Chase RLC-1 Preamp

[Otto]

Really a question for Wayne, but I'll post here for all to see.

I'm thinking of getting a new preamp that might not easily allow me to adjust the sub level. I'm using a balanced cable from my preamp to my sub right now. I want something like the RLC-1, but it's only got single-ended inputs and outputs.

Do you see any reason that I couldn't split out the two "hot" lines of the balanced cable to RCA plugs and send them into the RLC-1? At the output side, I'll just do the reverse, and recombine the "normal" and "inverted" signals to the single XLR cable.

Unless the two signal paths in the RLC-1 (for L and R) are separated such that I don't get common noise in the separated-but-balanced signal, I think I should be OK. I'd assume that the RLC-1 is quiet enough as to not introduce a significant amount of noise into the signal path, unless an experienced user says otherwise.

I think this would work. Comments?

[Wayne A. Pflughaupt]

I can’t think of any good reason why it wouldn’t work. As far as I know, about the only way you can “unbalance” a balanced signal is to short one of the signal leads (typically the [-] ) to the shield. The left and right channels of a stereo component are discreet, so you can send the balanced (+) through one and the (-) through the other, so I can’t see why the signal wouldn’t remain balanced.

I don’t see noise as a factor, unless your new pre amp happens to be significantly quieter than the RLC-1. A balanced output isn’t inherently quieter than an unbalanced – that’ll depend on the S/N ratios of the components in question. (A unbalanced signal’s main advantage is that it remains quieter over a long cable run.) Besides, even if there is some noise increase due to the Chase, this is a subwoofer signal, so it won’t be audible.

brucek is better at this kind of stuff than I am – maybe he can comment.

Regards,
Wayne

[F1 fan]

Otto wrote:

t do the reverse, and recombine the "normal" and "inverted" signals to the single XLR cable.

If you have one channel going into the sub on the + and the other on the - pin of the XLR then they will be out of phase would they not?
edit :they are in phase until they are at the input stage of the sub which may invert the signal on the - pin.

[Otto]

Thanks Wayne.

F1,

I'm going balanced out of my preamp to the BFD to the EP2500, so all is balanced. I think it will be OK.

[Otto]

Well, I was able to find a Chase Technologies RLC-1 on Craigslist in California somewhere. While I usually think of Craigslist as a good place to buy things locally, I contacted the seller and asked about shipping. "No problem," he said. After some delays, I was able to get it for $65 shipped. Not a great price, but not bad either, for this somewhat rare device.

I got the idea to use the RLC-1 as a sub level control from Wayne, of course. It's perfect for controlling sub volume after the processing stage that includes the Behringer BFD 1124P. Also, some preamps, mine included, don't make it easy to change the sub's output level on the fly. Additionally, I intend to supply the sub with an optional L/R signal, so there would effectively be no way to control that level with respect to the mains, as I'll essentially be feeding it the same signal as the mains themselves.

Anyway, here's a picture of the device in question:

05-ChaseRLC1.JPG

As described elsewhere, it's basically a remote controlled preamp, and that's all I'm using it for. One in, one out, and all I care about is controlling volume.

My initial question in this thread was "will it work with a balanced connection?" Well, the RLC-1 doesn't normally accept balanced inputs; it offers only single-ended RCA jacks. Since I'm only interested in using a mono, but balanced, sub channel, I figured that I could just break pins 2 and 3 of the XLR connector to RCA L/R plugs that I can then send to the RLC-1. Likewise, at the output, I will recombine those L/R RCA plugs back to a single XLR that will then head to my sub. The sub run is probably 20+ feet, so I like to use the balanced cable.

So I took a one meter balanced cable and cut it in half:

01-BalancedCableCutInHalf.JPG

Here's my workspace. Not 100% ideal, but could be worse. Actually, I could really use a small vise to hold things while I'm working; I'll pick one up the next time I order from PartsExpress. The WhiteHawk IPA helps keep things smooth...

02-Workspace.JPG

Basically, I just broke out all the wires from the balanced cable, and made the approprate connections to the RCA cable. Sorry no pics of that, guess I was busy working along...

