Will a K67 capsule sound good in a MXL 990 body?

[Arbolito]

Hello,

I'm thinking of doing the MXL 990 circuit replacement, based on a Schoeps CMC5 circuit. I also wanted (in fact primarily wanted) to replace the capsule, and I was wondering if the K67 capsule will sound well through this circuit?

The K67 capsule I'm looking at is a cardioid-only version (model name is RK-87C).

 

[Khron]

Big "maybe", depending how tolerant to sibilance you are or aren't.

You'll probably want to add a capacitor (or a capacitor in series with a resistor) in parallel with the drain resistor, to tame down some of the high frequencies (as the more complicated circuitry in the U67 and U87 does).

 

[SparkleBear]

Thanks for always chiming in to help a fellow mic junkie, @Khron. I’ve been pondering about similar things for a current project, deemphasis on a fet network vs tube… FET land is still not as familiar as tube world. @RuudNL has shared some great info about this too… diy troves.

Post in thread 'DIY FET mic with De emphasis 87 esque guidance needed ......'
DIY FET mic with De emphasis 87 esque guidance needed ......

I would be worried about sibilance with that capsule into a flat circuit too…

 

[Arbolito]

Thank you for the help and suggestion on the high frequency taming, should I then not worry about the compatibility of the capsule with the circuit?

Then for the high frequency taming, this is the circuit I want to put inside the body: circuit link (I hope I'm not breaking any rules by linking the place where i'm buying it), it states it contains "Additional capacitors to allow you to tune the high-frequency response of the circuit to accommodate brighter-voiced capsules such as RK-87 and RK-12."

Will then using these additional capacitors achieve the high frequency taming?

 

[Khron]

Will then using these additional capacitors achieve the high frequency taming?

Likely. But keep in mind, for $129 you could probably hunt down 2-4 used 990's, AND the parts you'd need to put together the electronics for those. Even if you were to recreate the circuit on perfboard...

 

[Arbolito]

Likely. But keep in mind, for $129 you could probably hunt down 2-4 used 990's, AND the parts you'd need to put together the electronics for those. Even if you were to recreate the circuit on perfboard...

Thank you, its clear to me now. I don't have enough knowledge to make a circuit board from scratch however, and the MXL 990 circuit is circular shaped. So I would have to design a new PCB from existing Schoeps CMC5 circuit schematics to go the cheaper way, am I mistaken?

 

[SparkleBear]

That is the way. I cant speak to what the exact schematic the mic-parts guys are using. I dont know if its 1:1, they usually have their take on circuits. Looks like that in the language of the kit that it says it already has a place for the de-emphasis cap on their board.

If you want to make your own circuit pcb i would recommend getting Kicad as its free and really powerful. Then with calipers and other tools you can CAD out your layout on your own pcb. Then send it to a fab (like JLC or PCBWay) to get printed.

Its a more rewarding experience to go the full diy route for sure. Get some 990s which Iiirc are already a schoeps-ish circuit. GUS made some amazing notes on the mods to clean up the stock circuit. (Gus' MXL 603s mod - Pictures/Part numbers -thanks Flatpicker ) Maybe you could start there to learn about the circuit?? That would be cheapest option.

MXL is selling their 990 new direct on reverb for cheaper than everyone else (even used ones) Reverb... they are on holiday vacation mode right now. I dont know if it was just a timely deal or their regular thing but i was getting from them around $50-60 if I remember correctly. Their MXL 770 is a great option if you want to add a transformer to a design. I love this one because you can design around the switches for pads/filters and patterns.

Good luck. LMK if you have questions about getting kicad started.

 

[TimG]

I bought a 990 as my first mic to take apart. I got it cheeep, which you should do. Watch shipping too!

I was just learning so I bought the transformer based 990xf replacement circuit from mic parts. I should have waited to do the $1670 job until I was a little better at soldering but it was educational. 990XF Circuit Kit


These guy are right, there is a lot that can be done before spending that kind of money on a cheap MXL 990/770

 

[mjmajilton]

Why not just use a K47 or especially the Flat47 and not worry about EQ? Then a cap upgrade on the original pcb if it’s the through hole type. I do a big revision of the pcb but it’s more complex.
I also like the replacement grill MP sells.

 

[Gus]

IIRC ricardo posted an add on EQ for the K67 like capsules in the China Schoeps based circuit however, I have not found the thread with searches. Others have posted about add on EQ for that circuit.
Now what Flatpicker posted was more of what upgraded parts I found that could fit in a SD microphone body it was not a big deal just different parts. I did not address different JFETs to be used or matching the output PNPs and other parts removing the build out resistors adjusting the bias of the stages etc.

