C12 with 6S6B-V triode

[Papa Tango Charly]

I would like to build a C12 with a 6S6B-V Triode and a Black Tbone PSU. I'm looking for a schematic. I have found this one. i'm wondering what are the optionals components? Do you have any other ideas? Thank you

 

[rock soderstrom]

i'm wondering what are the optionals components? Do you have any other ideas?

Yep, this is an optional RC ripple filter for a maximum clean B+ voltage. This is the last filter stage of the PSU but inside the microphone. The capacity of the cap is somewhere between 0.5-10uf (or even more, depends of the available space), the resistor needs some volts to do its job.

 

[rock soderstrom]

Some microphones have this filter, some do not. U47 for example has a 30K/1uF inbuilt PSU ripple filter.

 

[Papa Tango Charly]

Thank you do you think i could use this schematic i have found to build a C12 with a 6S6B-V triode

 

[rock soderstrom]

Yes, why not? Everyone has to decide for themselves whether this is still a C12? Perhaps the Soviet tube needs slightly different resistors at the cathode and anode? Just try it out, you have to start somewhere.

 

[HerbertR]

I would like to build a C12 with a 6S6B-V Triode and a Black Tbone PSU. I'm looking for a schematic. I have found this one. i'm wondering what are the optionals components? Do you have any other ideas? Thank you

Hello, if you are using the T-Bone SCT2000 power supply, as I have used x times for tube mic builds, you will need to reduce B+ from 180VDC to 120V. So you have to replace the two zeners (100V + 80V) with two protection zeners with a sum of 120V (example: 56 + 56, 80 + 39V...). But I have sometimes experienced batches with much noisier zener diodes, they are also not always really correct and give off a slightly different voltage you need to readjust with other "wrong" declared Zener values....... Additionally, if you have a transformer with 9.5V AC and 200V AC on the secondary (I have also heard of versions with 180V on the secondary), you will need to increase the sum of the 5 series resistors R1-R5 of the B+ part (20K+ 20K+6K8+6K8+6K8) CRCR...Filter up to a total of around 100K-130K or so which certainly depends mainly on the current draw of the tube used and the real output of the Power TX. This should be enough to provide a good stable voltage of up to about 1.2 - 1.5 mA B+. At the end the Protection Zener Diodes in the B+ Circuit should not really take over the work of the Dropping Resistors. Ohms law is the best friend... I also spent these PSUs always RFI Filters / replaced the EC PlugIn. They only cost a few bucks in China from AE (100 Percent the same as from other Electronic Suppliers...). R6 is a "Pre" Dropping Resistor for the 0-120V variable Pattern rotary switch and should be strongly reduced or bridged. It is also not a mistake to solder at the end of the R5 / first Zener Diode a extra 100-500nF Film Cap for extra Filtering against ground. If you want to underheat a Tube as example from 6.3V to 5.9V DC what I did on my M49 mics with Mini 5840W Tubes to improve lifetime and add a kick more harmonics then try to solder for a 6S6B Tube a small insulated-shrinked "flying" 2-3 Ohm Resistor with at least 0.25-0.5W between 7Pin XLR Connector and the cable of the 7Pin Dupont Connector. These cheap 50 Buck PSUs are a super starting point for Tube mic projects....

 

[ZHOUJUN]

After I modified a U95 power supply, I gave it to my M49 using 6C6B for testing，The B+ stepped down from 150-200V to 120V, and the heater 6.2V was directly available， It was very quiet.

 

[gyraf]

..don't use "filtered" power inlets unless absolutely necessary (smps etc.) and you KNOW that it is always going to be grounded - otherwise it tends to place your chassis ground at half mains voltage (at high-Z, but still). The schematic on the side shows why.

thus "this equipment MUST be grounded"

/Jakob E.

 

[Murdock]

..don't use "filtered" power inlets unless absolutely necessary (smps etc.) and you KNOW that it is always going to be grounded - otherwise it tends to place your chassis ground at half mains voltage (at high-Z, but still). The schematic on the side shows why.

thus "this equipment MUST be grounded"

/Jakob E.

Interesting. Haven’t thought about that. So you mean because both L and N going to chassis through these capacitors?

 

[gyraf]

yep

 

[rock soderstrom]

Interesting. Haven’t thought about that. So you mean because both L and N going to chassis through these capacitors?

Yes, interesting. I'll have to think again about it what that really means. My chassis are always grounded, at least when I use such power inlets. Then everything should be ok, right?

 

[Murdock]

yep

You mean mains PE should always be tied to chassis with these Filters? 0V/Signal ground could still be floating?

 

[HerbertR]

..don't use "filtered" power inlets unless absolutely necessary (smps etc.) and you KNOW that it is always going to be grounded - otherwise it tends to place your chassis ground at half mains voltage (at high-Z, but still). The schematic on the side shows why.

thus "this equipment MUST be grounded"

/Jakob E.

Interesting, never heard that. First time. These EMI Filters are fully metallic and must be grounded with a metall case star ground. Thats clear, they will otherwise not work ... The clear disadvantage of these Filters is not really obvisually

 

[Khron]

You mean mains PE should always be tied to chassis with these Filters? 0V/Signal ground could still be floating?

I believe that's a legal requirement, if the piece of equipment is *not* double-insulated..?

 

[Khron]

Interesting, never heard that. First time. These EMI Filters are fully metallic and must be grounded with a metall case star ground. Thats clear, they will otherwise not work ... The clear disadvantage of these Filters is not really obvisually

https://en.wikipedia.org/wiki/Film_capacitor#Safety_capacitor
What happens if the (metallic / conductive) chassis is not properly earthed, or the mains connection does not have an earth contact? Capacitors "conduct" AC...

 

[Murdock]

I believe that's a legal requirement, if the piece of equipment is *not* double-insulated..?

Yes, that's also what I thought. But there was a discussion somewhere else which I probably mixed up. There it was about floating signal ground/0v.
So yeah, chassis should always be tied to mains PE.
But are these EMI filters in other ways "bad" or not advisable to use?

 

[Khron]

But are these EMI filters in other ways "bad" or not advisable to use?

Only if the device ends up getting plugged into a non-earthed mains socket. Then, via the 2-4 Y-class capacitors in said mains filter, the chassis could end up floating around half-mains-voltage. Those capacitors (sub-10nF) can "only" pass single-digit mA currents at 50-60Hz, but that'll still be noticeable...

 

[tomas.borgstrom]

I would like to build a C12 with a 6S6B-V Triode and a Black Tbone PSU. I'm looking for a schematic. I have found this one. i'm wondering what are the optionals components? Do you have any other ideas? Thank you

The bias in the schematic you posted will work fine with 6s6b-v. I don't know how it will match T14 soundwise. You will get closer to the C12 sound with a high quality low noise old stock ECC81 and the original schematics with fixed bias. The capsule will as always be the most determining part.

 

[RuudNL]

I had to use a desktop computer on a not earthed mains socket. (There simply wasn't an earthed mains socket in the room.) There used to be about 115 Volts on the enclosure...

 

[Mr. Moscode]

I have a C12 PSU for sale. PM me if interested. 1 complete and 1 partially hacked up.