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John Curl's Blowtorch preamplifier part II
John Curl's Blowtorch preamplifier part II
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Old 31st October 2012, 07:49 PM   #28731
Wavebourn is online now Wavebourn  United States
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John Curl's Blowtorch preamplifier part II
I've scheduled a trip to Scott Wurcer (if you don't mind Scott) as soon as I have some working prototype of an optical microphone array. The capsules (both omni and cardioid) were shipped today, "one pocket of them" (sic!)
I hope the pocket did not have remains of some cashews or other garbage.

Let's measure and tune them in the "Golden Lab"!
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Old 31st October 2012, 07:51 PM   #28732
Kindhornman is offline Kindhornman  United States
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John Curl's Blowtorch preamplifier part II
Dimitri,
I once saw a complete set of 1/4", 1/2" and 3/4" capsules and all the cables and preamp in an original set on Ebay. Should have bought it at the time. Thank you for the offer, that is more than generous. I would feel bad having someone Else's prized possessions. I do have the Earthworks preamplifier and wonder if that would work with the B&K mike?
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Old 31st October 2012, 07:54 PM   #28733
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John Curl's Blowtorch preamplifier part II
Quote:
Originally Posted by scott wurcer View Post
Still a few dB of room for improvment at those numbers, but yes at 1" it works. They still had to work hard to get the frequency response.
I made quite nice sounding thingies from their capsules with flanges around using a single R-C in feedback for EQ. Quite smooth up to 16 KHz.
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Old 31st October 2012, 07:56 PM   #28734
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Probably he means less interference from light dimmers with IGBT than from light dimmers with FETS?
I mean with a electrostatic input cap high impedance when polarized with high DC , witch need FET or tube, VS low impedance when hf polarization with BJT.
What is so funny ?
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Old 31st October 2012, 08:05 PM   #28735
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Originally Posted by Esperado View Post
I mean with a electrostatic input cap high impedance when polarized with high DC , witch need FET or tube, VS low impedance when hf polarization with BJT.
What is so funny ?
You said "best IGBTs have a lower noise factor than FETs." Insulated gate bipolar transistors versus JFETs? I'm not aware of IGBTs used for much other than high power switching and amplification.
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Old 31st October 2012, 08:09 PM   #28736
scott wurcer is offline scott wurcer  United States
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John Curl's Blowtorch preamplifier part II
Quote:
Originally Posted by Wavebourn View Post
I've scheduled a trip to Scott Wurcer (if you don't mind Scott) as soon as I have some working prototype of an optical microphone array. The capsules (both omni and cardioid) were shipped today, "one pocket of them" (sic!)
I hope the pocket did not have remains of some cashews or other garbage.

Let's measure and tune them in the "Golden Lab"!
If it's optical we are interested, seriously. If you are interested we better take it to PM.
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Old 31st October 2012, 08:09 PM   #28737
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John Curl's Blowtorch preamplifier part II
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What is so funny ?
Brad explained. Please forgive our ignorance. I myself once was impressed when tried medium power Soviet KT626 transistors for low noise inputs in mic preamps, may be your finding is something similar, but we are unaware of it.
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Old 31st October 2012, 08:11 PM   #28738
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John Curl's Blowtorch preamplifier part II
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Originally Posted by scott wurcer View Post
If it's optical we are interested, seriously. If you are interested we better take it to PM.
Yes, I am.

We both have e-mail, sure.
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Old 31st October 2012, 08:18 PM   #28739
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Originally Posted by bcarso View Post
You said "best IGBTs have a lower noise factor than FETs." Insulated gate bipolar transistors versus JFETs? I'm not aware of IGBTs used for much other than high power switching and amplification.
Sorry, i wrote IGBT instead of BJT, as i said, i'm not friend with acronyms. It was just a typo.
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Old 31st October 2012, 08:19 PM   #28740
scott wurcer is offline scott wurcer  United States
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John Curl's Blowtorch preamplifier part II
I have seen a copy of Ron's paper. It makes sense now, a nice academic overview of everything that's been done. Tables of results make sense op-amps with <1.5 V/us slewrate are not good for audio. There are several tables of amplifiers that didn't register, I'm happy enough with that . Read the results on Nelson's Zen amps, and then we can talk. Ball's in your court.
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