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Post by basspro on May 24, 2024 12:44:49 GMT -6
I've always just committed compression/eq to tape while recording vocals and while it's usually totally fine, I occasionally will have a take where I wish I had a safety net.
I'm wanting to commit as usual, but use a half-normalled patchbay point to also record a dry copy. Is there anything to be worried about concerning impedance when you split a signal like this?
Would also like to try this for parallel compression on drums while tracking. I'm always looking to get as finished a sound as possible while recording, so as long as there are no impedance issues to worry about, this just might become a new workflow for me.
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Post by EmRR on May 24, 2024 13:16:04 GMT -6
If the 2 devices are same Z, Z is now 1/2. Usually fine, the point of bridging theory.
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Post by thirdeye on May 31, 2024 6:19:16 GMT -6
I've always just committed compression/eq to tape while recording vocals and while it's usually totally fine, I occasionally will have a take where I wish I had a safety net. I'm wanting to commit as usual, but use a half-normalled patchbay point to also record a dry copy. Is there anything to be worried about concerning impedance when you split a signal like this? Would also like to try this for parallel compression on drums while tracking. I'm always looking to get as finished a sound as possible while recording, so as long as there are no impedance issues to worry about, this just might become a new workflow for me. This is a great way to set up a patchbay. I've never had a sound degradation issue using this method. All of our mic preamps are half normalled. If you can have dedicated separate converters for your outboard and preamps, you can track the "dry/wet" right next to each other and have a "safety net" in case you over bake the processed signal on the way in. It's a great way to experiment as well - example, mult the vocal to a couple different compressors, record the 1 dry, 2 wet, and pick the best chain (or use both-Ha!). Workflow wise, it can be bit cumbersome (always having the multiple tracks grouped for punch ins, edits, etc.) but can be worth it. |
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Post by svart on May 31, 2024 7:47:36 GMT -6
Impedance matching has two reasons for use.
1: long transmission lines will have reflections of the electrical current, just like waves in the bathtub or sound reflecting off a wall. Impedance matching acts to reduce those reflections by sinking the current that would normally reflect backwards. This is why you have "75 ohm" or "50 ohm" cables which have identical impedances on either end.
2: Currents that are transmitted can be affected by the mismatch between source and load impedances and you can have voltage gain or loss that differs from power gain/loss. This can result in drastically different signal levels than you'd expect. For instance, a 600 ohm mic output is fed into a 600 ohm preamp input, the resulting signal will be 50% of what the source supplied which is 6dB of loss. If you have a 600 ohm mic output that is split and feeds parallel 600 ohm preamp inputs that now have a combined parallel impedance of 300 ohms. 600 ohms feeding 300 ohms will result in a loss of 66.6% or 9.5dB.
Which is why in audio, mics ACTUALLY have very low output impedances of around 100-200 ohms and preamps typically have impedances in the 10x range. 10x source to load impedance mismatch leads to the highest amounts of voltage transfer. A 100 ohm mic output into 1000 ohm preamp input would be around 1dB of loss. A 100 ohm mic into parallel connected 1000 ohm preamp inputs that have a resulting apparent impedance of 500 ohms would result in about 1.5dB of loss.
A well shielded cable shouldn't really need to worry about #1 in a studio application, so really it's all about maintaining signal level with #2.
So that's about it. A mic that's split into two average preamp inputs will lose about 1.5dB of signal. Unless you have hundreds to thousands of feet of cable in a noisy environment, you'll rarely have to worry about other kinds of transmission line issues.
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