Sony C100 circuit

[AUDIO FREQ]

Great sound but it has high self noise for my liking.

Here is a pic of the circuit if anyone is curious.

EDIT: Reverse sides of circuit.

 

[kags]

Just curious as to what mics would be quieter than this? I used the C100 extensively and found its self-noise in actual use to be comparable to U87, c414s, KM84s, and other common studio mics. I didn’t compare it directly to our Schoeps or MKH mics, but the Sony isn’t meant to be in that league.

Respectfully, I’m not saying there isn’t room for improvement- just wondering what your expectations for this mic might be.

 

[AUDIO FREQ]

Just curious as to what mics would be quieter than this? I used the C100 extensively and found its self-noise in actual use to be comparable to U87, c414s, KM84s, and other common studio mics. I didn’t compare it directly to our Schoeps or MKH mics, but the Sony isn’t meant to be in that league.

Respectfully, I’m not saying there isn’t room for improvement- just wondering what your expectations for this mic might be.

Hello,

Checking out the spec sheets for other mics, there are quite a few mics that are quieter. For instance the U87AI is quieter, TLM103, NT1, NT1A, and even tube mics like the C800g is quieter by a dB...

the C100 has an equivalent 19dB self noise in cardioid. For a fet mic, it seems a tad high in my opinion. In use, I noticed when boosting gain in the Apollo preamp, the mic starts to emit a white noise-ish self noise.

But who knows, maybe I have a dud?

 

[AUDIO FREQ]

Update, found the service manual if anyone is in need.

 

[Voyager10]

That's rather a quirky circuit. Looks like they have an LDC capsule feeding XLR pin 2 and an SDC feeding pin 3 (via a high pass filter). Combining the two happens in the preamp.

I'd suspect most of the noise comes from R152 in the LDC's impedance converter, that's 4.7k's worth of thermal noise right in the signal path. Seems sloppy to me - I wonder how it ended up like that?

 

[OneRoomStudio]

Update, found the service manual if anyone is in need.

Where’d you find the service manual? It would be interesting to get ahold of the C80 service manual to see if they used a similar circuit.

 

[emrr]

In use, I noticed when boosting gain in the Apollo preamp, the mic starts to emit a white noise-ish self noise.

You have verified the noise isn't the preamp by strapping an input resistance, such as a standard mic pad? Tried a different preamp channel? Different preamp?

 

[SubSpec]

I would concur on the noise, my experience with the C100 was similar. The best single mic acoustic guitar sound I've gotten, but it does have a more noticable noise floor than most of my mics.

 

[AUDIO FREQ]

That's rather a quirky circuit. Looks like they have an LDC capsule feeding XLR pin 2 and an SDC feeding pin 3 (via a high pass filter). Combining the two happens in the preamp.

I'd suspect most of the noise comes from R152 in the LDC's impedance converter, that's 4.7k's worth of thermal noise right in the signal path. Seems sloppy to me - I wonder how it ended up like that?

Any ideas to modify it for lower noise? How would you have designed the impedance converter, lower resistance at R152?

You have verified the noise isn't the preamp by strapping an input resistance, such as a standard mic pad? Tried a different preamp channel? Different preamp?

It comes with a pad. And yes i've engaged the pad on it as well as other patterns just to experiment. I use a plethora of different mics, and noticed the C100 is noisier. The spec sheets says 19db of self noise, and yes I have tried it on other pre-amps aside from the preamp in the Apollo Twin X and Apollo Twin X6. I have tried it on Focusrite 18i20 and Presonus Eureka with Jensen Transformer.

 

[emrr]

Not the pad on the mic. Using a pad as a way to load the preamp with no mic attached, evaluate its noise.

I personally can’t say I ever have problems with mic noise in the real world, nor with preamps of which I use a lot of antique technically noisy tube types, unless the source levels are so small as to suggest the wrong mic or preamp is being used for the job. Usually the rare noise problem is asking a ribbon and a high gain tube pre to do more than is reasonable for the situation. Air motion alone is usually the overriding noise source, swamping all else, outside of any hum fault.

It’s very easy to look for noise problems in a vacuum and find them, then use the same equipment on a recording job and hear none. I’ve been down that road numerous times.

