Sound Quality w/ Latest Firmware

[jhwilliams]

I have been trying out the new SlimServer 6.2 beta. I noticed that the sound wasn't as sharp when I used 6.2 against 6.1 - I did a blind test with my girlfriend and she picked the difference every single time.

After a bit of experimentation it turns out the actual factor was the firmware - if I use the same firmware from 6.1 the sound is noticably better.

Additionally, I seem to be having the opposite issue to many on here - with the newer firmware the SB2 isn't loud enough to drive my amp. Even with the preamp setting at zero it is quieter than the 6.1 firmware.

I've tried all the various player audio settings (different gain settings, etc). But the result is consistently the same - flatter sound at lower volumes.

Anyone got any advice? Is there a set of settings which I should be trying out?

ps. My setup is SB2 wireless, direct to amp. Test files all FLAC ripped w/ EAC.

I think the actual firmware versions involved was 15 for 6.1 and 40 for 6.2 (?).

[seanadams]

Originally Posted by jhwilliams

I've tried all the various player audio settings (different gain settings, etc). But the result is consistently the same - flatter sound at lower volumes.

The volume curve has changed.

[jhwilliams]

Originally Posted by seanadams

The volume curve has changed.

Is that to make it more linear?

I still find that with preamp at zero, max volume isn't as loud as it used to be (I realise this is the opposite issue to everyone else in here).

Any ideas/suggestions regarding the flatness of the sound? I have tried a bunch of different setting combinations - or perhaps another question - what settings will give audio behaviour similar/same as the old firmware?

[seanadams]

Originally Posted by jhwilliams

Is that to make it more linear?

I still find that with preamp at zero, max volume isn't as loud as it used to be (I realise this is the opposite issue to everyone else in here).

Perhaps replaygain is in effect?

Any ideas/suggestions regarding the flatness of the sound?

Can you be more specific?

[jhwilliams]

Originally Posted by seanadams

Perhaps replaygain is in effect?

I've disabled replaygain - i haven't bothered to run any tests (my equipment is packed), but i'd guess i can't get around half the range.

Originally Posted by seanadams

Can you be more specific?

Unfortunately I can only be subjective - the sound with the new version seems to roll off. I'm not that great with audiophile terminology, but i find the soundstage with v15 seems much better - especially with classical music.

I have a cd of african music where it is quite apparent - with v15 you feel like they are in the room, with the latest version that positioning is lost/collapsed.

I've got an outboard DAC (not here yet), so it's not a massive issue - just wondering if there are particular configurations that I should be trying.

[seanadams]

Originally Posted by jhwilliams

Unfortunately I can only be subjective - the sound with the new version seems to roll off. I'm not that great with audiophile terminology, but i find the soundstage with v15 seems much better - especially with classical music.

We'd have to identify something specific, otherwise it isn't anything I can look into. The most helpful thing by far would be if you could capture a recording from the digital outputs using a good s/pdif sound card, just so we can make sure the data is getting through the same as before. I can't think of anything that would be molesting the data here, and as far as we know everything is still correct in digital land.

WRT to the DAC, the only thing I can think of that has changed would be that we have corrected the polarity (aka phase) of the analog outputs. They were inverted before. If you can hear a difference, that's damn impressive as there is a long standing debate as to whether absolute phase is audible.

[Patrick Dixon]

Can you give us some more info on your setup? You say SB2 direct to amp, but you then talk about a preamp volume setting. What actual volume numbers are you using in each case?

I've found that with an SB2 directly into an amp, whereas I used to listen at around 20-25 on the SB2 volume setting, I'm now listening at 30-35. The 'new' settings give much more control at lower volumes (which I never use!), at the expense of larger steps at high volumes; but since they better match the response of the human ear, overall it's a much better approach.

IIRC, the volume control steps are now about 1.5db, so 35 is probably 'about' the same level as 20 on the 'old' linear system. When doing A/B tests, it quite important to properly match levels or you will find that the slightly louder one is often prefered (even if they are the same otherwise). Some audio systems don't seem to 'come alive' until you reach a certain volume level, so it's just possible that this is what's happening for you.

