Running an external preamp into an interface

[MikeMcKew]

Hey everyone,

I just picked up a two-channel tube preamp to run into my interface. The preamp is this and the interface is this (2nd gen). Not that it matters, but I'll be replacing the stock tubes with nicer ones as soon as they get to me.

I have it all up and running, and it sounds great, but I'm not sure if I have something to worry about. The Scarlett of course has phantom power for its mic inputs, but they're grouped into 1-4 and 5-8 with no further separation.

My concern is turning on the phantom power at an input that is connect to the output of my preamp. Will I blow anything up/break anything? I haven't been able to find a definitive answer for this specific question, and I know there are some knowledgeable people that hang out here!

Thus far I've used the phantom power on the preamp to power my condenser. Is it possible to use the interface's phantom power? If so, does it matter which one I use? What happens if both are on at the same time?

Any information is appreciated. Thanks in advance!

[QVprod]

Do not use the interface's phantom power. use the phantom power on the preamp. If you're connecting the preamp to the interface with an xlr cable, phantom power may damage your preamp. However, if using a 1/4" cable phantom power should not affect it as the interface will treat it as a line input.

If you want to be extra safe however try to keep phantom power off on 1-4 and use 5-8 for any additional condenser mics you may be recording with.

[MikeMcKew]

Do not use the interface's phantom power. use the phantom power on the preamp. If you're connecting the preamp to the interface with an xlr cable, phantom power may damage your preamp. However, if using a 1/4" cable phantom power should not affect it as the interface will treat it as a line input.

If you want to be extra safe however try to keep phantom power off on 1-4 and use 5-8 for any additional condenser mics you may be recording with.

Thanks! That's kinda what I figured, but I wanted to be absolutely sure. Now I'll just need to get two more channels of outboard gear so I can just use a bank of inputs for those.

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[MarkTarlton]

I never hook up an external preamp via xlr to a consumer grade interface, or you are going through another mic preamp(BAD)...use a line in via 1/4" in this case!!

[MikeMcKew]

I never hook up an external preamp via xlr to a consumer grade interface, or you are going through another mic preamp(BAD)...use a line in via 1/4" in this case!!

Good call on using TRS cables, I'll have to pick some up. Would it be safe to run phantom power through the interface in that case?

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[selig]

I never hook up an external preamp via xlr to a consumer grade interface, or you are going through another mic preamp(BAD)...use a line in via 1/4" in this case!!

Good call on using TRS cables, I'll have to pick some up. Would it be safe to run phantom power through the interface in that case?

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Just turn off phantom power on the interface, and leave if off! The main risk is for ribbon microphones, so it's probably not going to hurt anything - but why even think about it!

[MikeMcKew]

Fair enough. I'm just thinking since the interface provides phantom power in groups of four, and the preamp only takes up two inputs. So if I needed to run phantom power to a condenser on the other two inputs on that bank, I could run into an issue.

Probably an oddly specific situation to worry about, but I like to be sure about how my gear works.

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[MikeMcKew]

Good call on using TRS cables, I'll have to pick some up. Would it be safe to run phantom power through the interface in that case?

Sent from my Pixel XL using Tapatalk

Just turn off phantom power on the interface, and leave if off! The main risk is for ribbon microphones, so it's probably not going to hurt anything - but why even think about it!

Oops, meant to reply to this post. See above!

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[MarkTarlton]

Good call on using TRS cables, I'll have to pick some up. Would it be safe to run phantom power through the interface in that case?

Sent from my Pixel XL using Tapatalk

Just turn off phantom power on the interface, and leave if off! The main risk is for ribbon microphones, so it's probably not going to hurt anything - but why even think about it!

so you would send a mic pre into another mic pre? that is weird to me. I would definitely try 1/4" line in bypassing the mic pre and gain stage.

[selig]

Fair enough. I'm just thinking since the interface provides phantom power in groups of four, and the preamp only takes up two inputs. So if I needed to run phantom power to a condenser on the other two inputs on that bank, I could run into an issue.

