STK series amp modules- any good?

flyingtele · 30th June 2009, 06:23 PM

Hi people,
I am looking to build myself a small stereo power amp based on the STK integrated amp modules, I think they are made by Sanyo?
Anyway, I am looking for any advice anyone has on them, and opinions from people who have used them.
I am currently thinking of either using the STK-443 which is rated at 25+25 W at 8 ohms and a Vcc of 49V, or a couple of STK-084 or -086 which are mono and rated at 50W and 70W respectively at 8 ohms, and a Vcc of 35V and 42V respectively.

I personally would rather use two mono units, simply for the extra power and the fact there are less components packed into the case. I have heard that the stereo modules can be run mono in bridge mode, but I don't know how it affects their tone or reliability. Also, can I run these amps in parallel?

I want to use chip amps because of their compactness, as the case I have is limited in space. I'm not going to be spending a fortune on this project, I just have a really attractive wooden cabinet and chassis and faceplate from an old 70's stereo amp that was fried, and I just want to replace all the internals with modern stuff so it is still useable and doesnt sound awful.
If anyone has anything helpful to add, by all means do so

Josh

mjf · 30th June 2009, 09:11 PM

hello.
some years ago i have used the stk 439 and stk 460.and i had a receiver with stk 084g and a fisher amp with stk4171.........
the sound was acceptable...............but i think they die suddenly when there is a short at the output.
nowadays i prefer the national lm types (1875,1876,3886......) over the stk's, because they are cheap,tiny,easy available and with a good psu they sound amazingly well.
greetings................

sangram · 1st July 2009, 05:41 AM

The STK modules don't sound very good, and have too many external components (they run a bootstrap externally, as well as some part of the current mirror I guess). This usually makes for messy layouts.

With some care one can lay it out for minimal ground noise (the PCBs in the datasheet are terrible!), but the fidelity is still pretty low. I find the LM series sounds a whole lot better, even some of the TDA chips have better sound.

Most STKs currently available are fake, Sanyo stopped production quite a while ago. You're either getting NOS or NOK-OFF. Caveat Emptor.

I've used a lot of their amps in the past (41xx, 43xx) and at the time (90s) there were no chips available to compete with them. But there are better options now for sure.

And the STKs absolutely collapse in bridged mode. I was running a pair of STK4191 as bridge amps for a long time. I pulled it out for a listen recently, and I was appalled at the sound.

I would really look at something else, and this is coming from an ex-STK fanboy.

flyingtele · 1st July 2009, 06:00 AM

according to their spec sheet, they can tolerate a shorted load for 2 seconds, buts still thats only on paper

digi01 · 1st July 2009, 07:06 AM

i have made stk439 and stk465 poweramp at the time (90s).i would like stk465 chip.

today i will use lm series (4766,3886,1875) or go for solid stage.

Zoodle · 1st July 2009, 09:56 AM

Flyingtele,

Not sure if the following is any use to you, but here's my take on one particular STK:

I have a STK4141-II (part of an old Sansui receiver). I don't know how that compares to what you're looking at.

So far, I've bypassed everything but the tone controls. Not even an input selector or Vol (I'm controlling volume at my FLAC player, which is my only source). I'm running 90mm full-range, near-field monitors.

At the moment, the STK won't go loud without taking on a hard edge and losing bass depth, control and tune.

At lower volume I'm getting a lot of detail and 'ambiance.' It's toe-tappy and moderately tuneful -- even in the bass. A couple of hours warm up makes a big difference. I have some bigger P/S caps to fit -- hopefully that will help too.

Maybe I wasn't expecting much from something I found on the street, but I am impressed.

On the other hand: look at all the user feedback on the National chips.. People really love them.
When I get some money, I'll be trying one for myself.

flyingtele · 1st July 2009, 10:12 AM

Sweet, thanks for your help. Ill probably opt for an LM series chip amp from National. Can I run two off one power supply if its properly regulated, and has big enough rail caps and a transformer with enough juice?
Some amps work fine like that, yet others like the ETI 480 don't seem to like it.
As previously stated, its not for ultimate hi-fi, rather just bringing an attractive old amp back to life with new circuitry. For the pre amp I plan on using an LM1036 chip which is a stereo volume-bass-treble-balance control all in a single package.

AndrewT · 1st July 2009, 12:22 PM

Quote:

Originally posted by flyingtele
Can I run two off one power supply

of course you can.
and it does not need to be regulated.

Why do want to spill juice in/on it?

ali05314 · 1st June 2012, 06:47 PM

Hi dears i am newone to this forum
i have stk 086 but i dont have its pcb, someone post its pic
thanks
Ali

Tomom · 6th June 2012, 03:24 AM

There is a huge number of STK power output modules, with diferent toppologies, so is their quality (sound). STK4048XI is a very good one, 16 transistors in all with long tail pair and current mirror; I made amp with it and sound great, lot of power (150W) and good bass...STK084, 086 have much simple design with 9 transistors ...good for guitar amp...

