• jayn
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  • Registered: 2008-08-24
  • Posts: 8

Topic: dmc842 src vs mode2 questions

I've been using the 842 with 4 neumann mode 2 mics and about 30 feet of aes cable to each mic. with no issues.  I can also switch on src, and I can't detect any difference in the sound with these mics.

Is it really doing any sample rate conversion?  Do the mode 2 mics free run from an internal crystal when you turn on src, or is src just ignored?

Can RME provide any analysis for a choice between using SRC or using the mode 2 control?  I'm particularly interested in relative stability of the mode 2 control vs using SRC  as the cables get longer, as I am considering a setup with cables running 120 feet.

2 Reply by sf

  • sf
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  • Registered: 2007-05-20
  • Posts: 15

Re: dmc842 src vs mode2 questions

When the SRC is on, the mode 2 microphones continue to run on their vcxo.

You have a couple of possibilities to check, whether the SRC is working indeed:

1. Disable the sync pulses (SP) in the setup menu. You will notice that the sync LED starts blinking sooner or later (the frequencies will probably match quite well, so this may take a moment).

2. Disable the control pulses (CP) in the setup menu. This cuts all control data being sent to the microphone. If you now change the clock, e. g. from 48kHz to 44.1kHz, the microphone 'will not know'. You will notice ugly distortions and all will be fine again as soon as you activate the SRC.

Please don't forget to activate SP and CP again for your KMDs, as synchronous operation is really the way to go.

The transmission scheme for all data towards the microphone is very robust. The first thing which is going to happen, when cables get longer, is that the audio signal from the microphone will go away, first for quad frequency sampling rates, then for double speed and last for single speed.
If the SRC is deactivated and the sync LED is lit constantly, you are doing fine.

I hope this answers your questions and makes you feel comfortable when using this exciting new technology!

Kind regards,
Stephan Flock