connection types

[baydariz]

hey, i've been doing home recording for a little while, but i've recently decided to get real gear instead of 'plug-ins' so forgive what might be lame questions.

anyway, i'm having trouble with a couple of things. mainly, my compressor/limiter (presonus CL-44) has balanced XLR ins and outs, and an unbalanced TRS jack with a button that is supposed to change it from "in" to "out". I've been able to use the TRS jack as an imput from my preamp, but when trying to use it as an output from the CL-44 to my digi001, i get a VERY weak signal that barely registers. I thought perhaps this is because it is an "unbalanced" output, or maybe because the digi001 has a regular 1/4" jack instead of TRS (isn't this just a stereo 1/4" cable)?

in an attempt to correct this, i bought XLR to 1/4" adapters that are supposed to correct the impedance and connected it to an XLR cable out of the balanced XLR output on the CL-44. this works great, except that the adapter is so big and heavy that it doesn't sit well in the jack and i have to jiggle it around to get it to work.

so, if i get an XLR to 1/4" cable, will this solve my problems? I was told that i might need an adapter to correct the impedance, which is why i didn't just do this to begin with. if this is the case, where can i get good cables for this?

any advice would be greatly appreciated!

b[a]y

 

[sjjohnston]

... anyway, i'm having trouble with a couple of things. mainly, my compressor/limiter (presonus CL-44) has balanced XLR ins and outs, and an unbalanced TRS jack with a button that is supposed to change it from "in" to "out"....

I'm taking a shot in the dark, since I don't have this box (or any Presonus stuff, for that matter). Nevertheless:

This is weird. I'm not saying it's wrong, it's just weird. First "unbalanced TRS" is strange. Ordinarily you'd use a TRS to send a balanced signal (or a stereo signal). For an unbalanced output, the "R" isn't needed. I don't think I've ever seen a box that uses the same jack for both input and output ... except an insert jack, which does also use a TRS. Are you sure that isn't an insert (or "insert-type") jack? If so, one or the other of the tip or ring would carry the output (usually the tip) and one would carry the input (usually the ring). But then, of course, that pesky button you mention wouldn't be there.

It may be a jack like the one on the RNC. It's not an insert jack, really -- it's not there to insert something into the RNC's signal path, it's there to facilitate inserting the RNC into someone else's signal path. Thus the tip goes to the main input (coming from the output of your mixer's insert jack) and the ring connects to the main output (and goes back to the input of your mixer's insert jack).

Still, that button confuses me.

I've been able to use the TRS jack as an imput from my preamp, but when trying to use it as an output from the CL-44 to my digi001, i get a VERY weak signal that barely registers.

This is sort of the result one might expect if it's a jack like the one on the RNC. If you connect a TS plug, the tip connects to the tip (in) of your box's jack. But the ring (out) of your box connects to the sleeve (ground) of a TS plug. If you connect a TRS plug and the digi 001's input is an unbalanced TS, the ring (out) of your box connects to the ring of the TRS plug, but at the other end it either is left hanging or contacts the digi's sleeve/ground. Whatever tiny signal you get (theoretically, you shouldn't get any) is crosstalk through the common ground or something.

I thought perhaps this is because it is an "unbalanced" output, or maybe because the digi001 has a regular 1/4" jack instead of TRS (isn't this just a stereo 1/4" cable)?

Yes, a 1/4" stereo jack/plug/cord is the same thing as a TRS jack/plug/cord.

in an attempt to correct this, i bought XLR to 1/4" adapters that are supposed to correct the impedance and connected it to an XLR cable out of the balanced XLR output on the CL-44.

I may be totally off base, but this sounds like starting down the wrong road. The adapter I think your describing is a sort of barrel-shaped transformer. This is really intended to go between a microphone and an input jack. The TRS end (probably says 600 ohms or something like that on it), takes the low-Z microphone output and runs it through a transformer to avoid the messed-up frequency response you get when you connect a microphone to an input with too high an impedance. You don't need or want this in the signal path: the output of your compressor fully expects (and wants!) to be plugged into a very high-Z input. (If you'll pardon the pathetic fallacy).

this works great, except that the adapter is so big and heavy that it doesn't sit well in the jack and i have to jiggle it around to get it to work.

