Tube mic with pops and clicks

[arsmusic]

I have a M49 clone. It is brand new. This company makes 2 different types of power supply's for their mics. A mass produced one and a hand made type one. Mass produced has a normal transformer and regular pcb. The higher end one has a toroidal transformer and a higher quality thicker pcb.

The place shipped it with the cheaper power supply. The mic and cheaper power supply works fine. I then noticed it did not have the right PS and contacted the manufacture. They send me a new one. The new one seems to have jitter in it. Like crackling maybe twice a second or so. Quiet but it is there. I contacted them again and they send another PS and is is exactly the same. Sounds like jitter. The cheaper PS works fine. Weird. Could this be a problem with the mic? The manufacture is sort of a pain in the ass to deal with. I bought it on eBay and have the buyer protection that is the only was I was able to get a new PS. The case closed in 13 days or so so I do have to act fast. I really do know know what to do here.

The mic has a sub-minature tube (6S6B-V tube).  So, I cannot take it in and out and see if that solves the problem. 

It is just very bizarre the cheaper PS works perfectly fine but the 2 more expensive PS have pops and clicks in them.  I measures the voltages from the cheaper PS and the more expensive ones and they are very close but slightly difference.  I wonder if the difference is not giving enough of something to the mic.  Hence causing the pops and clicks.

 

[Khron]

Photos of the insides of the PSU(s)? Sound samples?

PS: Autocorrect strikes again? Surely that was supposed to be "toroidal", not "tripodal"

 

[arsmusic]

Here is a drive link with pics and audio samples. 

Uploaded 2 files with 20 db gain so you can really hear it.  It is subtle but imagine 20 tracks of that will add up quite a bit.

https://drive.google.com/drive/folders/1biBWKfKxfMo4t6h0l4HtLzGLSwzaee0F

I have two of the better power supply's with pops and clicks.  I only opened one and took pics.  I do not see and bad caps myself.  I measured the voltage a week ago or so.  They were very similar.  Say it one PS was 122.4 volts at pin 1 the other was maybe 120.3 at pin one.  Then similar differences on the other pins.  Less that a 2% difference.

And, yes I meant toroidal not tripodal stupid auto correct does not know what toroidal  is.

 

[RuudNL]

If it has a problem with one power supply, but works fine with another power supply, the microphone itself doesn't have a problem IMHO.

The "cheap" PSU looks like a typical 'el cheapo' Chinese power supply.
The 'better' PSU looks it has the +HT regulated.
It would be interesting to check if there are any spikes on this +HT. (Oscilloscope.)

 

[arsmusic]

How would I check for spikes on a oscilloscope?  Would I just measure the dc voltage of the outputs?  It is very strange the 2 "better" power supply's have the exact same problem.

 

[RuudNL]

Couple the oscilloscope for AC, eventually through a 0.1 uF capacitor. (To the +120V line.)
Use a relative high sensitivity, like 1 Volt/div.
In an ideal case, you should only see a flat line.
But if there are 'spikes' on the +HT, you will see them.

Maybe there is a design error in the "better" power supplies? (And nobody has complained...)

 

[Tubetec]

Could the toroid be coupling  unwanted mains garbage from primary to secondary ?
maybe the EI transformer is better in that respect .

Ive had that induced clicking thing going on before to, maybe check how the two psu's vary with regards chassis, ground and audio ground return , Ive a feeling sometimes a short unintentional loop can induce RF weirdness into  the audio path .
check how the heater supplies are grounded , maybe theres a difference from one supply to the other .

 

[ComodoComplex]

Yeah truthfully, the "cheapo" power supply looks like a better, more thoughtful design. The supply is a simple RC linear design, which should honestly be fine for this application.

The "nicer" one doesn't even have a heatsink on what I assume is the 6V filament regulator, which is technically ok if it's dissipating less than a watt, but still good practice to have one for long life. Since the "nicer" one has a regulated supply and the designer overlooked the heatsink as I mentioned, it's also possible they forgot to include over-voltage protection for the B+ voltage regulator which is needed during start-up. Is the chip a TL783 or LM317HV? Or just a standard LM317?

 

[arsmusic]

Thanks guys, I can try testing the PS with the oscilloscope tomorrow.

 

[arsmusic]

Couple the oscilloscope for AC, eventually through a 0.1 uF capacitor. (To the +120V line.)
Use a relative high sensitivity, like 1 Volt/div.
In an ideal case, you should only see a flat line.
But if there are 'spikes' on the +HT, you will see them.

Maybe there is a design error in the "better" power supplies? (And nobody has complained...)

What exactly should I be connecting the oscilloscope probes to when testing the power supply?  Should I connect them to ground then to the dc outputs (there are 3 dc outputs 120v, 56v and 6v or so)?  Where should the 0.1uF capacitor be?