If I were to get SV83, I'd get them from Steve. They cost a little more through him, but he gets the cream of the crop shipped to him, gold grids and all that. Plus he tests and matches them himself with a maximatcher setup. It takes time, but the result is a better selection of tubes.

As for the Hazen mod - I feel it adds a bit of clarity to the sound. I noticed it immediately when mine was done. If you like the sound of the SV83, then you'll love it with the Hazen mod.

IMHO, some vintage EL84 can sound "better", but I do believe you lose the hazen feature...I could be wrong though. It's been a while since I've researched it. I happen to like the SV83 myself.

Hi Lonely Raven and Lon,
thanks for your comments based on your experience.
I think my original SE84C came with the SV83,
a few years later I go the upgrade to SE84C+ (Hazen)
At the time, I did not check the model on the tube itself, therefore I can’t be sure of what model they were.
Later on when I did some tube rolling with the following tubes:
Electro-Harmonix EL84, Genalex - Gold Lion N709/EL84,
The EH EL84 was to me the best sounding tubes, lots of details and no aggressive sound, the Genalex Gold Lion is close but it’s missing the details at the top end.
However while doing tube rolling I dropped on the ceramic floor one SV83 with the consequences that you can imagine.
So, I kept the EH EL84 up to now.
But today I took the SV83 that survived the tube rolling and made a test, using it on the right channel and on the left channel, I kept the EH EL84.
I think the SV83 sounds a little better in the highs, but I’m not really sure, not easy since the two channels have different information, sometimes the cymbals are on the right side, sometimes on the left side. I’m sure you see what I mean.
Now, looking at the SV83 with a magnifying glass to confirm the model number, I was surprised to see the following number. Almost completely erased: 6U15U (The U letter in reverse, look like an N) 6N15N. (The date is 8502) no make.
Now, is it worth buying a pair of matched SV83 from Steve?
Yes, if the price is 50 USD for a matched pair.
Right now, I am in the process of moving back to my home country Canada after 20 years on planet Vietnam, so I’m sure you understand that I am not in a hurry to buy and test, especially that I am very satisfied with the sound I get from the EH EL84.
In addition the 6922 is now a EH 6922, the original was a 6H1N or 6H7N (The Russian N that looks like an upside down U)
I also have a Sylvania NOS 6922, but with my tests, the EH 6922 sounds as good as the two others, the Russian and Sylvania USA.
So, that’s it for now.
Next tube rolling will be later on this year.
Thanks for taking the time to comment.

Guy 13 on planet Vietnam,
but not for very much longer.

It has been my understanding that the original Zen amps were voiced to the Svetlana SV83 tube; however the more recent versions, such as Zen C+ and Super Zen CKC are voiced to the 6P15P-EV. These tubes are a little different from the SV83 and were made in different plants. So you might just obtain a good pair of 6P15P-EV from Steve.