GAP Pre-73 volume...WTH

aaronmcoleman

aaronmcoleman

The truth is out there!
Ok, I've used a GAP pre-73 for over a year now and loved it.

It has a 1/4" and an XLR output. I've always used a balanced 1/4". I finally got around to making some extra short XLR cables and using that for the output so today I started using the XLR out.

With my SM7B I had the output maxed and mic/line at -60 using the 1/4" TRS out. With the XLR I can cut the output to less that 25% and get the same volume. Does this make sense...why? shouldn't TRS and XLR have the same output?
 
The outputs might be the same but there's a variety of outcomes depending on the receiving hardware. Is the XLR going into a mic input or a line level input? Is the 1/4" output transformer, electronically or impedance balanced? Was the 1/4" output connected to a balanced input or an unbalanced one?
 
What interface are you going into? Does it have unbalanced jack inputs, because that might explain it.
Are the XLR and jack inputs on the interface both (the same) line level.

If that's not it, there's mention in the manual of a jumper which alters the output impedance, but I don't know if it effects XLR and JACK outputs equally.
It might be worth investigating.
 
Oh, that makes sense...

I use a Focusrite Saffire Pro 40. The jacks are those ones with the 1/4" inside the XLR. To get the 1/4" up to level I have the volume knob turned up to 4 (that's what is supposedly line level...or 0 or whatever...I don't know the terminology and want to learn all that).

So maybe the XLR are balanced and the 1/4" are unbalanced even though it's the same jack? That would mean with 1/4" I have to turn it up to 4 to get to (whatever that term is) and with XLR I can probably leave it at 0? Does balanced vs. unbalanced make a volume difference like that?

Does that make sense? Help me out with the terminology so I don't sound like an idiot next time :)
 
I'll try the TRS 1/4" cable with the volume at 4 like usual. Then the XLR with the volume at 0 and they should be the same if I'm thinking correctly.

Thanks!
 
The 1/4" in on the Focusrite is balanced. But the mic input (XLR) gets more gain than the line input. It's in the specs in the manual.

Paul
 
Steenamaroo said:
^^ That's the one.
You don't want to use XLR-XLR with your current gear.
Click to expand...

Wait, just when I thought I was getting it...why not?

With the 1/4" line level I have to turn the volume on the focusrite preamp up to 4 to get it to the same volume as mic level...so with XLR-XLR I can leave the focusrite at 0 and have even less noise...right?
 
aaronmcoleman said:
Wait, just when I thought I was getting it...why not?

With the 1/4" line level I have to turn the volume on the focusrite preamp up to 4 to get it to the same volume as mic level...so with XLR-XLR I can leave the focusrite at 0 and have even less noise...right?
Click to expand...

Do whatever works. Pay attention to noise levels. They're bound to be higher one way or another.

People may say it's bad going from one mic pre to another, but really the line input on many preamps is just padded down and fed to the same circuit as the mic input.
 
bouldersoundguy said:
Do whatever works. Pay attention to noise levels. They're bound to be higher one way or another.

People may say it's bad going from one mic pre to another, but really the line input on many preamps is just padded down and fed to the same circuit as the mic input.
Click to expand...

That's true, but I think padded down is the important part of what you said.
According to wiki, "A typical line out connection has an output impedance from 100 to 600Ω", and a mic input usually expects to see up to 250Ω or so, so with that in mind, line out to mic in may not be a good fit.


Keeping it simple and making generalisations though, a mic input wants to see a mic.
A line level input wants to see a line level output.

You're running a line level output into a mic level input, and amplifying your signal twice.

Personally, I'd just stick to the TRS cable. There should be zero difference between your XLR and TRS out anyway, unless there's something funky going on with the pre73.
 
Ok, I think I'm getting it. I should use the 1/4" because it doesn't go through the mic pre on my interface...right? XLR will go through the mic pre...right?

With the XLR I'd be amplifying the signal twice as Steen said...right?
 
I'll test it out both ways in a few minutes and report back.

Why is this stuff so complicated? haha...maybe it's not, maybe my brain just isn't complicated enough.
 
Yeah, according to the manual (which aaroncoleman doesn't read :p) the mic inputs (XLR) have gain ranging from +10dB to +55dB, whereas the line input (using the 1/4" part of the combo input sockets) provide gain from -10dB to +36dB (with the line/instrument switch in the LINE position).

ANALOGUE INPUTS
• Mic / Line inputs on XLR Combo with auto-switching between XLR and TRS.
• Mic / Line / Instrument 1 & 2: 2 x XLR Combo on front panel.
• Mic / Line 3-8: 6 x XLR Combo.
• Instrument: As above, switched to Instrument (inputs 1 & 2 only).
• Mic Gain: +10dB to + 55dB.
• Line 1-8 Gain: -10dB to +36dB.
• Instrument Gain: +10dB to +55dB.
Click to expand...

The mic input will, most likely, have lower impedance than the line input.

Unless I have misinterpreted the specs, the XLR input provides 20dB greater gain than the Line input.

Which is better? Let the ears decide.

Paul
 
PRHunt said:
Which is better? Let the ears decide.
Click to expand...

Exactly, which is better? To my ears they sound the same. With the XLR I leave the interface at 0, with the 1/4" I have it at 4. That's the only difference to me. It sounds the same. So I don't know. I think I'm just going to roll with the 1/4" since that's what I've always used and it seems like the better choice based on the numbers...But I can't hear a difference in noise or tone or anything.
 
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