PSA regarding tubes

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PSA regarding tubes

Post by Jaded Faith » Wed Mar 19, 2014 7:42 am

I have noticed several modules sent in recently for mods or repairs that had tube-related issues. I wanted to post this info in a sticky after emailing it several times this week.

I noticed several Tung Sol's being used in V2 (the tube on the right). That is the cathode follower (CF) position. Anything manufactured by New Sensor (ie: Tungsol and Mullard reissue, EH, Sovtek etc) have a lower heater to cathode rating. They will either completely die, go half gain/volume or fluctuate in volume if used here. JJs, Chinese and NOS preamp tubes will be fine for the CF position.

This is a tube manufacturing issue and has nothing to do with the modules or amp involved. It is not an MTS-related issue, it has to do with using the New Sensor tubes in any CF circuit. A CF stage subjects the cathode to high voltages and these tubes can not handle it. It may not cause an instant issue, but is will fail prematurely. Most of the donors sent in lately with a Tung Sol on the right have tested failed or worn with the CF side of the tube as the bad side.

This is a well-documented issue for several years now.
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Post by MarcoR » Wed Mar 19, 2014 12:05 pm

Thanks Rob! This is critical information to know!

This explains why the Mullard reissues I tried craped out one after the other when I tried them once and swapped their positions and tried again; first half volume then no volume.
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Post by drewiv » Wed Mar 19, 2014 4:47 pm

This is good information to share, thanks. One question, where do Ruby Tubes fit in this description? Chinese, I assume.
I've been known to have a module or two.

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Post by drewiv » Wed Mar 19, 2014 6:34 pm

Also, I believe you use an Orange tester, as do I. At what point (#) do you consider a tube weak and replaceable?
I've been known to have a module or two.

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Post by Jaded Faith » Thu Mar 20, 2014 6:25 am

Ruby's are Chinese. The main New Sensor brands you need to be aware of for this issue are Electro-Harmonix,Tungsol, Svetlana, Sovtek, Mullard and Genelex. I go through hundreds of tubes a year here and the Mullards and the Tungsols are the most sensitive to this. Mullards typically die instantly in this scenario.

The Orange VT1000 is what I use for simple day-to-day testing where my better testers aren't needed. That grades on a scale of 0-15. Any reading of 0-3 will fail the tube and it's garbage. I won't return these tubes to you and try to call or email immediately. A reading of 4-5 is considered worn and this tube has a very short life left with deteriorated performance. It should be replaced ASAP. I consider a 6-9 typical gain and healthy. Anything at a 10 or above is what I consider high gain.
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Post by drewiv » Mon Mar 24, 2014 5:23 am

I had several Sovteks (and a couple EH) in the V2 position when I went through my modules yesterday. All but one of these tubes tested good, if not incredibly high, on my tube tester. All these modules (tubes) have several, upon several, hours on them. I did swap them out and moved some Sovteks to V1 in some modules (put the rest in inventory), replaced V2 w/ Ruby HG/HG+, JJ or Chinese. Is there an explanation of why the Sovteks would have lasted so long in V2?

Also, where do Svetlanas fit in the mix? Are these New Sensor tubes?
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Post by Mattfig » Mon Mar 24, 2014 6:37 am

I'm also interested in this info....I tend to prefer Tung Sols in module V2 and mine also test well over time on my tester (Orange Valve Tester) ?

Is there somewhere to read up on this info?

Thanks.
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Post by hmic10 » Mon Mar 24, 2014 6:52 am

Just to make sure, If I am looking directly at the face plate v2 is on the right, correct?

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Post by Jaded Faith » Mon Mar 24, 2014 7:04 am

Hmic10: V2 on the module is on the right when looking at it from the front.

Drew: Sovtek are among the most stout of the New Sensor offerings. There are no hard and fast rules except that the potential for failure exists from this manufacturer. I will confirm from personal experience and several customer reports that the Mullard tubes are the ones that die the quickest. Many reports of these dying instantly in a CF position. I would say Svetlana and Tung Sol are the second quickest to die consistently.

Matt: There's no general place I can refer you to, but a quick Google search will show hundreds (if not thousands) of sources for this info all over the Internet over the past decade. It's well-documented for many gurus in the industry. You can find tons of posts from everyone from Friedman to Fortin amongst others all over Internet forums. Several Tube sellers will also mention it. It was a topic of discussion at the LA Amp show last year on our high gain wizards panel. I would say is being common knowledge since at least 2007.
Last edited by Jaded Faith on Mon Mar 24, 2014 5:38 pm, edited 1 time in total.
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Post by rblyn » Mon Mar 24, 2014 8:12 am

This makes sense since I lost several Tung Sols (gold pinners too) and EH in that V2. It would appear some old NOS, the Chinese tubes and JJ's arent affected here...At least in my rig.
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Post by drewiv » Mon Mar 24, 2014 8:21 am

Jaded Faith wrote:Hmic10: V2 on the module is on the right when looking at it from the front.

Drew: Sovtek are among the most stout of the New Sensor offerings. There are hard and fast rules except that the potential for failure exists from this manufacturer. I will confirm from personal experience and several customer reports that the Mullard tubes are the ones that die the quickest. Many reports of these dying instantly in a CF position. I would say Svetlana and Tung Sol are the second quickest to die consistently.

Matt: There's no general place I can refer you to, but a quick Google search will show hundreds (if not thousands) of sources for this info all over the Internet over the past decade. It's well-documented for many gurus in the industry. You can find tons of posts from everyone from Friedman to Fortin amongst others all over Internet forums. Several Tube sellers will also mention it. It was a topic of discussion at the LA Amp show last year on our high gain wizards panel. I would say is being common knowledge since at least 2007.
Thanks, Rob. I have found several websites, reviews, etc. that all are very clear in NOT USING these tubes in CF positions. I guess I should consider myself lucky that I didn't lose more nice tubes.

A bunch of Ruby and JJ on order as I used most of my supply on the project yesterday.
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Post by nitrous12 » Mon Mar 24, 2014 8:27 am

Looks like I am going to need to order up some JJ, Ruby, etc.
where did you order from drew?
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Post by dcg8 » Mon Mar 24, 2014 8:30 am

I just ordered $200 worth of Ruby's and JJ's from Doug's Tubes.
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Post by drewiv » Mon Mar 24, 2014 8:34 am

nitrous12 wrote:Looks like I am going to need to order up some JJ, Ruby, etc.
where did you order from drew?
I went with ValveQueen.com for the Rubys and Ruby/JJs. She has quite a nice variety at various pricing levels.

I got the Shuguang and straight JJs from tubestore.com.

I usually order from Doug's, but he sent me a couple bum tubes last time according to my tester and all he had to say was "they're guaranteed to work for their intended application." So, that's it for good ol' Dougie.
Last edited by drewiv on Mon Mar 24, 2014 10:52 am, edited 1 time in total.
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Post by Jaded Faith » Mon Mar 24, 2014 9:20 am

I have a very good record on any orders through The Tube Store and Tube Depot as far as consumer outlets go. Valve Queen is great as well.

If you are buying JJ's specifically, email Bob at Eurotubes and tell him Rob at Jaded Faith Mods sent you over. I use him for critical orders. His stuff is consistently the best tested before it ships out and my own checks here have confirmed it. I have the highest confidence in his JJ supply out of all my vendors.
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