Stock German EL34s in '93 Rivera R55-12 - Still Good to Go?

[tbonesullivan]

I picked up an R55-12 last weekend from BCR music, and honestly, it does sound pretty damn good as is. However,  given that it's 1993 and in VERY good shape,  that often means that the original tubes may still be inside it. I've gotten more than a few used amplifiers that still had the stock tubes.

My dilemma is that the stock tubes turned out to be Rivera tested German-made Siemens / RFT EL34s.  OLD Production tubes. I'm not very familiar with how original production tubes age. They still have plenty of getter flash on the top of the tubes, and i don't really see or hear any issues. However, I don't have a tube tester, so I can't really see how they stack up.

The preamp tubes also, are a Sovtek 12AX7WA in V1, with the rest being Chinese Beijing old production with the square foil-dimpled Getter. I know they aren't the same level as something like a Phillips or RCA, but people are willing to pay around 25-30 for new ones.

[LucSulla]

I listen to Dave Friedman's podcast, and he's pretty adamant, particularly with EL34s, that if you have some that sound good, don't touch them.  Given his ongoing issues with dependable EL34 sourcing (the dude hates a JJ), I think he'd got a point.  If I get a good sounding pair these days, I run them until they die, and if you are describing the amp as still sounding good, they aren't dying.  I play in bars and roadhouses; no one is going to here my top-end attenuating or whatever else supposedly happens to tubes as they age.  If the bass isn't flubbing out, I'm not hearing dropouts, and obviously nothing is red-plating,  the tubes stay. 

[tomteriffic]

^^^This.  Also goes for 6CA7's.  In my 55-12 I had a bit of noise, as in a bit more than I thought should be there.   I did a little preamp tube swapping with some decent new production, slightly used and NOS and did get the noise down a smidge, but I'm not sure that it was worth the time (I already had the tubes).  At the idle level that the noise became objectionable the amp in actual use was painfully loud.  Gawd I miss that amp.

[LucSulla]

2 hours ago, 0054 said:

http://www.tubetone.ru/index.php?option=com_content&view=article&id=106:friedman-eng&catid=39:2010-02-18-21-08-20&Itemid=139

He likes em here... who knows, right?

 

He did like them, but that interview is from a few years back,  in the past two years, he's gone from JJs to TAD to I believe Electro Harmonix.  I can't remember if I have those or TADs in my Small Box.  Around 2016, he started having a high number of bench failures on batches of JJs.  He gets pretty deep into it on one of the Tone Talk episodes. 

[tbonesullivan]

Ok then. I'll check the bias reading on the power tube, and keep them in.  Preamp tubes though, yeah those gotta have some changes made. The reverb driver is fine, but I'll probably swap out at least the first two tubes, and maybe the phase inverter. I do have some old production preamp tubes,  but most are long plates, so V1 really isn't a good place for them.

[tbonesullivan]

Well,  in my basement, we get 122 VAC, which is a bit above the 115VAC these would normally be biased at, so it's up around 80% plate dissipation.  I was getting around 47mA on each tube, so they are a bit high. Rivera recommends 40-45mA though, which is still pretty high compared to some recommendations.  at the 435 V I was reading on the plates, 40mA is 70%, and 45 is 78% of the max dissipation for an EL34.  Most likely, the amp is still set up as it left the factory, so the bias may have drifted somewhat.

[texwest]

I third, leave them in if you like the sound and they aren't starting to redplate.  It's all about the tone right!

Of course Friedman has to choose some sort of new tubes for his newly made amps!  So no contradiction there really.

I recently put new Svetlana's in a guys 74 Marshall and they sounded killer.  I bought the burned in for 40 hours ones thinking they might be more reliable that way.  I've had so many problems with new tubes, that I would hope if they run for 40 hours the bad ones will fail before I buy them.

The new Tung sol 12ax7's sound about as good as alot of NOS tubes. Less than $20 each.  Not as reliable if you put them in a socket that is a cathode follower circuit.  V2 of an old Marshall.

[tbonesullivan]

The Tung- Sols are nice. So are the reissue Mullards, which come from the same factory. The R55 doesn't have any cathode follower positions that I am aware of. Virtually every Marshall amplifier has one.

Right now I'm trying to decide whether I want to put a Sylvania or a CBS Hytron in the V2 slot for some vintage tube goodness.  The Baldwin-labeled Sylvania tubes are supposed to have a really nice overdrive sound.

[texwest]

Yes those Sylvanias are very nice.  Many years ago I bought a whole bunch of Tungsram and Sylvania 12ax7's for my personal use. Enough for the rest of my life.  They were the ones that sounded great that didn't already cost an arm and a leg, like the Mullards and Bugle boys.  I actually like the Tungsram and Sylvanias better anyway!

[tbonesullivan]

I've got a few Sylvanias now, but only one tungsram. Also two RCA short plates, and a bunch of others.

I'm probably going to put one of the RCA short plates into my Carvin Vintage 16. It's only got one slot aside from the phase inverter. I had thought about putting a CBS /Hytron there as well, but I think a short plate would work better as V1. Also going to put an RCA into my Maverick.

I may have to hunt down some more tungsrams, but they are hard to find. Groove Tubes bought up a lot back in the day.