You need to see if there is any DC voltage on the output of the second OpAmps. If yes and it's more than a say 5 mv, the caps should stay.
The "first" 100uf... measure DC volts on it from the DAC.
Changing the 6K8 to 4K7 alters the AC response of that stage due to C352 and C353. You have increased the bandwidth... letting more HF "hash" through.
The "first" 100uf... measure DC volts on it from the DAC.
Changing the 6K8 to 4K7 alters the AC response of that stage due to C352 and C353. You have increased the bandwidth... letting more HF "hash" through.
I can understand I need some dc protection but only 1 set of capacitors should do fine ...
If I keep the set after the amplification it doen not matter that much if the is a little (amplified) dc voltage in front of it.
The first stage has little amplification so any present dc from the dac will be small.
If I keep the set after the amplification it doen not matter that much if the is a little (amplified) dc voltage in front of it.
The first stage has little amplification so any present dc from the dac will be small.
The DAC output "may" be at several volts by design... so measure it on the first 100uf cap to be absolutely sure.
The offset voltage of the opamps is an issue as well. With the caps in place there should ideally be zero DC volts at the output of each opamp. FET devices will give this, bjt's won't .
The offset voltage of the opamps is an issue as well. With the caps in place there should ideally be zero DC volts at the output of each opamp. FET devices will give this, bjt's won't .
In fact looking more closely at your circuit pin 13 of the DAC is shown as being at 2.5 volts... but measure it for yourself 🙂
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