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91
Microphones / Re: Haufe T14/1 and alternatives
« Last post by Banzai on April 19, 2021, 06:57:50 PM »
Sowter's are a different size.

Haufe prices have gone a bit crazy lately. Best option is to try and buy second hand.
92
Microphones / Townsend Labs Sphere Guts and basic analysis
« Last post by kingkorg on April 19, 2021, 06:22:09 PM »
I finally got one to play with in order to get to the bottom of the case. Some interesting stuff, but no rocket science. Very doable for a DIY project, as the software is available for download, and is the heart of the system, great results can be achieved relatively easily and inexpensively.

The mic uses 797 audio CY002 capsule. Once again 797 audio proved to be insanely high quality, reliable, and consistent capsule manufacturer. Just look at the graph, front compared to back frequency responses.   

The capsule:



Front to back FR and sensitivity comparison.



As you can see, the frequency response of the mic is not flat. It is corrected in the software, first to flatten it out, then to apply various curves both to front and back to emulate responses of various mics it emulates.

Now, can you just stick this capsule in a random dual out mic and use it as Sphere? No, there is HF attenuation built in the mic which serves as a kind of hardware key. It looks like this, measured by injecting signal into the mic.



This is Sphere's filter compared to typical ''Microphone Parts EQ'' mod for schoeps based circuits. This is SP C1 with two 10k resistors and 1nf cap. Difference bellow 50hz is due to coupling caps in C1.



I have created a CSV file which can be loaded into CurveEQ from Voxengo, just before Sphere plugin so that one can use a microphone with mentioned 797 audio capsule in a flat circuit.
https://app.box.com/s/nq2a3rsi961z8dimr6rra0t5fpm88by8

Here's how the response of the capsule looks like when built in filter is taken out, compared to stock mic.



The headbasket shape plays a role of course. If one decides to go DIY and make their own version, this should be taken into the equation. So u47 shape is the way to go. Here is the response of the mic with and without headbasket.



Wow! Headbasket does play a role! Yup, but how audible it is might be debated. It is clearly measurable.

How about the electronics? Interesting, but i didn't bother to trace the circuit. Filtering curve can be achieved in Schoeps and other type circuits, so why complicate things? The way i see it, it's capsule straight to TLC070 which is used as the first stage. And yes, the mic is dead quiet and has crazy low THD. So this opamp might be something to think about.



Polarisation voltage is about 60v, supplied to the backplate, i believe the topology used for the voltage multiplier is similar to Rode NT1.



The other side:



The signal goes further to the two 33178 which split and balance the signal. Probably similar to Jules' arrangement, but that is just a guess on my side.
https://www.instructables.com/OPA-Based-Alice-Microphones-a-Cardioid-and-a-Figur/



The mic is extremely useful even without modeling capabilities. I've used several versions i had built myself, and for room stereo, M/S miking, is a must for me. The comparison measurements and audio shootout at Audio Test Kitchen show Sphere's Sony C800 model and the original are virtually indistinguishable, seem as matched pairs in measurement graphs. I enjoy using this emulation. This makes sense, as both mics are based around same type of capsule and share similar headbasket shape.

Sony's capsule. Darn, those look similar, and according to some measurements and calculations i've taken they measure remarkably close. But i'm not claiming anything! :D


 


93
Black Market / Re: WTB : Resotune 2
« Last post by willgmr on April 19, 2021, 05:27:33 PM »
I'm also interested if nashkato passes on yours!
94
Filters/Equalizers / Re: Poor Man's Pultec EQP1-A Build Support Thread
« Last post by ruffrecords on April 19, 2021, 04:37:42 PM »
Ian,

thanks again for the quick reply.

The inductor's intrinsic resistance is substituted in a gyrator circuit by a series resistance so I believe in theory this can be replicated. Is there a way to find out what the equivalent resistance is in the inductor you have chosen for your PCB?

The value is not critical. The Q is mainly determined by the sum of this resistance and other circuit resistances. A good design ensures the inductor resistance is only a small percentage of the total so the other circuit resistances dominate the Q and the designer can properly control Q independently of the inductor. In practice, the actual resistance depends on the tap selected so it is not constant. Someone once measured the dcr of the inductor and I think they published the results here. Might be worth a search. If that fail, a value of 100 ohms would probably do.

Cheers

Ian
95
The Lab / Re: Fuse for Neumann NSMa-23 Power Supply
« Last post by Khron on April 19, 2021, 04:37:14 PM »
"Don't seem to work" is a bit vague. Is that saying, they blow straight away?

Might not be a bad idea to power that through a series (tungsten fillament) lighbulb, a so-called "bulb tester".

Then again, if it's all stock, it wouldn't be too far-fetched to think one or more filter capacitors might've failed short-circuit, and as such, are drawing more current than normally expected, through the transformer.
96
Brewery / I don’t think this guy is married...
« Last post by pucho812 on April 19, 2021, 04:34:05 PM »
If he is, she is a keeper.
97
Dynamic Processors / Re: CLX-VU Build Thread (DBX 160VU ) UPDATE: REV 3
« Last post by AW on April 19, 2021, 04:25:07 PM »
98
Filters/Equalizers / Re: Poor Man's Pultec EQP1-A Build Support Thread
« Last post by spaceludwig on April 19, 2021, 04:21:53 PM »
Ian,

thanks again for the quick reply.

The inductor's intrinsic resistance is substituted in a gyrator circuit by a series resistance so I believe in theory this can be replicated. Is there a way to find out what the equivalent resistance is in the inductor you have chosen for your PCB?
99
Microphones / Re: Haufe T14/1 and alternatives
« Last post by snigglepit on April 19, 2021, 04:02:37 PM »
Thanks, but it sounds as though all of those are already claimed, no?
100
Microphones / Re: Haufe T14/1 and alternatives
« Last post by Vac11 on April 19, 2021, 03:53:10 PM »
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