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Build help and troubleshooting => EQ573 Equaliser => Topic started by: Slembones on July 15, 2026, 04:39:16 PM

Title: EQ573-II ran in my lab
Post by: Slembones on July 15, 2026, 04:39:16 PM
(https://i.imgur.com/6wqXGxb.png) this is the hi freq eq tests. the boost is a bell when it should be a shelf. the cut is a shelf. Did I do something wrong?  please advise. the unit works fine but thought I would lab test. the plots for mid and low are as expected
Title: Re: EQ573-II ran in my lab
Post by: JPK on July 15, 2026, 06:34:38 PM
It is a shelf but it is followed by a high frequency attenuation after 20kHz caused by the compensation caps in the circuit.
Can you make another diagram with a +/-6dB correction?
Title: Re: EQ573-II ran in my lab
Post by: Slembones on July 15, 2026, 09:40:06 PM
can I mod the unit to be flat to 50K and restore the shelf
Title: Re: EQ573-II ran in my lab
Post by: Slembones on July 15, 2026, 09:41:51 PM
the unit is beginning rolling off at 10K even with the band switches set to "off"
Title: Re: EQ573-II ran in my lab
Post by: Slembones on July 15, 2026, 10:02:09 PM
(https://i.imgur.com/jR8oopR.png) the red Line is switched out and the blue Lin is switch in but with all bands "off"
Title: Re: EQ573-II ran in my lab
Post by: Slembones on July 15, 2026, 10:18:42 PM
(https://i.imgur.com/fyPvHs5.png)This sweep has about 6dB boost and cut you can see the roll off. I also included a flat setting 
Title: Re: EQ573-II ran in my lab
Post by: Slembones on July 16, 2026, 08:57:43 PM
Found the measurements I made of a real 1073. Here’s the flat frequency response at a few different gains
(https://i.imgur.com/efKT68Z.png)flat to 50k Here’s the 1073 High shelf response 
(https://i.imgur.com/otAhQN3.png)
Title: Re: EQ573-II ran in my lab
Post by: JPK on July 17, 2026, 09:12:26 AM
OK, you may have an issue somewhere.
Please wait until I am back at work (end of July) so I can help you.
Title: Re: EQ573-II ran in my lab
Post by: Slembones on July 20, 2026, 07:48:39 PM
I have traced it to the discrete amps circuit with a scope. my component installation is correct. I think the feed back circuit at the end of the descrete op amp is rolling off the highs too soon? (guess). it is happening in both amps the same. the feedback (470pf on A and 150pf on B) cap on the outside of the circuit has little to no effect.  could I have a bad component?