TDA1541A sin(x)/x, I/V ... do I get this right

Posted by MBK (A) on March 8, 2002 at 09:47:02

Hi all,

after reading more I have the impression I start getting a grip. Many black holes still there though. So am I getting this right:
1- after non-oversampling mod in my 1541 equipped Rotel I now have a 44.1 kHz stepped output with all aliases present
2- these aliases past 22 kHz cause attenuation of sin(x)/x form and of course HF down the road that may cause problems (though it sounds fine to me in raw form, right now the original NE5532 and original analog filter are still in there).
3- to fix phase error close to 20 kHz and to get rid of HF aliases, thus fixing the sin(x)/x as well, passive 3 pole Bessel filters have been proposed after resistor based I/V conversion and subsequent transformer gain stage and tube gain stage. Alternately, I/V and nothing after that.

Problem:

I'd like to avoid transformers and tubes but like to put a suitable sin(x)/x filter anyway. May be op amp based (reason: passive I/V w/o transformers and tubes need gain somewhere, the rest of my chain is SS and I use active x-o's in my speakers AND op-amp chip amplifiers to one lonely tube somewhere won't make it a tube system anyway).

Questions:

1- to avoid loading op-amps with HF, may one do a passive I/V immediately followed by a passive sin(x)/x filter before the first op amp gain stage? Does that make sense at all? I'd think it saves the first op amp some HF load
2- the cutoff point and construction/calculation of this 3 pole Bessel lowpass is somehow lost on me (20 kHz?), anywhere in archives or datasheets I can only find it mentioned as "trivial" hahahaha...
3- if no passive filter before further gain is possible (that means, op amp pick up) how about an 4th order L-R after op-amp buffer, instead (the buffer takes the full brunt of the aliases though); I built those for my speaker x-o's so at least I'm on safer terrain here...

Thanks,

MBK

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Topic - TDA1541A sin(x)/x, I/V ... do I get this right - MBK 09:47:02 03/08/02 (19)

Re: TDA1541A sin(x)/x, I/V ... do I get this right - Elso Kwak 14:24:40 03/08/02 (17)

Ahhhhh!! - MBK 23:10:56 03/08/02 (11)

Re: Ahhhhh!! - Elso Kwak 03:35:28 03/12/02 (9)

Re: Ahhhhh!! - MBK 07:11:10 03/12/02 (8)

Re: Ahhhhh!! - Elso Kwak 00:20:14 03/13/02 (7)

Re: Ahhhhh!! - MBK 00:52:37 03/13/02 (6)

Re: Ahhhhh!! - Elso Kwak 09:46:24 03/13/02 (5)

Re: Ahhhhh!! - MBK 10:20:16 03/13/02 (4)

Re: Ahhhhh!! - Elso Kwak 12:29:28 03/13/02 (3)

changed to resistor i/v now... - MBK 09:23:52 03/14/02 (0)

Re: Ahhhhh!! - MBK 02:06:17 03/14/02 (1)

Re: Ahhhhh!! - Elso Kwak 13:18:07 03/15/02 (0)

Re: Ahhhhh!! - Thorsten 04:47:22 03/09/02 (0)

Re: TDA1541A sin(x)/x, I/V ... do I get this right - Thorsten 15:28:55 03/08/02 (4)

Re: TDA1541A sin(x)/x, I/V ... do I get this right - steve jones 11:06:50 03/09/02 (1)

Re: TDA1541A sin(x)/x, I/V ... do I get this right - Thorsten 15:57:00 03/09/02 (0)

Re: TDA1541A sin(x)/x, I/V ... do I get this right - JRR 20:20:14 03/08/02 (1)

Re: TDA1541A sin(x)/x, I/V ... do I get this right - Thorsten 04:38:28 03/09/02 (0)

Re: TDA1541A sin(x)/x, I/V ... do I get this right - Thorsten 11:09:31 03/08/02 (0)

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