Rode NT5 circuit

[LevinGuitar]

I was curious about the circuit of the Rode NT5. Here are some pics and measurements:

Main stabilized voltage 15v
Capsule polarization -71.7v

Fet (450) bias
Source 8.6v
Gate 5.4v
Drain 14.6v

Voltage between 150uf 16v capacitor pins: 15.4v
Voltage between 22uf 63v capacitor pins: 24v, 32v
Capacitors dimensions: 11.5x6mm


It seems similar to NT1A circuit except for the negative polarization (why?) and the grounded diaphragm with the backplate-gate imput cap.
I guess there could be some "voicing" tuning with better output caps, some should fit since there are a bit of room for them (2x2mm more? and 50v voltage rating) . Also I could try a different imput cap.
I wonder if the small voltage rating margin is something to be worried about in the 150uf 16v caps.

The dissasembly is a bit weird but easy:

1 Unscrew the XLR retaining screw (counterclockwise to loosen)
2 Pull out the XLR
3 Unscrew the main pcb
4 Pull out the PCB (fitting back the XLR)

 

[kingkorg]

It seems similar to NT1A circuit except for the negative polarization (why?)

According to Doug Ford someone at Rode had a preference that positive pressure on diaphragm gives positive voltage at the output.

 

[Khron]

According to Doug Ford someone at Rode had a preference that positive pressure on diaphragm gives positive voltage at the output.

That's pretty much the standard, actually. I guess that's what they needed to do, while keeping the circuit simple (ie. without needing to add another stage to invert the signal, AND not having pin 3 "hot", as opposed to the more usual pin 2)..?

 

[LevinGuitar]

According to Doug Ford someone at Rode had a preference that positive pressure on diaphragm gives positive voltage at the output.

I don't get it. Is phase what you mean?

 

[kingkorg]

I don't get it. Is phase what you mean?

Well basically yes, they could have avoided that by flipping the phase at XLR, but as Khron described you would have the pin 3 as hot, which is not a standard. All of this has no impact on performance, we believe it's just complying to standards.

 

[LevinGuitar]

Btw there is capsule backplate hole pattern image in the box

 

[ricardo]

Did you trace out the circuit?

 

[LevinGuitar]

Did you trace out the circuit?

Well, I tried today using the NT1a draw schematic I found here. It may have some mistakes, and I did not corrected the voltage amp part at all

 

[LevinGuitar]

Well, the biggest caps that would fit the body are 8×11.5mm size as the Nichicon FG 47uf 50v are. Did they made a big change? I wouldn't say so, the Wima FKP 1000pf for the imput cap was a "bigger" improvement but this is also somewhat subjective. There are still definately some brightness to get rid of.

 

[Khron]

There are still definately some brightness to get rid of.

I seriously doubt either of those capacitors could've / would've done anything about any "brightness"...

 

[LevinGuitar]

Best and easiest mod: elastic band over the vents! Now it sound completly different in a better way.

Don't know if it's close to the NT-45 O capsule response and polar pattern, but definately worth to try

 

[Rnelson50]

Well, the biggest caps that would fit the body are 8×11.5mm size as the Nichicon FG 47uf 50v are. Did they made a big change? I wouldn't say so, the Wima FKP 1000pf for the imput cap was a "bigger" improvement but this is also somewhat subjective. There are still definately some brightness to get rid of.

The higher value caps are strictly power supply filtering. The pair feeding the output wouldn't affect HF (larger values pass LF better but wouldn't affect HF or resonance issues) so increasing those uF values might extend the LF end.

 

[LevinGuitar]

I had that idea in mind, but was hoping that extending low end would compensate somewhat the brigthtness, but it did almost nothing. But the vents help a lot with it. I should find the omni capsule and see if it's even better

The higher value caps are strictly power supply filtering. The pair feeding the output wouldn't affect HF (larger values pass LF better but wouldn't affect HF or resonance issues) so increasing those uF values might extend the LF end.

 

[Rnelson50]

As you found it probably didn't do anything for the low I presume the caps were already large enough to cover the actual LF range. Manipulating ports will affect response and/or pattern but usually not in a good way. some of the non-electrolytic caps no doubt will affect HF rolloff, but I don't really see anything that is designed to handle specific peaks.

 

[Soundmatters]

I had that idea in mind, but was hoping that extending low end would compensate somewhat the brigthtness, but it did almost nothing. But the vents help a lot with it. I should find the omni capsule and see if it's even better

I have a pair of NT55s, and yes, the omni capsule sounds a lot nicer than the cardioid, with a much better low end response, which is why I use them all the time, despite the fact they pick up all the room noise with that capsule. Looking at what you've done though, and my capsules, perhaps the only difference is the lack of slots??

 

[LevinGuitar]

I have a pair of NT55s, and yes, the omni capsule sounds a lot nicer than the cardioid, with a much better low end response, which is why I use them all the time, despite the fact they pick up all the room noise with that capsule. Looking at what you've done though, and my capsules, perhaps the only difference is the lack of slots??

If you have both capsules (omni and cardioid), do the experiment with the cardioid and let us know if it sound close to the omni

 

[Soundmatters]

If you have both capsules (omni and cardioid), do the experiment with the cardioid and let us know if it sound close to the omni

Yeah, good idea

 

[Soundmatters]

I didn't have any elastic bands, so I tried it with some tape covering the vents and it doesn't sound as open as my omni capsule. The capsules look identical from the top, but they are different in other ways besides the vents as well, see attached pics of the capsule rears, omni on the Left.

 

[WingedFuse]

Hi! Do you know how Rode is pairing two microphone ? And if you change the capsules for omnidirectional ones on a pair of NT5, would have to match them after ?

I want to build a binaural microphone (a dummy head one like the Neumann KU100) using two NT5 omnidirectional capsules. I will make my own pcb and wonder if I could make some improvements on Rode's circuit to get the best sound quality.