EL84 Tube Shoot Out/ Rocket

[Rick]

Avoid all the New Sensor EL84 types except the Sovtek EL84M, which is their military EL84 type. The RI Mullards sound okay, but they are far from being matched directly from NS. The Gold Lions, Tung Sol, Svetlanas, etc.; all crap! Relabeled, untested, Sovteks. There are small differences in construction, but without adequate QA/QC, they suck. There are only a handful of tubes I would use from NS out of there large variety of tubes.

NOS Saratovs, Tesla Hex Plates, Rosnovs, RCAs, GEs, Sylvanias, Philips, etc. These are all good and not super expensive. All those British tubes are spendy these days.

I just got in a quad of new EL84M in today thinking they might be like the Russian 6P14P military which have been quite good actually. I'm running them in a new 30W 4-EL84 lightning with AC30 style power amp section. 2 of them lit up bright like in the early post of this thread. They actually shorted and cut the amp completely out a couple times. Then I upped the screen grid dropping resistance line with 500 ohm resistance thinking this would for sure cure it (the 100 ohm screen grid droppers are not such a great idea me thinks, not enough V drop to the screens). So I'm running 10 H choke and 500 ohms 5 watt dropping resistor to the screen grids each with their 100 ohm screen resistor. Not so, 2 of them still lit up and cut out. I put back in some old used 6P14Ps and the amp works fine. I guess they can go back to the Tube Depot. BTW, I checked all of them for shorts and emissions and all were good OK, but they can't handle much voltage at all, must be internal defects. Those old russian tubes shipped half way around the world, (they were sold as used, so who knows but check good) work much better than new EL84Ms, quality control must be down to zilch for a lot of stuff nowadays. Sheesh! Anyone know where you can get good new tubes? I've had bad new tubes of all kinds it seems, I won't use Sovtek LPS, EH 12AX7s. New JJ AX7s seem OK, but it's getting to be a real hassle to find good tubes and caps lately. It really cuts into a guys time try to sort all this stuf out when new parts come in and they are defective, worse, it starts you 2nd guessing your work and tearing stuff up for no reason when it's bad parts causing the trouble. My rant for the day...

[dartanion]

It's up to the consumer to apply QC to new tubes. If they are bad, send them back to the Tube Depot and get your money back. Again, tube testers are of limited utility. They don't put your tubes into a realistic operating condition, so they don't tell you squat. The only way to get a good set of new tubes is to buy more than you need and weed through them. Then send the rejects back for a refund.

[FYL]

It's up to the consumer to apply QC to new tubes.

Sorry but no, the reseller/distrib should fully test the tubes - by fully I mean real world tests, not a couple of useless measurements with an el cheapo tester.

End users aren't supposed to get defective stuff, or buy 20 tubes in order to get a matched quad.

[FYL]

I just got in a quad of new EL84M in today thinking they might be like the Russian 6P14P military which have been quite good actually.

The Sovtek EL84M *is* a rebranded 6П14П-EB = 6P14P-EV - same Reflektor factory, same tooling, same templates, same construction, same materials, same everything. Ditto for their EL84 = 6П14П = 6P14P.

Some NS-sourced batches can be quite poor because of sloppy production and lack of real QC. Vintage OTK models - I would say pre-1983 or so - are much better in that respect, they can still be found from Eastern European (r)etailers.

Russian suffixes:

P (Cyrillic) = R (Roman) = special quality
E = E = extended lifetime
B = V = ruggedized
K = K = vibration resistant

Russian equivalents of the EL84:

6П14П; bog standard version, large thick glass = EL84, 6BQ5
6П14П-EB; hardened version, longer lifetime = EL84M, 7189
6П14П-EP; special quality, longer lifetime = E84L, 7320 (quite rare)
6П14П-K; hardened version, vibration resistant = EL84F (very rare)

[dartanion]

It's up to the consumer to apply QC to new tubes.

Sorry but no, the reseller/distrib should fully test the tubes - by fully I mean real world tests, not a couple of useless measurements with an el cheapo tester.

End users aren't supposed to get defective stuff, or buy 20 tubes in order to get a matched quad.

Hello! I'm not saying this is how it should be, it's just how it is. If you can find a tube reseller that fully tests the tubes they sell, please let us all know who that is.

[FYL]

If you can find a tube reseller that fully tests the tubes they sell, please let us all know who that is.

I buy in bulk, do the real tests and neither work with resellers nor resell "bare" tubes, so I'm not really qualified here.

[dartanion]

If you can find a tube reseller that fully tests the tubes they sell, please let us all know who that is.

I buy in bulk, do the real tests and neither work with resellers nor resell "bare" tubes, so I'm not really qualified here.

