Transfer Filter / Neumann HT75 Replacement

Construction information for DIY projects, including the MS Mid Side Matrix, Elliptic Equalizer, Mastering Console, Phono Transfer System, Insert Switcher and the Dual Class-A Amplifier. You can post your baby pictures here.
Gold
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Re: Transfer Filter / Neumann HT75 Replacement

Post by Gold » Thu Feb 25, 2021 9:49 pm

mediatechnology wrote:
Thu Feb 25, 2021 8:37 pm
Yes, that's about as close to 16 kHz as we can get on the LPF with E6-series capacitors.
Great. I’ve never measured the HT75’s. I hope I’m not coming across as nit picking. I’m trying to learn. Do the same component tolerances account for the roll off being -14dB at an octave out instead of -18dB?

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mediatechnology
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Re: Transfer Filter / Neumann HT75 Replacement

Post by mediatechnology » Thu Feb 25, 2021 9:52 pm

I measured the slope on mine at 18 dB/octave.
My reference points were a little farther outside the pass band than 2xFc and Fc/2.
Its a Butterworth alignment so the initial rolloff isn't as steep as the outer skirts.
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Gold
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Re: Transfer Filter / Neumann HT75 Replacement

Post by Gold » Fri Feb 26, 2021 6:58 pm

I fixed the response of Pre B LPF. It was all of my own doing as usual. Yesterday I fixed the Pre B HPF section which of course wasn't broken...

I took another look at it today. I had the 680p and the 10n capacitor positions swapped on the right channel. Now it matches to a few hundredths of a dB like most of the rest of them.

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Re: Transfer Filter / Neumann HT75 Replacement

Post by Gold » Mon Mar 01, 2021 3:47 pm

It's done. It of course took much longer than I thought. That's kind of a good thing. If I accurately could estimate time I probably wouldn't have started in the first place.

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The faceplates are getting neater. This one has some mistakes but I'm happy with the overall look. I did the stripe down the middle on the micro mill. It's the first time I've tried something like this. I like the way it looks.

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There is a lot of wiring. There are separate power supplies for Preview and Modulation. This is all eight channels.

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The power distribution is done with these DIN rail terminal blocks. I had to diode isolate the Relay Common's so they didn't talk to each other through the return path. Luckily I've been through that already and knew what to do.

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Installed in the console. Now it's time to master a record and cut a couple of sides.

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mediatechnology
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Re: Transfer Filter / Neumann HT75 Replacement

Post by mediatechnology » Mon Mar 01, 2021 4:29 pm

Now it's time to master a record and cut a couple of sides.
Yea!
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Americas Frontline Doctors Lawsuit Motion For Preliminary Injunction Of Covid-19 Vaccine Emergency Use Authorization: https://waynekirkwood.com/images/pdf/Am ... zation.pdf
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Gold
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Re: Transfer Filter / Neumann HT75 Replacement

Post by Gold » Mon Mar 01, 2021 4:51 pm

I can't thank you enough Wayne. You saved my butt. The console sounds better already.

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