In Reply to: Re: error in "bench" schematic posted by Wayne Parham on January 31, 2003 at 12:15:42:
and it is plain WRONG. A typo. All I changed of his original schematic was the C3 value, and the LP peaking near cutoff goes away completely.
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I have not looked at his original HP in spice...it was apparent there is a significant error as far as the missing resistor(R20) between C8 and the "virtual ground" junction of R11/R12(1 meg). His R10 is WAY too small, probably "tweaked" to compensate for the "unique" 3rd pole layout. BWTFDIK.
For 800Hz. HP BW 3rd order values, the caps(C6,7,8) can all be 2200pF, but R9=180k, R10=90.9k, and R20=45.3k.
For the 800Hz. LP BW filter values, all R's can be 90.9K(R4,5,6) and the C's vary, C2=2200pF, C3=4400pF, and C4=1100pF. These look GREAT to me.
As always, hf comp. is not my bag. These values will be good for jbl/altec systems. HF shelving will be done at the amp.yeah, and C5 MUST be made larger to handle lower amplifier input Z's...looking at 2.2uF for 100K load, maybe OK down to 25K load...but 0.22uF, NO WAY.
.Wayne, if I fax the schematic, can you "proof-read" my results? I have the parts on hand to go with the above values, if I do the series/parallel thing as needed to generate values using 90.9k R's and 2200pF C's. Thanks. Sam
can I email you the spice file itself? how would I manage that?
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