Hi all! I stumbled onto decwares website some time in the late 90's and got really interested in the zen. Though I never ordered one it was always there everytime I started thinking about tube amps. This winter i started ordering parts to build a zkit1, but that quickly changed into building a se84c with tube rectifier. No circuit board or breadboard, just p2p. This is my first build, so I built the box a little bigger than neccessary, its about ten inches wide and maybe 12 deep, plus some place for the trannies.

My biggest fear was to get lots of hum. But first power up went really well, nothing went wrong, and at least with the speakers I have used so far, there is no audible hum. Will soon try it with my bigger, more efifficent speakers

And what a great little amp it is. It's sitting in my rack with just 10-20 hours on it and it just sounds better and better as things continue to burn in. The midrange is fast and very detailed just as it should be.

I decided to go all russian on the tubes. I will post pics later.

My warmest Thank you to Steve for sharing his design so I could build this little amplifier, this is serious stuff.

Thanks! Will post pics, I just have to post a few messages on the forum first.

Almost there..

Looks beautiful! Nice work.

It  is a ma ammeter...easily converted into a voltmeter, I use it as an indicator of how much current the sv83s are conducting, or bias meter. I checked the voltage drop across the 150R cathode resistor and it was just over 7V. I calculated the current to be around 45ma if i remember correctly.
My thought was that over time the tubes will weaken, and that I should be able to see it with this thing.
And hey, it looks pretty too.

Peter

I suspect 7v across the 150 ohm cathode resistor that is shared by both output tubes is too low (unless you've made other circuit changes).  Zkit1 spec says it should be 10.25v (68ma or 34ma per tube).  Your 7v indicates 47ma or 23.3 ma per tube, down 31%.  You may expect a slight reduction because the rectifier tube you are using will result in a lower B+ plate voltage than the 1n4007 silicon diodes used in the Zkit1, but I think you are too low.  

What voltage are you getting at TPA?  Should be 346 on a Zkit1
What voltage are you getting at TPB?  Should be 309 on a Zkit1
What voltage are you getting at TPD? (input tube pin 8 or 3) Should be 2.6 on a Zkit1

If all your voltages are down 30% (due to the tube rectifier vs the 144007's) you might want to think about reducing the size of the 1k 6w resistor connected to the rectifier output (cathode) to try to bring the voltages back up to where they are on a Zkit1.  The 150 ohm cathode resistor can also be tweaked if necessary.

Dan

Peter

I think that 1k 6w resistor might be replaced by an inductor if you use a tube rectifier instead of the 1N4007 diodes.  I have no idea what size or where to get the inductor.

Dan

Just quickly added another 1k 5w in parallel with the other one. Now my voltages at test point a and b are within spec, maybe off by 1-2V.
Test point d is now exactly at 2.6V.
Now I measure 7.7V  from the sv83's cathode to ground.

Better,  but not quite there yet.  ;D