Noisy headphone output on Sound Devices MixPre at DVinfo.net

Andre Theelen · July 5th, 2010, 04:14 PM

Hi all,

I recently bought a SD MixPre on eBay. When I tested it I found the headphones output rather noisy.
With the gain pots of both preamps at 0 and no mics connected, the noise became very apparent when the volume pot was over 30%. I would expect this to not be normal?
When turning the gain of the preamps up to 100% there was a barely noticeable increase in noise level, so my guess is the preamps are fine.
The high noise level is not recorded by the way, so it must be something in the headphones amp.
The limiter was off.

I use a Sony 7506 headphone for monitoring the audio.

I did some recording tests with a AT2035 and AT897 which went fine when I found the right recording levels on the MixPre and the Sony PCM-M10 I use as recorder. The MixPre TapeOut was connected to the M10 Line In.
I think the M10 does add a little noise to the recording, anyone has similar experiences?

Thanks,

Andre.

Steve House · July 5th, 2010, 04:22 PM

Testing for circuit noise with no mics connected at the inputs doesn't really tell you much. You need to short the inputs before the noise you hear in the phones really means anything.

SD has really good service ... if you think there's a problen a quivk trip back to the factory with get it tuned up for a reasonable fee. They cater to the working pro, a far cry from consumer grade service.

Vic Owen · July 5th, 2010, 05:36 PM

Andre--

I just did a quick check on my MixPre, with Sony 7506 headphones.

With the Mic gains at zero, I had no noise at any setting of the Phones volume - quiet all the way. With the Mic gains set at 12 o'clock, I could begin to hear some faint hiss at 1 o'clock on the volume. I did not try shorting the inputs, since I had no noise until I brought-up the Mic gains.

As Steve mentioned, I'd contact Sound Devices.

Cheers -

Andre Theelen · July 6th, 2010, 04:59 PM

Hi Steve, Vic,

Thank you both for your input.
There is a SD authorized service center in the Netherlands, so I'll check with them what they can do for me.

Regards, Andre.

Bob Hart · July 6th, 2010, 09:19 PM

Andre. It may be a whole lot easier than that.

With your phones on and a mic connected, move the "TAPE RTN" switch. You may have it set in the wrong position. I think it should be switched to the right when you are NOT returning audio in from the camera to the "TAPE RTN" socket.

If the switch is in the wrong position, you will hear audio but it will be a lower level with a high noise level. I experienced this when I first used the mixer.

Andre Theelen · July 7th, 2010, 09:56 AM

Hi Bob,

Thanks for your suggestion! That was the problem indeed!
The TAPE RTN switch was switched to the left and when I switched it to the middle position the noise disappeared and the mixer is working perfectly :)

Another stupid user error solved...

Cheers,

Andre.

Vic Owen · July 7th, 2010, 10:38 PM

Good on you, Bob! It never occurred to me to have Andre check that switch -- mine has never moved from its original position. Saves an unnecessary service call.

Cheers --

July 5th, 2010, 04:14 PM	#1
Andre Theelen Regular Crew Join Date: May 2007 Location: Netherlands Posts: 51	Noisy headphone output on Sound Devices MixPre Hi all, I recently bought a SD MixPre on eBay. When I tested it I found the headphones output rather noisy. With the gain pots of both preamps at 0 and no mics connected, the noise became very apparent when the volume pot was over 30%. I would expect this to not be normal? When turning the gain of the preamps up to 100% there was a barely noticeable increase in noise level, so my guess is the preamps are fine. The high noise level is not recorded by the way, so it must be something in the headphones amp. The limiter was off. I use a Sony 7506 headphone for monitoring the audio. I did some recording tests with a AT2035 and AT897 which went fine when I found the right recording levels on the MixPre and the Sony PCM-M10 I use as recorder. The MixPre TapeOut was connected to the M10 Line In. I think the M10 does add a little noise to the recording, anyone has similar experiences? Thanks, Andre.

July 5th, 2010, 04:22 PM	#2
Steve House Inner Circle Join Date: Mar 2005 Location: Hamilton, Ontario, Canada Posts: 5,742	Testing for circuit noise with no mics connected at the inputs doesn't really tell you much. You need to short the inputs before the noise you hear in the phones really means anything. SD has really good service ... if you think there's a problen a quivk trip back to the factory with get it tuned up for a reasonable fee. They cater to the working pro, a far cry from consumer grade service. __________________ Good news, Cousins! This week's chocolate ration is 15 grams!

July 5th, 2010, 05:36 PM	#3
Vic Owen Major Player Join Date: Dec 2001 Location: Seattle, WA Posts: 540	Andre-- I just did a quick check on my MixPre, with Sony 7506 headphones. With the Mic gains at zero, I had no noise at any setting of the Phones volume - quiet all the way. With the Mic gains set at 12 o'clock, I could begin to hear some faint hiss at 1 o'clock on the volume. I did not try shorting the inputs, since I had no noise until I brought-up the Mic gains. As Steve mentioned, I'd contact Sound Devices. Cheers - __________________ -- Vic Owen --

July 6th, 2010, 09:19 PM	#5
Bob Hart Inner Circle Join Date: Dec 2003 Location: PERTH. W.A. AUSTRALIA. Posts: 4,476	Andre. It may be a whole lot easier than that. With your phones on and a mic connected, move the "TAPE RTN" switch. You may have it set in the wrong position. I think it should be switched to the right when you are NOT returning audio in from the camera to the "TAPE RTN" socket. If the switch is in the wrong position, you will hear audio but it will be a lower level with a high noise level. I experienced this when I first used the mixer. Last edited by Bob Hart; July 6th, 2010 at 09:22 PM. Reason: error

July 7th, 2010, 10:38 PM	#7
Vic Owen Major Player Join Date: Dec 2001 Location: Seattle, WA Posts: 540	Good on you, Bob! It never occurred to me to have Andre check that switch -- mine has never moved from its original position. Saves an unnecessary service call. Cheers -- __________________ -- Vic Owen --

July 6th, 2010, 04:59 PM	#4
Andre Theelen Regular Crew Join Date: May 2007 Location: Netherlands Posts: 51	Hi Steve, Vic, Thank you both for your input. There is a SD authorized service center in the Netherlands, so I'll check with them what they can do for me. Regards, Andre.

July 7th, 2010, 09:56 AM	#6
Andre Theelen Regular Crew Join Date: May 2007 Location: Netherlands Posts: 51	Hi Bob, Thanks for your suggestion! That was the problem indeed! The TAPE RTN switch was switched to the left and when I switched it to the middle position the noise disappeared and the mixer is working perfectly :) Another stupid user error solved... Cheers, Andre.