I'm building a passive monitor controller.

[Cojo]

Okey, I'm not near done yet but I have put together some slutty computer picture of the unit for you to watch. Remember this is just a hint of what it would look like. The final version may differ a bit but the function would be pretty much the same.

I don't want to post any schematics yet since I'm not shure it would work correctly.

Have a great weekend!

/Cojo

[h2000]

Well it sure does look gorgeous!
Do you make the box or is that an off the shelf enclosure?

[Rep]

Are you using resistors. Ladder, and Shunt type stepped attenuators ,
fully assembled, as kits, and do it your self ... ect ?

here are some good resistor kits http://www.goldpt.com/prices.html

[ulysses]

I think the volume knob is the most difficult part of a monitor controller to implement correctly, and it's also the least necessary. Experienced engineers will talk about how much easier things got for them when they started using a calibrated monitor volume level (typically 0dbu=85dBSPL). If your monitors are always the same volume, then you will grow accustomed to knowing how loud things should sound in your mix. From there, it proves useful to have a "crank it up" setting so you can (briefly) hear the mix at full volume, as well as a "threshold of hearing" setting where you can hear what the last elements to disappear are. That setting is useful when the phone rings too, of course. So if I were building a monitor controller (which I will probably do at some point), I will probably omit the knob entirely and instead just have a few switches for a handful of useful positions. I'm curious to hear what other think of this idea. At the very least, it's a good way to break yourself from the common nervous habit of constantly making tiny adjustments to the volume control, which I have been known to do.

[Cojo]

Originally Posted by h2000

Well it sure does look gorgeous!
Do you make the box or is that an off the shelf enclosure?

Thanks!

I will probaly make the box myself because I havn't found any good boxes on the market that are in the right sizes. It's so hard to find decent slope shaped boxes (all enclosures are 19" for some strange reason?) but if I find one I will for shure add the wodden sides!

Originally Posted by Rep

Are you using resistors. Ladder, and Shunt type stepped attenuators ,
fully assembled, as kits, and do it your self ... ect ?

here are some good resistor kits http://www.goldpt.com/prices.html

I am using a series stepped attenuator simular to those on Goldpoint but I have calculated my own resistors so I get the steps that I want.

Originally Posted by ulysses

I think the volume knob is the most difficult part of a monitor controller to implement correctly, and it's also the least necessary. Experienced engineers will talk about how much easier things got for them when they started using a calibrated monitor volume level (typically 0dbu=85dBSPL). If your monitors are always the same volume, then you will grow accustomed to knowing how loud things should sound in your mix. From there, it proves useful to have a "crank it up" setting so you can (briefly) hear the mix at full volume, as well as a "threshold of hearing" setting where you can hear what the last elements to disappear are. That setting is useful when the phone rings too, of course. So if I were building a monitor controller (which I will probably do at some point), I will probably omit the knob entirely and instead just have a few switches for a handful of useful positions. I'm curious to hear what other think of this idea. At the very least, it's a good way to break yourself from the common nervous habit of constantly making tiny adjustments to the volume control, which I have been known to do.

Yes I have thougth of this! I wouldn't go so far as ditching the volume pot totally but It will be clearly marked in dB so I easy can get the same volume agan and again (right now my monitors are connected direct out from a motu 828mkII so I cant'n switch monitors but I've noticed that It's very convienient to adjust the volume when the motu on the display tells you the attenuation in dB).

If you watch carefully on the picture you can se a DIM switch where you actually can do what you suggested. You can step down the level by -18dB or -36dB. These values are chosed in relation to the values on the pot. So if you are at the near bottom end of the scale you just flip to -18dB and you can go back, adjusting the volume (for more accuracy) on the top of the scale again or you could just use it as a dim switch to monitor at whisper level. You can also adjust the volume to monitor on -18dB and the flip the switch to 0dB (that would be fun).

I'll maby consider changing the values on that switch (everything isn't written in stone) so I can have a "cranc it up" setting that is working.

Thanks for the inputs everyone, they are most wellcome!

/Cojo

[Rep]

Originally Posted by Cojo

Thanks!

