MILA-1 decent build pictures

[audiophreak]

Helloooo  ;D

          I'm about 70% assembled and need some help with the i/o transformer wiring.  I also used the CM-9589 of output and looking at the data sheet :
              C6 to RED
              B- to Brown
output XLR Pin2 to Yellow
output XLR Pin3 to Orange

  .. is this correct ??

  The CMMI-10c , pretty sure I'm looking for the 1:10 option but confused on how to wire it , as well as it looks like there are two Ground wires .. one circuit - one Chassis ??

  Thanks in advance 

 

[audiophreak]

Here is a pic of my build so far  , I used Kingston's turret board  layout, I had a custom PT made , perf boarded the Gyraf G9 HT and G-Pultec heater circuit and SSL9k phantom circuit, all voltages look good so far unloaded. The PT secondaries are 220vac @ .1mA  , 2 x  9vac @ 2,0A , 12vac @ .5mA , 45vac @ ,08vac.
  Using shielded cable where possible , let me know what you think 

 

[audiophreak]

Oooopsss ... sorry I hijacked your thread  Kingston , I've referenced your build so much this has become my " Help Thread "  ;D

 

[audiophreak]

So is it?

1st stage fb
1) 22K
2) 0
3) 0
4) 0
5) 0
6) 0

2nd stage fb
1) 50K
2) 50K
3) 100K
4) 220k
5) 470K
6) open circuit

No worries with oscillations anywhere at max gain?

That was exactly how I wired them. No oscillations at any setting and overdrives easily on settings 5 and 6. When I originally built this it was the best sounding tube distortion I had ever heard but now I know better. It can be a bit on the grainy side. I have since heard and designed better plans. 12AV7 is not the best sounding tube out there. Great for linear stuff of course.

  ... ok , I'm getting closer , confused on this "Range" setup - I know to remove R18 & R19 , but is C7 still connected to the two 50k resistors in the same way as R18 & R19 ?    ... also on 1st stage " Pole 1 " are positions 2-6 (0)  is that " Open - no connection " or does it go to ( B-)  ... and position 6 on 2nd stage " Pole 2 " = " open circuit" is this " No Connection " ??

Thanks for any and all help

 

[Kingston]

Metoo listed the total resistance of the switch at each position. 0 means no resistance ie. short circuit. Up to you how to wire them. You don't have to wire them with the parallel conf nyd had. Maybe he didn't have mbb switch and wanted this safety workaround. C7 is always connected. Although technically you can omit it if you take the feedback directly from the output cap.

 

[audiophreak]

Thanks Kingston ,
                Still trying to get this strait - for some reason switches really confuse me 

  .. is this correct ??

  EDIT : removed image

 

[Kingston]

pole 2 is correct, except you don't actually need two separate 50k resistors. pole 1 isn't correct.

probably best stop thinking about poles. Try to see them as two separate switches instead. Also no one is forcing you to couple these together like NYD did.

 

[audiophreak]

pole 2 is correct, except you don't actually need two separate 50k resistors. pole 1 isn't correct.

probably best stop thinking about poles. Try to see them as two separate switches instead. Also no one is forcing you to couple these together like NYD did.

Thank you , I updated the image in my last post - is this now correct ??  - and when you say " one is forcing you to couple these together "  are suggesting using something else other that  2/6 rotary switch ? 

  Thanks again so much , really want this to be right 

 

[audiophreak]

Hi Kingston , after staring at your turret layout and NYD's Mila schematic , if I put B- to pole 1 (com) of "switch 1 " leave position 1 open ( NC) effectively leaving R20 IN circuit and then positions 2-6 to B- effectively shorting or bypassing R20 - is this correct ??  if so I will correct my posted graphic.

 

 

[Kingston]

you are overthinking pole 1 (or we could say switch 1). try again, and start literally from ground up.

 

[audiophreak]

ok - did some searching and found this quote from, NYdave " The only difference between low and medium gain mode is that in medium gain, R20 is shorted out, causing C2 to bypass the cathode resistor of V1A (thus increasing the gain of V1A)."

  so is this correct now ??

 

[audiophreak]

  well ... I wired it that way and got the first channel working, very quiet , and sounds great !!!  Range switch seems to be working correctly and thanks to your Turret layout and awesome build documentation, I have no oscillation or noise or hum/buzz  issues.

    Thanks so much Kingston .. just great stuff !! 

 

[Kingston]

That's the correct wiring indeed.

I may have mentioned it earlier but while it's handy to have the extra gain from those lower NFB settings, the distortion of 12AV7 is not that great when it's overdriven heavily.  It's only barely better than the usual (and somewhat) harsh 12AX7 guitar preamp style distortion. In other words not very soft clipping. I later did the Drive-1 design to get a preamp to cover the softer area.

Where MILA-1 sounds its absolute best is the most linear setting of all in my opinion. (switch setting 1 in your plan, NFB in several flavours at once)

(switch setting 6 in your plan has no NFB in any of the stages by the way)

 

[audiophreak]

Thanks Kingston,
                          I got the other channel up and running today, all is good , I just have to permanently wire the Power ON switch , test the DI input and finalize the front panel graphics - then spend some time with it  ;D 

    I've been thinking about some of your previous comments / suggestions , I'd like to try and put a 10k resistor at position 2 of switch 1  as listed in my graphic to maybe " soften " or make that next step a little more gradual. 

  What do you think about that or have you tried similar ?

  Been wanting to take a try at your Drive-1 for a while now  ;D

 

[Kingston]

I've been thinking about some of your previous comments / suggestions , I'd like to try and put a 10k resistor at position 2 of switch 1  as listed in my graphic to maybe " soften " or make that next step a little more gradual. 

What do you think about that or have you tried similar ?

No point in it. The first three steps are already tuned very balanced (a single step is 5 dB). You might hear a difference if you could somehow overdrive the input stage but that's never going to happen: the input transformer clips way before that point.

 

[audiophreak]

well ... it was a thought , figured you probably experimented with that , Thanks as always for your invaluable insight and help !!