What is inside in Eartrumpet's Edwina?

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Hi Members!
I am new to this forum and successfully built my first 47-FET of which i am very proud of but had some help.
Since i am also playing Bluegrass i wanted to ask you for your opinion about these Eartrumpet mics p.e. Edwina that are more and more used on stage. I know that they have good marketing, unique look and were right in time, but would like to know what is inside (capsule) and how the wiring is established in the small handle with build in XLR socket. Might be also of interest for others?
Did someone ever had a closer look at it? Thought about doing kind of diy. Thanks! 
 
This might constitute a starting point: http://recordinghacks.com/microphones/Ear-Trumpet-Labs/Edwina

Also, especially considering the form factor, you can bet your booty the electronics are most likely SMD.
 
Yeah you're right. But would be of interest how everything looks like inside...
 
Don't know the circuit, probably simplified schoeps since it's "transformerless". Not truly flat, since there's eq for proximity effect.
Capsule is chinese electret used in Blue Spark and some chinese mics from aliexpress.
You are paying for the look and marketing.
Want something similar? Buy Blue spark, remove HPF, remove input capacitor, rewire capsule for electret use (backplate to fet gate, diaphragm to ground), use lower values output caps. You will get similar result.
 
Never understood this marketing or aesthetic, guess I scrutinize too DeeplyLooks like it came from my box of failed  diy projects from college days, all scavenged and repurposed...or contrived steampunk.' Spose if i was a normal person instead of a mic geek It might seem interesting. Lots of decent and practical mics use those electret capsules.
 
I'd be happy to explain exactly what's in there.

The circuit is a modified Schoeps-style - not simplified actually, but some unique component values and a few additions. Far from being SMD, the electronics are all discreet components hand wired point to point. Not even a printed circuit board. We use very high quality caps.  We hand match the paired resistors and transistors. We bias each JFET individually with an oscillosope and distortion analyzer. The JFET and its bias resistors and 1G gate resistor are built on a small board and mounted directly to the capsule inside the headbasket to minimze any leakage in the super-high impedance section of the circuit (between the capsule and the JFET gate). I've attached the exact schematic. The coupling caps to the BJTs are quite small in the Edwina - .01uF - giving a counter to proximity effect with the chosen capsule to make the low end flat at 6 inches. We do other models using values up to .05uF there, which provides a rumble filter but is full range in the low frequencies for practical purposes. There's a feedack cap around the JFET that matches the high end  to the capsule, similar to the U87 circuit.

The capsule is a Transound TSB-2555 26 mm single diaphragm electret.  I like the sound. For our purposes, electret is much more reliable for a live-use mic, and the 26mm size is a great compromise between some LDC character and a very consistent polar pattern across a wide response, which larger dual diaphragm capsules definitely lack. That's the key to good feedback rejection. The only problem with these capsules is that they're not manufactured very consistently. Our QA on them rejects about 30% for not being within our target response. So for DIYers, I would definitely suggest getting ten and profiling them.

We build the mics all by hand in a small 5-person shop using pretty much exactly the methods I used to build the first ones in my basement as a hobbyist. The look reflects that. Some people love it, some don't. I do think mic DIYers are missing out if they don't get into playing with their own body designs. Most of the sonic character of any mic comes from the capsule and the headbasket and the acoustic interaction between them. We need more inventiveness in that area. I could post  some pics of the guts if any one is interested.
 
 

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Hi pgrahametl,
Welcome to the forum and thanks for explanation!
Nice to have designer of commercial products giving so detailed info!
 
Those 330 ohm and the 680 between them look to me like a differential pad. There's a similar input padding arrangement inside my TC Konnekt 48.

PS: There's that little asterisk (*) next to them, with the mention below the schematic that they're matched, so...
 
Thank you all and especially pgrahametl! Very interesting and thanks for your detailed information about this mic. I am interested if you could some pics of the guts. You do a great job. Congrats!
 
pgrahametl said:
I'd be happy to explain exactly what's in there.

The circuit is a modified Schoeps-style - not simplified actually, but some unique component values and a few additions. Far from being SMD, the electronics are all discreet components hand wired point to point. Not even a printed circuit board. We use very high quality caps.  We hand match the paired resistors and transistors. We bias each JFET individually with an oscillosope and distortion analyzer. The JFET and its bias resistors and 1G gate resistor are built on a small board and mounted directly to the capsule inside the headbasket to minimze any leakage in the super-high impedance section of the circuit (between the capsule and the JFET gate). I've attached the exact schematic. The coupling caps to the BJTs are quite small in the Edwina - .01uF - giving a counter to proximity effect with the chosen capsule to make the low end flat at 6 inches. We do other models using values up to .05uF there, which provides a rumble filter but is full range in the low frequencies for practical purposes. There's a feedack cap around the JFET that matches the high end  to the capsule, similar to the U87 circuit.

The capsule is a Transound TSB-2555 26 mm single diaphragm electret.  I like the sound. For our purposes, electret is much more reliable for a live-use mic, and the 26mm size is a great compromise between some LDC character and a very consistent polar pattern across a wide response, which larger dual diaphragm capsules definitely lack. That's the key to good feedback rejection. The only problem with these capsules is that they're not manufactured very consistently. Our QA on them rejects about 30% for not being within our target response. So for DIYers, I would definitely suggest getting ten and profiling them.

We build the mics all by hand in a small 5-person shop using pretty much exactly the methods I used to build the first ones in my basement as a hobbyist. The look reflects that. Some people love it, some don't. I do think mic DIYers are missing out if they don't get into playing with their own body designs. Most of the sonic character of any mic comes from the capsule and the headbasket and the acoustic interaction between them. We need more inventiveness in that area. I could post  some pics of the guts if any one is interested.

Welcome pgrahametl!

Thanks for sharing ;)

Simplified, in case of not using DC converter, since it's electret capsule only ;)
Additional Drain capacitor doesn't act like U87 deemphasis but still it attenuate some high frequencies.
This capsule isn't so bright, but it doesn't harm to use it.
Anyway i also like this capsule.
Two suggestions for the circuit:
- C4/C5 could be removed
- C8/C9 could be much lower value as 2.2nF not 22nF.
C4/C5 isn't effective for high frequency attenuation, only affects badly phase.
C8/C9 22nF/330ohm also affects badly phase and audible range of high frequency. Moving it from 10kHz to 100kHz still works for RF but doesn't affect audible frequency spectrum.
Then you could increase drain cap value a little.

Love to see the guts ;)





 
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