In-ear finalizer/mastering device: anybody interested???

[Rogy]

The schematics and some curvers for the Constant Amplitude Phase Shift EQ are now available on my site.

Go to http://users.pandora.be/Rogy/IEMFinalizer/CAPS%20EQ/
and choose one of the five bands' folders.

Next thing to do is sim the Width control circuit and make a choice on the multiband comp topology.

For the comp probably a VCA will be the best gain reduction element choice.

I'll have a look at That Corp's design notes; I have some 2181's laying around that might be just suitable for the job...


Greetz,


Rogy

 

[Rogy]

And a block schematic has been added.

http://users.pandora.be/Rogy/IEMFinalizer/Block%20schematic.pdf


All comments are welcome!


Rogy

 

[StephenGiles]

Great stuff Rogy.
Stephen

 

[Samuel Groner]

Thanks for your sims, Rogy!

A block schemo for my suggested auto release sidechain:

[removed]

Samuel

 

[StephenGiles]

Samuel - so you are suggesting something like this - from the What Compressor?:

Stephen

 

[Samuel Groner]

Samuel - so you are suggesting something like this - from the What Compressor?

It goes in this direction, but it is a bit less simple. At least you need a RMS-converter. Did you check my earlier post in this thread about it?

Samuel

 

[StephenGiles]

Samuel - I was called away so I cut short my post! Yes of course one needs the RMS detector, something like a 2252 or SSM 2120 would do the trick. As to the bit of circuitry I posted, I quote from the "What Compressor " blurb:

The first envelope generator is the peak detector consisting of active
rectifier U3B, R10, R13 and C1. The second is the simple passive
averaging circuit containing R14 and C2. Active rectifiers U4A and
U4B select the highest voltage from either envelope generator at any
given moment.

I think Drawmer use a slightly different approach, and Aphex use all sorts of circuit wizardry which you can see here:
http://www.aphex.com/2020mkIII_downloads.htm
....bugger, I'm needed again!
Stephen

 

[Samuel Groner]

...

 

[Rogy]

Hi again,


I uploaded a complete schematic for the CAPS EQ; the three parametric bands and the hi/low shelvings are all on the same schematics page. Potmeters are clearly indicated (these will one day be replaced by rotaries; anyone who can provide me with a conversion graph showing linear potentiometer turn vs log and reverse log potentiometer value change?).

CAPS EQ schematic :

http://users.pandora.be/Rogy/IEMFinalizer/CAPS%20EQ/CAPS%20EQ%20Schematic.pdf

I also did an attempt to convert Samuel's suggested Width control into a full schematic. Please check this; there will be errors!

How do I test the function of this circuit with a spice simulator? What test signals to apply and what output to expect?

Width control schematic :

http://users.pandora.be/Rogy/IEMFinalizer/Width%20control/Width%20schematic%20V3.pdf


Greetz and enjoy!

Rogy

 

[Samuel Groner]

I also did an attempt to convert Samuel's suggested Width control into a full schematic. Please check this; there will be errors!

The makeup-gainstages should have a gain of +3 dB and not +15.5 dB. Otherwise it is correct, I think.

To avoid another active stage, the highpass-filter could be implemented with a switchable cap @ the output of U508 (after the feedback, of course).

How do I test the function of this circuit with a spice simulator? What test signals to apply and what output to expect?

As a first try, apply a 10 kHz sin to one input and 50 Hz to the other. Lowering the width should mix the signals while expanding will result in a simple (positive) amplitude change.

The filter should bring some 50 Hz to the opposite channel.

Samuel

 

[Rogy]

Hi Samuel,


I knew something had to be wrong; it was too long a day yesterday!

I adapted the gain of the summing amps and added the cap for the HPF.

HPF extremes are 20Hz and 300Hz for the moment; I thought I read somewhere that there isn't much of a stereo perception below 300Hz; is this correct?

New Width schematic :

http://users.pandora.be/Rogy/IEMFinalizer/Width%20control/Width%20schematic%20V3.pdf

I will try and sim this later today.

Thx for the time!

Rogy

 

[Kev]

I can't help but think this is drifting from the original premis and porpose of the project.

Stereo spread and HPF's and stereo perception below 300Hz ??? by who's standard and on what program material.

