John Curl's Blowtorch preamplifier part II - Page 3181 - diyAudio
Go Back   Home > Forums > Member Areas > The Lounge

The Lounge A place to talk about almost anything but politics and religion.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 27th December 2012, 02:43 AM   #31801
diyAudio Member
 
scott wurcer's Avatar
 
Join Date: Jan 2004
Location: cambridge ma
Quote:
Originally Posted by john curl View Post
In 1972, I was seeking out 100G resistors. Chickened out using them, settled for 1G and 10G. Still have some.
Well even JFET's start to fail on Ib with 100G resistors and doubling every 8 C, this is just engineering. John time to stop I know this punctures one of your strongly held fantasies, this has been hashed over before lets move back OT. In any case this is such a tiny issue issue considering A weighting and at the low end LP's are so bad how could it matter?
__________________
"The question of who is right and who is wrong has seemed to me always too small to be worth a moment's thought, while the question of what is right and what is wrong has seemed all-important."

Last edited by scott wurcer; 27th December 2012 at 02:49 AM.
  Reply With Quote
Old 27th December 2012, 03:06 AM   #31802
fas42 is online now fas42  Australia
diyAudio Member
 
fas42's Avatar
 
Join Date: Jun 2012
Location: NSW, Australia
Blog Entries: 11
Quote:
Originally Posted by john curl View Post
Fas 42, it doesn't really matter. Start with a measurement mike and compare.
Unfortunately, it does matter. The cop out by many in the electronics crowd, when replay is not up to scratch, is that our glorious circuits are not to blame, it's those terrible microphones and speakers which are the trouble makers, how can you get realistic playback when those fellows are mucking up everyone's chances. Well, I would like to see real figures about good these items are, in real situations, and not on a testbench pedestal ...

Frank
  Reply With Quote
Old 27th December 2012, 03:17 AM   #31803
diyAudio Member
 
Esperado's Avatar
 
Join Date: Jul 2011
Location: France
Quote:
Originally Posted by john curl View Post
Anybody yet figure out WHY B&K used such a low input Z?
To linearize the response curve at low frequency ? Or because the impedance of their cartridges is low enough at 10Hz ?
__________________
Ultimate Protection and more.The Only Source of Knowledge is experience, everything else is just information” ©A. Einstein
  Reply With Quote
Old 27th December 2012, 03:45 AM   #31804
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
Humidity is possible when a measurement mike is used outdoors in the rain. These mikes even had a heater, but moisture contamination was certainly possible. I thought that they were being a bit conservative, but that is exactly what they told me, back almost 40 years ago. In 1974, John Meyer and I went to Copenhagen to B&K and ordered 24 2619 microphone preamps with 1G resistors. They charged us extra, and later, they upgraded all their mikes when they found that it worked pretty well. You can ask John Meyer, himself, if you don't believe me. Go ahead! You know the president of MEYERSOUND.
I upgraded all the GD mikes, myself, in 1973, but it was easier, because they used Nagra instrumentation mike preamps, and they were more accessible to modification.
  Reply With Quote
Old 27th December 2012, 04:33 AM   #31805
diyAudio Member
 
scott wurcer's Avatar
 
Join Date: Jan 2004
Location: cambridge ma
Quote:
Originally Posted by john curl View Post
Humidity is possible when a measurement mike is used outdoors in the rain. These mikes even had a heater, but moisture contamination was certainly possible. I thought that they were being a bit conservative, but that is exactly what they told me, back almost 40 years ago. In 1974, John Meyer and I went to Copenhagen to B&K and ordered 24 2619 microphone preamps with 1G resistors. They charged us extra, and later, they upgraded all their mikes when they found that it worked pretty well. You can ask John Meyer, himself, if you don't believe me. Go ahead! You know the president of MEYERSOUND.
I upgraded all the GD mikes, myself, in 1973, but it was easier, because they used Nagra instrumentation mike preamps, and they were more accessible to modification.
Again B&K Technical Review No. 3 1972 a great survey article on microphone noise. Companies release products and are very resistant to change them, the marketeers were happy at the time, who knows, but the engineers were totally on top of all the issues. John it's pretty clear you have no intention of giving ground to anyone else's opinion or alternate views so these discussions are unfortunately a waste of time.
Attached Images
File Type: jpg bknoise.JPG (38.2 KB, 196 views)
__________________
"The question of who is right and who is wrong has seemed to me always too small to be worth a moment's thought, while the question of what is right and what is wrong has seemed all-important."

