Insert balancing well under way but still need some info.

Hello,

I'm currently working on some schematics to balance the inserts on my studer mixing desks. I have found the perfect schematic for balancing (send) and debalancing (return) in a nice little pakage. It is used in a certain fadermodule of the studer. As I have to normal the inserts on the patchbay I would like to use a relay to activate or deactivate the insert so I can keep the signal path as short as possible and don't have to normal the patchbay itself, when I don't use the insert. The insert itself is unbalanced. So I would like to use a relay before the balancing and debalancing amplifier. Does anyone have any suggestions with regard to the best cirquit for this option. I have no experience with relays so every help is welcome.

By the way I have the schematics and bill of materials finished in free PCB for the balancing and debalancing . If someone want's to host it that would be great so everyone can use this for balancing their inserts. I think it's a schematic everyone could use. The schematic uses two NE5532N dual opamps. It's really small (like 5.5 cm on 3.5 cm) and uses +- 15Volts to power it.

Regards,

Geert

[quote author="Geert Heyrman"]I can keep the signal path as short as possible and don't have to normal the patchbay itself, when I don't use the insert. The insert itself is unbalanced. So I would like to use a relay before the balancing and debalancing amplifier.

By the way I have the schematics and bill of materials finished in free PCB for the balancing and debalancing . If someone want's to host it that would be great so everyone can use this for balancing their inserts.
[/quote]

Yep
no suggestions right now but there are a few 5532 balancing circuits about

and YEP
on the hosting thing
if you can do some text and are interested enough to drive the writing and reaseach I'll help with the web page and post it at the Factory.
This is a perfect project for the Factory as it is look at one of the neccessary BUT unglamorous parts of the studio

let me know
I'm easy to find

ps
you got that Studer A xxx multitrack ... yes/no ?
from Australia ... :wink:

You might have a look at these:








Oops! Sorry, I did see you were needing insert balancing.

Hi kev,

Yep I got that studer A820 MCH recorder from SBS radio in melbourne. It travelled the whole world to reach me but I'm really happy with it. I have to change the batteries so I can save the alignment data. I'm actually looking to buy some sparemachienes for parts so I will never run out.... But I can fully recommend it... They just don't make equipment like they used to.

With regards to the balancing design I'm thinking of making a website myself as I'm working on several little projects now. I'm also makin a PCB for the sesel 9k lineamp. I'll send you the schematic this evening anyway so you can give your blessing :grin:

Could anybody tell me if it would be wise to add a level potentiometer to the insert send and return? As I like my API 4312+ preamps a lot when driven on the edge I fear that I might distort the input of some effectdevices I have. lowering the level would solve the problem partly I fear. As i would lose a litlle character from a driven preamp. The same applies even more to my tubepreamps. Until yet I have not founds inserts with levelcontrols for send and return on a hardwaremixer. I know I can do levelcontrol on the effectdevices, but distorting the AD-converters is.... not what I'm after.... is there any advantage to include it on the balancing PCB itself?

regards,

Geert

The problem with effectdevices is that my desk is =6dBu but some of the equipment I have is ..... well semiprofessional - 10dBu or 4dBu.

Geert

Hi Geert,

What mixing desks do you have?


Kev- if this goes up on your website, would you put a little notice/link here so that we can go see it when it's finished?


Cheers,

T

Hi Tillman,

I have two studer desks actually. One 903 24 track with no master fader but four stereogroups that I feed into 4 stereochannels of my studer 904 witch has 24 monotracks and 8 stereo. So I have access to 56 channels. I like the desk a lot because it has a really neutral sound. When all channels are on and set to 0 DB I have a noisefloor of -83 db... This desk is awesome for playback. For character I'm obliged to use preamps to spice things up, but the micpreamps itself are also very nice, just not allways what I'm looking for.

