Topic: Simple Nak cm300 Mod

[leegeddy]

marc - thanks for entertaining all the nit pickly questions...

Another source of my confusion was the schematic - I was looking at the after-mod version as if that was an XLR  - and I would just hook it up, turn on the Phantom and everything would be hunky dory...now I see - the rest of the story is in the AT8533...

Question 2 - is there a transformer in the Nak body? - in the before-mod schematic - that spring-looking thing that connects to pin 2 and 3 - is that the stock transformer...?

yep. the post-mod schematic only shows the capsule assembly. (i originally was going to use a mini-xlrm for the output).

that is a transformer you see in the original body, and it's stock in all cm300s.

marc

[jk labs]

I just re-read leegeddys original post - my confusion is stemming from not knowing what the AT8533 modules do.
he says:
i purchased Andy's (dwonk) CM300 pair last month and after few discussions with Audio Technica's tech about the specs of the AT8533 9-52v power modules,
I think the hyphen threw me...Ok - I get it...the leegeddy mod runs on 9V.

the part that I don't understand is, why does the mod make the mics sound different?  is 9v of phantom power different than 9v of power from the battery?  it must be, but i don't understand how/why.
isn't 9 volts of power, just that? 9 volts of power ? 

You're on the right track :-)
 
9 Volts IS 9 Volts. However, no power source is just 9 Volts DC. It's 9 volts DC + noise. Noise can be small, large, white, pink, 60Hz, 100kHz..... i.e it is made up of truly random broadband noise and _signal_ like components.   

The noise as defined above, is of AC nature by definition (we split all DC off into the "9V") . As such it leaks into the audio signal in many ways. Part of the noise is in the audioband and is audible directly. Other components become audible thought analog processes like modulation, rectification etc. And some frequencies leak through the ADC and are mapped down into the audio band by the sampling process itself.

This is a very brief look at a complex issue.

For completeness though: There is another parameter of equal importance and that is the internal resistance.   
Will the supply remain at 9 Volts when current is drawn? And the answer is no. Current is drawn to develop a signal.
So the current varies with the audio signal. So now suddenly, we have a noisy DC source supplying a voltage
that varies with the audio signal. In many circuits such signal variations in the supply will give rise to harmonic distortion. 

So to conclude: "9 Volts" is never 9 Volts. 


Just to be crystall clear - I do not offer this as an explanation for any differences, real or imagined, in the sound of Lee's Franken modded CM300s.  The changes Lee does to the circuitry itself are drastic enough to be the sole reason.

Jon