Here's a closeup of one of the cables:

04-BalancedBreakoutCloseup.JPG

And here are both the "in" and the "out" cable adapters:

03-BalancedBreakoutPairComplete.JPG

I hooked the adapters to the RLC-1, and then on out to the sub amp, and everything works fine! The user interface to the RLC-1 is pretty simple, so I'll have to get used to that, but it sure will be nice to be able to adjust the sub's level without going through the preamp's menus.

The final connection path goes something like this:

Cary Audio Cinema 11 Subwoofer Output -> BFD -> RLC-1 -> Behringer EP2500 amp -> IB Sub Drivers.

The red "->" indicates where these adapters are located.

I'm very happy with the result!

Next steps:

My preamp does not offer a signal at the subwoofer output when used to listen to 2-channel audio with the mains set to "full range" (and definitely not when in "bypass" mode). So, if I want any subwoofer augmentation when listening to 2-channel music, I need to figure out a way to get a signal to the sub when listening in that configuration.

My current thinking is that I will use my currently-unused L/R main balanced outputs. To get these to be a single mono signal, I will send them through a small two-channel mixer. That will then be fed to the "other" channel of the BFD, the one that's currently unused. I will set that BFD channel's filter as desired for two-channel listening. That output of the BFD will then feed into another input on the RLC-1. This will allow me to access two completely different sets of filters (one for movies, and one for music) from the BFD without any cable switching or anything else. Of course, I also get the remote volume control for the sub in all cases. Recommendations for a small, quality mixer are welcome!

That's it!

[F1 fan]

Maybe I missed it but won't you also need a low pass filter for 2 channel mode as well as a summing circuit to combine the L&R signals?That Chase is the cats meow for sub volume adjustment.

[Otto]

Yep, the mixer will be used to combine the L & R main outputs to a single, mono signal.

From there, I'll do the LPF with the BFD. I had it set up that way (for the BFD to do the LPF) before when I was using "bypass" mode with my Outlaw 990 preamp. In "bypass" mode, the 990 just sent a copy of L/R summed to the sub out, so it was doing the job of the mixer. My new preamp doesn't do that, though I have asked the manufacturer to consider putting it in a future firmware change (assuming they could do it in FW).

Thanks!

[F1 fan]

All you need to sum the L&R channels is a single op-amp and a few resistors.If you where feeling adventurous you could possibly just add it into the chase unit and get the appropriate power supply voltages from it.

[Otto]

I've considered making a little summer, but ended up thinking of using a little two channel mixer. Any suggestions for something like that?

[Wayne A. Pflughaupt]

Nice job on the cables, Otto!

Recommendations for a small, quality mixer are welcome!

Mackie, Behringer, Alesis, Soundcraft, Peavey. Be careful, though – some mini mixers don’t have balanced outputs. Check the specs before you buy. Alternately, you might consider one of these.

All you need to sum the L&R channels is a single op-amp and a few resistors. If you where feeling adventurous you could possibly just add it into the chase unit and get the appropriate power supply voltages from it.

Hmm... If you do that, it will probably nuke the two-channel separation Otto needs to maintain his balanced signal.

Regards,
Wayne

[F1 fan]

I don't know of any mixer but this gentleman is soon to be selling this hi pass filter kit.With a few slight changes it could work as a summer.It also has Balanced output capability and you can experiment with different hi pass filtering for your IB.Anyway just an option. see post #11 for the schematic.http://www.avsforum.com/avs-vb/showthread.php?t=867340

[Otto]

Hi guys,

Any reason why this would be a poor choice? I like that passive device you linked, Wayne, but I don't like its 3 dB insertion loss. I think I'll be able to better match levels between my "stereo" mode (using an active mixer) and my "home theater" mode (using the sub out of the preamp) -- I think using a passive device might have me bouncing around sub trim levels more frequently.

Anyway, that's the one I'm considering; I think it's about $80.

[Wayne A. Pflughaupt]

I like that passive device you linked, Wayne, but I don't like its 3 dB insertion loss.

Well, that’s a necessary function of the volume controlling capability you said you wanted (1st and 5th posts), but maybe I misunderstood what your needs were.

