Eldartford, you are right about that process, but the producer of an LP would never have the EQ of the RIAA messed with! Usually the issue is a private studio and producer have made a recording. They want an LP, so they send the tape to someone who can do that. Usually they also send a tape of test tones made on their tape machine, so the LP manufacturer can set his tape playback to match the calibration of the original tape machine. Then he makes the LP.
The producer then gets a test of the LP and listens to it. He may ask for changes in the tape playback calibration (this is something *very* different from EQ, BTW) in order to get the LP to sound more like it did when the recording was made.
If the LP is being pressed in a different country, this process is often broken. That is one reason why it is so important to get an LP that is pressed in the country where the recording was originally made!
It is a tricky process, no doubt, and full of errors, but one thing that no-one ever seems to mess with is the EQ curves. For the most part, there is a very genuine effort to get the LPs to sound like the playback of the master tape. |
Eldartford, my cutting lathe has a set of 'pre-emphasis' modules that are in fact the inverse RIAA curves- if you put their output into a phono preamp, the result should be flat.
It sounds to me that what you are getting at is that not all cutting systems are created equally, not all mics are neutral as well, that sort of thing, and you are absolutely correct.
However, you might be surprised but the cutter manufacturers were actually quite concerned about getting the pre-emphasis correct, to the point of hand-picking components to make it so. The same is true of any high end phono preamp manufacturer; after the hand-picking process we wind up with a substantial stack of unusable EQ components!
Raul is absolutely correct in saying that EQ errors of only 0.1db can be heard and he also gave the correct reason why- its a spectrum, not a single frequency. That makes a huge difference to the human ear.
In the end, this makes it possible to evaluate components used in the recording process, such as mics and recorders. Although 0.1 db seems like its not very much, it **can** be measured quite easily, and the math for generating the EQ networks is well established.
I have seen at least one manufacturer claim that due to other errors, RIAA EQ is not important. IMO such a claim is rubbish and if a manufacturer says that to you, turn around and run as fast as you can! |
Eldartford, when dealing with calibration of a cutting lathe, the speakers are not part of the equation. To answer your question to Raul though: we are, 'we' meaning the people who make this stuff to standards like this. 'We' say its bad when there is a boost or a roll-off that does not conform to the curve. Its not a matter of over-design either. You *can* find parts that a close enough in tolerance that they will do the job. |
Eldartford, the unit that I use has bandwidth out to just shy of 30K. The electronics have a bit more than that, but not much (they were designed in the late 60s). I don't think you could say that there is a 'typical' cutter, as they are all designed (like anything else in this world) to meet certain parameters that the designer felt was important.
I chose the unit I did based on hearing the LPs that it was know to have made, and also for the fact that I can get our amplifiers to drive the cutter as well- resulting in the first vacuum-tube transformerless cutter system. |
Eldartford, it might be, but in the world of high end, the difference between HIFI and the ability to sound like real music exists in the nuances. That is why there are Teflon caps, high precision resistors, care in grounding layouts, spec-ing out the gear octaves beyond human hearing, use of high purity wires, balanced operation (in our case anyway), non-ferrous chassis, *tubes* and whatnot.
We are trying to make it sound real. All designers probably have a blind spot, usually a focus on what they think is important :) so you will see a wide variation in designs as a result. It is the mark of a good designer to know what specs are 'negligible' and which ones are really important that *look* negligible. I don't think I am in a position to really judge exactly what that might be, because like everyone else, I have my blind spots too. In the case of EQ, we can spec the EQ components within 0.05% pretty easily, so I don't think hitting 0.01% should be all that much harder. |
Eldartford, that one is easy! We use a linear recording method, even if recording digitally. By that I mean linear as opposed to logarithmic.
The linear system requires flat frequency response. So we adhere to getting the RIAA correct in the same way that we make the linestage and amplifier absolutely flat frequency response.
IOW, its easy to get 0.1 or better flat frequency response from the AUX input, if we can do that then the phono should have the same benefit. Perhaps I should say *especially* the phono should have that benefit, since, for many, like myself, it is the primary playback source. |
Eldartford, its my opinion that in high end audio you build the equipment to do the job, then figure out how much it costs when you are done. It is a bit different from targeting a bomb :) |
I might have a different viewpoint here- I feel that it is not a good idea to excercise synergistic effects. Instead, I prefer that each component operate out of its own strengths, that you are not compensating for a brightness in one component by using a dullness in another. IOW there are no synergies, just strengths.
That may be the same as Raul was saying, not sure, but I thought it might be useful to clarify this. People ask us if our equipment is 'voiced' to work together, and it certainly is not, other than our amps and preamps are balanced and all-tube: that's the extent of it.
So this is why we take care with the RIAA- we have no idea what amp or cartridge will be used with our preamp; whatever coloration that might appear as a result will not something that is occurring because we were sloppy about EQ or didn't care. The response will be flat whether its phono or CD. If a cutter from the 60s had a problem, its not an excuse on our part to be negligent, all that results is now you have an instrument with the resolution to really know what is on the various LPs! |
