What happens to the sound of a 12AU7 tube when...

Elizabeth · « **Reply #20 on:** 8 Mar 2013, 11:50 pm »

My VAC Standard preamp had used tubes in it when i bought it. It has been on, 24/7 for the last three years... 3X365x24= 26,280 hours in use. And the tubes are stull playing great. (two 12AU7 and two 12AX7) well i might have turned it off several times try another powercord,so scratch two hours off that total.
So I question "5,000 hours" for a preamp tube?
A few preamp designs have the problem of 'eating' tubes, but plenty of others have designs allowing tubes to last for a very long time.

SteveFord · « **Reply #21 on:** 9 Mar 2013, 12:36 am »

I always figured 2x power tube lifespan for preamp tubes for a rule of thumb.
5000 power tube, 10,000 preamp but anything can happen.

AB · « **Reply #22 on:** 9 Mar 2013, 12:39 am »

Swap in some newer tubes and see how you feel.
Have you heard of the boiling frog metaphor?
I think it might apply here.

FullRangeMan · « **Reply #23 on:** 9 Mar 2013, 02:28 am »

Quote from: Elizabeth on 8 Mar 2013, 11:50 pm

My VAC Standard preamp had used tubes in it when i bought it. It has been on, 24/7 for the last three years... 3X365x24= 26,280 hours in use. And the tubes are stull playing great. (two 12AU7 and two 12AX7) well i might have turned it off several times try another powercord,so scratch two hours off that total.
So I question "5,000 hours" for a preamp tube?
A few preamp designs have the problem of 'eating' tubes, but plenty of others have designs allowing tubes to last for a very long time.

The most Methuselah small tube I have seen in recent years avaliable are the 6N1P-EV, this version are said to 10K hours.
ЕВ (EV)= higher reliability, longer life and mechanical ruggedness, according russian military tube spec books, the regular version are said to 5K hours.
Chinese or USA NOS tubes may differ.

I was told the factor that most affect tube life is the cold/hot cycles, most regular tubes are specified to 2K cycles.
So this tubes in your preamp seems benefit from small numbers of cold/hot cycles.
They had a long life in standby(that help the getter keep the vacuum clean), but few hours working with music, this led to a long life in hours numbers.

Elizabeth · « **Reply #24 on:** 9 Mar 2013, 04:43 am »

Quote from: AB on 9 Mar 2013, 12:39 am

Swap in some newer tubes and see how you feel.
Have you heard of the boiling frog metaphor?
I think it might apply here.

The system plays fine,and sounds great. I do not need to 'fix' what is not broken.
I am guessing you need to justify what you think you know?
Plenty of folks mention tubes which have lasted a very long time.

Freo-1 · « **Reply #25 on:** 9 Mar 2013, 01:07 pm »

Quote from: Elizabeth on 9 Mar 2013, 04:43 am

The system plays fine,and sounds great. I do not need to 'fix' what is not broken.
I am guessing you need to justify what you think you know?
Plenty of folks mention tubes which have lasted a very long time.

I'm sure it does sound fine. Telefunken 12AX7's are well noted for lasting a very LONG time. What I think piques the curiosity is how they (your tubes) would measure on a calibrated mutual transconductance tester (say, a Hickock 6000) after such use. The tester is what I use to figure out when a tube is going kaput. I'm not willing to let a power tube take out components. Once it measures low, it's out.

One item of note: I bought a pair of Bendix 2C51's that measured low (but still in band), but sound great. I think that happens a lot with tubes.

Ericus Rex · « **Reply #26 on:** 9 Mar 2013, 06:28 pm »

I can't say that I've ever worn out a 9-pin. They've always gone microphonic or totally kapput long before wearing out. Or I've sold the component before that. 5,000 hours seems like a rather short life for inputs/drivers. Maybe Rogue does run that tube a bit hot in the Perseus. It's a good thing you love the sound of the JJs. Retubing every 3 years with Teles would be painful!

Enjoy!

TJHUB · « **Reply #27 on:** 23 Mar 2013, 09:56 pm »

After a couple of weeks with my new tubes (4 of them), two things are very apparent. One, my old tubes now identified as Sylvania 12AU7A CONN organ green labels were definitely on their way out. Two, JJ ECC802S tubes sound like crap in my Rogue Audio Perseus preamp. What a waste of money. I now have a couple matched pairs of RCA clear tops to try before going back to NOS Sylvania's. It's hard to believe how much the wrong tubes can damage the sound quality. I find myself not even interested in listening any more...

