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Old 19th March 2005, 06:45 PM   #1
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Default need help with LM4651/2 filters and volume control

sorry for starting a new thread folks, but im new at this and didn't really ask the correct question in the subject box last time.
So here it is again.

Iím building a class D amplifier, using the LM4651 and LM4652 chip set I intend to provide two full range and a subwoofer/ low pass channel. Power will be provided by three separate toroidal transformers to avoid crosstalk and something like 30 and 18 odd thousand uF on the board which I hope will stabilise it without regs. Any comments on this are welcome.
Iíve simulated a filter system which seems to work quite well which hopefully I can post here somewhere, but how does this affect the input resistance the main amplifier is required to see or match with the values of R1, R2 (not their ratio) and RLP, CLP should they be removed with such an active filter?
Is this a good way to take a low pass from a stereo signal?
Any has anybody please got any ideas on how to implement a volume control?

Cheers from spud
(if anybody needs my help I'll do my best though I still feel like a baby at this)
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Old 8th April 2005, 03:30 PM   #2
jmateus is offline jmateus  United States
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Default Lm 4651 / 4652

I can see you`re working on a class D amp based on those chips.
I, too, have those chips but I`m having trouble in finding a PCB
for them. I hate to install the chips on a Perforated board and
not doing so I have to find a PCB to implement the amp.

What did you do for PCB, did you fabricated it? I could do it, but
if it requires a double face one I`m in trouble I canīt do it...
To your knowledge are there any PCB available out there?
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Old 13th April 2005, 07:43 PM   #3
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Sorry, posted in your other thread before seeing this one. Check out that post and then post back to this thread with any more questions.
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Old 19th April 2005, 06:17 PM   #4
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for PCB we used 2 single sided units, cos we didnt have a double and took the gerber layers from National Sems site printed em on inkjet and lined up copper bottom and top on separate sheets, which we stuck to form an envelope to accomadate the board. It came out lined up enough to work, i hope

also see reply in other post
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