Advice with adding direct outs to my Pye Discrete Mixing console.

Hi Guys,

  I need to add some direct outs to my Pye console. Firstly, I want to use individual channels as inserts in Protools, and perhaps (if they are quiet enough!) to enable me to record with it. This desk has a very noisey mixbus, due in part to the fact thqt it is only screened with plywood! the output of each channel is very low, perhaps as low as -40dB, but I haven't actually measured it accurately. I am tempted to just slap a 5534 in, since they wont draw that much current, but don't know how to approach this with only a +24v rail. `i have read of disadvantages with both inverting and non-inverting, and would welcome any advice.
  I am equally tempted to build something discrete and appropriate, but I am worried about smoking my power supply! I was thinking about Neve ba440, since it is Class AB. Normally, the load will be approx 10k, but I must be able to run comfortably into 'Tools at 18dB over. I have room to accommodate an output tranny, since I would like it to be balanced.

  `many thanks,


        ANdyP

Before attempting any mod, you must assess the situation. You need to know the gain structure of the channel. What is the gain of the mic pre? Is there any subsequent attenuation (passive EQ?), is there a post-fader amp? Then you will decide where to put gain and how.

HI,

  I don't have schematic here. EQ is passive. I am certain there is no post fader amp. I would probably like to make direct out pre-fader. If current draw were not a potential problem, i would like to have the option of both pre and post. I do not want to add a switch for this, rather use two separate line amps if possible, even if one is not balanced. there are 3 spare blank XLR cutouts on each module, so no worries there.I do have a spare Coutant/Neve 24v psu, so I could always up my supply to two psu's(?)


    KIndest regards,

 
        ANdyP

strangeandbouncy said:

HI,

   I don't have schematic here. EQ is passive. I am certain there is no post fader amp.

Click to expand...

No wonder the high bus noise. It looks like a major mod.

I would probably like to make direct out pre-fader. If current draw were not a potential problem, i would like to have the option of both pre and post. I do not want to add a switch for this, rather use two separate line amps if possible, even if one is not balanced. there are 3 spare blank XLR cutouts on each module, so no worries there.I do have a spare Coutant/Neve 24v psu, so I could always up my supply to two psu's(?)
    KIndest regards,
ANdyP

Click to expand...

I think you should use simple non-inverting one-opamp stages with adjustable gain. You could build that as a dual unit (one for pre-fade, the other post-fade), using a 5532. The added consumption would be around 12-15mA per channel. I don't know if you have enough headroom on your PSU to withstand that, but you can use two PSU's, splitting the power rails. You don't really need these outputs to be balanced. They could be impedance-balanced; it is done that way on many mixers, nobody really complains.

Hi,


  thanks! I'll get round to it soon(ish!)


  ANdyP

Hi,


  could someone point me in the direction of an "Impedance Balanced" output circuit diagram? I have failed so far on da webbage . . . . or let me know what devices employed such a setup . . . . ?

 

    Many thanks,


      ANdyP

Hi,

Check this page out-

Douglas Self Balanced Line Technology

It's the second circuit down from the first one the link brings you to.

Sounds like an interesting project!

Mark

Hi Mark,


  Oh yes! it certainly is! absolutely awesome passive eq, using NO inductors. All capacative! Amazing sounding pre's, but at the moment, it is rather noisy . . .


    Many thanks,


      ANdyP

Also,

Top of page 3 of this pdf-

Jensen AN003 Balanced Interconnection

strangeandbouncy said:

This desk has a very noisey mixbus, due in part to the fact thqt it is only screened with plywood!

Click to expand...

Surely pyewood? Watch out for woodworm hole resonance effects that can really sap the HF...



What are the output bus drivers on this Pye?

Cheers,

Mark

Hi Andy,

Sounds great- I've worked (repairs) on some of the smaller PYE desks, and love their design.

Hope these links are useful to you.

Mark

Mark,


  arf arf! The mix bus amps and output drivers are just what you would expect, substantial, discrete, and with huge output trannies. this desk SOUNDS outrageous. Possibly the most musical eq I have ever heard . . . . it is just too noisy as is . . . . Also, with modern "recall everything-at-the-touch-of-a-button" pressures, I want to be able to use the(switchable) 16 eq's as Protools inserts which I can't at the mo'.


  just to show off . . .

http://img.photobucket.com/albums/v692/strangeandbouncy/56-1.jpg

http://img.photobucket.com/albums/v692/strangeandbouncy/57-1.jpg

http://img.photobucket.com/albums/v692/strangeandbouncy/58-1.jpg

That looks shockingly/i] lovely,

I was going to ask for pics!

;D

Mark

Mark,

 this desk is some kind of hash up made from the components of the smaller SM8 console. My guess is that some TV company built it as a 20ch (16 mono/2 stereo) 4 group desk. It has amazing cabling and stage boxes marked as OB truck . . . As such, it sucks, since as you swap from between the two stereo busses, the gain structure changes! - Doh! I think that they put it away in the stores when they realised that it didn't do what they wanted, and forgot about it. iT was completely virgin when I GOT IT. All the vu bulbs(which are soldered in!) worked, - and they all failed in about 3 months! no greasy finger marks, not paint wear.

  there are plenty of blank xlr sockets on each channel, and ideally i would like to add direct out of mic pre, direct out pre(post eq) and post fader on each channel. I have nothing in my studio that has as low as a 600 ohm input, and will probably use desk as eq inserts into protools, and occasionally as preamps into protools. So only need to drive 10k over perhaps 2 metres.

  I would be so grateful if you have any insight/advice . . . .


    Kindest regards,


       ANdyP

I do have full manual/schematics(not here right now), and would far prefer to add something discrete to something chippy . . . Neve BA284?

Ha,

was about to post "what we could do with here is a schematic or block diag..."

...stopped in my tracks!

...Check your mail BTW,

Mark

Andy,

Did you start this project rolling?

Let us know how you get on!

Mark

Hi Mark,



  Still waiting to get my schematic back from my chum. I think that something based on the original Pye amps would be best, In the mean time, I am going to lash some 2520's on a couple of channels to see how it sounds. I have 'em knocking around doing nothing. If I cannot do something Pye-ish, I am considering something based around the Neve ba 284. Small part count sounds good. It wil be driving 10k inputs to 'Tools.


  Just had cataclysmic tax demand, so I will have to take a DIY sabbatical in the short term at least . . . .


    Kindest regards,


      ANdyP

strangeandbouncy said:

Hi Mark,



   Still waiting to get my schematic back from my chum. I think that something based on the original Pye amps would be best, In the mean time, I am going to lash some 2520's on a couple of channels to see how it sounds. I have 'em knocking around doing nothing. If I cannot do something Pye-ish, I am considering something based around the Neve ba 284. Small part count sounds good. It wil be driving 10k inputs to 'Tools.


   Just had cataclysmic tax demand, so I will have to take a DIY sabbatical in the short term at least . . . .


    Kindest regards,


       ANdyP

Click to expand...

I've just sent you by email the complete schematic of a channel (5534 opamp + out transformer).

Pier Paolo

HI Pier,


  I just picked up your email. I am so very grateful to you for this. Thank you so very much indeed! Although I was thinking of a temporary solution ,I suspect that this will happen to  all 16 channels! - time and money not withstanding. I hope that it it useful to others too!


    Thanks again.


    ANdyP

Just stumbled over this thread. Now I'm curious about this "most musical" EQ. ;-) Are the schematics online by any chance?