Superlux S502 MK2 test, teardown and improvements

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from your graph, regarding noise and freq responses they def seem on par !
I wonder how they behave time wise, this is a very important factor.
Did you do some blind A/B listening tests ? That may be the real tie breaker.
Thanks for sharing !
 
I've read numerous reviews mentionning that it is very prone to pick up radio magnetic interferences, did you experience that too ? Thomann reviews mention that a lot, for instance
 
thomasdf said:
I've read numerous reviews mentionning that it is very prone to pick up radio magnetic interferences, did you experience that too ? Thomann reviews mention that a lot, for instance
Click to expand...
I think this is not RFI but internally generated disturbances..
 
Hi Jan,

I have only used my MK4 capsules to record. So no experience with the original capsules.
Reiner
 
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Hi All,

the Superlux S502 MK2 has arrived :) Here are my first impressions and measurement results.
Subjective sound impressions:
It seems that the capsules are very well matched. With a small UKW radio 1m located exactly in front i am not able to find an audible interchannel difference when i exchange L/R channels.
In comparison with MBHO-capsules i would describe the sound as reluctant (very flat response, no hyped heights).
The noise floor is audible but not unpleasant.
I don't think that the stated sensivity of -36dBV is correct. I would say it is 2dB lower. More about that after exact measurements.
First measurements:
Both capsules have nearly the same polarisation voltage (60,2V and 59,9V).
Nearly the same capsule capacitance: 39pF and 40pF.
Wonderful: both backplate and membrane are seperated from case. This is important to use the real Schoeps circuit. More about that later on.
The mic self noise is moderately low: -116,0dBV(A) and -116,2dBV(A), see attached picture.
BUT: At 20kHz the noise level is too high. Such a high level i only know from OPA Alice circuit designs..

More measurement results will follow...
BR MicUlli
 

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Hi there, I didn't yet take time to read the whole thread but I will and I can say that this mic is stunning !

I have a pair and used it in many occasions and I'm more than amazed of how it sounds. I've made a few mods (but find the post about them) : replaicing the coupling cap (680pF I guess) by polystyren-copper caps and also one or two electrolitics which voltage was a bit low and sorten capsules' wires...

I've recorded "ambiance" classical ensembles, inside piano, choir... everything is nice and clean.

@MicUlli I'm sure you'll be more than happy with this mic : for me (and for 125€ !) it's a must have.
 
Emmathom said:
it's about the S502 MkII (better avoid it !)
the S502 "first version" does not suffer from RFI
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But S502 MkII is exactly what i test right now. The "first version" has not Schoeps compatible capsules and is far more noisy :confused:
I have not encountered any RFI problems yet..
 
MicUlli said:
But S502 MkII is exactly what i test right now. The "first version" has not Schoeps compatible capsules and is far more noisy :confused:
I have not encountered any RFI problems yet..
Click to expand...
Great for you. Mine (first version) is not so noisy
 
I scanned the Web for the capsule thread dimensions of the Schoeps MK4, which are supposedly identical to the S502 MkII capsule thread, aren't they? Does anyone know? Would be nice if a suitable cheap (black) SDC donor body could be found to build CM6/MK4 clones using the S502 MkII capsules.

Jan
 
jp8 said:
I scanned the Web for the capsule thread dimensions of the Schoeps MK4, which are supposedly identical to the S502 MkII capsule thread, aren't they? Does anyone know? Would be nice if a suitable cheap (black) SDC donor body could be found to build CM6/MK4 clones using the S502 MkII capsules.
Click to expand...
Just do this mod:
1731070649592.png
 
The next measurements have been done. I tested the headamp in the S502 MK2 (noise) with a capacitor of 44pF.

The cap was connected between the contacts for backplate and diaphragm. GREEN curve.
Then i changed the arrangement with cap connected between contact backplate and GND (case). BLUE curve.
Based on these measurements i could calculate the capsule noise. ORANGE curve.
For comparison i inserted the total noise curve already posted. RED curve.

Takeaways:
The capsule noise is -118,2 dBV (A), improvements in the circuit may bring up to 2,2 dB lower total microphone self noise.
The circuit has a gain of -1,2 dB and is therefore a "REAL" Schoeps design (capsule between gate and drain of the jfet).
This is proven by the blue curve. In this configuration the average gain is 6 dB higher.
 

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I have studied the circuit board a little bit. Nothing special, standard Schoeps CMC5 from 1973. But the component selection is nasty. JFET is MMBF5486, the output transistors are BC860C. All of them noisy as hell..
The oscillator circuits do not have the same frequency, they are shifted by about 23kHz. And now the first problem: After a while the beat frequency gets smaller and smaller. I saw 19kHz in the spectrum with nearly 1mV level! Maybe most of us do not detect this, but my grandchildren would...
Time to take the solder iron :)
 

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