Balanced / Unbalanced Mystery

[inverseroom]

I was having some trouble with my Hamptone pre last week--stuff that I was DI'ing through it, synthesizers specifically, sounded brittle and distorted. The mic inputs were perfectly fine, and so, oddly, was my Wurlitzer EP through the DI inputs. So, after writing to Scott Hampton about it (he didn't understand what the problem could be, since the DI signal path is the same as that of the mic signal), I took an hour to troubleshoot.

Basically, my studio is pretty lo-fi. I run everything unbalanced through a Behringer patchbay, and since it's only a couple of feet of cable here and there, everything still sounds good. Anyway, what I discovered is this. If I take an unbalanced signal, say from the synths, run it into the Hamptone, then run XLR's directly from the Hamptone into my hard disk recorder, the resulting sound is full-spectrum and sounds excellent. However when I go from Hamptone > XLR-to-TRS adapter cable > unbalanced patchbay > HD recorder, it's brittle and trashy.

But here's the weird part. If I go Hamptone > XLR-to-TRS cable > unbalanced patchbay > Pro VLA compressor > unbalanced patchbay > HD recorder, it sounds great again. This is true EVEN IF THE COMPRESSION ITSELF IS BEING BYPASSED.

So something about the compressor hardware restores the full spectrum of the sound. This is why the Wurli sounded good--I was compressing it. I suppose the Pro VLA is a balanced piece of gear, but how could this PUT BACK something that went missing before? Perhaps some polarity reversal is going on? A grounding issue is resolved?

Furthermore, I have no idea why this same lo-fi signal path didn't degrade the signal from a microphone...maybe because it was originally a balanced input, unlike the synths? Again, I have no idea why this should make a difference, but it does. Anyway, I will just run everything through the Pro VLA from now on, compressed or not...and sometime over the long coming winter I'm going to switch over the whole studio to TRS and a balanced patchbay.

Meanwhile, can anyone explain this effect? I'm stumped.

[vvv]

Dirty connections or a wiring problem in the patchbay is possible.

Is the compressor adding level?

[inverseroom]

It's not dirty connections--I'm putting the post-compressor signal through the exact same patchbay jacks as I did the compressor-free signal! And it isn't a question of adding level either...I got everything all unity'ed up for the sake of testing. The difference is not in level but in the quality of the sound...brittle and breaking up (and not in a good way) versus full-spectrum. It's like the difference between AM and FM radio.

[inverseroom]

Got an email from Scott...

If you are running into an unbalanced input, you need to ground pin 3 of the output. Likewise if you are coming from a balanced source, it is usually necessary to ground pin3, or the ring of a TRS. The micpre DI jack is not balanced, you cannot put a balanced signal into it, it must be TS...The bal unbal thing is confusing, especially now that there is a ton of consumer gear that is really not designed in a way that always works with true transformer balanced equipment. The thing to remember is you can short pin 3 of either the input, or the output of the micpre, and it works fine, its just unbalanced. If you leave pin3 open on the output (like some adapter cables are wired), it will sound tinny, with very low output, because the transformer is not completely connected.

I think I'm starting to get it.

[Professor]

Well that does help to make sense of the problem. I was trying to think of how the shorting of negative to ground would have screwed up the sound, but I suppose it would make sense if your patchbay is not actually shorting the connections.
So is this an unbalanced, TS patchbay with 1/4" jacks on both sides or is it a balanced TRS bay that just has a lot of your old TS cables running to the gear?

-Jeremy

[Cyan421]

Oh man. You will be so happy when you switch to ballanced pachbays. The studio i was at before made that switch when we "went office space" on the ADAT's (not literally). When the last of the unballanced gear when out the door (adats, behringer pachbays) all was better. Signals were better. The big thing was that the computers outputs were hotter comming into the console because there was no signal loss at the patchbay (in conversion of balanced to unbalanced).

