Real McTube II Questions

[Paul Marossy]

Has anyone here built the Real McTube II?

I have a question about the two pots:

On RV1, do I interpret that as having the lugs 1 and 3 connected directly together? I don't understand how this would work - it looks like it would ground the signal! Is this supposed to be a variable resistor?
And on RV2, there appears to be a 100K resistor connecting lugs 1 and 3 together, right? So that would be in parallel with the 500K pot?

Would there be a problem if I used 1M pots instead?

Here is the schematic:
http://www.dogstar.dantimax.dk/tubestuf/graphics/mctube2s.gif

Any help much appreciated.  

[Fp-www.Tonepad.com]

That 'ring' around the connection means to do it with shielded wire and ground only one end.

Fp

[lightningfingers]

USE SHIELDED WIRE!!

Seriously, mine at best sounded noisy when it was on, it wouldn't even consider being bypassed until I used shielded wire. [/b]

[Paul Marossy]

Thanks. Based on my Shaka Tube experience, I was planning on using shielded cable. So, that 100K resistor on RV2, it's across lugs 1 & 3?

[Fp-www.Tonepad.com]

yes.

Look here for more info on the real mc tube (permission granted to me by Fred to make this project).

http://www.tonepad.com/project.asp?id=23

(I haven't built it though)

Fp

[Paul Marossy]

Thanks Fp.  

[Paul Marossy]

One more question:

On the schematic, it shows Pin 4 & 5 of the 12AX7 connected to the 12.6V power supply, and Pin 9 grounded. Does Pin 9 actually get connected directly to ground? I thought that normally Pin 9 is left unconnected, at least on an AC heater scheme. But does that change with a DC heater supply?

I'm almost done, I just have to get those two 33uF/160V filter caps...
I've got it in a 6"x6"x2.5" high enclosure. Since I really like the clean to mild tones, it's going to be kind of a standalone tube preamp thing that will get a little wood enclosure wrapped in Tolex or something and a little carrying handle.