What should I do with this tube?

chadh · « **on:** 17 Apr 2006, 03:48 am »

Let this be a lesson to everybody: only shop on eBay when you're sufficiently awake to read product descriptions properly.

I've ordered my very first tubed component - a pre-amp from Space Tech Lab which will use a pair of 6sn7 tubes. As I wait for it to arive, I decided to go shopping for tubes on eBay. Well, it was late at night, and I obviously wasn't reading things clearly...or maybe I wasn't thinking clearly...or maybe it was both. Anyway, it seems I put in a bid on a single NOS tube (RCA 6sn7, black plate, black base, silver label), and will almost certainly win the auction.

So the question is: what should I do with this tube?

I need a matched pair for use in the pre-amp, so a single tube isn't much use to me. But this particular species of tube is purportedly a good one. Is it silly to hang onto it imagining that I can find another tube to match with it? Is such a plan even sillier if I have no way to test a tube? Should I just try to sell it?

Chad

acresm22 · « **Reply #1 on:** 17 Apr 2006, 04:38 am »

Don't worry about it...if you win the auction, great. Just look for another RCA 6SN7 to pair with it. Or try another brand 6SN7 and see how it matches up.

Here's a story...couple years ago I had an SE amp from a respected SET boutique designer...this one used 6L6s wired in triode. I had a nice Sylvania 6L6G coke-bottle shaped tube in my stash, but only one...so I shopped around on ebay and bought another. Was it matched to my existing 6L6G? No. Did it look exactly like my existing 6L6G? No. Did the two of them sound terrible together in the amp? No! In fact, the amp sounded wonderful using this pair.

Don't sweat it. Back in the old days, people were swapping tubes out of their good ol Magnavox consoles all the time, and loving every minute of sweet music that poured out.

D.

ohenry · « **Reply #2 on:** 17 Apr 2006, 02:15 pm »

If it were me, I'd candidly tell the seller what happened and ask if he could offer another to make a reasonable pair (assuming you win). Many of the ebay sellers have many tubes to offer and could accomodate that request. If not, buy another as recommended before, scribble a few numbers on two self-adhesive small white labels and attach them to the tube bases. Voila, matched tubes!

JoshK · « **Reply #3 on:** 17 Apr 2006, 02:27 pm »

This is actually a tactic to finding good tubes at good prices. Case in point, vintage 45's for instance tend to sell for much more than twice the individual price when they are paired. Solution? Buy a bunch of singles and pair them up yourself. Saves money.

chadh · « **Reply #4 on:** 17 Apr 2006, 05:49 pm »

Thanks for the advice.

I'll keep telling myself that I'll be able to save money this way. Except, if I keep perusing ebay at 1:30am, I'll probably end up making lots more mistakes. On this sale, for example (which I did win!), I got the tube for $8. But I'm also up for a $7.50 handling fee, along with shipping. And insurance (if I were to buy it) would be another $4. I can't believe these are market prices. The only thing more outrageous is the fact that I seemingly overlooked these issues when making the bid.

Of course, it's not a diaster. It's still only costing me $20 (without insurance). And hopefully I'll be more shrewd next time.

One question though - how closely should I aim to "match" tubes? Ideally within 5% or so on conductivity ratings?

Chad

Chad

boead · « **Reply #5 on:** 17 Apr 2006, 07:36 pm »

Yeah, matched tubes only mean they are tested to within tight tolerance of each other.

I’ve bought boat loads of tubes from eBay and so has a friend. Once he acquired a tube tester we found out how easily people are being ripped off. SO MANY tubes I have bought that the owner claims are NOS or 80+% good (and have been tested) are not!! So many end up being below 50%, so much so that my friend had his tester tested and recalibrated only to find out that nothing was wrong with it. Buyer beware!

What’s funny is that the sellers are fast to exchange or even refund your money when you tell them that the tube you bought that was supposed to be NOS was hardly over the minimum good mark – tell me they don’t know!?

All the tubes I like are usually between $50 and $150 each. The ones that actually sound great are desirable and tend to yield more money at auction. That doesn’t mean that a cheap tube can’t be your favorite but the general laws of supply and demand ring true.

markC · « **Reply #6 on:** 17 Apr 2006, 09:45 pm »

I've had the same experience on Ebay-you (generally), get what you pay for. If it seems like a deal that's too good to be true, it probably is. One of the best deals I got however was on a tube tester. But exotic tubes such as Sylvania 5751 3 mica black plate '50's vintage for cheap are not likely very good.