Sanken SK18752 Ampliier IC

[Ian Greenhalgh]

Hi folks

I pulled apart a broken Denon AV receiver a friend gave me in order to salvage some parts and among the useful bits I removed were two Sanken ICs - SK18752. There is no datasheet online and all I could find out was that it is a 50W amplifier for home cinema equipment and apparently needs a dual rail symmetrical power supply.

Anyone know anything about this IC? I'd like to make use of the two I have if possible.

 

[JonSnell Electronic]

Download the Denon service manual, you will be able to get data from the schematic.
Save you time, it is actually a re-badged LM1875.
http://www.ti.com/lit/ds/symlink/lm1875.pdf

 

[Ian Greenhalgh]

Cheers Jon, that's wonderfully helpful!

From the datasheet:

DESCRIPTION

The LM1875 is a monolithic power amplifier offering very low distortion and high quality performance for consumer audio applications.

The LM1875 delivers 20 watts into a 4Ω or 8Ω load on ±25V supplies. Using an 8Ω load and ±30V to supplies, over 30 watts of power may be delivered. The amplifier is designed to operate with a minimum of external components.

The LM1875 design takes advantage of advanced circuit techniques and processing to achieve extremely low distortion levels even at high output
power levels. Other outstanding features include high gain, fast slew rate and a wide power bandwidth, large output voltage swing, high current capability, and a very wide supply range. The amplifier is internally compensated and stable for gains of 10 or greater.

FEATURES

• Up to 30 Watts Output Power
• AVO Typically 90 dB
• Low Distortion: 0.015%, 1 kHz, 20 W
• Wide Power Bandwidth: 70 kHz
• Protection for AC and DC Short Circuits
Ground Device overload protection
• Thermal Protection with Parole Circuit
consists of both internal current limit and thermal
• High Current Capability: 4A shutdown.
• Wide Supply Range 16V-60V
• Internal Output Protection Diodes
• 94 dB Ripple Rejection
• Plastic Power Package TO-220

APPLICATIONS

• High Performance Audio Systems
• Bridge Amplifiers
• Stereo Phonographs
• Servo Amplifiers
• Instrument Systems

So it sounds like a useful chip, especially because it "is designed to operate with a minimum of external components." which suits me as I want to build a small, simple amplifier for my mum to listen to audio books and some music.

 

[JonSnell Electronic]

Same as the TDA2030/40/50 range of chips. Easy to use either single rail or dual rail supply.
http://www.ti.com/lit/ds/snas524a/snas524a.pdf
Page 2 shows a standard schematic, page 3 Single supply version.

 

[Ian Greenhalgh]

Yes, I looked a that schematic and I think I have all the components needed to build a stereo pair of them. I have a couple of 24-0-24 toroidal trafos I could use, they are only 0.5A but that might be enough as my mum will mostly be using headphones or a pair of small 8ohm speakers and only at low volume.

 

[PRR]

> 24-0-24 toroidal trafos

That makes +/-35V, 70V total, which appears to be in excess of the 60V spec.

At 0.5A it may sag bad on bench-test, but sitting near idle on Mum's table it is liable to die in months from voltage stress.

"Speakers at low volume" suggests finding the Single-Ended plan and feeding it single +36V and ground. Unless she favors the old Shiva subwoofer, 12 Watts ought to be enough for most mums.

 

[Ian Greenhalgh]

Thanks for the advice guys but it looks like this project is not going anywhere. I soldered on replacement pins to both ICs the tried them in my component tester and no go, they appear dead, so I've binned them and will use some of the pile of transistors I've accumulated instead.

Much appreciate the help though, cheers.