I am using a series stepped attenuator simular to those on Goldpoint but I have calculated my own resistors so I get the steps that I want.

/Cojo

Nice


Where are you getting the resistors for your stepped attenuator,
DO they have kits with bords and knobs ...ect
... IS it Vishay-Dale / other high end resistors,
where can you buy them from ?

[paully]

Originally Posted by Cojo

... I am using a series stepped attenuator simular to those on Goldpoint but I have calculated my own resistors so I get the steps that I want...

>>>>>>>>>>>>>>>>>
Great way to save about $500 for the same thing (Goldpoint).

Paul

[Rep]

Originally Posted by paully

>>>>>>>>>>>>>>>>>
Great way to save about $500 for the same thing (Goldpoint).

Paul

Really ? Even with all the parts that go into it ... like all the other things Like the housing , knobs, circuit boards, ect... where does one get all the good parts / not radio shack / high-End.
If all that was even worth the time wise,
... but for a custom unit It is worth the pain..

[paully]

Originally Posted by Rep

where does one get all the good parts ...

>>>>>>>>>>>>>>
Pretty much any component supplier like Mouser or Allied. Specify 1% components and check before installing. I'm sure you'd be 'close enough'. I'd also think you could build it for under $100.

Paul

[Cojo]

Originally Posted by Rep

Nice


Where are you getting the resistors for your stepped attenuator,
DO they have kits with bords and knobs ...ect
... IS it Vishay-Dale / other high end resistors,
where can you buy them from ?

Hi!

I'm probably gonna use Firstronics RM0207S. They are similar to the Vishay-Dale CMF60D that Goldpoint use. Vishay-Dale CMF60D follow the military standard RN60D and Firstronics RM0207S RN55C. The difference is RN60D, min 300V and temp coefficient 200-500ppm/degC while RN55C, min 200V and a temp coefficient of 50ppm/degC.

I'm probably buying from elfa.se.

I'm having a hard time locating a store to provide me with a 4 pole 24 pos elma 04 switch. If anyone knows a great store that provides elma switches to be bought in single quantitys please let me know!

/Cojo

[paully]

Try contacting:

http://www.electroswitch.com/

This is what they offer:

http://www.electroswitch.com/electro...ctor_guide.pdf

I'm sure you're aware of this, but Goldpoint sells just the switches as skeletons, or loaded. If that's what you're shooting for, look here:

http://www.goldpt.com/prices.html Choices / price

http://www.goldpt.com/vcb_sa2x.html Picture of the 4-deck switch

Paul

[h2000]

Originally Posted by ulysses

If your monitors are always the same volume, then you will grow accustomed to knowing how loud things should sound in your mix. From there, it proves useful to have a "crank it up" setting so you can (briefly) hear the mix at full volume, as well as a "threshold of hearing" setting where you can hear what the last elements to disappear are.

That's a pretty cool alternative. I have my volume marked at my useful points of reference anyway, so it's true that I don't really use the full range.

Only thing is when I listen to any current CDs on the market, I'll set it to the "threshold of hearing" setting and still be blown out of the room. LOL

[Cojo]

Originally Posted by paully

Try contacting:

http://www.electroswitch.com/

This is what they offer:

http://www.electroswitch.com/electro...ctor_guide.pdf

I'm sure you're aware of this, but Goldpoint sells just the switches as skeletons, or loaded. If that's what you're shooting for, look here:

http://www.goldpt.com/prices.html Choices / price

http://www.goldpt.com/vcb_sa2x.html Picture of the 4-deck switch

Paul

Yes I've seen them. But I think they are so overpriced so it's probalbly my last alternative. Thanks for the electroswitch link although they didn't have exactly was I had in mind.

/Cojo

[Cojo]

Ok, I have done some listening tests according to Ulysses suggestions so if you have it in the middle position it will be possible to use it as a "crank it up" and "bring it down to whispering low" level switch. The values I have found that seems to work have been: 0dB(top pos), -8dB(mid pos) and -24dB(bottom pos). Any suggestions or could these values work?

Thanks for the inputs so far!

