Microphone configuration and soundstage

[March Audio]

If you read the datasheet of the LT3042 it says the more you run in parallel, the lower the noise is. Also helps to distribute dissipated heat. I suppose you also benefit even if the other regulators aren't of the same quality. I was always told that the best regulator should be the one closest to whatever is using the power. And it should be located very close. Within 1 cm if possible, and use high quality bypass caps to reduce noise/increase PSSR. This was likely why the noise increased. The noise was picked up in the long distance between the supply and the ADC chip/analog stage opamp. So I suppose in order to get the very best out of it, you would have to swap the regulators out on the TI board with the LT3042's. But they don't come in the same package. Not sure if there's an adapter or not available.

Yes, agree with all of that, but I'm already achieving the adc spec, what gains could be made, if any, are very small.

 

[March Audio]

Getting back to the basic soundstage question. Three experts have written much on the subject.

Siegfried Linkwitz
http://www.linkwitzlab.com/Recording/AS_creation.htm

David Griesinger, both papers and videos about sound reinforment in halls.
http://www.davidgriesinger.com/

Floyd Toole in his book "Sound Reproduction".

Thanks for the links. Yes, got Floyd's book. Well worth a read.

 

[gearfreq]

Soundstage has been mentioned in another thread, I thought I would bring the discussion here as the useful information is being lost with unfortunate troll noise.

Soundstage is mostly an artificial construct made up from decisions and techniques used by the recording engineer. I would welcome comment from any studio professionals or experienced individuals out there on this. Even when the techniques are boiled down to their simplest levels, stereo pair mics, their positioning can have a clear effect on the perceived soundstage.

Just for fun I am going to record a speech "walkaround" in a few different environments with different mic configurations so people can hear the differences.

Set up is as follows:-

Rode NT5 cardioid matched pair -
http://www.rode.com/microphones/nt5
http://www.soundonsound.com/sos/aug02/articles/rodent4nt5.asp

Seventh Circle Audio T15 Mic pre-amps - https://seventhcircleaudio.com/products/8

Texas Instruments PCM4222EVM ADC - http://www.ti.com/lit/ug/sbau124/sbau124.pdf

Adobe Audition recording at 24 bit 96kHz

The ADC/mic amp is not exactly pretty, it more evolved with a lot of left over bits from the parts bin rather than being designed, however technically it performs very well.

View attachment 833

Wiki on sound localisation - https://en.wikipedia.org/wiki/Sound_localization

There are lots of resources on the net regarding stereo mic positioning and techniques, I randomly picked this one to give an idea of the possibilities.

http://ehomerecordingstudio.com/stereo-microphone-techniques/

Mic configurations are as follows
http://cdn1.rode.com/sb20_quickstart.pdf

1. Stereo spaced pair - Probably should be omnis for this, but I dont have them to hand.
View attachment 837

2. X-Y
View attachment 838

3. ORTF
View attachment 836

The recordings were made in my theatre / listening room which is well damped with an RT60 of around 0.25 in the midrange. All 3 recordings follow the same procedure, speech from 8 points around the room and a 1-24 count walking in a circle around the mics. This is followed by an extract from a track by Bill Morrissey. I will try and get time to record in a different room (far less absorption) and outside in the garden to see if these spaces affect the perceived soundstage.

I have a definite favourite configuration which I think most represents the spatial sound I hear. It will be interesting to see if others agree.

here are the recordings - dont laugh at my accent, I cant help being born and bred in the UK West Country!

http://gofile.me/2vnEF/sSiF1iTeL

Hello! I know its been over 6 years since this post but I was very curious to your ADC/Pre amp build. I have had a TI 4222 ADC sitting around for years I wanted to build a DIY all in one stereo 500 pre/ADC unit just like yours. I was wondering how it has been holding all these years. I only got as far as building psu's for them. I would love to know more about that build. Cheers!