Rode NT1 Kit (the black one) Mods

[dima_k85]

Rode have certainly taken some design decisions that require their circuit to be more complex than is strictly necessary.
I'm sure they'll have had their reasons for doing that...

The RODE solution has lower noise.

Not according the Rode themselves....

The HF6 capsule was developed especially for the new (black) NT1, which was released some time after the NT1-A.

See here: http://www.rode.com/microphones/nt1

Have you seen them yourself? They are absolutely the same.

 

[rogs]

The RODE solution has lower noise.

I don't think you'll find the low noise features of the Rode are specifically related related to the bias voltage multiplier. As I mentioned earlier the simple version I described has an output noise ripple (at 125KHz!) of c.3mV P-P on top of the 60V DC bias voltage.  That's a noise voltage (with a fundamental frequency of 125KHz) at around -86dB  below the 60V boas voltage.... Not really a contributory noise factor, I would suggest?..

Have you seen them yourself? They are absolutely the same.

Here's Rode's own words on the subject, from the page I linked to above:

"Although the body of the new NT1 closely resembles the NT1-A, the microphone has been completely redesigned from the ground up, with the only shared component being the mesh grille".

 

[kingkorg]

Nope, the capsule is definitely not the same, different spacers inside, different damping. This is the only current low cost mic capsule that is produced on their latest production line used for Faulkner mics.

The capsule is responsible for 0.5db better snr and the reason i wanted to go even further. Which i am glad i did

Some improvements might come from layout, better component matching. But that is hypothetical.

 

[dima_k85]

I don't think you'll find the low noise features of the Rode are specifically related related to the bias voltage multiplier. As I mentioned earlier the simple version I described has an output noise ripple (at 125KHz!) of c.3mV P-P on top of the 60V DC bias voltage.  That's a noise voltage (with a fundamental frequency of 125KHz) at around -86dB  below the 60V boas voltage.... Not really a contributory noise factor, I would suggest?..

Look at spectral analysis, not ripple.

Nope, the capsule is definitely not the same, different spacers inside, different damping.

Did you measure the thickness of the spacers yourself? What is it for NT1 and NT1-A?

 

[rogs]

Look at spectral analysis, not ripple.

With the fundamental oscillator frequency over 2 octaves higher than the audio spectrum, I'm not sure what you mean here? -- Are you suggesting measuring sub-fundamental noise content from the voltage multiplier? 
I have to confess I wouldn't know how to do that.  (I can't actually hear or measure any noise from the multiplier)

In practice, my LDCX2 sample builds have proven to be pretty quiet.  Not as quiet a reference noise floor as my Rode NT1, but as they tend to have higher sensitivity capsules - and thus require less preamp gain than the Rode - the end result is that the actual noise level ends up about about the same.

 

[dima_k85]

With the fundamental oscillator frequency over 2 octaves higher than the audio spectrum, I'm not sure what you mean here?

The amplifier is not limited to just the audio spectrum.
Processing of high frequency overtones goes much further, very, very far.

 

[kingkorg]

- Are you suggesting measuring sub-fundamental noise content from the voltage multiplier? 

Please, please don't go there! Unless there are some concrete measurements to publish?

I would love to keep this thread as concise and empirical as possible. That's why i started with measurements and only backed up facts. Please let's not step into audiofool territory, as it will end with the usual "Rode mics suck, and will never sound as a vintage mic".

Let's approach it as if we are modding a measurement tool.

 

[kingkorg]

Ok, the mic has been on for 24 hours, 100v polarization voltage, no issues whatsoever.

I compared the noise level, and it is quieter than stock, but both are so low in noise that i have no idea what i'd use them on for such quiet sources. I mean, the test was done in a dead vocal booth, no sound to speak of, yet i was able to hear everything else but noise. To hear any trace of noise on both i had to boost high end +30db, and then i could compare.

Next on the list is tho check the surroundings of the capsule, and see if any acoustical improvement can be done.

The capsule capacitance is 88pF if anyone is interrested.

 

[rogs]

The capsule capacitance is 88pF if anyone is interrested.

Interesting ... seems a typical value for an edge terminated capsule in my experience - and higher than most centre terminated capsules (typically around 65pF, I've found) .

Sound like an ideal  candidate for my RF bias mic ....  Not sure I have the confidence to take the capsule out of my NT1 to try though? ...
( I don't think doing that would help my 10 year Rode warranty any! )

 

[kingkorg]

If you decide to do it, dont unsolder the wire from the pcb, solder points are protected with some kind of clear coat. Not sure if soldering, unsoldering might affect noise if things get messy there.

