New DIY large condenser circuit in AliExpress?

[jacson]

I found this recently seems pretty new based on the reviews and I'm thinking if its a good deal for a DIY on a BM-800 for example. It has the main board that amplifies the capsule and a polarization plate, apparently that is suitable for large diaphragm capsules (34mm>). Does anybody have thoughts on this considered a high quality circuit and if it can be compared to other known microphones for their high quality? Thanks

https://www.aliexpress.com/item/100...o.order_list.order_list_main.4.36481802daPz9G

 

[Khron]

Well, as the only photo from the seemingly only review left for this item shows the board mounted with zipties in what looks like a BM800 body. That's not what i'd call "right", neither mechanically nor (especially) electrically.

Cute thought, convenient, but not for BM800's.

 

[jacson]

Well, as the only photo from the seemingly only review left for this item shows the board mounted with zipties in what looks like a BM800 body. That's not what i'd call "right", neither mechanically nor (especially) electrically.

Cute thought, convenient, but not for BM800's.

but speaking in value with included 2 circuit boards that's apparently compatible with large capsules must be worth it in my opinion. or if there's any DIY microphones out there that are this cheap

 

[metalockpick]

@MicMaven got a set. They're cheap, they function.
I don't believe that they use a DC-DC to boost polarization voltage, just available phantom pwr. Not the most dynamic or efficient preamp.
Typical Ali lack of documentation.

 

[rogs]

Well, the main title sentence has words in English ----

" Large Diaphragm Condenser Stereo Dynamic Microphone Accessories Amplifier Circuit Board DIY Mic Repair Wireless Module "

Not sure quite what they are describing?.... Is it for a dynamic mic or a condenser -- high -Z or lo-Z input impedance.
All a bit of a 'wishy washy' description.....
Think I'll stick to my stripboard OPIC mics for a simple, cheap high quality condenser mic preamp... fits into a BM800 without zip ties as well!

 

[Khron]

It has what might be a JFET (gate on the single-pin side of the sot23 package), but loads of passives after that, and one can only wonder what the opamp is supposed to be doing there...

 

[MicMaven]

Howdy! I purchased and tested this set of mic boards with @metalockpick patiently looking over my shoulder. They manage both true condenser and electret condenser capsules. Overall, I consider they are uninspiring and dull, suffering what I perceive is poor articulation with lack luster treble affect. They are reasonably quiet, but NOT as inherently quiet as, for example, the popular OPA Alice boards. While I have not measured them with a proper, formal protocol, they seem noisy compared to commercially produced boards.

They are what they are: $10 condenser circuit boards. They would certainly do in a pinch. While the gold foil capacitors is lovely . . . they sorta look and fee sorta "cheap" - and there is substantial manufacturing artifact giving them an unfinished appearance.

Note: These boards do not easily fit a BM-700/-800 body. While they are sufficiently narrow, they are 80mm long, which is exactly the length of the internal mounting rails of a typical BM-700/-800 chassis.

I may edit this post and provide a comparative recordings in due course. Until then, in a word, "Meh." I will probably replace them with other, quieter, more dynamic and musically exciting boards.

Of course, this is just MY take; your mileage may vary. // James / K8JHR //


PS - I appreciate the input I received from
Mr. Metalockpick as I tried them out. JR

 

[Khron]

What the hell even is that second board supposed to be (doing)?

 

[jacson]

What the hell even is that second board supposed to be (doing)?

Honestly probably for aesthetics, but possibly it's missing some resistors and a diode could be a clue.

 

[Khron]

By "second" i actually meant the bottom board, the one without any active components.

 

[jacson]

By "second" i actually meant the bottom board, the one without any active components.

Exactly, just for a show-off, but what I showed by circling may be impacting on the second board to fully function (if its really that possible)

 

[Khron]

The missing diode may well be a zener most likely. Not easy to say without tracing out the connections though...

 

[jacson]

Well, the main title sentence has words in English ----

" Large Diaphragm Condenser Stereo Dynamic Microphone Accessories Amplifier Circuit Board DIY Mic Repair Wireless Module "

Not sure quite what they are describing?.... Is it for a dynamic mic or a condenser -- high -Z or lo-Z input impedance.
All a bit of a 'wishy washy' description.....
Think I'll stick to my stripboard OPIC mics for a simple, cheap high quality condenser mic preamp... fits into a BM800 without zip ties as well!

I've read your LDC circuit and I find it interesting thanks. I might as well try out your LDC circuit design through the stripboard method, but how will I get the OPA1641 /w sip8 to dip8 on the market? I found this on ebay, if it's even legit...

 

[MicMaven]

By "second" I actually meant the bottom board, the one without any active components.

Do you suggest I should try it without the second board? (I do not believe it worked without both boards, but I tried so many things when it first arrived, and failed to take enough notes, I am not sure about it.)

Parenthetically, the two boards are connected solely with a four-pin jumper on the "back" side of each board, which is sort of difficult to see in the photo. You probably knew that, but I try to be helpful.

James

 

[Khron]

I noticed that 4-pin jumper, but that still reveals nothing about the intended role of that second board

 

[jacson]

Do you suggest I should try it without the second board? (I do not believe it worked without both boards, but I tried so many things when it first arrived, and failed to take enough notes, I am not sure about it.)

Parenthetically, the two boards are connected solely with a four-pin jumper on the "back" side of each board, which is sort of difficult to see in the photo. You probably knew that, but I try to be helpful.

James

I do think they disabled it with missing components on the first board. We really don't see why they have a second board that does nothing

 

[Khron]

Why would you assume it "does nothing"? Have you already traced out the entire circuit?

 

[jacson]

Why would you assume it "does nothing"? Have you already traced out the entire circuit?

no, just assuming most likely it's from aliexpress so you cant expect anything to fully function

 

[Khron]

I prefer to "only" ackowledge the possibility of DOA stuff, but "worst case" expect "only" suboptimal / convoluted solutions. Which kinda seems to be the case here. Which is why my curiosity would drive me to reverse-engineer the circuit...

 

[MicMaven]

expect "only" suboptimal / convoluted solutions. Which kinda seems to be the case here. Which is why my curiosity would drive me to reverse-engineer the circuit...

Yep - I get that. We see this sort of thing in other fields, for example copy cat or "patterned after" circuits / devices in amateur radio where the Chinese version is not quite a knock off of the original, but more often a stripped down "Muntzed" version of the original, and sold for a fraction of the cost of the original. They work, but not as well as the original. I have a $130 Software Defined Radio (SDR) with lots of neato sub-circuits, and a $40 Chinese copy cat that employs ONLY the main chips and essential supporting circuits. It works remarkably well, but nowhere close to the overall performance of the original.

I suspect (i.e., guess without knowing) this circuit is just such a take off of a more advanced, higher quality circuit that employs more and certainly better components. Therefore, it works, but not as well as the original it may be patterned after.

Just my WAG ... you guys know more about this sort of thing. James