STK4141 on batteries

[Mooly]

If your worried about offset issues just try it, with no speakers connected and say 24-0-12 or 12-0-24 and measure.Untill one or other rail drops below a value that causes internal constant current sources and voltage references to function correctly, the STK will "behave" as a normal op amp.
Lead acid batteries won't give much imbalance anyway. Fully charged say 12.5volts on load, totally discharged say 11volts. It's a non issue.

[Zoodle]

Thanks Mooly. I was concerned the chip might be damaged, but it seems that's not likely.
I'll measure outputs as you suggest. Thanks again.

[hipanni]

Hi,sakis . This is kannan .Your wrong. Most of stk series ic's better while using proper protect circuit and eq or driver circuits.This ic is cheaper and available in any country,very easy designing. Just thing about it.

[sakis]

Originally posted by hipanni
Hi,sakis . This is kannan .Your wrong. Most of stk series ic's better while using proper protect circuit and eq or driver circuits.This ic is cheaper and available in any country,very easy designing. Just thing about it.

i have nothing to say against what you wrote

proper protect is a n outside thing and there is no point talking about here
cheap yes available yes ...any country yes ....very easy design double yes pcb also triple yes !!!!

but the diference from a descrete amp tha will play 1000 times better and is going to be more of an excersize more dofocult to design and make pcb

but it will play alot better than any stk ....and if the bias is too litle you can crunk it up any time you like ...and so on and on and on

[sangram]

Watch that chip, Sanyo stopped production a decade ago and the only replacements are fake, as most chips in my country are today. I have two 12-year old STK4191s still in active service and though they're tough chips, the sonics are terrible. Good enough for cheap compact stereo, but I agree that a proper discrete circuit will be way better, or even a more modern chip like the LM3886.

24/0/24 would be fine for the 4141, these chips are essentially discrete amplifiers (hybrid construction, so they use actual semiconductor dies inside the package). They are openable and repairable, though a very hot iron is required. I remember someone here used to do that, and mentioned that the substrate sucked up heat very fast.

As for asymmetric rails, difficult to tell. The STKs expose some of the current mirror stages to external components, and the bootstrap as well. There are quite a few resistors that hang off the pins apart from the usual input/output/mute, and those have internal connections to the input and output stages. I don't really know if it'll cause an issue, and I'm not too keen to experiment as I only have these last two chips (and a project they need to go into).

You'll have to try it on a dummy load or open circuit (STKs have no problem with open circuit).

[hipanni]

Hi sakis,

yes your thought is 100% right . But during experiment other ic is not use because it's circuit is veri sensitive in small variation ic failiur. But stk series ic stands while small variation. Me also use stk ic past 5 years i done experiment using tone control with stk ic. To still its working. But other ic's not stand.please reply me .




BY


kannan

[Zoodle]

Originally posted by sangram
As for asymmetric rails, difficult to tell. The STKs expose some of the current mirror stages to external components, and the bootstrap as well. There are quite a few resistors that hang off the pins apart from the usual input/output/mute, and those have internal connections to the input and output stages. I don't really know if it'll cause an issue, and I'm not too keen to experiment as I only have these last two chips (and a project they need to go into).

Hi Sangram. I was hoping you would post.

I might postpone the battery experiment, despite Mooly's reassurance; although my STK cost me $0, I can't afford to replace it at the moment.

Instead, I'll move the transformer into a separate case (an old ATX P/S case). The transformer is currently positioned directly beneath the amp board, which can't be ideal.

BTW
Should I be adding 'bypass caps' across my smoothing caps? If yes, what type should I be looking for? I recently added extra capacitance -- some old "6800"mF caps added to the existing "3800"s (the aggregate measures just over 9,000mF each side). I've read that you're supposed to 'bypass' them. I admit I don't really understand it. Again, my priority is safety of the chip.

[sangram]

Contentious, the 'snubber' theory is. But I kind of just add them in, I don't see any harm and they cost nothing. It's more important to add some bypass at the chips. The STK reference PCBs don't have any bypassing closer than 4 inches near the pins, and the pinout means it's not possible to get too close, specially to the negative pins, but I manage a few caps an inch away or so. Not optimal, but helps a lot.

For the 'snubbers' I use 100nF ceramics, or 33nF polyester caps with a 1 ohm, 1 watt metal film resistor. For chip bypass it's usually a 10uF Panasonic FC, or a 100uF FM, and a 100nF X7R ceramic SMD soldered directly on the power pins.

All the 'snubber'/bypass do is reduce the inductance of the large caps, or the PCB tracks bringing in the supply respectively. this is supposed to improve HF performance but in truth I haven't been able to spot much difference wit or without them.

Don't worry about your chips, mine have proved that one can abuse the STKs and get away with it. I have had mine oscillating due to poor layout, and have run them bridged into 4 ohm loads, an impossible task for most amps. Now I respect their age, and they only do light and occasional duty, till my active line arrays get going with them performing most of the heavy lifting...