STK chips

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bubu

Member
Joined 2004
A response to Joey Bancroft (and the others)

I used +/- 82V, 15A, 20000 uF per rail. As for the wattage of your resistors you can follow the schematic wich is self explanatory. It is the same schematic I used to draw the pcb. I didn't change anything, I just built it as it is. It worked from the first start and I still use it to get my neighbours crazy. For the rest of the resistors you can use 0,5 to 1w. It's up to you. Also make sure your capacitors are not under 100V. You'll also find here the speaker protection circuit I use and a very simple and easy to build wattmeter from Velleman.
 

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B

bubu

Member
Joined 2004
A response to Joey Bancroft (and the others)

The protection circuit... Intrare=Input, Iesire=Output. Right?
From SR1 you can adjust the level where your speakers will be disconnected from the system. It will do soft start with 3 seconds delay, DC protect and overpower to skpeakers. The minimum power required is 6W. It does not protect you from short circuit and it was designed for diferential power supply. So don't use it when bridging! When you make the SR1 adjustments put a resistor as a load to your amplifier.
 

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B

bubu

Member
Joined 2004
A response to Joey Bancroft (and the others)

And the wattmeter... For 400W change R13 to 1K and so on. I will upload the pcb for this gizmo as soon as I will find the CD i put it on. You can get the complete manual from www.velleman.be
And how the hell I can attach more than one image per post?
 

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speaker

speaker

Member
Joined 2004
Da5id4Vz said:
I'm not sure that this amp has been discussed before in the forum or not, but I'm pretty sure that it uses an STK chip.

I think it gives a nice reference to what can be achieved with these chips and what the value of the finished product is.

http://www.ird-thailand.com/products/mb100/mb100.htm

Can anyone verify my assumption about the STK chip?
Click to expand...


I don't believe it is. Check the language for this relative to the MB100:

TDA7293

They seem to be saying the same thing.

speaker
 
E

ElectroPower

Member
Joined 2004
powerpt.net
Hi guys!

First, I have been fascinated with STK4050V, so great hibrid!

Just a correction for bubu, the output power of STK4050V isn´t 200W RMS (8 ohms), they are musical power. One more information the output power could be between 312W and 350W! (4 ohms of course)

Attention, this Watts is in Musical Watts, not RMS Watts! :bigeyes:

Good projects
 
B

bubu

Member
Joined 2004
No kidding? You dissapoint me ElectroPower. A man with a such nice site to have no idea about OHM's LAW!
You said:
"the output power of STK4050V isn´t 200W RMS (8 ohms), they are musical power. One more information the output power could be between 312W and 350W! (4 ohms of course)
Click to expand...
Where did you come up whith these values from?
You have any idea how to calculate RMS power according to Ohm's law? Here's an excerpt: P=UxU/Z
RMS (root mean squared) power is a statistical averaging method of the power delivered by a sine wave at some arbitrary low THD (total harmonic distortion) level. "Low distortion" usually means "at the onset of audible clipping". For a sine wave, the voltage is the sine wave's peak voltage divided by the square root of 2 (approx 1.4) , and the resistance is the speaker impedance. So an amplifier that gives 57 volts peak ( I measured around 57 to 59 Volts at the STK4050V output - that's 41 volts peak to peak for the positive and negative halves of the sine wave) into an 8 ohm speaker gives a power of:
57/1.4 = 41 volts, 41 x 41 = 1681, 1681 / 8 ohms = 210 watts RMS. According to the same equation, for 4 Ohms you get around 420W RMS. Clear enough?
Don't forget that STK4050 and most of the STK chips are 8 ohm not 4!
And I used this amp to drive 2 paralel 8 ohm speakers per channel(when one channel of my main amp blewed) and it performed very well. It was a wedding event. But i wonder - was it 200W or 350 at the output of the amp? You tell me!
See ya
 
E

ElectroPower

Member
Joined 2004
powerpt.net
Hi,

forgive me, I was wrong and this had to have view of the internet an wrong information about the STK4050V AND I know the ohm law!!!, I think that here in Portugal the teens learns yourself in the 2 secondary school, already I do not remember when I learned it, long time ago...!

Yes, the power is right, I analyzed the circuit with correct datasheet (original)... yes, you have reason.

