New to Grampian D. Summing up.

[uvoscillator]

Hello Trolls !
As always, thanks a lot, that you're here guys ! That is the only place that helps to start up cutting !

Less than year ago I get Rek-O-Kut M-12 with M-41-8 head to start my cutting way,
and I was surprised, how good it can sounds to me ))
So that was start for my sound art archive project:
http://cyland.bandcamp.com/
Of course it sounds less than semi-pro, but I was happy to get it sound at all )
So not some time ago I decide to invest some more money, and accidentally get burned Grampian D and suitcase Rek-O-Kut M-5 lathe, that seems to be my sweet company for many years.
Grampian is mostly done, and very soon it will come from service.

In parallel I working on feedback summing pre-amp, based on schematics that I found here, thanks Flo, Mark, and others who answered my questions this year...

But I want to be fully weaponed when Grampian will back home !

And most important question now - how to calibrate sound source -> pre-amp -> power amp and the head?

I just bought old level meter from big console - BEAG MAK 113, heard that it is very nice and precise meter.
It is stereo, so I can use it's two channel separately, to control different points level.

How to do next right ? Meter after preamp? After power amp? How much volts I need to run on Grampian at 1000Hz?
How to calibrate my rack to 0db?
I'm sorry, I'm still profan on most things, trying to read books, but on english it hurts, I do, but get 10% information right way

Help me to save my new gear !
Best wishes from St.Petersburg !

[markrob]

Hi,

You want to measure the power level right at the head. The Grampian spec shows 1.5W at 1Khz for 7cm/sec recorded velocity. I assume this to be peak, not RMS. This would yield 5cm/sec RMS. This is a pretty standard 0db reference level for cutting. If you strap you meter to measure the amplifier output voltage and it has VU style ballistics, that would equate to a voltage across the head of 4.74 Vac rms based on the head rated 15 ohm impedance. P = (V^2)/R I think you are best to use an average reading meter rather that a fast responding peak. The best would be a meter that reads both. If you allow +12db peaks over the 1.5 Watt 0 reference, you will need a peak power of 23 watts at 1 khz. Due to the RIAA, you'll need quite a bit more to handle the high frequencies. The Grampian was originally sold with a 150 watt amplifier.

Mark

[audadvnc]

Note the +18dB rise in power as you approach 20KHz on the RIAA curve. If you have been doing initial setup at 500 or 1000Hz, you'll need to turn your reference level down about 20dB (that's 10/1 voltage), otherwise you will toast that cutting head in very short order. Take it from me...

[uvoscillator]

Thank you for the answers ! I'm a bit closer to truth )
Will check with both UV meter and voltmeter... Thinking about RMS.

As I understand it is better to cut under 100(?)Hz and above 16KHz, right ?
My tube is 100W, and has switch 8 or 16 Ohm, so better to use on 16 if Grampian is 15Ohm?

And of course I'll put in line 3/4Amp fast blow fuse.

[powerstrip]

hi uvoscillator

I do not have a lot of input on the grampian D but would like to say, congratulations on your adventure into cutting, I see hints of people cutting in russia, but mainly, St. Petersburg has to be the most beautiful city in the world to me, glad to see you on here, I am dying to pay a visit some day! It's a huge goal in life for me

Good luck in the adventure!