Tank Circuit Math

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xlrider

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Tank Circuit Math
« on: 15 Sep 2008, 03:47 pm »
Can anyone help me decipher the Math, Frank used in Audio Basics?


For example, -RLC, is the "R" just a negative number, or is "RLC" all negative numbers?
I need to use the specifications for the Grado Green to finish the questions:

Input Load = 47K, Inductance = 45mH, Resistance = 475

Series Resistance of Cartridge Coil "R" would be 475?
Inductance of Cartridge Coil "L" would be 45 with  a -3 exponent, or is it just 45?
Cable capacitance  "C"  1pF = 10 "-12 exponent"?

Frank states, in his News Letter, that this formula "can be handled on any simple calculator"
So, maybe I am making this too complicated for myself.
BTW... $5.00 1982 dollars, is now $11.40   ;)

Thanks:
Tim

oneinthepipe

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Re: Tank Circuit Math
« Reply #1 on: 16 Sep 2008, 02:25 am »
BTW... $5.00 1982 dollars, is now $11.40

Unless it was $5.00 worth of gasoline; that would cost $14.78 today.

acwd1950

Re: Tank Circuit Math
« Reply #2 on: 16 Sep 2008, 02:47 am »
RL=122.38 is my answer, but dont bet the farm on it!

Steve
P.S.
-RxLxC is how I figured it

Speedskater

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Re: Tank Circuit Math
« Reply #3 on: 16 Sep 2008, 01:14 pm »
Cable capacitance  "C"  1pF = 10 "-12 exponent"?
1pF seams like a very very low value.

Tom Alverson

Re: Tank Circuit Math
« Reply #4 on: 16 Sep 2008, 01:59 pm »
1pF is way too low for the cable capacitance.  I would guess  more like 100pf.  If you use that value, you should get an Rl  value of around 10000 ohms, which is the value Frank uses to load Grado cartridges.

Tom

avahifi

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Re: Tank Circuit Math
« Reply #5 on: 16 Sep 2008, 02:05 pm »
Correct Tom.  Good to hear from you again.

Regards,

Frank Van Alstine

Tom Alverson

Re: Tank Circuit Math
« Reply #6 on: 16 Sep 2008, 02:20 pm »
I used Excel instead of a calculator.  I have posted the spreadsheet here if you want to use it:

http://nu8d.com/Documents/phono.xls



TheChairGuy

Re: Tank Circuit Math
« Reply #7 on: 16 Sep 2008, 02:38 pm »
Tim/xlrider,

Tho the math may lead you to a resistive setting of 10-12K for the Grado Prestige series....actual trial and listening will dictate something higher.  A cartridge is not purely an electrical device....it is affected my many mechanical factors...which skews the results.

Loading a Grado at 10-12K will likely result in overdamping it...leaving it with a limp version of its robust self. I found 27K to sound right in my system...my Grado has the Longhorn stabilizer, Frank's recipe for 1000cst silicone on the coils and an EAR Isodamp wedge (between body and headshell) on a 12gram/internally oil damped tonearm (along with a higher end shibata stylus from a G1+). 

All these non-electrical matters factor greatly into the purely electrical-based formula of Franks (and Jim Hagerman's resonance calculator, too).  Grado themselves now indicates just leaving it at 47K...better to be relatively underdamped than overdamped I think is their gist.  Once upon a time they listed 10K loading for their G and prior series, now they note 47K (on even the lower inductance low output Woodies).

That's not to say Grado is neccessarily 100% correct either...but something in between the two extremes 10-to-47K is likely about right.

There is a year-long post, viewed some 40,000x or something over at the Vinyl Engine on this topic  :o  I have to say it is the most beneficial topic on one's analog front end performance I've run into in a long time on the net (next to being told about the wonders of mortite caulking compound 25 years ago, and later re-discovering it in a sense thru Frank and Audio Basics with the use of Plast-i-Clay internally on many decks)

John

xlrider

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Re: Tank Circuit Math
« Reply #8 on: 16 Sep 2008, 04:27 pm »
Thanks everyone, for your input...
What I am trying to do is use Hagerman's Ripper ADC to move my LP's onto CD's. I don't want to spend a lot of money and, I would like to re-sell my setup. I hesitate to use this forum, but I thought I would get an answer to Franks equation here.
(I did have my Dynaco SCA-80Q converted around 1982, when Frank's place was still called Jensens Stereo Shop)
 
I posted a question to Hagerman's forum, last year and TheChairGuy suggested that I use Hagerman's Online Calculator. Hagerman's Calculator doesn't take in account "Series Resistance", I don't know if that matter's, I just would like to solve Frank's equation, and compare results. I also asked Hagerman, and he said:
I would listen first, before playing around with loading.

jh
OK..
I looked at Tom Alverson's XLS file, thanks to Tom
The problem I was having yesterday stems from an explanation I found online.
http://www.purplemath.com/modules/exponent4.htm
Frank say's in Audio Basic's, that the equation can be solved with a "simple calculator" "circa 1982", a simple calculator back then would only have a 10 digit display, according to the link above, I would need to move the decimal 12 places in order to calculate capacitance.

For now, I think am going to take Hagerman's suggestion, and listen first.


acwd1950

Re: Tank Circuit Math
« Reply #9 on: 18 Sep 2008, 12:28 am »
Did Anyone figure it out? Im curious about the answer that is all? Whats this for anyways?

Steve