Connecting MXL770 to PC

jbmolineux

New member
I'm trying to connect an MXL770 to my computer using an ART TubeMP Tube Microphone Preamp, plugged into the 3.5mm headphone jack on my docking station. I'm getting nothing! Please advise!

---------- Update ----------

(It's a PC running windows 10...)
 
Headphone jack? That would be for sound from the computer out to headphones or speakers, unless it si a combination headphone/microphone jack (4 conductor). What you really need is an audio interface that converts the audio to digital and connects to the computer via USB.
 
I meant 3.5mm microphone input (on docking station). I just tried purchasing a USB sound card, and that didn't work either. I am starting to suspect that the preamp may be faulty (had the same problem with a simple computer microphone that works). Is there an easy way to check that?
 
The ART TubeMP is a Mic preamp, so it outputs 'line-level'. So you shouldn't plug that into the microphone input.
That said, the microphone input should get a signal (although too loud and/or distorted).

If you have a line-in on your pc, use that. Or a line-input on your USB sound card, of course.
(Also, to exclude issues with the docking station, try to make it work first by connecting it to the pc directly.)

If you get nothing out of the preamp, regardless of input and output gain settings, chances are that you haven't enabled the 'P-Pwr' +48 volt phantom power that the condenser microphone needs to operate. (connect mic and turn down volumes/gains before switching it on..)

You could test the preamp by connecting the output to a hifi amp, headphone amp or mixing desk and see if you can get a signal out of the microphone.

Good luck!
 
I meant 3.5mm microphone input (on docking station). I just tried purchasing a USB sound card, and that didn't work either. I am starting to suspect that the preamp may be faulty (had the same problem with a simple computer microphone that works). Is there an easy way to check that?

- What USB sound card/interface (model/manufacturer)?
- What type of cables are you using to connect the mic to the preamp and the preamp to the USB interface? Mic to preamp should be XLR to XLR. The preamp to USB interface should most likely be TRS to TRS.
- Phantom power should be turned on on the preamp to power the microphone.
- Try plugging the mic into the USB interface directly with its phantom power on (don't use the preamp).

The preamp into the mic/line input of your computer can work, but the type of cable used is the key and not worth the hassle of doing it.
 
So, the USD soundcard is a cheap one that I bought in Kathmandu (where I live). It just says "3D sound" on it.

I was able to confirm (with other devices) that the following seem to be working:
*the "line in" on my computer (works with other mics)
*the cables (they are cheap and that may be an issue, but I at least should get something, right?) (I'm using XLR mic to preamp--tried 2 different cables--and XLW with a 3.5mm adaptor to (a) the line in on the PC, and (b) the USB sound card)
*the adapters
*I have tried all possible combinations of buttons, but definitely keeping the +48 volt phantom power on
*I've tried plugging the mic directly into the USB sound card and the line in (with the preamp)

All combinations result in zero sound from the mic. I also tried another (simple computer) mic with the preamp, and got nothing there. I also tried going directly from the preamp to headphones and a UE boom speaker, and nothing (not sure if that would work normally or not).

I also have limited access to the equipment mentioned (hifi amp, headphone amp or mixing desk) since I live in Kathmandu, and it's tough to get anything here (I had the mic and preamp brought over from the states). Is there anything else I can use to test?

Thanks for any help you can give!
 
If your "sound card" looks like the one below I can pretty much say that is your problem. It is not much different than plugging into your computers MIC/LINE jack. The XLR to 3.5mm cable will not work unless it is specially wired to 'convert' the balanced out of the preamp to an unbalanced connection into PC or the USB thingy if it does work at.

It may be possible to verify the mic works. The Tube MP has a green LED that shows it has power. That light turns red if the signal is too high to indicate clipping. Connect the mic using the XLR to XLR cable to the preamp and then turn on the Tube MP and phantom power. Turn the 'Input' knob full CCW to minimum gain and depress the button marked '+20dB Gain''. While speaking fairly loud into the mic, turn the Input gain knob up and see if you can get the 'Power/Clip=Red' light to come on. If it changes to red it shows that the mic is functioning and the preamp is getting signal.

Next thing to try in the bag of tricks if you have headphones with a 6.5mm plug or an 3.5mm to 6.5mm adapter. Plug the headphones into the 'Output' jack on the Tube MP and while speaking into the mic as above with the red light coming on, turn up the Output knob on the preamp. If you hear sound in the headphones the preamp should be working. The headphones may not have equal sound in each ear because the preamp output wasn't designed for stereo headphones, but will show that signal is going through the preamp.
(I just did this with an old ART Tube PAC preamp I have to prove to myself this test may work)

The cheapest USB interface to consider would be a Behringer UM2 ... https://www.amazon.com/Behringer-UM2-BEHRINGER-Black-1-Channel/dp/B00EK1OTZC

What software are you trying to record with or get the audio into? That can present problems also.
 

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That is indeed the USB "sound card" that I was able to find in the markets of Kathmandu.

I tried your experiment, and got no clipping. No red light. I tried it with two different chords.

What's my next move?

What software should I use? I was considering "N Track" (which I've used before), but what do you recommend for a PC?
 
That is indeed the USB "sound card" that I was able to find in the markets of Kathmandu.

I tried your experiment, and got no clipping. No red light. I tried it with two different chords.

What's my next move?

What software should I use? I was considering "N Track" (which I've used before), but what do you recommend for a PC?

If you have access to a 6.5mm to 6.5mm instrument/patch type phone cord, plug it into the preamp. Hold the tip of the open end of the plug and try the same checks I suggested for the mic looking for the red clip light or listening with headphones. Holding the tip of the plug should put a hum into the preamp like one might hear from a guitar cord plugged into an amp when the end is touched. If you get an indication from the light or hear hum in headphones it's possible the mic isn't working. If you don't see an indication from the light and don't hear something it could be the preamp.
You really need a proper USB interface such as the one I suggested in post #8. This would allow you to connect the mic to your computer without the preamp and would allow use of the preamp if you wanted to.
 
Doing this test I was able to get the red light clip. Is that sufficient to conclude that the problem is the mic? Is there anything to try but replacing it?

What software do you recommend?
 
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