Review: Hantek DDS 3X25. Anyone own one?

[saturation]

Looking for anyone who can post their experiences with this very low cost AWG.
Its one of the most hobbyist price friendly devices for an AWG.
However, don't know how its spec sheet comes up in real life.

The only comments at eevblog, if not anywhere on the net I can find are here:

https://www.eevblog.com/forum/index.php?topic=187.msg1826#msg1826

https://www.eevblog.com/forum/index.php?topic=197.msg1892#msg1892

[saturation]

I've located a short 'review' of the device from a Japanese radio restorer.  Anyone interested can take the links and translate them:

http://kasugamusen.com/2009/07/trio9r4j2.html

http://kasugamusen.com/



Certainly being able to restore these old radios successfully using these tools is a review in itself although in text not much is really said.

[EricF]

I researched this just a few weeks ago, and found someone in an online forum looking for the Windows 7 (64?) drivers which were not yet available. I can't seem to get onto the company site/forum the way I was able to before. Anyway, it does look like it could be a good buy if you want to run it on an XP machine, knowing there is a high risk of no software support.

EricF

[saturation]

Thanks, which forum?

The manual says it should run in 7, but I really think the issue is 64 bit, but it could be run in 32 bit emulation mode in 64 bit OS, I should chat with this person and see if it was done.

I researched this just a few weeks ago, and found someone in an online forum looking for the Windows 7 (64?) drivers which were not yet available. I can't seem to get onto the company site/forum the way I was able to before. Anyway, it does look like it could be a good buy if you want to run it on an XP machine, knowing there is a high risk of no software support.

EricF

[EricF]

It probably is a problem with the 64 bit OS. I believe I found it on a hantek.com support site, but recently I have not been able to reach their servers. My best recollection is that the person was having trouble getting it to work on a windows 7 machine and was asking when the newer drivers would be out. The request was made a few weeks before I visited the site, but no one had replied at that time. I am still considering buying one to play with, knowing it may have a limited lifespan. Truth is I don't really need it, it would just be fun to play around with the arbitrary waveforms. I would consider buying one for Dave to review if there was enough support from the EEV blog crowd and he was willing to do it.

EricF

[saturation]

Thanks EricF, will keep a look out.  I've PM'd Veramacor who basically said it works well, but I'd like to know its real frequency response and THD+N limits, and then finally its ergonomics.

Based on the manual, its -40dB at only 40kHz ! I'm not hopeful, it must make a lot of harmonics by not having a really selective output filter, however I can make those as needed to get cleaner output.

[alm]

and then finally its ergonomics.

I assume you mean software (it's just a box with BNC connectors). Can't you try the software without buying the hardware? Most manufacturers make the software available for anyone to download and implement a demonstration mode if no device is detected. Reading the manual may also give you some idea of the UI. I'm not very hopeful, most software from Chinese manufacturers, even more reputable ones like Rigol is a piece of crap in my opinion.

Based on the manual, its -40dB at only 40kHz ! I'm not hopeful, it must make a lot of harmonics by not having a really selective output filter, however I can make those as needed to get cleaner output.

Auch! You might have a hard time determining the fundamental near its max frequency . I wonder if it's the DAC or the output stage. The filter should just filter out the DDS frequency (assuming it uses DDS, which seems likely), which is constant, so it doesn't have to be very selective. For arbitrary waves, you can combine high and low frequency components, so I'm not sure how you're going to filter that (beyond filtering the DDS frequency), you may want some edges to be very fast. A bad output stage can distort anything, not much a filter can do about that.

[Zyvek]

Just noticed this tonight (no affiliation) on clearance for $99USD:

http://www.saelig.com/CL/CL001.htm

Not sure if this means they are discontinuing them...

[saturation]

Ouch!  I wish I had waited for your link, a lowest final price with S&H going via UPS is $111, $30 less than what I just paid just a few days ago.

I wouldn't be surprised if it has ceased production and is discontinued; its been on the market since 12/2008.  But that's not necessarily a bad thing, its an opportunity for those looking to examine or have a need for low fidelity DDS AWG generation.  The 3x25 typically sold for $150-180 delivered, its closest competitor is over $200 with similarly unclear specifications, such as those by Syscomp or Pico.

http://www.saelig.com/AG/AG009.htm

That's the best price I've read on this to date.