I agree that in Headphones left right very low matterial might be waisted but that is not to say that perception is low. Content in the low on POP music may be mostly centred so the need for spread at low frequencies might not be required.

Does or should this effect your design ??? ... if this is to later feed a mastering toy then I think you need to stay well separated in left/right.

does any of this make sense.

As far as IEM goes ... what is your original problem you are trying to solve ?

Why not get your hands on a Finalizer or DB-Max from TC and try it on some real IE program sources and see if it is what you want.
Second thought ...
A simple PA active xover and get three RNC's in super nice mode and see what happens. Mix the returns back through a small mixer and just try it all out first.

I still can't work out if you are chasing gain riding (AGC) or peak limiting.

The danger with the heavy multiband peak limiting is that you will be able to raise the rms levels in the EARS to very high levels without clipping and so the talent may be at risk.

You need to monitor this with the same set-up as the talent so you can look after them.

Think about how CD levels have got higher and higher BUT 0dbFS hasn't changed.

:green:
I just bought Green Day's new CD ... As loud as every. :shock:

 

[Samuel Groner]

I adapted the gain of the summing amps and added the cap for the HPF.

HPF extremes are 20Hz and 300Hz for the moment; I thought I read somewhere that there isn't much of a stereo perception below 300Hz; is this correct?

The cap should be placed one net earlier so that it affects both left and right channel. 300 Hz is OK for the highest frq. Of course, for the final design you want more choices and an off-position.

I think the gain of the summing amps is still to high (9 dB); the source imp is 5k (two 10k parallel) and not 10k. Or am I wrong?

if this is to later feed a mastering toy then I think you need to stay well separated in left/right.

Dou you know that almost no LP in the past century has been cut without an elliptic EQ? Of course, every mastering job needs something different, that's why we have bypass switches.

I still can't work out if you are chasing gain riding (AGC) or peak limiting.

I cannot either, but it does not matter. A "good" (in the sense of "flexible") compressor can do both.

Samuel

 

[Kev]

I haven't mastered for LP for such a long time.
The mastering jobs I have done have been very diverse and mostly for a Digital format , Optical CD style, Hard-drive and Tape based stuff. Stereo and multi channel.

I think even the latest Green Day CD may have a track that has the whole drum kit in the left chanel.

Having a single side chain is one thing but I think I'll try to keep the x-talk in my stuff as separated as practical.


I think that most of my comprerssors are too slow to be used as true limiters. Oh well I guess I'll have to settle for my bad, inflexible comps a little while longer.

:shock:
I'll shut up now

 

[Rogy]

[quote author="Kev"]
As far as IEM goes ... what is your original problem you are trying to solve ?
[/quote]

Hi Kev, IEM problem I'm trying to solve is the fact that nowadays there are very good 2-way in-ears (molds) and very good mixing desks and all outboard we need, with one exception: The wireless transmitter/receiver system transporting the mixer's output signal to the talent's in-ears. None of the systems available today is capable of handling a dynamic range of more than 60dB during transmission. Solution: Squash the signal in the transmitter (2:1 to 5:1!!!ratio; this is not a joke...) and try to expand it with the same ratio in the receiver. This way the transmitted dynamic range is artificially increased to, say, 120 dB. Now this companding is carried out by one chip in the transmitter and one chip in the receiver. Most of the time the compander has fixed threshold and ratio. Now what I hear in the receiver has little to do with what was coming out of the desk when it comes to dynamics. If the program material is pretty dynamic with some rhytmic low end in it, what i hear is just pumping and I don't like it.

So I'd rather limit the dynamic range before i send the mix to the transmitter, using a good 3-band comp with dual release per band, so the dynamic range is less but the compression is almost inaudible rather than having the "full" dynamic range which has artificially been companded by a bad cheap dynamics processor.

 

[Rogy]

[quote author="Kev"]
You need to monitor this with the same set-up as the talent so you can look after them.
[/quote]

We are ALWAYS listening to the same mix as the artist, with the same in-ear molds and thru the same type of transmitter/receiver connected to the Solo out of the console. If only one person is carrying wireless in-ears we even listen to a receiver set to the same frequency as the artist's one, so any interference heard by the artist is also heard by us.

