'Analog Dinosaur' succumbs to the joys of FBA : enter Raspberry Pi 2/IQ-Audio DAC+!!

[Marco]

Could be, Chris. Either way, I wasn't getting much sound out. If the 'correct' mixer control can be found, then I'd be happy to use it instead, providing that I know how!

In any case, I'm pretty convinced now that the Pi/DAC sounds best, controlled via a digital web interface, without the use of an active preamp. Quite simply, in the latter scenario, if pre-amplification of the signal is occurring twice, then that is not a good idea.

What I may experiment with, if Duncan confirms that there are potential sonic gains to be had [not least of which is perhaps removing any claimed signal degradation created by using a digital volume interface, and the subsequent loss of bit resolution], is having a passive pot instead, for adjusting sound levels, purely when using the Pi. It need only be a small and simple box.

Personally, I think there's some mileage in that, especially as convenience is a non-issue for me, if the by-product of that is a loss in fidelity, no matter how small.

Marco.

[tubehunter]

I have never liked digital control of volume, 0dB from dac gives the best signal to noise. imo
Not to mention loss of resolution.
Have you noticed that pop when you select a new track? when listening at low levels.


Some pictures of my PiPre

I used an old PS Audio case I had knocking about not pretty but functional.
On the front panel you have Volume, Selector Switch and a Pi Reset button (handy) with Led showing power to the Pi.
Rear has an Analogue in, Pi Usb and Ethernet inputs, Output and Mains switch and fuse.

[struth]

Pretty Tidy Duncan

[mikmas]

What I may experiment with, if Duncan confirms that there are potential sonic gains to be had [not least of which is perhaps removing any claimed signal degradation created by using digital volume interface, and the subsequent loss of bit resolution], is employing the use of a passive pot instead, for adjusting sound levels, purely when using the Pi. It need only be a small and simple box.

Personally, I think there's some mileage in that, especially as convenience is a non-issue for me, if the by-product of that is a loss in fidelity.

Marco.

My personal choice would be a passive pre - a simple 10k Alps (wired as a voltage divider) is what I've used between various DACs and my Quad 303 and this always worked sonically as the best and gives perfect volume control

Having now looked at the data sheet for the Texas Instruments DAC used by Qaudio my previous post was on the right track but possibly for the wrong reasons. Amplification of the analogue signal occurs via hardware internal to the DAC chip and inherent to its operation so doubt there is any way way to pick up that signal other than where's it's output to the RCAs. My inclination would be setting the 'digital' and 'hardware' sliders to 100% and using the passive to tame the 2v output for the power stage. If any clipping does occur then start by reducing the 'hardware' amplification until you reach the sweet spot.(as I think this has already been said) I have an aversion to any and all software volume controls as I've found they inevitably change the sound adversely.

[Marco]

The Pi-pre is looking good!

I have never liked digital control of volume, 0dB from dac gives the best signal to noise. imo
Not to mention loss of resolution.
Have you noticed that pop when you select a new track? when listening at low levels.

Yes, that was happening when you were here, too. It doesn't overly bother me, as it's very low-level, but would be better if it was gone.

I don't think we were hearing too much 'loss of resolution' (using Volumio and the Pi direct into a power amp) when, along with Ian at my place, we were sitting there wetting our pants at how good it sounded (either with your modded Quad 405s or the Copper amp in the equation)!!



But yes, I take your point. So how about building me a little passive volume pot, to use solely with the Pi, which I can simply connect up when I want to use it?

Marco.

[Marco]

My personal choice would be a passive pre - a simple 10k Alps (wired as a voltage divider) is what I've used between various DACs and my Quad 303 and this always worked sonically as the best and gives perfect volume control

Yeah, but I wouldn't want anything too complicated or expensive, as it won't be replacing my Croft. Essentially, all I need is something simple that replaces the role of Volumio, in terms of adjusting sound levels from the Pi, and achieves that with maximum resolution and minimal influence on the music signal.

Marco.

[mikmas]

Yeah, but I wouldn't want anything too complicated or expensive,Marco.

I can't do either complicated or expensive - I have neither the brains nor the wallet

I have two passive pres costing about £20 each to build (including case) and both are just wire, connectors and a pot and about 30 minutes to put them together The circuit couldn't be less complicated

(EDIT: just noticed that I use the same basic circuit Duncan used in the pic above)

[Ali Tait]

"

My personal choice would be a passive pre - a simple 10k Alps (wired as a voltage divider) is what I've used between various DACs and my Quad 303 and this always worked sonically as the best and gives perfect volume control

Having now looked at the data sheet for the Texas Instruments DAC used by Qaudio my previous post was on the right track but possibly for the wrong reasons. Amplification of the analogue signal occurs via hardware internal to the DAC chip and inherent to its operation so doubt there is any way way to pick up that signal other than where's it's output to the RCAs. My inclination would be setting the 'digital' and 'hardware' sliders to 100% and using the passive to tame the 2v output for the power stage. If any clipping does occur then start by reducing the 'hardware' amplification until you reach the sweet spot.(as I think this has already been said) I have an aversion to any and all software volume controls as I've found they inevitably change the sound adversely.

Much better pots around than Alps IMHO, for the same or not much more.

[mikmas]

"Much better pots around than Alps IMHO, for the same or not much more.

Cool - any brands in particular?

[Ali Tait]

TOCOS are very good I've found-


http://www.hificollective.co.uk/cata...er-p-9217.html