Noob Question: Circuit design for low self noise, what principles are important?

[AUDIO FREQ]

I've been looking at the Neumann TLM 103 circuit, and was wandering how they achieved such a low self noise from this design? The circuit board seems very minimalistic. I've read it's made from ceramic, in lieu of FR4 which is common?

Also that some of the components are laser etched in, I believe the resistors? Do these factor into the low self noise principle?

IMSAI guy says that the design is very similar, if not identical to the Rode NT1 design, and they both achieve very low self noise, but the TLM103 seems to be extremely sensitive also. MCould that be due to the capsule?

Thanks for the education guys!

 

[Екатерина]

This circuit has always been very quiet, and the impact of the circuit board material should be minimal. The reason for the capsule should also be a part of it. I believe they have adopted customized low noise components with good shielding

 

[Voyager10]

A few things to consider:

• Sensitivity of the capsule itself
• Bias voltage for the capsule (e.g. recordinghacks reports the NT1-A has a +75V polarisation voltage; not all capsules tolerate this!)
• Choice of FET (low inherent noise, and also low input capacitance so signal is not attenuated)
• Biasing of FET (the data sheet may show how noise figure varies with operating currents & voltages)

 

[Khron]

(e.g. recordinghacks reports the NT1-A has a +75V polarisation voltage; not all capsules tolerate this!)

The output of the DC/DC converter relative to ground, yes. But the other side of the capsule is NOT at ground potential (but 6V or so above ground), so there's not quite 75V across the capsule. Just saying...

 

[AUDIO FREQ]

JLI electronics says 80v! I think im gonna insert the 10k pot and trim it down to 60v.

 

[kingkorg]

I've been looking at the Neumann TLM 103 circuit, and was wandering how they achieved such a low self noise from this design? The circuit board seems very minimalistic. I've read it's made from ceramic, in lieu of FR4 which is common?

Also that some of the components are laser etched in, I believe the resistors? Do these factor into the low self noise principle?

IMSAI guy says that the design is very similar, if not identical to the Rode NT1 design, and they both achieve very low self noise, but the TLM103 seems to be extremely sensitive also. MCould that be due to the capsule?

Thanks for the education guys!

A few things to consider:

• Sensitivity of the capsule itself
• Bias voltage for the capsule (e.g. recordinghacks reports the NT1-A has a +75V polarisation voltage; not all capsules tolerate this!)
• Choice of FET (low inherent noise, and also low input capacitance so signal is not attenuated)
• Biasing of FET (the data sheet may show how noise figure varies with operating currents & voltages)

In case of NT1 bootstrap FET to negate it's input capacitance. NT1 fet doesn't have low input capacitance. Also PCB layout.