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My SE84CDIY Clone (Read 2777 times)
Alvaro Oliver
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My SE84CDIY Clone
08/28/17 at 17:24:17
 
Let me introduce you to my clone for Zkit1 or SE84CDIY.
















This amplifier was built based on the schematics available for the ZEN Kit # 1, but I've also added the CCE mod and the bias selector switch from the Select model.

Instead of using the kit's PCB, I preferred to wire it point-to-point using home made turret boards, taking care of separating well the power supply from the audio inputs and outputs stages using a three-star grounding scheme. Connection to the chassis was done by means of a loop breaker circuit, with a 22nF cap (x2 rated) and a 50 Ohms parallel resistor. Since I don't own an original SE84C to compare, I can´t tell how much these changes had contributed but the truth is that it is a very quiet amplifier.

For the power transformer the Edcor XPWR172 was used, which is made for 220 VAC instead of the 240 VAC from the suggested model XPWR066-240.

As for the sound, after 24 hours of operation this thing shows a spectacular performance, with a gian 3D soundstage and incredible dynamism, especially with the bias selector forward (2.7 KOhm).

This amplifier comes to replace my beloved Denon POA-1500 power amplifier (a 150 Watts SS monster) and, to be truth, now I know I don't need more than the 2 Watts this system provides to fluently move my Pioneer HPM-100 speakers (92.5dB), together they make an excellent match and the Improvement in clarity and scene is shocking.

I would like to add that power can be greatly enhanced when using a preamplifier. In my case I use my Denon PRA-1000, which is very transparent and allows me to add those extra decibels to the reproduction of my vinyls.

Finally, I want to especially thanks Steve for making his designs available and for answering my questions here in the forum. This is my first valve power amplifier and it could not have come true without Steve's generosity. Clearly I will go for more soon.


Greetings from Santiago de Chile.
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Lon
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Re: My SE84CDIY Clone
Reply #1 - 08/28/17 at 17:32:07
 
Very nicely done! Felicitaciones!
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HR-1,ZP3,ZTPRE,ZBIT,ZROCK2,SE84UFO3-25th, CSP3-25th;PS Audio:Soloist SE,DMP+DSD,P10, PowerBases,XStream Statemt spk cb,AC-12 power cds;Mapleshade:SamsonV2+V3;Oppo UDP-205;VooDoo Cremona +Amati,Iso-Pods;Aurios;MD90-T SE tuner; headphones: Oppo PM-1,Sennheiser HD800
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Lonely Raven
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Re: My SE84CDIY Clone
Reply #2 - 08/28/17 at 20:33:23
 

That's some really clean looking work! I love the labels and all!

I'm Glad you're enjoying it!
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4krow
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Re: My SE84CDIY Clone
Reply #3 - 08/29/17 at 02:33:19
 
 This is the level of product that I would like to produce someday. I have no apologies for what I turn out now, yet when I see this attention to detail, that becomes a reminder as to what a bit more time on a unit becomes. Point to point is the way to go, and the heavy duty yet appealing use of materials chosen, make me a believer.
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Decware 34I.3 integrated amp/Forte' 3 bass amp/Velodyne SMS-1 bass mngmnt system/Decware ZOB speakers/Audio Nirvana 8" bass drivers/Xiang Seng DAC/ LR Audio Computer/Rega Apollo R CDP/Emotiva ERC3 CDP/BPT 3.0 power cond.
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Alvaro Oliver
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Posts: 13
Re: My SE84CDIY Clone
Reply #4 - 08/30/17 at 18:44:33
 
Thank you all for your positive feedback, this encourages me to go ahead and think about future mods/projects.

One more thing, I love how Zen sounds with the bias set at 2.7 KOhms. I don't understand why it was decided to remove this selector and leave only 0.96 KOhms fixed.
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Crazy Bill the Eel Killer
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Tubes Rule !!

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Re: My SE84CDIY Clone
Reply #5 - 09/02/17 at 02:56:59
 
Hello Alvaro,

First, nice work.

Now to your question,only guessing, of course, but here goes.

I far prefer the hotter bias setting. The 2.7 k resistor sounds anemic and asleep to me. AAMOF, I prefer to run that tube hotter still ( mods required of course ) at around 5-6 ma on the 6922 types. utilizing a cathode resistor of 480 ohms.

Way better to my ears.

As I said I'm only guessing, but I would think Steve played around a lot and listened, and came up with the present operating points based upon his listening tests.

I would also think ( again, only guessing ) that Steve got a lot of customer feedback favoring the hotter operating point.

Clearly, based upon what you've done, you're capable to do the following.

Throw a 480 ohm cathode resistor on the 6922, unbypassed, and modify your PS to get 95 volts or so on the plate of the 6922.

Give a listen and see what you think.

Cheers,           Crazy Bill
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Alvaro Oliver
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Re: My SE84CDIY Clone
Reply #6 - 09/04/17 at 19:16:41
 
Hello Crazy Bill, thank you very much for your answer.

First of all, I hope my appreciation has not been taken as a negative review. I definitely agree with you, after a few days listening to more varied music I can conclude that my previous impressions were rushed. Effectively in the hottest mode you get a better sound with most styles, especially with rock. Now I prefer the quieter mode almost exclusively for jazz or more relaxed music.

I will definitely try the modifications you advise me, just to see how it changes.

Best regards,

Álvaro
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clowkoy
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Re: My SE84CDIY Clone
Reply #7 - 09/09/17 at 03:38:51
 
Nice build! Why didn't you use a tube rectifier?  Your transformer has a 5-volt tap. You could swap rectifier tubes and change the operating points of the input and output tubes. The 10k resistors and 3.3uf caps are omitted in newer Zen from 84C+. The 1k power resistor  needs to be at at least 12 watts.
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Alvaro Oliver
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Posts: 13
Re: My SE84CDIY Clone
Reply #8 - 10/18/18 at 22:28:00
 
Thanks clowkoy, I din't use the tube rectifier because I started from the ZKIT schemmatics, later I found out the SE84C schemmatic so I put the bias switch (and also the CCE mod) but it was too late for adding the tube rectifier. Anyway, I think I'm going to give it a try soon.

How is that the new models doesn't have the 10k 3.3uF network? I've been looking for a newer schematic but I can't find any.

Best regards,

Alvaro
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