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View Full Version : Bugzilla Bug 1601: Additional "preamp" volume control for use with power amp



ephemere
2005-09-13, 22:19
This was marked fixed for target milestone 6.5. Does anyone know if the implemented fix is option #1 or option #2? (See the bug description.)

http://bugs.slimdevices.com/show_bug.cgi?id=1601

I'm hoping it's #2. The line outputs are mighty hot right now.

kdf
2005-09-13, 22:34
On 13-Sep-05, at 10:19 PM, ephemere wrote:

>
> This was marked fixed for target milestone 6.5. Does anyone know if
> the
> implemented fix is option #1 or option #2? (See the bug description.)
>
> http://bugs.slimdevices.com/show_bug.cgi?id=1601
>
> I'm hoping it's #2. The line outputs are mighty hot right now.
>
From the strings.txt file on the change that added this feature:

This is a secondary volume control which applies only to the analog
outputs on Squeezebox2. Enter the amount of attenuation in decibels.
Range is 0.0 to 63.0 in 0.5 db steps. The default is 0 (for full
volume). WARNING: if your amplifier is powerful enough to blow your
speakers, a receiver, preamp, or line attenuator should still be used
as a safety measure!

From that, given the analog only aspect, that it is option #2.

-kdf

seanadams
2005-09-13, 22:44
Correct, we are doing this as a digital function in the DAC. That may change in the future - we're exploring the options right now along with the needs for replaygain and such. There's a lot more info in this thread:

http://forums.slimdevices.com/showthread.php?t=16209

Feedback on this feature is welcome.

ephemere
2005-09-14, 00:22
Perfect! Just tried it and it works great.

ephemere
2005-09-14, 00:39
Oh, one bit of feedback on this feature. I assume the DAC chip uses all 24 bits of resolution for its internal attenuation control, while the volume control in the CPU uses only 16 bits (i.e., feeds a 16-bit signal to the DAC). If I'm right about that then it would be nice to be able to configure the SB2 so that the CPU's volume is fixed at max (40) and the volume buttons control the DAC's volume. With this configuration you'd lose volume control at the digital outputs but you'd presumably gain quite a bit of dynamic range at the analog outputs at low volumes.

dean
2005-09-14, 09:42
On Sep 14, 2005, at 12:39 AM, ephemere wrote:
> Oh, one bit of feedback on this feature. I assume the DAC chip
> uses all
> 24 bits of resolution for its internal attenuation control, while the
> volume control in the CPU uses only 16 bits (i.e., feeds a 16-bit
> signal to the DAC).
No, it feeds a 24-bit value to the DAC.

ephemere
2005-09-14, 10:15
> No, it feeds a 24-bit value to the DAC.

Oh interesting. Is this same 24-bit signal available on the digital outputs (for a 16-bit input signal)?

seanadams
2005-09-14, 10:23
> No, it feeds a 24-bit value to the DAC.

Oh interesting. Is this same 24-bit signal available on the digital outputs (for a 16-bit input signal)?

Yes

Please search the audiophile forum - there has been a lot of discussion already on this...