Stellar CM-6 Power Supply Replacement

[Mwine]

Hi there. I had a studio burglary a few years back, and they dropped a Stellar CM-6 on the way out, but made off with the case and power supply (among 20k of other items stolen).
So today I found the CM-6 in a closet and tried to search online for a replacement power supply. The mic uses an EF806, but I've had no luck confirming if an aftermarket supply is easily available. If anyone knows of a replacement, I'd greatly appreciate it. Thanks!

 

[rock soderstrom]

Hi there. I had a studio burglary a few years back, and they dropped a Stellar CM-6 on the way out, but made off with the case and power supply (among 20k of other items stolen).

I'm sorry to hear that!

So today I found the CM-6 in a closet and tried to search online for a replacement power supply. The mic uses an EF806, but I've had no luck confirming if an aftermarket supply is easily available. If anyone knows of a replacement, I'd greatly appreciate it.

I couldn't find a schematic for the mic, but I guess you could easily adapt an existing power supply from Thomann to the mic or look around here on Groupdiy for a suitable DIY project.

It would be important to know what pinout and voltages the mic expects. Maybe one of the members here has such a mic and can provide the necessary information.

https://www.thomann.de/de/the_tbone_psu_sct_2000.htm

https://www.thomann.de/de/the_t.bone_psu_retro_tube_ii.htm

Edit: can you show some good gut shoots of the mic?

 

[Mwine]

I'll take some shots of the mic's guts, Thanks!

 

[Mwine]

 

[Mwine]

 

[Mwine]

 

[Mwine]

I believe it's a K67 style capsule. Multipattern.

 

[rock soderstrom]

The main circuit board comes from this microphone, although it has a different tube. The pinout of the microphone, cable and power supply should be very similar. This seller may be able to provide information or even sell you a suitable PSU and cable.

http://www.shuaiy.com/product02.asp?plt=72&pone=5

 

[Mwine]

Wow. Thanks for the quick reply. I'll look into that. Huge thanks.

 

[rock soderstrom]

Can you check the colour Code for the two resistors at the top of the PCB? Can't see it

 

[Mwine]

 

[rock soderstrom]

What is printed on R5?

 

[Mwine]

R5 is 200m

 

[Khron]

Looks very similar to the t.bone SCT700 / Alctron GT2B / Nady TCM1050, apart from that great big honkin' film cap.

 

[Migs 31]

The Stellar CM-6 is a great budget mic. A colleague of mine had one and I made a copy of it- it was that good/for the price. I have hand drawn schemo with part values somewhere...

As Khron and Rock said these mics share SCT700- Nady / SYT and many others Body & basics.The TungSol EF806 can be replaced by a good Mullard-Siemens-Valvo Telefunken EF86 without problem, if the original valve/tube is busted.

The generic Chinese power supply (like the one pictured) and XLR 7 pin cable will work straight away.

Just make sure you have 6.3V on pin 2 (yellow if remember well) so the EF806 is happy.

https://www.thomann.de/fr/the_t.bone_psu_retro_tube_ii.htm

PS: Google Peter Bloch - Stellar Professional Microphones (SPM)
M

 

[rock soderstrom]

The generic Chinese power supply (like the one pictured) and XLR 7 pin cable will work straight away.

Just make sure you have 6.3V on pin 2 (yellow if remember well) so the EF806 is happy.

Thanks Migs for confirming my assumption.

Someone wrote on the web that the original PSU has a B+ of 145V, which with a 1:1 voltage divider would be about 72V polarization voltage. The capsule can certainly handle that, but I would still go down to 120V B+. This would mean that the Zener diodes in the PSU would have to be adjusted. No problem.

I noticed one other thing. This mic is supposedly using a BV8 style double bobbin output transformer with 6.5 to 1 transfer factor. This is definitely not a light load for the EF86 and will limit the lower frequency range. This could also explain the rather bright sound of the microphone (which some users describe). As always, this is a matter of taste, but the EF86 is mismatched in terms of impedance. Even with NFB, which is not available here, min. 10:1 would be the more suitable load.

A better Noval tube for these impedance ratio would be an EF800 (as a triode) or an ECC81/6072a or similar. This is a mod I would try out.

 

[Mwine]

I really can't thank y'all enough for the guidance. If I, for some reason, can't get it to work with the generic power supply, I'll donate it here for someone to play with. I do remember it sounding shockingly great for what it cost. Thanks!

 

[Khron]

A better Noval tube for these impedance ratio would be an EF800 (as a triode) or an ECC81/6072a or similar. This is a mod I would try out.

That's gonna take some hardware surgery...

 

[rock soderstrom]

That's gonna take some hardware surgery...

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