/Cojo

[Matt Syson]

Hi
How about using relays and a cheap (er) switch. You could then get into surround monitoring levels too if you wished. A 12 position rotary with some other switch types for the mute, dim and even 'boost' positions should pretty much cover it.
A 24 way rotary is available from Digikey but I haven't investigated them yet.
This is a project I have been meaning to get into but never have the time so I have a 1K dual pot in an aluminium box!
Your box looks great though!
Matt S

[Cojo]

Originally Posted by Matt Syson

Hi
How about using relays and a cheap (er) switch.

I can't say I havn't thought of it! One advantage would be that I can have all the electronics in a 19" rack and a brake out box with the controls. Hmmm...

Originally Posted by Matt Syson

This is a project I have been meaning to get into but never have the time so I have a 1K dual pot in an aluminium box!
Your box looks great though!
Matt S

Maby it's time to start your project! It's never to late.

Thanks for the comments on the design. Keep in mind it's just sketch, the final box would probably have different proportions.

/Cojo

[Matt Syson]

Hi
My initial thoughts are to have a set of constant impedance T pads (probably 600 ohm by convention) of 1,2 4,8 (dB) sequence attenuators. Unbalanced would be 2 pole relays but balanced gets more expensive for 4 pole. The Dim and boost relays would be set to around 14 - 20 dB for dim and ?? for boost.
You could go mad and stick a microcontroller in there to operate things and do 'intelligent' offset (balance) functions or keep it simple.
My first assembly used an A/D convertor and works well enough. I had 0.5 dB as my first switch level change and it sounds a bit manic when sweeping min - max on the pot!
The choices got too much for me so I stopped working on it although the audio board may happen soon, probably eurocard size 2 channels with the relays and relay drivers.
Matt S

[tINY]

A clever fellow would figure out how to use an r-2r ladder instead of T or L pads and save a few bucks.....




-tINY

[Matt Syson]

Hi
An R-2R attenuator would not have constant input and output impedances so would vary depending on the amplifier and source impedances. It would also be switch inefficient as you would need many more steps to get say 1 dB resolution over a 60 - 70 dB range. By all means post how it is done if you can manage it.
Matt S

[ToroRojo]

I hope this isn't an ignorant question, but how would one go about implementing a calibrated monitoring level pot (from a high level standpoint)?

In order to do this, it seems that all incoming feeds would have to have the same level prior to hitting the calibrated pot. It seems an additional trim pot would be needed to adjust the level of the individual inputs to get the correctly calibrated output.

[tINY]

Originally Posted by Matt Syson

Hi
An R-2R attenuator would not have constant input and output impedances so would vary depending on the amplifier and source impedances. It would also be switch inefficient as you would need many more steps to get say 1 dB resolution over a 60 - 70 dB range. By all means post how it is done if you can manage it.
Matt S

Using a 16 rung r2r ladder, 9 output tap positions and 5 ground taps I can get this.

This is assuming that Zout of the source is 0 and Zin of the amp is infinate. Imp scaler is the input impedance of the attenuator and the input impedance of the amp would be in series with 2*R. It might work pretty well if you can find an R2R ladder where R=200-500ohms.....



-tINY

[Matt Syson]

Originally Posted by ToroRojo

I hope this isn't an ignorant question, but how would one go about implementing a calibrated monitoring level pot (from a high level standpoint)?

In order to do this, it seems that all incoming feeds would have to have the same level prior to hitting the calibrated pot. It seems an additional trim pot would be needed to adjust the level of the individual inputs to get the correctly calibrated output.

