I accidentally soldered the input + to sgnd on my chipamp 
I was replacing the R2 for a lower value of 10kR to lower the DC offset, but then I soldered the in+ to the wrong end of the resistor.
I turned the amp on and off multiple times and tested with source before I realized what I've done. I was getting nothing but buzzing from the speakers, then I resoldered the in+ and now I hear the amp working but very very quiet and with some noise.
So have I fried the chips, or could it be something else? Don't know where to start testing...
I think I need a
I was replacing the R2 for a lower value of 10kR to lower the DC offset, but then I soldered the in+ to the wrong end of the resistor.
I turned the amp on and off multiple times and tested with source before I realized what I've done. I was getting nothing but buzzing from the speakers, then I resoldered the in+ and now I hear the amp working but very very quiet and with some noise.
So have I fried the chips, or could it be something else? Don't know where to start testing...
I think I need a
I have the chipamp.com amp, changed a lot of it as you can see in the pic.
But I looked at my scheme once again and I stand corrected - I actually soldered the in- to the wrong side of my R2, NOT in+ to sgnd!
You can see what I did here, the dashed grey line is where I should have soldered IN- in the first place of course.
But I looked at my scheme once again and I stand corrected - I actually soldered the in- to the wrong side of my R2, NOT in+ to sgnd!
You can see what I did here, the dashed grey line is where I should have soldered IN- in the first place of course.
An externally hosted image should be here but it was not working when we last tested it.
It could be the speakers or the amp or both...
What you have done will have caused a huge DC offset and that will have been applied to the speaker. Has it survived ? You need to check with another or check that speaker on a known good amp.
The chio may also have fried and been damaged. Check the DC voltage on pin 3 which should be zero. Also check R3 as that is low enough in value to be damaged by any rail voltage flying around. Also check that 2.7 ohm.
What you have done will have caused a huge DC offset and that will have been applied to the speaker. Has it survived ? You need to check with another or check that speaker on a known good amp.
The chio may also have fried and been damaged. Check the DC voltage on pin 3 which should be zero. Also check R3 as that is low enough in value to be damaged by any rail voltage flying around. Also check that 2.7 ohm.
The way you show it may have caused HF oscillation and can cause Rz to burn. This schematic is terrible. Without a coupling capacitor on the input and FB loop, any DC on the input will cause larger DC on the output and also disturb the bias current set by R2. Then there's that 2.7 ohm resistor returning the input signal to ground. Why? It is as if they are afraid to return the input signal to ground!
Ok, so I have to correct myself again - the speaker bought it, not the amp.
@Mooly - I confirmed the resistors are ok and measured DC on pin 3, which is 0.44v L and 0.19v R - same as DC offset at output - I guess this is ok?
I tried the test speaker again and found that it died. No worries, it's a cheapo
So the amp is working ok.
@johnr66 - I changed the original scheme after lots of reading here and suggestions made by more experienced members:
the 2.7R is a ground lift resistor, used for isolating signal ground from main ground, and I removed the Cin and Ci because the amp sounds WAY better without these. I just want a cheap tweaked amp, buying Mundorfs is not on the list yet. R2 was lowered from 22k to 10k because of high DC offset and works great.
And why exactly do you think that the scheme is terrible? Peter Daniel's premium kit also has no Cin, Ci, doesn't use R1, and all I hear is praise for it.
@Mooly - I confirmed the resistors are ok and measured DC on pin 3, which is 0.44v L and 0.19v R - same as DC offset at output - I guess this is ok?
I tried the test speaker again and found that it died. No worries, it's a cheapo
So the amp is working ok.
@johnr66 - I changed the original scheme after lots of reading here and suggestions made by more experienced members:
the 2.7R is a ground lift resistor, used for isolating signal ground from main ground, and I removed the Cin and Ci because the amp sounds WAY better without these. I just want a cheap tweaked amp, buying Mundorfs is not on the list yet. R2 was lowered from 22k to 10k because of high DC offset and works great.
And why exactly do you think that the scheme is terrible? Peter Daniel's premium kit also has no Cin, Ci, doesn't use R1, and all I hear is praise for it.
The input "lift" resistor is nonsense. The input signal still has to flow in the ground circuit. Putting a small resistance there that is a tiny fraction of the input impedance does nothing. Keeping the heavier supply and output currents out of the input ground path via star grounding accomplishes that.
Because Cin and Ci probably would have saved your speaker.
You should always check for DC offset after changes and before you hook up a speaker. Even better would be to have a DC detection and speaker protection circuit, since you're running a DC coupled amp.
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@johnr66 - well I've seen more than one implementation of this ground lifting by expert members here, so I wanted to try for myself, though I would have to test for any audible advantages - reducing noise would presumably be one of them.
@Redshift187 - so if I hook up a Velleman K4700 speaker protection unit, would that save me from using Cin and Ci?
Now my goal is to squeeze the best possible sound from the chip, and I think we all agree that "no Cin is the best Cin", apart from expensive Mundorfs and such. Right?
If you take into consideration that I actually use only one source at a time, and always measure for output DC, I think it puts me in kind of safe spot, and alows me to get the best sound.
I'm well aware that this is by far NOT the best practice of building amps, and that turning the source component on or off WHILE the amp is on - my speakers would probably die, at least after a few dozen times, because for example I measured DC of more than 4v on output when powering my portable mp3 player hooked to the amp...
@Redshift187 - so if I hook up a Velleman K4700 speaker protection unit, would that save me from using Cin and Ci?
Now my goal is to squeeze the best possible sound from the chip, and I think we all agree that "no Cin is the best Cin", apart from expensive Mundorfs and such. Right?
If you take into consideration that I actually use only one source at a time, and always measure for output DC, I think it puts me in kind of safe spot, and alows me to get the best sound.
I'm well aware that this is by far NOT the best practice of building amps, and that turning the source component on or off WHILE the amp is on - my speakers would probably die, at least after a few dozen times, because for example I measured DC of more than 4v on output when powering my portable mp3 player hooked to the amp...
I wish one of the experts would explain it. Why not return the output side to ground through a .22 ohm resistor as well? (makes as little sense to me) Its as if they are afraid to return the signal to ground when it has to flow there anyway.
There is a lot of audio wizardry here, but also a lot of audio foolery such as:
Circuits with missing parts that compromise reliability and safety.
Added parts of questionable purpose.
Pushing parts beyond datasheet absolute maximum ratings.
Buying on price only. You often get stuck with counterfeit parts. They might work at first, but can fail eventually.
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