Rather unscrew the wires at the capsule, and use another pair of wires for your mic. If you do it carefully, no one will ever know

 

[kingkorg]

I added some foam under the capsule, and that smoothed high end and upper midrange as expected. I would suggest this mod to just about any mic.

If you go this route make sure the foam doasn't touch connections or the front ring. If the sponge gets damp it will start conducting and start making noise, but will go away when foam dries out. The dip at 7.5 khz is caused by the grille. I you want to get rid if that one you need a different grille.

I found an error on the schematic. 0.047 cap at Q1 is 100pF. And 0.047 across D4 diodes and 1k resistor is 5nF.

The response

 

[dima_k85]

And 0.047 across D4 diodes and 1k resistor is 5nF.

Too little, there must be more.

 

[kingkorg]

Did you join the forum just to troll this thread? Please don't do that. The capacitor is of this value, i measured it my self.

No problem with low humidity, start using it when recording voice and problems may appear.
The membrane may be electrically breakdowned.

This is not true. The membrane is edge terminated, so humidity from the breath can not conduct between  cathode and anode. You can spit directly into it, and it will still work. Please stop doing this.

 

[dima_k85]

Did you join the forum just to troll this thread? Please don't do that. The capacitor is of this value, i measured it my self.

This is not true. The membrane is edge terminated, so humidity from the breath can not conduct between  cathode and anode. You can spit directly into it, and it will still work. Please stop doing this.

You are very funny. You do not understand anything either in amplifier circuitry or in elementary physics.
You cannot even understand that I am writing not about what is, but about how it should be.

Keep spitting into your microphone.

 

[dima_k85]

Rode amplifiers are wonderful designs and their capsules are the worst.

The best mod I have found for any of their mics has been to replace the capsule with a decent one.

I would not say that RODE amplifiers are well designed. A lot of nuances are not taken into account. Especially in the PCB layout.
AKG design is much better.

What exactly do you dislike about RODE capsules?

 

[Tim Campbell]

AKG design is much better.

Hahaha obviously you haven't worked on any C414 models. Their mechanical layout creates so many problems.
The switches are a nightmare as well as dirty pcb's, fragile frame assemblies. Most of their really great mics are so overcomplicated and fragile.

 

[kingkorg]

The best mod I have found for any of their mics has been to replace the capsule with a decent one.

This capsule isn't winning any contests any time soon, but seems to be most neutral out of all previous iterations.

I had to post this one for those who believe Rode's and similar edge terminated capsules resemble even closely true CK12. And since Tim chimed in, here's NT1 against C12 i built with Tim's capsule, and transparent headbasket. Other capsules like RK12, CK12 from 797... measure similarly to NT1, but are a db or two brighter. All have the same shape which is far from what they are trying to emulate.

Red NT1
Black CK12

 

[rogs]

Their backplate/phase network is just a rip off of bad chinese designs. Their 70v polarisation voltage means compromises have to be made to the membrane/backplate relationship in order to keep them from collapsing. Their designs of capsule mounts are the worst, just laughable.

Many years ago I had discussions with Rode about designing some capsules for them and they were in total denial that their was anything wrong with their capsules. They are typical electronic oriented engineers and seem to see the capsule as just a capacitor, which if the specs are right, for the right price, work properly

I have to say I think these comments are perhaps a little harsh?....
I've been quite pleased with my Rode NT1 (2014 'black' model with the HF6 capsule), and have certainly found it better - especially HF wise - than my selection of various 'Chinese' 34mm LDC capsules.

I think most folk would agree the difference between the Rode NT1, and the famous Neumann U47 is not worth an extra £7500!   ..
I think the Rode stands up pretty well?..

https://www.youtube.com/watch?v=VnrXFC5Pyhs

 

[RuudNL]

Did you notice that the video with the comparison was made by Røde?...

 

[rogs]

Did you notice that the video with the comparison was made by Røde?...

Yes, I did notice -  but as the test conditions are a direct comparison, using identical channel inputs, it seems a reasonable test set up?
I'm guessing they set it up to see how they compared,  and then decided whether the results were good enough to publish? 
If they hadn't been good enough - they simply wouldn't have posted the video!

I suppose they may have 'cheated', somehow?  - although for a reputable company to take the risk of any 'cheat' being revealed later on, I can't see why they would take that chance.... They didn't have to post this clip...
My guess is that Rode may have been a bit surprised themselves at just how well their mic performed