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Old 24th Sep 2019, 4:30 pm   #9
Levente
Hexode
 
Join Date: Nov 2016
Location: Budapest, Hungary
Posts: 348
Default Re: Vintage Radio and Phonograph cutter schematic

Okay... I am reading do much about this and really into it... just a thought on frequency responses vs cutter head.. would it be possible to increase the frequency response of the given crystal cutter if:

1. the cutter is wired for modified constant velocity ( i think, looking at the schematic, it is)

2. Knowing the capacitance of the cutter head and calculating the impedance at 100 cycles and the highest desired cycles

and the this (copied) :

If, when using the crystal cutter, the impedance of the driving
source is made equal to the impedance of the cutter at any frequency,
the cutter response drops at the rate of 6 db per octave above that frequency. The impedance of the .007 pi capacitance of the RC -20 cutter
for instance, is approximately 44,000 ohms at 500 cycles. If it is fed
by a 44,000 -ohm source, response (stylus movement) will be constant
for all frequencies below the 500 -cycle point of equal impedances ; but,
as the frequency rises, it will be reduced at the rate of 6 db per octave.
Under these conditions, the response is exactly the same as a magnetic
cutter cutting modified constant velocity ! Merely by adjusting the
source impedance we can adjust the characteristic for any desired turnover frequency or we can cut constant amplitude, which is merely a
characteristic in which the turnover frequency is above the usable frequency range, and so, practically speaking, does not exist.

4. raising the cutter head voltages 75 RMS is the working voltage, but capable of 280 according the data sheet...

5. (copied) When modified -constant -velocity response is cut with a crystal
cutter, driving voltage may be increased. With the RC -20, a turnover
of 500 cycles will permit driving voltage of 150. Voltage overloads must
be carefully avoided, or the crystal may be cracked.

considering the above, a cutter head of 7500 cps would be capable to produce higher frequencies? or am I getting confused on this...
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