AliExpress cheap low distortion analog sine generator - review and measurements

[pma]

AliExpress cheap low distortion analog sine generator - review and measurements

I bought this generator from AliExpress at $16.50 (shipment and VAT included). The product page is below:

https://www.aliexpress.com/item/1005009069241437.html

1. Info from aliexpress page:

Feature:
1. 1KHz sine wave output with a distortion coefficient of only 0.000064%, suitable for high-precision testing applications.
2. Ultra low distortion design, with distortion less than 0.001%, ensuring signal purity and stability.
3. The power supply is ± 15V, with a current of only 30mA, making low-power operation more efficient and energy-saving.
4. Output voltage greater than 7V, suitable for harmonic distortion testing, level testing, and regenerative power supply scenarios.
5. Adopting the NE5532 chip, it has good performance and effective use.
Product parameters:
Power supply: ± 15V, 30mA
Output voltage: greater than 7V
Distortion: less than 0.001%
Dimensions: 90 * 49mm * 16mm

Product Description:
Low distortion coefficient sine wave oscillator circuit board, oscillation frequency: 1 KHz, ultra-low distortion, distortion coefficient 0.000064% (-124dB). Can be used for harmonic distortion testing, level testing, regenerative power supply, etc.
The capacitors that control the oscillation frequency on the board are selected and paired using a digital meter. The resistor that controls the oscillation frequency is a 3.3K resistor and a 200 ohm 3296 multi turn potentiometer connected in series. The pairing is adjusted by measuring with a digital meter to ensure the accuracy and low distortion of the output frequency.
matters needing attention:
In theory, R10=2R13， C3=2C4， Minimal distortion.
2. The data in the figure is a value of 1KHZ. If there are other frequencies, besides R6, R7, C1, and C2 that need to be adjusted accordingly, R11 should also be modified according to the frequency.
For example: 50HZ, R11=447K, 60HZ, R11=408K.
Product List:
1X module

2. My additional description
The generator arrives as an assembled printed circuit board with through hole parts. It needs 2x15V (+/-15V) power supply, which is not a part of delivery. After connecting to power supply, it starts to run and gives 7Vrms approx. output voltage at single-ended output terminals. If the output voltage is too high, it may be reduced by external resistor voltage divider. The web page shows circuit schematics, you may see it in the attached pdf file.

3. Measurements
I connected the generator to a 2x15V external power supply and measured the output with E1DA Cosmos ADC at 10V input setting. Without further adjustments, output frequency was 934 Hz, output voltage 6.983Vrms, THD = 0.00011% and THD+N = 0.00022%. SNR = 114dB. These are excellent results for analog generator and especially at such price.

4. Conclusion

For those who need a cheap and clean sine generator, this is an excellent choice. Most of the soundcards are unable to generate such clean signal.

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Edit September 04 - I have placed the generator board into a shielded box and the 50Hz mains line has c0mpletely disappeared:

 

[staticV3]

Nice find!

113.15dB SINAD for those wondering

 

[mhardy6647]

Is it photographic artifact, or are the DIP sockets and the Phoenix terminal connectors on that PCB actually as askew as they seem to be?

 

[pma]

Wide angle lens proximity distortion. And not very careful positioning before soldering.

 

[pma]

Nice find!

113.15dB SINAD for those wondering

Remember - with 45kHz measuring bandwidth. It is even better with 22kHz, as always.

114.9 dB @BW22kHz

 

[mhardy6647]

Wide angle lens proximity distortion. And not very careful positioning before soldering.

Noting that the 8-pin DIP ICs are (or appear to be) socketed...
Just one word, Benjamin.
Rolling.

Boutique ICs will enhance the analog warmth of those sine waves, I'll betcha.

 

[pma]

Noting that the 8-pin DIP ICs are (or appear to be) socketed...
Just one word, Benjamin.
Rolling.

Boutique ICs will enhance the analog warmth of those sine waves, I'll betcha.

They are socketed. However, the 5532 used is the best choice. Of course I have immediately tried the LM4562. The result was bad, with nasty spectrum due to induced instability. I have described the same issue in another thread.

 

[pma]

I have placed the generator board into a small, well shielded Al box. The 50Hz mains line, that was induced by air coupling, has completely disappeared.

This just reminds to importance of proper shielding. Please also note that the "jitter" 50Hz components near the base frequency line have disappeared as well.

 

[phofman]

The question is what frequency drifts of an analog oscillator do to high-resolution FFT (i.e. with tiny bin width), especially with averaging.

