[lcrim]

A few weeks ago I rejoined the Decware site to learn more about this mod.  The basis for the mod is that in certain true pentodes the suppressor grid is not internally connected to the cathode. The two pentodes that concerned the Decware crowd are the EL34 and the Russian 6P15P-EV.  It seems that by connecting the suppressor grid to the cathode via a low value ( 0.1uf 400V) polyester film capacitor which are non polarized,  astounding performance gains are possible. 
I was able to get the caps last week for less than a $.15  apiece and soldered them in place.  At that point I owned a decent collection of EL84 tubes collected over the years, unfortunately the internal configuration of EL84's doesn't benefit from this mod as its suppressor grid isn't separated internally.  I had ordered some inexpensive 6P15P-EV's from an Ebay seller in the Ukraine.  They arrived today.
The difference is night and day.  There's more power, coherence, punch, better mids, better extension at the frequency extremes.  The clarity and detail are improved as well as the dynamics.
In short, the best tweak I've ever encountered in this hobby.  Inexpensive, effective and no trade offs.

[planet10]

...true triodes the suppressor grid is not internally connected to the cathode. The two triodes that concerned the Decware crowd are the EL34 and the Russian 6P15P-EV.

You mean pentodes. The 6P15P-EV os also known as SV-83

dave

[lcrim]

Thanks for the sharp eyes.

[lcrim]

Here's a link to the Decware site http://www.decware.com/cgi-bin/yabb22/YaBB.pl?num=1243915681
This mod also works for the EL34 tube family.
The lack of interest for a tweak that can transform your amp is difficult to explain.

[djn]

I just recieved 2 6P15P tubes for my Zen amp and the .1 caps are in the mail from PE.  I am looking forward to this mod as I run my Zen amp all day while at my desk.

[lcrim]

Please check back with your results.

[nature boy]

I had the Hazen mod done to my Decware Zen SE84CS w/ EX mod and found the same results with the SV-83 tubes.  I was previously using Genalex EL-84 reissues in the amplifier.  I prefer cryo'd SV-83 tubes over the standard SV-83's, just a little clearer sounding to my ears.

NB

A few weeks ago I rejoined the Decware site to learn more about this mod.  The basis for the mod is that in certain true pentodes the suppressor grid is not internally connected to the cathode. The two pentodes that concerned the Decware crowd are the EL34 and the Russian 6P15P-EV.  It seems that by connecting the suppressor grid to the cathode via a low value ( 0.1uf 400V) polyester film capacitor which are non polarized,  astounding performance gains are possible. 
I was able to get the caps last week for less than a $.15  apiece and soldered them in place.  At that point I owned a decent collection of EL84 tubes collected over the years, unfortunately the internal configuration of EL84's doesn't benefit from this mod as its suppressor grid isn't separated internally.  I had ordered some inexpensive 6P15P-EV's from an Ebay seller in the Ukraine.  They arrived today.
The difference is night and day.  There's more power, coherence, punch, better mids, better extension at the frequency extremes.  The clarity and detail are improved as well as the dynamics.
In short, the best tweak I've ever encountered in this hobby.  Inexpensive, effective and no trade offs.

[Listens2tubes]

Guys, I just read all the info on the Decware link Larry posted. The white papers, then, the 5 pages of comments. Very informative I  will do this mod to my Dynaco MkIV amps and report back.

[Listens2tubes]

Doin' some more reading I found this more recent post http://www.decware.com/cgi-bin/yabb22/YaBB.pl?num=1278169698 seems to be continuing to excite

[JohnR]

The lack of interest for a tweak that can transform your amp is difficult to explain.

Perhaps a better title would have helped...

[TheChairGuy]

The lack of interest for a tweak that can transform your amp is difficult to explain.

+1 above for JohnR.

Old marketing adage: Sell the sizzle and the steak sells with it

John

[lcrim]

I'm not trying to sell anything.  I find that kind of presentation on a hobbyist site out of character, at least for me. 
I presented what I thought to be a very valuable tweak and it was ignored. 

It may be that I'm totally wasting my time here as the makeup of the membership has changed in character. 

[DaveC113]

I have a tubelab SimpleSE running wingC el34s I'm going to try this on.... one of these days 

[scitizen17]

I normally run KT88 in my SE amp, however I wanted to try this mod and see what the hype was all about. I installed a 0.1uf 630V Wima MKP between pins 1 & 8 and ran my EH EL34s for a while. To me, a several of my co-workers, the highs sounded muffled and maybe even a little distorted. To confirm this I jumped out the cap on one channel, and clearly (or unclearly) the caps muffled the high end on the channel with the cap. I didn't even bother breaking out the scope to check it out. Needless to say I removed the caps and put the jumper back between 1 & 8.

This mod did not work in my case.

[TheChairGuy]

I'm not trying to sell anything.  I find that kind of presentation on a hobbyist site out of character, at least for me. 
I presented what I thought to be a very valuable tweak and it was ignored. 

It may be that I'm totally wasting my time here as the makeup of the membership has changed in character.

Larry,

All hobbyists are busy humans...with precious little time to glance at the wealth of information available to us all 24/7 in the internet age.  I didn't know who 'Hazen' is and I'm sure others don't either....frankly, the only reason I even checked into it was because I saw you had posted it so I thought it maybe worthwhile.

Perhaps a modest change of title to The Hazen mod - a great upgrade for your Decware! would reel several more hobbyists into this topic.

Regards, John

[DaveC113]

I normally run KT88 in my SE amp, however I wanted to try this mod and see what the hype was all about. I installed a 0.1uf 630V Wima MKP between pins 1 & 8 and ran my EH EL34s for a while. To me, a several of my co-workers, the highs sounded muffled and maybe even a little distorted. To confirm this I jumped out the cap on one channel, and clearly (or unclearly) the caps muffled the high end on the channel with the cap. I didn't even bother breaking out the scope to check it out. Needless to say I removed the caps and put the jumper back between 1 & 8.

This mod did not work in my case.

What amp are you using?

I have not tried this mod yet because I'd have to cut a trace on my pcb... which I'd rather avoid if it's not going to help...

[rivieraranch]

I recently bought a brand new DECWARE TABOO that had the Hazen mod. With the 6P15P-EV tubes it sounds a lot more spacious and open than my previous TABOO did with EL84 tubes, and my old TABOO was wonderful in its own right. I did not believe that the Hazen mod would sound as nice as it is. It has a real impact on the depth of the soundstage and clarity of the presentation. This is not something to be scoffed at.   

[Frank I]

Here is what I am finding with this tube. I tried Sylvania blackplates which sound very nice in the amp. The Genelax reissues EL84 which is not as lush as the Sylvania and I just swapped back in the oruiginal tube Steve Deckert designed the Hazen Mod taboo and this tube is by far much better than both the other two tubes. Sometimes we try other stuff and do not realize the manufacturer may know what going to work best in the amps. Using this with the GE12BH7 it is more easier with a smooth overtone which is why I love tubes to begin with and yes it appears more power. Kudio to Decware

[chrisby]

A late follow up on the subject - the 6BQ5 / EL84 / SV83 family is not the only power tube on which this mod works wonders. But it won't elicit any improvement on types that have internal connection from suppressor grid to cathode. 

I've added it to a couple of P/P amps - DIY EL84 and already modded Jolida EL34 and liked it enough to keep them both that way.
 
Mr Eddie Vaughn (Carina) built me a custom EL34 SE triode amp about a year ago - after experimenting with the Hazen mod, he highly recommended it be included in the build, which was certainly enough validation for me.