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

[mikmas]

TOCOS are very good I've found-


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

Thanks for the tip - bit pricier than the Alps but might give one a whirl when they have the 10k back in stock ....

[Ali Tait]

Not sure they will, think they are being phased out. 20k would be fine I'd have thought.

[rectorydp]

Hi David,



Since you're obviously knowledgeable in these matters and reasonably local (I'm in Wrexham), if you were willing, at your convenience, to pop round here and have a look at things for me (as well as have a music sesh), I'd be more than willing to pay your fuel costs and provide a hot meal and drinks!

I don't even mind coming to collect you, or meeting you halfway at a train station if that suits better

Marco.

I think it might be worth experimenting with the analogue volume to lower the output to 1v rms max. If you do that then you would be able to reduce the digital attenuation. According to the IQaudIO documentation, the analogue volume is the Playback volume control. It is mentioned on page 20 (http://www.iqaudio.com/downloads/IQaudIO.pdf). The main volume control should be at ~86% for 0dB i.e. no digital domain attenuation. If you use a passive pre then that is where you would want to set the digital volume control as indicated by Duncan (you would probably set the analogue volume at max in that situation). I note that Duncan says that he sets the volume at maximum before disabling. If you didn't do that then it could be why your attempt encountered the problems that it did.

It would be interesting to try a passive pre to see whether it was better or worse. However, I don't really think that digital attenuation should be a big issue here. If the TI chip is using the full 32 bits when controlling the volume then it really won't have an impact on the signal at listening volumes because it has so many bits spare.

Thanks for the invitation to Marco Towers. TBH I think you will probably have sorted this out by the time I would be able to pop up to see you. There are certainly lots of suggestions from the forum!

[lovejoy]

Well, it's in, it's built and it's up and running. I also got to meet Gordon at IQ Audio earlier too and what an absolute gent and incredibly enthusiastic bloke he is.

I don't want to say much at the moment as I like to have at least a few days to listen to form a proper conclusion and not let the initial expectation bias/enthusiasm cloud my judgement, but let's just say that new cartridge may well have just got a step closer ;-).

[Marco]

Hi David,

I think it might be worth experimenting with the analogue volume to lower the output to 1v rms max. If you do that then you would be able to reduce the digital attenuation.

If that's considered a good idea, it would definitely be one for Duncan to implement, as I wouldn't know how.

According to the IQaudIO documentation, the analogue volume is the Playback volume control. It is mentioned on page 20 (http://www.iqaudio.com/downloads/IQaudIO.pdf). The main volume control should be at ~86% for 0dB i.e. no digital domain attenuation. If you use a passive pre then that is where you would want to set the digital volume control as indicated by Duncan (you would probably set the analogue volume at max in that situation).

Yup, I get that, thanks. However, the idea now may be to go with a 'Pi pre', such as Duncan showed a picture of earlier, as I think that would produce the best results.

I note that Duncan says that he sets the volume at maximum before disabling. If you didn't do that then it could be why your attempt encountered the problems that it did.

Yes, having spoken with a friend earlier about this, who also has a Pi and an active valve preamp, I think you're probably right, so will give that another go.

It would be interesting to try a passive pre to see whether it was better or worse. However, I don't really think that digital attenuation should be a big issue here. If the TI chip is using the full 32 bits when controlling the volume then it really won't have an impact on the signal at listening volumes because it has so many bits spare.

Yup, that's certainly what's happening here, as I can detect no sonic degradation whatsoever, as a result of using the Volumio digital interface to control sound levels.

In that respect, I could simply leave things as they are. However, being a perfectionist and someone who will always try to eke out the final few percent of performance from my kit, I'll be investigating some other options, as outlined, just to see if those are any better!

Thanks for the invitation to Marco Towers. TBH I think you will probably have sorted this out by the time I would be able to pop up to see you. There are certainly lots of suggestions from the forum!

Indeed. However, you'd be welcome here anytime. We also go down to Shrewsbury at least once a month to do some shopping and buy wine in Tanners, so perhaps we could hook up next time I'm in your area?

