O
Olaf Marzocchi
Hi to all,
I'm building an audio amplifier with the TA202 chip (it's simple to
solder at home and sounds great) for home use.
I'd like to use a digital potentiometer as volume control and a digital
switch to select the inputs (4 way will be enough).
My problem is that I'm a bit inexperienced, so I don't know how to put a
pot like DS1802 (audio pot from Maxim) in the circuit Tripath shows in
the datasheet.
I'll try to draw the circuit here, if it's not clear this is the link:
http://www.tripath.com/downloads/TA2020.pdf.
OUTSIDE | INSIDE
|
+- R2 --|OP-AMP OUT
| |
input --- C -- R1 -+-------|INV
| |
V \______/
AC, maybe L---> high pass filter: no more DC
with Dc
bias
Inside the chip there is an opamp that takes INV and a constant signal
as input, it's output is the OP-AMP OUT (obviously, OP-AMP OUT is only a
feedback, not the only output).
OP-AMP OUT------+
|\ |
INV---| \ |
| \ -----+---amplification
2,5V--| /
|/
The TA2020 gain is: constant*R2/R1.
(I hope not to write obvious things).
The digital pot does not allow AC inputs/outputs, so I cannot put it
instead of R2, since it is connected to R1 on one side and in R1 flows
an AC signal.
How should I modify the circuit? I'd like not to put the digital pot
simply after R1, since it would change the high-pass filter and it would
attenuate the signal (less dynamic range), not set the gain.
As far as it concerns the audio input selection, I think I will read
what is already available in sci.electronics.* before asking. However, I
will probably have the same problem: the switch will accept DC inputs
while I have AC inputs.
Thank in advance to anyone! I hope to be able to build my hi-fi soon! (I
have already designed the circuit board, the gain and the switches are
the only things left).
Olaf Marzocchi
I'm building an audio amplifier with the TA202 chip (it's simple to
solder at home and sounds great) for home use.
I'd like to use a digital potentiometer as volume control and a digital
switch to select the inputs (4 way will be enough).
My problem is that I'm a bit inexperienced, so I don't know how to put a
pot like DS1802 (audio pot from Maxim) in the circuit Tripath shows in
the datasheet.
I'll try to draw the circuit here, if it's not clear this is the link:
http://www.tripath.com/downloads/TA2020.pdf.
OUTSIDE | INSIDE
|
+- R2 --|OP-AMP OUT
| |
input --- C -- R1 -+-------|INV
| |
V \______/
AC, maybe L---> high pass filter: no more DC
with Dc
bias
Inside the chip there is an opamp that takes INV and a constant signal
as input, it's output is the OP-AMP OUT (obviously, OP-AMP OUT is only a
feedback, not the only output).
OP-AMP OUT------+
|\ |
INV---| \ |
| \ -----+---amplification
2,5V--| /
|/
The TA2020 gain is: constant*R2/R1.
(I hope not to write obvious things).
The digital pot does not allow AC inputs/outputs, so I cannot put it
instead of R2, since it is connected to R1 on one side and in R1 flows
an AC signal.
How should I modify the circuit? I'd like not to put the digital pot
simply after R1, since it would change the high-pass filter and it would
attenuate the signal (less dynamic range), not set the gain.
As far as it concerns the audio input selection, I think I will read
what is already available in sci.electronics.* before asking. However, I
will probably have the same problem: the switch will accept DC inputs
while I have AC inputs.
Thank in advance to anyone! I hope to be able to build my hi-fi soon! (I
have already designed the circuit board, the gain and the switches are
the only things left).
Olaf Marzocchi
