Some transformer questions...

[GibsonGM]

Hey guys,

I'm moving into the world of tubes...have done a lot of house wiring, tube amp mod/repair and projects like that, so I am pretty aware of how to work safely (as one can be).   I'm thinking about a Tube Reactor project, and want to cobble a power supply together for tube experimentation - not sure about buying a nice Hammond dual-secondary transformer until I make something permanent.

So, I have a nice tranny my buddy gave me.  110 p, and a couple of secondary taps offering 220 and 440v. This thing can put out mucho amperage (fused to 1A tho), and these ckts require very little.  If I tie into the 220, there's the B+.   Can I put a little RS transformer in parallel with the big one from line voltage to get my heater supply?  I have a 6.3-0-6.3, can regulate the 10-something post-rectification voltage to 6v. 
How would I tie them together & establish a ground point?  It seems like a good idea, but I don't want to go trying things at those voltages and potential currents without a direction, you only get 1 shot with this stuff!

Thanks

[blindsjc]

Hi friend,
I have a PSU made like McTube project that I use to test
all my tube projects, since in my city wall voltage is 220,
this PSU have a 12V and 220V outputs that fits almost any
tube circuit, just for test. My TubeReactor first test I made
with a transformer for heaters and another for HV, they
worked without a ground connection:

wall -> Low Voltage Transformer -> rectifier -> Heaters
wall -> High Voltage Transformer -> rectifier -> TubeReactor

Again, just for test...
Sorry about bad english.
Thanks

[GibsonGM]

Thanks, sjc...so, they do not have a common ground?  Any time I simulate them with the same ground, I get errors.  I could just treat the heaters as a separate circuit (that's what the schematics seem to do).   I didn't want to introduce ground loops, hum, or interaction is all.    For a "real" build, I would buy a transformer with the 2 secondaries!  )

[blindsjc]

Yes,
My final build is planned to a transformer with 2 secondaries too,
and really, you can see the heater as a complete independent circuit,
just a bulb lamp. LOL.

After your tests tell what you think about the tubereactor sounds,
mine is amazing, man, the best tube distortion ever. Used a 220K
at second plate resitor, just to play heavy metal.

Thanks

[GibsonGM]

Do you run yours directly into your power amp?  Would running it into your amp's preamp just defeat the purpose?     This is leading towards building my own low-wattage amp )
Running out now to see if RS has a 317T for my 6v, but the 2 transformer power supply is working out!

---Edit---
Theoretically, one can dismantle a suitable transformer and roll their own...I'd like to try that someday!
If you find a supplier for the ~200V and 9V secondaries (Hammond, etc) in the US, would you let me know?

[blindsjc]

Mine is a little low volume when plugged directly to power amp,
but I think the problem cause is my PSU, its weak and final voltage
is about 150V, Bancika uses his and gets high output (I need the
final version transformer soon) with 250V.

Mine is a mod tube reactor and haves complete independent
marshall tonestacks for clean and dirty channel, the true objective
is use it like a preamp with a LM3886 power module.

I'm thinking on a bigger resistence value for the 56K resistor
before tonestack at dirty channel, but I dont know if it will change
the sound. Do you have some idea? Maybe with other resistor
I will have less signal going to ground.

[GibsonGM]

I don't know how you have it wired, but could the 2 tonestacks have something to do with the lower volume?   I still have to build this, then I will mod it!  So sorry, no suggestions as of right now....I don't think you could hurt anything by increasing the 56K, though!

I have to find those 2W resistors and 450V caps...maybe I can parallel something together to get it running soon!   Getting my power supply was the big thing - as soon as I get those parts I can start building!

[blindsjc]

Yes,
Tonestacks eats a lot of volume, you gave me an idea, I will try the
circuit without the tonestack. I have a PCB version of hotbox, if you
want I can send it to you, just send me a message.

Thanks friend

[GibsonGM]

OK, another question!    I don't have an LM7806...so I took a 7805, and used that trick of putting 2  1N4005 diodes to ground from the common terminal.  My output is now 6.3 volts...do you think that will be ok?  I tried it with an old AT7; the heaters glow...voltage sagged to 6.2v...

Thx. for the PCB offer, but I'll probably just perf it...too much work to make a board!! 

[blindsjc]

If you got 6.3 volts and current enougth for heaters is all ok.
Dont forget to tell me about the sound ok.

I'm thinking in write a method to make pcbs with white glue,
I make then this way... But there are a lot of steps and my
english is so weak... this way works great. Maybe you can
help me with english to write it.

[GibsonGM]

I would gladly help )  If you want something written into easier English, PM me and I will copy it for you.   I would learn a lot!   

I got 6.3V...then thermal shutdown on the 7805 from too much current draw.  I added a large heatsink.   Connected 2 12AX7's, and measured 1.72A!  That's a lot of current...at 6.3v, approx. = 10.5W!  The resistance of the AX7 is 1/3 that of the AT7.   I let it run this way for 1/2 hour, and all is well )   I still have to get rectifier diodes for the 200V power, I'll let you know how it turns out!   It will be a little while, though. 
Thanks for the advice! 

[blindsjc]

Thanks, I will write something and pass to you,
maybe we can post it here in the forum later for
everybody.

About the heaters, 12ax7 are aprox. 300mA for
each heater... I use 7806 too, but how you said,
with large heatsink. The 1N4007 diodes will be ok
for the rectifier, voltage is high butcurrent for tubes
are low. Thanks a lot friend.

[GibsonGM]

Looking forward to seeing your PCB process, sjc!