John Curl's Blowtorch preamplifier part II

[kgrlee]

Originally Posted by Wavebourn

I can borrow some most venerable mikes from Gearslutz forum members, if my own mikes are not the reference for someone.

However, would be great to have access to some acoustic measurement laboratory.

If you have a choice, the closest in 'concept' & function to Optimic2 is an Earthworks QTC30. If you record a wide band source with both simultaneously, eg as the 2 channels on a WAV file, I'll even give you frequency response & noise.

Let me know when you have the mikes and we'll talk about how to do the recording to that standard. What were you planning to record? In what sort of environment?

Can you play a WAV file and record it simultaneously with consistent latency?

[RNMarsh]

Wavebourn ---- I too have measurement mics if you need to try any others. However, I am still in Thailand for a couple more weeks --- decided to buy a new condo in Bangkok today. That will keep me busy for awhile. While over here, I look forward and will continue to check and see your progress on making the opto mics better than ever. Thx-RNM

[Wavebourn]

Thank you Guys, I am still waiting for shipment.

[scott wurcer]

Originally Posted by 1audio

B&K make an RF version of the microphone preamp that could easily have response to DC. Sennheiser has a similar technology.

These put the diaphragm capacitance in a bridge, typical usable capsules do not have DC motion since rear front pressure is equalized. The guage side of a strain guage can be set by a sealed chamber even a vacuum. I was amazed to find the silicon pressure guages responded up to 3500Hz. There is one of these that does 15uV/Pa (pretty small) but it yields well to using an instrumentation amplifier. It did "voice of wife from kitchen" pretty well. I ended up making a very nice piston chamber with it (350Hz), up to 150dB and if you translate the specs to audio .1% THD and .1dB ABSOLUTE response calibration without a transfer standard. I hope to get this into Linear Audio as soon as I get time to sit down with our B&K reference equipment to verify this.

http://www.ge-mcs.com/download/press...s/920_276a.pdf

[scott wurcer]

Originally Posted by Wavebourn

However, would be great to have access to some acoustic measurement laboratory.

I do, the MEMS microphone guys bought a complete gold standard everything lab and then moved it to our site.

[1audio]

Originally Posted by scott wurcer

I do, the MEMS microphone guys bought a complete gold standard everything lab and then moved it to our site.

I'm told that the MEMs mikes are very consistent and accurate across their usable range. Its a virtue of the process. Is there a chance that we may be able to get a class 1 transducer for $1.00 instead of $500?

[scott wurcer]

Originally Posted by kgrlee

I've read the Optimic bumph and am frankly quite sceptical ... but it might be NIH syndrome on my part as I've never tried one in the flesh

Me too, peeling back the specs they seemed quite mundane. Big issue, the best optical position sensing techniques present an almost insurmountable fringe counting issue unless you restrict motion to < 1 wavelength then the SNR is very bad.

I would try a force balance system using the optical path to 0 the diaphragm position.

[scott wurcer]

Originally Posted by 1audio

I'm told that the MEMs mikes are very consistent and accurate across their usable range. Its a virtue of the process. Is there a chance that we may be able to get a class 1 transducer for $1.00 instead of $500?

Unfortunately size matters . The SNR reaches the physics limit somewhere around 66dB or so. I haven't heard the new "smart" versions but the last gen sounds pretty good, pretty sure you have one in an iPhone or iPad. Can't tell you how much "they" pay, but there is a secret project with one of the very big mic manus. It would be somewhere between those numbers.

[Esperado]

Originally Posted by john curl

Unfortunately, there is too much 'expertise' being thrown around, amounting to little or nothing.

I can't explain why, suddenly, evolution has stopped in the 80s. In everything, arts as well as technology. Cars are the same, they just eat a little less gas, while they were supposed to fly, in years 2000s. TVs just bigger and flat with more definitions and better colors, and the same programs ever and ever...
We are no more able to walk on the moon, while we were supposed to go to Mars for week-end, in 2000.

About music, each year was the birth of a new sound, rock'nroll, electric blues, country music, ouest coast, Tamla Motown,, Hard rock, heavy metal, jazz rock Funk, reggae etc. Then after the disco years, nothing new....

After home computers and Internet, what else ?

In the audio world, what's new after the digital revolution ? Apart class D amp, i see nothing new or exiting. In Paris there where may-be 30 shops where you were able to find electronic spare parts... now, one ?
Near nobody is able to repair any electronic component, we just throw away them to replace with the last model, even if they still wok...

Last week, i asked a young Rap musician, about that and he answered: "What do-you want us to invent, your generation has created everything". It killed me. 'This is my ge...neration, baby".(The who)

I had explained him that it is just a matter of the way to thing; to look at the things upside down.. We tried, at each moment, to find something new, playing tapes backwards, putting mikes out of phase, saturating, under powered amps, putting mikes under the water, inside bathrooms, lifter's cages, vases, even metro tunnels by night (i have done that ;-), building strange boxes to torture the sounds in a new way.

Musicians told us: "Try to find a new sound, this sound too much like...", then suddenly at each session, new musician arrived, all asking "I want me to sound like..." and they played, imitating the grove and technics of some well known musician...

Rock'n roll music has turned in some king of classical music...Rock'n roll is dead in his wax museum.

[Wavebourn]

Originally Posted by scott wurcer

I do, the MEMS microphone guys bought a complete gold standard everything lab and then moved it to our site.

Thank you Scott; I have to plan a trip to your side of the world!