Just noticed this tonight (no affiliation) on clearance for $99USD:

http://www.saelig.com/CL/CL001.htm

Not sure if this means they are discontinuing them...

[saturation]

Hi alm,

Yes, jump the gun that's what I meant, since the box has nothing to it.  If I could test the software, I would have, but I wouldn't be surprised, the www.hantek.com.cn site has been down most often for over a week.  Thus all the inquiries here.  I've gone through all I could find, one thing of key value is the Japanese website and Veramacor's statement, of 'working well.'  The Japanese radio restorer used it to generate AM modulated waveforms I'll presume to the limit of the band, 1.0-1.7 MHz, and likely detect the modulated tones. 

As I understand DDS, the final output stage is a reconstruction low filter.  How its made determines what harmonics and distortion will squeeze through.  As for arbitrary waves with different frequency characteristics, I'll have to play each as it occurs, doing what I draw and what I see comparisons .  Right now, my requirement are burst pulse trains that are PWM, with second long intervals between bursts, and modulated FM to test transmissions into the FM radio band.

and then finally its ergonomics.

I assume you mean software(it's just a box with BNC connectors). Can't you try the software without buying the hardware?  Most manufacturers make the software available for anyone to download and implement a demonstration mode if no device is detected. Reading the manual may also give you some idea of the UI. I'm not very hopeful, most software from Chinese manufacturers, even more reputable ones like Rigol is a piece of crap in my opinion.

Based on the manual, its -40dB at only 40kHz ! I'm not hopeful, it must make a lot of harmonics by not having a really selective output filter, however I can make those as needed to get cleaner output.

Auch! You might have a hard time determining the fundamental near its max frequency . I wonder if it's the DAC or the output stage. The filter should just filter out the DDS frequency (assuming it uses DDS, which seems likely), which is constant, so it doesn't have to be very selective. For arbitrary waves, you can combine high and low frequency components, so I'm not sure how you're going to filter that (beyond filtering the DDS frequency), you may want some edges to be very fast. A bad output stage can distort anything, not much a filter can do about that.

[saturation]

Yes, I concur 'close outs' are my favorite deal purchases.  I will review it,hopefully also take time to post photos of it working to its maximum capacity.

I wouldn't be surprised if it has ceased production and is discontinued; its been on the market since 12/2008.  But that's not necessarily a bad thing,

dont worry, the last batch usually is the most stable and cheapest.

Ouch!  I wish I had waited for your link, a lowest final price with S&H going via UPS is $111, $30 less than what I just paid just a few days ago.

dont worry, you can think later on how to gain that $30 back by using the device. possibly more.

[alm]

As I understand DDS, the final output stage is a reconstruction low filter.  How its made determines what harmonics and distortion will squeeze through.  As for arbitrary waves with different frequency characteristics, I'll have to play each as it occurs, doing what I draw and what I see comparisons .

That low-pass filter is for the harmonics from the DAC, which is usually a fixed frequency.

I believe the difference between DDS and 'true' arbitrary waveform generator (as defined by the manufacturers of those) is that a true AWG runs the DAC at a sample rate equal to number of samples * repetition rate. DDS runs the DAC at a fixed frequency, and adjusts the samples to match. It has to interpolate or round the samples if the sample rate doesn't happen to be a multiple of number of samples * repetition rate. The advantage of DDS is that it can easily vary the frequency, for example for sweeping. This makes it also easy to implement a function generator. I'm by no means an expert on DDS or AWG, most of my knowledge comes from reading appnotes and datasheets/manuals. Some links: Tegam AN-401: True Arbitary Waveform Generators Offer More Than Function Generators with Arbitary Capability, Tektronix XYZs of Signal Generators.

Most cheap arbitrary waveform generators seem to use DDS, even though true AWG seems simpler to me. Maybe implementing true AWG is harder than it looks, or it's because they want to bundle a function generator. My guess is that the Hantek unit also uses DDS.