[jhwilliams]

Originally Posted by seanadams

We'd have to identify something specific, otherwise it isn't anything I can look into. The most helpful thing by far would be if you could capture a recording from the digital outputs using a good s/pdif sound card, just so we can make sure the data is getting through the same as before. I can't think of anything that would be molesting the data here, and as far as we know everything is still correct in digital land.

I will do - I don't have all my equipment yet, but when I do I'll give it a shot. I also have an outboard dac coming which will help isolate.

Originally Posted by seanadams

WRT to the DAC, the only thing I can think of that has changed would be that we have corrected the polarity (aka phase) of the analog outputs. They were inverted before. If you can hear a difference, that's damn impressive as there is a long standing debate as to whether absolute phase is audible.

Interesting! I don't know much about it, but I would have assumed the same re: phase.

That said, it's interesting you mention that and that the CD I find most noticable is of african music (lots of voice, timbre, etc). On the back of that I tried changing the speaker orientation a little and found it helped a lot. Not sure what this all means - I haven't had time to investigate further yet (or try another proper blind test).

Additionally, I have a tube amp, which may be inverting phase itself. So a few things to try... My wiring is a bit of a pain and doesn't lend itself easily to switching back and forth - I might see if I can produce an inverted WAV. Thanks for the tip.

[jhwilliams]

Originally Posted by Patrick Dixon

Can you give us some more info on your setup? You say SB2 direct to amp, but you then talk about a preamp volume setting. What actual volume numbers are you using in each case?

I've found that with an SB2 directly into an amp, whereas I used to listen at around 20-25 on the SB2 volume setting, I'm now listening at 30-35. The 'new' settings give much more control at lower volumes (which I never use!), at the expense of larger steps at high volumes; but since they better match the response of the human ear, overall it's a much better approach.

IIRC, the volume control steps are now about 1.5db, so 35 is probably 'about' the same level as 20 on the 'old' linear system. When doing A/B tests, it quite important to properly match levels or you will find that the slightly louder one is often prefered (even if they are the same otherwise). Some audio systems don't seem to 'come alive' until you reach a certain volume level, so it's just possible that this is what's happening for you.

I've got a McIntosh tube amp - fed directly from the SB2. The amp feeds my speakers directly, so a pretty simple setup for now.

With the old firmware I was running pretty similar values to you - low 20's before and low 30's now.

The preamp setting I referred to is the new preamp value in the player settings (for the latest firmware). I've left this at zero and also turned off the gain correction.

You might be right regarding the volume. Generally in my tests I've tried to get the volume consistent between the two by ear, so you're right that it might be missing a few db without knowing (I have a meter, but it's not handy unfortunately). I might need to adjust the calibration on the amp unbalanced inputs as well.

I'll give the above a shot and let you know - thanks.

[Patrick Dixon]

I've been listening to my modified SB2 very carefully over the last few days, and it has been troubling me that it didn't sound as good as I remembered.

It seemed to me that there was something wrong at the HF end which was making it sound a little harsh and fatiguing - a characteristic that I was sure was not there before.

So I ran some frequency sweeps through it (mainly to check that the response was flat), and I noticed a certain amplitude grantularity. This got me thinking that the new volume curve might be responsible (I've been using the SB2 direct to an amp with the SB2 volume control), and so I've been running some numbers through excel.

I'm not sure exactly how the 'linear' volume control was implemented, but assuming a 2.5% reduction in amplitude per step, volumes of 40, 35, 30, 25, 20, 15 etc would still produce 'lossless' results with 16 bit (CD-derived) sources. If SD implemented the intermediate volumes using 1/256 rounded coefficients, all the remaining volumes would have been lossless too.

However the new 'log' volume control uses 1.27dB reductions per step, which gives NO lossless volume settings - except for 40 (assuming 16 bit audio data).

So is this what I and jhwilliams + girlfriend are hearing? Well I've reverted to a pre-log-volume-control nightly, and I am convinced it sounds better.

So Sean, I have a suggestion. The log volume control is clearly a better approach overall, but could you implement a version that uses 1/256 rounded multipliers for (say) volumes 20-40, and non-rounded multipliers below? No critical listening can really take place at -25dB+ with 'normal' amp gains /speaker efficiency, so the levels below 20 (which can't be smoothly rounded in 1/256ths) don't really matter.

In the interests of bit-perfect audio and all that ....