Caiman Mods

[leo]

Hiface is a 24/192k USB to spdif converter price around £100
link to Leo's thread
http://www.theartofsound.net/forum/s...ead.php?t=4880

For a cheap and easy way of getting Hi Rez from the pc its a great little device and a good performer for the price, no idea if it betters whatever your currently using as a transport though for 44.1k

[StanleyB]

Is an upsampling converter really that much better than the REDBOOK spec 44.1KHz?

[Covenant]

Im trying out this
http://cgi.ebay.com.au/ws/eBayISAPI....=STRK:MEWNX:IT

and the same for OP627, not sure what to expect, I`ll let people know.

Don't see why people like the 4562, I really don't like it much at all, the mids are pretty great, but the bass sounds pretty bad and the highs sound too sharp..imo.
Had AD826NZ or something in before and they were pretty good

I think a few people will be interested in your thoughts on these op-amps.
Have you done the MCL5/6 mod and as a result fitted an additional capacitor?

[Themis]

Is an upsampling converter really that much better than the REDBOOK spec 44.1KHz?

Well, it depends. In this particular case, there are two distinct things:
- The conversion to S/PDIF (good thing for average/long cable runs)
- The upsampling

The upsampling in itself (when it's well made) may have some advantages. This is the view of Giuseppe Rampino (from Northstar) :

First of all, let's say the upsampling method CAN'T improve anything. The sound of a digitally upsampled DAC is better because it is the non-upsampled one to be worse.
For, let's see what happens to a standard 44.1 kHz digital signal when it is converted directly by a DAC. Before going into analogue, the digital signal crosses a digital filter that oversamples it (normally 8 times, 8x oversampling, as usually called) and a second digital filter with very high slope that cuts off all the garbage above a certain frequency, quite close to the audio band.
Once the signal has been converted into analogue, it crosses another filter, an analogue one, normally of the 2nd or 3rd kind, that introduces phase rotations into the audible spectrum.
Now, how can we consider the effect of a phase rotation in the time domain?
Let's suppose to have a musical instrument that plays its fundamental tone and its harmonics. The first ones normally are reproduced fine...but the higher order ones are delivered to your ears with a phase rotation (with respect to the first ones) and hence with a time delay that can be heard as distorion.

What happens with upsampling? The standard 44.1 kHz digital stream is interpolated and the samples are calculated as the original signal had a 192 kHz sampling rate. BUT!!!! This process adds NOTHING to the original signal!!!! Even at 192 kHz the signal is still extended till 20 kHz!
The difference now is that the signal crosses digital filters centered at 96 kHz and the following analogue filter will be centered far from the upper limit of the audio band (actually, near 96 kHz!!!).
This means the analogue signal coming out of the DAC will be more faithful to the original one in the time domain (less phase rotations, that is).

[StanleyB]

No disrespect to Giuseppe, but I beg to differ on his interpretation of the facts.
His claim that nothing is added to the signal, because it is still only up to 20KHz is incorrect. D to A decoding does not suddenly drop off at 20KHz. It extends well into the MHz range in some cases and needs careful filtering after 20KHz.
The other thing is that upsampling is done in the digital domain, not the analogue one. If people are concerned that signals should be bit perfect, then upsampling is loaded with imperfect bits.

I am not against the use of upsampling, just as I am not against mp3 lossy compression. But for critical listening with bit perfect accuracy and adhering to the Red Book principle, surely upsampling is just another lossy format that adds data, compared to mp3 that removes data.

[Themis]

I agree that the D/A decoding extends over 20kHz, but the recorded signal part of it is up to 22KHz. The rest is noise inherent to the D/A process.

I guess that there's nothing "perfect" about D/A processing anyway: I know that upsampling is controversial (Dan Lavry is against too, if I'm not mistaken - see http://www.lavryengineering.com/docu...ing_Theory.pdf).
In practice, where an upsampling switch is available, the result is slightly more "relaxed" (without this meaning that some details are lost in the process) when upsampling is engaged. I agree that there's nothing bit-perfect in upsampling (I remember also having said that to Keith, one day), but I guess it's simply a way of addressing digital aliasing. I'm not a specialist, of course, but that's my understanding.

Have you tried using an resampling/upsampling chip with one of your dacs ? Perhaps it could be worth it ?

[lovejoy]

Just to add. I'm not using the HiFace as an upsampler - only as a USB -> SPDIF converter for which I think it does an excellent job and far exceeds what the Mac is capable of on its own. The vast majority of music I own is 44.1/16 and is always output at this rate.

Ever since switching to a Mac for music I was always aware that it's digital output never sounded as good to my ears as the optical or coax from my big old PC, but it's size and the amount of fan noise it made won it a place in the system. Now I know that the Mac is perfectly capable of a 'bit-perfect' signal so I assumed that the quality of the SPDIF signal itself from the Mac just wasn't particularly clean.

So when Keith from Purite offered me a loan of a HiFace to try on the Mac I jumped at it. The improvement took seconds to realise and apart from a few A/B comparisons initially, I wouldn't touch the Mac's optical output with a bargepole again. The major differences are in the frequency extremes - bass is incredibly tight, controlled and tuneful and treble is sweet an unfatiguing. By comparison the Mac sounds wooly and monotonic in the bass and cymbal crashes sound like someone dropping glass onto a tiled floor. Maybe that's a bit of an exaggeration but you get the idea ;-).

I would seriously recommend *ANYONE* using a Mac as a digital source to a DAC to try one of these things. You will notice the difference straight away, certainly if you're using a 2007/8 model Mac like I am.

It wasn't until getting the HiFace that I realised what the Caiman is truly capable of - plus my Caiman is still in an unmodded state presently.

[StanleyB]

Have you tried using an resampling/upsampling chip with one of your dacs ? Perhaps it could be worth it ?

I have tried one of the TI chips, and found that the 64X oversampling Wolfson chip as used in the Caiman gives a far superior result that I prefer. The upsamplng process reminded my of the DBX decoding system. If you listen even casually, you can hear the signal 'pumping'. i.e the attack and decay times were noticeably different and softer compared to the non-upsampled original. It isn't so obvious on low sensitivity speakers and valve amps though. They soften up the signals by default anyhow.

[Themis]

I have tried one of the TI chips, and found that the 64X oversampling Wolfson chip as used in the Caiman gives a far superior result that I prefer. The upsamplng process reminded my of the DBX decoding system. If you listen even casually, you can hear the signal 'pumping'. i.e the attack and decay times were noticeably different and softer compared to the non-upsampled original. It isn't so obvious on low sensitivity speakers and valve amps though. They soften up the signals by default anyhow.

Thanks for the info, Stan.

[leo]

I'm not a great fan of 44.1 upsampled , as mentioned when trying the Hiface , with 96k and 192k I didn't like the effect although proper recorded direct 176.4 stuff sounded brilliant

The Hiface wasn't upsampling 44.1 when I tried it, any 96k 192k material was downloaded in those formats, I'd imagine most of those files had aready been upsampled