studer 900 eq in 500/51x series. Possible?

[Larsson]

Hi guys.
Im about to start a 3 months electronics project in school. I was thinking about taking the 900 EQ and stuff it in a 500 or 51x format. I would use the 900 line input stage --> EQ --> some line output amp . There are however -6V and -24V rails for some logic and switching. I guess i could cut out the -6 volts but im unsure of the -24V. For me some parts of the circuit are yet quite difficult to understand  ???.  Has anyone thought about doing this earlier and would like to share some knowledge?  The main reason im doing this is to learn Altium Designer and also try to understand the 900 circuit better.  The schematics can be found here:ftp://ftp.studer.ch/public/Products/Mixing_Analog/900/Manuals/900_Op_Serv.pdf on page 199-201.
Thanks! // Larsson

 

[[silent:arts]]

If you go with the GDIY51X format you have the -24V available.
If you need -6V just regulate down from the -16V.

 

[Larsson]

If you go with the GDIY51X format you have the -24V available.
If you need -6V just regulate down from the -16V.

Yes i could do that. I dont understand the function of this section with cmos and ppnp transistors. Anybody got a clue?
https://www.dropbox.com/s/nock1ufvfqu7b2g/linetransistors.jpg?dl=0

 

[taram101]

I dont understand the function of this section with cmos and ppnp transistors. Anybody got a clue?

Electronic switch for input select. You don't need it if you are using only line input. 

 

[Larsson]

I dont understand the function of this section with cmos and ppnp transistors. Anybody got a clue?

Electronic switch for input select. You don't need it if you are using only line input.

Thanks. Thats what i suspected. As of now it seems i can get rid of the -24 and -6V rails. I do some more research tomorrow.

 

[Brian Roth]

A quick glance at the schemos seems to indicate the -24 rail is used just for the various FET switches.  In a 500 module, those functions should be easy to replicate with hard switches (mini toggles, whatever).  I may have overlooked other uses for the -24 rail, so double check.

The -6 rail seems to be associated with various LED functions, and that rail can be easily "derived" from the standard -15 rail in a 500 frame using a 3-terminal negative regulator (LM337 or a 7906).

I don't think it will be a problem, but you need to ensure the total current draw for each rail in the 500 rack falls below the maximums specified in the VPA spec.

Bri

 

[Larsson]

A quick glance at the schemos seems to indicate the -24 rail is used just for the various FET switches.  In a 500 module, those functions should be easy to replicate with hard switches (mini toggles, whatever).  I may have overlooked other uses for the -24 rail, so double check.

The -6 rail seems to be associated with various LED functions, and that rail can be easily "derived" from the standard -15 rail in a 500 frame using a 3-terminal negative regulator (LM337 or a 7906).

I don't think it will be a problem, but you need to ensure the total current draw for each rail in the 500 rack falls below the maximums specified in the VPA spec.

Bri

My idea was to use  potentiometers with pull switch in every position.  That would also minimize the amount of toggle switches and end up in a nicer layout. The studer 900 uses this in the parametric bands to adjust Q. As far as LEDs go i thought of having three leds G/Y/R showing input signal and one red indicating overload on the output. Thanks for the input!