STK4151 Stereo Amplifier

[Anton Joubert]

Hi There , I have a old (Sentimental) Amp with the stereo amplifier STK4151 X (22Pin) which has gone faulty , I now want to replace it with a STK4151 II (18 Pin).
Where can I search for the PINOUT configuration of these components , or has someone done this exercise before who can give me some guidance ?

 

[Nigel Goodwin]

Haven't you considered using google?

STK4151 Datasheet, PDF

STK4151 Datasheet. Part #: STK4151II. Datasheet: 104Kb/2P. Manufacturer: List of Unclassifed Manufacturers. Description: 2-CHANNEL AF POWER AMP. 5 Results. Part #: STK4151V. Datasheet: 379Kb/5P. Manufacturer: Sanyo Semicon Device.

www.alldatasheet.com

Depending on the manufacturer of the amplifer there 'may' even be a manufacturers sheet on replacing the module with a later repair 'kit', Kenwood commonly did that. However, it's not usually that trivial a replacement - think fitting the module upside down, wiring each pin by hand, and adding various components - the kits usually came with a small PCB that held the extra components.

In my opinion those modules were a REALLY poor idea, I can only imagine they priced so cheap to the amplifier manufacturers that they couldn't turn them down.

 

[unclejed613]

having looked through this: https://pdf1.alldatasheet.com/datasheet-pdf/view/116247/ETC1/STK4151X.html on pages 10 and 16 you will see that to match the pinouts, you need to leave the first two and last two holes on the original board empty... if the board has ceramic caps connected to the now empty pins, you will want to test the amp carefully with the "light bulb test" (connecting a 60-75W INCANDESCENT bulb in place of the main AC line fuse) and turning the amp on. if the bulb lights up and stays at medium or high brightness, check the amp for oscillation with an oscope. if the bulb goes dim, everything should be ok, disconnect the bulb and put the fuse back in... the light bulb acts as a nonlinear current limiter to keep things from frying if there's a problem. even if those caps aren't there, it's still a good idea to power up the first time with a bulb limiter.

 

[schmitt trigger]

Sanken was the world’s leader in hybrid circuits.
It offered catalog and custom solutions that, from an OEM point of view, were very appealing. They were found everywhere in consumer electronics.

From the repair point of view, as Nigel mentioned, not so much.

 

[ACharnley]

They were used in the Beolab 1 and 9, so weren't considered poor quality.

 

[Nigel Goodwin]

They were used in the Beolab 1 and 9, so weren't considered poor quality.

They were 'so so' quality really, I remember one of the electronics magazines did an article about how to improve them.

Being used by B&O isn't a terribly great recommendation anyway, as it's only average stuff - basically just a fashion statement, and a long way from serious HiFi. Generally their 'mechanicals' were good though, with some of the controls on TV's etc. been exceptionally nicely designed.

MANY manufacturers did use them though, although normally only on the low end ranges. When I bought my Kenwood amp, I specifically got one that didn't use those modules - so more power, less distortion, higher quality, and much greater reliability.

 

[ACharnley]

You say that till you own them, the design work and CNC'ing on the tower pieces is second to none and still unmatched by anyone. The resin moulding they introduced in the 80's is still generally unmatched today, they put no ceiling on research and design. There were sacrifices made in placing design first, you could never get real bass extension from tower speakers. On the electronics front, the A/B amplifiers in the Pentas are considered by many to be the best ever made for the wattage classificiation, and B&O were the first company to stick Class D amps in their actives - over 20 years ago now. Hardly average.

The THD figures for the BL1 and 9 were excellent and used these amps, one for midrange and one for the tweeter. Much of it is the externals like power supply as you already know I'm sure.

 

[Nigel Goodwin]

You say that till you own them, the design work and CNC'ing on the tower pieces is second to none and still unmatched by anyone.

Like I said, good mechanicals - but electronically and technically not so good.

B&O are considered a 'fashion statement' than a serious audio manufacturer, hence their lack of reviews and advertising in the HiFi magazines - much like Bose really.

I've repaired a fair amount of B&O over the years, nothing very exciting about it, average gear in posh cabinets - 'designer' electronics.

 

[ACharnley]

If serious audio manufacturer is sticking three none precision cones in a wooden cabinet with some cross-over elements and charging an absurd amount where hardly any of that has gone into R&D and manufacturing capabilities, I'll go with a so called electronically and technically not so good fashion statement which has had a huge amount spent on R&D and manufacturing capabilities.

Bose is crap, you get little for your money.

 

[Nigel Goodwin]

If serious audio manufacturer is sticking three none precision cones in a wooden cabinet with some cross-over elements and charging an absurd amount where hardly any of that has gone into R&D and manufacturing capabilities, I'll go with a so called electronically and technically not so good fashion statement which has had a huge amount spent on R&D and manufacturing capabilities.

Bose is crap, you get little for your money.

The choice is yours, I wouldn't touch either, both far too much money for too poor a performance.

 

[ACharnley]

There in lies the difference with B&O, it's not just about performance. There is value in the engineering - four axis CNC machining for large chunks of aluminium is not cheap. They are the only consumer grade company that has seriously invested, the likes of Bose with their plastic moulds which anyone can do are meh. Good craftsmanship is worth something.

 

[Nigel Goodwin]

There in lies the difference with B&O, it's not just about performance. There is value in the engineering - four axis CNC machining for large chunks of aluminium is not cheap. They are the only consumer grade company that has seriously invested, the likes of Bose with their plastic moulds which anyone can do are meh. Good craftsmanship is worth something.

For a furniture manufacturer perhaps, but the audio quality isn't there - hence them not been a serious player in the HiFi market.

 

[ACharnley]

It isn't there with the smaller stuff, but (and audio quality is subjective) I would say it's definitely there with the larger models.

 

[Nigel Goodwin]

It isn't there with the smaller stuff, but (and audio quality is subjective) I would say it's definitely there with the larger models.

Even B&O probably wouldn't agree with you, which is why they don't try and compete in the quality audio market - it's basically a visual statement, for those who like that particular style, audio quality is less of a concern.

 

[ACharnley]

If that were true they wouldn't develop some of the best amplifiers in the business, or use drivers from the likes of Seas, as there'd be no point.

I own a pair of Beolab 1's. They don't have quite the bass extension that non-column speakers can offer, but otherwise they've outshone everything else I've compared them to (Q Acoustic, B&W among them).

 

[unclejed613]

but electronically and technically not so good.

their "ICE Amp" is a lot better than most other class D amps, primarily because they do have an effective feedback system that lowers distortion and output impedance to the levels of a good analog power amp. several other manufacturers use B&O ICE amps in their receivers and amplifiers. if i had weight constraints for an amplifier that ruled out anything other than a class D amp i would choose an ICE amp over anything else i have seen... that said, any class D amp is far more complex than an analog one, and so there's more that can go wrong with it... i can do the same job with a handful of transistors, with the major difference being heat sink weight because the analog amp dissipates more heat.

i first ran into STK packs in about 1977/78 when Pioneer began using the STK-0050 in their budget receivers. IIRC the STK-0050 was only a bias/driver/output stage and still required a diff amp and voltage amp on the PCB.