Well, that's the main issue. Regardless if you are buying bulk from the manufacturer or buying from a reseller, you still have to "test" them all yourself. It sucks, but that's reality. If true QC was applied at the factory, we'd have much less failures and crap tubes reaching the consumer. Even the resellers/middlemen are not or cannot fully test the tubes they sell. It eats into their profit margin.

[FYL]

Even the resellers/middlemen are not or cannot fully test the tubes they sell. It eats into their profit margin.

All quality distributors I work with fully test and grade the tubes they supply - either rebranded or stock versions. That's how they can justify their margins: for instance a pair of 6П14П-EB resold as TAD EL84-STR streets for $31.95 or so while the same pair in Sovtek EL84M guise streets for $24.95.

The Sovtek's are tested and somewhat matched, the TAD's are graded for noise, fully tested and matched, with current as well as transconductance measured and the tubes labelled with the actual results.

BTW, the original 6П14П-EB can be bought in bulk for less than $5.00 a pop, new in crates but neither fully tested nor matched.

[dartanion]

Does the TAD procedure include a burn in period and tested at realistic voltages that you see in an amp? I doubt it, but they may.

[FYL]

TAD tubes are burnt-in and tested at realistic voltages (up to 500v plate for their custom gear if I remember correctly). They don't fully test big bottles and offer them with "factory matching" only - heck, matching 845's at 1KV plate requires a muy expensivo dedicated system.

[dartanion]

TAD tubes are burnt-in and tested at realistic voltages (up to 500v plate for their custom gear if I remember correctly). They don't fully test big bottles and offer them with "factory matching" only - heck, matching 845's at 1KV plate requires a muy expensivo dedicated system.

Thanks for the info. They are doing it right then. I'll have to give some TAD tubes a shot in the future.

[FYL]

I'll have to give some TAD tubes a shot in the future.

Their EL84-STR is excellent (as is any properly selected 6П14П-EB). works very nicely in Voxen as well as derived amps, not so nicely in 18-watt clones which need "dirtier" tubes.

I also like their 6V6GT-STR in BF's - works really well in an Express too; ditto for the 6L6GC-STR and 6L6WGC-STR in Fender-style amps.

Their other power as well as preamp tubes are less interesting IMO.

Oh, here's an interesting article in Guitarist (a Brit rag) about testing at Watford Valves, a serious UK distrib:
http://www.watfordvalves.com/pdfs/guita ... review.pdf

They've even co-designed with David Petersen a dedicated EL84 tester for Brian May and other players who dare to use Voxen on stage...

[passfan]

I'm in agreement with Jana, I think the tube has a poor vacuum. If it's just a poor vacuum rather than leaking, then eventually you might see that plasma use up the residual nitrogen in there and the tube will work out O.K.... but I'm skeptical of that. A little bit of gas can make plasma for a very long time.

I have photos of the vintage Saratov's (thank you Lonely Raven). Fishy is right, these are from the old school and are obviously different in appearance. These tubes sound awesome and I think I bought a matched set of four for $44 US... hard to beat that price for a tube this great.

Follow this link and look for ones like in these pictures and hopefully he's got some left. "The Tube Sargent"... http://mhuss.com/sgtoverdrive/

these are the ones you want...

rj

Just picked up 8 of these from 79' off ebay for 32 bucks. We'll see how they sound unmatched.

[Rick]

It's up to the consumer to apply QC to new tubes. If they are bad, send them back to the Tube Depot and get your money back. Again, tube testers are of limited utility. They don't put your tubes into a realistic operating condition, so they don't tell you squat. The only way to get a good set of new tubes is to buy more than you need and weed through them. Then send the rejects back for a refund.

Yes, I understand that. I've been weeding through tubes for years and sending back defective tubes as I have already sent back these EL84Ms. Fortunately Tube Depot is good in that regard as they have a pretty no B.S. return policy and refund is not a problem. I just think that the whole production-distribution chain is failing at least at a few places. Defective tubes shouldn't be leaving the factory outside of a trash dumpster. Retailers should do the real world testing you speak of and save us a lot of trouble. Some claim to do testing but I'm not sure what kind of tests they are doing or how comprehensive they are.

BTW, I'm wondering, I have an early Jackson 648. I realize it is not a true mutual conductance tester. The meter says "RELATIVE MICROMHOS". Tubes like EL84s give a variety of readings, much more varied than the same tubes on a simple emissions tester, so I have used it to try to match somewhat a pair or quad of tubes. I'm wondering if these readings are at all useful to try to at least marginally match some tubes, or are those readings as useless as plain old emission readings as far as matching is concerned?

[FYL]

The Jackson 648 is a dynamic emission tester, quite flexible and fast but far from sufficient for any half decent testing.