MTC-MS-II Mid Side Matrix Construction Information

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.
berkfinger
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Joined: Tue Oct 10, 2023 5:39 am

Re: MTC-MS-II Mid Side Matrix Construction Information

Post by berkfinger »

Hello,

I'm putting together an MSII_38 board at the moment. I noticed the BOM doesn't appear to include the 4 x 1M ohm resistors that are needed for R4, R11, R12, R14...

I DO have 4 spare 100k resistors from the BOM order.

Just checking if I am supposed to go with 1M ohm?

Many thanks,

Simon.
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mediatechnology
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Re: MTC-MS-II Mid Side Matrix Construction Information

Post by mediatechnology »

berkfinger wrote: Tue Oct 10, 2023 5:46 am Hello,

I'm putting together an MSII_38 board at the moment. I noticed the BOM doesn't appear to include the 4 x 1M ohm resistors that are needed for R4, R11, R12, R14...

I DO have 4 spare 100k resistors from the BOM order.

Just checking if I am supposed to go with 1M ohm?

Many thanks,

Simon.
Hi Simon. Thank you for joining us!

You can use 100KΩ.

R4, R11 and R12 provide bias current in the event a pot or stepped switch isn't connected to Width or Tilt EQ.
100KΩ is fine and best if the control is a pot.
If a make-before-break stepped switch is used 1MΩ will provide a little more accuracy in step size near the midpoint of a linear taper switch.

R14 provides bias current for IC8 when J1 is open and when RY4 is switching between positions with J1 linked to "A.".
100KΩ is a good all-around choice for R14 and, if a Mid attenutor isn't used or J1 isn't in the -3dB "B" position, then 10KΩ might be even better when RY4 switches.

BTW IMHO keeping Mid unity gain at J1 ("A") and not using the Mid Attenuator connector is the configuration I would recommend.
Pivoting Side gain around Mid using the Width control achieves the same result and saves a pot or switch.
Mid build-up from strong Mono correlation can always be compensated using RY1 the Mid Gain relay which is an accurate -6 on encode and +6 on decode.
When more Width gain is needed than the 6 dB provided J1 set to B allows up to 9 dB of relative Side gain.
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mediatechnology
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Re: MTC-MS-II Mid Side Matrix Construction Information

Post by mediatechnology »

@berkfinger Thanks for reminding me that although I updated the instructions back in February when I changed the BOM I never uploaded it. The updated assembly documents are in the first post. Still need to change the schematic...
berkfinger
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Re: MTC-MS-II Mid Side Matrix Construction Information

Post by berkfinger »

Thankyou that clears it up!

I guess I should ask before I order one:

Does this switch look suitable for switching Insert Relays and the functions of the M/S board? I've been struggling to find many options here in Australia.

https://au.element14.com/eao/18-287-035 ... o%20switch

Thanks,

Simon.
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mediatechnology
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Re: MTC-MS-II Mid Side Matrix Construction Information

Post by mediatechnology »

Those EAO will work and are nice switches.

You might want to take a look at NKK from Mouser. The YB-series is similar and may be more available and less expensive: https://www.mouser.com/datasheet/2/295/ ... 663306.pdf

Whatever bushing mount switch you buy be sure to order a wrench to tighten the bushing.
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