30th June 2009, 06:23 PM	#1
flyingtele diyAudio Member Join Date: Jun 2009	STK series amp modules- any good? Hi people, I am looking to build myself a small stereo power amp based on the STK integrated amp modules, I think they are made by Sanyo? Anyway, I am looking for any advice anyone has on them, and opinions from people who have used them. I am currently thinking of either using the STK-443 which is rated at 25+25 W at 8 ohms and a Vcc of 49V, or a couple of STK-084 or -086 which are mono and rated at 50W and 70W respectively at 8 ohms, and a Vcc of 35V and 42V respectively. I personally would rather use two mono units, simply for the extra power and the fact there are less components packed into the case. I have heard that the stereo modules can be run mono in bridge mode, but I don't know how it affects their tone or reliability. Also, can I run these amps in parallel? I want to use chip amps because of their compactness, as the case I have is limited in space. I'm not going to be spending a fortune on this project, I just have a really attractive wooden cabinet and chassis and faceplate from an old 70's stereo amp that was fried, and I just want to replace all the internals with modern stuff so it is still useable and doesnt sound awful. If anyone has anything helpful to add, by all means do so Josh

1st July 2009, 07:06 AM	#5
digi01 diyAudio Member Join Date: Mar 2003 Location: BEIJING	i have made stk439 and stk465 poweramp at the time (90s).i would like stk465 chip. today i will use lm series (4766,3886,1875) or go for solid stage. __________________ 2010 DIY ALBUM UPDATED UCPv1(preamp) & DUAL(power supply)

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30th June 2009, 09:11 PM	#2
mjf diyAudio Member Join Date: Jan 2009 Location: upper austria/near linz	hello. some years ago i have used the stk 439 and stk 460.and i had a receiver with stk 084g and a fisher amp with stk4171......... the sound was acceptable...............but i think they die suddenly when there is a short at the output. nowadays i prefer the national lm types (1875,1876,3886......) over the stk's, because they are cheap,tiny,easy available and with a good psu they sound amazingly well. greetings................

1st July 2009, 05:41 AM	#3
sangram diyAudio Member Join Date: Sep 2002 Location: India	The STK modules don't sound very good, and have too many external components (they run a bootstrap externally, as well as some part of the current mirror I guess). This usually makes for messy layouts. With some care one can lay it out for minimal ground noise (the PCBs in the datasheet are terrible!), but the fidelity is still pretty low. I find the LM series sounds a whole lot better, even some of the TDA chips have better sound. Most STKs currently available are fake, Sanyo stopped production quite a while ago. You're either getting NOS or NOK-OFF. Caveat Emptor. I've used a lot of their amps in the past (41xx, 43xx) and at the time (90s) there were no chips available to compete with them. But there are better options now for sure. And the STKs absolutely collapse in bridged mode. I was running a pair of STK4191 as bridge amps for a long time. I pulled it out for a listen recently, and I was appalled at the sound. I would really look at something else, and this is coming from an ex-STK fanboy.

1st July 2009, 06:00 AM	#4
flyingtele diyAudio Member Join Date: Jun 2009	according to their spec sheet, they can tolerate a shorted load for 2 seconds, buts still thats only on paper

1st July 2009, 09:56 AM	#6
Zoodle diyAudio Member Join Date: Jun 2009	Flyingtele, Not sure if the following is any use to you, but here's my take on one particular STK: I have a STK4141-II (part of an old Sansui receiver). I don't know how that compares to what you're looking at. So far, I've bypassed everything but the tone controls. Not even an input selector or Vol (I'm controlling volume at my FLAC player, which is my only source). I'm running 90mm full-range, near-field monitors. At the moment, the STK won't go loud without taking on a hard edge and losing bass depth, control and tune. At lower volume I'm getting a lot of detail and 'ambiance.' It's toe-tappy and moderately tuneful -- even in the bass. A couple of hours warm up makes a big difference. I have some bigger P/S caps to fit -- hopefully that will help too. Maybe I wasn't expecting much from something I found on the street, but I am impressed. On the other hand: look at all the user feedback on the National chips.. People really love them. When I get some money, I'll be trying one for myself.

1st July 2009, 10:12 AM	#7
flyingtele diyAudio Member Join Date: Jun 2009	Sweet, thanks for your help. Ill probably opt for an LM series chip amp from National. Can I run two off one power supply if its properly regulated, and has big enough rail caps and a transformer with enough juice? Some amps work fine like that, yet others like the ETI 480 don't seem to like it. As previously stated, its not for ultimate hi-fi, rather just bringing an attractive old amp back to life with new circuitry. For the pre amp I plan on using an LM1036 chip which is a stereo volume-bass-treble-balance control all in a single package.

1st June 2012, 06:47 PM	#9
ali05314 diyAudio Member Join Date: Jun 2012	Hi dears i am newone to this forum i have stk 086 but i dont have its pcb, someone post its pic thanks Ali

6th June 2012, 03:24 AM	#10
Tomom diyAudio Member Join Date: Dec 2010	There is a huge number of STK power output modules, with diferent toppologies, so is their quality (sound). STK4048XI is a very good one, 16 transistors in all with long tail pair and current mirror; I made amp with it and sound great, lot of power (150W) and good bass...STK084, 086 have much simple design with 9 transistors ...good for guitar amp...