Topic: Battery/PiP powered jfet buffer for TSB-120a --> Korg MR-1

[Roger Gustavsson]

The TSB-120 with a 4.7k resistor would lower the output level to about 1.6mV/94dB. Will the noisefloor drop by 10dB as well, to -122dBV? That will call for an external low noise mic preamp for recording low level events.

Roger

[Church-Audio]

The TSB-120 with a 4.7k resistor would lower the output level to about 1.6mV/94dB. Will the noisefloor drop by 10dB as well, to -122dBV? That will call for an external low noise mic preamp for recording low level events.

Roger

The total output of the capsule drops so yes noise floor would go down relative to the drop in output. You always need a good quality low noise preamp when your dealing with low acoustic levels   

[jobseek2001]

Chris, there's a discussion of some sorts going on at micbuilders about the 8% distortion figure and whether a 4K7 would do any good.
Care to explain here or there?

[Church-Audio]

Chris, there's a discussion of some sorts going on at micbuilders about the 8% distortion figure and whether a 4K7 would do any good.
Care to explain here or there?

Yeah its simple... I measure my distortion with a FFT analyser and a super low distortion sound source directly coupled to the capsule then I take my 4.7 k resistor and the distortion goes from 8% to 0.5% in an instant. Its very simple not much to tell my methods are correct in my measurements. This works not only with my capsules but with some other capsules as well. I have measured my source with a DPA 4006 measurement mic that has extremely low distortion my sound source at 114 db at 1k is less then 0.004%.

I know my distortion measurements are based on the mic capsule / acoustic properties and not just on purely fet distortion like other tests are. That is why some mics that have problems with the acoustic properties of the capsule and not electrical properties do not benefit from this mod.
This mod absolutely works no question about it.

Chris Church

[ricardo]

I measure my distortion with a FFT analyser and a super low distortion sound source directly coupled to the capsule ...

Is this a B&K 4231 Calibrator?

[Church-Audio]

I measure my distortion with a FFT analyser and a super low distortion sound source directly coupled to the capsule ...

Is this a B&K 4231 Calibrator?

bv

I dont want to give away all my little secrets.... The name and make of the device shall remain my little secret but its not a regular calibrator if that is what your asking. 

[ricardo]

Chris, I'm puzzled by the 10dB drop in sensitivity when you replace the internal 2k2 with 4k7.

Did you measure this on your "FFT analyser and a super low distortion sound source directly coupled to the capsule .. " setup?

[illconditioned]

I measure my distortion with a FFT analyser and a super low distortion sound source directly coupled to the capsule ...

Is this a B&K 4231 Calibrator?

bv

I dont want to give away all my little secrets.... The name and make of the device shall remain my little secret but its not a regular calibrator if that is what your asking. 

Just my opinion, but I don't like this secrecy.  I've said this before, and I'll say it again, there is lots of room for both vendors and diy types here.  Hiding this information does no good.  People in the know (competitors) will figure out how to do this anyway.  You (Chris) are offering a great product at a great price.  And you're constantly innovating, with new products that we (think we) need.  That is what sells your product.  IMO this is what puts you above others (like Soundpros, Core sound, and sonicstudios, for example).

  Richard

[ricardo]

There's a basic misunderstanding going on between micbuilders and here . . . they are talking about a common drain configuration, Chris is using common source.

You are right.  I was assuming the TSB120 used as in their literature; common drain / source follower.

GHW, you mention a Church type 2 wire connection.  Is there a link to this?

Chris, if it isn't too secret  , is your recommendation, "replace 2k4 with 4k7", to do with an external load resistor for common source PiP operation?

I was under the impression you were advocating replacing the internal (SMD on tiny PCB behind the capsule) 2k2.

[Church-Audio]

There's a basic misunderstanding going on between micbuilders and here . . . they are talking about a common drain configuration, Chris is using common source.

You are right.  I was assuming the TSB120 used as in their literature; common drain / source follower.

GHW, you mention a Church type 2 wire connection.  Is there a link to this?

Chris, if it isn't too secret  , is your recommendation, "replace 2k4 with 4k7", to do with an external load resistor for common source PiP operation?

I was under the impression you were advocating replacing the internal (SMD on tiny PCB behind the capsule) 2k2.

Ok I will tell you what part of the gear that I use to test the mics is a burr brown 1k oscillator its a chip that is encased in epoxy. It has one of the lowest distortions available for a 1k oscillator and I couple that with a Mylar driver that is mounted in a machined housing. But its not something off the shelf. I use a 4.7k resistor in almost all of my mics and it works provided you have approximately 10k or so load impedance and a 9 volt supply.

Chris

[illconditioned]

There's a basic misunderstanding going on between micbuilders and here . . . they are talking about a common drain configuration, Chris is using common source.

You are right.  I was assuming the TSB120 used as in their literature; common drain / source follower.

GHW, you mention a Church type 2 wire connection.  Is there a link to this?

Chris, if it isn't too secret  , is your recommendation, "replace 2k4 with 4k7", to do with an external load resistor for common source PiP operation?