Well, thanks for the comment about my site :)

Good projects
 
B

bubu

Member
Joined 2004
BTW. The 2000W schematic on your site is the Elektor Titan 2000 amplifier. "Current feedback topology that delivers 300w - 8ohms, 500w - 4ohms or 800w - 2 ohms and is 1.5ohms stable. Delivers 1.6kw into 2ohms bridged". You can find the link with complete schematics around this forum. If I will have the time I will send them to you.
 
E

EWorkshop1708

Member
Joined 2004
I have an amp I'm using for a 12" 4 ohm subwoofer, and I'm getting over 200W RMS.

The Module is an STK4231-II

I parallelled the two channels together to make a single 4 ohm mono amp, and I was very impressed on how hard it drives my sub.

The amp is running on +- 55V rails.

I'm impressed with the STK modules.

Has anyone upgraded their modules with a pin-compatible model with a higher wattage rating (better SOA)??? I've thought about trying that.
 
S

sasmit

Member
Joined 2006
rljones said:
It is interesting that you should make this post, as I was about to start a thread on these hybrid op amps.

A few months ago, I made a pcb for the STK4048XI. [As an aside, this device has full complementary outputs; the 'V' versions, as opposed to the 'XI' versions, are quasi-complementary. A smaller module, the STK4044XI, has 4 output devices and 15 pins; the STK4048XI, 6 output devices and 18 pins. You can ignore the last 3 pins on the '48 if you put a '44 into the same circuit, so design for the 18 pin versions and you can go with either unit.]

Anyhow, I had so many problems that I became frustrated and put them away: horrible oscillation that I could not stop despite trying all sorts of things with the grounding, etc. However, after a friend of mine fried one of my amps, I decided to attempt making a couple of STK modules to put into the damaged unit. This weekend, I finally figured out the problems, one of which is hinted at on the application docs by Sanyo, and another which I accidentally discovered and yet seems very important.

The main secret in stopping oscillation is to keep the gain at 40dB. I don't like amps with this much gain as the input sensitivity is around 0.4 V for full power. This kept me from getting rid of the oscillation as I had initially changed the input resistors from 1K/50K to 1K/20K, and never looked back.

Once you get the gain up, to the suggested 40 dB range, almost all oscillation stops. The amp then looks very good on the scope, except for a little bit of something on the sine waves. (BTW, I used all of the parts suggested on the app docs, various 100pF caps, etc to avoid oscillation as Sanyo warns.) This where the application docs stop. What I found was that there was still oscillation, but at VERY low levels, like 1 mW output into 8 ohms. [And I'm now wondering if this low level oscillation is what has given these guys a back name, particularly with respect to longevity. Any amp that oscillates will overheat and eventually burn-out the output devices.]

At these low levels, the oscillation took off again. I tried all sorts of stuff to fix it: bypassing the feedback resistor with small caps like 10 to 200 pF, changing the input blocking caps, but nothing helped--until the other evening. I was looking at th scope ready to go to bed when I started holding a 200 pF cap across the feedback resistor when the oscillation completely disappeared. But I'd made a mistake, it turns out I'd actually put this capacitor from the amp output side of the feedback resistor to pin 3 going to ground.

In other words, by placing a 200 pF cap from the amp output to ground (but at low current level location; I didn't use the output terminals), the remaining oscillation stopped. The amp then looked absolutely perfect and all distortion dropped 10 dB, especially at low levels. The heatsinks were now cold when idling; before they were warm but this was due to overlooked oscillation.

This STK4048XI produces, with a +/-55 V supply that sags to 50V at full output, 140 W into 8 ohms and 220 W into 4 ohms. Freq response is -0.4 dB at 10 Hz to -2 dB at 100 kHz (limits of my equipment). Distortion (THD) is 0.8mW is 0.08% at 1kHz, 0.025% at 1W, 0.007% at 10W. At 20 kHz and 10W it is 0.035% and only 0.1% at 10W at 50 kHz.

As for sound, it initially sounds very good, not as open or airy as my Rowland amp, but very good. The input needs adjustment: my initially listening was done with an input transformer, which I think may be a mistake on this amp (I was still trying to cut that incredible gain...). Once I get it going, and properly set up, I'll compare it to a Tripath 104, a Rowland, and a homebrew Aleph.
Click to expand...



I have had quite some experience with the stk modules starting from stk 435...439 459...to the new generation 4xxx's..They were very good when there was nothing around..I mean no LM's and very few TDA's..but now with so many choices there are better options.Most of the STK's we get in India ...mostly are fake ! The 435..459 etc sounded really good I built quite a few for my friends to use with their Gaming PC's.
 
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