I added two attachments about filters for DDS. The first is from an ELV design for a 30MHz DDS function generator (no arbitrary waveform capability, but DDS is DDS). The DAC is in IC5 (AD9834), the signal is outputted on IOUT (Sig Bit Out is used for high frequency square waves, just ignore that part). ADG736 is just an analog switch. Depending on the type of signal, the Chebyshev filter (knee frequency = 34MHz) is used for sines (up to 30MHz), but bypassed for square waves (rise time is <5nS IIRC). The sample rate is 67.109MHz, well above 34MHz. The filter doesn't change with frequency.

The second is part of the HP 33120A service manual, a function generator/arbitrary waveform generator (DDS, 15MHz, 40MS/s). Depeding on the type of signal, it either uses a very sharp filter (ideal would be a brick wall response slightly above 15MHz) for sines, or a shallow filter for all other types of signals. Both filters have a fixed frequency response.

[DaJones]

I just purchased one of these units, and it looks like I'm going to have to return it.

I get jitter on all waveforms other than sin, above 2mhz.

Here are some shots of the jitter, using the Rigol REF function to make it visible.






The Sync-Out also has a LOT of jitter and most of the time doesn't stay in step with the output signal ( depending on
the frequency ).

I'm hoping this unit is defective, and that a replacement might fix the issue.  But I can't find any reviews anywhere on the net.

Can anyone confirm that these units actually work and have stable signals?

[saturation]

@ alm, thanks a bunch for those links, some reading to do!

@ dajones, ah!  you're the first to post some specifics about its frequency output.  Is this a 100 MHz Rigol?  Using a 10MHz square wave is at the limits of its frequency response, you'd have to set the scope at its best to reduce the effect of the DSO introducing its own jitter, making the measurement less stable.

http://www.edn.com/contents/images/6486046.pdf

Set the Rigol to peak sampling mode and increase the waveform amplitude, at minimum, has it helped?

[DaJones]

I have a modded DS1052E ( 100mhz ).

I see the same terrible jitter on an analog Tek 2235 scope ( 100mhz ).

The jitter starts at around 2mhz and gets worse as the frequency goes up ( it may start sooner than that, but isn't noticeable, proportionally ).

The Sync-Out jitter is really bad. At some frequencies the jitter settles down, at other frequencies there seems to be no timing connection between
the Sync-Out and the output signal.

In fact, if I set the frequency to 2.5mhz, the Sync-Out is kind of stable ( though the output signal is jittery ). But if I step the smallest amount up or down in
frequency ( 2,500,000.001hz ) the Sync-Out signal looses all timing relationship to the output signal ( and is itself still jittery ).

I'm really puzzled by the fact that this product has been out for years now, and it's for sale all over the place, and yet I can't find any reviews or comments on it.

I'm going to have to ask the seller if he sells a lot of these, if he gets a lot of returns, etc.

If someone could confirm that this is a design problem, I wouldn't bother with an exchange and just get a refund.

So... is anyone with one of these units able to confirm a 10mhz stable square wave??

[DaJones]

As a follow-up on the DDS-3x25...

Here is an image of a 10mhz square wave with display persistence turned on. The jitter seems to always be +/- 5.5ns, no matter what the
output frequency is.




And here is a capture of the Sync-Out caught in the act of jittering.

[saturation]

Thanks dajones, I think the jitter issue maybe real, and not a design defect.  I'm due to get my unit in a few days, and I'll confirm whatever you already find.  Jitter is a problem with synchronous signals assuming its not a scope issue, so this is not something you'd apply this device.

On the good side, it seems the rise time on the square wave is good to 10MHz, suggesting it will produce a useful signal higher than 3MHz, but of questionable stability.

Jitter aside, have you tried seeing its maximum frequency response on sine, and square at least, and how 'stable' they are?  What harmonics on FFT are generated by its pure sine wave to its maximum frequency response? How is the output amplitude stability [we know a bit now of the frequency]? 

[Bored@Work]

Kids, mhz means nothing.  mHz would be millihertz (10^-3 Hz). But if you mean megahertz, then write MHz (10⁶ Hz, or 1000000000 times larger than mHz). If that is to inconvenient for you, what about another hobby or profession?

[Time]

Kids, mhz means nothing.  mHz would be millihertz (10^-3 Hz). But if you mean megahertz, then write MHz (10⁶ Hz, or 1000000000 times larger than mHz). If that is to inconvenient for you, what about another hobby or profession?

