homemade monitor switch

im gonna make a monitor selector with 3 inputs and three outputs
any way heres my design, i dont know how to draw schematics, but heres the idea,
tell me what you think





heres my make shift schematics




what parts and switches would i need, can you give me links

you should point to point that. :thumb:

If you skip the two meters you can make a totally passive monitor switcher.
In that case you'll need:

One 2 pole (1 deck)3 position rotary switch for the input selector
0ne 2 pole (2 deck)24 position rotary switch for the mastevolume control
one 2 pole (1 deck)3 position rotary switch for the ouput selector

Here a nice site to get some insperation from...

You can also buy your Elma switches without the little pcb's or buy cheaper rotary switches like Lorlin for example although you'll need at least one Elma for the master volume...

EDIT: Changed both input and uotput selector switches to 2 pole instead of 1 pole....

I was thinking of doing this a little while ago, but a friend told me that it wouldn't be good for the power amps. Regular preamps have buffer stages. Is it really that big of a deal and what do the monitor stages of consoles look like? Are they passive or do they have buffer stages in them?

One 1 pole (1 deck)3 position rotary switch for the input selector
0ne 2 pole (2 deck)24 position rotary switch for the mastevolume control
one 1 pole (1 deck)3 position rotary switch for the ouput selector

Click to expand...

Surely you`re thinking in mono here for the input & output selector switches !!! Shouldn`t they be 2 pole switches.

[quote author="Rob Flinn"]

One 1 pole (1 deck)3 position rotary switch for the input selector
0ne 2 pole (2 deck)24 position rotary switch for the mastevolume control
one 1 pole (1 deck)3 position rotary switch for the ouput selector

Click to expand...

Surely you`re thinking in mono here for the input & output selector switches !!! Shouldn`t they be 2 pole switches.[/quote]

Oops

Brian Roth gave an interesant information for wiring this type of thing:
http://www.groupdiy.com/index.php?topic=148829#148829

Some thoughts:

- you might wanna include a mono switch.
- a mute and/or dim switch might be handy, too.

Handling could be improved if you put the volume pot into the lower area. Put the individual volume pots into the upper area. In normal use you don't need them that often. On most monitoring controllers those are trimpots.

I would skip the meters. They're not that useful unless they are very accurate and calibrated to match your DAW meters. Of the usual monitoring controllers only the Presonus Central Station has really good metering. It has a digital input and can thus be calibrated to the internal DA-converters. On most other controllers the meters are just some visual feedback, but for actual information you really have to watch the meters in your software.
Plus, as was said before, your box can be entirely passive without the meters.

That said, there is a pretty okay controller box by SM Pro audio. To be honest, I'm not a big fan of their stuff, but the M-Patch does what it's supposed to do, it is entirely passive, and even the volume pots are of decent quality. BTW: You need a 4-layer pot for a passive ballanced volume control.

JimY from the SOS forums put together a nice little pdf here on a "simple" monitor switch
http://hometown.aol.com/AshdaleStudio/Ashdale+PMC.pdf

[quote author="Rossi"]. BTW: You need a 4-layer pot for a passive ballanced volume control.[/quote]

If going balanced you'll need 4- layer (4 pole, 4 deck..whatever) switches also for input and output.

A 4 pole 24 position Elma is going to cost you ......ouch :evil:

Make it active / balanced / floating. Don't use switches on signal path, or just short the unselected inputs to ground (via R) using a (mechanical or electronic / FET / bipolar / whatever) switch.

Alternatively make it passive but use patch chords and design with retro analog synth look. Put some xformers inside (helps keeping the grounds separated as well), maybe with a multiple outputs to adjust the output levels.

I have been thinking about a similar project based around an old A/IO/B monitor switch box that is surplus to requirements. It features one heavy duty switch and knob on the front and three 15-pin monitor sockets alongside three PS/2 mouse/keyboard ports. I figure I can ignore the PS/2 ports and use the box by wiring up three multi-core cables with 15-pin plugs at one end and three pairs of RCA jacks at the other. As the cables that can be found attached to abandoned computer monitors are designed for digital data transmission I presume that they will be inadequately sheilded for audio signals, although I might make a point of carrying a pair of cable cutters around with me for the next few weeks.

