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steve355



Joined: 02/03/07
Posts: 485
Loc: Stevenage, Herts
Measuring s/n ratio
      #785220 - 06/11/09 12:47 PM
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Is there an easy way to measure the s/n ratio of my preamps? (separately) I'd like to compare them against the specs.

Cheers

Steve

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Hugh RobjohnsAdministrator
SOS Technical Editor


Joined: 25/07/03
Posts: 10732
Loc: Worcestershire
Re: Measuring s/n ratio new [Re: steve355]
      #785338 - 06/11/09 06:10 PM
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Terminate the input with a 150 ohm resistor soldered between pins 2 and 3 of the XLR. (For American preamps, use 200 ohms -- it's the standard they mostly use over there).

Measure the residual noise level. Add the gain of the amp. That gives the Equivalent input noise figure (EIN). Example: if the residual noise with the input termination fitted measures -65dBu, and the preamp was set to 60dB of gain, then the EIN is 65+60 = -125dBu

hugh

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steve355



Joined: 02/03/07
Posts: 485
Loc: Stevenage, Herts
Re: Measuring s/n ratio new [Re: Hugh Robjohns]
      #786134 - 09/11/09 10:58 PM
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Quote Hugh Robjohns:

Terminate the input with a 150 ohm resistor soldered between pins 2 and 3 of the XLR. (For American preamps, use 200 ohms -- it's the standard they mostly use over there).

Measure the residual noise level. Add the gain of the amp. That gives the Equivalent input noise figure (EIN). Example: if the residual noise with the input termination fitted measures -65dBu, and the preamp was set to 60dB of gain, then the EIN is 65+60 = -125dBu

hugh



Thanks Hugh. The preamp is an American clone of a British design, so I'll contact the guy to ask which resistor to use. I guess the residual noise can be measured in a DAW by recording "silence".

Cheers

Steve

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MikeOates



Joined: 16/01/06
Posts: 384
Loc: Manchester, UK
Re: Measuring s/n ratio new [Re: Hugh Robjohns]
      #786289 - 10/11/09 01:06 PM
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That's great Hugh, I did not realise it was so simple, but how is the level measured, average RMS power, or total RMS power?

Mike

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Audio Recording Live

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