first tube rolling: expert advice needed - take 2

Annoyingly my first thread that went under this header has disappeared. Apologies to everyone who had contributed and put a lot of thinking into this.

Here is the plot again: I had bought a second hand Unison Research Unico SE hybrid integrated amp with two Electro Harmonix 12AU7A in the pre-amp section. Very fine in musical terms, the amp caused an unacceptable (in my solid-state biassed opinion) amount of hiss and slight traces of hum coming from the speakers in silent parts. I had assumed this was caused by (perhaps defective) tubes. Not knowing where or what substitutes to start searching for, I have had the benefit of Audiogoner's advice and finally acquired a pair of NOS tubes at Machmat in the Netherlands, namely:
Tesla ECC802S unused NOS (virtually the same as Telefunken's ECC802S, I have been told, picture: see my "Guests" system).

Here is the good news: Am I glad I tried this! I am getting a cleaner and more saturated sound, as if creases had been ironed out; bass appears more finely detailed (tried this with different speakers with reproducible results)
And here is the bad news: The hiss is still there, perhaps even more disturbing than before because the music is better. Guess I'll have to have the amp inspected and probed (hope I haven't been "had"). Anyway, if it doesn't work out with this machine, I'll be looking at a full valve integrated from Unison (I do like this sound).

One tip I gladly pass on (not just to the Europeans): Mattijs de Vries of Machmat sure is someone to rely on!

Finally one question to the experts: Is there something like a burn-in procedure I should observe or time I must allow for with unused NOS?

Thanks in advance and regards
Indeed yes an unused tube requires some use to get the emmiting plates boiling off electrons in a steady equilibrium while the recieving plates acquire a coating of of oxidation. The filment wire burns in etc.
That said, let me warn you that totally black silence with tubes is a rare commodity indeed. If you press your ear to the speaker almost any tube will yeild a slight hiss. It should not be pronounced and will not get better with use. In fact hiss is more often associated with aging tubes (not old as in old stock, but with usage). If you really want total silence you will have to forgoe the splendor of tubed equipment, and return to solid state.
Being a tubophile myself, I highly prefer the glorious dimensionality (a neologism?), transparency and tone my tube preamps AND tube amps give me. I simply ignore this shortcoming and choose the quieter tubes I have.
Hiss is frequently tube related Hum rarely. Iwould suspect some other element for hum problems. For instance the well known ground loop.
A very good alternative is the opposite of the common belief that a tube pre and solid state power amps yield the essential tube amp sound. Use a totally solid state preamp of course the best being the one you like and can afford and then buy tube power amps. Alternatively an all tube integrated, which I'm heading toward BTW will be just as good in many cases. That way you will really hear how good tubes are, at least to some of us. Don't even use a hybrid pre in this manner it must be a good entirely solid state unit. I am not kidding. This phenomena is well described by my old buddy and respected audiogon member TRELJA on his website. I don't know if the Audiogon censors will allow my to tell you what the site is so e-mail me on the side.

My Mono bloc tube power amps are great BTW, but I had a once in a blue moon opportunity, to aquire a truly special integrated. There is a current review of these puppies on 6 Six Moons, Opera audio/Consonance Cyber 800 mono block amps. I may well keep these. I like them that much. The integrated is a Jadis DA-60, which, it seems is being replaced by the DA-88s. These amps are mucho dinero, approx. $10-12K+ new and rarely come up for sale used. I assume, knowing the amp fairly well, that it is because, the owners hold on to them.

Note: Consider the fact that, I am/was an old friend to the current importer/distributor of Opera Audio of North America.

BTW, I had 2 tube rolling topics deleted. For reasons that elude me they think the topic is inherently contentious and will result in a flamethrower contest. Honestly I don't see why this topic, which some people, may have strong opions about, is any different than any other post that makes it???? I will try again, last time they said I have to mention a specific piece of gear. Why? I don't know.

Hi Mechans, good to hear from you again. With regard to the hiss I hear, it's not the phenomenon you describe I'm afraid. I can actually hear it from a few meters away, definitely too much if you ask me.
Interestingly, you mention Jadis. I first heared my Well Tempered table with Jadis gear and was mightily impressed. Eventually, things would take another turn and, in honesty, I am perfectly satisfied with the Tidal amps in my main system. For the second system Jadis seems indeed too expensive (I have seen one or the other used but even then it's a lot of $$ and I'm becoming wary of some offers after what I'm experiencing with my Unison), but I'm seriously considering an all tubes alternative.
As to my deleted thread, apart from opinions on one or the other dealer, I only saw people of the same conviction exchanging thoughts. To me this thread held a lot of information and introduced me to a fascinating new field. Too bad it had to go.

I am having this same problem with my Unison Unico. Have you had any luck in reducing the hissing?

I too can hear it from meters away.
I guess the question on the Unico was actually addressed to me. I have been swapping cables, experimenting with isolation bases and moving the unit to different places in the apartment but never succeeded to get rid of the noise. Hooking up different speakers however made a huge difference. With Lua Con Fuoco Mk3 (4 Ohm impedance, SPL rated around 89db) the hiss reached the annoying level I described. With Chario Constellation Cygnus (4 Ohm, SPL 87db) the level was at a point that I could probably live with: audible in 1m, ear at the height of the drivers; to me that is, a friend told me he barely noticed anything in the ambient of a living room at daytime. I had been intending sending the Unison to the distributor for examination whether there was a defect after all, but I didn't get that far since the guy I mentioned bought the amp and the speakers from me.