Haven’t used this mic, but like poster #2, am skeptical that Sony would release a mic like this with a questionable noise floor. There’s plenty of recommendations for it from classical recordists, ambient usage as the S in MS, etc. It wouldn’t fly if considered noisy by those users. Maybe there are faulty samples out there. I’d certainly dig into that further.

 

[Voyager10]

Any ideas to modify it for lower noise? How would you have designed the impedance converter, lower resistance at R152?

You could lower R152 to 2K2, but this would also increase the gain of this stage, which would alter the balance between the LDC capsule and the HF one, and change the sound of the mic. You may be able to re-balance it by reducing R102 and/or increasing R104 in the HF amp, but this would need careful measurements in order to get it right.

One alternative would be to use a 'charge amplifier' arrangement, like the U87 and KM84. For this, there's a big (e.g. 22uF) bypass capacitor across the R152 position, and a small feedback capacitor (typically 3-10pF) is put between Q151 drain and gate to set the gain. This capacitor value is critical to success, so if it were me I'd want to measure gain and THD before and after, and be prepared to experiment.

 

[AUDIO FREQ]

Not the pad on the mic. Using a pad as a way to load the preamp with no mic attached, evaluate its noise.

I personally can’t say I ever have problems with mic noise in the real world, nor with preamps of which I use a lot of antique technically noisy tube types, unless the source levels are so small as to suggest the wrong mic or preamp is being used for the job. Usually the rare noise problem is asking a ribbon and a high gain tube pre to do more than is reasonable for the situation. Air motion alone is usually the overriding noise source, swamping all else, outside of any hum fault.

It’s very easy to look for noise problems in a vacuum and find them, then use the same equipment on a recording job and hear none. I’ve been down that road numerous times.

Haven’t used this mic, but like poster #2, am skeptical that Sony would release a mic like this with a questionable noise floor. There’s plenty of recommendations for it from classical recordists, ambient usage as the S in MS, etc. It wouldn’t fly if considered noisy by those users. Maybe there are faulty samples out there. I’d certainly dig into that further.

So engage the PAD on the Mic preamp with nothing attached, to make sure it's not the mic preamp? I can try that later today.

It says on the spec sheet 19dB, and others have pointed out it's a bit noisier than most mics. It does sound fantastic though.

 

[OneRoomStudio]

One question about this circuit - if the two legs of the XLR are receiving different signals (they must be at least slightly different, or why use two different capsules), wouldn't that affect the CMR? I'm not saying that's what's responsible for the noise, per se, just seems like a weird way to design a mic.

 

[Khron]

wouldn't that affect the CMR?

CMR only cares about (output / input) impedances.

 

[OneRoomStudio]

CMR only cares about (output / input) impedances.

Damn, you're right, of course. I need to retrain my brain from the days when I was taught that 'balanced' and CMR had to do with opposite-polarity identical signals.

 

[kags]

This mic is more fairly compared to small or “medium” diaphragm mics. Km84 and 451 are similar noise-wise. Is that why nobody ever liked them?(!)

Run your mic through an LA2A and see if the mic self-noise matters. Better yet, make music!

I’m all for the search of high performance, but an apple will never be an orange.

 

[k brown]

Not the pad on the mic. Using a pad as a way to load the preamp with no mic attached, evaluate its noise.

I personally can’t say I ever have problems with mic noise in the real world, nor with preamps of which I use a lot of antique technically noisy tube types, unless the source levels are so small as to suggest the wrong mic or preamp is being used for the job. Usually the rare noise problem is asking a ribbon and a high gain tube pre to do more than is reasonable for the situation. Air motion alone is usually the overriding noise source, swamping all else, outside of any hum fault.

It’s very easy to look for noise problems in a vacuum and find them, then use the same equipment on a recording job and hear none. I’ve been down that road numerous times.

Haven’t used this mic, but like poster #2, am skeptical that Sony would release a mic like this with a questionable noise floor. There’s plenty of recommendations for it from classical recordists, ambient usage as the S in MS, etc. It wouldn’t fly if considered noisy by those users. Maybe there are faulty samples out there. I’d certainly dig into that further.

Indeed - far too much obsessing about self noise specs; ignore the numbers and listen!