Hello,
I have made this amplifier (Fig. 1) out of pure curiosity – I wanted to test a pair of brand new STK4042Xi ICs sold by Reichelt GmbH from Germany. My tests indicate that rumors about fake STK ICs are wrong, at least if you purchase them from reputable supplier. I don’t know who is producer and where the ICs were produced, but I can conclude, that the measurement data are consistent with the original SANYO technical documentation.
The product came as a positive surprise: both subjective impressions and measurement results are quite fine.
From the results below (Fig. 2) one can conclude, that based of these ICs it is possible to build a fine 80W Hi-Fi amplifier.
Measurements indicate that THD is consistently much lower than 0,1% and also that there is a very low noise floor. Measurement results of harmonic distortion present in a 1KHz and 10 KHz signal at 30W output are presented in Fig. 3 and 4, respectively.
To make this amplifier I have used:
For testing I have used:
Figures
Fig 1. A photo of the amplifier on the test bench
Fif. 2. Measurement results THD (+N) values at different power outputs, at 1KHz
Fig. 3. Measurement of the harmonic distortion present in a 1KHz signal at 30W output
Fig. 4. Measurement of the harmonic distortion present in a 10 KHz signal at 30W output
I have made this amplifier (Fig. 1) out of pure curiosity – I wanted to test a pair of brand new STK4042Xi ICs sold by Reichelt GmbH from Germany. My tests indicate that rumors about fake STK ICs are wrong, at least if you purchase them from reputable supplier. I don’t know who is producer and where the ICs were produced, but I can conclude, that the measurement data are consistent with the original SANYO technical documentation.
The product came as a positive surprise: both subjective impressions and measurement results are quite fine.
From the results below (Fig. 2) one can conclude, that based of these ICs it is possible to build a fine 80W Hi-Fi amplifier.
Measurements indicate that THD is consistently much lower than 0,1% and also that there is a very low noise floor. Measurement results of harmonic distortion present in a 1KHz and 10 KHz signal at 30W output are presented in Fig. 3 and 4, respectively.
To make this amplifier I have used:
2X STK4042Xi (Note that the suffix Xi indicates High Fidelity product)
1X PCB from Aliexpress (Tianle HiFi STK 4040-4050)
1X 400VA/230V toroidal transformer with double 30V secondaries
1X Heat sink (Fischer Electronics SK56 100, 0.4K/W)
List of components is in the attached .7z file
For testing I have used:
Oscilloscope Rigol DS1074Z-S Plus
Arta software
Sound card: Xonar U7 Mk II
Figures
Fig 1. A photo of the amplifier on the test bench
Fif. 2. Measurement results THD (+N) values at different power outputs, at 1KHz
Fig. 3. Measurement of the harmonic distortion present in a 1KHz signal at 30W output
Fig. 4. Measurement of the harmonic distortion present in a 10 KHz signal at 30W output
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Fake STK ICs are very real; at least in my country. Cheap & quite popular here as low-fi audio amplifier. Of course you don't have to worry about quality & authenticity if you buy from reputable supplier.
Thanks Radian!
In the category of chipamps I have compared it to XY LM3886! STK4042Xi is much better both in subjective perception tests and in measured parameters. This amplifier is equally good at low and highest power level - distortion doesn't lncrease substantially up to 75W. It also has very good performance at low frequencies (square wave and bandwidth tests). It is also important to note that STK4042Xi has low THD+N values at higher frequencies - I have presented results at 1KHz and 10 KHz. Refer to Figures 3. and 4. in the #1 post.
Also, Tianle HiFi STK 4040-4050 (See the attached figure below) board has everything you need to build a complete compact amplifier: power supply, speaker protection and Thiele network. I was affratd that just two 10.000uF capacitors wouldnt be enough and have used 20.000uF/50V instead. This amplifier does not have any undesirable sounds. With no signal at the input it sounds like turned-of.
The only problem is availability of genuine STK4042Xi. I am aware that there is a large number of fake chips available from unreliable sources. Just read post #2.
I have read somewhere that ON Semi have acquired Sanyo facilities and that these chips can be purchased from trustworthy suppliers. At Reichelt, I have paid 25,43 € each, but original chips. Quality (reputation) has price.
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