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chucky3042

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See my post in

 

MidiMagic

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One item: On any mono recording, you have to ignore the content of the vertical part of the groove. Manufacturers did not control for noise in the vertical direction.

The MONO switch shorts the two stereo channels together, eliminating this noise.
 

chucky3042

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Nostalgia corner

Just found this picture tonight, not sure if I posted it previously but its the very first analogue hardware version of the surround master way back around 2008. I see that I stole a few chips from the middle. It worked fine but there was a weird low level whistle coming from the VCA chips........never did fix that until the DSP.

1596116901745.png
 

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esimms86

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Nostalgia corner

Just found this picture tonight, not sure if I posted it previously but its the very first analogue hardware version of the surround master way back around 2008. I see that I stole a few chips from the middle. It worked fine but there was a weird low level whistle coming from the VCA chips........never did fix that until the DSP.

View attachment 54604
Very cool, thanks for sharing the circuit board porn. So version 2 really is a chip off the old block 🤔.
 

Sonik Wiz

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Nostalgia corner

Just found this picture tonight, not sure if I posted it previously but its the very first analogue hardware version of the surround master way back around 2008. I see that I stole a few chips from the middle. It worked fine but there was a weird low level whistle coming from the VCA chips........never did fix that until the DSP.

View attachment 54604
Circuit geek that I am, may I ask what VCA's you were using? The ones from THAT CORP is the best I know of. And how did you do RMS/LOG sensing in analog?
 

chucky3042

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Circuit geek that I am, may I ask what VCA's you were using? The ones from THAT CORP is the best I know of. And how did you do RMS/LOG sensing in analog?
Hey Sonic

We used the Analogue Devices SSM2164

As I said it has a low level weird whistle about it. Cannot find the schematic on the log conversion but it was a opamp diode thing, the averaging on that proto was not RMS (it is now via DSP)
 

DuncanS

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Hey Sonic

We used the Analogue Devices SSM2164

As I said it has a low level weird whistle about it. Cannot find the schematic on the log conversion but it was a opamp diode thing, the averaging on that proto was not RMS (it is now via DSP)
I designed some circuits using (pre-ADI ownership) SSM (Solid State Music) op-amps, great amps, with very low distortion, wide bandwidth with good gain, which was what I wanted. But if you didn't put a capacitor across the differential inputs (as per their datasheet/App Note) it would oscillate. Never found out why!
Edit: I was just wondering if I still have the datasheet up in the loft with the rest of my stuff from my PhD. Now I'm curious I'll have to have a look.
 
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