I'll have to make 112 balancing amps :shock: if I want to balance all the inserts... hell of a job. On the other hand I'll be able to solder ciquits in the dark when this project is finished. I'm also considering to make balancing rackunits for my synths and other unbalanced gear and bring all my unbalanced rackgear up to +6dBu
Regards,

Geert

if any thing goes up at the factory a link is posted if the originator of the idea or page is ok with it
usually it does go on the thread that is most relavant

one day the front page will reflect what is underneath ... no rush at the moment to get that all working


as for trims on the insert returns

I think ALL inputs DAW and Desk will benefit from an interfacing unit.
This could be simple resistors or may stretch to a transformer coupled DI box thing.
NOT all DI boxes need to be aimed at Bass Guitars and Synths ... they can be line level.

for example
An Ai3 can't handle a great deal of level and if you do want to drive your API or N1290 up into the red then you need to provide a termination and a little level drop to enter the Ai3 without clipping

SO
a simple rotary switch with a couple of PAD positions and a trafo to unbalance can help to interface this high level retro gear with modern crap B desks and simple DAW interfaces etc

PS
congrats on the tape deck
but
bummer that gear like this ends up leaving my country
... this is one of the resons I am trying to make it possible that I can sell my Auditrionics to someone local who is capable of looking after them
and I think I have found someone

Do you have a particular need for balanced inserts, such as extremely long lines, noise interference, etc? Unless you have a problem, or an interface solution that requires a balanced line, you might consider letting it be. The additional circuitry will certainly change the sound more than the unbalanced line will, assuming a lack of a discernable problem with an unbalanced path.

I think a lot of people get caught up in the often stated 'superiority' of balanced line level signals. This is one of those places where ideal-theory and practical-reality can be pretty different. I hope you've considered the reality of your need carefully, before you go on an expensive and time consuming wild goose chase, that may not yield definite improvements. Maybe consider a halfway point, like a patchable set of balancing amps that live near the insert points. You could then use them with very long runs and particular noise or interface needs as they arise.

Good luck with it, whatever path you take.

Hi Doug,

The sound doesn't change a lot, actually I don't hear the change except for the fact that it's less noisier. I also don't have to add 6db of gain so I don't increase the noisefloor either. I know this because some of the faders I have in my desk have this exact schematic for balancing the inserts, but only the prefader insert. the prefilter insert stays unbalanced... So it's a studer design to start with. The thing is that my cableruns will be around 10 meters (5 meter to the patchbay and in general 5 to six meters to the effects and dynamics). I prefer keeping everything balanced so I'll definitely will proceed my goal to balance the inserts. The direct outs will suffer the same degree of DIY terrorism :twisted:

Regards,

Geert:

PS: I have sent Kev the schematic, when the pcb is finished I'll send him the files as well. It would be nice though if I could make gerberfiles.... but as allways I prefer investing in hardware above software so freePCB will be my platform for a long time I fear.

Kev,

Can you show a picture of your desk? Would like to see it as well as the channelelectronics :grin:

Geert

there is TWO desks going to the new owner
as for other tech stuff
.. I hope to work with him to produce some new DIY projects

tech drawings are on the factory site and a couple of pictures are on my very old personal site

Auditronics Stuff
Draft 1 - A draft copy of the re-typed, main text section of the manual
http://www.diyfactory.com/data/A501draft_text_only.pdf
Draft 2 - Section 6 - just a short list of the main schematics
http://www.diyfactory.com/data/A501draft_section_6_short_list.pdf


this was back in 2002
http://voyager.celestial.com.au/~rosswood/Studio/who_is_in_the_house_4.htm

this was way back in history when the desk was at Bake House ( later known as Silkwood)
with an unknown band called Skyhooks
http://voyager.celestial.com.au/~rosswood/images/skyhooks.gif

Man that looks nice and vintage. What desk will take its place?

Geert

the desks are '72 and '73
Quad ( stereo front and stereo fack)
T config
left centre right and one rear
left centre right is a tricky pan arrangement and can't be used in the normal left right mode
think the ProTools convergent and divergent pans


I'm going to try to survive without a desk

:shock:
extra I/O for the DAW and have everything on an interface with minimal patch panel

I am looking at some DIY gear with remote control and hopefully be able to load settings from software. Keep the settings in the same folder as the Song Session ... even better if I can get it inside the DAW software with Midi Sequence and CC data.

One of the first units should be an Auditronics mono and stereo EQ
both in front panel and software control
then perhaps a direrent look at the THAT2180/1 stereo comp.

think of the typical Practel sort of thing and then look at the Talia Broadcast Equipment. The second will give you a hint to who I hope to be working with on this project.