We may need some more information Stefan!
When you say that it is OK to start with do you mean that at the start of a track, where it usually starts quietly, the sound is OK, but when it gets louder, you get the distortion?
In other words is the distortion related to the level of content of the music?
When you say that it is OK to start with do you mean that at the start of a track, where it usually starts quietly, the sound is OK, but when it gets louder, you get the distortion?
In other words is the distortion related to the level of content of the music?
GC Distortion
My appologies. It was late; upon reflection my question was vague. The design is from the following link. http://f18.parsimony.net/forum31999/messages/38318.htm This is the inverted GC. The only difference is I realize now is that I don't have a 1uF cap between the pins 1 and 4. The supply is 25.5 V at 2.5A X 2 with 2200uf each at the chip. The pos and neg are floating. I did not however ground the cnter tap of each trans.
I power the amp and play music from my DVD Player or using my Sansui AU-D11 as a pre for phono, after less than a minute of breathtaking music from either source the amp distorts at all frequencies. All is well for 30 secs or so then fairly rapid distortion. The chips do not feel hot and i have done vibration tests and voltage/resistance tests. Nothing stands out. I am using homemade speakers using FE167 FR drivers. The only other thing I can think of is the 100K pot is a cheap RS dual audio taper. The pot however does not sound scratchy. I can for the brief time at the beginning run to very loud volumes without distortion. So as far as I can tell it is not a power dependent phenomena. Do I need a Zobel ntwk? If I am still vague on something let know.
Again Thanks,
Stefan
My appologies. It was late; upon reflection my question was vague. The design is from the following link. http://f18.parsimony.net/forum31999/messages/38318.htm This is the inverted GC. The only difference is I realize now is that I don't have a 1uF cap between the pins 1 and 4. The supply is 25.5 V at 2.5A X 2 with 2200uf each at the chip. The pos and neg are floating. I did not however ground the cnter tap of each trans.
I power the amp and play music from my DVD Player or using my Sansui AU-D11 as a pre for phono, after less than a minute of breathtaking music from either source the amp distorts at all frequencies. All is well for 30 secs or so then fairly rapid distortion. The chips do not feel hot and i have done vibration tests and voltage/resistance tests. Nothing stands out. I am using homemade speakers using FE167 FR drivers. The only other thing I can think of is the 100K pot is a cheap RS dual audio taper. The pot however does not sound scratchy. I can for the brief time at the beginning run to very loud volumes without distortion. So as far as I can tell it is not a power dependent phenomena. Do I need a Zobel ntwk? If I am still vague on something let know.
Again Thanks,
Stefan
Nuuk said:
Yes, it lowers the volume and then it cools a little and then up again.
Nothing to do with distortion.
Stefan, check the PSU caps and see if there's any mistake there, like wrong polarity.
Sometimes they don't blow in your face when mounted with the wrong polarity, but they do those strange things.
I also hope that you have the PSU caps near the chip's pins.
If you have them far away you may run into those problems.
fedde said:
Fedde,
I've been there.
Pushing the volume to silly levels, connected to 4 ohm speakers, I could hear the sound up-down-up-down (in intervals of just a few seconds).
It never completely cuts the volume.
This is the thermal protection in action, and that was when I had the chips mounted on the bottom of the case.
Now I mounted two heatsinks and it shouldn't happen again.
What I'm describing is documented on the datasheet.
The chip has other forms of protection that may act as you say.
Only had 3 types of distortion happen with the GC.#1 had the 1uf cap not hooked up correctly (all i was using , i have batt P/S).#2 amp went un stable.#3 drastic difference in the +/- P/S voltages(12.4 vrs 10.2). I have since fixed the voltage difference thing as i leave 2 trickle chargers on at all times, even when i play it. Also i leave the GC on at all times.
It would appear that i would get a junky P/S line but i dont , in fact it actually sounds better with the combined batt/charger P/S. I am even thinking about some additional caps at the batteries , maybe something on the order of 500-1000uf, and see if that sounds even better.On my scope i see no P/S ripple and the only time i see any movement is like when the fridge or AC kicks on then it drops and come right back up but it dosent appear to affect the sound.
ron
It would appear that i would get a junky P/S line but i dont , in fact it actually sounds better with the combined batt/charger P/S. I am even thinking about some additional caps at the batteries , maybe something on the order of 500-1000uf, and see if that sounds even better.On my scope i see no P/S ripple and the only time i see any movement is like when the fridge or AC kicks on then it drops and come right back up but it dosent appear to affect the sound.
ron
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