martthie_08
Well-known member
anyone experienced with 1073 style circuits that could give me some advice on a EQ I am trying to fix in the studio?
It is a Chandler LTD-1, which works great (after replacing a buggy Lorlin switch with an ELMA), but once I engage the high pass filter there is a really noticable hum on the output (50Hz, 100Hz, 150Hz, 200Hz, etc).
The hum is not affected by the Line input gain switch, but varies with the output trim pot and changes depending on the filter cutoff frequency.
Here are some quick and dirty measurements (just for comparing the relative levels):
no EQ <-80 dB
no HPF -77.5 dB
50 -70.0 dB
80 -66.6 dB
160 -64.1 dB
300 -68.3 dB
does that ring a bell to anyone?
I presume this circuit is inductor based? Might it be a shielding issue?
I have tried lifting the 0V on the output, but to no effect...
I'd love to get this "fixed" as the filter sounds really good.
thanks for any help!
cheers, Marten
It is a Chandler LTD-1, which works great (after replacing a buggy Lorlin switch with an ELMA), but once I engage the high pass filter there is a really noticable hum on the output (50Hz, 100Hz, 150Hz, 200Hz, etc).
The hum is not affected by the Line input gain switch, but varies with the output trim pot and changes depending on the filter cutoff frequency.
Here are some quick and dirty measurements (just for comparing the relative levels):
no EQ <-80 dB
no HPF -77.5 dB
50 -70.0 dB
80 -66.6 dB
160 -64.1 dB
300 -68.3 dB
does that ring a bell to anyone?
I presume this circuit is inductor based? Might it be a shielding issue?
I have tried lifting the 0V on the output, but to no effect...
I'd love to get this "fixed" as the filter sounds really good.
thanks for any help!
cheers, Marten