Freo-1 · « **Reply #28 on:** 23 Mar 2013, 10:09 pm »

Does not suprise me in the least. Never been a big fan of 12AU7's. Whenever possible, a 12BH7 is preferred. The BEST 12AU7 type is the 6085 (what a sweet tube!) It is not exactly a drop in for the 12AU7. Need to check with the manufacture or your gear first.

TJHUB · « **Reply #29 on:** 23 Mar 2013, 10:16 pm »

I've had a couple discussions with people that really know their stuff. I HATE tube rolling. I've never had any success with it other than spending money. And I've talked to many people about the JJ tubes, and Rogue is the ONLY place or person that said they are a good tube. Absolutely everyone else says the JJ's aren't any good. It looks like everyone else is right!

I'm now working with Brent Jessee. He has never steered me wrong in the past, and I hope he doesn't now. His trade-in policy helps too. I regret not calling him in the first place.

Ericus Rex · « **Reply #30 on:** 24 Mar 2013, 12:24 am »

Too bad you're not happy with the JJs. I had hoped they'd work out for you as they are quite inexpensive. At least Sylvanias aren't uber-priced like some NOS Europeans. They sound pretty good and are cheap...well, maybe not Brent Jesse's Sylvanias.

Did any of the people you consulted recommend ANY new production tube?

TJHUB · « **Reply #31 on:** 24 Mar 2013, 12:42 am »

No one suggested any new production tubes. Would you?

kingdeezie · « **Reply #32 on:** 24 Mar 2013, 12:48 am »

I like the PSVANE tubes. They are current production tubes. They are pricey, but they are readily available.

ted_b · « **Reply #33 on:** 24 Mar 2013, 12:51 am »

I still say 5814 Sylvania Gold brand Gold label triple micas. $75/pair. Wonderful sounding.

TJHUB · « **Reply #34 on:** 24 Mar 2013, 12:51 am »

Quote from: kingdeezie on 24 Mar 2013, 12:48 am

I like the PSVANE tubes. They are current production tubes. They are pricey, but they are readily available.

I didn't want to mention the Psvane tubes, but I rolled about 10 different tubes through my DAC, and the Psvane was my favorite.

Ericus Rex · « **Reply #35 on:** 24 Mar 2013, 01:33 am »

Quote from: TJHUB on 24 Mar 2013, 12:42 am

No one suggested any new production tubes. Would you?

I'm just wondering how the JJ compares to other new production. If your tube gurus are pricey NOS fans then no one is going to recommend new production. It doesn't mean the JJ is total garbage, if I read your post as intended. Are the JJs fully broken in?

I don't have a lot of experience with the 12AU7 so I wouldn't venture a guess and possibly waste any more of your dough. At this point, I'd just recommend going with what you know you like: Sylvanias.

TJHUB · « **Reply #36 on:** 24 Mar 2013, 01:41 am »

Just know that my "tube gurus" as you call them have only suggested tubes that are cheaper or similarly priced to the JJ's.

The JJ's have at least 200 hours on them. Let's just say they are definitely not for me.

Kim S. · « **Reply #37 on:** 24 Mar 2013, 09:30 am »

I've tried the JJ's in my preamp (not a Rogue) and I agree they are not very good. You cannot go wrong working with Brent Jesse. They are pricey but you might want to try NOS Mazda 12AU7's. As Brent describes, they are a very clean and dynamic tube, for me well worth the price. He can probably direct you to a lot more inexpensive choices that would also be good.

borism · « **Reply #38 on:** 24 Mar 2013, 01:03 pm »

Quote from: TJHUB on 23 Mar 2013, 09:56 pm

I now have a couple matched pairs of RCA clear tops to try before going back to NOS Sylvania's.

Terry,
How are the RCA clear tops sounding in your preamp? I bought RCAs from Brent Jessee for my Atma-Sphere MP3 and preferred them over NOS Mullards and Radiotechnique that I got from Upscale.
I find tube rolling to be quite enjoyable though.
Boris

TJHUB · « **Reply #39 on:** 24 Mar 2013, 02:25 pm »

Quote from: borism on 24 Mar 2013, 01:03 pm

Terry,
How are the RCA clear tops sounding in your preamp? I bought RCAs from Brent Jessee for my Atma-Sphere MP3 and preferred them over NOS Mullards and Radiotechnique that I got from Upscale.
I find tube rolling to be quite enjoyable though.
Boris

I was hoping o get the RCAs on Saturday, but they didn't show up. I should get them tomorrow. I'll be sure to report back after a few days of break-in.