Hi
The first part of your question is a little ambiguous so I am presuming you mean how do you set a calibrated listening level. You would select a nominal average recording level say 0VU or 12 - 18 dB below digital full scale (depends on material you are working with) and set levels of your 'volume control' on the desk (or controller) to be say 10 - 16 dB less than maximum. Now using a sound level meter adjust your monitoring power amp controls for a suitable listening level.
Most of this is of course subjective although I believe if you are int film work Dolby Labs have specifications which they mix to so that when played back in cinemas which should also have been calibrated the audience hears the soundtrack as it was intended. (too dumn loud in my experience!!).
In reply to the second question, yes all sources should have been 'normalised' such that they all appear at the volume control at the same level when at their 'line up' condition. The source selector would normally have adjustments available to set this up. There are various units out there, Dangerous is one that comes to mind although there are others which have these facilities and more.
CoJo was proposing a relatively simple unit (I believe) which would be perfectly workable and probably as much as most people would require. Unfortunately his picture did not really show what all the switches do but it is a super enclosure.
Am I reading Tiny's graph correctly in that the attenuation is between about 7 dB and 20 dB? If this is so, although impressive by itself does not give much range (13dB as shown) and it is too conditional in requiring a low input drive impedance (not really a problen but may be if driven from a simple switch source selector) but requires an infinite load impedance or calculated using a known load perhaps. When switching to alternate amplifiers for your nearfields then this may well be different.
Matt S

[Cojo]

The inputs on my controller is intended to select between DAW and MIXER and both (in my case) have their own monitor volume so calibrating is no problem otherwise there would deffinatly be good if you could adjust and match incomming levels. The outputs are going to two sets of powred monitors and they have also their own level controls so matching them is no problem either.

Matt, you have triggerd some new ideas regarding the attenuator so now I'm calculating new resistor values like a mad scientist!

/Cojo

[Matt Syson]

Hi Cojo
I think I would be tempted by the constant impedance pads since it makes calculations easier and the results more predictable (the worlds RF engineers can't all be wrong!) They would normally be working the 50 or 75 ohm area. I would set my attenuators based on say 1K or 1K2 to give a gentler load. If you were really bored you could set the actual load in this area but using the computer spreadsheet to find a value which can be achieved by the most 'usual' resistor values, or you can watch paint dry!
Having them actually unbalanced but floating would probably be a reasonable compromise and allow simpler switching.
Can you turn your picture so we can see what all the switches are doing?
Look at some vintage gear diagrams to see how constant impedance pads were done, it's just the multi position switches we can't get now.
I look forward to seeing what you come up with.
Matt S

[Cojo]

Hi, here's a image from the front. As I said the dB values vould probably change (as I'm calculating right now) but the function switches would be the same.

[paully]

One thing struck me about your original photo. Does a loaded 4 x 24 switch actually fit in that slanted box? I'm working on an old Binson unit with a similar 4 deck switch. I know there are different switches available, but the Binson is at least 3" long. Just curious.

Paul

[Cojo]

Originally Posted by paully

One thing struck me about your original photo. Does a loaded 4 x 24 switch actually fit in that slanted box? I'm working on an old Binson unit with a similar 4 deck switch. I know there are different switches available, but the Binson is at least 3" long. Just curious.

Paul

Ha!

You're the first one who noticed!!!

No it doesn't fit in that box. It will be a little higher, the picture was just made for me to get an idea of the look with the wood against the frontplate.

/Cojo

[supaheef]

Well call me a dodgem car, because I like to bump!

How is this thing coming along? Any finished photos or thoughts? I am thinking about building my own passive volume control (but with mono and channel mute switches) when I finally get back to land of Oz (currently I am stuck in Kansas with a tin man, a lion, a little dog...)

Photos and/or words would sate my (and others, I imagine) curiosity...

sh.

[Cojo]

Nice little story!

Thanks for the interest in my monitor controller but I think I'll have to make you disapointed... sorry!

I have had a lot of other (non musical things) to do such as renovating my kitchen that have taken up all my time this spring. I have also purchased a new mixer (actually it's second hand but to me it's new) and I'm going to alter my setup a bit so my need for a monitor controller is not as big any more. But I would still like to make one! Maby later this year when the summer is over and the leafs are falling.

Now I'm going to enjoy a few festivals, drink some beer in the sun and chill!



/Cojo

[supaheef]

Well that sounds fun too! As an aussie I am a big fan of beer, sun and festivals. In that order too...

I don't get back to Oz for another 3 months yet, but who knows, I might be you to the finish! However I am notoriosly slack, especially with a soldering iron.

peace out!

sh.