Where stk 461 amp stand

[kaushik]

Long back i tried t assemble a STK 461 based Amp ...
That time i had very less knowledge about amps ..
still i started a STK 461 based Amp project ..

The schematics were published in EFY magazine ... glamorized as 360W PMPO AMP
i used a PCB with preamp stages included ...bought from a chennai based vendor .

The power supply was developed with 15-0-15A 5AMPs [ secondary..as per local guys specifications.. ] transformer
.. but the overall the AMP turned out to be very inferior interms of power ..
.... still the kit is at the native place . .. i wanted to know :

>As per the data sheet [link below]: Max power is only 20W RMS per channel or 10 + 10W?
>why the amp power is low as compared to ..that time popular LA4440 ...that take 12V @3Amps Supply

could it be ...counterfeit chip STK[ heard about counterfeit STK chips ] got /poor power supply ??

>where does it stand in comparison among chip amps of the same power category
in terms of quality /sound characteristics

Some web pointers also will be helpful


http://audiolabga.com/pdf/STK461.pdf

 

[nitinbose]

My Dear Friend,

Never consider amps with STK series chips; simply because of the fact that they are hard to source if a replacement is sought.

STK chips are made by Sanyo. They phase out the chips and release new ones as comparable to movie releases.

The circuit clearly mentions the output as 360Watts PMPO. PMPO is a fictitious measure of audio output. PMPO gives an impression of the audio power and often exaggerated by a factor of 10 or more. The best way to consider an audion output is the power at 0.1% THD over 20Hz-20KHZ. Once again, the quality of the preamp, the audio enhancers used would tremendously affect the quality of sound? Wonder how the "two-in-ones" fared, in the olden days - usually far superior as compared to most systems.

If you are looking for a quality amplifier, always consider a transistor/mosfet based amplifier, for they have the capacity to generate the current to drive the loudspeakers, while chip amps are for minor listening purposes, e.g. for a bedside stereo or computer speaker systems etc.

Whatever the case, the two major points to consider are:

(1). Are you looking for an amplifier for listening to music, in which case you would be better off buying one from a renowned manufacturer.

OR

(2). Do you want to learn how amplifier works? in which case you may expend your efforts in construction.

Thanks and regards,

Nitin.

 

[kaushik]

thank you nitin,

very good info you have given to me about STK ..these chips are obsolete items now a days

The amp with STK was my effort about 7 years ago .. yes I am aware of PMPO,preamps... etc ...as i am a regular visitor of sites like diyaudio . ...

only i wanted to know what i missed while building , is the chip is of any casual use(definitely not a audiophile grade..) ....

because that kit may be given a boxed shape..at spare time ...if it serves the
minimum purpose of some amplification with average sound quality.. with my new amp building knowledge !

 

[nitinbose]

Hi,

Indeed, chipamps may not offer an audiophile grade quality, for which you would have to go for a MOSFET based amp.

However, as mentioned earlier, the quality of audio again depends on the preamp and the controls. The lesser the distortion present at this stage would mean a better quality. The same goes for frequency response.

Sometimes, you may have a regular poweramp, but with a good preamp, matching high quality standards!

I remember seeing a Philips D6550 portable public address system. I do not know about the power output, but the speaker was rated at 15W and the power supply input was 35Watts, but setting the volume at level 2 of 10 was sufficient to literally "shake" the room - i mean it...

The old good days... to summarize with..

 

[soundsgreat]

Hi,

So Kuashik you know that its phased out Chip blah blah ! so won't tell you much bout that!

But will go straight to answer your main question,The STK chips were and are good in general sense but if you want a audiophile quality from them then the circuit design and components used will come into picture ! but in general they are good sounding chips,very easy to build ! as with comparison of STK vs LA, I think you've not heard the STK's in full glory thats why the comments !! coz noway will I compare the sound of LA to STK as STK is obviously better ! and yes its 20W per channel not 10 + 10 !

Hope this helps !

Now coming to Nitin's comment !

Indeed, chipamps may not offer an audiophile grade quality, for which you would have to go for a MOSFET based amp.

I think you obviously not know much about chip amps !! Am sorry if I sound bit harsh ! please excuse me.

The chipamps or Chips (IC as output devices) has come a long from their basic Avatars as small audio output device with only a few watts with TBA810 (regarded as revolution in those days) to nowadays several 100 watts !