The fact it works great suggest maybe I'm wrong, but that physically sounds like the microphone transformer I'm describing.

so, if i get an XLR to 1/4" cable, will this solve my problems? I was told that i might need an adapter to correct the impedance, which is why i didn't just do this to begin with. if this is the case, where can i get good cables for this?

You shouldn't need to correct any impedances. A preamp out should connect to the compressor input, and the compressor out should connect to an A/D converter input just fine.

The two obvious ways to go would be:

(i) Figure out how that TRS jack really works. If it is like the RNC's jack, you can use it with an insert cable. An insert cable (as you probably already know) has a TRS plug at one end and two TS plugs at the other. The T of the TRS goes to the T of one TS, and the R of the TRS goes to the T of the other TS. Figure out which is which (they should be labelled). Plug the TRS into the compressor. Plug the T plug into the preamp output. Plug the R plug into the digi001 input.

(ii) There are standard XLR-TS cables. There are also XLR-TRS cables. If you want to go this route, take a look at how the Presonus manual suggests connecting its balanced output to an unbalanced input. If you want to ground one leg of the output, you'll want a cable that connects the XLR's cold (-) output (pin 3, I think?) to ground (pin 2? or the sleeve of the TS). You can accomplish the same thing other ways. For example, plugging a standard TS plug into a TRS jack connects the R of the jack to the S/ground.

 

[baydariz]

thanks

hey sjjohnston, thanks for the detailed response!

as it turns out, my main problem is a bad jack on my digi001! of course, i was testing everything with that channel, so i thought the whole setup was wrong! arghhhh...

so last night i decided it would be a good idea to disassemble my digi001 and see if i could fix the jack (of course, not knowing how). i successfully disassembled it, but the 1/4" inputs are soldered into the board, so there wasn't much i could do. thankfully i was able to put it all back together! it works if i pull it out a little bit or jiggle it around, so i think it's just loose.

i'm going to try to return those XLR - 1/4" adapters, which are the ones you thought they were. the guy at the music store is the one that told me i would need them (and at $12 a pop!). he wasn't trying to rip me off, i just think he doesn't know what he's talking about.

as for the TRS output on the CL44, i misread the manual. it's switchable input/output in that you can change which connection it uses on the TRS cable, which of course would be a return or send. regardless, i couldn't get this to work into my digi, but that's ok, i'm just going to buy XLR - 1/4" cables.

while i have your attention, can you recommend a good patch bay? what i want to do is hook up my compressor/limiter to the patch bay, and into my digi001 from there, so i can put a gate in the signal patch if i need to use it for that track, or whatever other effects. i was eyeing up the Furman PB-48 Patch Bay ( http://www.musiciansfriend.com/srs7...5100652572/search/g=home/detail/base_id/73190 ) but i don't know if i should buy a better one?

thanks a ton!

b[a]y

 

[sjjohnston]

Re: thanks

... while i have your attention, can you recommend a good patch bay? ...

Patchbays, strange as it may sound, can be a bit of an emotional issue, and can provoke rather more gear-status-posturing and gear-status-feelings-of-inadequacy than you might think possible.
Here is my overly-elaborate thinking on patchbays. This is definitely in the "home recording" context.

First decision: Jacks on the back?

Real "professional" patchbays have jacks on the front (obviously), but the back is punch blocks or solder points or something like that. "Amateur" patchbays (for want of a better term) have jacks on the back. My opinion is that in the typical home recording set-up you'd rather have jacks on the back. Home recordists are, in my limited experience, prone to add and change gear (or just suddenly to rearrange racks and patchbays based on some newly-imagined theory of symmetry and elegance). Also, home recordists, compared to professional studios, are relatively free of interns and lackies who can be put to work soldering or stripping cables for hours at a time.

