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Switchable impedence possible?
Posted:
Tue Aug 16, 2005 1:47 pmby Thunder Audio
Just curious - would it be possible to set the J99 up to have a switchable input impedence to better load my many ribbon mics? ...perhaps by having different taps of the input X-former going out to a switch/selector. I realize that that would mean the audio passes thru the switch/selector, but one wouldn't want to be changing that parameter mid-performance, anyway, now would one?
Thanx in advance for any thoughts on the subject...
Joe F.
Posted:
Mon Aug 22, 2005 10:14 pmby tpryan
Totally possible, just wire a DPDT switch to J1/J2. You'll be able to switch between 1K and 250R input impedances.
Posted:
Tue Mar 02, 2010 9:33 pmby RYAN
It seems that in the assembly instructions, it seems to indicate that 300ohm is recommending for ribbons, yet AEA makes a pre amp that has 18kohms. Wouldn't you want to go up from 1200 rather than down?
If this means that I can emulate what the AEA pre does with this kit, I am so sold.
Posted:
Fri Mar 05, 2010 1:08 pmby tpryan
Some old ribbon mics had low output impedances and would deliver a more useful signal driving a transformer input wired for a greater step-up ratio. Modern ribbon mics have transformers with a nominal 150 ohm output impedance and are happier driving a 1500 ohm or higher input impedance.
The AEA preamp is a transformerless JFET based circuit that has nothing to do with the J99.