Superlux S502 MK2 test, teardown and improvements

[MicUlli]

where we can find rhis pcbs

See Post #67 in this thread

 

[jp8]

Outstanding: frequency response S502 (1st version).
Find attached some pics...

Hi MicUlli,

Could you also share frequency response charts of both the mk1 and mk2 versions? Preferably at 0, 90 and 180 degrees, if you can. I could do them myself with the mics I have, but I do not fully trust the results

Jan

 

[Emmathom]

Well I was already very satisfied with the sound of my S502 1rst version... now it's Xmas time !

I'm impatient to install my new board...

 

[janpanis]

Bingo. That’s what I get for trying just once and being too frustrated with tiny tools to even think about trying the other way.

Alas, the capsules are electret and soldered a way way (ring is conected to backplate and ground) that one can't test them in Schoepses, though they would fit. Electronics are very basic with a double opamp GS6002. They sound good and the "finish" is very nice Schoepsy.

 

[MicUlli]

Hi MicUlli,

Could you also share frequency response charts of both the mk1 and mk2 versions? Preferably at 0, 90 and 180 degrees, if you can. I could do them myself with the mics I have, but I do not fully trust the results

Jan

Hi Jan,
the frequency response of the S502MKII under different incident angles was already posted in #56. It has not changed significantly with my electronics.

Find attached the frequency response of the S502 with my electronics. I purchased the S502 from "Kleinanzeigen" as "defekt". And it was, so i didnt try to repair the old electronics...

Very pleasing are the noise measurement results:
S502MKII self noise is 14,1 dBA (SPL) left channel and 14,3 dBA (SPL) right channel. Sensivity is -37,4 dBV left channel and -37,7 dBV right channel.
Overload point is around 138 dB (SPL).
S502 (1st version) self noise 15,6 dBA (SPL) left and 16,2 dBA (SPL) right. Sensivity is -43,4 dBV left and -43,7 dBV right. Overload point is around 144 dB (SPL).

No noise artefacts above 20kHz thanks to the very stable JFET-oscillator (420kHz)

Now shipping of the "repair kits" will start...

Best regards MicUlli

 

[jp8]

Thanks a lot for sharing! I skimmed through your posts too fast and missed your post with the S502 MK2 charts. Sorry.

Jan

 

[ubxf]

Hi Jan,
the frequency response of the S502MKII under different incident angles was already posted in #56. It has not changed significantly with my electronics.

Find attached the frequency response of the S502 with my electronics. I purchased the S502 from "Kleinanzeigen" as "defekt". And it was, so i didnt try to repair the old electronics...

Very pleasing are the noise measurement results:
S502MKII self noise is 14,1 dBA (SPL) left channel and 14,3 dBA (SPL) right channel. Sensivity is -37,4 dBV left channel and -37,7 dBV right channel.
Overload point is around 138 dB (SPL).
S502 (1st version) self noise 15,6 dBA (SPL) left and 16,2 dBA (SPL) right. Sensivity is -43,4 dBV left and -43,7 dBV right. Overload point is around 144 dB (SPL).

No noise artefacts above 20kHz thanks to the very stable JFET-oscillator (420kHz)

Now shipping of the "repair kits" will start...

Best regards MicUlli

Great news thank you, I noticed that a fair amount of smd components are required. I've only done repair on a single smd component before. Is it reasonable to attempt building this or is it too big of a step for smd beginner ?

 

[MicUlli]

Great news thank you, I noticed that a fair amount of smd components are required. I've only done repair on a single smd component before. Is it reasonable to attempt building this or is it too big of a step for smd beginner ?

Well, it depends...
You need a small solder iron tip (0,4..0,6mm), a small pair of tweezers, thin solder wire and a good magnifier, preferable binocular.
Fix the pcb on a flat working plate (with tape). Presolder one of the pads of the component. Then position the component
and melt the presoldered pad. That is the best way to handle smd components. Then solder the remaining pads.
AND dont drink too much coffee
BR MicUlli

 

[mhelin]

Another way to solder a couple of SMD components at the same is to use the hotplate method. I've been using a piece of straight around 4mm thick aluminium plate on top of a usual cooking hotplate. Here's one of the videos from Youtube presenting this method, remember to wear a face mask (like a covid-19 one if you have any left):


Edit: There are some small hot plates available on Ebay, might be enough for solderin small preamp PCB's:
https://www.ebay.de/itm/126175900208
Teardown video:

 

[ubxf]

Thank you guys, I'll get a couple of boards in case I fumble the first one : )

 

[ccaudle]

I've only done repair on a single smd component before.

