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#1
03-26-2017, 01:30 PM
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Passive pickups through audio interface
So if I run an acoustic with a passive pickup, say a k&k for example, into the input of my focusrite saffire 6 USB audio interface, will that act as a preamp? It's mic preamps but are they the same? Or will I need a separate preamp as well?
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#2
03-26-2017, 01:51 PM
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Quote:
If the input impedance of the instrument input is about 900k Ohms or greater, you'll be fine. If it is less, particularly if it is much less (e,g,. 300k), you won't be fine. Generally, many interfaces provide 1 MegOhm or greater input impedances for their instrument level inputs and some provide less. I suggest you keep asking for the impedance spec for the instrument input. Perhaps you could call Focusrite in the UK or USA and talk to their tech folks.
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#4
03-26-2017, 03:05 PM
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You can just try it, as it won't damage anything.
If it's a piezo pickup with small elements and sounds thin and lifeless with hardly any bass or low mids, then you'll need a high input impedance preamp to go before it for best results. If you buy a preamp, make sure it matches your pickups. K&Ks have fairly large piezo elements and can get away with 1 MegaOhm. If it's an under-saddle element with smaller surface area, then you'll want something with a high input impedance. I've found even K&Ks sound better input 2.2Meg and above. Any extra bass can be easily EQed out, but passive pickups just sound more 'alive' to me with higher input impedances, even if I have an EQ pulling down the bass. This applies doubly to passive USTs, 1Meg is just too heavy a load. I built up a pre-amp with a default 10 Meg input impedance that I can switch down to 4.7, 2.2, and 1 Meg. As it stands, I always just leave it on 10 Meg, as that is where everything sounds best to me. The K&K still sounds good at 4.7 and pretty good at 2.2, but the Baggs element really prefers the 10Meg setting, as do the Graphtech ghosts in my electric. The Fishman power bridge was good down to 4.7, but lost 'oomph' at 2.2 and 1.
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#5
03-27-2017, 03:43 AM
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Thanks for your replies. It's a k&k I'm talking about, does anyone know if this specifically will be ok through the focusrite? I haven't bought it yet you see and I need to know whether I need to factor in the cost of a preamp...
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#7
03-27-2017, 09:28 AM
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UKPAULIE, I plugged my K&K Pure Western mini into my Focusrite Scarlett this morning and it worked just fine. I kept the input levels the same as I use plugging my outboard mic preamp into the Focusrite and got a very workable signal.
I understand the pre amps in my Scarlett and your Sapphire are the same.
__________________
Goodall, Martin, Wingert
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#8
03-27-2017, 03:35 PM
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Quote:
It was based on a positive feedback arrangement around an ultra low noise low power opamp from Burr Brown, with the second half of the op-amp package buffering a 1k levelling pot. I ran it off two 9V batteries for a positive and negative rail. The op-amp drove a Jensen output transformer for a balanced XLR output. The input side had a couple of ferrites, protection diodes and a few switchable resistors on the input to select the input load impedance. I crammed it all into one of those MXR size aluminium boxes. The box has 4 toggle switches, a power switch, a power LED, an output level knob, a 1/4" input, a 1/4" pre-transformer output, and a post-transformer balanced XLR output. Pretty much built it in a couple of hours including drilling out the enclosure.
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