 

[MicMaven]

Hello,

I'm thinking of doing the MXL 990 circuit replacement,

Gee. I wonder whether the board replacement kit represents good value for his hard earned brass. It replaces the entire original circuit for a whopping $129, which is double the cost of a used MSL990, and not that far from double the cost of a new one. The cost of a replacement capsule ranges from $120 (Arienne Audio) and $160 (MicParts) for a total cost exceeding $300. Would we (he and I) not be better served spending $300 on a new Sennheiser MK4, AKG C214, Shure Beta 27, Shure SM27, or another really good mic in that price range? While it obviates the heady sense of self-satisfaction one gets from a successful home brew project, I suspect the overall performance of one of these microphones exceeds that of the rebuilt MXL990. I presume the capsules, circuits and bodies of these models outperform the modified MXL990. Or am I missing something?

Considering the number of experts who say the capsule is 95% of the final sound, and the circuit board contributes only 5% to the final sound, I wonder whether the original poster would be better served with just a capsule upgrade, which could provide a substantial improvement at a much lower cost. It seems, to me, a rather high price for such a modest improvement.

I do NOT intend to rain on the gentleman's DIY parade, but I seriously wonder whether the circuit kit provides enough improvement to warrant its hefty price tag. Would it truly represent good value overall? (... notwithstanding the kit building experience.)

Therefore, I as to the original poster, I sugget a capsule upgrade and not a full kit, saving the balance of the cost for a higher quality microphone or a more cost-effective rebuild that would produce a more substantial improvement at lower cost later.

Or am did I miss something along the trail? James

 

[Arbolito]

Gee. I wonder whether the board replacement kit represents good value for his hard earned brass. It replaces the entire original circuit for a whopping $129, which is double the cost of a used MSL990, and not that far from double the cost of a new one. The cost of a replacement capsule ranges from $120 (Arienne Audio) and $160 (MicParts) for a total cost exceeding $300. Would we (he and I) not be better served spending $300 on a new Sennheiser MK4, AKG C214, Shure Beta 27, Shure SM27, or another really good mic in that price range? While it obviates the heady sense of self-satisfaction one gets from a successful home brew project, I suspect the overall performance of one of these microphones exceeds that of the rebuilt MXL990. I presume the capsules, circuits and bodies of these models outperform the modified MXL990. Or am I missing something?

Considering the number of experts who say the capsule is 95% of the final sound, and the circuit board contributes only 5% to the final sound, I wonder whether the original poster would be better served with just a capsule upgrade, which could provide a substantial improvement at a much lower cost. It seems, to me, a rather high price for such a modest improvement.

I do NOT intend to rain on the gentleman's DIY parade, but I seriously wonder whether the circuit kit provides enough improvement to warrant its hefty price tag. Would it truly represent good value overall? (... notwithstanding the kit building experience.)

Therefore, I as to the original poster, I sugget a capsule upgrade and not a full kit, saving the balance of the cost for a higher quality microphone or a more cost-effective rebuild that would produce a more substantial improvement at lower cost later.

Or am did I miss something along the trail? James

What I'm looking for is to have a Neumann microphone sound, without spending thousands of dollars. I was looking at the rk87-c capsule (copy of K67) as its like the one used in the U67, and then I just wanted a circuit that will drive the capsule properly.

Will the circuit upgrade really only change 5% of the sound, compared to the capsule's drastic change? I watched the video on "what gives a microphone its tone", but of course how can I know until I try it myself..

 

[SparkleBear]

Please consider @soliloqueen capsules over the RK. (Arienneaudio.com). It’s so clearly a product oozing with care and detail oriented production. It might be a bit more cost as it’s two sided but I think it’s a better product and it’s gdiy family vibes. I’ve shot it out (not super scientifically) against the Neumann k67 in a u67 and it held its own to my taste.

But I do see that the cardioid only rk87 is only $99 so the arienne capsule will be almost double. Either you choose will improve upon the stock capsule.

So maybe one of these capsules with the eq circuit Gus was mentioning. See where that gets you, then maybe parts upgrade (swapping out the caps if it’s not smd) and if none of that gets you there doing a transformer based (or not) circuit swap?

Long ago, I remember putting a budget k47 on the stock circuit and being very amazed by the improvement. So maybe you’ll be happy with the simple capsule swap.

 

[Khron]

I seriously wonder whether the circuit kit provides enough improvement to warrant its hefty price tag. Would it truly represent good value overall?

Most definitely not

 

[Voyager10]

Will the circuit upgrade really only change 5% of the sound, compared to the capsule's drastic change?

Replacing one basically flat preamp with another is not going to make the leap in quality you're looking for. There is so much which can go wrong - in a real, measurable way - with the mechanical components (capsule, mount, grille, body), that it's not worth fretting over the electronics until they're sorted.

Edit: (If you're jonesing for a U87, try starting with the MXL 2001 instead of the 990. Readily available second hand, and easy to tweak the EQ if the capsule needs it).

 

[mjmajilton]

Replacing one basically flat preamp with another is not going to make the leap in quality you're looking for. There is so much which can go wrong - in a real, measurable way - with the mechanical components (capsule, mount, grille, body), that it's not worth fretting over the electronics until they're sorted.

Edit: (If you're jonesing for a U87, try starting with the MXL 2001 instead of the 990. Readily available second hand, and easy to tweak the EQ if the capsule needs it).

Right. MXL 2001 is the way to go. It’s