Thanks Myles for all your good Karma and always "paying it forward" to assist others.
When it comes to my interests and hobbies, I can get into it and go on and on! I am fascinated with the subjectivity of tone and the expression of tone through the use of valve amplification technologies. With your knowledge, experiences and contributions that you have made in the quest for tone,,,,, Just saying, that I am sure that I have enough questions and interest in your opinions that you could probably write a book. So if I start getting carried away or what not,,,, I hope someone will let me know "hey dude your hogging the forum" or "just quit now, with bothering the man!"
Ok with that above disclaimer above said and without having reached my limit on Questions for Myles, Here's more general material for Myles to ponder and maybe could be helpful for others beside myself.....
VINTAGE TUBES? USED TUBES? OLD TUBES? BACKUP TUBES? ECT.......
What ways can a person judge and decide if an older tube is still serviceable or worthy? I have been more and more often coming up on old classic used tubes and such. Some old tube brands are in such high demand that prices for even used tubes have become ridiculous! As an amatuer enthusiast and not fully professional service man (person) .... I have fairly rudimentary compliment of test gear, (Test gear is another whole subject!) I don't have a "tube tester". Thinking out loud,, how many modern service guys actually have access to tube testing equipment? Everyone just relies on the tube vendors?
What can a person do to test or judge tubes without a tube tester? I have been a bit apprehensive of purchasing tube testing gear for several reasons. First, I dont have enough knowledge about which tester, tests what? Or what needs to specifically tested. Not all testers are the same or useful in what attributes they test. Second, nobody makes a modern tester that can bought brand new. Vintage old equipment that is reliable might be a premium, and reqiure alot of maintence and calibration, plus most are big boat anchors that require shop space too. So short of a tube tester what can someone do to judge or grade the usefulness of tubes? One bigtime scenario that I have come upon is all these unmatched unknown tubes I have accumulated. I suppose its a symptom of my hoarding but I always save my old tubes when I put new ones in. I have one amp that would vibrate and puncture the envelope on just one tube and I ended up with alot of mismatched sets of triplicates before realizing what caused vacuum failure. Expensive when you have to buy a whole set of matched 6550's, relying on the vendor to grade them! (Ok I shoulda bought groovetubes or ruby's that grade and indicate the matched sets! But I am a comparison shopper looking for best deal and at that time unsavvy on how to spec and request a single to match my other triples!) Still am unsure how or what to request when I dont know the exact tranconductance and how current was matched with the other three. We put alot of faith in how the heck these vendors actually match a set sold to us. Dynamically in the amp may or may not be indicative, but if it is working I suppose all else matters not... Maybe that crosshatch mismatch is a good thing sonically and the old crude perception of ones own ears knows best?
Similiarly I have a rare old amp that runs exotic expensive quad of 8417's I have numerous single examples and no way to match em other than just measure individual cathode current in amp operation? (Lightbulb moment) . Accumulating tubes and trying to match them, what other way to test other than measure current draw in a test amp?
Visual physical inspection? Anything to look specifically for? Am I missing anything when I look at the following things????
I look at the plates, looking for deformation, warpage, signs of overheating. I look at the mica standoff and spacer, making sure the components are secure, I also hold the tube and tap the envelope with my forefinger, feeling if the interior vibrates or rattles and possibly microphonic. I view the silver deposit on the glass around the getters, looking to see how solid the deposit and how opaque and no haziness cloudy or dull flaking for indications of vacuum failure, I also look at the glass for any other evidence of foriegn or dark dirty burnt deposits such as vaporization of the interior components deposited upon the glass. I check that the leads arent broken or arc'd below the plates and where they exit the envelope.
Is this sound methodology? Or does it really prove norhing? I hate to place a tube in an amp only to have it be internally shorted and take out my newly built or overhauled amplifier. Its happened before, luckily with just a screen resistor. But would hate to fry a circuit board on say my 74 marshall!
My collection of old and desirable vintage tubes is growing steadily. Its interesting and fun to roll some of them through my own amps on the bench as I gain a better appreciation for the subtle nuances and tone traits of various similar tubes. But how can I be assured of reliabilty of the tubes life once I button up the amp and want to put it to use? ESPECIALLY WORRYSOME IS RELIABILTY OF POWER TUBE DISCOVERIES!
Even more so is the fact that as I have refined my ear and experience at judging tone, more and more acquaintences look to me for tone and setting up their amps! A big starting point and cornerstone to my toneprinting begins with Vintage and/or NOS premium tubes. Many times my tube precurement must resort to antique salvage used finds of these devices. When used for non-personal gear, and professionally performing gear reliabilty now becomes a liability issue, not just an inconvienence. And...... what to do about all those unmatched singles I have collected? How many single ended amp builds can you have? I got a single ended of every popular audio tube,,, either breadboarded or housed in lunchboxes, tupperware, even inside an old dreadnought... !
Maybe I could build a benchtop test amp thingamajiggy. Could run some dynamic testing? What features would you include on such a project? What would you measure and how could it be incorporated into the test amp?
Finally what traits make certain tubes stand out as being exceptional tubes? I have limited experience with a few of those holy grail NOS tubes and some of them were nothing spectacular. A set of Mullards stands out as being very uninspiring. I have others such as a pair of mediocre sylvania bq6c that were relabeled as magnavox that were exceptional sounding. I put those ones aside for safe keeping! Interestingly they had failed my visual screening numerous times because of all the dark burnt looking deposits inside the glass. NOW TELEFUNKEN 12AX7 ECC803 SMOOTHPLATES.... those that I have are the gold standard. I didnt even know how premium they were back when I first had placed them in a Crate Blue Vodoo amplifier and appreciated that they worked best. No wonder why, they are all the hype, at least the few working examples I have. However, I just noticed the bids that some have been getting on Ebay,,,, if thats any indicator of the market, I am very scared! Great tube but not at over $150+ dollars with or without orig box!
Also as I proofread I had another question about why I am hoarding numerous tubes with no vacuum? Could they somehow have a new envelope blown and if soneone could draw down a powerful enough vacuum? I know not many places to find that strong a vacuum but, I have crossed that bridge before in the other direction and now have access to 4800-6000psi compressed air! So might not be practical but is it feasible given the tenacity,, could new life come to lets say some ultra premium uber expensive tube examples in which the envelope had failed and breached in air? I just cant seem to throw some things away!
So if I havent worn out my welcome what has Myles or anyone else have to say on the subject of tubes, old tubes, used tubes, NOS tubes or just usefulness of tubes in general?????????