Takstar CM 60 suggested mods/improvements (?)

[pmfalcman]

Hello everyone.

After reading this and other forums several times (well.. almost) I decided to buy Takstar CM-60 mics. So it's all your fault, guys
Still probably several weeks before the parcel arrives but I'm already looking for advice.

First off - the slotted grill. I read so much about the importance of rounded edges, capsule being as close as possible to the front etc, so I wonder whether shaving of those thick, sharp slots wouldn't be advantageous? There's mesh beneath them, it seems.
I know a good machinist who could take care of this, no problem.

The other thing is fet bias. Here I need some help and finger pointing
RuudNL mentioned several times that Takstars need bias adjusting. And a trimpot place. Unfortunately I'm electronically dumb. Half-dumb anyway. I have proper tools, I know a cap from a resistor, can solder smd circuits without problems (been soldering even 32-pin chips once upon a time) but I wouldn't recognise, say, a voltage divider even if it bit me in the ass. But I can design you a logotype for your mic Or make a custom industrial/loft style lamp
What I need is: " replace Rxx with trimpot of xxOhm and adjust from this point to ground (or across this element) till the V is such and such."

Any other suggestions in the field of replacing elements with better ones?

I do not record music/vocals. Field recording definitely. So not looking for warmth nor character.

Thanks in advance - Paweł

 

[Franlennon]

Hopefully someone will chime in!

 

[kingkorg]

There is nothing in particular i would improve circuit wise. I took the capsule voltage up to ca80v to get the noise bit lower. The capsule can take it. Modding the capsule would not be easy, and the slots in front are not the issue. Backplate has to be modded. But the stock capsule is not bad either it's just that it has a 8k peak, which can be addressed with eq. So being aware of the peak helps. The mic is great platform for other capsules of this format and i use it as such. This is probably the best pencil mic for the price i've encountered.

Bias wouldn't be a deal breaker for outdoor recording unless you are recording rocket launch. It is critical for high SPL. In any case there are well documented threads on Schoeps bias which apply here.

 

[pmfalcman]

Thanks, kingkorg.

There are no launchpads around here within reasonable distance so rockets are a non issue really. The best I will do are trains, heavy machinery and gun shots. Though I started with recording crickets yesterday (the mic has finally arrived).
So yes - bringing the noise down will be beneficial.

Just out of curiosity - what capsules do you use/recommend for it?

 

[kingkorg]

Thanks, kingkorg.

There are no launchpads around here within reasonable distance so rockets are a non issue really. The best I will do are trains, heavy machinery and gun shots. Though I started with recording crickets yesterday (the mic has finally arrived).
So yes - bringing the noise down will be beneficial.

Just out of curiosity - what capsules do you use/recommend for it?

I modified the stock one's backplate, but it wasn't an easy task. And i use one of Neumann's from kms105 which fits perfectly. People seem to have good experience with 3U capsules for this format, and they should fit.

 

[Chrisfromthepast]

The 3u 0.5mm capsules fit well and are a direct replacement. Cardioid, omni, and super cardioid.
The complete takstar mics are cheaper than a high quality aftermarket capsule so I have used them for parts as well. The backplate from a cm-60 is inside one of my banzai capsules and it will probably stay there. The body tube is well made, so Im slowly migrating some builds that were housed in 603s donor bodies over to cm-60.
I have stopped buying used 603s types…
Hope this helps.

 

[pmfalcman]

Thanks, guys.

I know if 3u capsules, though the confirmed info on 0,5 mm is valuable.

This modifying backplate spiked my interest!

 

[gtroc71]

This is a great thread discussing the backplate mods
https://groupdiy.com/threads/pronomic-scm-1.69474/post-892528

 

[pmfalcman]

I know well this thread, thanks.
BTW it finally convinced me to buy Takstar mics.

 

[HerbertR]

These CM60s are currently very cheap to order, under 25 Euros.... Is it really true that the 3U 0.5mm SDC with 22.5mm outer diameter would fit, has anyone checked this really physically yet...?

Then it would be great if we could start a "Group Buy" for EU/Europe for 3U 0.5mm SDCs to get a great discount. I would be in with a few pairs of them.....

 

[Voyager10]

This is a 3U 0.5mm hypercardioid capsule on a CM60:



Happy to confirm it does indeed work well.

 

[MicMaven]

This is a 3U 0.5mm hypercardioid capsule on a CM60: Happy to confirm it does indeed work well.

Way cool, and thanks for reporting in. Looks good.
________________________________

Not intending to hijack, but hoping to expand this thread about capsules for the CM-60, I recently traveled a different route and purchased a super low cost 22 mm brass-cased cardiod capsule on eBay for around $10 US. It screws easily on a Takstar CM-60 microphone body as a drop-in replacement. It also fits MXL and other brand 22m condenser capsule saddles.

The jury is out as I continue to evaluate how it sounds compared to the original Takstar CM-60 cardiod capsule, a same-diameter MXL-700 cardiod capsule, and MXL-603/604 omni-directional capsule I have on hand. Unfortunately, I cannot make a direct comparison to the 3u capsule above at this time.

It sounds just OK to my ears, slightly restricted and congested, lacking brilliance in the upper registers compared to the original CM-60 capsule which sounds pretty flat and slightly more open. In contrast, the MXL-700 capsule is inherently much louder and is almost too bright and airy, perhaps exhibiting the typical elevated high frequency response curve frequently exhibited by low cost modern capsules. The MXL 603/604 omni-directional capsules pose something of an apples-to-kumquats comparison, so I have set them aside for now.

I attach a few photos for the curious, below.

This is a condensed version of the Seller’s product description:

Clear Sound Microphone Large Diagram Condenser DIY Microphone Parts​

​

Frequency response: 100 HZ-10 KHZ​

Sensitivity: -26± 1dB ​

Output impedance: 2.2K​

Size: approx 2.2x1.3cm/1x0.5in​

Material: Brass ​

​

Manufactured with the most precise machinery to achieve sensitivity making them able to reproduce subtle sounds. A very good condenser microphone for recording music. Every microphone goes through our intensive testing procedure. This includes a frequency test as well as a self-noise test to ensure every circuit performs within specifications. This microphone can be widely used in live-/conference/classroom, etc. Brass, durable, sturdy & long for time service. Package Includes: 1x Microphone ​

Samples:

I attach two recordings comparing this new capsule with the original Takstar capsule to permit others to judge these capsules for themselves. Let me know if I should provide additional information or other samples to facilitate assessing its relative capabilities, and I will do my best to accommodate the same.

Comparison Sample 1 – Speaking 5 inches away, no EQ and same mixer settings for all, except slightly reduced gain on MXL-700 in an untreated 5m x 5m room.

View attachment 22mm capsule comparison 1a n .wav

Comparison Sample 2 – Martin HD-28v guitar lick 32mm from instrument, no EQ and same mixer settings, except slightly lower gain for MXL-700 in an untreated 5m x 5m room.

View attachment 22mm capsule comparison 2.wav

So, … ahem …. um … you be the judge. Any questions?

James / K8JHR
________________________

Disclaimer – crude, unrehearsed, unprofessional recordings ... anyone can see why I am not a voice over actor or in-demand studio musician, and I sing even worse than I play! So, Whaddaya want for nothing?

 

[HerbertR]

I have 3U SD mm5 cardioid capsules and CM60 microphones. I made some improvements to the amplifier, replaced some components like 1000pF capacitor, 47UF capacitor ... with better ones and soldered a 10K potentiometer for bias calibration on the free designated place. Calibration was easy, the second harmonic almost completely disappeared after calibration finding the best setting.

The good thing about it - the microphone sounds fabulous with the 3U Capsules, top class, well balanced, really lively, great clean low mids and low end and nice open highs. The Takstar capsule,... well,....is not so good, maybe a case for experiments like KK does with them. Will try to do the same. Too muddy mids and dull highs.

Another con of the CM60 circuit - the noise floor is not really bad, but can't compete with e.g. AKG C391 and CK91 Cardioid, which needs 7-8 dB more amplification and is still noticeably quieter by a few dB...

I'll try the CM63 next and hopefully the background noise will be a bit quieter....

 

[jeremynothman]

Way cool, and thanks for reporting in. Looks good.
________________________________

Not intending to hijack, but hoping to expand this thread about capsules for the CM-60, I recently traveled a different route and purchased a super low cost 22 mm brass-cased cardiod capsule on eBay for around $10 US. It screws easily on a Takstar CM-60 microphone body as a drop-in replacement. It also fits MXL and other brand 22m condenser capsule saddles.

The jury is out as I continue to evaluate how it sounds compared to the original Takstar CM-60 cardiod capsule, a same-diameter MXL-700 cardiod capsule, and MXL-603/604 omni-directional capsule I have on hand. Unfortunately, I cannot make a direct comparison to the 3u capsule above at this time.

It sounds just OK to my ears, slightly restricted and congested, lacking brilliance in the upper registers compared to the original CM-60 capsule which sounds pretty flat and slightly more open. In contrast, the MXL-700 capsule is inherently much louder and is almost too bright and airy, perhaps exhibiting the typical elevated high frequency response curve frequently exhibited by low cost modern capsules. The MXL 603/604 omni-directional capsules pose something of an apples-to-kumquats comparison, so I have set them aside for now.

I attach a few photos for the curious, below.

This is a condensed version of the Seller’s product description:

Clear Sound Microphone Large Diagram Condenser DIY Microphone Parts​

​

Frequency response: 100 HZ-10 KHZ​

Sensitivity: -26± 1dB ​

Output impedance: 2.2K​

Size: approx 2.2x1.3cm/1x0.5in​

Material: Brass ​

​

Manufactured with the most precise machinery to achieve sensitivity making them able to reproduce subtle sounds. A very good condenser microphone for recording music. Every microphone goes through our intensive testing procedure. This includes a frequency test as well as a self-noise test to ensure every circuit performs within specifications. This microphone can be widely used in live-/conference/classroom, etc. Brass, durable, sturdy & long for time service. Package Includes: 1x Microphone ​

Samples:

I attach two recordings comparing this new capsule with the original Takstar capsule to permit others to judge these capsules for themselves. Let me know if I should provide additional information or other samples to facilitate assessing its relative capabilities, and I will do my best to accommodate the same.

Comparison Sample 1 – Speaking 5 inches away, no EQ and same mixer settings for all, except slightly reduced gain on MXL-700 in an untreated 5m x 5m room.

View attachment 130073

Comparison Sample 2 – Martin HD-28v guitar lick 32mm from instrument, no EQ and same mixer settings, except slightly lower gain for MXL-700 in an untreated 5m x 5m room.

View attachment 130074

So, … ahem …. um … you be the judge. Any questions?

James / K8JHR
________________________

Disclaimer – crude, unrehearsed, unprofessional recordings ... anyone can see why I am not a voice over actor or in-demand studio musician, and I sing even worse than I play! So, Whaddaya want for nothing?

View attachment 130083View attachment 130084View attachment 130085

For my ears (listening on headphones, mind you) the new capsule feels very flat, and somehow not very 3D. I don't hate the tonality, but it's feeling a little cloudy. Maybe it's actually a wider pattern than the others? The other two feel more alive, but the Takstar has some ugly lispy sibilance for my ears. I actually like the MXL best.
Are these actually recorded at the same time? To me the mic position sounds different.

 

[HerbertR]

Some more improvements with the CM60 Amp, not really DIY friendly due to the SMDs...

I did all the high impedance parts like the two 1G resistors, 1000pF... from this Schoesps circuit in the air with a Teflon pin, added a RF filter, PCB ground connection via ferrite bead, replaced the SMD 2SK208 FET with a 2SK117, new bias calibration....taadaaa... And the mismatched colors of the case and 3U capsule? Who cares. First test shows outstandingly detailed sound, fabulous, noiselevel low like from AKG391. Need more testing. $150 for a mic of this league, unbelievable... Hopefully the CM63 Circuit comes with the same performance already delivered from the factory.

 

[museric]

Oh my goodness, I'm taking notes - this is great! I've recently received a pair of these CM-60s with a mind to mod as close to KM84s as reasonable, and now I'm quite excited of the possibilities (and I'm not afraid of SMDs - years ago I've had some experience retrofitting a test product with a properly-spec'd tiny smd resistor with a very not-up-to-the-task iron, and since then I've picked up some strategies and a much better iron.)

 

[Voyager10]

The main problems with the stock CM60 circuit seem to be (a) the gain is low, ~1.3x where an ideal FET would give 2x; this makes the noise worse, and (b) the max output level is very low (or distortion at any given output level is worse than it could be).

@HerbertR - do you have any measurements of gain or max level with the new FET? In my own measurements (this thread) the 2SK117 was one of the best in the Schoeps circuit.

 

[pmfalcman]

replaced some components like 1000pF

Are you sure about the units? If I'm not mistaken I can see 100n on the cap. 100nF is much more picos
Or have you changed from 1000pF to 100nF?

 

[k brown]

Are you sure about the units? If I'm not mistaken I can see 100n on the cap. 100nF is much more picos
Or have you changed from 1000pF to 100nF?

1000pf is commonly seen between the capsule and the FET.

 

[jp8]

Some more improvements with the CM60 Amp, not really DIY friendly due to the SMDs...

I did all the high impedance parts like the two 1G resistors, 1000pF... from this Schoesps circuit in the air with a Teflon pin, added a RF filter, PCB ground connection via ferrite bead, replaced the SMD 2SK208 FET with a 2SK117, new bias calibration....taadaaa... And the mismatched colors of the case and 3U capsule? Who cares. First test shows outstandingly detailed sound, fabulous, noiselevel low like from AKG391. Need more testing. $150 for a mic of this league, unbelievable... Hopefully the CM63 Circuit comes with the same performance already delivered from the factory.

A while ago, I did some measurements on the CM-60 and CM-63 and posted them in another thread. I'm reposting the file here. My conclusions and some suggestions for improvements are included in the file.

Personally, I would not have changed the input capacitor. The one on the PCB is an excellent C0G type. But everyone seems to have a different opinion on what are good and not so good caps for this purpose. The High-Z area is conformally coated, though in my case it is not completely covering all the solderpads and components it should have covered. And ideally, Takstar should have cleaned the PCBA from reflow solder flux. Anyway, in this case, I think it's good enough and the added value of a teflon turret is questionable, IMHO. What bugged me most about the CM-6- was the very low input stage supply voltage of just 7.2V, which limits headroom. Max SPL @ 0.5% was only 124 dB SPL. Usable, bot can be improved. That would be the first thing I would have changed. And like you already did: make the bias adjustable.

The CM-63 electronics is better in most aspects. The JFET stage runs on 13.4V. Much better. But the bias adjustment was totally off... And with the 2k Drain and Source resistors in the circuit, the adjustment range of the pot was too small. I changed them to 2k7 and was able to adjust the bias such that minimal THD could be achieved. Initially, max SPL for this mic was also 124 dB SPL, but after modification, it improved to 138 dB SPL. The 2k7 resistors would increase noise slightly, but the capsule self-noise is higher than the self-nois of the electronics. So not much can be gained there, except if you raise the capsule polarization voltage.

The CM-63 has very good RFI rejection and due to its longer body and more space between switch and XLR, it is much easier to get a transformer circuit in. I'm currently in the process of building several PCBs with different circuits for both the CM-60 and CM-63 and will make PCBs available through PCBWAY.

An improved KM84 circuit for the CM-60 would have been the first one I would release, if I hadn't made a mistake in the PCB that slipped in after the last DRC check . I will have to order again, but I am waiting until I have more PCB designs to order. The transformer only just fits between HPF switch and XLR. I sent prototypes of this PCBA to @joulupukki for test and evaluation and he was very satisfied with them. Especially about the significantly improved RFI rejection. He shared a recording on his Youtube channel here, where he compares his DIY KM84, the Mic-Parts version, and my design. Together, we optimized the design until it is what it is now. I am still very grateful for all the time and effort he put into this! The CM-63 version of this circuit will get a CMOS polarization voltage generator, a selectable -6 dB/oct or -12 dB/oct HPF and -20 dB pad.

Jan