I have a Denon POA-220 stereo amplifier that I use
to monitor an audio interface when running Windows.
This interface does not work under Linux, But I have
a Scarlet 2i2 that does. I tried using a Radio Shack
stereo switch to change the amplifier source between
the two interfaces, but it introduced noise.
So I noticed that the amp has two RCA inputs for each
channel:
https://tinyurl.com/mrxzrwuf
one marked "CD" and the other "NORMAL". I'm tempted
to use these to connect both interfaces at once, but
something tells me that may not be a great idea. There
are no input switches on the amp. The only controls
are power, and speaker A/B switches.
My main interface is a Presonus 1810, with the older
USB connection. It seems that the USB-C version is
supported by Linux, but I can't get my version to work,
although I do see some Alsa devices (but not the outputs)
in the mixer.
Toby
It's actually a POA-2200. I found a block diagram:
https://imgur.com/a/ivhcMCR
Not sure why the low-pass filter on the CD input.
Other than that, using both inputs would be like
using a 'Y' cable, which I understand is a no-no.
Interesting.Imgur won't let me see that as I am in the UK. I suspect
that our online safety law has come into play. Amplifier porn. ;-0
I'm curious though, if I were using this amp with
a CD player, how would I control the volume? As I
said, there is only power and speaker A/B on the front.
Surely they don't expect one to reach around the back
and adjust both gain knobs.
Interesting.Imgur won't let me see that as I am in the UK. I suspect
that our online safety law has come into play. Amplifier porn. ;-0
Probably the URL shortening service. I guess I should stop
using those.
https://imgur.com/a/denon-poa-2200-block-diagram-ivhcMCR
Toby
It's actually a POA-2200. I found a block diagram:
https://imgur.com/a/ivhcMCR
Not sure why the low-pass filter on the CD input.
Other than that, using both inputs would be like
using a 'Y' cable, which I understand is a no-no.
Maybe the filter gives enough isolation that it
would still be possible? Or perhaps there is more
circuitry involved that does not show up on this
diagram that would make it ok.
I'm also not sure how to set the input level knob.
I just have them at half-way right now. If it controls
gain, I would think that the minimum level that gives
me the output I need would be best.
I'm curious though, if I were using this amp with
a CD player, how would I control the volume? As I
said, there is only power and speaker A/B on the front.
Surely they don't expect one to reach around the back
and adjust both gain knobs.
Toby
On 12/26/25 07:09, Tobiah wrote:
I have a Denon POA-220 stereo amplifier that I use
to monitor an audio interface when running Windows.
This interface does not work under Linux, But I have
a Scarlet 2i2 that does. I tried using a Radio Shack
stereo switch to change the amplifier source between
the two interfaces, but it introduced noise.
So I noticed that the amp has two RCA inputs for each
channel:
https://tinyurl.com/mrxzrwuf
one marked "CD" and the other "NORMAL". I'm tempted
to use these to connect both interfaces at once, but
something tells me that may not be a great idea. There
are no input switches on the amp. The only controls
are power, and speaker A/B switches.
My main interface is a Presonus 1810, with the older
USB connection. It seems that the USB-C version is
supported by Linux, but I can't get my version to work,
although I do see some Alsa devices (but not the outputs)
in the mixer.
Toby
On 26/12/2025 15:43, Tobiah wrote:
It's actually a POA-2200. I found a block diagram:Interesting.Imgur won't let me see that as I am in the UK. I suspect
https://imgur.com/a/ivhcMCR
that our online safety law has come into play. Amplifier porn. ;-0
Not sure why the low-pass filter on the CD input.I'd expect a low cut filter on the normal input to reduce rumble.
Other than that, using both inputs would be like
using a 'Y' cable, which I understand is a no-no.
The block diagram in the service manual shows a hi cut filter on the CD input.
(a 7.5 k Ohm resistor in series with a 270 pf capacitor which is in
parallel with a 50 K Ohm potentiometer.
A quick check shows it may be designed to stop any clock frequency
leakage from the DAC, as the -3dB point is above 78 kHz.
Curious as to how a simple mechanical switch (slide ?) could 'introduce noise'. Unless close to a powerful electro-magnetic field such as an external power supply, or close mains cabling.
| Sysop: | Angel Ripoll |
|---|---|
| Location: | Madrid, Spain |
| Users: | 13 |
| Nodes: | 8 (0 / 8) |
| Uptime: | 295:29:57 |
| Calls: | 1,105 |
| Calls today: | 1 |
| Files: | 1,388 |
| D/L today: |
1 files (3K bytes) |
| Messages: | 71,557 |