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Using a Power amp with no gain controls?


Distinguished Member
Hi Chaps,

Most amps used for subs have gain control, however I am considering trying a power amp without gain controls. Do you think I am likely to have any probalems with this approach?

The only thing I can think of is that if I continue to use a BFD that I may not be able to set the input level correctly and still be able to balance the levels with the other speakers. I am not sure exactly how critical this is and whether a few dB out on the input levels is worth worrying about? I suppose it is if it is too high though...

If I eventually do build a Linkwitz transform, I assume this would get round that issue?


Adam :)

Member 639844

Former Advertiser
Well I have to have my gain down to about 65% to be able to get the required cut on the sub trim (currently @ -9), without the amps gain I wouldnt be able to do this. I would have to then boost the speaker trims to get the balance right which would throw the reference level out. I think it would be a problem, and dont think an LTC is going to help either, its effect basically amounts to low end boosting, which would increase the issue if anything possibly resulting in your amp clipping hard. It would especially be a problem if you couldnt boost the speakers enough for the balance to be achieved.

You might be able to add in your own gain control though via the BFD or in line independent gain control, not sure though. From the experience of Nimby and I it looks as though a cut is generally needed on the amp which shouldnt be too hard to introduce, but what noise is added into the signal might be of concern. Little bit of research needed I think.
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Distinguished Member
I sometimes use the +/-6dB gain controls on my CX2310 active crossover but then adjust the EP2500 controls once I have found the correct setting. Without some control it would be hard to balance the sub against the speakers. I'm turned down below 12 o'clock on the EP2500 already. I'd have no windows left if I had the EP1500 on "full". The BFD has a switchable control on the back to match domestic AV with pro gear. Using this in combination with the AVR's LFE level adjustment would give you some leeway. Absolute level of the sub relative to the speakers is very dependent on the quality of the subwoofer and how flat its response. I find that the better the subwoofer the more freedom in relative level is possible. Meaning how "hot" you can get away with.

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