Using the Paragraphic EQ to set Turnover and Rolloff

[James]

Thanks Craig,

Been a little tied up of late, but still doing this. My question still stands. What in the picture you posted is showing me that the Turnover is 500 Hz....or 400Hz....or whatever. Based on what I see (and understand) at the 500 Hz point, the line is intersecting at 8.5-9db. How does that equal 500 Hz...or 400 Hz turnover?

[Craig Maier]

Turnover should be defined as the -3db attenuation point of the low frequency shelf starting frequency relative to DC. I forget what that turnover frequency was - - - I guess it should be clear on the graph.

Craig

[Craig Maier]

Just looked at the graph, and it looks like that has a corner frequency of 400 Hz (3 dB down at that frequency).

Craig

[James]

1) Still lost Craig. What does this mean? - "-3db attenuation point of the low frequency shelf starting frequency relative to DC."

2) Say I want to set something at 500 Turnorver, -8.5 Rolloff. What will that look like on the graph?

[Craig Maier]

- 3dB is the engineeering definition for the corner frequency of a filter relative to a reference level. - - - I would like to help further, but I have exhausted my ability to explain a turnover shelf function. I tried. Maybe someone else can help.

Craig

[Dan McDonald]

I'm not an engineer, but try this, James. When you look at the graph, find 400 Hz (as Craig mentioned - that's approximately where it is on this graph). Go up to where you see the "shelf" - that is, a straight line, in the lower frequencies, That's about 12dB. Then check where the curve intersects with 400Hz. You'll see it's about 9 dB, so that is -3dB below the 12 dB. The left hand axis is in 4 dB increments (4, 8, 12 etc), and the curve hits 400Hz about where a 9 would be if it showed 9.

[Marc Hildebrant]

James,

Could you restate what your goal is ? Also, as has been stated, is the needed setting in the virtual phone preamp section ?

Marc

[James]

Thank you all for trying to answer my apparently poorly asked questions. Frankly, I had given up on this for quite some time. But, thought I would wade in again and try to understand this.

Perhaps, the best answer...to start....would be a picture. Can someone please post a picture of what would the paragraphic EQ look like if, for example, I wanted to set it for a Turnover of 375 AND a Rolloff of 12?

[Craig Maier]

We have been through this for a long time. Answer: I do not know. Maybe someone else does know. However, if you want the NAB curve, it is in the Virtual Phono Preamp (VPP) as a preset called Approximate NAB LP curve. Approximate means that it is within 1 dB of the ideal curve. I sincerely doubt that any human being can hear a 1 dB deviation from an ideal curve, especially considering that the record was mastered using EQ circuits consisting of resistors and capacitors and electron tubes (with the capacitors having tolerances of +/- 5%).

Craig

[Dan McDonald]

How about if you say what you have (e.g., 78 rpm record recorded via a standard stereo amp, or a flat preamp, etc.) and then it might be easier to explain what to do with it.

[Craig Maier]

All of those things are in the VPP, so that is my easiest explanation about it. That is why we created a VPP.

Craig

[Dan McDonald]

Yes. I was just wondering why that's not working for him.

[James]

I play my record, through my RIAA stereo, into my computer. I thus have a RIAA sound file. I use the Virtual Phono Preamp and for 'preamp hardware', select 'Standard RIAA preamp'. For record type, I select 'Acoustical', thus converting my file to a flat signal. I go about my sound restoration.....

At some point near the end, I want to convert the file back to its CORRECT Turnover and Rolloff setting. Here is the point where I can't seem to understand, or get an answer.

1) If I want the recording to have a Turnover of 375 and a Rolloff of 12, how do I do that?

2) If I want the recording to have a Turnover of 500 and a Rolloff of 5, how do I do that?

3) If I want the recording to have a Turnover of 250 and a Rolloff of 16, how do I do that?

4) If I want the recording to have a Turnover of X and a Rolloff of X, how do I do that?

If I understand correctly, and perhaps I don't, the Paragraphic EQ is supposed to allow me to set any Turnover and Rolloff I desire. But how do I get there? I understand that I need to select 'Low Freq Shelf' and set number of filters to 2. I have that. Easy enough. But at what points on the grid does the line need to cross, as set by the two adjustable points, to make my desired settings occur? If I understand correctly, Rolloff is the rate of treble attenuation in db at 10 KHz. I have attached a picture. Does this picture indeed show me setting the Rolloff at what would be defined as '12'? My question is never about how do I get the settings dialed into the nearest 1db or within 0.5 hz, well beyond the ability of human differentiation. It is just how do I set this, within whatever 'margin of error', to the industry standard primary points.

I have a 1950's Scott Dynaural 121-C. I can turn the knobs and achieve any of the settings I want. I have a 1990's Owl 1. I turn the knobs and can get any of the (pre-specified) settings I want. If I were to order a new preamp, I could turn to knobs and achieve any setting I want. How do I make the Paragraphic EQ do the same?

[Craig Maier]

As I said, I do not know. Find somebody who "knows". It's not me. The only thing that I "know" is that the Diamond Cut VPP has a very large array of phonographic settings, including NAB. If you choose not to use the VPP for phonographic applications, well, I do not know (or understand).

I use a flat preamp and the VPP. If I did not have a flat preamp, and only an RIAA preamp, I would reverse the RIAA curve with the VPP and then choose the preset that corresponds to the record type that I have, and it will apply that curve in a second step of the process.


Craig

[Craig Maier]

Please go to the following link to create non-standard record EQ curves that have been transferred via an RIAA Preamplifier: http://www.diamondcut.com/vforum/for...onograph-curve