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Music that sounds better in lo-fi

Started by Sony Walkman Prophecies, December 07, 2018, 05:27:08 PM

Previous topic - Next topic
Quote from: buzby on December 12, 2018, 10:24:58 PM
Pre-emphasis on CDs is quite rare, and was only really a thing in the very early days before 16-bit DAC chips became commonly available. Early CD players used 14-bit DACs and a 22khz low-pass filter to cut off the resulting conversion noise at higher frequencies.

Just to go off on this tangent, the Aiwa CD player I had in the 90s marketed itself as having a "1-bit DAC". Assuming this is an accurate description (and rendered the audio in a way close to pulse width modulation, and/or used an even more aggressive filter), that's pretty terrible isn't it.  I never saw CD players with 16- or even 14-bit DACs, so I'm guessing this must've been top-end kit that was well out of my price range.

As something of an audiophile, I always noticed that my CDs didn't really sound as good as I'd expected them to, so perhaps this is why.

Sebastian Cobb

Quote from: the on December 13, 2018, 09:40:23 AM
I don't care
I don't care
I don't care if he comes round here
I've got my bass in the sidechain here
let plugins sort it out if it thumps too near

10/10

buzby

#32
Quote from: Darles Chickens on December 13, 2018, 10:35:22 AM
Just to go off on this tangent, the Aiwa CD player I had in the 90s marketed itself as having a "1-bit DAC". Assuming this is an accurate description (and rendered the audio in a way close to pulse width modulation, and/or used an even more aggressive filter), that's pretty terrible isn't it.  I never saw CD players with 16- or even 14-bit DACs, so I'm guessing this must've been top-end kit that was well out of my price range.

As something of an audiophile, I always noticed that my CDs didn't really sound as good as I'd expected them to, so perhaps this is why.
1 bit DACs are something completely different - they are based on the Delta-Sigma modulation conversion principle and treat the bitstream coming off the CD as serial data, and clock the converter (i.e. oversample) at a multiple of 16 bits to produce the output waveforms - for 1-bit DACs 256x oversampling was usually the norm. This produces a more linear output and removes the problems of zero-crossing that you get with a 16-bit DAC, but 256x oversampling at 1 bit wide is really only adequate to reconstruct an 8-bit signal, so they are more susceptible to producing conversion noise. As they derive the closck for oversampling from the CD clock signal, they are also more prone to jitter than a multi-bit DAC. To get round this, they used digital filtering and noise shaping algorithms.

The 1 bit DAC for CD players was originally designed by Philips ((which they called BitStream) to replace the 14-bit DACs they started out with (Sony had insisted on 16-bits being the standard, as they had the capability to make 16-bit DACs). Matshushita (Technics/Panasonic) also developed their own variant of the 1-bit DAC, but only used 32 or 64x oversampling and a digital noise shaper (developed by NTT, Japan's equivalent to BT) to reconstruct 4-bit nibbles at a time which were then fed into a PWM-based 4-bit DAC to get the analogue waveform. This system was called MASH.

Virtually every CD player made since then has used a Delta-Sigma based oversampling 1-bit DAC (other than some really high-end ones, which still use the Burr-Brown PCM1704 16-bit DAC chip that dates back to the 80s), and the SACD standard was based on it (the bitstream on the disc is the direct Delta-Sigma encoded signal).

There is a good (if rather technical) description of the Delta-Sigma conversion process and the effect of increasing the oversampling rate on noise performance here.

Thanks buzby!  Knew I could rely on you for more information on this than I could have possibly anticipated!  Thuzby.

What I find interesting about this is that, although digital audio was always sold as being not prone to signal degradation etc, it seems like there were a number of different ways of actually interpreting the digital data as analogue audio, each with their own merits and weaknesses.  So, not all CD players were equal.  As a kid, I didn't realise this and assumed that differences in output would be due entirely to the quality of the amplifier and speakers (which also will have had a part to play of course).

mojo filters

Quick question with reference to the post about early 14bit CD players (have to admit I'd not heard of such, I assumed 16bit was standard from the start - in line with Sony/Phillips Red Book).

If the high pass filter was still at 22kHz, wouldn't that be exactly the same Nyquist frequency as all 44.1kHz devices? In other words, the bit rate doesn't appear to impact the sampling rate - unless I'm missing something...

Also with reference to modern CD players having 1bit DACs utilising DSD oversampling, my relatively modern Arcam 72T made no mention of this I can recall.

It's been a while, but I remember because one advantage was I could have Arcam upgrade the DAC to better Burr Brown or Wolfson DACs from more upmarket models in that range - though I've never really found any need, as it sounds fine.

Sebastian Cobb

What makes me chuckle is how hifi mags have high end transport decks and review them as if they make a difference; you could use a £10 cd rom drive and connect it to the dac portion and it'd make no difference.

