dlozanothornton

Sonosax SX-M2 Improvements? M/S circuit?
« on: March 14, 2019, 08:10:27 PM »
Hi there I am wondering about making a modification to a Sonosax SX-M2 to improve audio quality and power issues. The schematics are below.
Would there be any obvious issues with simply swapping the TL072 for a newer opamp (apart from battery life?). Possibly the TL2072 or the 1612OPA (the pins are correct).
Have any opamps improved on the SSM2142 either?
Furthermore, battery life and power noise rejection have been touted as possible issues by other users. Would replacing the si9912dy be a good idea here also? It seems like it has been discontinued, but I can't find an upgrade.

Furthermore, could  some cabling and resistors make an unbalanced M/S encoder out of the two balanced line signals?
M(L+) + S(R+)  = Left, M(L+) + (R-) = Right, with the addition achieved by resistor summing?
« Last Edit: March 14, 2019, 08:35:57 PM by dlozanothornton »


gyraf

Re: Sonosax SX-M2 Improvements? M/S circuit?
« Reply #1 on: March 15, 2019, 03:59:21 AM »
That is not really a full schematic - e.g. what is the "860019" and the "DCH148"..? and I don't see anything named "si9912dy" in the schematic?

The only thing I think you would gain from replacing the TL072 would be a little better low-z-drive-capability on the unbalanced stereo-jack lineout. Of limited value, really.

Don't underestimate the engineers at Sonosax, they know what they are doing.

Jakob E.
..note to self: don't let Harman run your company..

dlozanothornton

Re: Sonosax SX-M2 Improvements? M/S circuit?
« Reply #2 on: March 15, 2019, 07:03:03 AM »
Yes I didn’t post all the schematics, I have a history of doing that but I do actually have them all at home this time.
Ill upload later.
Also the minijack L might help me in my M/S cable,
So XLR L+ plus minijack R going to the Left channel and  minijack L plus XLR R-  going to the Right channel should work... Or will the chip driving the XLRs cause a level imbalance here?

Thanks for the reply Jakob!

gyraf

Re: Sonosax SX-M2 Improvements? M/S circuit?
« Reply #3 on: March 15, 2019, 08:55:34 AM »
I don't think you can use only one/half of the electronically balanced outputs and expect the signal to be predictable.

If you really need MS, why not just go with an external transformer matrix?

Jakob E.
..note to self: don't let Harman run your company..

dlozanothornton

Re: Sonosax SX-M2 Improvements? M/S circuit?
« Reply #4 on: March 15, 2019, 10:37:03 AM »
I don't think you can use only one/half of the electronically balanced outputs and expect the signal to be predictable.

If you really need MS, why not just go with an external transformer matrix?

Jakob E.

So in response to the earlier bit about Sonosax, it’s a 25 year old design at least so I thought there may be upgrades possible.

And I have been in contact with cinemag and they have advised me on a transformer solution as per your circuit that I found in the archives.
But a great solution would be somewhere around $125- $200 (after shipping and enclosure) which I don’t mind but if I could have figured out a simpler solution that would be good...

[silent:arts]

Re: Sonosax SX-M2 Improvements? M/S circuit?
« Reply #5 on: March 15, 2019, 11:10:14 AM »
But a great solution would be somewhere around $125- $200 (after shipping and enclosure) which I don’t mind but if I could have figured out a simpler solution that would be good...

Your location in your profile would help.

I do sell passive MS Boxes (with Lundahl transformers) for EUR 190 (+VAT if applicable) each.
https://www.instagram.com/p/BqPB2aoleze/

A box without transformers would be EUR 85 (+VAT if applicable),
and Andrew may have a pair of Lundahls left?
https://groupdiy.com/index.php?topic=68300.msg896856#msg896856

dlozanothornton

Re: Sonosax SX-M2 Improvements? M/S circuit?
« Reply #6 on: March 15, 2019, 01:38:16 PM »
Here's the schematic I was actually referring too, quite similar in many respects...

dlozanothornton

Re: Sonosax SX-M2 Improvements? M/S circuit?
« Reply #7 on: March 15, 2019, 01:38:53 PM »
And this should fill out the middle bit.

dlozanothornton

Re: Sonosax SX-M2 Improvements? M/S circuit?
« Reply #8 on: March 15, 2019, 01:43:37 PM »
Your location in your profile would help.

I do sell passive MS Boxes (with Lundahl transformers) for EUR 190 (+VAT if applicable) each.
https://www.instagram.com/p/BqPB2aoleze/

A box without transformers would be EUR 85 (+VAT if applicable),
and Andrew may have a pair of Lundahls left?
https://groupdiy.com/index.php?topic=68300.msg896856#msg896856

Very pretty box! I may consider it...

dlozanothornton

Re: Sonosax SX-M2 Improvements? M/S circuit?
« Reply #9 on: March 16, 2019, 05:26:19 PM »
http://cinemag.biz/output/PDF/CMOQ-2.pdf
This seems to have better specs than the lundahl and is cheaper in this part of the world new.

http://www.lundahl.se/wp-content/uploads/datasheets/1527_7xl.pdf


gyraf

Re: Sonosax SX-M2 Improvements? M/S circuit?
« Reply #10 on: March 18, 2019, 03:21:08 AM »
I'm not sure that you'll want bifilar wound coils for MS-matrixing - iirc, we run into strange issues because of inter-winding capacitive couplings..

Jakob E.
..note to self: don't let Harman run your company..

dlozanothornton

Re: Sonosax SX-M2 Improvements? M/S circuit?
« Reply #11 on: March 18, 2019, 08:49:15 AM »
I'm not sure that you'll want bifilar wound coils for MS-matrixing - iirc, we run into strange issues because of inter-winding capacitive couplings..

Jakob E.

Cinemag said they can make it as a trifilar or quadfilar, will this improve anything?
I know next to nothing about transformers past a shallow understanding of what they do.


 

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