Seeking Advice: Best Preamp Design for Low-Noise, Balanced Microphones

[bigben83]

Hi everyone,

I'm currently designing a compact, low-noise 2-channel preamp module and could use some advice on the best preamp topology and components for the job. The module needs to support both microphone and line-level inputs, have balanced XLR outputs, and feature remote volume control via a 10k linear potentiometer. Selectable phantom power (24V) is also required.

Key Design Requirements:​

• Ultra-low noise performance for professional audio applications
• Flexible power: 12-24V DC or potentially phantom power
• Balanced XLR outputs (preferably electronically balanced)
• Remote volume control using a 10k linear potentiometer with a DC supply (Similar to this https://rdlnet.com/product/st-vca3/)
• Input gain range: -60 dB to +4 dB

I’ve been considering preamp ICs like INA163, ADA4627-1, THAT1583, OPA1656, but I'm open to suggestions on what would work best for ultra-low noise performance. Additionally, I’m weighing whether to go for active balancing or a transformer-based output stage—would love some input on the trade-offs for each approach.

Has anyone here worked on something similar or have recommendations on circuit design, component choices, or best practices for achieving low-noise, high-quality audio performance? Any insights on PCB layout techniques to reduce noise and interference would also be much appreciated.

This is for a specialised system used in a church setting.

Looking forward to your thoughts!

 

[gyraf]

Why would it have to be "ultra low noise" if used in a church setting anyway?

 

[bigben83]

Why would it have to be "ultra low noise" if used in a church setting anyway?

To be used in acoustically dead rooms. so I'm aiming for as low noise as possible

 

[gyraf]

Now you have me confused: acoustically dead rooms, in a church setting..?!?

Trying to figure out exactly what you are aiming for here, it's not clear at all yet..

 

[bigben83]

Ha Ha sorry to confuse you. Think modern church with carpet floor, accoustic ceiling tiles. dense foam padded seating. acoustic slat-style wall treatment.

All I am after is a really good quality balanced mic preamp. which I can possibly modify the volume control so it can be remotely controlled. via a small seat-mounted control.

 

[k brown]

Ha Ha sorry to confuse you. Think modern church with carpet floor, accoustic ceiling tiles. dense foam padded seating. acoustic slat-style wall treatment.

All I am after is a really good quality balanced mic preamp. which I can possibly modify the volume control so it can be remotely controlled. via a small seat-mounted control.

Remote control of the actual mic gain, or of the line-level output volume?

 

[micolas]

Why would it have to be "ultra low noise" if used in a church setting anyway?

@bigben83
I agree with @gyraf
Will the church be empty, without an audience?
Regardless of the acoustic treatment, the mere presence of a crowd of people produces a lot of noise. Breathing, coughing, whispering, other noises produced by people, rubbing, or touching clothes, objects, chairs, etc., all these cumulative noises are substantial.
The specific "live" noise would overcome the noise of the preamps.

 

[Newmarket]

Ha Ha sorry to confuse you. Think modern church with carpet floor, accoustic ceiling tiles. dense foam padded seating. acoustic slat-style wall treatment.

All I am after is a really good quality balanced mic preamp. which I can possibly modify the volume control so it can be remotely controlled. via a small seat-mounted control.

Any decent off the shelf micpre / mixing desk would be fine for the job.
Whilst not wanting to discourage DIY activity - it seems you might be starting from 'scratch'. Italmost certain to cost you more in time and money compared to buying something. And the church would be waiting a long time for the kit.

 

[bigben83]

Remote control of the actual mic gain, or of the line-level output volume?

Yes it would be the line-level output volume that would be remote controlled.

 

[bigben83]

Thanks to all that have replied,
I get the feeling that there isn't a preferred IC to use for preamps. I've put this task out as a job on upworker seems to be plenty of talent to help out.

 

[micolas]

@bigben83
But what is the ultimate goal?
Indoor/outdoor local live PA or remote PA for a relatively close location
Audio recording
Streaming, radio/tv broadcasting, etc
For all these purposes I have used easily accessible common equipment over the years and SNR has never been a problem

 

[Newmarket]

Thanks to all that have replied,
I get the feeling that there isn't a preferred IC to use for preamps. I've put this task out as a job on upworker seems to be plenty of talent to help out.

If putting it out for development then you need to rethink this:

• Input gain range: -60 dB to +4 dB

But how many of these systems do you envisage making ?
I have a feeling that it may not be enough to cover the developer cost let alone materials / fabrication etc.