Bad Tube?

[joelorigo]

In my recently built Archibald, I put in a brand new Psvane 12ax7 to see if there were any sonic differences compared to the one I had in there. After deciding that I don't think I heard much difference I turned it off and messed around with a new pedal build. When I came back to the Archibald, it was a very quiet futzy sound. Bypass was fine. I unplugged it for a few and tried it again and it was back to normal but after a few minutes I heard it go from normal to the very quiet futzy sound. Bypass was fine again. I took out the Psvane and put back in the tube I started with and played for a while, waiting to see if it happened again. It didn't. Can one assume the brand new Psvane was bad?

[jwin615]

Likely.QC on Chinese tubes isn't great. I had a rainbow  12ax7 once that had so much gain it would screach regardless of what I put it in

[joelorigo]

I put the brand new Psvane tube in my Effectrode Tube Driver and it acted fine for about an hour. So, is it possible that it doesn't like my Archibald? Or  is there something with the fact that the Effectrode has 3 tubes?

[gordo]

Tubes can be hit or miss.  I've been out of the repair business for a while now but a pal of mine owns a music store and after a silver face Pro Reverb got rebuilt by his repair guy (an absolute wizard) it came back in with weird noises.  Like, literally the next day.  It would blat out and have some fizzle on the note decay.  His repair guy is out for a while so he asked me to take a look at it.  The first tube on the Vibrato channel was wonky.  Not a brand new tube but worked fine when it left the shop.  Replaced it and all is good.

In comparison the other amp I took in is a 65 Epiphone Comet with ORIGINAL TUBES!!!  The tubes sound just glorious.  The caps are all shot but the tubes are fantastic.  This one gets a 3 prong conversion and a recap.  I really don't have the time for this stuff any more but I forgot how fun/frustrating repairs are.  This old beast gets a beautiful set of F&T and Sprague caps and will go back out the door ready for another 50 years.

[jimilee]

Daaaammn, I bet that's what was wrong with my first tube amp about 7 years ago. I paid to have it fixed. I could've just replaced the tubes myself.


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[joelorigo]

I took the new Psvane tube and tried it in my AC15 and it works fine there as well. Weird that it didn't like the Archibald. The Archibald has not had any problems since I took out the Psvane. I have tired 2 12AX7s in it and it's fine.

[jwin615]

It may be a gain factor issue. It should have a GF of around 100. If its 120 or even more, may be clipping other components or pulling to much current?
I had a Ruby once that went bonkers in some circuits. Super loud. They were made by the same cats that later started psvane iirc.
Also, Holy ____! Those go for $20+?!?!?!?
why not just get a JJ or EHX?

[joelorigo]

If I remember correctly, when I bought the psvane a few months ago, they were 17 and change. Cheaper than JJ and EHX but not by much.

However, one of the 2 tubes I mentioned trying in the Archibald since taking out the psvane is a "yugo" 12ax7. 50 with shipping which is the best price I could find. I don't think I hear a difference worth double the price.