The least different the joining metals are, the better. And, the fewer different metals used., will be better.
THx-RNMarsh
Hi Scott,
I skimmed the link you provided, it was interesting for one claim that I find improbable I'll quote that passage ...
I had met Arthur Salvatore when he lived in Toronto. I don't know where he is now. He's an interesting fellow with viewpoints that are uniquely his own. When I met him, his listening room was surrounded by LPs on three walls (that is a huge amount of lacquer!) with power cords snaking to a small collection of tube amps and preamp topped with a turntable. The two odd speakers in the room topped off this visual treat. I can't remember what equipment was there as I had other things to do. I believe he owned the building where he was living and working and sold equipment by appointment. Reading his advice in the link, I can believe this is the same person. He was friendly and engaging at the time.
-Chris
I skimmed the link you provided, it was interesting for one claim that I find improbable I'll quote that passage ...
You have got to be kidding me! Someone is giving Joe credit for Allen Wright's work!
I had met Arthur Salvatore when he lived in Toronto. I don't know where he is now. He's an interesting fellow with viewpoints that are uniquely his own. When I met him, his listening room was surrounded by LPs on three walls (that is a huge amount of lacquer!) with power cords snaking to a small collection of tube amps and preamp topped with a turntable. The two odd speakers in the room topped off this visual treat. I can't remember what equipment was there as I had other things to do. I believe he owned the building where he was living and working and sold equipment by appointment. Reading his advice in the link, I can believe this is the same person. He was friendly and engaging at the time.
-Chris
A while back i was wondering about the distotion of measurement microphones adequacy for measuring low distortion speakers.
Seems there are quit a few "condenser" type microphones -- electrics et al... that are low enough distortion but only down to 100Hz
The distortion of these microphones rises a LOT below 100hz. An AES paper explains why and how much and what to do about it.
100 Meg Ohm of input Z of older tube mic amps is not sufficient. 3G is minimum for lowst electrical distortions. 20G Ohm is recomended in which case thd will be below .003% THD for 1/2 inch capsule used compared to 10%.
AES JUne 2000. Vol 48 No6 "Condenser microphone electrical distortions"
THx-RNMarsh
Seems there are quit a few "condenser" type microphones -- electrics et al... that are low enough distortion but only down to 100Hz
The distortion of these microphones rises a LOT below 100hz. An AES paper explains why and how much and what to do about it.
100 Meg Ohm of input Z of older tube mic amps is not sufficient. 3G is minimum for lowst electrical distortions. 20G Ohm is recomended in which case thd will be below .003% THD for 1/2 inch capsule used compared to 10%.
AES JUne 2000. Vol 48 No6 "Condenser microphone electrical distortions"
THx-RNMarsh
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Hi Richard,
I wish I had access to those papers.
Those impedance's you're talking about can only be met with Teflon standoffs and dry air dielectric from what I know. Sealed in nitrogen would be my guess as to how to do this. Normal PCB materials are far too leaky, so Teflon or glass substrate?
-Chris
I wish I had access to those papers.
Those impedance's you're talking about can only be met with Teflon standoffs and dry air dielectric from what I know. Sealed in nitrogen would be my guess as to how to do this. Normal PCB materials are far too leaky, so Teflon or glass substrate?
-Chris
Because what the mic measures at a particular place is not what/how you hear the sound at the same place.
Absolutely correct. Just record yourself in a room and hear what you get. Or record your speakers. Ear differs between direct sound, early reflections and late reflections. Microphone has no idea and makes one summarized sound, from which, when replayed, ear is unable to decipher what was a direct sound and what reflections.
Yes, high input Z is paramount for low LF distortion. Basically it's a C-R-highpass with a nonlinear C (plus the much larger DC-blocking cap), therefore the corner frequency of this must be as low as possible. Low distortion is best achieved with lowest excursion of the diaphragm which favors small size capsules (at the cost of noise) which have lower capacitance and therefore need even higher load resistance for a low LF corner. Parallel external capacitance helps to reduce the impedance but introduces its own systematic wideband distortion, so of little help here.
Source : B&K Microphone Handbook Volume 1, https://www.bksv.com/media/doc/be1447.pdf
Construction-wise, bootstrapping and guarding are used in many capsule buffers to get to the required impedance levels. The classic B&K buffer uses the leakage current of two back-to-back bootstrapped JFET diodes for buffer FET biasing, for example. Still there is a only a single digit Gigaohms feed resistor for the polarisation voltage which isn't bootstrapped in the clone B&K buffer amp I own and thus this may dominate distortion. Bootstrapping can be managed on the supply side of the cable, though (haven't tried this yet)
Yes but just in case there is any confusion - the brains does it's analysis based on the interaural time & volume differences (along with spectral correlation) to be able to extract what is direct Vs what is reflected sound. The pressure waves that hit a microphone's diaphragm is exactly the same as the pressure waves that hits one ear's tympanic membrane.
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