MS Mini - 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.
Post Reply
User avatar
mediatechnology
Posts: 4943
Joined: Sat Aug 11, 2007 2:34 pm
Location: Oak Cliff, Texas
Contact:

MS Mini - Mid Side Matrix Construction Information

Post by mediatechnology » Wed Sep 08, 2021 8:29 pm

MS Mini Mid Side Matrix Construction Information

This is the construction thread for the Mid Side Mini MS Matrix.

Image
MS Mini Mid Side Encoder-Decoder PCB Assembled

Buy Assembled and Tested, Boards with ICs or Bare Boards here: https://ka-electronics.com/shop/index.p ... ide%20Mini
Mid Side Mini Assembly and Test Documents: https://ka-electronics.com/images/pdf/M ... 0821_1.pdf
Mid Side Mini Mouser Project Manager Bill Of Materials: https://www.mouser.com/ProjectManager/P ... 238566cd15

Image
MS Mini Mid Side Encoder-Decoder Schematic

Fragletrollet
Posts: 8
Joined: Sat Oct 31, 2020 9:55 am

Re: MS Mini - Mid Side Matrix Construction Information

Post by Fragletrollet » Fri Nov 12, 2021 9:10 am

Hello!

I see most circuits using That chips normally use +/-15V, although the datasheets state they will run happily up to +/-18V. How does different rail voltages affect the headroom of the chips? The stated "Input Voltage Range" in the datasheet, does that refer to a +/-18V setup?

This will be used in a valve compressor with very clean amps with high headroom, so I believe the That chips onboard here will define the headroom of the unit, as they have lower headroom than the compressor. What (dis)advantages are there to running this at +/-18V compared to +/-15V?

Also, what would be the easiest way to bypass the M/S processing board, to use the unit as L/R? Something like bypass relay wiring of the M/S board + relaying the I/O of the compressor from the M/S I/O to the general I/O? ...so if I'm correct, 4 dpdt relays should do the job?

Edit: oh and 35V for the caps when using +/-15V and 50V when using higher rails, I presume?

User avatar
mediatechnology
Posts: 4943
Joined: Sat Aug 11, 2007 2:34 pm
Location: Oak Cliff, Texas
Contact:

Re: MS Mini - Mid Side Matrix Construction Information

Post by mediatechnology » Fri Nov 12, 2021 11:26 am

Hi -
I see most circuits using That chips normally use +/-15V, although the datasheets state they will run happily up to +/-18V. How does different rail voltages affect the headroom of the chips? The stated "Input Voltage Range" in the datasheet, does that refer to a +/-18V setup?
Using +/-18V is no problem - you'll pickup just under 1.6 dB of additional headroom.

For the 1246 the +27.5 dBu maximum input level is specified with +/-15V supplies.
On the 1646 the +27.5 dBu maximum is specified with +/-18V supplies but that's with a 600Ω load so in practice if the load is bridging the 1646 can usually provide +27.5 dBu with +/-15V and a tad more with +/-18V rails.

I don't see a downside to using +/-18V.
Also, what would be the easiest way to bypass the M/S processing board, to use the unit as L/R? Something like bypass relay wiring of the M/S board + relaying the I/O of the compressor from the M/S I/O to the general I/O? ...so if I'm correct, 4 dpdt relays should do the job?
Maybe an insert switcher board with no Flip and only one insert's worth of relays would be the simplest?

I recall the BOM specifying 35V caps.

Fragletrollet
Posts: 8
Joined: Sat Oct 31, 2020 9:55 am

Re: MS Mini - Mid Side Matrix Construction Information

Post by Fragletrollet » Fri Nov 12, 2021 12:59 pm

No need to up voltage rating on caps when using +/-18V?

User avatar
mediatechnology
Posts: 4943
Joined: Sat Aug 11, 2007 2:34 pm
Location: Oak Cliff, Texas
Contact:

Re: MS Mini - Mid Side Matrix Construction Information

Post by mediatechnology » Fri Nov 12, 2021 1:06 pm

Since the bypass caps reference to ground they'll only see 18V of their 35V rating.

In a lifted ground fault scenario the caps are in series so they would only see 36V of their combined 70V rating.
They probably wouldn't split equally but in the unlikely situation where one cap was fully-shorted the other would only see 36V.

Fragletrollet
Posts: 8
Joined: Sat Oct 31, 2020 9:55 am

Re: MS Mini - Mid Side Matrix Construction Information

Post by Fragletrollet » Fri Nov 12, 2021 1:26 pm

Thanks for the explanation, makes sense :idea:

Post Reply