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

[NRG]

Great you have got that sorted out Marco.

I've gone as far as I wanted with mine at the moment, will now wait for the IQ boards to come into stock. Now I've had more time to compare against my SB the differences are seemingly greater, the SB is more engaging over time...hard to describe exactly but it just comes across being more natural and refined. I hope the IQ DAC reverses that!

[Marco]

I'm confident it will. Does your SB use a linear PSU?

Marco.

[Marco]

Just one thing, Mark...

Playback and Playback boost are the ones that should be adjusted to suit (according to the input sensitivity of your pre) this will be an ears and brains activity. I'd suggest setting the pre to a sensible level and then winding up the 'playback' control, if you get all the way to the top and your system is still quiet (compared to what you'd expect for the pre volume setting) then proceed to winding up the playback boost control too (there's another couple of milivolts of gain on this slider)...

I've found that adjusting both the playback and playback boost levels, using the up and down arrows on my keyboard, doesn't allow for any incremental adjustment: it's either all or nothing... The only incremental adjustment available, via using the up and down arrows on the keyboard, is with the PCM (master volume) setting.

Is that normal?

Marco.

[Marco]

Anyone? Rob?

Btw, after further experimentation I've now adjusted things on Alsamixer so that only Playback has been set to max. Playback boost has been set to zero, as otherwise I was getting a little distortion.

One other little tweak (within the Volumio web interface, under System Settings) is to disable everything listed under the 'Services Management' section (Airplay, UPNP Control, UPNP/DNLA Indexing and DNLA Library Server), as that reduces the amount of processing taking place and improves sound quality.

Marco.

[Rothchild]

Anyone? Rob?

Btw, after further experimentation I've now adjusted things on Alsamixer so that only Playback has been set to max. Playback boost has been set to zero, as otherwise I was getting a little distortion.

Marco.

As I'd suggested might be the case. Glad to hear you've got on top of the settings. I note you're running the PCM volume at 96 rather than 86 (which would be the the 'un-tampered with' setting), in theory at least if you ratcheted down the pcm to 86 you would be getting 'bit perfect' translation and the 0.8dBv of gain available from the playback boost would allow you to make up the difference in the analogue domain. It's not clear from the guidance that Gordon gave if the system goes up to +2dBv on Playback with an additional 0.8dB of gain on playback boost or if turning both up gives you the +2dBv of gain.

[Marco]

Hi Marc,

As I'd suggested might be the case. Glad to hear you've got on top of the settings. I note you're running the PCM volume at 96 rather than 86 (which would be the the 'un-tampered with' setting), in theory at least if you ratcheted down the pcm to 86 you would be getting 'bit perfect' translation and the 0.8dBv of gain available from the playback boost would allow you to make up the difference in the analogue domain.

Yes, I've tried it that way, but it doesn't seem to be as good as leaving the playback boost off and using a higher PCM setting.

To obtain the same output from the Pi/IQ-Audio DAC, as I get from my CDP [i.e level-matched], the PCM setting needs to be 96. Any less than that, even with the playback boost on, results in a softer and less 'punchy' and wide open sound, not to mention significantly less output than my CDP provides, at the same volume setting on my preamp.

You didn't answer my point about not being able to adjust playback or playback boost in increments. With both here (in Alsamixer), it's either 'all or nothing'. Is that how it's supposed to be?

It's not clear from the guidance that Gordon gave if the system goes up to +2dBv on Playback with an additional 0.8dB of gain on playback boost or if turning both up gives you the +2dBv of gain.

Indeed. I'll ask Gordon about that one.

Marco.

[Rothchild]

Well, if it sounds good, it is good.

It's a known phenomena that louder sounds better (even by tiny increments) so you're right to aim at level matching, but I'm interested to know if what you're hearing is the sweetspot of the pre input, or if level matching by turning up the pre output (to get you back to the right volume) makes up the difference. Presumably with a quality pre the gain there should be better than the gain in the pi.

Question not answered cos I don't know, sorry! Sounds odd through, could just be a matter of using the right key to control it?

[Marco]

...but I'm interested to know if what you're hearing is the sweetspot of the pre input, or if level matching by turning up the pre output (to get you back to the right volume) makes up the difference.

I've read that about four or five times now, but I don't really get what you mean?

Question not answered cos I don't know, sorry! Sounds odd through, could just be a matter of using the right key to control it?

Perhaps, although it's the up and down arrows on the keyboard for adjusting the PCM level, so it seems odd that Playback and Playback boost would be controlled differently... Also, a friend trying it yesterday (with a Pi/IQ-Audio DAC) reported the same thing.

Marco.

[Rothchild]

I've read that about four or five times now, but I don't really get what you mean?

Marco.

I'm presuming that your pre has a volume knob on the front of it? If so, what I'm saying is that rather than level matching the cdp with the volume knob at the same place, take the lower input from the pi and make up for it by turning the volume knob on the pre up until the levels in the room are the same as with the cdp.

Obviously the output level of the Pi is driving the input level of the pre, there will be an optimum value for this - too low and the pre has to do too much work, too high and the pre inputs will start to distort. Given that an amount of this is about satisfying an audiophile tendency, I'm thinking that having the pi set up to do no digital gain changing but pushing the analogue output level and then making up the difference with the expensive gain in your pre-amp would be preferable than 'messing with your bits' (via the PCM control).

Unfortunately this will make comparing a little harder as it will be difficult to match the sound level in the room and most research seems to show that even with tiny differences in volume listeners will prefer the louder source.

[ReggieB]

I've found that adjusting both the playback and playback boost levels, using the up and down arrows on my keyboard, doesn't allow for any incremental adjustment: it's either all or nothing... The only incremental adjustment available, via using the up and down arrows on the keyboard, is with the PCM (master volume) setting.

Is that normal?

Yes. I get the same.

The alsamixer settings are a tweakfest. You're not going to break anything, so have a play and use what best suits your ears.