When mixing iem's, you have to continuously check all mixes. A sudden 3 dB increase in level of one channel is a problem that should be immediately compensated for because it is perceived as being "a lot louder". This is not the case when mixing on a PA or on floor monitors. In-ear mixes have to be the most accurate mixes possible because the drivers of the in ear molds are about 1 mm away from the cochlea, which converts sounds (mechanical vibrations) into electrical signals. I don't want to blow anyone's ears and most artists listen at an SPL of about 95-100dBA (bloody loud).

 

[Rogy]

Now back to the electronics.

I finally succeeded in simulating the Width control circuit.

http://users.pandora.be/Rogy/IEMFinalizer/Width%20control/Width%20schematic%20V3.pdf

The gain of the summing amps is changed to +3dB (A=Rt/Rin, with Rin being 10K//10K = 5K)
So +3dB = 1.41x.
Rt = R502 = Rin x A.
R502 = 1.41 x 5K = 7.06K Correct?

The HPF Cap has been moved. It is bypassed in the above schema.

In this place, the plots can be found:

http://users.pandora.be/Rogy/IEMFinalizer/Width%20control/

I made plots with the Trim at 0dB and at + and -10dB.

One thing that should be noted is that for every dB of trim applied, the output voltage will raise by 1dB. So when the trim is at 0dB, input and output signals are equal in level.
At + or -10dB trim (extreme narrow or wide) the output signals are 10dB (3.15x) louder than the input signals.

This is a problem that we should try to solve; there should be made an interaction between the Trim circuit and the gain of the input buffers (to preserve headroom). Ideas on how to implement this? I think it can be done by replacing the input buffers by the same circuits as the Trim (U503-U508) but with opposite gain and control the gain of the four Trims by one four-gang rotary switch.

Anyway i'm glad we got this far; thanks again Samuel for the explanation of the width topology.


Concerning the multiband comp, I had a look at the What comp and I like some of the ideas used in there.
The What comp is similar in design as the JBL Urei 7110, one of my favourite 1U-comps. However the 7110 uses a VCA and the What an opto/LDR.

The schematic of the JBL/Urei can be found here (on last page of PDF)

http://users.pandora.be/Rogy/IEMFinalizer/Multiband%20comp/JBL-7110%20manual.pdf (3.2MB!)

Maybe we could adapt some of the 7110 circuitry and use that for the multiband?

Gotta go work now (mix in-ears...)


Bye


Rogy

 

[StephenGiles]

Is the 7110 an acceptable compressor? I have SSM2014 and (I believe) it's drop in successor - SSM2018 in my samples box.
Stephen

 

[Rogy]

Hi Stephen,

I like it a lot because of it's peak/average knob; it can really handle all styles of music, it can be driven hard and fast or soft and slow. To my opinion it's one of these compressors that you can hardly ever get to "sound bad".

Its main quality is that it can be used to apply quite some gain reduction without being audible (no pumping and breathing).

However I never did an A/B bypass test with all controls flat to see how much colouration is added by the VCA, without applying gain reduction, so I cannot comment on that.


I certainly like it a lot better than the focusrite compounders. But these have 2 channels of comp in 1U, and the 7110 only one.

Greetz,


Rogy

 

[Samuel Groner]

Sorry, Kev, if you felt kicked off - it was not my intention to do so! Of course you are right that most analog comps do not well as a peak limiter, and a mutliband will do worse. That's why I suggested a limiter after the comp and it was my fault when I did not make clear that I was thinking about this combo in my last post.

One thing that should be noted is that for every dB of trim applied, the output voltage will raise by 1dB. So when the trim is at 0dB, input and output signals are equal in level.
At + or -10dB trim (extreme narrow or wide) the output signals are 10dB (3.15x) louder than the input signals.

I'm not sure (I almost wrote shure :grin: ) whether the level change will be a problem; if you lower the width, the stereo-portion of the signal will have lower and the mono-part higher amplitude. Depending on the original signal, this will result either in a higher or lower overall output level. The test signals I suggested do not simulate this well. Can you try pink (or white) noise?

Replacing the input buffer is a good idea, but I would throw in a dedicated rotary switch.

Lowering the width should mix the signals while expanding will result in a simple (positive) amplitude change.

The second one is BS, sorry about that. The sims Rogy did are correct, my prediction was not.

Samuel