 

[pma]

@phofman : Sure. 09/03/2025 Fo = 933.82 Hz, 09/04/2025 Fo = 933.79 Hz. Small uncertainty might be (maybe) seen in spectrum widening below -140dBr. Is it important for brief testing of an amplifier? I do not think so, but correct me if I am wrong. I also tried a long term run, with similar results.

 

[phofman]

I do not know what your FFT size is, but that difference could be across several FFT bins. But REW does some advanced interpolation of results between bins, maybe it has no effect. But without some advanced bin recalculation I would not trust results of high-resolution FFT analyzing slowly-drifting signal - e.g. collecting samples for one pass can take several seconds during which the frequency would move within the bins, affecting the result even for one pass. And results are calculated from a single bin (in simple FFT use, with no drift handling).

 

[pma]

This is a continuous exponential averaging for 1 minute in Arta, with parameters included.

 

[phofman]

Do we know how Arta handles the frequency shift? My 2 cents no handling because it does not seem to even measure the fundamental.

@JohnPM Please can you explain details how RTA in REW handles slow frequency drifts of analog oscillators? Thanks a lot!

 

[pma]

I still do not understand your concerns, because the frequency shifts are in 0.01Hz order. I have long wav records of the gen output. Then it is compared in Deltawave with digitally generated sine of the average generator frequency and you can check ultra low frequency beats. Still I do not see how it affects amplifier testing.

 

[Torin Krell]

My late 1940s Altec AS-1600 analog signal generator still works perfectly after I made a simple internal adjustment. I picked it up at a vintage video game store a decade ago for $12.

 

[SSS]

For the low cost it is an excellent oscillator. My more expensive 1 kHz oscillator from Viktor in Latvia seems to be slightly better and for my measurements sufficient. Atached the FFT measurement display and the oscillator picture plus the circuit schematic. Part of the distortion may be due to the limits of the QuantAsylum QA403 measurement instrument. Last display is the loop back measurement of the QA403 oscillator. For further comparison the FFT of my old Sound Technology ST-1710A distortion measurment instrument. There the limit can be seen although before Audio Precision this instrument was widely used.

 

[pma]

My late 1940s Altec AS-1600 analog signal generator still works perfectly after I made a simple internal adjustment. I picked it up at a vintage video game store a decade ago for $12.

I have some analog generators as well, like this one:



It has range from 10Hz to 1MHz, which is fine for quick testing. However, the best THD = 0.003% and only in 1kHz - 10kHz range. This is 30x worse than this little generator tested here and does not allow for distortion measurements even that of average commercial amplifiers.

 

[pma]

For the low cost it is an excellent oscillator. My more expensive 1 kHz oscillator from Viktor in Latvia seems to be slightly better and for my measurements sufficient.

Nice. May I have a small question? Are you able to get rid off those mains multiples, this is from my view important. It tells me how good is the PCB design, shielding and measuring system arrangement. And, THD+N seems to be higher (I read -105.61dB), though this cheap AliExpress thing measures better than -115dB! Victor generator seems to have -125.98dB THD, Aliexpress has -120 to -119dB. So, you have lower THD, but higher noise and less clean spectrum regarding mains frequency and its multiples.



BTW, the schematics is quite similar:

 

[SSS]

Nice. May I have a small question? Are you able to get rid off those mains multiples, this is from my view important. It tells me how good is the PCB design, shielding and measuring system arrangement. And, THD+N seems to be higher (I read -105.61dB), though this cheap AliExpress thing measures better than -115dB! Victor generator seems to have -125.98dB THD, Aliexpress has -120 to -119dB. So, you have lower THD, but higher noise and less clean spectrum regarding mains frequency and its multiples.

View attachment 474243

BTW, the schematics is quite similar:
View attachment 474244

For my easy meas setup I could go little bit better regarding mains hum. At this low level I cannot really fast find out where it is injected. There I would need to invesigate with screening cases and probably better power supply aka batteries. Attached the latest FFT. But as I said part of the distorion may come from the QA403 since Viktor claimes somewhat of -160 dB THD or so. Found that even at a distance of half a meter the small power supply transformer coupled into the circuits. Further away I could get the hum into the noise floor. See the second attached file just below this text.

 

[pma]

Thank you for your reply. The generator should be quite immune to its physical placement, this might depend on shielding efficiency. I am also a bit confused by the modulated noise floor in your last plot, it might indicate to frequency instability or the window used.