Decware ZKIT-1 model SE84DIY

[henry4841]

Found this on the diyaudio forum and since there is so much talk of Steve's little amp I thought members on this forum may want to try and build one for themselves. I have built one on another published schematic which I have shared on this forum in the past but not this one. 

 

https://www.decware.com/newsite/ZKIT1.pdf

[KT88]

So it is this one?

 

https://www.decware.com/newsite/SE84CDIY.htm

[henry4841]

I've seen that years ago but not sure if it is still available. But I have not searched Decker's website for it. I would not build from a board anyways but nice to have the schematic if one chooses to build point to point. 

[tube fanatic]

This amp features Deckert’s Hazen grid wiring which connects the suppressor to the cathode through a capacitor (normally it is connected directly).  I have never tried it to see if it produces the claimed results.  You can read more about it here:

 

https://www.decware.com/newsite/paper146.html

 

Maynard

[82 Cornwalls]

https://www.decware.com/newsite/paper145.htm

[henry4841]

7 hours ago, 82 Cornwalls said:

https://www.decware.com/newsite/paper145.htm

Sounds like someone on this forum needs to do some testing and post their opinion of the added cap. Maynard first pointed this mod out to me probably years ago but refreshed my memory a few days ago. I may experiment adding the cap to the suppressor myself as soon as it gets too hot for an old man to work outside here in the deep south of Alabama. Deckert seems to be sold on the advantages. 

[mark1101]

If I'm reading the article in blue correctly, that connection was suggested back in the 30s.  Although the article never specified how it changed the sound.  Just redirected the secondary electrons back to the plate.

[henry4841]

Redirecting the electrons back to the plate is the job of the suppressor grid which has almost always been connected to the cathode of the tube which is negative that repeals the electrons which are bombarded off of the plate by the force of the electrons from the cathode striking the plate. I have not read or studied the articles of using a cap but it seems to me an isolation cap makes the suppressor grid floating. Apparently it still repels the loose electrons from what is said. Theory escapes me but the articles say it improves the sound. Subjective I know but who knows if one does not try.

 

 

[kevinmi]

I built a couple of these kits years ago with the Hazen mod board, but have nothing to compare the sound to without the mod. I haven't listened to them in years. Maybe I'll do a comparison with my Dennis Had Inspire amp and my Cary 300se monoblocks.

[henry4841]

I have been giving this mod some more thought especially on the Decware Zen using an EL84 tube vs the 6P15P tube. The biggest difference between the tubes is that in the EL84 has the suppressor grid tied to the cathode internally so in effect you will have a cap across the connection and not isolated from the cathode  by a capacitor as in the 6P15P tube where the suppressor grid is not tied internally to the cathode. All the published schematics of the Zen I have seen this is not shown and Steve does not mention if he ties the two, G3 and K pins together as sent to customer. It makes sense to me since the amp is supposedly built to accommodate both the EL-84 tube and the 6P15P tube to tie the two pins together. It will not matter in the EL84 since the pins are already tied internally but will make a big difference, technically, using a 6P15P tube where a cap will isolate the suppressor grid "g3" from the cathode "k" if the two pins are not tied together. 

 

Thoughts, any of our electronic nerds on this forum? Perhaps maybe an owner of the Zen taking a look inside to see if Steve sends the amp out with the pins tied together. 

[82 Cornwalls]

Yes, a 0.1uf cap between 3 (k) and 6 (g3) for 6P15P tubes.

[henry4841]

8 hours ago, 82 Cornwalls said:

Yes, a 0.1uf cap between 3 (k) and 6 (g3) for 6P15P tubes.

But then in effect the g3 is floating and it's purpose is to suppress the electrons knocked off the A making it useless as if it was not there. That and with the EL84, the tube the amp is actually built for, the cap is bypassed internally as if the cap is not there. Contradictory is the word that comes to mind. Steve is the only source I have ever heard that claims the cap is an improvement in sound but actually admits he does not understand how. What I would like to know is if Steve connects the g3 to k in the amps he sells where the 6P15P is like the EL84 tube. His published schematics do not show this but then his published schematic uses SS rectification whereas the ones he sells uses a tube with pleasing distortion is what I call tube rectification which is actually why many prefer a tube amp with tube rectification. 

