Meridian Unplugged - Powered by MrTechGuy.co.uk

Sorry Ronnie - must have missed it.

Initial thoughts are that they are different. Tough question is whether either is better. I'll do some A/B listening to see if I can articulate what the differences are.

Evdberg...many thanks for that. If only I understood what it meant

VK, How is that Tinkering with Sox and Transporter going.

You might find this post useful.

http://forums.slimdevices.com/showpost.php?p=573376&postcount=13

By the way, it does work. G68 is showing 88K for a 44K track playing on Transporter. And it's doing this on an old pokey laptop for a server and no skips or anything.

I don't really expect to hear any improvement since I can't hear a reduce in quality from a real 24/96 to 16/44.

Wish I could instantly tweak it.

I think you can run Sox with dBpoweramp (via custom command line DSP) and then I could make two flacs (or more) and flip through them.

I don't know what he did as far as pre-echo switches and he may be using a choice that is light on CPU load.

Hi George,

Good spot. I trawled the forum for ages but couldn't find a clear set of code
that did 88.2 and figured the volume piece out. This bit I don't really understand and am not sure what it means to drop volume by 10%. Why would the processing push towards clipping at 100%?

Given your 'expertise' in this area I wonder if you had any thoughts?

I'll give this a go at the weekend.

cheers

Can't understand why that guy has turned off dithering though...

Not spent any more time investigating this yet, but I did finish painting my theatre room ceiling yesterday evening

What colour?

Black!

FWIW - I've just put the custom-config file into my squeeze-server and the G68 is showing 88k as expected.

No time yet to listen properly but first impression is "lovely"....but then the 8k's do that every time. Will try and switch it on/off over the weekend and see if I can hear any differences.

Anyone else tried it yet ?

I've not tried the code above but I have tried various minimum phase filters implemented using Sox. I have to confess that I don't hear much (if any) difference. I haven't done extended listening tests however.

Cliff

PS: Have any of you Transporter owners compared the fast and slow roll off filters for its AK4396 DAC which are now software-switchable in the latest Transporter firmware release? Haven't had a play myself yet but I might have a listen over the weekend

Cliff

In the server settings: advanced/file types
FLAC-FLAC lists as FLAC/sox. I don't recall it listing as this before. Does slim change if you have the custom config installed ?

Task manager shows FLAC.exe, squ.exe and sox.exe running.

Just curious.....

Ok, I'm taking a look at this whilst lying in bed with a stinking head cold...

Here's my take on "soundcheck's" options:

[sox] -v0.9 -D -q -t WAV - -t FLAC -C0 -b24 - rate -v -s -M -a 88200

-v 0.9 : I don't like this volume factor. SoX FAQ #5 states that both resampling and dither require headroom, but I don't see why this should be necessary when going from 16 to 24-bits.

-D : Disable automatic dithering. Seems to me to be a *very* bad idea given this is a non-trivial DSP operation with a change in word size.

-q : Run in quiet mode.

-t WAV - -t FLAC : Input file is WAV (decoded from FLAC); output file is FLAC.

-C0 : Zero compression of the FLAC.

-b24 : Output 24 bits.

rate : Resampling

-v : Very high quality.

-s : Steep filter.

-M : Minimum phase.

-a : Allow aliasing above the pass-band.

88200 : Output sample rate

From this graph I'd be tempted to stick with -vMa (zero pre-echo with the fasted post-echo decay) and skip the -s (steep filter) option. I'm not sure what this will do to the impulse response.

More ramblings later. I'm going to try the following on the command-line with some of my files and see if I get any clipping messages:

sox -t WAV - -t FLAC -C0 -b24 - rate -vMa 88200

Two more things:

1) If we're happy to use SoX for re-sampling, then I guess we might as well make use of it's ability to apply replay gain.

2) Does anyone know where the 96k to 48k and 88.2k to 44.1k downsampling for non-96k Squeezeboxes is specified? Is it hardcoded into the Squeezeboxserver application?