cancel
Showing results for 
Search instead for 
Did you mean: 
cancel
Showing results for 
Search instead for 
Did you mean: 
DavidP-at-Bose
Member
  • 0
  • 69
  • 0
Registered since

Nov 19, 2008

PM input sensitivity and corresponding meters?

Changes in the input sensitivity, specifically analog inputs (I don't have a digital card handy to test it), do not result in a corresponding change in input level metering, but do ultimately result in a change at the output.

This seems to contradict the help file which states the meters are post A/D.

1. What is the expected/designed functionality?

2. Where are the input sensitivity settings actually taking place- pre or post A/D?

Thanks!
D.
5 REPLIES 5
DavidP-at-Bose
Member
  • 0
  • 69
  • 0
Registered since

Nov 19, 2008

Re: PM input sensitivity and corresponding meters?

Just want to bump this topic in case it got lost in the mix.

Also clarify where the confusion is coming in... for instance- switch between +4dBu and +12dBu sensitivity, no change in input meter dBFS reading. But switch between +12dBu and +24dBu and there is a change... worse yet not a 12dB change as one would possibly expect, instead something more like 7 or 8dB.

So clearly we are changing "headroom" or S/N ratio differently for different settings. Not necessarily an issue, just would like to know what they are.

Also, and more importantly, we need to visually show where the "0", or full output, point is on the input meter for each respective input sensitivity- since it changes. Without this reference there is no way to know where your input signal with respect to driving the amp to its full output (or into limiting as the case may be).
RobB-at-Bose
Collaborator
  • 10
  • 1056
  • 0
Registered since

Oct 6, 2008

Re: PM input sensitivity and corresponding meters?

Hi David,

Apologies for the delay in responding to you..

Your assumption is correct, the amount of "headroom" available varies with the input sensitivity and hence the metering isn't changing exactly as you might expect. The metering is correctly indicating the amount of headroom in the amplifier.

Your second point is also correct, there should really be some indication of where the signal should be to achieve full output. Without the headroom data (which I will try and get - not sure that the values I have were the final production ones) you can't even calculate it. We have this issue logged and it should be addressed with a future release.

Best regards
Rob
RobB-at-Bose
Collaborator
  • 10
  • 1056
  • 0
Registered since

Oct 6, 2008

Re: PM input sensitivity and corresponding meters?

Hi David,

Here are the headroom/clip levels for each analog sensitivity setting (taken from the CSD help file) which should help clarify things for you..

Best regards
Rob
DavidP-at-Bose
Member
  • 0
  • 69
  • 0
Registered since

Nov 19, 2008

Re: PM input sensitivity and corresponding meters?

Cool, thanks Rob. Apologies... I thought I searched the help file and came up blank... now I see it in there... strugglin'!

Everything seems to make sense except for the +12dB sensitivity setting. That is not matching my measurements here in my office. Due to some signal generator limitations, I was using a 0dBu 1kHz test signal. On the +12dBu sensitivity setting, I read -18dBFS on the input meter, and -12dBFS on the output. So in whole input to output, everything matched- with 0dBu input I should have been 12dB away from full output which I was. But the input meter should have been reading -24dBFS according to the help file chart.

Instead it would appear that we only have 6dB of input headroom and must be clipping at +18dBu, again on the +12dBu input sensitivity rating.

Have I confused anyone yet? Wink

Best-
D.
Kyle
Contributor
  • 3
  • 1138
  • 0
Registered since

Feb 13, 2017

Re: PM input sensitivity and corresponding meters?

Hi David,
There are some conversations going on here to explain/address this discrepancy. Just letting you know an explanation will be posted shortly.

Thanks,
Kyle