Like any pre amp, the Chase is basically an attenuator, with full-open passing an input signal’s full voltage. Any setting below fully open is attenuating the signal – but you have to have that in order to turn the subs up via remote control. If needed, the Chase could be set for full open, if you leave it plugged in to an always-hot outlet and not switch its power cord, the latter of which I recommended if one wanted it to return to a reference setting upon system power-up (as I noted in that thread I opened about the Chase, once you adjust its volume it’s difficult to exactly return it back to where you started).

As to the Peavey, I’m sure there’s nothing wrong with it, if you believe it will fit your needs – which I’m not sure I fully understand at this point. If this is what you’re trying to accomplish...

My preamp does not offer a signal at the subwoofer output when used to listen to 2-channel audio with the mains set to "full range" (and definitely not when in "bypass" mode).

My current thinking is that I will use my currently-unused L/R main balanced outputs. To get these to be a single mono signal, I will send them through a small two-channel mixer. That will then be fed to the "other" channel of the BFD, the one that's currently unused.

...you could use the Peavey to combine the signal to mono, then send that signal to a separate input on the Chase, then switch between Chase inputs for music or movies.

Regards,
Wayne

[Otto]

Wayne A. Pflughaupt wrote:

Well, that’s a necessary function of the volume controlling capability you said you wanted (1st and 5th posts), but maybe I misunderstood what your needs were.

Like any pre amp, the Chase is basically an attenuator, with full-open passing an input signal’s full voltage.

Oh, I think we might have started talking about two different things... I'm talking about this thing. I'm OK with unity gain on the Chase, of couse, but the "Stick-On" combiner induces a 3 dB loss, over which I have no control. An active mixer will let me pretty much match the signal level between it and my Cary's sub pre-out (or otherwise get them such that I don't have to play around with the preamp's sub "trim" or the Chase's volume that much).

If needed, the Chase could be set for full open, if you leave it plugged in to an always-hot outlet and not switch its power cord, the latter of which I recommended if one wanted it to return to a reference setting upon system power-up (as I noted in that thread I opened about the Chase, once you adjust its volume it’s difficult to exactly return it back to where you started).

Yeah, I've thought about that. I think the manual states that its default level (i.e., after a hard power cycle) is -20 dB. I can certainly leave it on all the time, but time will tell exactly how it gets used.

if you believe it will fit your needs – which I’m not sure I fully understand at this point. If this is what you’re trying to accomplish...

...you could use the Peavey to combine the signal to mono, then send that signal to a separate input on the Chase, then switch between Chase inputs for music or movies.

That's exactly right!!! I'm looking for a signal I can feed to my sub when listening to 2-channel (during which there's no signal at the "subwoofer" preamp output). The other piece of the plan is to send it through the unused channel on my BFD -- to be equalized for music, where the other half is equalized for movies (house curve, LPF, whatever). I'm not really that lazy, but I am somewhat excited to be able to apply the different filter schemes remotely. And of course, I will now be able to run a sub with 2-channel listening, which I currently cannot.

Sorry if I wasn't clear previously, but I think you've got it right.

Looks like I picked up your font!

All the best!

[Wayne A. Pflughaupt]

Otto wrote:

Oh, I think we might have started talking about two different things... I'm talking about this thing. I'm OK with unity gain on the Chase, of couse, but the "Stick-On" combiner induces a 3 dB loss, over which I have no control.

Ah yes, I’d forgotten about that little bugger! I didn’t notice that it had a 3 dB loss – probably because the resistors it uses for the summing.

Not that I’m finally on board – yes, I think that Peavey is the way to go.

Yeah, I've thought about that. I think the manual states that its default level (i.e., after a hard power cycle) is -20 dB. I can certainly leave it on all the time, but time will tell exactly how it gets used.

You don’t have to leave it on all the time. Plugged into an always-hot outlet, it will remember its settings when you turn it off - i.e., if you use the Chase’s remote’s power button. You could program your system remote's macro to switch the Chase on and off.

Looks like I picked up your font!

Sure looks like it! You should open up your “edit” box and take a look – there are font on/ font off commands for every freakin’ paragraph!

Regards,
Wayne