mics connected to the patchbay directly, but I have connected the FX send/returns on the 4-710D to the patchbay (with the returns below the sends on each channel of the patch).

I'd planned to patch in an external compressor when recording vocals (which would mean phantom power sometimes being active). Generally I use a couple of favoured tube mics, though, which have their own power supply. Would it be safe to use these, connected to the 4-710 D and onto the patchbay, (with no phantom power coming from the 4-710D)?
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Re: Send and Return from Guitar Amp to Patchbay - Will I Explode??!!!

Postby paulsmusic » Mon Apr 26, 2021 12:45 pm

ef37a wrote:One thing to be aware of is the likely lower level of the FX loop signals.
*Some (cough!) amplifier manfctrs give you a choice of +4 and neg ten loop levels!

Dave.

Thanks Dave! Yes, you're right, the FX send from the V40 Deluxe is running at a lower level. I think I need to figure out another way of doing what I need to do. Sometimes I like to play guitar at one end of my studio (where the amp/cab/Ox top are set up), but other times I want to be near the computer, which is also where the patchbay is. It would be handy just to be able to plug and play either end of the studio without having to change lots of cables etc.
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Re: Send and Return from Guitar Amp to Patchbay - Will I Explode??!!!

Postby Luke W » Mon Apr 26, 2021 1:29 pm

paulsmusic wrote:So should I not be using the FX send/returns on the 4-710D at all when I'm running phantom power? I don't have any mics connected to the patchbay directly, but I have connected the FX send/returns on the 4-710D to the patchbay (with the returns below the sends on each channel of the patch).

In that case you'll be fine to use the inserts as normal, the phantom power on the 4-710D will only be heading to the XLR mic inputs, so if it's just the send/return points you've got connected to your patchbay then that's not a problem.

Hugh's warning (I assume) was regarding using a patchbay to make connections to the mic inputs themselves, which you've said you're not doing.
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Re: Send and Return from Guitar Amp to Patchbay - Will I Explode??!!!

Postby paulsmusic » Mon Apr 26, 2021 7:09 pm

Luke W wrote:
paulsmusic wrote:So should I not be using the FX send/returns on the 4-710D at all when I'm running phantom power? I don't have any mics connected to the patchbay directly, but I have connected the FX send/returns on the 4-710D to the patchbay (with the returns below the sends on each channel of the patch).

In that case you'll be fine to use the inserts as normal, the phantom power on the 4-710D will only be heading to the XLR mic inputs, so if it's just the send/return points you've got connected to your patchbay then that's not a problem.

Hugh's warning (I assume) was regarding using a patchbay to make connections to the mic inputs themselves, which you've said you're not doing.

Phew - I'm glad about that!
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Re: Send and Return from Guitar Amp to Patchbay - Will I Explode??!!!

Postby ef37a » Tue Apr 27, 2021 12:31 pm

paulsmusic wrote:
ef37a wrote:One thing to be aware of is the likely lower level of the FX loop signals.
*Some (cough!) amplifier manfctrs give you a choice of +4 and neg ten loop levels!

Dave.

Thanks Dave! Yes, you're right, the FX send from the V40 Deluxe is running at a lower level. I think I need to figure out another way of doing what I need to do. Sometimes I like to play guitar at one end of my studio (where the amp/cab/Ox top are set up), but other times I want to be near the computer, which is also where the patchbay is. It would be handy just to be able to plug and play either end of the studio without having to change lots of cables etc.

What sort of distance are we talking about Paul? There is usually no problem with a good quality guitar cable of 3 mtrs, even a bit more but I assume you want the effects near you and thus extend the loop jacks?
The problem there is the output impedance of the FX send on the amplifier. It should be low, less than 1k Ohm, better a few 100 Ohms but some FX loops on some amps (yes, even quite expensive ones!) are poorly designed in that regard. A high source impedance will give you treble loss ("tone suck" in gitist's parlance) and possibly some hum.

However, that amp has a "hard bypass" switch for the FX loop so, get a guitar cable rather longer than you need for the room and link FX out to in. You can now flip the bypass switch and compare the direct and 'long' run sound quality and noise levels. If satisfactory, build the remote box.

Dave.
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Re: Send and Return from Guitar Amp to Patchbay - Will I Explode??!!!

Postby paulsmusic » Tue Apr 27, 2021 1:14 pm

ef37a wrote:
What sort of distance are we talking about Paul? There is usually no problem with a good quality guitar cable of 3 mtrs, even a bit more but I assume you want the effects near you and thus extend the loop jacks?
The problem there is the output impedance of the FX send on the amplifier. It should be low, less than 1k Ohm, better a few 100 Ohms but some FX loops on some amps (yes, even quite expensive ones!) are poorly designed in that regard. A high source impedance will give you treble loss ("tone suck" in gitist's parlance) and possibly some hum.

However, that amp has a "hard bypass" switch for the FX loop so, get a guitar cable rather longer than you need for the room and link FX out to in. You can now flip the bypass switch and compare the direct and 'long' run sound quality and noise levels. If satisfactory, build the remote box.

Dave.

Thanks Dave! A 3 metre cable should reach from the amp to my desk, so will give your suggestions a try. Yes, I would want the FX near my feet as well, as I use a combination of the HX-FX, Ox software, and UAD plug-ins to create my guitar presets (hence wanting to be near the computer at times).
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