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Old 16th December 2004, 05:00 PM   #1
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Default impedance mismatch?

I recently finished a GC using Brian's kit. I'm impressed initially with the sound but last night I replaced an AVA mosfet 100w/chan (old Dynaco ST150) with the gainclone and noticed not so good bass performance. The application is a bi-amplified speaker system using a S&B TX102 TVC driving an active xover. Signal below 200 hz is sent to the GC (or mosfet amp) for bass duties. Speakers are big Altec 515s. What I'm hearing...... the mosfet amp gives tighter more tuneful bass performance. The GC is a little uncontrolled and tubby sounding. Bass notes seem to all run together.

Any idea how to analyze this problem to see if it is an impedance issue?

Jim D.
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Old 16th December 2004, 05:13 PM   #2
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As I recall, GC builders use more supply capacitance when the amp is confined to bass duties. Try 10,000 mfd.
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Old 16th December 2004, 07:23 PM   #3
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lots of capacitans and a snubber should do the job. 2*1500uf on chip is nothing near enough for bass, and not enough for anything else either, or at least so i think, having compared 2*1000uf per board, 2*1000uf per board+2670uf per rail in the PS, 2*1000 per board+6200 in the PS, and finally, and what i ended up using, 2*1000uf per board+ 6200uf per rail en the PS with a snubber. read carlosfm's post about the big capacitans psu for chipamps. it's on the first page.

regards
marius
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