2. analog
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KAB Rumble filter gets preamp to overload/distort?

So, I have always hated to see the woofers on my speakers bouncing around while playing vinyl no matter how well I chose and set up my systems (all of my turntables-arms-cartridges exhibit a resonance frequency around 9-10 hz). I decided to give the KAB rumble filter a try to eliminate this problem. I got it today and it works without having any apparent effect on sound quality until i notice something WEIRD:

I usually set the gain on my Manley Steelhead for the Clearaudio Maestro around 50-55db . While playing a London FFRR LP of Askenazy playing Rachmaninoff's preludes, I heard some distortion very much like the breaking-up sound of mistracking on both channels. I was so scared that was something wrong with the Maestro and it was eating up my record, so I immediately stopped playing and took it under a microscope to check the stylus..To my relief, it still looked very much like new (about a year old but playing sparingly and always on new, clean records), so I proceeded to check the tracking force, anti-skating and everything is fine. I took out a test record to roughly check the tracking and BOTH channel buzzed like crazy that I thought the cartridge's suspension was out or something.

At this time I didnt know what else to check rather than thinking of finding someone to give the cartridge a complete health check, then with a very faint hope, I decided to just use the Steelhead's lowest gain to see how it went and voila..the distortion disappeared.

My particular analog rig never acts like this, and the Clearaudio Maestro - Moerch DP6 red dot - Thorens TD-124 has been a tracking champ, so the culprit must be the newly added KAB rumble filter!

I took it out of the chain, ran the test on both 50db and 55db gain and everything is fine..no tracking distortion, no overload!

I will try to contact KAB to find out what the problem might be, but meanwhile, can anyone explain why a rumble filter can cause this distortion??

Does anyone has this type of problem with KAB rumble filter before?

Thanks
jaytea

Showing 1 response by rpfef

rpfef
110 posts
 
I had the same experience with the KAB filter when I switched preamps.
The problem, according to the designer of the new SS preamp (Reflection Audio OM-1), is that the tape output is not buffered, whereas it was buffered on my old one, a tube design. Therefore I could not use the tape loop.
I do not know how common it is the have an unbuffered tape out but potential users of this fine rumble filter should be alert to this possibility.
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