embossing test, low volume

[Pure2]

Hi dears,

I'm Marco from Italy, this is the first time that I write here, I hope to explain in my best way
I'm trying to emboss some mastered track on blank, but the results aren't good.

I use a late machine from David project, the file audio come from a NAD preamplifer to the Audio Research D240.
The RIIA eq curve is applied to the audio in my DAW.

I tried to increase or decrease the angle of stylus (embossyng styl Presto) and tried to increase or decrease the weight, now is around the 40gr, but without any success.
Anytime that I try to increase the volume, the groove become irregular as the pics attached.
If I emboss the silent the groove is regular, without a strange frequencies; if I try to emboss the 1Khz test tone around the -20db, all is ok,
but if I try to emboss some audio file, mastered, added RIIA eq curve at -6db, as soon as I increase the volume, the groove become irregular.

Have you some suggestions? please.

Cheers from Italy,
Marco

[markrob]

Hi,

If you are using the full RIAA recording curve, you will get very bad results. The low frequencies will be over boosted and you will have wildly large excursions. You need to develop an EQ curve that works with your open loop head design. The published RIAA curve assumes your head is flat vs. velocity. This is most defiantly not true. Best bet is to cut a pink or white noise test signal at about 1 or 2 watts and look at the playback spectrum. Use White noise if using an FFT based spectrum and pink noise if a RTA 1/3 octave analyzer. Equalize the playback to be flat and take a second pass using that curve. After a few iterations, you should be in good shape. Make sure you are not boosting too much at the high frequencies as its easy to mistake the noise floor for the signal when using a noise source as your test cut.

Mark

[Sylvere]

hello,
what kind of microscope do u use it, please ?
cause i m looking for a microscope with vga output to be able to watch grooves in closeup on screen !
thx to u.
syl

[Pure2]

Hi,

If you are using the full RIAA recording curve, you will get very bad results. The low frequencies will be over boosted and you will have wildly large excursions. You need to develop an EQ curve that works with your open loop head design. The published RIAA curve assumes your head is flat vs. velocity. This is most defiantly not true. Best bet is to cut a pink or white noise test signal at about 1 or 2 watts and look at the playback spectrum. Use White noise if using an FFT based spectrum and pink noise if a RTA 1/3 octave analyzer. Equalize the playback to be flat and take a second pass using that curve. After a few iterations, you should be in good shape. Make sure you are not boosting too much at the high frequencies as its easy to mistake the noise floor for the signal when using a noise source as your test cut.

Mark

Hi Mark,
thank you so much for your reply, sure in the next days I will test it

marco

[Pure2]

hello,
what kind of microscope do u use it, please ?
cause i m looking for a microscope with vga output to be able to watch grooves in closeup on screen !
thx to u.
syl

Hi Syl,
I'm using this one https://www.amazon.it/dp/B07L8KGKQP?psc=1&ref=ppx_yo2ov_dt_b_product_details
it's a cheap model but for easy use isn't bad but the output is only by usb cable.

marco