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PLLXO question related to LDR
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Posted on February 26, 2012 at 06:52:39 | ||
Posts: 495
Joined: October 26, 2011 |
Been wanting to try one of the new light dependent resistor attenuators as a passive pre in my system, to replace the old Channel Island jobber I use now. The recommended system requirement specs for this design is a source of around 200 ohms output impedance and a power amp of 47k ohms or more input impedance. I'm good with the output impedance spec, will be using a Dodd tube buffer after my DAC, utilizing a 6H30DR which will give me about a 100 ohm output. Power amp wise my Aragon(s) are low, 22k ohms, although folks have used amps with this low of input impedance and reported success. I was wondering, can a passive line level crossover be designed with a high input impedance, say 100K ohms? That way I can take care of two issues at once. |
RE: PLLXO question related to LDR, posted on February 26, 2012 at 09:07:12 | |
Posts: 4842
Location: Virginia Joined: February 21, 2002 Contributor Since: December 2, 2004 |
I would think a 100k input load would give you too much insertion loss to be practical. However I think this would work for your MMG's. R-HP = 6190 ohm C-HP = 1.7 nf R-LP = 5600 ohm C-LP = 120 nf (0.12 mfd) I calculate the insertion loss to be -2db and the minimum input impedance seen by your tube stage is 4740 ohm. Here's the Bode diagram comparing to stock: Here's my PLLXO spreadsheet in Open Office. "Our head is round in order to allow our thoughts to change direction." Francis Picabia |
RE: PLLXO question related to LDR, posted on February 26, 2012 at 09:28:17 | |
Posts: 495
Joined: October 26, 2011 |
Thanks Neolith, I sent you a PM |