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Old 21st July 2013, 10:26 PM   #1
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Default Raising Input Impedance on 200ASC

I recently got a pair of Ice Power 200ASC boards and have read since the input impedance is so low (around 10kohms) it can suffer from high frequency roll off because the source might have to high of an out impedance.

My Wyred 4 Sound DAC 2 has an output of 100ohms and i can not hear this roll off but maybe with a tube pre amp, which could be 600-2.5kohms output.

It's my understanding the 10kohms standard rating is for a balanced signal and would be halved with an SE input (around 5kohms then).

I'm looking to raise the input impedance of this amp. Why? To learn from the whole experience and have an amp that functions better then it's original form.

I've asked Kevin at K&K audio about this matter and he suggested i use an LL1571 mic transformer and wire it as a step down, which will raise the impedance to around 30kohms but drop the gain voltage by 4db, which isn't that bad but could be with the wrong source.

Other options would be an input buffer and use the 12v auz power on the board or an "instrumentation amplifier".

Can someone help me out

Matt Kraemer

BTW these babies will be going into a fully CNC'd case

Like my last project using the Hypex NC400's....

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Last edited by Kraemerkid; 21st July 2013 at 10:41 PM.
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Old 22nd July 2013, 04:51 PM   #2
bwaslo is offline bwaslo  United States
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Too low an input impedance won't cause High Frequency rolloff (it would actually be slightly less likely to rolloff from cable capacitance than a higher impedance input might be; though with a 100ohm source, it's not really gonna happen much with either). It MIGHT cause the preamp to have more distortion, as it would draw more current from it, but unless the preamp/DAC is quite wimpy, that's also not likely to be an issue. Tube preamps that are current challenged might, though.
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Old 22nd July 2013, 05:04 PM   #3
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Thanks for the reply.

I do not hear the roll off personally but was just wondering
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