EL84 shoot-out !

[Thor61]

Can anyone comment on the sound quality, or there personal experiences of various EL84 tube types and/or there equivalents when used in or with the "ST35" circuit or pcb ?

[Ty_Bower]

I've used mostly Russian 6pi14pi tubes and their variants (-EB, -K, etc). I think they sound good to me. There is a fair amount of feedback (~20dB) designed into the circuit, which I believe reduces some of the differences in various manufactures of tubes. I a small collection of random Philips tubes from assorted factories. I might be able to assemble a quad and see if I hear any differences.

I seem to recall some guys over at AK tried out some different flavors of tubes in their 6BQ5/EL84 amps. Maybe you could search up an informative thread?

Before I spent a lot of dough trying out different EL84 types, I'd play with the 12AX7/12AU7 combo in the front end. You'll hear some subtle but definite changes depending on the tube(s) you put there. Many people seem to like the 5751/12BH7.

[Thor61]

Do you know of a good source for the Russian 6pi14pi that's reasonably priced and doesn't take forever to receive ? I once ordered some 6n1p's for a headphone amp it took 4 - 5 weeks before receiving them. Was told the problem was because customs had held up the order ect... ????????

[Ty_Bower]

Nope. They come from the Ukraine, and take forever to arrive. Unless, of course, you were foolish enough to order a lot of eighty of them once upon a time. Then you just make a trip down to the basement and take out whatever you need. :)

[EWBrown]

I haven't yet tried them, but I've been told that the 6P14P-ER is the best sounding variant, got that from Kevin Kennedy and others who have tried them out. IIRC, the -ER is the >10K lifetime hour variant, prehaps not as common as 6P14P, or 6P14P-EV

Shipments from former USSR nations can be as short as ten days, and as long as 45 days, usually 17-21 days is average. I have two cobalt blue "Neman" glass insulators enroute from Belarus, the usual delivery time is 2-3 weeks, but these have been "en route" since Jan 31. The seller over there recently checked the "RR" Russian tracking number, and she says that they have arrived in USA a few days ago, so it looks like it's up to US Customs, and the USPS now...

The Belarus insulators finally arrived after a total transit time of fifty days. Seems that some highly efficient, well trained, diligent person at US Customs in NY decided that they should take a short side trip to Lima, Peru, rather than directly to North Carolina.

D'Oh...

/ed B

[Thor61]

Thanks guys ! I was kind of hoping to pull a rabbit out of a hat on the time frame. But considering the price, patience is gonna win this one ! Do either of you have a second choice preference something available from in the USA ? I always like to have a back-up plan, Murphy's Law seems to be my albatross ! Again Thank-you.

[Ty_Bower]

I hear good things about the JJ EL84 tubes, although I haven't tried them myself. Just shy away from the JJ octal based tubes. There's too many reported QC issues.

[Thor61]

I have been looking at them for a while, found them for $ 40.00 matched quad. Does JJ make all there tube's in the same plant ? When I received the the Heath-kit SA2 from which I'm now using the transformers out of, It had Original Mullard El84's. They look very old and have some kind of black oily substance on the inner glass near the mica insulators. I have no way of testing them ! Do you know what can cause that type of thing inside a tube ?

[Ty_Bower]

Do they look like the two on the right?



That's what Mullards do. It's completely normal, and a reassuring indication that you've got genuine Mullard EL84 tubes. They usually test strong and last long, too. Enjoy them.

[Thor61]

As always your reply's are continued source of inspiration ! Good thing I held on to them, my girlfriend wanted to embed them in liquid acrylic to make a paper weight. I would still like to some how test them! Any advice as how to do so with simple equipment or maybe a link to provide the needed answers ? For what its worth on the top just below the chrome area it says " 6BQ5/EL84 GT.Britain" the getter is round and the inner plate area is gray with 2 ribs having a hole in the center. Can almost make out some kind of diamond looking logo and half spelled Heathkit all writing is a lite gray color. Also on top of the tube there are what looks like casting lines. EDIT: Actually very much like the 2 on the right in your pics !

[DeathRex]

For the price, I like JJs, I have a set in a Emud 1210. I've ordered a set of 6P14P-EVs and 6N1Ps. Plan to use the 6P14Ps on a Heathkit AA-151. Might be a month before I get them though.

[Mossback]

Mullard EL84 tubes are outstanding in every way however the cost and availability is an issue.
I agree with the others here that the USSR surplus tubes sound good after 200 or 300 hours. You need to find the ones made no later than the early 1980’s. What you look for are a gray almost etched lettering. It will include a date and the letters OTK. Only use the OTK tubes the pins will look plated not dull. The red print dull pin tubes are consumer grade and are trash. The OTK’s will take a beating and not even break a sweat.
I use the reissue Gold Lion tube myself its as good as the original Mullards. Some of the Holland tubes are good as well as BEL made in India with the Mullard tooling. I own a few quad of NOS matched BEL and Mullard but find the Gold Lion every bit as good.

[Quad]

Since this OTK thing keeps popping up - OTK
loosely translates to "inspected by" with the
number following it identifying the inspector or inspection process.
It just seems to indicate "QA passed".

Quoting Wavebourn (I believe he is Russian) on diyaudio:
OTK label means an ordinary QC, i.e. Отдел Технического Контроля that exists on any enterprise. Rhombus or a star with a letter in it means Приёмка Представителя Заказчика, i.e. Defence Ministry QC.

It's funny - I scoured the market here (Hyderabad, India)
and can't find any interesting BEL tubes (GZ34s, EL34, EL84).
Looks like they have been cleaned out by ebay bounty hunters
or I am not looking in the right places.

[EWBrown]

OTK, which is the initials for Отдел Технического Контроля translates to Bureau of Technical Control, which means that these tubes are of higher quality, and are subjected to more rigorous testing standards, than the run-of the-mill "consumer grade" tubes, which are generally the cheapest productions, and assorted "rejects" from higher level QA testing. The "Diamond" (Rhombus) shape indicates a higher order of testing standards, for Mil-Spec or Critical Industrial standards.

Отдел Технического Контроля sounds like "Otdyel Technicheskogo Kontrolya"

/ed B

[DerekVa]

Nope. They come from the Ukraine, and take forever to arrive. Unless, of course, you were foolish enough to order a lot of eighty of them once upon a time. Then you just make a trip down to the basement and take out whatever you need. :)

I guess I know who to bother about local (US) sources of 6pi14pi tubes now. ;-)

-D