STK4044 Power up.

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I bought these PCB with all components installed. I would like to know more about powering these. At 100 watts RMS into 8ohms per module, I was told that ideally I would use a torroidal 38-0-38 250VA.
I do not need that much power. Would I reduce the voltage, current or both to make them around 50 Watts RMS. I would prefer not to attenuate and at full power, be the loudest that I will ever use with a nearfield monitoring situation. I would also like to know what signal power I need to drive these. The PCB has 2 STK4044XI. My hopes are to use this pair to bi amp speakers.
Thanks
 

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I would follow the data sheet for all the circuit details.
http://www.datasheetcatalog.org/datasheet/sanyo/STK4044II.pdf

Perhaps aim for around -/+45 DC which suggests a 30-0-30 tranny. The AC voltage will be higher at low load anyway. 50 watts RMS/8ohm is 28 volts RMS or 40 volts pk/pk.

Power up initially with a bulb tester... just in case there are any construction errors... it could save damaging the STK's

The "signal power" (you mean voltage) needed for full output depends on the values of the feedback components. Thats the 56K and 560 ohm in the application circuit. They give a gain of (56000+560)/560 which is 101. So for 28 volts RMS output you need to apply 28/101 which is 277mv RMS. In practice that means line level and a passive volume control.
 
Can I expect good results from these modules? I would like to drive a Dynaudio 17w75 from one module and a dynaudio D28/2 from the other. I am hoping to exceed the quality of my Blue sky that used Tip 35 and Tip 36. I do not need much power. I am always attenuated while working at my desk.
 
I am learning very much today. I have a few transformer lying around. I plugged one in and found it to have 30-0-30. I was feeling lucky! When I plugged in directly, My voltage went up. I had about -51 and +51. I thought that the light bulb was current limiting but obviously causes voltage to drop as well. I have another transformer here. It is 22-0-22. Would that be too weak to audition these Amps?
 
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The bulb is for limiting and as such will drop some voltage as current is drawn.

22-0-22 is perfectly fine, and you may find it gives all the output power you need in actual use. Probably around 40 watts RMS.

An added bonus is that the lower the supply voltage and the less heatsinking you need.
 
I have supply hooked up. It is sitting at -31Vdc and +31Vdc. All of these little details were so unexpected! I really thought that It would come easier than this. Then again, the reason that I left the automotive field to learn elcetronics was that I needed the stimulation. These recent projects have been far from swapping visibly scorched components and getting lucky 51% of the time.
Thanks so much!
 
WOW!!! This is my first finished circuit of any significance. It sounds like I am running out of current when I run it at higher levels. I am notiving more high frency energy than all of the other amps I have used on My Tag band 2 ways. Is it possible that something is lacking or is this the transparency I have been looking for?
 
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Without hearing it :) I wouldn't like to say what you are hearing :D

The next step would be to use a scope and confirm all is as it should be, but assuming you haven't access to one there are still a couple of things to check.

The power supply. Having confirmed it all works, I'm assuming your running it on full mains power now without the bulb. So check the rail voltage with your meter as you turn the volume up. The power supply should hold up without the voltage sagging.

The other thing is to check the grounding layout, In particular I would make sure that the speaker returns go directly back to the power supply and not to any points on the PCB.
 
Really? The negative speaker lead will connect to my ground between the capacitors and resistors? Got it. My rail voltages dropped to 29vdc when I turned up the volume. That was going to two two way speakers. I have it in my system now running from an active crossover, driving one dynaudio 6" per module. Plenty of power no drop in voltage. I found a bigger transformer with 30-0-30 it was on a 6 amp fuse. Tomorrow, I want to try to run my second pair of modules so that I have stereo bi-amp. I also found some 8200uF 50 Volt capacitors. Would they be better in the power supply than the 6800uF? I would like also in the near future to connect something such that I don't hear they power up and turning off.
If I didn't say it clear enough. THANKS!!! I am hearing transparency, detail, piano keys drift into oblivion instead of falling off a cliff. This setup blows away the Blue sky system ones that I paid dearly for as well as any other under $2000 near fields. I borrowed 4 channel car amp that my friend purchased for over $500 and it was not remotely close in terms of quality. I must say that my little old Orion car amp is handling the D28/2 well for now but ultimately want to get out of cheating by using Car amplifiers. I am just very excited about this amp you helped me to create.
 
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When it comes to grounding remember to think of each conductor be it wire or PCB print as a resistance. Ask yourself if the current flowing in that line can cause a problem if something else connects along its length.

This might give you some insight. Its a wandery thread but should help. Jump in at post #14 and 38

http://www.diyaudio.com/forums/solid-state/101321-3-stage-lin-topology-nfb-tappings.html#post1623053

The difference in real terms between 6800 and 8200uf is minimal and either should be fine. Going too large can bring its own problems too. The bigger the caps, the larger the charging pulses but over a shorter time. Remember the bridge rectifier conducts only at the "tips" of the AC voltage when the peak AC voltage exceeds the charge on the caps. Bigger caps droop less between each cycle but to put that energy back requires more current over less time. Small caps cause the bridge to conduct for longer (because the voltage on the cap has fallen more between cycles) but the peak current is less.
High currents increase "copper losses" in the transformer and can cause saturation and excess temperatures.

So in practice anything from around 3300uf to say 10,000 uf would be good.

For switch on thumps you need a simple reliable relay delay, something like this.
http://www.diyaudio.com/forums/solid-state/224957-simple-universal-speaker-delay-using-triac.html

There are some video clips of it working in post #24
 
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