General queries INF CNF order

[Stephen Langley]

Greetings all,

This is my first post, although I have been reading the entries of others for quite some time, and have made personal contact with a few members here and there. At this point I must congratulate Craig and Rick for such a wonderful support network for DC users. A fantastic resource - very much appreciated.

At last I've mustered the courage to go public with a couple of questions and would be grateful for any perspectives / experiences.

For both vinyl and shellac transfer I have noticed that when establishing a multifilter chain that the paragraphic EQ needs to be at the front end of the chain, otherwise a bubbly distortion can manefest, and I have less scope with the INF filter thresholds. Is this for any particular reason? As I use a flat preamp, my intuition suggests that I would be better filtering first and finally applying RIAA. I do everthing at 96/24 and dither down for the CD prep. I find that there is considerable more flexibility at the higher sampling rate.

I also wonder about using the CNF after the Paragraphic (RIAA) in the chain, as I believe that when sampling noise, it does so independently from oher filters in the chain (samples the raw 'flat' signal), but when engaged, it is effectively 'downstream' from RIAA. Wouldnt the noise characteristics therefore be different in application compared to the sample fingerprint? This may be a naive question...?

Finally, I have noticed that sometimes when I go to downsample and normalise etc, the system defaults to the non-filtered raw file rather than the one I have just filtered / editted. I must be doing something incorrect here (I get about it by saving the filtered file under another name, closing everything and beginning again from here)

Oh yes...I am hoping to put together a couple of portable turntables for remote use and I wonder if the flat pramps (CTP1000) are available as a prebuilt circuit board only, as I hope to mount them at the base of the tonearm? My current flat pres are from a homemade kit, but I thought it may be interesting to explore other options also.

Many thanks for your indulgence.

Stephen

[Craig Maier]

As a rule of thumb, the system was designed to have the EQ applied before applying the INF or the CNF. Applying a flat, unequalized signal to those filters can cause distortions and/or digital artifacts. With that said, some folks have gotten around that rule of thumb and have claimed to obtain superior results by applying the EQ last in the chain. I am not familiar with that technique or what paramater settings to recommend when operating the system in that manner. Again, it must be possible because people have done it successfully that way. Hopefully, one of the users who uses the system in that mode can advise you on that methodology.

The mathematical reason for this is that a so called "flat preamplifier" actually produces a non-flat audio spectrum (which is counter intuitive). In reversing the RIAA curve with the Paragraphic EQ, you are actually creating a flat response with respect to the manner in which the Vinyl LP was originally "cut". The reason for non-flat mastering of Vinyl LP's is improved Signal to Noise ratios achieved by accentuating the top end and attenuating the bottom end of the audio spectrum. Both the top and bottom end of the audio spectrum are cut in what is known as "Constant Amplitude" mode of operation, while the middle portion of the spectrum are cut in "Constant Velocity" mode.

I agree with your assessment about the CNF fingerprint when using a chain of filters in the multifilter. To get around that, you can use the Auto CNF mode which is adaptive in nature. That means that it determines the noise floor fingerprint on-the-fly and continuously adjusts itself to the material presented to it.

I am not sure why the system is defaulting to the non-filtered file when performing gain normalize, etc. Which mode are you using - - - Classic Edit or Fast Edit. Perhaps that has something to do with it. In classic edit mode, the system should always be operating on the Source (top) file. In Fast Edit mode, there is only one for it to operate on.

As for the purchase of the PCB's of the raw preamplifiers, you will have to ask Tracer about that. Although I performed its circuit design, I do not get involved in any production or OEM related issues. You can call Tracer at:

1-717-764-9240

[Jan Myren]

EWhere do I find the Auto CNF mode

HI!

You wrote:

"To get around that, you can use the Auto CNF mode which is adaptive in nature. That means that it determines the noise floor fingerprint on-the-fly and continuously adjusts itself to the material presented to it."

Does this mean that there is a way you can run through a whole chain of filters in one single multifilter also consisting of the cnf?

Best regards
Jan
NORWAY

[Craig Maier]

Quoting the Question:

"Does this mean that there is a way you can run through a whole chain of filters in one single multifilter also consisting of the cnf?"

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Answer: In short, yes.

If you have DC6, just set the CNF mode to Auto Spectrum. It will find its own noise fingerprint on the fly and adjust itself to changing conditions. (DC5 does not have this feature). If you do not have DC6 or want to take your own fingerprint and run the standard CNF mode, you can take a noise fingerprint seperately from the multifilter (by bringing up the CNF as a stand-alone filter) and save the noise fingerprint as a preset within the CNF. Then, when you put the CNF in the Multifilter, just bring up that same preset and you have it.