Topic: digital modifications?

[udovdh]

Hello,

Why is it that on CD players etc clock mods are 'acceptable' but in recording decks we only see analog mods to input stages?
I know that decks are small but if a recording is made using a sub-optimal clock, what good is the ulta-low jitter clock in the CD-player that is going to play the audio?
Any comments?

Udo

[ghellquist]

To be thruthful, all those clock mods really does very little difference. Mostly an expensive marketing thing.
Ask the modders for hard facts about the real difference and most of them does not even know how to properly measure jitter. Go figure if they know what they are doing (they do know how to make you part with your money, but apart from that ... )

It is very easy and cheap to make a crystal oscillator with very low jitter figures. Which is what the recorders generally has. To get better real-world values you need to go to a larger crystal and feed it more energy, maybe even placing it in an oven. This will not fit inside the boxes or eat batteries. And at that, probably not give any real difference.

No, the real issue is that most of the small boxes has analog circuits that are quite noisy. They all advertize 24 bits but when you do real measurements on them you find that a lot of the bits are only noise. It is not uncommon for the small boxes to have 8 bits of noise, in effect giving you a 16 bit recorder. Now, remember, 16 bits is plenty good. It is a waste of disk space to record those 8 noisy bits, but well, your choice.

Even the very best recorders has about 4 bits of noise, one example may be the Sound Devices 7xx series. This gives you around 20bits of actual signal. In all cases the limiting factor are the analog circuits.

Gunnar

[xpander]

Why is it that on CD players etc clock mods are 'acceptable' but in recording decks we only see analog mods to input stages?
I know that decks are small but if a recording is made using a sub-optimal clock, what good is the ulta-low jitter clock in the CD-player that is going to play the audio?

It's all about the size and money vs. the gains commonly accepted. There is no way (yet) to even put highest quality pres and converters into the tiniest boxes people so eagerly would want to carry around, with all the features they'd like to see in them. It's always a compromise. A high quality clock circuit in itself would be about the size of the box these tiny recorders come in, and very much a wasted effort considering that rest of the circuit is not up to the task of really using the benefits of that clock anyway. There ARE already high quality recorders, converters and all in the recording business, it's the matter of accepting the price and the size in which that quality comes from, if it really is needed.

One thing sometimes forgotten is that all the recording procedures and gear used there are part of creating a sound. On the other hand, the playback system is usually expected to be able to reproduce all the sounds from different sources as is. In other words, there basically is no bad gear to make recordings, as long as it is able to do what you want it to do, sounding like you want it to. But the playback system is not supposed to have same kind of bias, otherwise there would be only one type of source it would play truthfully. In the real world this is rarely achieved anyway, so kind of a moot point. We tend to have a sound preference, bias towards something specific, it's even kind of built into our differing ears by the nature.


PS. I have built a better clock into one of my cd-players. Cost about $50, size of 3 ciggie packs in total (including the separate psu). Performs well and there is a difference, however small that might be to uninitiated. Any commercial manufacturer would offer the same in a smaller package, integrated better into the actual circuit...and the whole player costing about $500 more. They'd probably have the rest of the ckt changed in the same way also, like mine....and the name would be xxxSE, xxxmkII or something. But all this before mp3s became the standard of audio, like so many people seem to have audacity to call it nowadays. Pearls.

[ghellquist]

xpander.
Interesting to hear about your modding.
I believe it to be really fun and well worth it to do modding yourself. It might or might not make any large difference but it sure is worth the money just for the fun of doing it.

But marketing and selling mods to unsuspecting people is a quite different thing. I set much higher standards on that. For one thing you should be able to prove that what you say is based on measurable differences in the real world.
There are two very important things to notice about how we perceive clock jitter.

The first thing is that our minds are very easily fooled. Tell someone that this thing, whatever, is clearly superior and chances are that you will agree. Price is one such factor, expensive surely has to be better. The only way to handle this perception thing scientifically is to do true and well-designed blind AB tests. One way is to do a random sequence, say AABABBABBABBAB. On each change you say if it gets better or worse. In order to say that A is really better than B you should set a treshold, say 80% of the changes (statistical theory has ways to design this kind of tests). The really important thing is that there should be no way whatsoever for you to know the sequence.

The other interesting thing is that less clock jitter is not necessarily perceived as better. I know of no real scientific tests here, but I have heard statements to this effect but from real people and on the net. A certain amount of jitter may add a "sound" that you may like. Sort of like the way people like tape distortion.

Gunnar

[xpander]

The other interesting thing is that less clock jitter is not necessarily perceived as better.

That seems to be true, at least to some people in some tests...I've probably read same things about this as you.

I'm not ever selling my modified things or updated whatever, those have been purely for my education and fun, as you said. However, there have been some instances where other people have asked if I'd do the same thing into their gear, after hearing my stuff. That's a little bit different situation, and I have modded couple of things like that, no money involved.

Even though I understand the need for common reference points and proof, I'm not a big believer in "highly scientific" AB tests myself. I have listened some of my gear, the very same gear, even for decades. I will know instantly if something is not the same, given that I'm fully aware of my current state otherwise too and can adapt. The amount of rest, physical and mental stress levels, emotional state, surroundings with all the variables, they all have impact in how we hear also....or process what we are hearing. Being tossed into situation where many of the variables are not familiar and then presented with gear you have never heard before, and having no control over the music used, volume levels, nothing...man, I can hear pigs singing in tune or then again, might not even tell a mp3 from SACD. That in itself might be telling something about the lowest common nominators, but not necessarily anything about the best I can strive for by myself. Can't necessarily prove anything, don't need to prove anything. 

All this is of course different for people who would need the proof to sell something.

Fun stuff to talk about, but maybe enough for our forum here. Rest assured, my system doesn't have wooden volume knobs and the cables are not floating above the floor level, neither do I listen frozen cds or use exotic (snake) oil...but I can't really diss some people having that fun with their gear either.

Bringing this back to the original question, even a working mod might be useless or even worse than the original, if not applied well. I've seen some well made clock circuits myself, hacked into players in a way which will bring some troubles. For all that I know about that stuff, that is. Might not be much, after all. Also, a working improvement in itself and applied well enough, might still make the whole sound worse. Now the better part is just revealing a problem somewhere else that was hidden before. Some things are better left alone, otherwise you'll end up building the whole darn thing anew...done that too. 

[ironbut]

I think we have to remember that even the best portable recorder is built to a price point. It's been my experience with most all digital devices (portable, studio or home use) is that the bean counters have made their hits on the analog section of these devices. Cutting these corners rarely show up on the spec sheets. And as far as the major companies are concerned, what they can get away with is right up there with getting a product to market for Xmas! From my experience with digital audio the modifications that are so popular such as switching converters don't do nearly as much as getting the analog and power supply up to a level equal with the rest of the circuit. And since these are battery powered anyway, that pretty much leaves the analog circuits.