distortion analyzer recomendations?

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#161
I have a set of the printed circuit boards. I received them on October 23, 1983 from the Circuit Works. I never opened the inner package. I planned to put them in a Heathkit IM-58 Harmonic Distortion Meter case that I had. The vacuum tube IM-58 never could read low distortion but it had a nice meter and all the controls and connections. I never got the needed rotary switches. So when my new job (1883) required driving 105 miles each day the project was left untouched.
 
#162
Re: Re: Re: Cordell oscillator

kcollins said:


As may be seen from the plot below, Mr. Cordell has done a truly remarkable job. While the new bypass caps lower the noise floor a bit, the OPA627 performs only insignificantly better than the 5534 / 318 combination of the original design. Not too bad for a couple of 30 year old op amps!

With effort, I�m sure further improvements could be made, but I think the important point here is, that the Cordell oscillator with or without modifications, is a very high performance device, equal to or better than, most available commercial designs.

And that, in my opinion, is what DIY electronics is all about.

regards,

Keith
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Thats the charm of such a project ! and that's why i whant to build it.

Armint said:
Hi guys, thanks for all the replies. I decided I am going to build the oscillator of the Cordell design first, and if I can get that thing to work properly I will continue with the rest of the analyzer. Or, if I'm fed up with the project by then I will have a good oscillator, and I will buy a second hand distortion analyzer to use it with.
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Nice but have you had a supplier for those roary switches ? and keep us posted.

Kevin Graf said:
I have a set of the printed circuit boards. I received them on October 23, 1983 from the Circuit Works. I never opened the inner package. I planned to put them in a Heathkit IM-58 Harmonic Distortion Meter case that I had. The vacuum tube IM-58 never could read low distortion but it had a nice meter and all the controls and connections. I never got the needed rotary switches. So when my new job (1883) required driving 105 miles each day the project was left untouched.
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Those pcb's are nine months older then i'm !! said that you never had the time to build the analyzer. I'm also guessing how old you are when you started your new job back in 1883 !
 
#163
Kevin Graf said:
I have a set of the printed circuit boards. I received them on October 23, 1983 from the Circuit Works. I never opened the inner package. I planned to put them in a Heathkit IM-58 Harmonic Distortion Meter case that I had. The vacuum tube IM-58 never could read low distortion but it had a nice meter and all the controls and connections. I never got the needed rotary switches. So when my new job (1883) required driving 105 miles each day the project was left untouched.
Click to expand...


I had an unassembled Heathkit graphic analyzer of the same vintage -- sold it unassembled on EBay for about 3X the price it went for originally.

Kevin -- Lakewood is an old stomping ground for me -- from high school days.
 
#164
Nice but have you had a supplier for those roary switches ?
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Well, it seems I am a bit lucky for living near Germany. There is a German company called Monacor, that produces multilevel switches like those, but they go only up to 3 levels. You can see them here.
They look like they can be taken apart easily, and with a bit of effort, I am sure I can assemble them into 9-level switches. I ordered them from Sholtzhauer Elektronik, shipping to the Netherlands cost me 8 euro's, not too bad.
and keep us posted.
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I will!
 
#166
I wonder whether anyone who care to comment on the performance of THD or spectrum analyser freeware based on 24 bit 192kHz sound cards. While an analog THD meter is certainly an interesting project, I could not help thinking the many extra features one gets from digital measurement, especially freq analysis, would put an analog meter to obscurity.


Patrick
 
#167
The digital analysis is great BUT sound cards and digital systems in general are much more dynamically limited than analog systems. the bet approach is the R&S of using an analog front end combined with digital analysis. A passive analog filter after the input conditioning/differential amp greatly extends the measurement capability of the digital system. A soundcard adapter that allows for this would be very attractive. Praxis approaches this concept but its focused on speaker analysis so its not got the distortion floor and noise floor essential for analyzing SOTA devices. I use it all the time but revert to analog instruments for basic analysis of amps, preamps etc.
 
#169
Roar:
perhaps you can give us some idea on how the R&S handles the input signal processing?

It would be interesting to create a USB controlled interface for a soundcard with possibly 4 or 5 fixed frequency filters, autoranging in front of the filters and auto gain adjust after to maximize the digital analysis. The interface is necessary to manage the gains and have meaningful readings. Possibly some source processing to clean up the source signal as well.
 
#171
1audio said:

I need to clear out my store room (museum of analog technology) of things I really don't need or use. Perhaps I should post a list for those close enough to come by to pick the excess up.
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As soon as you post your address I'm gonna send you an HP3770A (Amplitude/Delay Distortion Analyzer) which I tried to fix. Perhaps we could call Yellow Freight or ConWay to make a bulk drop of discarded test equipment projects at your warehouse.
 
#174
I have no interest in getting more old stuff with few exceptions. However for those really interested I may post a list of excess to be booted out of here in the next few weeks.

And here in enlightened Califorina we have periodic electronic recycling, so I can properly dump my mistakes. I must presume that NJ isn't that PC yet?
 
#176
Does AP use a post-filter in the generator section of their analyzers?
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Good question. In the first generation, no. And they have an output transformer and still get very low distortion. They do refer to a passive notch on later units input circuit. I have a Client with a new one. I'll see if he has any info. I do have some on the low pass filter for measuring digital amps.

My CLT-1 has a passive filter on its output to get the -170 dB 3rd Harmonic, probably no other way to do it.

I will open the ShibaSoku and see what they do soon. Its distortion is an order of magnitude below the AP. I have looked for a manual with no success so I guess I'll need to open it.
 
#177
Hello guys,
I currently have my eye on an HP334 distortion analyzer.
However I’ve seen some talk about the HP3581A
wave analyzer. Could I use the 3581A as an alternative
to the 334? The reason I ask is because the 3581s seem
to be going pretty cheap. Almost to the point that it makes
me think that there must be some drawback with it.

Thanks
 
#179
But the dynamic range is only listed at 80 dB. So if you want to see that 100 nV signal the maximum input would be 1V and you can't be sure its not generated internally.
The real limitation is how slow it is to get a THD or a noise number. I think they are fine but not a replacement for an audio analyzer. Hang it on the output of the analyzer.
 
#180
Thanks for the replies,
I’m currently looking to fill in some holes on my test bench.
Right now I don’t have anything to check the actual distortion
figure on an amplifier. I would also be using it in the process of
aligning FM tuners. The 334 I’m looking at is in pristine
shape but the price tag is about $300. I’ve just noticed that the
pricing on the 3581s is pretty attractive (as low as 50 bucks)
and wasn’t sure if it could be used as a substitute. If it cant I’ll
bite the bullet pay the extra and go for the 334.
 
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