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Chip Amps Amplifiers based on integrated circuits

Experts needed: Crazy phase issue with Inverted Gainclone
Experts needed: Crazy phase issue with Inverted Gainclone
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Old 20th February 2003, 06:06 AM   #31
PaulHilgeman is offline PaulHilgeman
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Join Date: Dec 2002
Default Issues Resolved

Hey Guys,

Thanks for all of the support. Last night I did about 6 hours of research and testing. I 'reverse' wound my transformer and got it down to 19-0-19 VAC, I incrased the capacitence to 3300uF per rail plus 1000uF per rail, per chip right near/on the chip.

Lastly, and this is pure dumbness on my part. I have my system in a 12x16 room, and if you do the calculations on this, there is a huge hole starting at 35Hz, going all of the way to 55Hz of about -8dB.

So, the combination of all of these iterations of research has brought me to the conclusion that the am sounds incredible, more so with the lowered PS voltage (this made the largest difference), and the increased capacitence (this made a difference in that the lower mids are much more 'meaty' and bold), and the realization that I had a 6dB bass boost on my old amp that I had totaly forgoten that I had turned on 8 months ago when I had goten this room 'flattened' out.

So, the moral of the story and what my ears heard is that the lower supply volage is very very important, even when driving nominal 6 or 8 ohm speakers. I would just stick with 18-0-18 no matter what, or possibly 20-0-20. I had ordered 25-0-25, and with my higher than average wall voltage was getting about 27-0-27 which was too high for the 3886 to handle.

Second moral, after probably 6 to 8 hours of listening, I do prefer a slightly higher capacitence (I still have the original 1000uF caps near the chips though). I will of course remove these additional 3300uF caps closer to the PS in a couple of weeks when the amp is broken in and see how it sounds.

Third moral, even if you set your previous amp up months ago, and then sold it and couldnt see what the settings were, try and remember if you had a bass boost. to remove or help out some of your room modes. I was burned by this one, and now that I am listening to a flat amp, I have nulls of about -8dB in the bass region, which is killing some things pretty bad. I will desing a cicruit to correct this though.

Thanks again
-Paul Hilgeman

P.S. I will post final pictures soon!!!
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