Hi guys,
unfortunately the life commitments did not allow me to terminate the analyzer.
Many other things have been done:true RMS digital voltmeter (with AD636), digital frequency meter and potentiometer gang stepper relays.
My heart cries, I can not finish this stupendous project.
Almost all stages are already calibrated and boxed shielded.
(I will send some pictures).
Cordially and Best regards
unfortunately the life commitments did not allow me to terminate the analyzer.
Many other things have been done:true RMS digital voltmeter (with AD636), digital frequency meter and potentiometer gang stepper relays.
My heart cries, I can not finish this stupendous project.
Almost all stages are already calibrated and boxed shielded.
(I will send some pictures).
Cordially and Best regards
This looks like a beautiful piece of work. I hope you will soon get an opportunity to finish it. When you do, let us know and show us more pictures and tell us how it performs!
Cheers,
Bob
WOW, nice work.
I'd say get it working leaving out features that will save you the most time.
Or get the oscillator working first.
Distortion Magnifier
Browsing thru this thread on the Cordell THD analyzer project and the later replies regarding the ups and downs of soundcard /software alternatives to vintage gear like the 339 and 334A for THD measurements I was wondering if anyone (like Bob C in particular..) had any thoughts on the third alternative of using the Cordell distortion magnifier in conjunction with vintage THD gear.
My current gear for THD is a stock HP334 and a Cordell distortion magnifier, as well as an EMU 0404USB and ARTA. Like many, I'm exploring my best option at a reasonable cost to measure THD at lower levels than a 334 or 339 can manage AND at higher frequencies than the SC/ARTA approach allows.
I have not yet investigated myself how far the Distortion Magnifier may expand the range of my 334A as repairing vintage audio gear for customers keeps my bench tied up. Plus I have to sort out the inoperative AutoTune function on my 334A first...
Browsing thru this thread on the Cordell THD analyzer project and the later replies regarding the ups and downs of soundcard /software alternatives to vintage gear like the 339 and 334A for THD measurements I was wondering if anyone (like Bob C in particular..) had any thoughts on the third alternative of using the Cordell distortion magnifier in conjunction with vintage THD gear.
My current gear for THD is a stock HP334 and a Cordell distortion magnifier, as well as an EMU 0404USB and ARTA. Like many, I'm exploring my best option at a reasonable cost to measure THD at lower levels than a 334 or 339 can manage AND at higher frequencies than the SC/ARTA approach allows.
I have not yet investigated myself how far the Distortion Magnifier may expand the range of my 334A as repairing vintage audio gear for customers keeps my bench tied up. Plus I have to sort out the inoperative AutoTune function on my 334A first...
I'm considering exactly this. I have a hp 3562a DSA which has a somewhat limited dynamic range in comparison to some current equipment. To to test low distortion levels I want to use a Distortion Magnifier to do this.
unfortunately the PCB's for the Distortion Magnifier are not available anyplace as far as i know. So if anyone knows a source for them please post. If not I will either do a point to point wired version or get a pcb made up.
Sadly the site shows that they are not responding to customers due to health issues.
Home
also, the page that has the pcb now gives a 404 error
Pilgham Audio - HTTP-statuscode: 404
Home
also, the page that has the pcb now gives a 404 error
Pilgham Audio - HTTP-statuscode: 404
thanks, i sent you a pm.
I am fairly confident it will work considering the description people have given. also i do have the linear audio article.
i've started to lay out a board, but, it is something i have done only a handful of times but always have had good results. with the quick turnaround of some of these pcb houses and the costs, its not impractical these days to do.
The Distortion Magnifier is quite good at increasing the dynamic range of distortion-measuring instruments like traditional THD analyzers, sound-card analyzers and spectrum analyzers. I have used it with my traditional HP3580A distortion analyzer which I still love to this day. DSOs with spectral analysis capability can also benefit from the DM because their dynamic range is often somewhat limited.
Apart from dynamic range, the other big elephant in the room is analyzer frequency range. This is a particular issue would sound card based analyzers. If you want to look at the harmonic spectrum of 20 kHz THD, you will see little or none of the harmonics with a soundcard. Even at 192 kHz sampling, you will only see harmonics up to about 80 kHz.
Cheers,
Bob
I would recommend contacting Jan Didden about availability of DM PCBs or artwork. Jan oversaw all of the implementation of the DM into a buildable PCB.
Cheers,
Bob
Thanks Bob. Just as you said, my EMU 0404 soundcard setup taps out at ~90 kHz with its 192 kHz sampling rate.
I'm hoping when I get the AutoTune on my HP334A back in operation (bad bridge lamp) I will be able to use it with your Distortion Magnifier to push my THD measuing ability at HF down toward 0.0001%.
I'm also hoping the amp replacement board that I designed for my Pioneer SX-750 will need that kind of firepower to measure THD levels
Thanks Bob,
I've dropped him a PM. At the same time i have started laying out a board myself in case i cant get one. I already have the schematic input and doing the layout now.
While i am at it, i am considering adding a limit switch and some diodes to limit the output to protect sound cards and using the unused op amp to drive a log output to a meter to do the null stand alone.
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Depending on budget --- the 339a can be easily improved with a few parts updated. Especially the oscillator opamp. I have modified several 339 and easily get THD below .001%. The problem with the 339 is finding one with the plastic knobs that are not broken.
At the 400-900 dollar level, a ShibaSoku AM70A does well.
Then, if you want to spend a little more (1500 USD), get IM and THD and individual harmonics up to 5th and be able to measure to -140 Get a stock Panasonic VP-7722A.
Other wise sound cards are the best bang for your money. With a good source (Vinic) you can measure to -110 with good accuracy.
There are several other options but all at higher cost.
THx-RNMarsh
At the 400-900 dollar level, a ShibaSoku AM70A does well.
Then, if you want to spend a little more (1500 USD), get IM and THD and individual harmonics up to 5th and be able to measure to -140 Get a stock Panasonic VP-7722A.
Other wise sound cards are the best bang for your money. With a good source (Vinic) you can measure to -110 with good accuracy.
There are several other options but all at higher cost.
THx-RNMarsh
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I think that the QuantAsylum QA401 is much better bang for the money than virtually any sound card - software combination.
Cheers,
Bob
Hi Bob,
I have the QA401 and a solution using Asus Essence STX with an input attenuator.
Now i´ll try the EVGA NU in order to work with 384kHz sampling rates.
I like QA. is very good, but a good software like Virtins, a good audio card and something like the Jan´s audio front end is, IMHO, far better.
Look at this screenshoot the loopback of Asus with LME49990 at the line output.
Actually the problem with this cards is the lack of better QC (in my card, the right channel is 10 times worse in THD than the left channel - .001% versus .0001% - .001% is excellent for audio reproduction, but not so good for audio measurements).
The USB audio devices like MOTU 8A or RME ADI are excellent too, but a bit expensive devices.
Regards,
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Pilgham Audio is still active, they are revamping the website.
Ask Ward directly at wma@pilghamaudio.com .
Jan
Ask Ward directly at wma@pilghamaudio.com .
Jan
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