Urgent Mixpad and Pro88W help...

[Matt Gabor]

Hi All,

I am preparing for a documentary shoot next week and am having a problem with some audio gear that I just purchased. I have searched these forums, Jay Rose's book, and Ty Ford's book, but been unable to solve this issue. I'm guessing it's my own audio ignorance.... maybe one of you can help me out.

I have a Samson Mixpad4 and two Audio-Technica Pro88W lavalier systems. For some reason, when I plug a lav receiver into the 1\4" input for channel 1 or channel 2 (both are mono) on the Mixpad I can't hear anything. I am able to hear audio from the lav receiver when it is plugged into the 1\4" input for channel 3L/4R (stereo), but it is really soft and crackles a lot.

Here is the troubleshooting I've done:

- Plugged my Senheiser ME66 into both the XLR and 1\4" inputs on channel 1 and 2. Both inputs and channels work fine. The ME66 is running on battery not phantom power. This tells me (I think) that the Mixpad is working.

- Plugged headphones into the "phone out" input on the PRO88W receiver and clearly hear audio from the PRO88W transmitter. This tells me (I think) that the lav system is working.

- The PRO88W lavs came with a 1\8" male to 1\8" male cable and a 1\8" to 1\4" adapter which I'm using to plug the receiver into the Mixpad. I have plugged an iPod into the Mixpad using the same cable + adapter and the ipod plays fine (Note: The audio sounds warped through the mono channels, but fine through the stereo channel. I assume this expected behavior). This tells me (I think) that the cable + adapter are working.

The one thing I haven't tried because I don't have the right connectors (Radioshack tomorrow) is plugging the PRO88W receiver into the XLR input and not the 1\4" input. Could this be the problem?

Any have any thoughts????

[Steve House]

Don't know anything about the Samson but as I read their online manual it appears the 1/4" inputs on the mono channels are expecting line level signals. Since the Pro88 appears to be intended to drive the aux mic input on consumer camcorders, I'll bet it's outputting at mic level. (AT doesn't post much info online about it, do they?)

Watch out for the Radio Shack adapters to make sure that the pins on the input connect to the right pins on the XLR. Couldn't find online manual for the PRO88 but is its output balanced or unbalanced, TRS or TS?

[Matt Gabor]

On the Mixpad both the 1\4" mono channel inputs and the 1\4" outputs are balanced TRS.

The PRO88w manual is not very helpful. It doesn't indicate if the output is line or mic. They do sell a cable for the receiver that has this description - "CP8306 transformer balanced microphone adapter cable can be purchased separately for use with equipment with XLRF-type balanced microphone inputs".

I'm guessing you're right about the mic vs. line level. The mono channel XLR input says MIC and the 1\4" input says LINE. I'm hoping that using balanced female 1\4" to male XLR adapter to plug into the MIC input will help boost the signal coming out of the PR088w receiver.

Thanks a lot for the help.

[Steve House]

Is the plug on the 1/8 cable from the Pro88 a TS or TRS plug?

[Douglas Spotted Eagle]

The Pro88 is a T/S plug, and the receiver outputs line or mic level.
You should be able to plug this straight into the 1/4 input using an adapter of channel one or two on your MixPad. Just tested it here on my Mixpad, no problem. You'll need a little gain.

[Steve House]

I wonder if he's using a stereo 1/8 to 1/4 adapter instead of a mono and that could have something to do with it?

[Douglas Spotted Eagle]

Originally Posted by Steve House

I wonder if he's using a stereo 1/8 to 1/4 adapter instead of a mono and that could have something to do with it?

That's a good catch, and a likely possiblity

[Matt Gabor]

Douglas - Thanks for testing my set up. It's relieving to know that it should be working... now I just have to sort out why it isn't.

Is there a way to tell if the 1/8 to 1/4 adapter that I'm using is stereo? The adapter came with the PRO88w so I assumed it would be fine.

I also just got back from Radioshack and purchased a transformer from 1/4 unbalanced to xlr balanced. About to test this out to see if it helps.

[Matt Gabor]

OK. Update... The 1/4 to XLR transformer seems to be working. I'm able hear audio on my monitors now. I do have to turn up the TRIM a bit in order to get a decent level, but it's good to know I can get something to work with.

For my own learning, I still would like to resolve the 1/4 input problem (especially since it works for Douglas). I'm going to do some research on the stereo vs. mono 1/8 to 1/4 adapter issue.

Also, since as Douglas says the PRO88w outputs both line and mic, would I get better audio by plugging into the 1/4 line or the XLR mic input?

[Steve House]

I would assume the adapter that came with the unit would be correct. Of course, one should never assume. And adapters are notorioulsy famous for bad or broken connections inside them.

DSE said that the receiver can output either mic or line level. You'll probably find that setting somewhere in the setup menus. Set it to line and try the 1/4 again.

The reason I've been asking about stereo/mono thing is the wiring of a adapter to connect a stereo plug into a mono input is tip-to-tip, ring-to-tip, and sleeve to sleeve - that connects the left and right signals together at the tip into one mono channel. But in TRS balanced, the tip is signal hot and the ring is signal cold. The stereo-to-mono adapter shorts them out and kills the signal. The correct wiring of a TRS balanced to TS unbalanced adapter is tip-to-tip, ring-to-sleeve (or unconnected), and sleeve-to-sleeve. To make things even more interesting, with some 1/4 or 1/8 inch TS plugs the tip extends back far enough to accidently come into contact with the ring slider when you put it into a TRS jack and shorting tip and ring together in the process.

[Douglas Spotted Eagle]

The receiver doesn't have menus, it's just two ouputs, one for mic and one for line. Use the mic output, the line output on these lil' wireless are noisy. Mostly there for monitoring or plugging into a home stereo, I'd think.
The output on the Pro88 is unbalanced. you need a mono, Tip/Sleeve adapter for your Pro88w output. If it's stereo, it will have two little plastic dividers in the connector, if it's mono, it will only have one.
FWIW, my "Instant Audio" book covers this fairly deeply. Run to Walmart :-) They've got it in the bigger stores. They might have the adapter you need too, but it's likely a Radio Shack thing.

[Matt Gabor]

Man, you guys are great. Your explanations of the mono/stereo and TRS/TS issues were very helpful. I am now getting audio through the Mixpad's 1/4 line input by using a mono TS 1/8" to 1/4" adapter! Thank you so much for the help. I hope, with time and continued learning, I will be able to pass on my knowledge to others as you have to me. Douglas - I don't have time today to get to Walmart and buy your book, but I certainly will. I know I have a lot to learn.

That being said, I have another question :-). There are now two ways I can input the lav receivers:

1) male 1/8 to male 1/8 cable from the receiver mic out into a TS 1/4 mono adapter which is plugged into the Mixpad's LINE input

2) male 1/8 to male 1/8 cable from the receiver mic out into a TS 1/4 mono adapter into a transformer from 1/4 unbalanced to XLR balanced which is plugged into the Mixpad's MIC input

Is there an advantage to going through the unbalanced to balanced transformer? To my ears it sounds marginally less noisy, but I'm still training my ears and can't tell if I'm imagining the difference.

I was just listening to the audio through monitors. Now I'm going to actually record some into my PD150 (using an attenuator to adjust from the Mixpad's +4dBu out to the PD150's -10dBv line input). We'll see how it goes...