[82 Cornwalls]

I thought I already answered that.

 

Some that have tried it say they hear an improvement, some say they don't.

 

https://www.decwareproducts.com/se84ufo

Model SE84C+  -  2009 ~ 2012

The color was changed to white, the binding posts were also upgraded and the circuit was further tweaked with the CCE mods dealing with the suppressor grids of the output tubes further improving transparency at these lower voltages.

 

 

https://www.decwareproducts.com/se34i-6

Model SE34I.2+

Manufactured from 2009 to 2012.
The output tube section was upgraded with the Hazen Grid Mod pushing the performance and fidelity of the EL34 a bit higher. 

[82 Cornwalls]

 

 

Look closely at the power tube sockets; EL34  pin 1 - g3, pin 8 - k.

This is the P/P U/L Torii Jr II

[OO1]

14 hours ago, henry4841 said:

 Contradictory 

 

[82 Cornwalls]

6 hours ago, henry4841 said:

That and with the EL84, the tube the amp is actually built for, the cap is bypassed internally as if the cap is not there. Contradictory is the word that comes to mind.

 

Yes the amplifier was originally designed for the EL84 tube, and while it will operate fine with them, Decware has been recommending and shipping it with 6P15P tubes since 2009 (maybe earlier). Decware doesn't even keep EL84 tubes on hand for new amplifiers or as replacements.

 

I fail to see a contradiction, an owner is free to use the tube he or she chooses and therefore can take advantage of the mod if they feel it makes a difference or ignore it if they hear no difference.

[tube fanatic]

Keep in mind that the suppressor is only needed for pentode operation to keep the secondary electrons away from the screen.  Since the screen is tied to the plate in this amp, I think we are dealing with an academic point (obviously, triodes don’t have a suppressor since one is not needed).  So, it can’t hurt to have the mod in place as it will have no effect with the EL84 in the socket.  If anyone builds one of these, it would be an easy matter to put a switch across the cap to allow instant comparisons while the music plays when using a tube with the suppressor brought out to the socket.

 

Maynard

[henry4841]

1 hour ago, tube fanatic said:

Keep in mind that the suppressor is only needed for pentode operation to keep the secondary electrons away from the screen.  Since the screen is tied to the plate in this amp, I think we are dealing with an academic point (obviously, triodes don’t have a suppressor since one is not needed).  So, it can’t hurt to have the mod in place as it will have no effect with the EL84 in the socket.  If anyone builds one of these, it would be an easy matter to put a switch across the cap to allow instant comparisons while the music plays when using a tube with the suppressor brought out to the socket.

 

Maynard

I am considering building another SE EL84 amplifier and my thoughts are the switch to see just how it actually effects the sound. As far as Steve sending the amp with 6P15P, my thought is price. The 6P15P was not designed as an audio tube but rather as a video frequency voltage tube but can be like many other tubes built for another purpose can be used as an audio tube. They use to be cheap on Ebay but like all tubes the price has gone up. 

[82 Cornwalls]

Steve started using the SED SV83/6P15P-EV because it is a video tube which he believes is better due to the extended bandwidth and speed. After trying it with the "mod" Mr. Hazen came up with, he liked them even more. 

 

Quote from Steve on his forum: "6P15P-EV have always cost a lot more than 6P15P."
 

[henry4841]

But much cheaper than a NOS EL84. I have a PP EL84 amplifier I built and I am using the 6P15P-EV's instead of EL84's mainly because of cost. Hey they sound really good and all you have to do is tie the K to G3 and you essentially make a EL84 or 6P14P which is the Russian answer for the EL84 electronically. Both the 6P15P-EV and 6P14P are NOS tubes from Russia made when tubes ruled in Russia.