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Old 19th September 2006, 03:30 AM   #1
Usher is offline Usher  Serbia
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Question STK4050V, for real!

Greetings,

At the moment, I'm working on a STK4050V power amplifier, and I've been browsing STK40xx related posts on this forum to get some info. I found some very useful informations, but still, there are a few questions...

Q-1. Thermal shutdown
Q-2. Load-short protection circuit
Q-3. Pop noise muting

The datasheet says that the amp supports addition of these electronic circuits. Are these circuits already in the schematics, or if not, does anyone have the schematics?

Q-4. Input signal voltage and impendance

Does anyone know the maximum input signal voltage in Vrms and nominal input impendance?

Q-5. PSU with voltage regulation

Can I use a PSU with positive/negatve float voltage regulators? is there anything bad about this idea? Resonances? Cooling problems?

Q-6. R15?

There is a Sanyo datasheet,
And also schematics I've found on this forum (attached);
There is one question- what is the purpose of the 100 ohm resitor R15? There is no such resistor in Sanyo datasheet...

Q-7. Stopping oscillations

rljones posted: this;
Should I change the input resistors from 1K/56K to 1K/20K, and why exactly? Where should I put that 200pF cap- between ground and which point in the schematics?

Q-8. Speaker impendance

What happens if a 4ohm speaker is connected? If I got it right, output resistors and PSU must be able to handle 2x the nominal current, right? And then the STK will burn out if it feels like it... And what happens if a 16 ohm speaker is connected? Evrerything should be OK, right?

Q-9. Part list

Considering the schematics and common sense, I have made this part list. Could someone be so kind to check the voltage and power ratings for the components?
  • R1 1K 2W 5% carbon film
    R2 56K 2W 5% carbon film
    R3 560 0.5W <1% metal film !
    R4 10K 2W 5% carbon film
    R5 56K >2W <1% metal film !
    R6 100 2W 5% carbon film
    R7 1K 2W 5% carbon film
    R8 100 2W 5% carbon film
    R9 .22 5W 5% ceramic
    R10 .22 5W 5% ceramic
    R11 .22 5W 5% ceramic
    R12 .22 5W 5% ceramic
    R13 4.7 5W 5% ceramic
    R14 4.7 5W 5% ceramic
    R15 100 0.5W lin trimmer
    C1 470p 500V ceramic
    C2 4.7u 160V electrolytic
    C3 100u 160V electrolytic
    C4 10u 160V electrolytic
    C5 100u 160V electrolytic
    C6 100p 500V ceramic
    C7 1n 500V ceramic
    C8 100u 160V electrolytic
    C9 100p 500V ceramic !
    C10 100p 500V ceramic !
    C11 10u 160V electrolytic
    C12 1u 350V electrolytic
    C13 0.1u 400V polyester film
Thank you all.
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Old 19th September 2006, 07:50 AM   #2
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Over kill on your cap voltage!!!!

C1, C2, C3 are all low voltage stuff like 1~2V so 10V caps are good for that and will save you some money and space.

C4, C5, C8, C11, C12 are way too high, suggested value on schematic is 63V which is way more than enough.

C6, C7 50V should be more than enough.

C9 and C10 should be double so if using a 50V rail, use 100V caps

C13 should be what is shown on schematic, 120V

Resister wqattages are way too high!!!!!

R9, R10, R11, R12 are good, leave them at 5W

R1, R2, R3, R4, R7, R15 could be 1/8W but 1/4 are easier too handle.

R6 and R8 are 1/2W as listed in schematic.

R5, R13, R14 are 2W, agin as listed in schematic.

Input voltage as stated above is about 1~2V max and Input imp. would be fairly high which is good.

Q-1,2,3 can all be done with on IC like the HA12001 (which is out dataed but good for examples) which can disconnect the load if the amp gets too warm (load = HEAT). It can also (because it uses a relay for load disconect) remove the load incase of amp shorting or disconnect load if load shorts. It also has a delayed on and almost instant off so pop noise is unheard of.

Sanyo recomends a 8 Ohm load so I wouldn't attemt any lower unless you want to lose a STK. High ohm speaker is easier for amp to drive but going from 8-16ohm will cut output power(W) in half.

Don't worry about Q-7 until you have built the amp then you can check for oscillation and fix it then.

Having a regulated PSU will not yeild a hole lot of inprovments for all the work and space that would be required.


BTW I have no Idea what R15 is for exactly, looks like a snubber network across pins 7 and 10? anyone want to correct or verify?
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Old 19th September 2006, 08:51 PM   #3
Usher is offline Usher  Serbia
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Default Possible oscillation problems in the near future...

Thank you for the info!

If I got it right, the IC HA12001 solves the problems of overheating, short protection and pop noise? I didn't mannage to find the datasheet, nor a single thread on this forum... Are there any better solutions? Any links?

