So I bought a Behringer mic800 microphone preamp about 6 years ago, just to use as a talkback preamp. Obviously I know this thing is cheap... When I first opened it and hooked it up I immediately noticed a hissing noise.I know that cheap equipment will give you not so great signal to noise ratio, but this was beyond that. It made the preamp unusable. I tried to contact behringer but had no luck so it just sat around the studio for all of these years. My question is, What would be a likely cause for this hissing noise? A bad transistor or opamp? Again... I know this preamp is shitty, so please don't respond with sarcastic comments. Thanks!
A preamp will generally be noisier without a microphone attached. To test it properly without a microphone, connect a 150 ohm resistor between pin 2 and pin 3 of the XLR input and then measure the noise. The 150 ohm resistor simulates the output impedance of the mike, and will likely be in parallel with much larger resistances in the input stage that are causing the excessive noise.
Thanks for the response Monte. The noise is with or without a microphone attached. I've tried a few different mics all with the same result. Would it help if I could record a sample of the type of hiss I'm getting?
Hissing could be a failed or faulty semiconductor near the beginning of the amplifier chain.
It could also be a broken connection that then presents the input with a very high impedance that generates excessive wideband noise.
It could also be a broken connection that then presents the input with a very high impedance that generates excessive wideband noise.
Andrew is right, it could be just an exemplary fault. Behringer may be cheap but they don't sell units that are from the outset noisy like that.
Too bad you didn't test it immediately when you bought it, you might have returned it for a swap at Behringer.
Jan
Too bad you didn't test it immediately when you bought it, you might have returned it for a swap at Behringer.
Jan
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