The advantage of this system would be that as I am using two sets of passive monitors connected to two separate amplifiers (A: Audio Research/Yamaha B: Wharfedale/Pioneer) I can feed three sets of inputs on each amp from a common source. Currently unconnected RCA jacks tend to hover around the back of my mixer.

the more complicated it get the more I think it needs to be remote controlled so the signals stay in the main equipment racks

http://www.diyfactory.com/

obviously still a work in progress but the DAW Monitor Switches will live here

http://www.diyfactory.com/projects/dawmonswitch/dawmonswitch_1.htm
http://www.diyfactory.com/projects/dawmonswitch/dawmonswitch_2.htm
http://www.diyfactory.com/projects/dawmonswitch/dawmonswitch_3.htm
(I'll see if i can fix the links to the pictures on 3)

and number four will be a Single chip type solution like the PGA2310 or one of the otrher zero crossing volume control chips.

PIC is popular and some of the magazines have done motorised fader/volume thingos
http://www.siliconchip.com.au/cms/A_30559/article.html

Kev,

quick suggestion for you.

MSP430F2003 - low pincount MSP430 with an ADC on board to measure your volume pot position.
PGA2310 - Digitally controlled volume control

you could quite easily clock out in SPI a value for 2x7segment displays and update the attenuation on the PGA2310.

Maybe a small relay driver for channeling the audio around the board.

cheers

R

> It features one heavy duty switch and knob

The usual run of cheap mechanical KVM switches are NOT "heavy duty". I'm rather disgusted by them. However, in low-level audio the poor contact and possible short-between may do less damage than I've seen on keyboards.

The electronic switches probably won't handle audio (or they might, but it will be lo-low-Z and unidirectional).

> I figure I can ignore the PS/2 ports

If you do go there, bypass the diodes used to leak power to the idle keyboard/mouse.

> the cables that can be found attached to abandoned computer monitors are designed for digital data transmission...

Actually, 15-pin VGA signals are analog. Yup, digital inside the video card but the 15-pin is fed from the output of a DAC. At the time, that was the most practical way to handle things. Anyway, inside a VGA monitor everything is analog: slewing the grid-cathode voltage on an electron gun.

You don't get digital on the wire until you get to the new-fangled DVI connectors, and sometimes not even then (some have analog signal, and some "DVI" monitors really use the analog signal). DVI makes sense in LCD displays, which often want digital going to the LCD panel drivers; but analog VGA is so ubiquitous that most LCD displays have the ADC converter anyway.

> I presume that they will be inadequately sheilded for audio signals

I think you will be cool in any EMI environment where you'd want to have fine audio on RCA plugs. Leakage "out" of the cable degrades the super-fast video, so even low-grade video cable is usually "air-tight" at audio frequencies.

If you ran a mile of video cable, you could have loading issues, but the amount you will get with wirecutters in the junkroom won't be long enough to hurt.

That stuff is sometimes very un-fun to strip and terminate.

Thanks, PRR. That's good advice. As my needs are modest (and am currently building a SoundLab mini synth and bearing the consequential financial burden) I think I shall try chopping a few cables off abandoned monitors. I seem to see several being chucked out every week around my estate.

I'd like to build something similar to this, and the Ashdale pdf looks like a good starting point. I'd like the 3 switchable inputs and 3 switchable speaker outs, but I'd also like to have an always active headphone out and an always active 2-track passthrough output. How could I work this into the aforementioned designs?

Sorry for the super-newb questions.

Ok, I found this Jensen 2-way splitter design:

http://www.jensen-transformers.com/as/as041.pdf

Will this work in the following application? Is there a more efficient/cost-effective solution? Just trying to think outside the box... (baaaad pun, I know.)

I built this unit for my friend/client Dave Gardner, who operates Magneto Mastering in Minneapolis:

http://www.brianroth.com/projects/gardner/monitor-control.jpg

The primary signal path is totally passive. The "input" switch is a 12 pole Electroswitch. Each of the three stereo inputs requires two poles per channel. , hence the need for 12 poles. Any unused input is terminated into 1200 Ohms since the entire system was designed as a 1200 Ohm load fior the sources. The Shallco stepped attenuator is also a custom 1200 Ohm unit.

The "output" switch is also an Electroswitch 12 pole part. Each output tip/ring pair requires two switch poles per channel since any unused "destination" is shorted to avoid crosstalk.

Active circuity is required for the "mono" listening mode as well as for the meter buffers.

If I did this sort of gizmo again, I would be tempted to use relays.

Bri

You can find some stuff at the DIY Factory

... the relay unit is based on Mikkel's balanced relay board ... 64/63 steps
do a search and you'll find

then there is the Texas chip which is very cool and accurate ... levels wise ... accurate sound well you can decide that