Zero Cool [/i][B] I am reading up on my John Curl History and found an interesting quip about J.C and selecting Fet's from a stereophile article. I am posting this here because WDS asked what we look for when selecting devices and this is a twist i hand't thought of! From Stereophile: [I]Footnote 3: John Curl hand-selects FETs for the SCP-2 with a transistor tester which not only measures noise but classifies that noise according to frequency. Thus he can select both on the basis of low noise and of noise with a particular spectral density.[/I][/B][/QUOTE][QUOTE][i]Originally posted by wds said:
hmmm .......
... a transistor tester which not only measures noise
but classifies that noise according to frequency ...
... noise with a particular spectral density ...
What kind of machine can possible do this ???????
John Curl,
I want to borrow your tester. Just for a while!
No worry, I give it back when I have selected my Perfect JFET transistors.
For my upcoming vendetta challenger phono amplifier( Okay, it will be for MM phono cartriges, only )
Lineup
lineup said:
If you are going to measure noise with different parameters, get yourself a nice Danish Cookie Tin.
An HP3581 "Wave Analyzer" can do this -- it has crystal filters from 3 Hertz to 300 Hertz and is tuneable from around 10 Hz to 50kHz -- these instruments were dirt cheap, but now run anywhere from $50 to $200. It is capable of measuring nano-volts, but you probably would want to put a Discrete Cascode JFET preamp, AD797 or LT1028 in front of it. The 3581 can be run off a NiCad pack for ultralow noise measurements.
You could also use the HP3586 "Selective Level" receiver. These are programmable via the GPIB and offer bandwidth as low as 20Hz. Some of the HP3586 receivers have an ovenized reference.
Quan-Tech Transistor Noise Analyzer ...
Check this link:
http://www.pearl-hifi.com/07_Facility_Tour/Facility_Tour.html
Scroll to the bottom to see the picture - no model number or other data though ...
Check this link:
http://www.pearl-hifi.com/07_Facility_Tour/Facility_Tour.html
Scroll to the bottom to see the picture - no model number or other data though ...
noise spectrum & curve tracer
Well in the intervening years, Pete Millet came up with a sound card interface FFT and true RMS meter DIY project, threaded here http://www.diyaudio.com/forums/tubes-valves/155405-test-measurement-interface-soundcard.html
with writeup here pmillet.com but where is the CT200 or any other PC based tube curve tracer project? Anything else out there?
Thanks!
Well in the intervening years, Pete Millet came up with a sound card interface FFT and true RMS meter DIY project, threaded here http://www.diyaudio.com/forums/tubes-valves/155405-test-measurement-interface-soundcard.html
with writeup here pmillet.com but where is the CT200 or any other PC based tube curve tracer project? Anything else out there?
Thanks!
Tube Curve Tracer
Thanks Patrick, looks like I'm going to have to embark on my own, DIY microprocessor/microcontroller based USB interface to get at some of the most useful and low cost instrumentation interfaces & PC displays. Have ordered a breadboarding kit based on "open-usb-io" which uses the ATMEL ATMEGA32 and has 10 bit ADC among other features. This is not good enough to include decent FFT spectrum analysis along with curve tracing, but is plenty good for a prototype; the package gives access to a host of PC display choices, all open source and available for nadda, and while it doesn't have the ability to handle tube voltages or currents itself, that's just a matter of some additional buffering if one plans on using bench supplies as I do for the HV stuff.
Thanks,
Bob
Thanks Patrick, looks like I'm going to have to embark on my own, DIY microprocessor/microcontroller based USB interface to get at some of the most useful and low cost instrumentation interfaces & PC displays. Have ordered a breadboarding kit based on "open-usb-io" which uses the ATMEL ATMEGA32 and has 10 bit ADC among other features. This is not good enough to include decent FFT spectrum analysis along with curve tracing, but is plenty good for a prototype; the package gives access to a host of PC display choices, all open source and available for nadda, and while it doesn't have the ability to handle tube voltages or currents itself, that's just a matter of some additional buffering if one plans on using bench supplies as I do for the HV stuff.
Thanks,
Bob
CircuitEd update: received this reply to my inquiry as to price and delivery of the CT100:
"Hello,
Thank you for your interest in the CT-100.
Unfortunately, the CT-100 is out of stock and out of production at this time.
Regards,
CircuitED"
However I recently came across a USB-based transistor curve tracer kit, Transistor Curve Tracer - ELEKTOR.com | Electronics: Microcontrollers Embedded Audio Digital Analogue Test Measurement which is a R8C/13 microcontroller setup. Bad news, however, the forum discussion about this unit (I have the article from Feb '09 if anyone wants it) is less than complementary regarding some firmware errors, a schematic error, and the fact that it's setup for only 220v operation (UK outfit).
So the search goes on. I now have the Open-USB-IO board (from AU), and it's very neat for getting into Atmel AVR systems and C++ programming. Some of the other open-source instrumentation software out there might be readily adapted, but that's beyond my reach for the time being. I am chasing another setuup that also has promise, a very low end PC-scope application that with suitable buffering could well get to some tube curve tracing without having to reinvent the whole thing, or use a sound card.
"Hello,
Thank you for your interest in the CT-100.
Unfortunately, the CT-100 is out of stock and out of production at this time.
Regards,
CircuitED"
However I recently came across a USB-based transistor curve tracer kit, Transistor Curve Tracer - ELEKTOR.com | Electronics: Microcontrollers Embedded Audio Digital Analogue Test Measurement which is a R8C/13 microcontroller setup. Bad news, however, the forum discussion about this unit (I have the article from Feb '09 if anyone wants it) is less than complementary regarding some firmware errors, a schematic error, and the fact that it's setup for only 220v operation (UK outfit).
So the search goes on. I now have the Open-USB-IO board (from AU), and it's very neat for getting into Atmel AVR systems and C++ programming. Some of the other open-source instrumentation software out there might be readily adapted, but that's beyond my reach for the time being. I am chasing another setuup that also has promise, a very low end PC-scope application that with suitable buffering could well get to some tube curve tracing without having to reinvent the whole thing, or use a sound card.
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