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. 8)
That 'ring' around the connection means to do it with shielded wire and ground only one end.
Fp
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]
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?
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
Thanks Fp. 8)
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. 8)