Even if I have no interest in a thread topic and I see BoredAtWork has posted something on it I open it up anyways.  Just so I can enjoy golden comments like this one.

[DaJones]

Kids, mhz means nothing.  mHz would be millihertz (10-3 Hz). But if you mean megahertz, then write MHz (106 Hz, or 1000000000 times larger than mHz). If that is to inconvenient for you, what about another hobby or profession?

Thanks for the correction, BoredAtWork.

That sounds familiar. I was in High School when the change was made from "cps" to "MHz", and even at that young age I was resistant to change. Maybe the fact that I disliked the change helps explain why I didn't absorb the details.

And strictly in the spirit of sharing ( I don't normally do this ), I thought I would return the favor and point out a common grammatical error in your response.

"If that is to inconvenient..." should be "If that is too inconvenient...".

[saturation]

As always, alm, a nice information packed post.  I'm still digesting all the articles you linked, and it does clear the air between what is a true AWG, which typically do not use the DDS approach, and what has best been called function generators with arbitrary capability, most which use DDS.

However,  the Hantek design is curious.  The 3x25 suggests it uses a variable frequency clock.  Since the output filter is vital to supression of additional frequencies generated with the DAC process, that are tied to the DAC clock frequency, how they manage to suppress it with a fixed frequency filter will be interesting to see.  Without it, I'd expect to see harmonics and images of the clock frequency contaminating the 3x25 output.

It thus, seems like a 'hybrid' providing some of true AWG capacities using a DDS process; but this is all theory, when I get the unit it will become more real!

3x25 Manual Specs:



In the updated DDS 3005 model, it states the DAC clock is a variable clock and the filters are programmable.

As I understand DDS, the final output stage is a reconstruction low filter.  How its made determines what harmonics and distortion will squeeze through.  As for arbitrary waves with different frequency characteristics, I'll have to play each as it occurs, doing what I draw and what I see comparisons .

That low-pass filter is for the harmonics from the DAC, which is usually a fixed frequency.

I believe the difference between DDS and 'true' arbitrary waveform generator (as defined by the manufacturers of those) is that a true AWG runs the DAC at a sample rate equal to number of samples * repetition rate. DDS runs the DAC at a fixed frequency, and adjusts the samples to match. It has to interpolate or round the samples if the sample rate doesn't happen to be a multiple of number of samples * repetition rate. The advantage of DDS is that it can easily vary the frequency, for example for sweeping. This makes it also easy to implement a function generator. I'm by no means an expert on DDS or AWG, most of my knowledge comes from reading appnotes and datasheets/manuals. Some links: Tegam AN-401: True Arbitary Waveform Generators Offer More Than Function Generators with Arbitary Capability, Tektronix XYZs of Signal Generators.

Most cheap arbitrary waveform generators seem to use DDS, even though true AWG seems simpler to me. Maybe implementing true AWG is harder than it looks, or it's because they want to bundle a function generator. My guess is that the Hantek unit also uses DDS.

I added two attachments about filters for DDS. The first is from an ELV design for a 30MHz DDS function generator (no arbitrary waveform capability, but DDS is DDS). The DAC is in IC5 (AD9834), the signal is outputted on IOUT (Sig Bit Out is used for high frequency square waves, just ignore that part). ADG736 is just an analog switch. Depending on the type of signal, the Chebyshev filter (knee frequency = 34MHz) is used for sines (up to 30MHz), but bypassed for square waves (rise time is <5nS IIRC). The sample rate is 67.109MHz, well above 34MHz. The filter doesn't change with frequency.

The second is part of the HP 33120A service manual, a function generator/arbitrary waveform generator (DDS, 15MHz, 40MS/s). Depeding on the type of signal, it either uses a very sharp filter (ideal would be a brick wall response slightly above 15MHz) for sines, or a shallow filter for all other types of signals. Both filters have a fixed frequency response.

[saturation]

I received the unit yesterday and it does the job well, moreso its excellent for its price performance.  Just went through testing it at its extreme settings and it came through very well.  I think its well suited for providing function generator capacity with arbitrary waveform capability at very low cost.

I confirm dajones posts, there is a persistent jitter of 5-8ns most obvious in the square wave output.  I haven't tried mitigating it, or trying a whole suit of tests, and will post a more detailed review later as I find time.

