posted 28 April 2005 08:42            

My Capybara outputs a (sort of) white noise when powered on. The level is - 2 dBu ; it is very loud if no attention is given when powering on the devices.

I would like to know if it is a bug or a feature ;-)
By the way, I saw that there will be a firmware update in order to run ASIO or CoreAudio drivers with the Capybara. In the case that this is not an intended feature, is there a way to take this opportunity and tell the Capybara to output nothing when powered up (before Kyma connects to it)?

Last thing: there is a tiny high pitched noise while operating. I don't find it annoying but I would like to know if others noticed it and if yes, if they measured it. The noise is not present on digital outputs.

posted 28 April 2005 12:43            

quote:

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Originally posted by tuscland:

Last thing: there is a tiny high pitched noise while operating. I don't find it annoying but I would like to know if others noticed it and if yes, if they measured it. The noise is not present on digital outputs.

Best Regards,
Camille

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My Capy is VERY quiet; if I want to hear a hiss I have to crank the gain to max and monitor level to max!

posted 29 April 2005 12:03            

I just wondered if you were connecting to your mixer as balanced or unbalanced ?

posted 29 April 2005 12:11            

quote:

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Originally posted by pete:
Hi Cam

I just wondered if you were connecting to your mixer as balanced or unbalanced ?

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Hi Pete,

My Capybara is connected balanced with 'XLR male / XLR female' connectors, but I plan to buy 'XLR / balanced jack' cables and connect the Capybara on the Line jack input because the gain is too hot for the mic input - however the mic input of my small Mackie has lots of headroom, but still I need to lower the Capybara's output gain.

posted 29 April 2005 12:42            

there was a posting a while back that the capy analogue outs are actually phase reversed so if your inputs on the mixer are not truly balanced (some manufactures use balanced connecters but the internal wiring is such that the neg side of the signal and the ground get wired together) if this is the case then the combination can be sending noise from the ground line into your audio chain. That noise may not always sound like 60hz buzz it can sometimes just be a hiss. Perhaps someone else on the forum can verify about the analogue i/o as the posting was a fair while ago.

Also the under the kyma > preferences menu there is a setting for the output level of the capy.

posted 29 April 2005 13:09            

quote:

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Originally posted by rafe:
hi cam

there was a posting a while back that the capy analogue outs are actually phase reversed so if your inputs on the mixer are not truly balanced (some manufactures use balanced connecters but the internal wiring is such that the neg side of the signal and the ground get wired together) if this is the case then the combination can be sending noise from the ground line into your audio chain. That noise may not always sound like 60hz buzz it can sometimes just be a hiss. Perhaps someone else on the forum can verify about the analogue i/o as the posting was a fair while ago.

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The hiss is around 8 kHz, here a screenshot of an analysis I made under Wavelab. I can live with it, but it is a bit annoying, see my answer to your next question.

quote:

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Also the under the kyma > preferences menu there is a setting for the output level of the capy.

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Yeah, as the Capy's output are very hot for the mic inputs of the mixer, I used this setting to lower the output. But this leads to two VERY annoying side-effects :

1. The DSP status window doesn't show a normalized digital output, but the output that is actually sent to the D/A converters. I mean if a Sound outputs at 0dB, the DSP status window will show a signal at -15dB. I find it annoying because I have less readability of the actual headroom I can dispose, and I don't really know if the Sound is clipping or not. (I hope this is clear enough, english is not my mother tongue ;-))

2. If I digitally lower the output of the Capy by 15 dB, I also loose 15 dB of dynamics. For instance, I measured the hiss to have a peak at 8 kHz, - 96 dB (the measure is not precise at all). Having the Capy outputting 15 dB lower, makes the hiss by relation 15 dB higher : - 81 dB.

In conclusion, I don't really like to lower the gain using this option, I prefer to lower the gain on the mixer.

posted 01 May 2005 20:33            

It's interesting that, in standard SNR measurements, sine wave peaks don't contribute much at all to the overall noise measurement (integrated from 0 to 20 kHz). But the human auditory system is able to pick out even these very low level sine waves that are just above the white noise floor.

posted 03 May 2005 05:12            

quote:

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Originally posted by SSC:
We will make this fix into a Preferences item in the next update of Kyma that we post on the tweaky.

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Why integrate this into the Preferences? Are there some occasions where this anomaly might be useful?

posted 03 May 2005 10:11            

We have tried out our solution on 20 D/As over the weekend and it works for all cases. So it is not a situation where you will have to "tune" it or find the sweet spot. Since it is a digital filter, there won't be variations in its response from chip to chip. Once we have incorporated into the code, it will just work automatically on all Capybara-320s.

Limit cycles are well known artifacts of all digital IIR filters which, for certain constant inputs can get into a repeating cycle due to a combination of quantization and feedback. Since this particular limit cycle occurs in a digital filter that is *inside* the Burr Brown chip, we cannot change the filter itself. But we *can* change the value that we feed it as the "resting" or silent value.