Battery in the signal path

[Grapestomper]

I'm one of the many lurking learners here, and as part of my self-education I've been I've been going through the circuits of all the mics I actually own to see what I can learn.

I have a set of Nakamichi CM-300 small diaphragm battery powered electret SDCs, which have a very simple circuit that you can see about two thirds of the way down this page:

https://audiomods.datsunzgarage.us/cm300/

It's obvious from the diagram (and also just looking at the microphone) that the battery is in the signal path, and my question is this: is battery chemistry likely to influence the sound?

These mics originally came with a 9V mercury cell, which is now (rightly) unobtanium (and also a hazmat issue). I'm using them with a stack of 3V "dog collar" batteries, which I think are Lithium based, but there is also an alkaline cell available online for around $20.

Does anyone here know if battery chemistry a factor at all?

(I guess I could just pony up for the alkaline cell and do the experiment for myself, but I'm hesitant to spend on these mics, as I don't use them often.)

M

 

[k brown]

I was always VERY curious about that too; when I first saw that schem, I thought: "Can this be right?".

 

[Rusan]

I played in a band with a singer who had an EV BK-1, with a battery that looked just like the 206 9V but it was 4.5V. It burned through 'em like water, and got expensive in a hurry. They had a powered head without P48, that we replaced with an entire new PA soon after I joined. None of us heard any difference when powering it with P48 versus the battery, including him.

There are many guitar players who swear they can hear a difference between 9V battery brands in their pedals, and a huge difference between battery power and wall wart/power brick AC adapters. I guess I don't hear what they're hearing, because it all sounds exactly the same to me.

I once read that NiCd cells have lower internal impedance than NiMH cells, which makes them superior for cathode biasing of vacuum tubes. In the case of the microphone, a few ohms difference would of course be meaningless in series with the drain of a JFET, but there might well be some non-linearities inherit to certain cell chemistries. It would be something interesting to test.

 

[k brown]

There are many guitar players that swear they can hear the difference between different 9V battery brands in their pedals, and a huge difference between battery power and wall wart/power brick AC adapters. I guess I don't hear what they're hearing, because they all sound exactly the same to me.

I once read that NiCd cells have lower internal impedance than NiMH cells, which makes them superior for cathode biasing of vacuum tubes. In the case of the microphone, a few ohms difference would of course be meaningless in series with the drain of a JFET, but there might well be some non-linearities inherit to certain cell chemistries. It would be something interesting to test.

The question is about a circuit where the audio actually passes through the battery.

 

[Rusan]

The question is about a circuit where the audio actually passes through the battery.

I realize that, hence, "In the case of the microphone, a few ohms difference would of course be meaningless in series with the drain of a JFET, but there might well be some non-linearities inherit to certain cell chemistries." I meant to convey that even though I myself never heard a difference, if some say they can clearly hear a difference between different battery brands and external power sources, then there certainly may well indeed be significant sonic differences when said batteries are actually in the direct AC signal path. As in, "NiCd cells have lower internal impedance than NiMH cells, which makes them superior for cathode biasing of vacuum tubes," due to a lower impedance AC ground.

Sorry, I should've worded my syntax a little more orderly.

 

[rock soderstrom]

I was always VERY curious about that too; when I first saw that schem, I thought: "Can this be right?".

+1, same here.