I was under the impression you were advocating replacing the internal (SMD on tiny PCB behind the capsule) 2k2.

Ok I will tell you what part of the gear that I use to test the mics is a burr brown 1k oscillator its a chip that is encased in epoxy. It has one of the lowest distortions available for a 1k oscillator and I couple that with a Mylar driver that is mounted in a machined housing. But its not something off the shelf. I use a 4.7k resistor in almost all of my mics and it works provided you have approximately 10k or so load impedance and a 9 volt supply.

Chris

Thanks for the information.

I will say that you are probably the only builder to systematically tests their gear.  I have only recently started testing (PC with EMU 1212m soundcard, RMAA program), and it is certainly more tricky than I imagined.

  Richard

[ricardo]

Ok I will tell you what part of the gear that I use to test the mics is a burr brown 1k oscillator its a chip that is encased in epoxy. It has one of the lowest distortions available for a 1k oscillator and I couple that with a Mylar driver that is mounted in a machined housing. But its not something off the shelf. I use a 4.7k resistor in almost all of my mics and it works provided you have approximately 10k or so load impedance and a 9 volt supply.

Thanks for this Chris.  Now everything is clear.

I will say that you are probably the only builder to systematically tests their gear.  I have only recently started testing (PC with EMU 1212m soundcard, RMAA program), and it is certainly more tricky than I imagined.

Richard (and anyone else), do you know of free/inexpensive software/gear to measure acoustic frequency response/impulse response of speakers & mikes?
Electrical stuff is easy with RMAA and other stuff.

The nearest I know of is Professor Angelo Farina's Aurora plugins to Audition.  Not exactly free but the Audition license is the main expense.

I use MARS, a programme by CRC, (Canada) for impulse  responses and my own klunky DOS software for frequency response and signal processing to get a quasi anechoic measurement.

For commercial stuff, I like Clio; especially ClioQC for production testing.  Their inexpensive measurement mikes are one of the few whose calibration I trust.

[Church-Audio]

Ok I will tell you what part of the gear that I use to test the mics is a burr brown 1k oscillator its a chip that is encased in epoxy. It has one of the lowest distortions available for a 1k oscillator and I couple that with a Mylar driver that is mounted in a machined housing. But its not something off the shelf. I use a 4.7k resistor in almost all of my mics and it works provided you have approximately 10k or so load impedance and a 9 volt supply.

Thanks for this Chris.  Now everything is clear.

I will say that you are probably the only builder to systematically tests their gear.  I have only recently started testing (PC with EMU 1212m soundcard, RMAA program), and it is certainly more tricky than I imagined.

Richard (and anyone else), do you know of free/inexpensive software/gear to measure acoustic frequency response/impulse response of speakers & mikes?
Electrical stuff is easy with RMAA and other stuff.

The nearest I know of is Professor Angelo Farina's Aurora plugins to Audition.  Not exactly free but the Audition license is the main expense.

I use MARS, a programme by CRC, (Canada) for impulse  responses and my own klunky DOS software for frequency response and signal processing to get a quasi anechoic measurement.

For commercial stuff, I like Clio; especially ClioQC for production testing.  Their inexpensive measurement mikes are one of the few whose calibration I trust.

The best software out there IMO is winaudiomls I have the lab edition with all the plugins.. but you dont need to get that elaborate. I also use the emu 1212m soundcard as my measurement interface. Here is a link to an ebay auction for the basic version of the software I use. I have over $3000 in software from Winaudiomls and I can honestly say they do update and fix any bugs that I find with in 24 hours.. thats pretty impressive..
check this link from time to time he has deals on ebay for his software. http://www.dr-jordan-design.de/Special_offers.htm

http://www.dr-jordan-design.de/complete.htm

[Roger Gustavsson]

There's a basic misunderstanding going on between micbuilders and here . . . they are talking about a common drain configuration, Chris is using common source.

You are right.  I was assuming the TSB120 used as in their literature; common drain / source follower.

GHW, you mention a Church type 2 wire connection.  Is there a link to this?

Chris, if it isn't too secret  , is your recommendation, "replace 2k4 with 4k7", to do with an external load resistor for common source PiP operation?

I was under the impression you were advocating replacing the internal (SMD on tiny PCB behind the capsule) 2k2.

Is this what we are comparing? Inside the red line is what Church is doing and inside the green the standard schematic. The series capacitor and the 10k resistor represents the input of the preamp.



Roger

[Church-Audio]

There's a basic misunderstanding going on between micbuilders and here . . . they are talking about a common drain configuration, Chris is using common source.

You are right.  I was assuming the TSB120 used as in their literature; common drain / source follower.

GHW, you mention a Church type 2 wire connection.  Is there a link to this?

Chris, if it isn't too secret  , is your recommendation, "replace 2k4 with 4k7", to do with an external load resistor for common source PiP operation?

I was under the impression you were advocating replacing the internal (SMD on tiny PCB behind the capsule) 2k2.

Is this what we are comparing? Inside the red line is what Church is doing and inside the green the standard schematic. The series capacitor and the 10k resistor represents the input of the preamp.



Roger

actually thats not what I am doing.