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.-a 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:
-a https://tinyurl.com/mrxzrwuf
one marked "CD" and the other "NORMAL".-a I'm tempted
to use these to connect both interfaces at once, but
something tells me that may not be a great idea.-a There
are no input switches on the amp.-a The only controls
are power, and speaker A/B switches.
My main interface is a Presonus 1810, with the older
USB connection.-a 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?-a 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.-a I found a block diagram:
-a 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?-a 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.-a 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?-a 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.-a 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:
-a-a https://tinyurl.com/mrxzrwuf
one marked "CD" and the other "NORMAL".-a I'm tempted
to use these to connect both interfaces at once, but
something tells me that may not be a great idea.-a There
are no input switches on the amp.-a The only controls
are power, and speaker A/B switches.
My main interface is a Presonus 1810, with the older
USB connection.-a 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.-a I found a block diagram:Interesting.Imgur won't let me see that as I am in the UK. I suspect
-a 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: | Amessyroom |
|---|---|
| Location: | Fayetteville, NC |
| Users: | 54 |
| Nodes: | 6 (0 / 6) |
| Uptime: | 18:03:14 |
| Calls: | 742 |
| Files: | 1,218 |
| D/L today: |
4 files (8,203K bytes) |
| Messages: | 184,414 |
| Posted today: | 1 |