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Zen clone from Sweden (Read 1402 times)
Peter
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Zen clone from Sweden
04/27/14 at 22:10:28
 
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.
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« Last Edit: 04/27/14 at 22:21:45 by Peter »  
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Lon
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Re: Zen clone from Sweden
Reply #1 - 04/27/14 at 22:59:55
 
Awesome! I admire your skill to put one together and so well first time out. I'm glad you are enjoying it!
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Decware:ERR,HR-1,ZP3,CSP2+,Torii Mk III,PS Audio PWT+DS,PowerBases,PPP,AC-12 pcs, Denon DBP-A100, Denon DCD-A100,Rega RP3 +TTPSU,white belt+Exact2, VooDoo Cable:Evo,Ultra Linear, Iso-PodMapleshade:Double Heiix Plus.Samsonv2+v3 +4" platforms,Herbie's Iso-Cup
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Peter
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Re: Zen clone from Sweden
Reply #2 - 04/28/14 at 16:03:14
 
Thanks! Will post pics, I just have to post a few messages on the forum first.
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Peter
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Re: Zen clone from Sweden
Reply #3 - 04/28/14 at 16:37:49
 
Wait for it...
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Peter
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Re: Zen clone from Sweden
Reply #4 - 04/28/14 at 16:40:13
 
Almost there..
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Peter
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Re: Zen clone from Sweden
Reply #5 - 04/28/14 at 16:51:50
 


This pic was takrn just over a week ago, dry-fitting the tubes before starting the soldering.

A good piece of advice is not to rush things. I almost wired the high voltage coming from the rectifier to the negative side of the power supply. I took my time to double check before soldering anything.
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Lon
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"Love without
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Philip K. D*ck

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Re: Zen clone from Sweden
Reply #6 - 04/28/14 at 17:24:56
 
Looks beautiful! Nice work.
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Decware:ERR,HR-1,ZP3,CSP2+,Torii Mk III,PS Audio PWT+DS,PowerBases,PPP,AC-12 pcs, Denon DBP-A100, Denon DCD-A100,Rega RP3 +TTPSU,white belt+Exact2, VooDoo Cable:Evo,Ultra Linear, Iso-PodMapleshade:Double Heiix Plus.Samsonv2+v3 +4" platforms,Herbie's Iso-Cup
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dank
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pair of dual 18
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Re: Zen clone from Sweden
Reply #7 - 04/28/14 at 19:15:18
 
Peter

What's the meter metering?


Dan
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Peter
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Re: Zen clone from Sweden
Reply #8 - 04/28/14 at 22:18:49
 
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. Wink

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Peter
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Re: Zen clone from Sweden
Reply #9 - 04/29/14 at 14:54:53
 
All tubes in the amp are russian nos, I already had some 6n1p, and the sv83s are really cheap. The most expensive tube was the rectifier, a black plate Svetlana 5c3s from -61.

oh and of course it got the Hazen mod done right away.
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dank
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pair of dual 18
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Re: Zen clone from Sweden
Reply #10 - 04/29/14 at 21:41:56
 
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
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Peter
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Re: Zen clone from Sweden
Reply #11 - 04/30/14 at 08:18:28
 
Thank you very much  for your input, Dan!
I will check the voltages and report back!
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dank
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pair of dual 18
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Re: Zen clone from Sweden
Reply #12 - 04/30/14 at 12:54:38
 
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
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Peter
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Re: Zen clone from Sweden
Reply #13 - 04/30/14 at 13:36:43
 
Just checked the voltages.

Test point a, 320v
Test point b, 285v
Test point d, 2.4v.

Checked the voltage drop across the 1k first resistor in the power supply. It drops about 50v. Given ohms law, the current is 50ma.

If I want to get my voltages spot on at test points a and b I might change that one k resistor to 500 ohms. It is true about the inductor.
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Peter
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Re: Zen clone from Sweden
Reply #14 - 04/30/14 at 17:04:49
 
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
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