how can i increase sound in circuit Opic and opa alice

[rogs]

Hi, thanks to Mic Scharf and Rogs for the great project!!! I also ordered a set of circuit boards and built them in BM 800 housings and the jli 2555 capsules. The noiselevel is very low, pretty cool. I find the used JLI capsules are bit too bright.

Does anyone have an idea where in the circuit you could implement a reasonable de-emphasis of the highs? A few dB less in the highs above 8kHz would be a bit better.

This Opic circuit is imo almost indistinguishable in a direct parallel comparison with a Schoeps electret circuit on a PCB from VAMI and these JLI 2555 capsules. Not really bad...

The OPIC circuit is pretty much as simple as things can get...... It's a unity gain impedance converter, with no extra gain stages - or even non essential resistors - in the signal path. That helps to keep the noise down.

Where it doesn't work so well is when you consider adding internal EQ. That would not only be a bit of a major rethink, it would add extra components in the mic itself. .... Extra components in this early part of the signal path will add noise, in addition to doing what you hope the filter will do!
Also, adding a simple single order low pass filter is a bit brutal..... Yes, it will attenuate the offensive 'bright' mid range boost -- but also everything else above that !

If you're recording, then adding EQ in your DAW in post is probably a better answer. Much more subtle in controlling specific parts of the frequency range.

If you're doing things live, then you might like to look at the option of adding EQ - at line level - further along the signal path?
( I made some notes on cheap hobby versions of that idea HERE )

Simplest and best of all is k. brown's idea - fit a better capsule. I've found JLI's shipping costs make their products pretty expensive outside the USA.
If you want to add a capsule that will really change the character of the mic, you might look at Arienne Audio capsules? ..
Bit expensive maybe? -- but really good IMHO.

 

[MicMaven]

Simplest and best of all is k. brown's idea - fit a better capsule.

While I am confident Mr. Brown and Mr. Rogs are quite correct and their advice is surely on solid ground, you MIGHT try my SUPER LOW COST, SUPER LOW TECH, easy peezy ANALOG solution: I sometimes shroud a hot capsule with a layer of open cell foam, topped with a layer of high-thread-count (always red) cotton fabric, and, in extreme cases, add a thin layer fiber-fill batting, or, heaven forbid, a layer of good old bathroom tissue, otherwise known as TP, as a "poor man's" high frequency attenuator. While I am sure honest to goodness recording engineers would shudder at the very thought, it often tames hot, shrill capsules, and, occasionally, shrill, sibilant headphone receivers.

Really, please do not laugh or scoff at this suggestion - I really do this and I think it works well (in some cases) and certainly the price is right!!)

Oh no ... please don't offer to pay me for this highly practical advice proffered at absolutely no charge !!!

(Offered both in fun and as a serious, short term suggestion.) Happy trails to you. James

 

[Екатерина]

While I am confident Mr. Brown and Mr. Rogs are quite correct and their advice is surely on solid ground, you MIGHT try my SUPER LOW COST, SUPER LOW TECH, easy peezy ANALOG solution: I sometimes shroud a hot capsule with a layer of open cell foam, topped with a layer of high-thread-count (always red) cotton fabric, and, in extreme cases, add a thin layer fiber-fill batting, or, heaven forbid, a layer of good old bathroom tissue, otherwise known as TP, as a "poor man's" high frequency attenuator. While I am sure honest to goodness recording engineers would shudder at the very thought, it often tames hot, shrill capsules, and, occasionally, shrill, sibilant headphone receivers.

Really, please do not laugh or scoff at this suggestion - I really do this and I think it works well (in some cases) and certainly the price is right!!)

Oh no ... please don't offer to pay me for this highly practical advice proffered at absolutely no charge !!!

(Offered both in fun and as a serious, short term suggestion.) Happy trails to you. James

Oh, that's not funny. They've always been very effective, but it's difficult to quantify them accurately

 

[Khron]

a layer of good old bathroom tissue, otherwise known as TP, as a "poor man's" high frequency attenuator

Good enough for tens (if not hundreds or more) of NS10 tweeters...

 

[micolas]

While I am confident Mr. Brown and Mr. Rogs are quite correct and their advice is surely on solid ground, you MIGHT try my SUPER LOW COST, SUPER LOW TECH, easy peezy ANALOG solution: I sometimes shroud a hot capsule with a layer of open cell foam, topped with a layer of high-thread-count (always red) cotton fabric, and, in extreme cases, add a thin layer fiber-fill batting, or, heaven forbid, a layer of good old bathroom tissue, otherwise known as TP, as a "poor man's" high frequency attenuator. While I am sure honest to goodness recording engineers would shudder at the very thought, it often tames hot, shrill capsules, and, occasionally, shrill, sibilant headphone receivers.

Really, please do not laugh or scoff at this suggestion - I really do this and I think it works well (in some cases) and certainly the price is right!!)

Oh no ... please don't offer to pay me for this highly practical advice proffered at absolutely no charge !!!

(Offered both in fun and as a serious, short term suggestion.) Happy trails to you. James

A few pieces of toilet paper() turn a pair of cheap headphones with exaggerated treble into perfectly usable ones

 

[MicMaven]

A few pieces of toilet paper() turn a pair of cheap headphones with exaggerated treble into perfectly usable ones

Right ... although the photo depicts what appears to be paper toweling. Perhaps an alternative is coffee filter paper. It would last longer than TP and, after all, it IS a type of "filter."

Are those your headphones? I have a pair, myself. James

 

[micolas]

Right ... although the photo depicts what appears to be paper toweling. Perhaps an alternative is coffee filter paper. It would last longer than TP and, after all, it IS a type of "filter."

Are those your headphones? I have a pair, myself. James

It's toilet paper I unfolded it in a single layer and used as much as I liked for a more neutral sound. I cut them round and put them under the canvas layer. I have many models of Superlux headphones. They have an excellent performance/price ratio. They produce OEM for well-known brands.

 

[HerbertR]

Hi, I also built this OPIC circuit using Mic Scharf's Opic PCBs and the awesome OPIC VM voltage multiplier PCB counterpart to drive a brass beesneez C12 capsule with the capsule voltage in a TF11 body from Ali.
I used a MC14106 CMOS instead of the CD40106 suggested by the BOM for this additional "voltage pump" circuit . It gives the same voltages when changing R5 (schematic) / R15 (Mic Scharf's PCBs). So can be used as a direct replacement. It's super easy to change the capsule voltage and test the audible results. Fantastic circuit, so simple, so good, ...


By the way, I immediately came to the conclusion that I prefer ~52V (65V-12.5V, 2K Ohm at R15 used) over 60V (72V-12.5V, 600 Ohm at R15) as voltage for the Beesneez BC12 capsule. It dampens the highs a bit, makes the sound shine thicker, gives an additional "on the face" with a little bit more lowend. 60V sounds audible slightly thinner, and also more "crystaline". I prefer here a few volts less.

This motivates me to also to adopt the voltage divider by a few volts down in my 251 tube mic builds with these BN 12 Brass capsules.