The World's First Lampizator DAC-300B

Lukasz Fikus, final design August 2010




In my search for the best Lampizator - especially for my new digital PCB - the Fikus DAC, I have fallen into deep meditation mode and the loose thoughts and feelings have passed through my mind, and I thought - if 300B has the best midrange out there, if 300B is what some people follow like a sect, if 300B is almost the most desired tube and has most addictive sound characteristics, then I have no choice but to try to implement it in my DAC.
A quick look at the data sheet - and bingo! The paper data has all that I need to use this tube. Very easy looking implementation.

What I came up with is a simple circuit that is a basic starting point. The DAC is connected to the tube grid by wire - no resistors, no caps, nothing. Pretty radical approach.
The automatic bias sets the desired current 20 s after plugging in.
All components stay cool.
The PSU has one choke in CLC filter.
The triode has a inductor loading (not resistive and not transformer). I  Used again ideal Lampizator choke from my shop - 40 H by 2k2 Ohm by 20 mA.  It is perfect for the dynamically sounding SET config.

The DAC played well from the beginning, but after 10 minutes burn-in and warm up it started to be jaw dropping awesome.
It is very hard to characterize the sound. One of my colleagues call it mature sound. It means that the sound is not trying to impress, it is self confident, it i doing its job and we appreciate it more and more. The sound is easy, flowing with grace, it is breathing, it has not only the mids to die for but the bass and trebles as well. This is the closest I ever got to a reference vinyl sound. There is totally NOTHING digital about that presentation, and nothing is soft or rosy or sugarcoated either.

The 300B seems ideal for this job. Don't forget that we are not driving the speakers via the transformer - we are merely amplifying 0,5 V to be 2 V.  It is sort of like asking Hulk Hogan or Pudzian to lift a match-box.

All measurements confirm a stable design. Anode current of 20 mA per tube, filament current of 1.2 A at 5V, and 250 V anode voltage.

I am getting addicted to this sound and I will now build a radical commercial version, with tube rectifiers and fully dual mono supplies etc.

Meanwhile I remain sincerely yours ,
Lukasz Fikus in the state of bliss.

DAC300B


Above the prototype already singing , the 300B's are the cheapest Russian Svetlanas I could find. I wonder what the Mesh JJ's will do here.




The above shows my DIY Breadboard (available from the L-Szop) with the edge connector adapter (again - from L-Szop) and the big universal transformer  and the chokes. All this makes such project very easy. With a little help of my Friends - Marcin and Martijn - we did it from scratch to music in 3 hours.





Here is my schematics.


DAC 300B Lampizator

Half year later - an update


I made the commercial DAC with 300B
In the process I tested several tubes:
carbon Shunguang
Svetlana 300B
Electro Harmonics Gold 300B
TJ Full Music Mesh Plate
2A3 Electro Harmonix Gold
45 from USA nos.

Of all these tubes the best 300B was Electro Harmonics by a good margin. 2A3 was somewhat less dynamic ~(just a little bit) and less microphonic.
45 equalls the 300B and is much easier to apply (half heating current is needed compared to 2A3) and it is much less microphonic than both 300B and 2A3.
45 is the hardest one to get in good conditon.
Overall the differences were very small, because this is NOT AN AMPLIFIER and the operating point is on opposite end of range compared to amps.
So the common wisdom about certain tubes being this or that is useless here.


The hardest part of this project is getting the hum low enough. TRhis hum is a result of heaters being heated either by AC or DC. None of the old tricks seem to work well enough. In this application the 300B is hundreds times more sensitive to humming and microphony than in normal amp.

All the difficulties are compensated for by the gloriously analog sound.