Music Man Stingray and Lectrosonics RF system
Hello. I'm posting this here as it will be January 6th before I can speak with someone at Lectrosonics about my issue. And they may not have heard of my situation while I think that someone here may have run into this and have an idea how to deal with it.
I own a Lectrosonics TM400 Digital Hybrid wireless system that I used with a measurement mic (Earthworks M20) wirelessly when measuring sound systems in concerts and/or installs. The system consists of the R400a receiver and the UH400TM transmitter (now replaced with an updated model, but it still serves the purpose very nicely). Since I've stared playing bass again, I'd like to use this system to go wireless with the bass. The Line 6 bass wireless systems aren't a good option at the moment because of the interference with other wifi operations both in the venues I work and for the other players when we begin to use a digital console where the players will be able to control their own mix via their iPhone/iPad.
My bass is a Music Man Stingray 5-string with the 3-band EQ preamp. It was made in early 1998 (#E00040).
The transmitter is equipped with a female XLR for its input, so I wired the appropriate XLR-to-1/4" cable to connect the bass to. I wired the XLR connector for unbalanced operation (pin 2 hot, pins 1 & 3 to the shield). Since the transmitter is equipped with a phantom power supply, I'm being extremely careful to turn the transmitter on before I connect the transmitter to the bass, insuring that it's in dynamic-mic mode so no phantom power is inadvertently sent to the preamp of the bass. I've seen unbalanced playback devices destroyed (not my doing!) because of phantom being on as it was connected to the console via unbalanced XLR to RCA adapters. It's not at all pretty.
Okay, I've taken the long way around to get to this point. I was comparing the TM400 system to the 1/4" cable with my bass rig. With the TM400 system, there's a noticeable attenuation of the lows starting at, I'm guessing around 100hZ, maybe higher, when compared to the sound of the wire. Increasing the low EQ control on the amp around 3dB makes up the difference nicely. Otherwise, the sound of the bass is nearly identical with either wire or wireless. I'm actually quite excited about the results. It sounds awesome and the RF quality is very robust. I'll go ahead and run with the unit under these circumstances.
Here, I'll go into the particulars of my trouble-shooting. The input impedance of the UH400 transmitter is 1k ohms (balanced input). I do not know the output impedance of the (unbalanced, naturally) Stingray 3-band EQ preamp. I've looked on the EB website and the Musicman.org website and I've not been able to find out the O/P impedance. Knowing this would help in my trouble-shooting. I did make another XLR-to-1/4" adapter for the bass and the transmitter with different wire and I'm seeing the same results. I wire up balanced-to-unbalanced adapters all the time and I've not run into this type of discrepancy before with the playback devices that we use. I know that buffering the output of the bass might help, but that's gonna be physically unwieldy between the bass and the transmitter that will be attached to my strap.
I'd appreciate any ideas with this situation. As I said, I'd be perfectly happy to use the wireless system as it is, because, it REALLY SOUNDS GOOD!
Sorry for the length of the post, trying to get the details out there.
I don't think this will work without some kind of impedance changing device, like a DI, between the bass and the UH input.
The UH series from Lectro are designed to plug onto the end of a handheld mic and are optimized for mic levels and impedances. The LF rolloff you are experiencing is from impedance mismatch. Your MM bass has a Low Z output (less than 1K ohms), but it is not designed to drive a mic input. It wants to see a line or instrument level input with an input Z of >10K ohms, preferably more than 100K ohms, not the 1K ohm mic in on the UH. It works, as you said, with EQ added to offset the rolloff, but the increased load on the MM pre may shorten the battery life by causing the pre to draw more current.
The Lectro LM series of transmitters, with the mini 5 pin XLR connectors, are more adaptable to a variety of input devices, and they even sell a specific cable for that series which has a buffer (essentially a DI) built into the connector, to use with musical instrument outputs. That cable is P/N MI33ARA or MI33AST, depending on whether you want a straight 1/4" or right-angle 1/4" connector.
This is my take on the situation from several years of working with various wireless systems as a TV audio guy. Lectro may say something different when you talk to them.
Larry, you are indeed The Man...:o))
You were exactly correct. The Lectro guys concur with your comments about the impedance mismatch. And they are filing away the info about higher battery drain on the active preamp of the bass. They hadn't thought about that, but they definitely see where it would be an issue.
I'm now getting prices on the UM400 and the SMV series, although the SMV series are a lot more expensive and have waaay more features than I would ever need (We use the SMV and the SMQV for our lapel mice at church and they are awesome).
Also, I'm glad you mentioned the MI33 cable. Lectro recommended the MI39 cable, but upon further reading, I learned that the MI33 cable is more suitable for high-output instruments like my active Music Man (to Lectro's credit, I didn't tell them which instrument I was planning to use). That was a big help, too.
I so very much appreciate you taking the time to respond to this, Larry. I'm headed in the right direction now and I hope to have the UM in my hands before too long (after, of course, my account recovers from buying that EBS Fafner bass head from Ebay this morning. It kinda popped up a couple of days ago and I've wanted one of those for a very long time. Too good a deal to pass up.
Thanx again and take care, Larry.
You're welcome, Geri, and good luck with the Lectro gear. They make good sounding, hardy, reliable stuff, so once you find the right setup, it should last a long time.
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