Hello!

Back in the mic making game and working on a Mid-Side setup! Anyways, I bought several TSB2555 capsules and looking at the datasheet it says the operating voltage is 1-10V (). Seems like a big range...any recommendations of what voltage to get the lowest self noise and highest SPL? Lowest noise matters most to me. Also can the TSB2555 be used in a Schoeps style circuit? I assume so but would like to verify.?

Thanks!

Best regards,
Blair

I bought several?
TSB2555 capsules and looking at the datasheet it says the operating voltage is 1-10V?
( ). Seems like a?
big range...any recommendations of what voltage to get the lowest self noise and highest?
SPL? Lowest noise matters most to me. Also can the TSB2555 be used in a Schoeps style circuit?

That capsule is an electret. It needs no polarizing voltage.

Regarding “lowest self noise,” you might end up considering a larger capsule. Capsule self-noise is inversely proportional to active diaphragm area. Said another way, larger capsules have (or at least potentially have) lower noise than smaller capsules.

Another factor is capsule sensitivity. The higher the capsule’s output level, the lower noise the microphone could have — because you’ll need less preamp gain to get a usable signal level into the DAW. Preamps add noise (especially consumer-grade preamps, especially at high gain settings), but even at low gain they’re amplifying both the signal and the noise from the mic. The higher the signal level from the mic, the less preamp gain you’d need, which tends to result in a lower-noise track.

I’m not sure I understand the need for low noise AND high SPL. I think that microphones built for high SPL can afford to be noisier, and in fact typically are noisier, because the mic’s noise floor will be inaudible as compared to the very loud signal. In the case of condenser mics, the circuit can easily overload due to a high SPL transient — or, the downstream preamp could clip if the mic’s output voltage is too high. There are several common solutions to that, such as putting a capacitive pad on the mic’s input circuit, and/or attenuating the signal within the circuit to reduce the likelihood that the preamp clips. But most of those solutions effectively lower the signal-to-noise ratio of the mic. In other words: raising SPL capability also raises the mic’s effective noise floor. You’ve turned down the signal, but the mic’s native noise floor stayed the same (hence: lower signal-to-noise ratio), and you need more preamp gain to hear the attenuated signal, so the preamp amplifies the mic’s noise floor.

Audio design usually involves tradeoffs.?

The TSB2555 can be used in a Schoeps style circuit, although the full Schoeps circuit includes a DC multiplier that electret capsules do not need. The DC circuit in a Schoeps mic contains roughly 50% of the components of the circuit, so that’s not a trivial thing. You wouldn’t want to build a Schoeps circuit from a schematic if you’re using the TSB-2555, because you’d be doing twice as much work as needed.

Other people on this forum can point to PCBs for Schoeps-based *audio* circuits that more easily adapt to the TSB-2555. Or you could see buy MicParts S-25, which is a full mic kit with a Schoeps-derived audio circuit. (Full disclosure: I developed and sell that kit, so the previous sentence is an advertisement, not an impartial recommendation.)

But, as suggested above, if your goal is lowest possible noise, the TSB-2555 won’t get you there. By way of comparison, the MicParts S-87 (a large-diaphragm mic kit with a full Schoeps circuit and a very high-output capsule) delivers 6-8dB higher output than typical electret Schoeps mics, with lower noise.?

Also, if you want highest possible SPL, the Schoeps circuit wouldn’t be my first choice.

—
matt.

Sadly, the 2555 data sheet you link to is mostly nonsense.? This capsule is a FETless electret, and the data sheet has details of the characteristics of the impedance converter shown in the schematic -- which doesn't exist within this capsule??
(The 2555 capsule only contains the part shown within the dotted line box on the schematic)
So, although you don't need a polarising voltage - as recordinghacks has already indicated - you will need an impedance converter.? That can be a Schoeps style FET interface, or perhaps an op amp impedance converter?
Mic Scharf has already linked to my Mid/side project . The FETless version of that project? shows how you might interface a capsule like the 2555, in it simplest form.
And it will be the capsule noise itself which dominates with that circuit.

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I have a question regarding the EMI/RF suppression caps. On this page:??the value is .22nF (220pF) and here 22nF. That is a big difference, what is right?.

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Gavin, yea you can. I did it here:?

Hi Jules

Did you know any easy way/alternative to buy from JLI electronics in Europe and not being "killed" by a massive "customs fee" after also paying a big Shipping cost?

Thanks!

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I’m working to have Micboosters in the UK carry them but ut us work in progress. They do have the TSB2555 capsules?

Some great info! I didn't realize that these capsules are fetless and thus don't need the polarization like I was using on the EM272s. I don't have any OPA164x opamps on hand. How would I modify a schoeps circuit to work with the capsules? Also probably a silly question, but like the em272's can these TSB2555's be placed in parallel to improve the SNR?

Just wanted to ping the group to see if there's a recommended transistor style preamp design for the TSB2555.

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Yes, the “Alice” or Pimped Alice. They both have a FET front end. You need that for the impedance. ?There aren’t any PNP or NPN only ones?

Thanks Jules! Found the schematic. Is a 1G Ohm resistor really needed? Why such a high value? Wouldn't this add noise to the circuit?

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Yea it is ( the 1Gig) needed. ?The capsule has a capacitance of 15-55pF so that forms an RC filter that takes care of the noise. It also provides DC bias to the FET (or What ever the Impedance converter is) and finally develops the voltage to get sensed. ?There are some fets, usually the internal to an electret ones that have a “leakage diode” in them that serves ?the same purpose?

Interesting. Could a diode be used instead of the 1GOhm resistor? Resistors that size seem challenging to source after some quick searching.

I use these ones, if its any help:

I use those as well and some SMD versions.

Best Regards,

Jules Ryckebusch