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Author Topic: Mesa GEQ Inductors - Gyrators  (Read 3047 times)

mensur

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Mesa GEQ Inductors - Gyrators
« on: October 11, 2009, 06:09:14 AM »
Hi guys,
I'll try to replace mesa inductors with gyrators, but I need some help:
1.Is the transistor emitter bias resistor fine(6.8K), or I should use another value?
2.Do I need to use dual voltage supply for the circuit?



Thanks
« Last Edit: October 11, 2009, 07:58:57 AM by mensur »

J M Fahey

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Re: Mesa GEQ Inductors - Gyrators
« Reply #1 on: October 11, 2009, 10:33:47 AM »
Hi Mensur.
6k8 is fine, so far so good.
What worries me is that you draw only *part* of the circuit, we donĀ“t know where those gyrators are connected and powered, how they are biased, etc.
Please re-draw the full GEQ schematic as you intend to build it, along with the original one for easier comparison.
I'm not checking your inductor-to-gyrator transformation, I assume you did your homework correctly.
The original GEQ uses PNP, negatively-powered transistors, because Mesa happens to have "free" -50V available (the 6L6 bias supply), but you can build an all NPN version if you wish (or stick with the PNP original)
NOTE: *please* post drawings smaller than 4000x1400 pixels.
We get stuck with unreadable miniatures or "the tree hides the forest" ones.
Good luck.
Juan Manuel Fahey

mensur

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Re: Mesa GEQ Inductors - Gyrators
« Reply #2 on: October 11, 2009, 10:55:55 AM »
I used NPN transistors (like Mesa did now on MarkV), but which power supply(30V) I should use, dual or single power supply for the gyrators?
And are the Q-point resistors fine,how can I determine them?
This my version of GEQ: