Samson CL8 Housing Removal and Possible Improvements

[guitardick]

I bought a few Samson CL8 multi-pattern mics. While they actually sound pretty good (considering I got them for for under 120, but the self noise is pretty high, at 19dB(A). When you record with them, they sound pretty good, but after mastering, the noise is more noticeable. I would like to look under the hood of one to see if there is room for component improvements, but for the life of me, I can’t seem to get this thing apart.

Anyone know how?

I asked Samson for a schematic, but they told me, “We don’t have the schematic.” It used to be that when you bought something, it came with a schematic, a component list, suggested custom ”component changes” for specific uses, and a list authorized service centers. Companies wanted you to be happy, so you would continue to support their business.

If anyone has it, please PM me a copy or post it in this thread.

 

[guitardick]

Still looking for the Schematic to the Samson CL8, I would be very grateful.

 

[RuudNL]

They may be similar to the Behringer C-3, the worst microphone I ever had...
This microphone was so noisy, that you could only use it to record (loud!) hardrock...

​

 

[guitardick]

Update: for anyone interested, to remove the housing of the Samson CL8, there is a screw hidden on the front side of the mic under the label, “CL8 Studio Condenser.” There is a small round faux button. Just remove that with some needle nose pliers or a small knife and the screw is there underneath that, see the photo.

 

[guitardick]

I am still looking for a schematic, if anyone has a copy, I would love a one to continue to learn more about electronics. Unfortunately, Samson was not willing to share, when I asked.

 

[Khron]

1) You could consider trying to correct the title of this thread - autocorrect wreaking havoc?

2) Now that you got the mic open, nothing's stopping you from posting a couple decent photos of the insides here - odds are it's not difficult to "decode" for some of us who've seen "a few" mics in our time...

 

[guitardick]

Hi Khron, yes Autocorrect got me again. Hahaha. Thanks for pointing that out, buddy.

 

[guitardick]

I was planning to post some photos, but I wanted to create a complete parts list, before I posted the photos. Some of the parts are hard to read as they are very close together. I will post some pics and the partial parts list in a minute. I can always use edit to update it when I finish that task.

Khron, thanks for the suggestions and interest.

 

[guitardick]

Here are some photos of the inside. My suspicion is that it might be variation of a U87ai.

 

[Khron]

U87Ai-like capsule bias oscillator, sure. JFET + PNP driving a low-ratio transformer? Like MXL2001 / MCA SP1?

 

[guitardick]

Below is a parts list. It is not complete yet, I will update it as I finish the list. I am doing this to exercise my brain, and maybe do some work so others can improve their CL8.

The Samson CL8 has a decent sound, when compared to other Chinese mics. It is built well, fairly durable, but in my humble opinion, it is a little peaky/esshey, has low-ish headroom, not enough lows, not much room for a nicer transformer, and a high noise floor (19dBa). I am not an electronics engineer and I looked up the Chinese part numbers on the internet, so I would GREATLY appreciate being corrected, if I made a mistake.

Goals: (suggestions welcome)

1. Keep and optimize current features (patterns, pad, low cut)
2. Keep similar sound or improve
3. Lower noise floor
4. Increase headroom
5. Extend low end, but keep it tight
6. Measure the TX and if poor, see if an AMI, Cinemag, or other will fit
7. Maybe, alter or add hi frequency de-emphasis to optimize use with stock Chinese K67 capsule or other capsules variants for different flavors: K47, C12, C800, K89
8. ??? Open to suggestions, just not, buy a new mic. I Want to do this to keep my brain from falling into dementia.

C0 (unlabeled connected to the capsule): 471 = 470pf 63V

C1: 103J100 = 10nf/0.01uf 100V

C2: (small,hard to read) 221 = 220pf 50V

C3: 151 = 150pf 50V

C4: 471 = 470pf 63V

C5: 474J63 = 47nf/0.047uf 63V

C6, C7: (not present)

C8: 103J63 = 10nf/0.01uf 63V

C9: 474 +35k = 47nf/0.047uf 35V (tantalum)

C10: 103J100 = 10nf/0.01uf 100V

C11: 475L* = 4.7uF 35V (tantalum)

C12: 105L = 1uF 35V (tantalum)

C13: 226F* = 22uf 16V (tantalum)

C14: 103J63 = 0.01uf 63V

C15: 103J63 = 0.01uf 63V

C16: 331 = 330pf 100V

C17: 331 = 330pf 100V

C18: (not present)

C19: 33 = 33pf

C20: 334J63 = 33uf 63V

C21: (not present)

C22: 474 +35k = 47nf/0.047uf 35V (tantalum)

C23, C24, C25: (not present)

C26: 331 = 330pf 100V

C27: 106L = 10uf 35V (tantalum)

C28: 471 = 470pf 63V

C29: 471 = 470pf 63V

C30, C31, C32, C33, C34, C35: (not present)

C36: 104J100 = 1uf 100V

C37: 103J100 = 10nf 100V

C38: 103J100 = 10nf 100V

C39: 104J100 = 1uf 100V



D1:

D2:

D3:

D4:

D5:

D6:

D7: 47 59A 310

D8:



L1: 41 uH

L2: 41 uH

L3, L4 (not present)

L5: 220 uH 10%

L6: 220 uH 10%



1G (labeled this way): 1 KM

1G (labeled this way): 1 KM



R1:

R2:

R3:

R4:

R5:

R6:

R7:

R8:

R9:

R10:

R11:

R12:

R13:

R14:

R15:

R16:

R17:

R18:

R19:

R20:

R21:

R22:

R23:

R24:

R25:

R26:

R27:

R28:

R29:

R30:

R31:

R32:

R33:





T1: k105 HOYC

T2: A1015 Y51B

T9: 2N5551 148

T10: k105 HOYC



TX1: transformer Unknown

 

[guitardick]

U87Ai-like capsule bias oscillator, sure. JFET + PNP driving a low-ratio transformer? Like MXL2001 / MCA SP1?

Thanks Khron, the truth is, I don’t know, but I want to learn to know. It was just a dumb guess by someone who knows very little. I will probably have to guess wrong 500 times before I guess one thing right. hahaha

Like one version of the U87ai, it has a K67 capsule, a transformer, 4 inductors (U87ai has 2), 8 diodes, and 4 transistors. However, just cause it has 8 diodes and 4 transistors does not mean they are being used the same way or are even the same type of diodes and transistors. This is what I based my dumb guess on.

 

[Gus]

2sk105 found this
https://datasheetspdf.com/pdf/742896/NEC/2SK105/1It is kind of like a 2n3819
IIRC I looked at a CL7 cardiod model(years ago so I can be remembering wrong) when they first were sold and if I am recalling correctly it was a copy of the U87 not a JFET PNP into a lower ratio transformer.

There is a 87 version with a constant current fragment using a JFET in the supply line
This could be a mix of china DC to DC setup as +- and a version of an U87 circuit

I did see some white staining on a 1Gig resistor in one of the pictures so I would clean up the PCB and use a soft clean brush to remove the dust from the capsule. Also there is a lot of stuff inside the headbasket that I would clean up.
I also don't know what is on the 471 cap on the bottom of the plastic part of the capsule mount by the switch.

Do a search for cleaning capsules

I don't remember the CL7 being excessively noisy

 

[guitardick]

2sk105 found this
https://datasheetspdf.com/pdf/742896/NEC/2SK105/1It is kind of like a 2n3819
IIRC I looked at a CL7 cardiod model(years ago so I can be remembering wrong) when they first were sold and if I am recalling correctly it was a copy of the U87 not a JFET PNP into a lower ratio transformer.

Hi Gus, thanks for the reply, I appreciate it. I am still learning, so if I say something wrong, please correct me.

Thanks for confirming that the CL8 might be a U87 clone. Since the CL8 has 4 FETs like one version or the U87ai, I assumed it might possibly be that version. The U87 had only one FET In the schematic I saw. I attached a schematic below of the U87ai to show what I am referring to. This is not me contradicting you, just showing where my stupid guess came from.

Gus, did you measure the transformer in your CL7? If so, do you recall the approximate ratio?

For others reading this:

If you look up the 2N3819 and Neumann, you will see that it was replaced by Neumann in the U87 with the K105 and the SK107.

In the link below, Klaus Heyne, talks about T1 on a U87 schematic having four transistors that Neumann used interchangeably throughout the years, as they were so close in spec. They were the 2436, 2N3819, K105, and the SK107.

https://repforums.prosoundweb.com/index.php?topic=11630.0

 

[guitardick]

There is a 87 version with a constant current fragment using a JFET in the supply line
This could be a mix of china DC to DC setup as +- and a version of an U87 circuit

Gus, what Do you mean by a constant current fragment?

 

[guitardick]

I did see some white staining on a 1Gig resistor in one of the pictures so I would clean up the PCB and use a soft clean brush to remove the dust from the capsule. Also there is a lot of stuff inside the headbasket that I would clean up.
I also don't know what is on the 471 cap on the bottom of the plastic part of the capsule mount by the switch.

Do a search for cleaning capsules

I don't remember the CL7 being excessively noisy

Gus, I‘m not sure what the white stain is, I will look at it tomorrow and clean it. I believe the stuff on the 471 cap is hot glue, as it is secured to the black plastic piece.

Man, most of the resistors are so tiny, I am having a difficult time reading them. I might have to take some out just to measure them to make sure I am reading them correctly. I wish Samson would provide a schematic.

I just bought the CL8 in the photos. It was used. It arrived this way. I will clean it.

I will look to see what Klaus or someone similar says about how to clean the capsule. Thanks Gus, those are all great suggestions.

I have a few other CL8’s. I bought one a while back thinking it is probably going to be a piece of junk. When I plugged it in, I was quite surprised. It sounded much better than I anticipated. Much better than the average Chinese LDC. It had a sound that I instantly liked. So, I bought more, as a store was blowing them out really cheap.

They all sound pretty similar. They are all a little lean in the low end. Not bad, just a little. I wonder if it is the transformer, capsule, or the circuit choices.

My other CL8’s aren’t noisy, I just feel that with a few component upgrades, we might be able to get it lower than the stated 19 dB(A). Maybe increase the headroom a bit, while we improve the stated Noise specs.

 

[Gus]

I did not own a CL7 I had a chance to take a quick look at the PCB and a quick listen.

I was thinking of the circuit by the meter in this one Neumann U 87 | RecordingHacks.com.

Can you take a picture of the bottom of the boards and/or check with a meter what the leads of the transformer connect to.

If the drain of the JFET connects by a cap to the transformer it is most likely a U87 like circuit
if it connects by the emitter of the PNP to a cap then transformer then it is probably like a MXL2001etc. circuit.

 

[guitardick]

Gus, Samson the two circuit boards connected by a 4 pin header. I got that apart, but the bottom of the circuit board is connected to something and there is very little wiggle room to get it to a position where I can take a photo. There is also a metal plate in between, so that makes it even harder to get a good photo of the bottom. I will try and post an update in a few minutes.

Regardless of the relationship to a U87 or not, it is a decent sounding mic with the High frequencies more tame than the usual Chinese Mic.

Any suggestions are welcome and appreciated.

 

[guitardick]

Here are the photos. FYI, T1 is a K105 N channel JFET and T2 is an A1015 PNP Epitaxial Silicon Transistor. Both were designed to be used as AF Amplifiers.

It looks like the drain goes to C8 or C9 (depending on the switch), if C8, then to C10 and then T2, then out the emitter to C13 to the transformer. If C9, then to T2, out the emitter to the transformer. So, my guess is that Khron was right, and it is probably like the MXL 2001 and has a low wind transformer. Don't trust me, I’m a noob.

If it is, like the 2001, I have a few ideas, I’ll share three of them. Still thinking about the other ideas.

1. Choose better values, types and brands for crucial caps and resistors in the audio path. Workout the proper de-emphasis. Then, re-bias to make it sound as good as it can for $30-50 bucks.

2. In addition to better caps, resistors, and rebasing, add a a higher quality, slightly higher ratio 2.25:1 transformer like the AKG 414EB. Lower the gain to increase the headroom. Then, workout the proper de-emphasis for a total of $75-95 bucks. The circuit is a little different, but it appears like it might work.

3. In addition to better caps, resistors, de-emphasis, and rebasing, remove the second transistor and add an AMI, Cinemag, or other higher quality 9.5:1 transformer, so it is more like a U87, than a MXL 2001. In this case, the 3 micron K67 capsule will probably sound good enough to keep. Putting the Grand total at $125-145 with an AMI T14.

Any of those options could include the ever so popular option of capsule replacement: Swap the 3 micron 32mm K67 for a 6 micron-34mm K67, a K47 or C12 for an extra $40 (next group buy) - 115 from someone like Dave at Advanced Audio.

Someone, please check my tracing, before I attempt to draw a schematic from the PCB.

Any thoughts, anyone?

 

[guitardick]

The following photos, are from a different orientation. Instead of the header being on the bottom like the last set of photos, I turned The mic 180 degrees to see the PCB from a different angle.