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Old 4th December 2010, 06:15 PM   #1
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Default Which Preamp for Icepower 1000asp? (impedance)

I'm having a hard time working out what output impedance from
a preamp is suitable for driving a stock 1000asp module. input impedance = 8k

I currently have two preamps. a passive with 10k stepped pot
and an active tube manley purist - output impedance 50ohm.
The manley also has balanced XLR outputs, but I'm unsure
if the impedance still remains the same at 50ohm?

Either way are any of these suitable for driving the 1000asp module.

I will be using them in a tri-amping situation where the 1000asp
will only be driving bass. and a leak 20 driving the mids which likes
a really low gain or passive pre to work to it's best.
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Old 4th December 2010, 06:38 PM   #2
john65b is offline john65b  United States
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On my biamped setup with a pair of Icepower 1000ASP on bass panels of my Magnepan Tympani IVa, I have a Behringer DCX2496 Digital crossover between the preamp and the amp. The Behringer drives the amp, so I can use any preamp in front of the Behringer.

It is unfortunate that the ICEPower 1000ASP has such a low input impedance (I believe it is 10K, not that it matters). You can build a buffer and place it in front of the Icepower to raise its input impedance...thats what a Jeff Rowland 501 has, and a hefty price tag....
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Old 4th December 2010, 06:54 PM   #3
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Thanks John,

Is there any ready built circuit board you can think of on the market
that would work with balanced inputs? I did ask this question in another thread, but had any response.

what would be an optimal output impedance from the preamp or buffer to match the 10k input impedance of the 1000asp?
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Old 4th December 2010, 07:12 PM   #4
john65b is offline john65b  United States
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Some say the ratio is 10 to 1, other say the wider, the better. With a low amp input impedance of 10K, any pre with lower than 1000 ohms output impedance would suffice. Most SS preamps fit this perfectly, while tubeamps are a bit of a challenge.

Adcom GFP-750 comes to mind as far as excellent SS balanced pre, also a Pass Aleph 1.7.

Tubed Balance pre? I have only heard a BAT VK-3ix, and it was very very nice. I do not know its output impedance tho...

Have you considered a Behringer DCX2496 between any pre and the amps? It takes balance in/out, low output impedance, and can be had for $200. You can try different crossover slopes, Butterworth, Linkwitz Riley, Bessel, gain, delay, etc. I have a DIY Single ended 6SN7 Aikido, to the DCX2496 to the Icepower (bass) and Krell Clone (Mid/Ribbons) and am very happy. No issues with impedance mismatches either.

But your Manley at 50 ohms output should be fine. Try it out.
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Last edited by john65b; 4th December 2010 at 07:20 PM.
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