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Re: MEP-250 Bridged-T equalizer

Posted: Mon Mar 25, 2019 7:33 pm
by billshurv
Suddenly I remember why I am using a PC for parametric duties. I'd never find time to build that.

Re: MEP-250 Bridged-T equalizer

Posted: Tue Mar 26, 2019 2:02 pm
by Gold
billshurv wrote:
Mon Mar 25, 2019 7:33 pm
Suddenly I remember why I am using a PC for parametric duties. I'd never find time to build that.
It took about 100 hours to build. The second unit I expect to come in at half that or less. These EQ’s are for a console that will be used daily to generate billing. I certainly wouldn’t do it just for fun. These cost a fortune to build. The second one is well in its way.

Re: MEP-250 Bridged-T equalizer

Posted: Wed Apr 03, 2019 11:17 am
by Gold
Some notes on a real Sontec. They use polystyrene caps for the smaller value in the tuning circuit. I guessed right on that. This one used Evox (Kemet) polypropylene film caps for the larger value. This one had a noise floor of -82dBu unweighted. The one I built has a noise floor of -86dBu.

The one I built doesn’t sound exactly the same but it’s in the same ball park. Mine is a two opamp 250 style. This Sontec is a 4xx and is a three opamp version. On the three opamp version sum and output use separate opamps.

Re: MEP-250 Bridged-T equalizer

Posted: Tue Dec 10, 2019 6:12 pm
by Bill Wilson
In the Sontec circuit C25's value is 33mfd, 6vdc. The values for all 5 filter frequencies are listed ln the lower right hand corner of the schematic.

Re: MEP-250 Bridged-T equalizer

Posted: Wed Dec 11, 2019 2:17 pm
by Gold
The ones I built aren't an exact clone of a 250 or 430. The tuning capacitors aren't the values listed in the 250 schematic. It's kind of a mashup of the 250 and the GML 8200. The 430 uses three op amps in the summing section. One for Input, one for Output and one for summing.