Consideration of this first decision rapidly expands into a consideration of the other differences between "pro" and "amateur" patchbays:

- Jack type. The pro 1/4" patchbays typically use the "long-frame" or "military" type jacks, rather than the 1/4" jacks we are familar with. The plugs on the patch cables look kind of like TRS plugs, but they have another bump around where the ring is. Whatever the virtues of long-frame jacks/plugs generally, I say we already have too many different types of connectors to deal with (TRS, TS, RCA, XLR, 1/8", Midi, DB25, Elco, BNC ...). If push comes to shove (which it often does in a home studio), you can patch something new right into your bay through the front jacks. You can even plug a guitar or a bass into the patchbay.

There are also "TT" patchbays which use "tiny telephone" jacks, typically arranged in neat pairs. These are sort of appealing because you can get more points in a rack space, though again you've got that "yet another type of connector" problem going.

- Sturdiness. If someone's spending thousands of dollars an hour to use your studio, engineers, session musicians, etc., and they get stymied by a faulty patchbay, that's a big problem (and they won't be mollified if you told them you saved $300 by using a cheaper patchbay). If a home recordist gets stopped by a faulty patchbay, he can work around it or -- if worse comes to worst -- go away and watch TV. Patch bays in pro studios may get used 12 (or more) hours a day, 6 or 7 days a week, by groups of people, some of whom are mad and don't own the equipment. They'd better be sturdy! A home recordists patchbay gets used lightly by the owner. If a jack is rated for a mean of 1,000,000 insertions before failure, 9,999,940 of them will just go to waste.

- Pro-ness. The pro ones win here. You'll never pass your setup off as a real "pro" rig in a photo in TapeOp with an amateur patchbay. Of course, your monitors on orange crates, absence of color-coordinated Auralex and the presence of names like "Alesis" and "Fostex" will probably give you away anyway.

- Price. The bottom line ultimately may become compelling. The price of "pro" patchbays runs about an order of magnitude higher than "amateur" patchbays.

Second decision: TS or TRS?

Even amateur "jacks on the back" patchbays come in two main flavors: TRS or TS. TRS patchbays give you the ability to send balanced lines through them. Whether this is of value depends on a consideration of how many balanced connections you actually have. You can also save patchpoints by sending stereo signals through a single TRS patchpoint. Theoretically, you could combine any two signals on a single TRS point, but I'd generally limit it to stereo signals that you're going to route as a pair (e.g. main mixer output to 2-track recorder).

Third decision: Normalling options

In my experience, you definitely want to be able to set individual jack pairs to different normalling schemes, and these should include at least half-normalled and "open" (open = top and bottom are never connected, even with no jacks in the front). And you want to be able to do this without clipping wires or soldering things. Ideally, you want to be able to do this without taking anything out of the rack.

The two basic schemes for doing this are rotating cards and switches. If you have rotating cards, you'd like to be able to remove them from the front without taking the bay out of the rack. If you have switches, you'd prefer to have them on the front.

Some Specifics

With all that considered, you can consider specific options. Hosa has some new patchbays with normal-switches on the front. While anything labelled "Hosa" will definitely take you out of the "pro" camp, you can always just put tape over the brandname.

Various manufacturers have flippable-card bays. I have Neutrik one where you can easily remove the front and flip cards (the front panel is only grabbed by one rack screw on each side, so if you remove those two you can get the faceplate off while the other two screws hold it in place). Unfortunately, it's seems sort of flimsily built, though it hasn't actually broken. The jacks are difficult to insert plugs into.

The only Behringer piece of gear I own is a patchbay. It's fairly sturdily built (lots of actual metal), but has the disadvantages of being TS and having the normalling switches on the top, where you can't get at them in rack. It's cheap, though! And that's not a bad thing.

I'd suggest looking at some actual products at a store before buying one, to see if the construction seems flimsy or hard to work with.