Regulated PSU is not worth the effort? Is the float voltage regulator too bad? I guess that 10000-50000 uF cap will be enough?

Does anyone else know the purpose of R15? I'll put a 100 ohm/0.25 W trimmer and see what happens...

I'm working on a PCB at the moment, and I do things nice 'n' tidy; so I'd like to know where should I put that cap if it turns out that I will be needing it. And what about that input resistors???

Thanks...
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Old 20th September 2006, 03:03 AM   #4
Leolabs is offline Leolabs  Malaysia
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Nice to see someone still "in love" with Sanyo's STKs.
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Old 20th September 2006, 07:20 AM   #5
kmj is offline kmj  Sweden
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Quote:
Nice to see someone still "in love" with Sanyo's STKs
Are these old chips any good and how do they compare to newer stuff? I happen ta have 8pc of STK050 in my partsbin and it would be nice to know if they are useful for anything.
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Old 20th September 2006, 10:30 PM   #6
Usher is offline Usher  Serbia
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Default Good enough

Quote:
Originally posted by kmj


Are these old chips any good and how do they compare to newer stuff? I happen ta have 8pc of STK050 in my partsbin and it would be nice to know if they are useful for anything.
As a well-informed n00b, I think they are. Anything bad about 200 Wrms @ 8 ohms w/ RMS ~ 0.08% and 28 passive external parts? They are easy to build, easy to bridge, and need no extra tinkering, save for a tiny oscillation problem (at VERY low levels, like 1 mW or so) that I mentioned...

Newer stuff? What newer stuff? Am I missing something? Any better options for my 200 Wrms @ 8 ohms w/ THD <0.1% project than a STK4050V?

Take a look at this thread , especially rljones' posts...



C'MON GUYS, HELP ME OUT- AM I ASKING TOO MUCH?
-> WHERE TO PUT THAT 200 pF CAP ??? <-
I HAVE ONLY 10 DAYS LEFT OF MY SUMMER HOLIDAY TO FINISH THAT AMP!!!
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Old 20th September 2006, 10:36 PM   #7
Netlist is offline Netlist  Belgium
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Default Re: Good enough

Quote:
Originally posted by Usher

C'MON GUYS, HELP ME OUT- AM I ASKING TOO MUCH?
-> WHERE TO PUT THAT 200 pF CAP ??? <-
I HAVE ONLY 10 DAYS LEFT OF MY SUMMER HOLIDAY TO FINISH THAT AMP!!!
Cool down Usher, I know life is short.

/Hugo
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Old 21st September 2006, 02:04 AM   #8
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Default Re: Good enough

Quote:
Originally posted by Usher


C'MON GUYS, HELP ME OUT- AM I ASKING TOO MUCH?
-> WHERE TO PUT THAT 200 pF CAP ??? <-

I believe this cap goes from the right side of R5 to ground(the side of the resistor that goes to R9), thats the impression I get from the post you linkined in your first post.

BTW these stk amps sound just fine to me, the main problem is people either thinking these sound bad, heared it in a crappy design or are massive audiofies.

Oh and a newer up to date amp could be the TDA7293 (100W 120V 4-8Ohm load with low THD.)
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Old 22nd September 2006, 03:30 AM   #9
Usher is offline Usher  Serbia
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Default Thanks

Quote:
Originally posted by ifrythings



I believe this cap goes from the right side of R5 to ground(the side of the resistor that goes to R9), thats the impression I get from the post you linkined in your first post.

BTW these stk amps sound just fine to me, the main problem is people either thinking these sound bad, heared it in a crappy design or are massive audiofies.

Oh and a newer up to date amp could be the TDA7293 (100W 120V 4-8Ohm load with low THD.)
Thank you, you have been very helpfull! I got the same impression, I just wanted to chek...

A guy who owns a tiny music shop here in Belgrade, built a STK4048XI. We have compared it with Rowland 112 (if my memory serves me), with the same studio monitors, same mixer, same CD and same guitar. The two seemed pretty much the same to me, save for a bit smudgy-smeared basses (somewhere around 50Hz or so) on STK4048XI. BTW, this guy frowned on some harsh highs, but I wasn't able to tell the difference (I think I have a problem with highs )...

TDA7293 is a real beauty, but I need more power... STK4050V is the most powerfull single-chip amp that I know of... BTW, I'm building a bass guitar gig-amp, and since I play in a heavy metal band, the STK4050V is more than "fine" to me...
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Old 12th March 2008, 05:11 AM   #10
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Default One STK4050V Warm

Anybody can help...

I'v built 2 modules based on STK4050V schematic published here. At Normal Room Listening Level.. 1 of the module getting warmer but the other module not even warm..

both modules are working fine... only a low hum when no music. Powering up using +/- 53Vdc (from 36Vac Transfo 100VA).

Any suggestion guys.....TQ
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