Last edited by scott wurcer; 27th December 2012 at 04:36 AM.
  Reply With Quote
Old 27th December 2012, 05:40 AM   #31806
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
Look everyone, I showed today the ORIGINAL schematic for the B&K microphone preamp. It had the equivalent of 100 meg input resistance. The reason given to me by a B&K engineer at my office in San Francisco in 1973, was that they kept the resistor values low because of potential humidity problems. I found that a higher value made it usefully quieter, with 4133 capsules, so I modified all the mikes that we bought for the GD to higher values. However, the B&K preamps were more complex and difficult to modify, so we went to them for the upgrade. This is when they ultimately raised their input Z to 1966 standards as shown by Mead Killion in the AES preprint. I don't claim to have invented the upgrade, Mead did it in 1966, and gave me the idea. However, we HAD to pay extra for the upgrade in 1974. It is of course difficult to tell a real microphone expert how to improve their microphones, but we had to, in order to get it done. Perhaps research did not talk to production. That happens, and it even happened at Ampex when it came to record and reproduce heads. They were WAY behind when I came on the scene, in the audio department. Within 5 years they had used every improvement that I suggested in 1968, in their production machines, but not without a fight. I didn't INVENT 1 or 2 mil lams, I just insisted that they be used. Sometimes you just have to embarrass people in order for them to improve the product.

Last edited by john curl; 27th December 2012 at 05:50 AM.
  Reply With Quote
Old 27th December 2012, 06:33 AM   #31807
PMA is offline PMA  Europe
Design engineer, consultant
diyAudio Member
 
PMA's Avatar
 
Join Date: Apr 2002
Location: Prague
Quote:
Originally Posted by Telstar View Post
Pavel, I haven't read all single posts of this huge thread, but I don't remember YOU sharing any of your designs. Why would expect JC to do it then?


Regards
1) why in THIS thread?

2) I am neither claiming I am the best nor I am saying my designs are the best. If I did, I would have to prove it.
__________________
Pavel Macura
http://web.telecom.cz/macura/audiopage.html
  Reply With Quote
Old 27th December 2012, 09:07 AM   #31808
Telstar is offline Telstar  Italy
diyAudio Member
 
Join Date: Dec 2007
Location: Italy
Quote:
Originally Posted by fas42 View Post
I've done this experiment many times now, it's 100% predictable for me: if I change the sample rate, up or down, it changes the reproduced quality. I use Audacity to do the resampling, which has an algorithm that takes the process seriously: it can take half an hour, easily, for a 4 minute stereo track to be crunched, and then I use Audacity again to compare waveforms -- nothing is added, nothing is lost, no matter how times times you do this; only different if you start with a hi-res file that has genuine, above 20kHz, info. Yes, all hi-res files have ultra sonic content, but normally it's pure rubbish, noise, random meandering meaning nothing ...

Frank
I don't doubt this, but if you compare 2L highres (those taken from dxd master) at various samplerates there should be some difference in the waveforms.

Idk how good is audacity, but i have got some files upsampled with Saracon and it's not the same thing as the original.
Moreover, non- integer upsaming alterates the samples even more.
__________________
"The total harmonic distortion is not a measure of the degree of distastefulness to the listener and it is recommended that its use should be discontinued." D. Masa, 1938
  Reply With Quote
Old 27th December 2012, 09:17 AM   #31809
Telstar is offline Telstar  Italy
diyAudio Member
 
Join Date: Dec 2007
Location: Italy
Quote:
Originally Posted by PMA View Post
1) why in THIS thread?

2) I am neither claiming I am the best nor I am saying my designs are the best. If I did, I would have to prove it.
I didnt mean in this thread, Just anywhere.
If you have shared some innovative circuitry, post where you did.
For instance, where is the schematic of your single polarity differential jfet input stage?

Somebody said "who is without sins, throw the first stone". So, are you?
__________________
"The total harmonic distortion is not a measure of the degree of distastefulness to the listener and it is recommended that its use should be discontinued." D. Masa, 1938
  Reply With Quote
Old 27th December 2012, 12:17 PM   #31810
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
It's OK, PMA doesn't need to share more than he does. People just don't like the very fact that I am well known and often receive awards for 'Best of Year' etc. along with my colleagues. I am often accused of not sharing enough, and sometimes I am accused of sharing too much! '-) In any case, my best and newest stuff I will not post here. Everything I posted recently is 25-40 years old. Its time to let them into the light of day.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



New To Site? Need Help?

All times are GMT. The time now is 01:47 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2