sqrt 2=>3dB, not 1.4. 1.414 =sqrt 2.

Le 14/02/2025 à 00:45, Casey via groups.io a écrit?:

Others will correct me if wrong, but based on what I've read here about this:

With Simplest P48 (capsule + resistor + capacitor) you can indeed parallel the capsules. You use a single resistor/capacitor set, but you cut the resistor value in half for two capsules, to 1/3rd for three capsules, etc.

You can apparently also parallel the entire SP48 circuit off the XLR, which someone suggested might be better for 3 or more capsules.

My notes say "Could theoretically power ~14 in parallel, but CMRR degrades with each capsule (because SP48 loads only one of the 6.81k resistors used in phantom); "in the real world you should be OK putting three or four P48's in parallel" "

Someone on this list (sorry for lack of attribution) also said "Doubling the number of capsules can improve your SNR by 1/sqrt(2). So going from 1->2 improves things by that much. Going from 2->4 does so again. Going from 4->8 does so again. But that's where things get a little iffy. 2 capsules arranged vertically mostly works because most sources are going to be in the plane of the mic so you won't get much in the way of comb filtering between the capsules. By the time you've crammed eight capsules into one spot, it's going to start having a noticeable effect. Also, if you look at what 1/sqrt(2) looks like in dB, it's tiny. It's about a 1.4dB improvement in SNR. I don't know how tight the tolerances are on the Primo or PUI capsules, but you may be able to better that by just picking the best of a batch and using those as single capsules per channel."

There are other considerations, but that about sums it up. :-)

-c

On 2/13/25 15:31, Cram via groups.io wrote:

Hi all,?

First post on here - I've done a search through the group but couldn't find a definitive answer.

I've been mucking around lately with aom5024 capsules to go along with the clippy mics that I have, and have been quite happy with their performance. I've got some as PIP, and I've built some into XLR plugs using the simple p48 circuit to use with a zoom h5, and these also work a treat.

I've seen a few mentions online about the merits of running two or more capsules in parallel, and would like to try this myself. Seems fairly straightforward with the PIP examples online, however I've been overthinking it in regards to the phantom power XLR connection and am now double guessing myself.

My question is:

1) can I use the the same p48 circuit I used for a single capsule, and just wire two capsules in parallel

2) do I do #1 but adjust the cap/resistor values to accommodate the multiple capsules

3) does each capsule require its own resistor/cap?

Thanks in advance guys :)? ??