The fact that the very same chips are being used by some of the Audiophile brands such JEFF ROWLAND,Krell etc is any indication and anything to go by, then I think its very very far from ruling out them as cheap alternatives to the almighty MOSFET's or BIPOLOR's !!

There are many such chips For Ex. there would'nt be a serious DIYer who hasn't heard about the gainclone amp ! this very very famous design uses National Semiconductor's LM3886 as the output device ! with this very same chip you build an Amp from 50W RMS to 300W RMS ( Multiple used in bridged mode) .

Another good one is the ST Mircoelectronics TDA 7294/95 where a single chip can provide 100W Rms power !

Now I won't even bother to compare the Slew rates of a discrete device to these Chips as that would not only make this a long post but also will be too hard to digest for an average person !!

Hope this throws some light on the subject !

Regards.

 

[kaushik]

quiet a informative reply shreekanth,
yes ,your answer clarifies my doubt to some extent .......
i have heard older SONODYNE amps used STKs so i am interested in these ..

Hi,

if you want a audiophile quality from them then the circuit design and components used will come into picture ! Hope this helps !


Regards.

i have seen a simple circuit around the chip ...
so i have to apply some MODs to the original circuit right! Any forum link or
any comments on that ?

for stereo power amp module with that STK ,
what are the key components that, i should ensure ,are of hi-quality to get full out of STK ....

my amp had some humming sound ...that i could not cure ,
i mounted it on a proper chassis , all wires are also properly shortened ,as i tested similar mounting with LA kit with no hum...

some one told,the hum noise is because , the power supply current is less than what the chip needs ..is it true?


lastly ,
will the 20+ 20W rms STK amp with existing kit will cost
more to built than a MOSFET based amp circuit ? [with hi Q components ...i cant estimate as i used local components that time ]






regarding the comment by nitin
" Indeed, chipamps may not offer an audiophile grade quality"

i think .. .. the statement may be read as "chipamps may not offer rich
sound output in some of the types of music or may be so in
for low budget DIY amps..and one has to go for MOSFET"

 

[surfatwork]

I echo soundsgreat's comments about getting a STK amp to deliver good quality sound by careful circuit design and component choice. But I would say such effort is likely to produce better results either by opting for a discrete amp (using mosfets or transistors) or by using a more contemporary IC like the ones mentioned in the earlier post. the target market for the STK was never audiophile sound quality - it was for the mass market. mfrs like akai and sansui used it a fair bit in the 90s.

 

[soundsgreat]

Hi,

Sorry Kaushik had missed your post hence didn't reply !!

For the STK there aren't that many mods one can do !! all you can do is to use high quality components like metal film resistors instead of carbon,usage of metalised polypropylene,silver mica and others instead of good old ceramic,a heafty power supply with atleast 15000 Mfd or above filter caps, a proper rated toroid transformer instead of lossy&hummy E&I !

These are few guidelines to followed in all Amp build using any kind of device !! if done this way the quality and the outcome will certainly be better !!

Now I wouldn't recommend you to waste money on this STK chip as this already a history and won't make a difference much ! I strongly recommend you to try out the LM series chip (they have replaced the LM3886 with 3942 or similar) or the TDA digital Dmos chip ! Am sure they are way better then the STK and will be of 100% Audiophile quality !

Check the below sites for the further details !

sjostromaudio.com - Home

Gainclone Gallery
(follow the links of the projects of each one)

A must know and know it all for above said LM based Amp !!Am not one of those people who copy paste stuff from different sites and claim it as their writing ! so here's the direct link
Gainclone FAQ (Frequently Asked Questions)

Hope is enough to start you into cooking mode !!

regarding the comment by nitin
" Indeed, chipamps may not offer an audiophile grade quality"

i think .. .. the statement may be read as "chipamps may not offer rich
sound output in some of the types of music or may be so in
for low budget DIY amps..and one has to go for MOSFET"

Kaushik please don't mind !! but what part of the my answer don't you agree or understand ?? you still think that the design engineers at those world famous brands don't know what they doing ?? otherwise how will you explain the sentence that you have quoted ??

As with the low budget DIY Amps its going to be of the same sound quality if you chose to ignore the facts that I've mentioned above !! so once you do that,it doesn't matter whether you go for a mosfet or a chipamp ! coz it will not matter in any case and sound bad anyway !

Regards.