[happyrabbit]

Norman !

Thanks again for the insight and lovely commentary 

Currently using the free software from www.4pcb.com.   It’s really a glorified paint program.  I have had 5+ years experience to learn most of its tricks.. 

The cost difference between a 4 layer vs 6 layer pcb isn’t soo great plus it’s a DIY project.  I ended up with sig/gnd/pwr/pwr/gnd/sig configuration.  The two ground planes are tied together.   The plane pours are tied to the input ground.  I guess it’s more of a mixed signal configuration..   The input & output signal are on the top level and the bottom level contains everything else.  The power planes are sandwiched between the grounds.   This approach is new territory for me.

https://hobbyking.com/en_us/vibration-damping-balls-300g-red-8-pcs.html


The Microphonic Issue..  you might have noticed the mounting holes are huge...  I plan on using  ‘damping balls ‘ and placing the PCB in tension.  The case mounting points are offset  to achieve  a ‘mildly tensioned’ PCB..hopefully   This approach is similar to solutions found  on drone camera mounts.  I will also add a 2mm silicone pad to the bottom of the nutube with mass loaded vinyl on top.   




Dwight

[happyrabbit]

1st board built !

[happyrabbit]

Please note da Glow 

[happyrabbit]

My next attempt @ da nutube.  No more variable plate load.   Too many issues     Going to place an Intact Autoformer on the front end for attenuation.   Moved the layout around to improve cable routing.  Hopefully the muting shunt will actually work this attempt.   No more unprotected mosfets for me.  Also replaced the b+ op-amp buffer with an 7h + 220uf filter.  Similar to the Grid configuration.  The 10uf electrolytic blocking cap has been replaced with (2) 4.7uf 50v Rubycon Mu Series. Curious about the sound. 

http://www.intactaudio.com/atten.html

[aldcoll]

Please note da glow)

  I only see 1 side glowing,  is that a photo reason or??

I am interested as all getup. 

Alan

[happyrabbit]

Alan,.

One channel per board.   This is not a minimalist approach. 

Couple weeks out on the next board.

Dwight

[happyrabbit]

Round 2..    also changed the input transformer from 1:1 -> 2:1 to lower the gain from 12db to 6db. 

[happyrabbit]

[happyrabbit]

Round 3..

* 4 layer PCB instead of 6
* removed the rubycon mu film and added amtrans amcg  (dc blocking)
* 4 pole mundorf replaced with a heavy duty common mode / diff filter.
* added a cascode ccs to the Jfet voltage follower. 

Also ordered a new case to support the intact autoformers.

[happyrabbit]

Intact 47 Position Autoformers.  Thinner case.   Having issues with filament noise on the latest Build.  CCS is appears unstable with this Nutube.  Audible hiss..ugh     Ordered another tube.   I noticed a couple people on diyaudio stating ‘ hiss ‘.  I thought 💭 grounding issues. Maybe not.  See attacched

[happyrabbit]

It’s finally done and operational.      Glad it’s over 👍.  Tremendous amount of effort and $$$$. 

Dwight

[happyrabbit]

da Luv is On !    latest version.   noise finally gone !   da nutube is the bomb dot com 

Clarity CSA for the dc blocking cap.  Gotta luv purple 
Back to a op-amp buffered plate load.
Common mode & diff filter for dc supply.
Reconfigured CCS for lower filament noise. 
Leaded solder..  much easier soldering into the GND plane.