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Old 02-28-2017, 11:34 AM   #7
karbomusic
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Originally Posted by Judders View Post
Hey, you know far more about the guts of stuff than me, just wondering what your thoughts on the below are:

"Do passive DI's present a different load to a guitar or bass as opposed to active DI's?
Our fellow member ashcat is going to know far more than I but I can offer a couple tidbits. I think 130k is a little low for 2017 but that depends more on what is plugged in so in many ways it is perfectly sufficient. Typically the rule is that the target device's impedance (the DI in this case) should be 10 to 100 times higher than the source impedance (the guitar). Most guitars fall in that 5-10k range IIRC so you can sort of see we are within but close to the 10 times number.

Many modern pedals, at least DIY ones use 1-10 Megaohms to ensure there simply isn't a source impedance high enough to cause any frequency losses. That being said, when I stated insertion loss above I meant loss of dB level not really loss of fidelity.

Another tidbit about transformers, they will pick the crap up out of hum. Thusly to make one that can cover 20-20K and be properly shielded (using MU metal etc.) they can be extremely expensive to manufacture, this is precisely why Jensens (and Radial) cost so much so that isn't a scam, it's just a byproduct of the technology. That's also why Radial DIs have that very thick folded metal enclosure.

All that being said, a true DI is for converting an unbalanced signal to a balanced signal, if that isn't needed then you can achieve the same with any input circuit/buffer that has sufficiently high impedance. Many conflate DI as in plugging a guitar directly in with the conversion to balanced, it's a nitpick but I like calling DIs the ones that actually do the conversion and the ones that don't buffers or similar.

Last edited by karbomusic; 02-28-2017 at 12:13 PM.
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