Marco.

[Marco]

Well, it's in, it's built and it's up and running. I also got to meet Gordon at IQ Audio earlier too and what an absolute gent and incredibly enthusiastic bloke he is.

Excellent news, mate. You should ask Gordon to join AoS, as i think he's currently posting on pfm. I'm sure he'd be delighted that his products are receiving such high praise here, too.

I don't want to say much at the moment as I like to have at least a few days to listen to form a proper conclusion and not let the initial expectation bias/enthusiasm cloud my judgement, but let's just say that new cartridge may well have just got a step closer ;-).

Cool, although I'm not sure I understand what you mean about the cartridge....

Marco.

[lovejoy]

Cool, although I'm not sure I understand what you mean about the cartridge....

Marco.

Sorry, that might have been a bit vague - What I meant was that I'm enjoying the new DAC so much that the Naim DAC could be in serious danger of being sold on, which means I'll have the funds for a cartridge upgrade ;-).

Got up early for a bit more listening this morning, that's how addictive this is. A few observations to start:
Here's how things are set up:
Pi 2 running Volumio with MinimServer on my NAS being controlled with BubbleUpnp from my phone/tablet - this is working REALLY well.
Currently I have the mixer in Volumio disabled so I'm going straight into my Dynavector L300 pre at 100% volume - Well, actually I've turned it down to 90 as I was getting some distortion at 100% so I'll have another look at that later. One thing I noticed, and I guess this is the same trouble you've had Marco - is that when you disable the mixer, that seems to lock the volume at whatever it was set to last. The fresh Volumio install set the voume somewhere around 54% which is probably wise to avoid anyone blowing their speakers if they're going straight into a power amp, but I expected that disabling the mixer would have locked it to 100% volume without having to do anything else, but it looks as if you have to manually set the volume to the level you want it to be locked at first.

What am I getting from it sonically?
The first thing that hits me is instrument tone and separation. You can ALWAYS follow any instrument in the mix no matter how busy it is and instrument timbre is just amazing. Listening to 'Easy pickings' by This is the Kit, the song starts off with a banjo, then the vocals arrive. What I always found with the Naim was that when the vocals came in, the banjo receded and sounded as if it was just being strummed and the notes became flat, as if the frets were just being muted, but now the banjo remains solidly in the mix and can be followed and the notes, the tones of the picking and the strings is all there.
It cuts through the BS and just gets you to the music, which can be both a good and a bad thing depending on the recording. Where as my Naim tends to sugar coat and polish everything, where everything is 'nice', an enjoyable listen. The iqaudio just seems to hand you whatever is in the stream - so bad recordings will still be bad, but good recordings will shine in a way the Naim won't reveal. That said, even with the bad recordings, this DAC seems to be pulling everything out, so you find that you're never really getting distracted or focusing on the bad bits, but because the whole picture is being presented to you, there's always something interesting going on. Time will tell whether I start to shy away from the poorly recorded stuff. I have a feeling I won't because this isn't what I would call a 'warts and all' presentation, merely a clean window into the recording - What I have a feeling I may start doing more of is hunting down the better masterings of a lot of recordings I have.

[Rothchild]

Interesting blog post here: https://hifiduino.wordpress.com/2014...-pi-version-b/

+ a few more clues about how the gain structure of some of these dacs is put together.

[lovejoy]

Reading the manual and the previous threads pays! 86% for 0dB output! Now I'm cooking on gas!

[r100]

I've been sifting through some of Gordon's posts (he is the iqaudio designer) over at www.volumio.org .. maybe the below quote is an additional clue .. in any event, this board is getting a lot of praise ref. SQ

The IQaudio Pi-DAC+ and older Pi-DAC use the PCM5122 dac which has built in hw volume control.
usage of this feature requires i2c commands to be sent to the dac to adjust the volume.
This can be done using direct i2c commands or via ALSA function calls. Also code for the IQaudio DAC for Rotary encoder is available on www.github.com/iqaudio/tools

Very best regards,
Gordon