Question about Samson C01

Hi everyone !

I'd like to know if some of you knows about the possibilty to apply modifications to improve this microphone.

I know these mic's are really cheap and that's why they sound so cheap too

Playing on response pattern (cardioïd, 8, ...) seems quiet easy with tube microphones, you just need to play on the polarity of the capsule. What about this knid of microphones ?

I don't think there is anything you can do to change to pickup pattern. the capsule might be ok if it's the same as the MXL99x stuff, but i bet the electronics are cheap, cheap cheap. upgrading the FET(s), caps and resistors will help but it's lilke putting a bandaid on a bleeding stump.. it's be better but how much is the question.. let your ears make the decision!

:thumb:

I have worked on a few. The problem with the microphone is that the electret capsule has high noise IMO. I have upgraded caps and changed the fet and a transistor the noise stayed.

I bought two for fun/modding thinking it could be a cheaper AT4033 with a simpler circuit. Sometime you get what you pay for.

It is a more hypercardiod pattern I believe.

Not much to do with that microphone IMO. The stuff I did made little difference.

If the capsule is good, I could only change the electronic of the body. I'm pretty sure that some of you here have already done a small and efficient mic' preamp

EDIT: after reading your post Gus, I'll try to get one for a few nuts and play with it ... I mean with its electronic

What is IMO standing for ? It must be some kind of Internal Noise of the capsule but I'm not sure ...

IMO in my opinon. I don't think the circuit design is the problem. I don't like the noise level from the capsule.

There's something I don't understand: capsules are passive really high impedance devices so how an they make so much noise ?

Gus > did you take the time to note the schematic of the electronic ?

Looks like a standard circuit. I am not going to waste my time tracing it, it is not worth working on IMO.

OK, thanks for your replies anyway

> capsules are passive really high impedance devices so how an they make so much noise?

Well, in most audio, high impedance means high noise voltage. Take a common XLR mike preamp. Take three XLR plugs. On one, short the two live pins together; on another solder a 300 ohm resistor across, third plug use a 100K resistor. Put on the 300 ohm plug and crank the gain to hear hiss. Mute, put on the shorted plug, un-mute. Hiss is probably less. Mute, 100K, un-mute: hiss is probably very high. (There are some preamps that will confound this test.)

However when you get into a complete capacitor mike and its onboard preamp and acoustic damping, it gets complicated. On JFET preamps you want a super high gate resistor so the capsule capacitance swamps it. Tubes often can't use such high grid resistors because their grid current noise is significant. But the real confuser is: stretched diaphragms ring badly. The usual fix is a large amount of acoustic resistance (small slits or holes). Same as an electric resistance, an acoustic resistance has a noise power, and the capsule makes noise even if you have a noiseless preamp.

So I'm guessing this capsule has an unhappy amount of acoustic damping. But it could also have dirty or contaminated insulation.

Thanks for this clear explanation PRR. But an other question comes to me:
high impedance means high equivalent noise.

If my memory is good, noise is proportionnal to the value of the resistance, something like
"noise = k*T*delta_f*R"
with k = Boltzmann constant, T the temperature, delta_f the band frequency and R the value of the resistance.

So my question is: why do we use high impedance input circuits such as with FET or valves if they are so noisy ?

An answer could be "because audio devices are voltage controled, that's why we use low ouptut impedance and high input impedance". But it won't solve the noise problem

Preamp input impedance is pretty much dictated by the output of the transducer we want to connect to it; generally, it should be ten times or more the output impedance of the transducer. So, with a typical dynamic mic having a source impedance of 150-200 ohms, a mic preamp would have an input impedance of 1500-2000 ohms, an electric guitar preamp would have an input impedance of several hundred Kohms, several Megohms for a piezo pickup, and so on. The application dictates the sort of devices used in the input stage. The best we can do is to try to optimize the other parameters of the stage while fulfilling that primary requirement.

Inside of a system, where the designer has some measure of control over both source and input impedances, it's a balancing act between noise and power consumption, heat, etc. A mixing console can be designed for rather low internal buss impedances, for lower noise, but you'll pay a price in heat and power consumption, reduced headroom, etc. It's a matter of tradeoffs and careful choices.

[quote author="slash14"]
So my question is: why do we use high impedance input circuits such as with FET or valves if they are so noisy ?
[/quote]
My own simplistic way of looking at it, in the case on condenser mics, is that the current produced by the condenser's capacitance change (in response to acoustic waves) is so small that it has to go into an extremely high impedance to produce a measurable or useful voltage.

E=IR.