distortion analyzer recomendations?

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#141
I noticed that the sample rate and bandwidth of the TiePie is better than the PicoScope at 12 bits.

PicoScope 72db, 20 MS/sec
TiePie 80db, 50 MS/sec

If there was only a product that split the diffrence between Audio Precision ATS-1 or 2 and these lower cost products.

A good used ATS is tough to come by and still big $$$.

-David
 
#142
EUVL said:
Jan,

I have a TiePie HS3 and never regreted spending the money.

For one it is hard to get any scope with better than 10 bit resolution. With the HS3, you get 12 bit at least, 16 bit if you restrict freq. Yes you can argue how many of the last bits are noise. Still. The bit I like most is the built-in functions generator. Just makes life a lot easier.

The only thing against is that you need to boot your computer every time when you connect the HS-3 to it. Otherwise the TiePie software won't link to the scope.

I am sure you can get better funcgens and scopes stand alone, but not at that price combined. And it is a cute little thing.

🙂


Patrick
Click to expand...


One reason I'm still hesitating is the limited info on the AWG. For one application I need a signal consisting of a 20-100Hz sine wave, with narrow (50uS) alternating polarity pulses with a prf of say 500-2000Hz superimposed on the sine. I asked TiePie for info but got a non-committal answer. Have you ever tried something like that? Can you make a file with the waveform you want and read that into the AWG?

Jan Didden
 
#143
> Have you ever tried something like that? Can you make a file with the waveform you want and read that into the AWG?

Have not, because what I need is already available, including sweeping through frequencies. But apparently you CAN generate a waveform and read that into the AWG. But 50us pulse might be tricky.....

There must be forums at Benelux for TiePie where you can post the question ??


Cheers,
Patrick


PS
If I remember correctly, at the time I bought TiePie, Picoscope was more expensive....
 
#145
Hi maxpou,
i would like to know if HP331A is a good distortion analyzer for tested my working bench?
Click to expand...
Yes.
The 333A or 334A would be much better (easier to use) as they have auto nulling.

Read my earlier comments on these. I have a 339A and a 334A. I am keeping the 334A because of it's very high frequency response. The 333A and 334A are almost the same instrument. The 333A does not read AM modulated RF waves (big deal!).

-Chris
 
#148
Hi maxpou,
I've seen them go for higher, but I have also seen the 333A/334A go for less money.

One thing to consider is that these all seem to have problems and a seized frequency dial is one of them. It's easy top break the nylon coupler in there.

I do have one of these that I could sell you after I fix it up and make sure it's running to spec. I don't know how much. Depends on how much work I have to put into it. The other thing I could suggest would be to wait until you see a better deal. I found a 333A on Ebay that SY was able to grab for $80 USD. The unit was closer to him. Beware the customs and UPS fees. They can easily run way up there. UPS normally charges $30 ~ $40 to clear parcels. I got a lot of $40 charges, so that the clearing and shipping have been about 1/2 the budget I had for test gear. A sobering thought.

If you can wait for an auto nulling model it would be easier for you to use. Not that the manual ones are difficult. I can usually get a deeper null on manual.

-Chris
 
#150
Armint said:
Hi there,

I am also looking for a distortion analyzer and i came upon this diy thd analyzer: http://www.tech-diy.com/thd_analyzers.htm
Has anyone here actually built it? It's certainly not an easy project, and the rotary switches will be very difficult to obtain. It looks worthwhile though...
Click to expand...

The oscillator uses the state variable layout so is very similar to that used by Bruce Hofer in the Tektronix SG-505 -- you can probably get the distortion down to 0.0003%
 
#152
Cordell oscillator

jackinnj said:


The oscillator uses the state variable layout so is very similar to that used by Bruce Hofer in the Tektronix SG-505 -- you can probably get the distortion down to 0.0003%
Click to expand...


I built several of the Cordell oscillators back in the 80's and have found them to have excellent performance.

Recently, I decided to see if a few simple updates would have much of an effect. Nothing very fancy, just new op amps and better bypassing, along with a supposedly more linear control element.

A plot of the results is below.

Also shows what you can do with a decent sound card and a software analyzer.

Keith
 

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#154
Pan said:
PS3224 is a 12bit unit with the possibility to use oversampling for increased resolution on static signals (or so they say)....Seems like 80dB range to me and I have not changed any files in the software in order to maximise oversampling. Possibly the unit is set for maximum dynamic range, don't know.
Click to expand...

To use resolution enhancement on the PS3224, you need to update the software to Picoscope 6. It's described here.
 
#155
Re: Cordell oscillator

Armint said:
Hi there,

I am also looking for a distortion analyzer and i came upon this diy thd analyzer: http://www.tech-diy.com/thd_analyzers.htm
Has anyone here actually built it? It's certainly not an easy project, and the rotary switches will be very difficult to obtain. It looks worthwhile though...
Click to expand...

Looks very nice i'm reading the paper right now, soldering iron on ! Maybe a redesign of the pcb's with fancy soic's or somthing like that.


kcollins said:


I built several of the Cordell oscillators back in the 80's and have found them to have excellent performance.

Recently, I decided to see if a few simple updates would have much of an effect. Nothing very fancy, just new op amps and better bypassing, along with a supposedly more linear control element.

A plot of the results is below.

Also shows what you can do with a decent sound card and a software analyzer.

Keith
Click to expand...

Which components did you change precise ? only the 5534 by opa627 ? or more ?
 
#156
Re: Re: Cordell oscillator

Jaac said:


Which components did you change precise ? only the 5534 by opa627 ? or more ?
Click to expand...

Hi jaac,

All eight of the op amps were replaced by the OPA627, including the LM318 in the DC control loop. The OPA627 was chosen simply because it was the only modern op amp I had on hand in sufficient quantity.

I also tried the AD797 in the oscillator and output amplifier sections, but it was not stable. The AD797 would probably be an excellent choice if the circuit could be stabilized, but my investigations were only a quick check to see if simple component substitutions would make an improvement, rather than an attempt to re-engineer the design.

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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#158
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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