Prelim testing was done with an unmodified Rigol 50 MHz 1052E and its FFT.  The limits below are written because they are  at the 1052E's bandwidth limits.  I did review the outputs at it maximum setting, 75 MHz sine, and 25 MHz square, and the additional instabilities can't be ascertained to be solely from the 3x25.


Pros

Low harmonic distortion stable sine wave in excess of 50 MHz, here's a sample screen shot at 1 MHz
Fast rise time and symmetric square, triangle, and sawtooths mostly clean [ as expected by a Fourier harmonic distribution] >= 5 MHz  
Instantaneous response from selection to output
Bug free software usage and installation; easy to use, manual not necessary, small size, 11 MB
Works in Windows OS: Vista 32, Win7 32, and XP 32 bit
Small hardware footprint, powered by USB, no external power needed
Interface USB and BNC cables included


Cons

Jitter noticeable in all but the sine waves, worst in square waves, but not exceeding 8ns
Self installing driver did not install in Win7; I manually installed it from the CD
Software could have used more ergonomics
No external power adapter included

[EricF]

Thanks for the initial impressions saturation! Looking forward to hearing more.

EricF

[DaJones]

I confirm dajones posts, there is a persistent jitter of 5-8nS most obvious in the square wave output.  I haven't tried mitigating it, or trying a whole suit of tests, and will post a more detailed review later as I find time.

: /

I was HOPING that it was just 'my unit' that was having this problem.

You might want to take a look at the "Sync-Out" problem.

If I set my unit to 2.5MHz, and display the output signal on one trace, and the Sync-Out on another trace ( on the scope ), I see that
they are in step and not much jitter on the sync line. If I bump this up or down in frequency by a small factor ( 2.51MHz or 2.5000000.001 or 2.4999 )
the Sync-Out signal gets so jittery there doesn't seem to be any timing relationship between the two signals at all.

[saturation]

Its a big problem with the Rigol's inherent noise and the potential for artifacts caused by the FFT itself, as we've discussed on eevblog in the past.  Its a reason I'll post scope images more than discuss it [ its also easy to do with the 1052E], you can see the signal vs harmonics+ noise for yourselves.  I also analyzed the maximum amplitude on FFT to see whatever harmonics are there and sometimes, not always, pick up a few distinct frequencies spiking over noise. So far the noise floor and/or specific frequencies are <= 1-5 mVrms for a fundamental at 1.4Vrms.  That's ~ <= 0.36%. 

The key issue is while one cannot be so sure what the specific harmonic components are without some sleuthing [they could be real or reflected aliases for example], if the harmonic outputs are near to zero [as expected in a sine response] its meaningful, once you also respect the limits of the 1052E's response and what FFT algorithms do.  Likewise, one can calibrate the FFT response by passing a reference wave to insure its anticipated harmonics, say of a square wave at the fundamental x 3,5,7,9,11,etc., happens as expected and compare it the frequency under test.  For example, if I see other blips at 1 MHz sine on the FFT using the 3x25 I'm not sure off, I examine a better 1 MHz sine from my Instek SFG-1003, which is calibrated and traceable [ so Instek says in the documentation].  Whatever difference shown is part of the distortion from the 3x25.

Right now for sine, the Instek and 3x25 are equal in quality, with the 3x25 better given it can go to 40 MHz +.

On square waves, the Instek is cleaner and jitter free.

Again, I'll post images and less theoretical discussion and would love to hear feedback or more ways to check my findings.

 

Prelim testing was done with an unmodified Rigol 50 MHz 1052E and its FFT.

i'm no expert, but i have a feeling doubt to rigol's fft.

Kids, mhz means nothing.  mHz would be millihertz (10^-3 Hz). But if you mean megahertz, then write MHz (10⁶ Hz, or 1000000000 times larger than mHz). If that is to inconvenient for you, what about another hobby or profession?

Even if I have no interest in a thread topic and I see BoredAtWork has posted something on it I open it up anyways.  Just so I can enjoy golden comments like this one.

sometime me too lazy press the shift/caps button, i just rely on my extra terestial intelligent to read people's post, but a good reminder... with the butt kicking word "kids".