Probably an oddly specific situation to worry about, but I like to be sure about how my gear works.

Sent from my Pixel XL using Tapatalk

OK, I understand now - shouldn't be a problem as phantom power is designed to not harm anything that doesn't use it. In fact, it doesn't actually harm ribbon microphones if applied after connected. The are cases where there CAN be a problem, such as with TRS patch bays. But since ribbons are not fun to replace, most folks take a "better safe than sorry" approach and simply avoid the issue entirely.

Read more about the subject here, if interested, for a full description of the issues of phantom power and ribbon microphones:
http://royerlabs.com/ribbon-mics-and-phantom-power/

Also worth noting, there actually are ribbon microphones that REQUIRE phantom power (see the above link). With those you simply make sure to turn OFF phantom power before connecting/disconnecting the cables. I would imaging the same thing would apply in your case - turn off phantom power then connecting/disconnecting cables, and only turn it back on once everything is connected.

[MikeMcKew]

Gotcha, thanks for the info and the link. Good to know, I actually am planning on picking up a ribbon mic shortly so this will be relevant!

Fair enough. I'm just thinking since the interface provides phantom power in groups of four, and the preamp only takes up two inputs. So if I needed to run phantom power to a condenser on the other two inputs on that bank, I could run into an issue.

Probably an oddly specific situation to worry about, but I like to be sure about how my gear works.

Sent from my Pixel XL using Tapatalk

OK, I understand now - shouldn't be a problem as phantom power is designed to not harm anything that doesn't use it. In fact, it doesn't actually harm ribbon microphones if applied after connected. The are cases where there CAN be a problem, such as with TRS patch bays. But since ribbons are not fun to replace, most folks take a "better safe than sorry" approach and simply avoid the issue entirely.

Read more about the subject here, if interested, for a full description of the issues of phantom power and ribbon microphones:
http://royerlabs.com/ribbon-mics-and-phantom-power/

Also worth noting, there actually are ribbon microphones that REQUIRE phantom power (see the above link). With those you simply make sure to turn OFF phantom power before connecting/disconnecting the cables. I would imaging the same thing would apply in your case - turn off phantom power then connecting/disconnecting cables, and only turn it back on once everything is connected.

[skie]

Gotcha, thanks for the info and the link. Good to know, I actually am planning on picking up a ribbon mic shortly so this will be relevant!

OK, I understand now - shouldn't be a problem as phantom power is designed to not harm anything that doesn't use it. In fact, it doesn't actually harm ribbon microphones if applied after connected. The are cases where there CAN be a problem, such as with TRS patch bays. But since ribbons are not fun to replace, most folks take a "better safe than sorry" approach and simply avoid the issue entirely.

Read more about the subject here, if interested, for a full description of the issues of phantom power and ribbon microphones:
http://royerlabs.com/ribbon-mics-and-phantom-power/

Also worth noting, there actually are ribbon microphones that REQUIRE phantom power (see the above link). With those you simply make sure to turn OFF phantom power before connecting/disconnecting the cables. I would imaging the same thing would apply in your case - turn off phantom power then connecting/disconnecting cables, and only turn it back on once everything is connected.

I was told by Focusrite that the safest thing to do is run your preamp into input 1 or 2 with a 1/4" TRS plug, because you bypass any possibility of damage this way. I no longer have the email unfortunately.

[MikeMcKew]

Great, thanks for that. I'm still thinking of emailing both Focusrite and ART about this specific question, even with the great discussion here. Always best to hear it from the manufacturer's mouth.

Gotcha, thanks for the info and the link. Good to know, I actually am planning on picking up a ribbon mic shortly so this will be relevant!

I was told by Focusrite that the safest thing to do is run your preamp into input 1 or 2 with a 1/4" TRS plug, because you bypass any possibility of damage this way. I no longer have the email unfortunately.