Ask a designer

[jammy395]

Why do LP's not track from the center to the outer edge, like CD's do.

This would help facilitate replaceing the arm back onto its rest once side is finished - Thus greatly reducing the chance of scratching your records....

Just a thought - "Resistance is futile"

[Dr Bunsen Honeydew]

Maybe because the stylus would fall off the record at the end of side.

[Lindsayt]

You'd just need to cut a proper run out groove. Technically inside to out makes a lot of sense - especially for orchestral works.

When cutting the master disks I suppose it makes the job easier in terms of deciding how wide to make the grooves as if you misjudged it from inside to out you'd overshoot and miss out on the last bit of the recording. If you erred on the cautious side you'd have a lot of wasted space on the outside - which would result in an overall worse sound for rock and pop.

These days off course you'd just get a computer to calculte it and do it properly, but in the old days they didn't have that.

[Dr Bunsen Honeydew]

An add on for the moment about SUTs (step up transformers) from earlier post.

A transformer is two coils wound around a magnetic core or air cored. In the SUT case the second winding is larger so that the voltage from the output of the SUT is larger than the input voltage. But remember electricity is made up of voltage and current and there is no free lunch in electronics. So by increasing voltage you have to use available current to do this. The source for that current is a moving coil phono cart running in the groove of a record, now how much current do you think that generates - well bugger all - which leads to loads of problems designing SUTs just to work!!! - I will continue this theme later.

Now problems with coils / chokes in this application. Read this http://en.wikipedia.org/wiki/Choke_(electronics) http://en.wikipedia.org/wiki/Coil and you will see the major function of a coil is as a filter so it doesn't take much intelligence to see another problem associated with SUTs. Again good design can help, which i will come back to, but it can never completely alleviate this problem.

Edit - links are not copying correctly, you have to relink at the wiki page.

[Daniel Quinn]

Re - records - Is there not something about the diameter of the circles effecting the bass response . Peter Gabriel track listing on so was determined by the more bass heavy songs being the first songs on either side as he couldn't get the bass response required on the smaller inner groves . [ something amended with the 25th anniversaty addition ]

Also Us is a double album not for time reasons , but because the inner circles are simple not used at all and the record ends about 60% in .

[Dr Bunsen Honeydew]

A filter curve RIAA is used so that the modulation in the grooves is not too large for the stylus to cope with at bass frequencies. Replay RIAA *is bad* as it is a filter, but it is a filter we have no choice with and have to put up with.

http://en.wikipedia.org/wiki/RIAA_equalization

[Lindsayt]

Another question. I've read that the dynamic range of CD's is 90dbs (compared to vinyl of 70 to 80 dbs). Is this the real usable dynamic range of CD's? My understanding is that the distortion level in CD's increases as the recording level decreases. A major contributor to that will be granularity - where there's not enough bits to represent the signal properly. At what point does granularity become noticeable in CD's? For example if the recording is 50 dbs below maximum possible level, will granularity - or some other distortion become objectionably apparent?

[Dr Bunsen Honeydew]

CD's are digital beasts, I am a analogue engineer / designer.

[Helge Gundersen]

I can't answer the CD question, but the only uncompressed recordings I have are those on the CIMP label, and they write:

CIMP records are digitally recorded live to two tracks. Digital recording allows for a vanishingly low noise floor and tremendous dynamic range. There is no compression, homogenization, eq-ing, post-recording splicing, mixing, or electronic fiddling with CIMP performances. Compressing the dynamic range is what limits the "air" and life of many recordings. Our recordings capture the full dynamic range one would experience in a live concert; many of them have a dynamic swing of over 85dB.

We set our levels so that the maximum signal will not overload the recorder. This means that the average level will be much lower than you are used to. If you set your levels during the loudest passages to be reasonably loud, the rest will fall into place. You may find passages where the signal is almost inaudible. Resist the temptation to turn the volume up; this is the way it sounded when it was recorded and was the dynamic intention of the musicians. In this regard these recordings are demanding. The quieter your system and the lower the noise floor of the listening area the more impressive they will be.

[Dr Bunsen Honeydew]

Adding some more to the SUT thing. Now we have established as fact that in order amplify a SUT has to exchange voltage for current and there ain't little or any current to exchange. So how does it do it - well with great difficulty. Because it works on the margins of what is possible it has to built to the nth degree not to have internal losses, which is why good SUTs cost a fortune and cheap ones are a waste of time. Transformers are naturally lossy things, if you want them not to be you need masses of very good quality steel plate and large and pure copper (or preferably silver) coils = large amount of money and large size. Even then it is really struggling and has to be perfectly matched to the input and output load to be able to function correctly (input coil - input load, output coil - output load). reason there is no current head room. Think of the SUT as a swing door that is swinging too and fro at the frequency of the music. It need energy, a push to make it function, that energy is not there just to force the door open and closed so it has to match to the door as much as possible so as not to fight the door but go with the flow. That means when things change (musically) the door does not respond quickly, as there is no power to change too quickly or too much. this tends to give a soggy smooth presentation that is nice but not musically accurate. the world through rose coloured glasses again like valves which is one of the reason bottle heads like SUTs.

Now well designed solid state active phono stages (very few are well designed). You can build in massive amounts or power and headroom relative to the jobs being done. the door is pushed and swung around very easily and the speed it can change and react to amplitude and speed changes is instantanious - reason is that that large headroom means there is no need to perfectly match, the door is just bashed open and closed by power. This is referred to as load rejecting because matching is no longer a large consideration, it just becomes a very minor musical balance preference. BUT we still have all the forum bullshit about cartridge matching that only applies to SUTs, even some active phono stage makers have pandered to it by giving load adjustments switches for the customer, a waste of time and the switch contacts themselves damage the music at that low signal level.

Now the trade off for me is that 1/ SUTs are quieter in terms of thermal noise, but noisier in terms of hum and they alter the frequency balance of the music at the frequency extremes as a coil can only be built to be 100% efficient at one frequency, either side you get progressive attenuation. 2/ Active have no attenuation at frequency extremes unless you build it in to simulate a SUT (some idiots do this), it reacts far faster to the musical changes which can be a shock if you are not used to it and you like your comfortable valvey type sludge musical presentation. Disadvantage, active has higher levels of thermal noise so the noise floor is higher than a SUT which can slightly mask midband information, but with the best actives this is not noticeable or a problem.

You pays yer money and you takes yer choice all I am pointing out per usual is the bullshit that takes away your choices if you believe it. Using a SUT is like preferring to use a bucket and washboard to an automatic washing machine - bloody daft in this day and age IMO. AND to get good ones costs a bloody fortune and lays you open to yet another industry rip-off.