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450 2nd September 2006 05:41 AM

Help with Sanyo STK4211 Amplifier!
Hi everyone! (sorry long post skip 1st para 'cuz thats just me telling a rant/story :-p)

Alrighty, here's what went down. I have, err had this Aiwa NSX-V20 bookshelf system with a damaged 3 CD changer that I used for audio on one of my computers. One day however the sound was intermittent and sometimes got better if I jiggled the volume knob (which itself became jiggly that day). Today though, thw whole thing didnt play any sounds out of radio, tape or aux (for computer) and the volume knob was super jiggly. So I guessed that the volume pot needed replacing. Upon opening the thing, I saw it had one of those special motorized 50k volume pots and that it was okay. What wasn't okay however was the circuit board it was on. It completely broke off. Then I thoguht no amount of soldering would help fix the thing, but then I spot the STK4211 amp and then proceeded to disassemble the stereo.

So I got some info on the STK4211 here. I learn its a 15w +15w and thought then that it would be pretty cool to make my first speaker (or headphone) amp from this thing. So my question is... where should I start if it's even possible to use this thing?

BTW: I can read some diagrams and know how to solder and that sorta thing, and I'm a junior in high school so my budget and knowledge is limited! Oh, and I already have a Pioneer Elite A-35R for my main system in my room (which is equivalent to some of your guys' third or fourth systems. eek!) so this is just a project to screw around with and if it turns out well, an amp for my speakers/headphones for the computer.

Also, I did a search for "STK4211" and found nothing, is there something else I should be searching for?

Help apprieciated!

Thank You!

Nanook 3rd September 2006 08:03 AM

no help:-)
build the amp that Sanyo has on their data sheet/applications notes (from the link you provided..)

Alternately you could gut the Aiwa thingy, taking the power amp circuit board and power supply, and upgrade parts. One of the easiest things to do is to get a new potentiometer/volume pot (you need one anyways). Also buy some decent speaker connectors (5 way binding posts). There may be a surplus outlet near you, or consider Apex jr or similar . Get some decent hook up wire (solid core), and package it all in a cigar box (or whatever you can get your hands on). You may also need to choose from sources so some kind of selector would be needed as well as a power switch of some sort.

If the Aiwa was working, I'd hawk all the stuff from it if possible and rebox it. If you're happy with it then look at parts upgrades, and better enclosure etc, later on--- that way no or little $$ spent, and a pretty reasonable try at an amp.

Radio Shack used to sell a couple of nice little books explaining electronics with some basic projects. Also ask your dad, uncle, grand dad, librarian , --whoever if they have old copies of magazines. TAB books had several project books out years ago. Any of these will give you a start. The only caution that should be followed is 120 volts or less can do serious damage, etc. Always use common sense, fuse the ac input , and never open the unit up with 120 volts going to it.

Someplace on this site or others are basic guides for safety. Please follow them (check the Faqs section)

450 3rd September 2006 07:06 PM

Yeah, I've already gutted the Aiwa unit and I took the power amp unit and the PSU.

I have a question however... I think the Aiwa manual states the system as a 40w + 40w device, whereas the Sanyo power amp is only 15w +15w. Where is that extra 50w coming from? Because on the Sanyo STK4122 manual, it states 15w as a minimum but no maximum. So do different layouts somehow yield massively different wattage output?

I know some electrical safety as I did take an Electronics course in High School and I've worked inside of computers and projectors. But I'll certainly look for the books and read the FAQ.

450 3rd September 2006 10:08 PM

Sorry for double posting but I can't edit yet... :(

Okay that 40w + 40w thing I said was wrong. The speakers each can take 40w but the unit itself apparently produces 16wpc.

I do have a new question though, should I salvage the caps and resistors from the Aiwa unit by desoldering them, or should I just not bother and purchase new caps and resistors?

So far I think if I follow the plans from the Sanyo PDF and Nanook's ideas I need to buy some 5-way binding posts, circuit board, bread board (to test - is this a bad idea?), volume pot, some wire, and a case, right?

Nanook 4th September 2006 06:48 AM

power and other stuff..
Sanyo indicates that Vcc can be +/- 30.5, but recommend +/-20, note that that is based on 20Hz-20kHz at .4% distortion continuous. Many "power ratings" are stated as peak @1kHz, for 1 millisecond. That's usually a portable or car audio "trick".

A proper spec may look like this: 15 watts , 20Hz-20kHz no more that .4% THD . There may also be a error or variance listed as well, like +/- 3dB, 20Hx-20kHz, no morethan .4% THD.

As far as replacing capacitors, etc.. If you have the $$, and want to upgrade the existing amp, why not. My warnings regarding AC voltage safety is meant to remind you (or any reading) that AC voltage can kill and safety precautions should be taken, and common sense employed.
look here for some basic safety guidelines.

I guess "perf" board is what I would use, not breadboard. Perf board has solder pads, breadboard is just pushin.

450 4th September 2006 08:46 PM

I've labeled all of the resistors and capacitors I need to desolder from the Aiwa unit. I'll need to go and buy a perf board and desoldering tool from Radio Shack however.

The Psu needs to be replaced I think. It works fine, but the thing is I think it might be too powerful for the amp just by itself. The psu is 1.25 amps and 250 Volts. Eep. I know anything above 1 amp will kill, so i dont know if I should just play it safe and purchase a regulated PSU from R/S or not.

Nanook 4th September 2006 11:57 PM

the PSU...
ok, well if the thing is unplugged,. take it from the Aiwa and use it. If worried, make sure you fuse it, and enclose it in something (a plastic throw away "Glad" container or similar--yogurt container, anything to enclose it that is non-conductive.

The amp will only draw the current it needs, and a large PSU is more desireable than a small one. Just splice the power supply voltage lines making them longer. That way you will be getting DC, and it will be easy to take to the existing board. You could use alligator clips (sorry , RIP Steve Irwin, aka: the Crocidile Hunter, he was killed earlier today by a stingray barb to the heart). Modify the amp on the existing board, solder wire extensions and connect the potentiometer, and maybe a stereo source selector switch (double throw, double pole toggle?)

Once you know it works (you'll need to find the line in to the amp), and solder a couple of RCA connectors to them. Then hook up whatever you have for a source, to the stock Aiwa speakers, and give it a try.Once you know it works then I'd hit the local electtronics shop for some better stuff, the 5 way binding posts, etc. But don't spend too much. You may have the world's most expensive STK based amp. If ya get the bug, look at the Gainclones and other chip amps or Class D amps, and do a really nice job there :-)

tddodds 10th June 2007 12:12 PM

Are you still working on this amp?
I gotd one of these devices in surplus and thought I would make an amplifier out of it, so I would be interested in your experience with same. FYI if you still are interested, this chip is 7o watts per channel. Datasheet is at:

Tom: :)

artvipinosa 1st November 2011 10:25 AM

hey did you manage to complete this project?

i also have taken an power amp circuit and power supply of my sony stereo with STK4122II

i manage to connect the B+ B- Gnd INput L & R and also the output but i dont know why this does not produced sound... theres is 2 connectors on the board that i don't use the mute and the other one is that i don't know....

can you post some pictures how you do it... tnx.

this is i've got

Uploaded with

Uploaded with

is it ok to leave mute alone... and what is that pin between mute and L out?

hoping for help thank you

artvipinosa 1st November 2011 03:25 PM


Uploaded with

i have figured that that the pin between mute & L out is also GND...

my question now is that is it alright to leave the mute alone? or i need a mute circuit to make it work.

thanks again....

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