Hello,
How much does a preamplifier impact sound quality? Should the electret capsule primarily determine the sound quality? I’m considering purchasing the AD620BRZ, INA849DGKT, AD797ANZ, and MUSES03 for testing, but I’m unsure if they will work well together. I’m working on building a microphone for musical instruments and would appreciate any insights.
Thanks!
How much does a preamplifier impact sound quality? Should the electret capsule primarily determine the sound quality? I’m considering purchasing the AD620BRZ, INA849DGKT, AD797ANZ, and MUSES03 for testing, but I’m unsure if they will work well together. I’m working on building a microphone for musical instruments and would appreciate any insights.
Thanks!
I assume you use an electret capsule with built-in JFET. Is that correct and if so, two pin or three pin? What model?
The amplifier after such a capsule (I mean an amplifier that is specific for the microphone, not a general-purpose microphone preamp) can have some effect on the large signal performance. The late Scott Wurcer had a bootstrapping method that could much improve the signal handling, it can be applied to three-pin capsules. For two pin, my late colleague Henk ten Pierick had a method to reduce distortion at the expense of a bit worse noise.
Does the whole thing need to be supplied by 48 V phantom supply?
The amplifier after such a capsule (I mean an amplifier that is specific for the microphone, not a general-purpose microphone preamp) can have some effect on the large signal performance. The late Scott Wurcer had a bootstrapping method that could much improve the signal handling, it can be applied to three-pin capsules. For two pin, my late colleague Henk ten Pierick had a method to reduce distortion at the expense of a bit worse noise.
Does the whole thing need to be supplied by 48 V phantom supply?
Thank you for answering me. It will be a Primo EM273 (Omni) 3 pin capsule. The connection will be with a 9 volt crown.
I'm not quite sure how to choose between a special purpose preamplifier and a general preamplifier . I was asking companies like THAT. They recommended me the expensive MUSES03 and a few inexpensive models. Although they have specialized preamplifiers for microphone https://thatcorp.com/low-noise-preamplifier-ics/.
Do you mean it is going to be supplied by a 9 V block battery? Does that only apply to the capsule or also to the preamplifier?
Regarding the output of the preamplifier, what kind of input does it have to drive?
Yes, both the mic and preamplifier will be powered by 9V. It will only have a volume control input.
What do you want to connect the preamplifier's output to? To an unbalanced line input, an unbalanced microphone input, a balanced line input, a guitar amplifier input?
OK, so you want to interface an EM273 to a balanced XLR microphone input without phantom supply, using a circuit that works on 9 V.
@TNT uses an EM273 for his fixed-gain field recorder. You can actually listen to the results, as he has posted some recordings near the end of the thread.
As far as I recall, he uses a variant of this circuit:
with the silicon diode shorted and with two extra resistors at the outputs.
For your application, some things would need to be changed. You would definitely need AC coupling and small series resistors at the outputs, and an op-amp type that works well at a single 9 V supply and that doesn't draw too much current. The second op-amp can either be turned into a gain of -1 amplifier or removed alltogether (quasi-balanced output).
By the way, the late Scott Wurcer published two interesting articles about this subject in Linear Audio. Part II in Linear Audio vol. 3 has some tried and tested examples. Unfortunately the Linear Audio website is about to go offline.
https://linearaudio.net/diy-low-noise-microphone-preamplifiers-part-ii
Something like this, for example. The OPA1677's common-mode range is more suitable for single-supply operation, it draws less current and its noise is still low enough (well below the microphone's). The bootstrapping via the 47 uF and 100 uF electrolytic capacitors practically eliminates the distortion of the FET inside the EM273, like in the circuit TNT uses. The 47 uF, 63 V bipolar electrolytic capacitors keep the amplifier's bias voltages out of the mixing console and hopefully protect the circuit if the microphone input should have 48 V phantom supply after all.
Sorry, I forgot to answer you. Thanks for the diagram. It works. And if I want to connect 3 electronic capsules, will they also work according to this diagram?
Do you mean three EM273s in parallel? It will probably work, but not very well. You lose the advantage of the low distortion of this configuration, especially when the three EM273s pick up different sounds.
From this I see it as an un-balanced microphone output > driving a balanced microphone input.
This would mean forgoing the noise cancelling properties of a fully balanced scenario.
A true balanced output would be more elegant, but this solution can actually work quite well as long as the impedances are balanced and the receiving end has a good common-mode rejection.
It's essentially equivalent to a differential output plus a common-mode signal of half the amplitude of the differential signal. I didn't see a simple way to make it completely balanced without causing extra battery drain, extra noise and/or extra costs.
It's essentially equivalent to a differential output plus a common-mode signal of half the amplitude of the differential signal. I didn't see a simple way to make it completely balanced without causing extra battery drain, extra noise and/or extra costs.
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Fine preamplifier ICs for when you are designing the mixing console, useless when you want to interface an EM273 to an existing mixing console using a 9 V battery as supply.