When I had a minidisc player and no cd's with optical out I used a cd rom drive with a led connected to the digital out and pushed into a few mm of biro which I'd then push onto the toslink cable, worked fine.


mojo filters

Surely build quality plays some factor in respect of transport decks, even if it's just in respect of longevity?

My first relatively modest Sony CD player lasted about 15 years of solid duty. Then I picked up a used NAD which worked fine, but I traded it in for my Arcam which a friend working in Richer Sounds tipped me off to - as it had been returned due to a cosmetic blemish, which the factory fixed but the customer wanted a new one, so it was on sale at a very attractive price (this was before Richer Sounds sold much upmarket hifi or home cinema stuff).

By contrast I got through 3 budget (but decent) Toshiba DVD players in about a decade. Then I bought a nice Pioneer that plays DVD-A and Sony DSD too, which is still going fine after many years (to be fair the only hi res audio action it's ever seen is Pet Sounds and that orchestral Joni Mitchell album).

Endicott

Quote from: mojo filters on December 13, 2018, 04:25:30 PM
Also with reference to modern CD players having 1bit DACs utilising DSD oversampling, my relatively modern Arcam 72T made no mention of this I can recall.

https://www.arcam.co.uk/products,diva-cd72-t-cd-player.htm

QuoteThe latest generation 24 bit DAC from Burr Brown
QuoteThe new CD72 uses a 24 bit Burr Brown multi level delta sigma DAC

So it mentions Burr Brown and delta sigma - basically I am now confused. Sounds like a nice player anyway.

mojo filters

Quote from: Endicott on December 13, 2018, 05:42:01 PM
https://www.arcam.co.uk/products,diva-cd72-t-cd-player.htm

So it mentions Burr Brown and delta sigma - basically I am now confused. Sounds like a nice player anyway.

Thanks, that makes sense. Guess I remembered it wrong!

Yeah, it's a nice player built pretty solid, especially considering how little I paid. Certainly not tempted to upgrade the DAC. Not really much of a hifi snob, like with most things in sound - it's the environment, input source and output device that makes the most difference.

The only upmarket thing I own are PMC monitors as I'm a big fan of the transmission line loading technique, which is like an inverted tapped horn subwoofer. The group delay is more akin to a sealed box design, but with greater low frequency extension considering the size of the cabinet.

If I was going to invest any more significant money in hifi / monitoring, I'd be looking at further room treatment - an area often underestimated by upmarket hifi users!

buzby

Quote from: mojo filters on December 13, 2018, 04:25:30 PM
Quick question with reference to the post about early 14bit CD players (have to admit I'd not heard of such, I assumed 16bit was standard from the start - in line with Sony/Phillips Red Book).
Philips' original standard for CD was going to be 14-bit, and they had designed their DAC around this. When Sony came onboard, they successfully lobbied for the standard to be changed to 16-bit, which left Philips in a bit of a quandary, as they had no time to redesign their DAC before the 1982 launch. Instead, to make up for the missing 2 bits of resolution they used 4x oversampling and a noise shaping algorithm to 'dither' the values of the missing 2 bits.

They didn't have a true 16-bit DAC until 1985, and then in 1989 they introduced their Bitstream 1-bit  Delta-Sigma DAC.  This was initially intended for the low end of the market as they were a lot cheaper to produce than a precision resistor-ladder 16-bit DAC, but eventually the advantages of the design led to it's widespread adoption by other manufacturers.

There is a good article on the history of Philips' DAC developments here.

Quote from: mojo filters on December 13, 2018, 05:37:03 PM
Surely build quality plays some factor in respect of transport decks, even if it's just in respect of longevity?
Yes, it does, particularly the precision of the speed control and the optical tracking system on the read head, as these contribute to jitter and you want the lowest jitter possible (especially with 1-bit DACs as the oversampling rate is referenced to a clock signal that has to match the bit read rate from the disc as closely as possible). Obviously the older transports that had a lot of metal and precision bearings in them were a lot more robust too, but were so expensive they they soon were replaced by plastic components.

Quote from: Endicott on December 13, 2018, 05:42:01 PM
https://www.arcam.co.uk/products,diva-cd72-t-cd-player.htm
Quote
    The latest generation 24 bit DAC from Burr Brown
    The new CD72 uses a 24 bit Burr Brown multi level delta sigma DAC
So it mentions Burr Brown and delta sigma - basically I am now confused. Sounds like a nice player anyway.
Burr-Brown make both precision resistor-ladder DACs for the ultra-high end market, and Delta-Sigma 1-bit DACs for (slightly) cheaper models. The 24-bit resolution is a function of the oversampling rate, noise shaping algorithm and digital filtering that is used with the 1-bit DAC.