When I first learned to work on SMD components, I found a broken circuit board which was being scrapped and practiced removing and installing components on the broken board before I attempted to work on a board which I thought could be repaired.
It also helps to have an experienced friend sit beside you and show you the techniques, although today YouTube videos can somewhat substitute if you do not have a friend experienced in SMD repair.

 

[ubxf]

when I repaired my synth I found out quickly it was possible to cause more damage than good. Luckily I managed to fix it but it was only one component. I'm determined to soldier through this project though even if it takes a couple of attempts.

 

[janpanis]

Hi Jan,
the frequency response of the S502MKII under different incident angles was already posted in #56. It has not changed significantly with my electronics.

Find attached the frequency response of the S502 with my electronics. I purchased the S502 from "Kleinanzeigen" as "defekt". And it was, so i didnt try to repair the old electronics...

Very pleasing are the noise measurement results:
S502MKII self noise is 14,1 dBA (SPL) left channel and 14,3 dBA (SPL) right channel. Sensivity is -37,4 dBV left channel and -37,7 dBV right channel.
Overload point is around 138 dB (SPL).
S502 (1st version) self noise 15,6 dBA (SPL) left and 16,2 dBA (SPL) right. Sensivity is -43,4 dBV left and -43,7 dBV right. Overload point is around 144 dB (SPL).

No noise artefacts above 20kHz thanks to the very stable JFET-oscillator (420kHz)

Now shipping of the "repair kits" will start...

Best regards MicUlli

Hi Ulli, I was interested in the boards as I wrote before, how can I order/pay them?

 

[pmfalcman]

Thank you guys, I'll get a couple of boards in case I fumble the first one : )

You'll be fine.
SMD are easier than popular beliefs maintain.
Except the smallest size.

@MicUlli gave you a simplest and a shure-fire method to solder them.

For me cheap reading glasses (+3 diopters) work perfectly fine for soldering SMDs.
Plus a hand held magnifying glass (also cheap) for checking the joints. Final QC
You do not need to spend obscene amount of $ for equipment

 

[rvperez]

Hi Jan,
the frequency response of the S502MKII under different incident angles was already posted in #56. It has not changed significantly with my electronics.

Find attached the frequency response of the S502 with my electronics. I purchased the S502 from "Kleinanzeigen" as "defekt". And it was, so i didnt try to repair the old electronics...

Very pleasing are the noise measurement results:
S502MKII self noise is 14,1 dBA (SPL) left channel and 14,3 dBA (SPL) right channel. Sensivity is -37,4 dBV left channel and -37,7 dBV right channel.
Overload point is around 138 dB (SPL).
S502 (1st version) self noise 15,6 dBA (SPL) left and 16,2 dBA (SPL) right. Sensivity is -43,4 dBV left and -43,7 dBV right. Overload point is around 144 dB (SPL).

No noise artefacts above 20kHz thanks to the very stable JFET-oscillator (420kHz)

Now shipping of the "repair kits" will start...

Best regards MicUlli

then S502mk II is more silent but have less dinamic range because, I see S402 mor for drum s and S502MKII for calssical recordings, isn't it?

 

[MicUlli]

then S502mk II is more silent but have less dinamic range because, I see S402 mor for drum s and S502MKII for calssical recordings, isn't it?

Hmm, i am not sure. I doubt that you produce an SPL of more than 130 dB with your drums in practice...
And the overload levels are related to the capability of the electronics. Unfortunately i am not able to produce such high SPL for testing the capsule behaviour.
BR MicUlli

 

[rvperez]

After calculating some technical and commercial aspects i am going to consider the design of pcbs for the Superlux S502MKII based on my MicUlli-design (MBC5X0), see https://groupdiy.com/threads/a-very-versatile-input-stage-for-sdc-mics.80172/

Requirements:
1. Board shall have the same size as the original
2. Using surface mount components, only electrolytic caps are discrete
3. Optional DCDC converter for -20V (will lead to 59V pol voltage and a higher sensivity)
4. Board shall also be usable for the S502 1st version (with the bigger capsules), but limited to 39V pol voltage
Advantages:
1. Better SNR (as already proven)
2. Better max. SPL (as already proven)
3. Much smaller THD
4. No spurious noise artefacts above the audible range

I need at least 2 boards, some of you want 4 boards (thanks for that ), but it makes no sense to order components for a batch smaller than 15 units. So let me know (drop a PM) whether you are interested in some of these "S502MK1+MK2 repair kits"

So long MicUlli

I understand that i S502 we coul use an standar phantom the 39 limitation is doing inside the pcb?

 

[MicUlli]

I understand that i S502 we coul use an standar phantom the 39 limitation is doing inside the pcb?

High pol. voltage is indeed dependent of supply current drawn from P48 voltage. 39V is a compromise...