Volume attenuator question - Monitor Controller DIY

I need to make a simple Monitor controller...

What kind of rotary do I need for 12 step balanced stereo volume attenuator? 2 or 4 deck rotary?

I found some 2 decks here
http://www.banzaieffects.com/Rotary-Switch-2-level-1x12-pr-20274.html

I will do it based on this great page http://www.euronet.nl/~mgw/background/attenuator/uk_attenuator_1.html#excel



BTW, does the Mackie Big knob really degrade the sound? A few friends have it and they are satisfied with this thing.

For stereo balanced signals, you'll need a four deck switch. Also, try to get precision tolerance resistors, or do some matching with an ohmmeter, since any imbalance in attentuation between the positive and negative legs of your balanced signal will introduce some noise.

I build this(unbalanced, though), which I am very happy with:

http://i13.photobucket.com/albums/a253/slapback/passive_router_sch_rev_d.jpg

Cheers :guinness:

Lars

Are you sure you need balanced? Unbalanced would be sooo much simpler..

Jakob E.

OK. Thanks for the tip :thumb:

Now, my next question is: where do I get nice and cheap 4 deck 12 or 24 rotary steeped rotaries? :wink:

[quote author="gyraf"]Are you sure you need balanced? Unbalanced would be sooo much simpler..

Jakob E.[/quote]

I don't know actually. From the controller I would have max about 4m long cables to the 2 sets of active monitors. Can somebody please explain if balanced is really needed here and why. :roll: :?:

I would try unbalanced first, and only run balanced if that caused noise&trouble. And I don't think it will, if you keep attenuator impedances moderately low, say 2.5-5KOhm.

All monitoring in our facility runs unbalanced (in decent-quality Mogami cables, nothing fancy though) and dosen't cause trouble..

Jakob E.

Sounds good. Now I just need to figure out the thing with attenuators impedance (2.5-5KOhm). To be senciere I have no clue about this yet. I think I will need help from someone to get me the right resistor values for 12 or 24 steps in this impedance range. Jacob? :roll:

I got these links from Jakob a while ago - schould be what you are looking for -->

Calculator:

http://www.quadesl.com/attenuator.html

Switches:

http://www.uraltone.com/kauppa/index.php?cPath=15_53

Lars

Thanks Black Dog! :thumb:

[quote author="Purusha"]Thanks Black Dog! :thumb:[/quote]

No problem - just remember to show us the result :grin:

OK, another question.

1. If I wanna make the >DIM< option what do I have to put in the signal path? Probably a resistor but what value for -10 or -15db ? What is a usual diminished value used in db?

2. Another thing is, if I wanna make the >MUTE< button, do I just cut of the signal or should I put some stronger resistance there to avoid pops and clicks?

I am pretty dumb when it comes to certain things in DIY so you'll have to forgive me if this sounded like very dumb questions.


My chain for unbalanced controller will go like this:

1. 3 x INPUT SELECTION (2x6 rotary)
2. DIM (push button + dual relay)
3. MONO (push button + dual relay) based on the New York Dave's schematics
4. MUTE left (push button + single relay)
5. MUTE right (push button + single relay)
6. MUTE ALL
7. VOLUME ATTENUATOR (1x12 DUAL LAYER rotary)
8. OUTPUT SELECTION (2x6 rotary)
9. EXTRA VOLUME ATTENUATOR FOR LOUDEST MONITORS to make the same level on both active monitors. This may not be needed at the end.
10. VOLUME ATTENUATOR FOR SUB MONITORS + SUB MUTE push button with dual relay

What do you think? Any suggestion or comment is most welcome.

This is the mono schematics suggested by NYD

Another dumb question :grin: what does the >total resistance< in the java calculator http://www.quadesl.com/attenuator.html stand for? I don't know how to use it properly :?

A while back, I had the DIY idea for a Monitor section as well.
But after calculating all the parts ( case, compnents, labeling, wiring, etc) I decided to buy the Cranesong Avocet , If I remember well I paid 1400 euro or so.
IMO, well spend, considering the features and the excellent sounding DA's.
I doubt you will save half of that amount if you DIY this project.

Hi Purusha, check out www.goldpt.com they sell the raw attentuator as well in most formats. afaik, the impedance isn't critical for monitor outs so your dim could be a 10 or 20k load that can be put in series at the top of your controller which is quite easy.

Andy

[quote author="andre tchmil"]........ , If I remember well I paid 1400 euro or so.
.......[/quote]

A Cranesong Advocat costs more than 3000 euro here in the Netherlands....

[quote author="andre tchmil"]A while back, I had the DIY idea for a Monitor section as well.
But after calculating all the parts ( case, compnents, labeling, wiring, etc) I decided to buy the Cranesong Avocet , If I remember well I paid 1400 euro or so.
IMO, well spend, considering the features and the excellent sounding DA's.
I doubt you will save half of that amount if you DIY this project.[/quote]

I estimated my controller for 150? in parts as max. There is nothing very expensieve inside. A few relays, switches, resistors, few caps and 5532s and a nice 1U rack case which I will design in no time.

[quote author="Purusha"][quote author="andre tchmil"]A while back, I had the DIY idea for a Monitor section as well.
But after calculating all the parts ( case, compnents, labeling, wiring, etc) I decided to buy the Cranesong Avocet , If I remember well I paid 1400 euro or so.
IMO, well spend, considering the features and the excellent sounding DA's.
I doubt you will save half of that amount if you DIY this project.[/quote]

I estimated my controller for 150? in parts as max. There is nothing very expensieve inside. A few relays, switches, resistors, few caps and 5532s and a nice 1U rack case which I will design in no time.

BTW, Andre, what happened to your 50 custom cases you were asking some time ago?[/quote]

Didn't find the time yet to make a proper Layout , but hey winter is coming so expect my order in a few months from here.

OK, I am back at my monitor controler DIY :green:

One question. For DIM option, is 10K or 20K in series enough or do I have to make a link with 1K to the GND after the 10K resistor as well?
This is something I saw in this photo...

[quote author="Purusha"]OK, I am back at my monitor controler DIY :green:

One question. For DIM option, is 10K or 20K in series enough or do I have to make a link with 1K to the GND after the 10K resistor as well?
This is something I saw in this photo...
[/quote]

Without the 1k resistor you will only have about -6dB attenuation for a 10k dropping resistor or a little less than -10dB for 20k. With the 1k resistor you'll get about -22dB for 10k or about -27dB for 20k. This is assuming zero source impedance and infinite load impedance.

You could use a larger dropping resistor, but then the circuit impedance is getting a little high. The 1k connection would require more contacts on a switch or relay, but the cost difference is small. The main thing you need to decide is how much attenuation you want for the dim switch.