Hi,

I own a Focusrite Liquid channel and am still getting used to it's features and performance.

I noticed on a recently vocal recording that there appeared to be a small amount of distortion on some loud sections. I had my Liquid Channel connected to my Focusrite Saffire Pro DSP 24 via the digital connection and the meter in the Saffire MixControl was peaking around -10db. The meter on the Liquid Channel was barely flickering even though it was on around 30db gain.

The mic that I used was a Neumann TLM102.

I had a look at the specs of the Liquid Channel and it says the maximum input is +16dbu. I looked at some other preamps and they have there specs generally range from +24dbu - +30dbu for maximum level before clipping or headroom.
To be honest I'm not really sure what these specs mean or how they translate to real world performance!
The spec for for my UA Solo 610 says -12dbu!?

The Liquid Channel looks pretty low compared to some of these other preamps. I'm only using the Liquid Channel for vocals and miking acoustic guitars and upright bass.

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www.richardpenrose.com

You're comparing the max input of the LC with the max output of the other units. The LC has plenty of headroom. Could it be the mic that was distorting?

H

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Technical Editor, Sound On Sound

That would be my guess too. Swap it out for an SM7 and if it still distorts at the same level to DAW then investigate further.

J

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www.jackruston.com

Quote Hugh Robjohns:

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You're comparing the max input of the LC with the max output of the other units. The LC has plenty of headroom. Could it be the mic that was distorting?

H

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Hi,

I just had another look at the True Systems P-Solo specs and it clearly says maximum input level +25dbu. Also the DAV BG1u has a clipping level of +29dbu?

http://www.true-systems.com/p-solo.html

http://www.davelectronics.com/bg1u.htm

Do these mean different things?

The Neumann TLM102 has a maximum SPL of 144db so I'd be very surprised if that is distorting unless other things can make the mic sound distorted?

Also, how does a maximum input level of +16dbu translate into real world performance? What would that equate to?

Thanks

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www.richardpenrose.com

Quote dickiefunk:

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I just had another look at the True Systems P-Solo specs and it clearly says maximum input level +25dbu. Also the DAV BG1u has a clipping level of +29dbu?

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References to max level or clipping level in preamp specs normally relates to the maximum line output level. With pro products it would typically be somewhere between +24 and +30dBu -- most being around +24 to +28dBu.

The maximum input level will vary a lot more and isn't often stated, but would typically be anywhere from 0 up to +18dB or so, with a few going higher, up to maybe +24 or +26dB. There aren't many that go higher than that, but I've met a few. It largely depends on the attenuation of the input pad.

Quote:

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The Neumann TLM102 has a maximum SPL of 144db so I'd be very surprised if that is distorting unless other things can make the mic sound distorted?

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Fair point, but it can happen -- and distortion starts much lower than 144dB -- it reaches 0.5% THD at 144dB! As for the actual signal levels concerned, the TLM102 has a sensitivity of 11mV/Pa. 1 Pascal is a sound pressure level of 94dB SPL, giving an output of -37dBu. The maximum sound pressure of 144dB SPL is 50dB higher, so the output from the mic would also be 50dB higher, which would be +13dBu -- and that's not likely to upset most decent preamps.

Distortion exists in many different forms and can be caused in many different ways. I'd be surprised if the preamp is the culprit -- the LC has one of the best mic preamps circuits available anywhere -- but it can happen. What you really need to do is make a series of substitutions to track down the problem.

For example, it could be the source itself breaking up at high volume -- voices do make the strangest of noises sometimes! It could be a mechanical or electrical fault within the mic. It could be because the correct phantom power isn't reaching the mic, possibly because of a cable fault or a strange cable. It could be that the mic doesn't like the preamp's input impedance or the impedance of the cable come to that! It could be a preamp input overload. It could be a preamp output problem, not liking the load it is having to drive, it could be a converter issue.... And the list goes on.

I'd start with substituting the mic cable as a first step, followed by swappingthe mic, as was suggested above. Swapping the preamp would be the next... and so on until you track down the problem.

You might find this article from the www.microphone-data.com website helpful:

http://www.microphone-data.com/media/filestore/articles/MW%20mic%20specs-1 0.pdf

hugh

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Technical Editor, Sound On Sound