[inverseroom]

Well that does help to make sense of the problem. I was trying to think of how the shorting of negative to ground would have screwed up the sound, but I suppose it would make sense if your patchbay is not actually shorting the connections.
So is this an unbalanced, TS patchbay with 1/4" jacks on both sides or is it a balanced TRS bay that just has a lot of your old TS cables running to the gear?

-Jeremy

It's a TS patchbay, AND TS cables. Yuck. Honestly, it all sounds fine, but the TRS upgrade is a long time coming. I'll have an order in to Redco soon & will spend some winter afternoon inhaling solder fumes.

[CarryTheZero]

Not to hijack the thread but I have a similiar question. It is my understanding that the FMR Audio RNC has unbalanced inputs and outputs. I have owned one now for almost a year and I always run balanced signals into it using TRS cables and run TRS cables out of it into other balanced inputs. Thus far I don't notice a problem as everything sounds fine. Am I experiencing some irregularity or is this normal? I'm lazy so I never bothered to try to go from -10 to +4 but shouldn't I use or do something to convert the signal?

[inverseroom]

I've got an FMR and it sounds fine with balanced gear. As I'm reading Scott's comments above, the problem can come in using TS cables with balanced gear, rather than the opposite.

[Professor]

It's a TS patchbay, AND TS cables. Yuck. Honestly, it all sounds fine, but the TRS upgrade is a long time coming. I'll have an order in to Redco soon & will spend some winter afternoon inhaling solder fumes.

Making the switch will likely help although you may still have some unbalanced gear mixed in, so it may turn up again.
Since the patchbay is unbalance, I'd figure that inside of it there are a bunch of those plastic chassis-mount 1/4" plugs with only two of the three metal tabs, the one for tip and sleeve. The likely culprit for your problem would be a balanced cable that has sneaked in there somewhere, probably between the mic preamp and the patchbay, perhaps an XLR-F to 1/4" TRS cable? If that is run out to the patchbay which only has the tip and sleeve tabs on the connectors, then that ring and sleeve short will never happen.
I'm a bit confused still at how that might be remedied when you run to the compressor, unless something is repatched in a way that does end up shorting those connections. Unless the preamp-to-patchbay cable is pulled and plugged into a different connection, I can't figure how it would short. Unless the plug the preamp is in on the bay just happens to be a TRS jack, that is normalled to a TS for the recorder, but the act of inserting of TS patch cable to route to the compressor completes the necessary short. But that can only happen if that third pin is present on that particular jack.
Weird.
Recording would be so much easier if it weren't for electricity.

-Jeremy

[inverseroom]

The likely culprit for your problem would be a balanced cable that has sneaked in there somewhere, probably between the mic preamp and the patchbay, perhaps an XLR-F to 1/4" TRS cable?

I may not have made myself clear above, but that's precisely what I'm running from the Hamptone into the TS patchbay...but it IS weird that this doesn't happen with mic signal, and compressors fixes the DI.

Go figure!

[Scodiddly]

Transfomer-balanced stuff is pretty rare nowadays - you have to make sure that both connections to the transfomer go somewhere to make it work. So if you're going unbalanced, ground the other pin of the XLR just as Scott (Hampton) said.

[inverseroom]

Transfomer-balanced stuff is pretty rare nowadays - you have to make sure that both connections to the transfomer go somewhere to make it work. So if you're going unbalanced, ground the other pin of the XLR just as Scott (Hampton) said.

In other words, the Hamptone's too good for me.

You made it to Chicago safely Scott?

[msmith4060]

Not too good...Just floating...

You are worth it....As Loreal says...

[Scodiddly]

Transfomer-balanced stuff is pretty rare nowadays - you have to make sure that both connections to the transfomer go somewhere to make it work. So if you're going unbalanced, ground the other pin of the XLR just as Scott (Hampton) said.

In other words, the Hamptone's too good for me.

You made it to Chicago safely Scott?

Yup - finally got internet into my apartment yesterday evening, so I can hang out here a bit more often.