Meanwhile, I got myself a Unison S2K tube integrated rated at 2x15W (an enormous difference in terms of output from the hybrid Unico SE with its 2x130W) that I'm driving the Lua with, and guess what: dead silent. I have also hooked up a couple of Zu Druid Mk4 (rated at 101db), again: silence. The S2K sports 2 ECC802S (I use NOS Tesla with EAT Cool Dampers) and 2 KT88 (presently the original Sovtek - with my fingers itching to try EAT KT88 Diamond Valves, ridiculously expensive but reportedly as good as NOS Genalex).

I'm not stating that the problem with the Unico was reducible to speaker sensitivity (there may be other tech specs that complete the picture) and I cannot be sure whether there wasn't an inherent defect on top of it (the lottery with buying used gear). But in my case the speakers made all the difference.
Karelfd: I'll have to second Mechans' take on the
SS pre and tube amps set up. I've got that set up as well,
using mono tube amps and get absolutely fantastic

good luck!
Karelfd,I have experienced the same problem that you have.I tried different tubes,speaker cables,interconnects,power cords,Spikes,cones everything you could imagine.It was only after placing a tubed preamp with a separate power supply in my system did i achieve silence.Of course nothing goes well for the audiophile, although silent I didn't care for the sound of the new preamp.
Good Luck
I just can't agree with you guys.I have a tube pre(BAT VK-30) and SS monoblocks(PSE's) and I have absolute silence in the silent sections.I also have Tesla's in my pre.
I had some serious hiss as well a while back, I later found that my 6922 pre-amp tubes had very little gain in them. I bought them from a reputable tube dealer, and I paid large for matched sections, matched pairs and high gain. I now own a tube tester and it makes life alot easier. Out of 8 EH6922 Gold Pin only 5 were showing good
EM and Gm tests , 3 of the tubes were showing "REPLACE" in Em and below the Gm acceptance grade.I decided to test my findings and bought a bunch of Tesla E88CC for a great price.
I bought 24 tubes and totally did the nines on testing them,I found 8 really high scoring tubes, and decided to test them in my pre-amp, and in conclusion I was right, the hiss disappeared.I did receive a full refund for my
EH6922 Gold pin, and never bought tubes from that outfit
again. My pre-amp and amp take a total of 22 tubes, it just made sense to have my own tube tester, to think I was going to spend my money on an AC line conditioner, it would have improved nothing, if you have bad tubes.

Hello Karelfd- It certainly sounds like "tube rush" the way you describe it. The least little noise put out by a tube in your pre-amp will be magnified exponentially. Contact Kevin here: ( He very closely screens every tube that passes through his operation, and has tubes that are designated for pre-amp use. Very knowledgable on tube equipment and possible problems. OH- nothing manufactured today even comes close to the Telefunken ECC802S(regardless of what you may be told otherwise). No one can afford to put that much effort into precise/quality manufacturing techniques nowdays. Now if EAT or KR were to manufacture a copy.....
Hi everyone. Thanks for your input! Unfortunately, I can't put some of your advice to the test as I sold the amp meanwhile (see my posting of 04.04 above).
Still, very grateful for any further thoughts you may have (I now own a fully tubed integrated :^) fortunately without problems).
Slates, your observation is quite worrying! However, I don't think my tubes were bad since I'm using the very same ECC802S Teslas in my new Unison S2K - without hiss - that I had tried in my Unison Unico - with hiss. The guy I brought them from claims they were thoroughly tested.
Then again, since the Unico is part of my friend's system now, perhaps, just for the sake of it, I can convince him to experiment a bit (although he's happy with its performance, I must add).
Hi Karelfd,
In my situation my pre-amp takes 8x 6922 tubes, 4 of those 8 tubes are in the input stage the next 2 are for the feedback and the last 2 are from my understanding the interconnect on the back of the unit, now the 4 input tubes are detrimental , if those tubes are not tested close to perfect for all aspects, you will definitely hear the difference. I also found that if the pins don't make good contact in the socket, it will cause the tube issues, and I can only make an assumption that this could have been your problem, the tube is a strange beast once you understand it, most of your problems will vanish.
My findings are from countless hours of tube rolling and experimenting, this
is the only way to be sure, because all systems are different from one another.


For the record i've used both Telefunken ecc802s and the Tesla version of the same name.
The Telefunken is in an entirely different class, its the best of the best standing head and shoudlers above all others including Mazda Silver plagte 12au7WA 6189 which are also excellent. I've rolled through 40-50 different 12 AU7 ECC82 in my OTO SE, mullards, brimar, rca, raytheon, CBS, sylvania, telefunken smooth plate, rough plate, Ei, Sovtek, Tesla, Cifte. TJ Ful lMusic, The american CBS raytheon are nice too but the Tele 802S is simply in a class of its own.
Is it worth the money? Yes!
The 12AU7 is my favorite tube; it brings out the best in the sound of jazz. The RCA cleartop is a good choice for NOS tubes.
Hi Karel,
This post is for your friend's benefit. He should take it to a good stereo repair shop. I've got an SE that I bought used over 4 years ago and I've never heard any hiss.
I just turned it (back) on and only hear a little hiss when I crank the volume way up and put my ear right in front of the speaker. I've never noticed any hiss while listening regardless of volume. I assume you weren't driving some super sensitive horn speakers. My speakers are A.Z. Addagio's, not especially low sensitivity.
I don't have any audiophile power cleaning in place since my PS Audio Duet pooped out on me a few months ago.

PS: Glad you restarted this. I'm going to do some tube rolling.