as weird as it may sound, if mine are fakes, i'd have peace of mind knowing there's still a chance to make the circuit work with minimal 'rework' if i can order genuine ones. but my friend told me he got these from digikey. oh well, i might as well order a couple more.
i tried the circuit that you showed me. loaded 33kohms, 20k, 10k down to 150 ohms. for some reason, the wave still remains the same??
however, i tried putting a couple of .047uf mylar caps parallel to the load resistor and i was able to get a significant change in waveform without significant change in level.
here's the waveform as it originally exits pin1 even with different load resistors.
after putting caps in parallel with the resistor.
then i tried it to the circuit i replicated. here's the original waveform @ pin1
after putting caps @ pin1 to gnd
what's your take on this mooly?
however, i tried putting a couple of .047uf mylar caps parallel to the load resistor and i was able to get a significant change in waveform without significant change in level.
here's the waveform as it originally exits pin1 even with different load resistors.
after putting caps in parallel with the resistor.
then i tried it to the circuit i replicated. here's the original waveform @ pin1
after putting caps @ pin1 to gnd
what's your take on this mooly?
I really think these IC's are very very suspect...
Could they be comparators badged as 4562'S ? Something like that might account for the gross distortion. The "crossover" distortion at the centre of the waveform is big clue all is not as it should be. I think a comparator would actually behave like that if used as a linear amp. A small cap such as 0.047uF is just acting as an integrator and "taking the rough edges off" and causing the output to slew rate limit.
I can't see any other explanation tbh.
I was trying to look at the picture of it. Very hard to say I know. Worth rubbing with alcohol or even really fine wet/dry paper and seeing if anything is underneath.
Another worthwhile test. Just measure the current into pin 8 with no load and no signal. My data sheet say the LM4562 draws 10ma typically, maximum of 12ma. See what it actually is.
Could they be comparators badged as 4562'S ? Something like that might account for the gross distortion. The "crossover" distortion at the centre of the waveform is big clue all is not as it should be. I think a comparator would actually behave like that if used as a linear amp. A small cap such as 0.047uF is just acting as an integrator and "taking the rough edges off" and causing the output to slew rate limit.
I can't see any other explanation tbh.
I was trying to look at the picture of it. Very hard to say I know. Worth rubbing with alcohol or even really fine wet/dry paper and seeing if anything is underneath.
Another worthwhile test. Just measure the current into pin 8 with no load and no signal. My data sheet say the LM4562 draws 10ma typically, maximum of 12ma. See what it actually is.
hi mooly,
did the current draw test. i think we may have found the culprit. either they're all toast (tested 18 units) or they could be something other than a 4562.
without load it draws .65mA. i tried loading it and giving 8kHz input signal, it goes to 0.7mA.
i tried the 4558 in place and it did 1.75mA unloaded. still far from the 3mA spec but given the unit to be nearly 7yrs old i don't worry much about it. plus it works as it should when placed in the crossover.
the 4560 draws a respectable 3.6mA unloaded so i guess it is within spec.
so, do we have the culprit??
i may want to order another batch of 4562 myself. together with the 2134 . i'm thinking mouser if they have some, digi key lists 0 in their available quantity.
did the current draw test. i think we may have found the culprit. either they're all toast (tested 18 units) or they could be something other than a 4562.
without load it draws .65mA. i tried loading it and giving 8kHz input signal, it goes to 0.7mA.
i tried the 4558 in place and it did 1.75mA unloaded. still far from the 3mA spec but given the unit to be nearly 7yrs old i don't worry much about it. plus it works as it should when placed in the crossover.
the 4560 draws a respectable 3.6mA unloaded so i guess it is within spec.
so, do we have the culprit??
i may want to order another batch of 4562 myself. together with the 2134 . i'm thinking mouser if they have some, digi key lists 0 in their available quantity.
I had forgotten about this... been here before
http://www.diyaudio.com/forums/digital-source/171998-op-amp-swapping-2.html#post2344847
Look at the scope piccys.
http://www.diyaudio.com/forums/digital-source/171998-op-amp-swapping-2.html#post2344847
Look at the scope piccys.
Look at the ebay link and picture in post #11 here,
LM4562 opamps are terribly noisy - Page 2 - The Art of Sound Forum
Same code as yours I think.
LM4562 opamps are terribly noisy - Page 2 - The Art of Sound Forum
Same code as yours I think.
whoah! those are same waves as mine!
anyway, i'll be getting some more caps and opamps. just found out mouser ships to my country through fedex with an estimated delivery of 3 days ($40.00). i hope it will arrive next week.
too bad we got bad ICs. my friend started re-building his 4 way crossover with SOIC lm4562 in browndog adapter to replace the rc4136 and it's showing the same problem and scope waves as mine.
thanks for all your help mooly. i really appreciate it. i'll update this thread once i get the parts.
anyway, i'll be getting some more caps and opamps. just found out mouser ships to my country through fedex with an estimated delivery of 3 days ($40.00). i hope it will arrive next week.
too bad we got bad ICs. my friend started re-building his 4 way crossover with SOIC lm4562 in browndog adapter to replace the rc4136 and it's showing the same problem and scope waves as mine.
thanks for all your help mooly. i really appreciate it. i'll update this thread once i get the parts.
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