RS127 RS135

[Lee_M]

I remembered also that they also have a Big passive EMI equalizer unit.

It is the same as this one but it's green and not white:

Let me know if you need pictures , measurements, etc...

I would love to see some more pics of that unit, It looks pretty funky.

 

[Whoops]

Its quite big and I remember the back was open, its just front panel and electronics as far as I remember.

As it's passive we used a preamp channel on the console for the return as makeup gain

 

[ruffrecords]

I remembered also that they also have a Big passive EMI equalizer unit.

It is the same as this one but it's green and not white:

Let me know if you need pictures , measurements, etc...

That would be extremely interesting. I feel sure it has a very similar pedigree to the other EMI EQs so its topology should also be very similar. I don't suppose you can lay your hands on a schematic?

Cheers

Ian

 

[Whoops]

That would be extremely interesting. I feel sure it has a very similar pedigree to the other EMI EQs so its topology should also be very similar. I don't suppose you can lay your hands on a schematic?

Cheers

Ian

Sorry I don't have schematics, it's a really old unit, it was bought from EMI in the 60's.
What I can do is take some pics of the insides and do any measurements you'll like.

 

[thomasdf]

Very intesting topic! Eager to read & learn more!
Thanks guys

 

[Goodizzy]

I am also interested to see any pictures!

 

[ruffrecords]

Sorry I don't have schematics, it's a really old unit, it was bought from EMI in the 60's.
What I can do is take some pics of the insides and do any measurements you'll like.

OK, understood. Some pictures of the inside would be good so we can work out if iy uses tapped inductors and maybe see the values of some or all the caps. If you could possibly measure the inductor values that would be a great clue  for working out the schematic. Lastly a hi res picture of the front panel to give me a list of the frequencies and dB steps.

Thank you very much for offering to do this.

Cheers

ian

 

[ruffrecords]

I found this manual for the software plug in version which gives some clues about the shape of the bands:

http://www.waves.com/1lib/pdf/plugins/rs56.pdf

Cheers

Ian

 

[Whoops]

OK, understood. Some pictures of the inside would be good so we can work out if iy uses tapped inductors and maybe see the values of some or all the caps. If you could possibly measure the inductor values that would be a great clue  for working out the schematic. Lastly a hi res picture of the front panel to give me a list of the frequencies and dB steps.

Thank you very much for offering to do this.

Cheers

ian

I will do that.
I guess is the same unit, the one at the sutido is Green, it appears in the book " Recording the Beatles : The Studio Equipment and Techniques Used to Create Their Classic Albums ".
It's strange that I can't seem to find any pictures of the unit on the web. The closest one is that white unit I posted.

I never measured inductance, How can I do that?

I have a Fluke 179 multimeter but on the specs I dont see inductance metering

 

[thomasdf]

To my knowledge, you need a inductance meter to measure inductors, capacitors etc
If you are able to make 100% accurate measurements that leads to cloning this beast, I'd be 100% happy to organise a fund collect to offer you the measurement tools you'll need.
I have been dreaming of building an EQ like this one for years.
The RS56 plugin is actually quite good for a plugin, but the real deal must be awesome...
It looks like a huge project, but I am so down for it!

 

[Lee_M]

I found this manual for the software plug in version which gives some clues about the shape of the bands:

http://www.waves.com/1lib/pdf/plugins/rs56.pdf

The plot thickens!

I'm extremely interested to get a vague idea of what the rotary switches are doing, If this is a constant-Z EQ (I'd guess so, if it was happy feeding a low-z mic input) then I'd expect the "curve" and "frequency" switches to be very complex.

My understanding is that the different bell curves would each require different values of capacitance and inductance (both shunt & series) for each band, So I'd expect a fair few multi-tapped inductors and non-standard value (or parallel) caps inside the unit.

@Whoops
Measuring inductors in circuit is tricky. 
I have a marconi TF2701 "in-situ universal bridge" which is apparently capable of measuring components in circuit, But I haven't needed to use that capability yet. It's a very handy tool for other purposes too, If a little confusing to use at times.
I picked it up for fairly cheap (£30 or so) on ebay.

Where in europe are you located?
I don't know how widespread marconi gear is where you are, but I'd expect there to be similar items from other manufacturers available in your country.
Perhaps some other members on here can recommend alternatives.

 

[Whoops]

To my knowledge, you need a inductance meter to measure inductors, capacitors etc
If you are able to make 100% accurate measurements that leads to cloning this beast, I'd be 100% happy to organise a fund collect to offer you the measurement tools you'll need.
I have been dreaming of building an EQ like this one for years.
The RS56 plugin is actually quite good for a plugin, but the real deal must be awesome...
It looks like a huge project, but I am so down for it!

Well it's a passive EQ, theres Switches, Wire, Inductros and Capacitors inside.

I'm sure I can make 100% accurate measurements

 

[Whoops]

I see that Peak have an Inductance/Capacitance meter:
http://www.peakelec.co.uk/acatalog/lcr45.html

The problem is that it doesn't measure inductance in circuit.

I'm located in Portugal

 

[Lee_M]

I see that Peak have an Inductance/Capacitance meter:
http://www.peakelec.co.uk/acatalog/lcr45.html

The problem is that it doesn't measure inductance in circuit.

I'm located in Portugal

Another issue with the peak LCR45 is the 10H range limitation, It likely wouldn't be a problem for measuring the inductors in the RS56 (those should be fairly small values) but it could definitely get in the way of other uses.

 

[emrr]

Flashing back to that RCA, note it says 'strapping' on many of those taps and that's what the additional pictures show, they're not on the switch. 

I have a LPF from that same Photophone film line, looks exactly the same on the outside, which consists of 3 separate potted H networks, one for each of the 3 frequencies offered, and a switch between them.  There are other combos of BPF, stepped HPF, etc.  The ones I've measured all have very steep slopes, with the usual constant-K uptick after the majority of the slope. 

Complementing those on the theater install side is an EQ that is entirely straps rather than controls, for room correction, those are quite common.   

 

[ruffrecords]

I see that Peak have an Inductance/Capacitance meter:
http://www.peakelec.co.uk/acatalog/lcr45.html

The problem is that it doesn't measure inductance in circuit.

I'm located in Portugal

I think this will probably be fine. Most passive EQs use series resonant circuits so you have a C and an R in series with the inductance. Most inductance meters should be able to cope with this situation without becoming confused especially if we measure at maximum boost where the resistance should be highest. Measuring individual taps might be more difficult.  Alternatively, if you were to set the frequency to the highest value this should select the first tap on the inductor. The other taps should then be floating and could be measured directly. Definitely worth a try.

Another approach is to work out the capacitance used at each frequency setting from which the required inductor can be  calculated - this is how I did the Helios 69 EQ.

Cheers

Ian

 

[Whoops]

I will take the pictures Ian,
But I don't have any way of measuring inductance.

 

[ruffrecords]

I will take the pictures Ian,
But I don't have any way of measuring inductance.

OK, let's start with pictures. I am sure we can find a way of getting you the right tool to measure inductance later.

Cheers

Ian

 

[leadbreath]

go Ian go!! go Ian go!! go Ian go!! etc..etc..

 

[leadbreath]

do your magic Ian!!  if you can add this EQ to your arsenal it would be fucking awesome!!!