Thoughts on Tung Sol reissue 12AX7 and reliability?

[Enzo]

Hummy also depends upon it being used in a circuit prone to hum. Hummy is why some amps use DC for heaters or elevate the DC.

Steve, how far off are your resistors? Are they within the stated tolerance? If you order 5% 10k resistors, chances are good none of them will be exactly 10k. There is an old trick to matching resistors. If you need a couple matched 10k resistors, and the absolute value is not so critical, but matching is - like a bridge circuit - then look off to the side. The dead on 10k ones have been culled to sell at closer tolerance, but you might find a lot of 10.24k or whatever in your batch.


You are paying them three and a half cents per resistor, but they are paying less than half a cent per each. Any duds, they aren't going to want them returned. Look them up in Mouser, even there, they are under a penny in reels, and buy several reels, and they are cheaper yet. 5000 of them in a reel.

[daz]

Can u believe this....my last one just died ! Must have jinxed it starting this thread ! It still makes sound but it's weak and making a static like sound. Popped in another tube and all is well. Best get a few ASAP because i like the tone too much to use anything else right now. Why do i always get attached to things that are either unreliable or get discontinued?

[Enzo]

Just for science, take that tube you just removed, and install it again. Does it still act defective, or does it want to work again?

[Steve A.]

Steve, how far off are your resistors? Are they within the stated tolerance? If you order 5% 10k resistors, chances are good none of them will be exactly 10k. You are paying them three and a half cents per resistor, but they are paying less than half a cent per each. Any duds, they aren't going to want them returned. Look them up in Mouser, even there, they are under a penny in reels, and buy several reels, and they are cheaper yet. 5000 of them in a reel.

Enzo- They are 5% resistors and a good portion of them appear to be off by almost 5%. I usually check all of the resistors I use and these are more off than I am used to. I usually use 1/2W MF resistors but I got the 1/4W CF resistors for when I don't want to jam in the 1/2 watters on a pcb. FWIW I have some old 1/4W and 1/2W CF resistors I got 30 years ago which are usually pretty damn close to the rated value.

I was checking out one of the suppliers- Jameco?- and I was very tempted by the resistor assortments they sell.

Steve

P.S. I have no complaints about the Velleman resistor assortment. I usually buy those cardboard packs of MF resistors that sell for $0.79 to $0.99 each mainly because they work for my resistor filing system (I put about 7 or 8 in a small 2" x 3" baggie and then store those in a 2" wide cardboard bin.)

I was pissed off at their assortment of ceramic caps because there was no voltage rating on the package or in their on-line catalog. On their forum I learned that they are 50v.

[km6xz]

If you order from first line industrial supply houses, you will get rated parts and not culls which are sold to repackaging outfits who sell to hobbyists or small repair shops. The largest by volume are:
Avnet, Arrow Electronics, Future Electronics, Bell Microproducts and Digi-Key Corp. They are cheap, fast and do not sell fall outs because they are selling primarily to manufacturers of end products. Velleman definitely does not cater to manufacturers or others who would howl if delivered out of tolerance parts.
Most of the industrial supply house also have engineering kits, sets of various values preferred in prototyping. That is the best way to get decent collection of SMD complete with easy to access containers.
Good parts do not cost more than repackaged fall outs.

[Leo_Gnardo]

If you order from first line industrial supply houses, you will get rated parts and not culls which are sold to repackaging outfits who sell to hobbyists or small repair shops. ..... Good parts do not cost more than repackaged fall outs.

Absolutely true and I've had good experience with Mouser too. A couple of years ago they had Allen-Bradley carbon comps which were often out of tolerance new or after simply aging on (my) parts shelf for a couple years. I don't see those any more and the cc's they have now are closer to value than the AB's were. Also audiophile builders/repairers/modders regard the KOA-Speer carbon films (available at Mouser) as an insider's rock bottom bargain.

Velleman - those Belgians! Even the king is about to abdicate. Love their beers - kriek is 'the bomb'. And FN products are quality. But V-man, I've never been impressed.

Stan, we had a question about Magic's tube test gear on the JJ 6L6 ... WTF thread. You helped out Magic/Ruby some years ago and maybe you could fill us in. With great appreciation, LG.

[Steve A.]

Velleman definitely does not cater to manufacturers or others who would howl if delivered out of tolerance parts.

At least in the US Velleman's market is hobbyists- and in that regard I have no complaints. Thanks for the tips about engineering kits and your list of major vendors.

Steve

[daz]

Just for science, take that tube you just removed, and install it again. Does it still act defective, or does it want to work again?

I know what U R getting at, but i've swapped tubes in that socket often enough that the tube's pins and socket aren't oxidized or whatever it is that causes connectors to stagnate and start making bad contact after a time w/o movement. But i tried it never the less and it still does it.

[daz]

Well, it's been a while but i have 3 tung sols after getting my hands on 2 more used ones. 2 hum loudly, the other is usable but hums a bit Then today i received 2 more from dougs tubes and one hums loudly, the other hums so loud it's unusable. I know y'all think it's gotta be my amp, but without exaggeration i have no less than 10 different brands of ax7's, many examples of some of them of and not one of them does this. I guess i have to give up on them. $38 more down the drain.

[JoeM]

daz,

have you tried the TS in another amp(s)?

[daz]

daz,

have you tried the TS in another amp(s)?

No, but when 10 other brands all are dead quiet then even if my amp just happens to bring it out more than some others, that still points to the tung sols as being hit and miss with mostly miss. No way no other tube i've ever tried, and multiple instances of them has ever been noisy would be the case if there was anything in my amp that wasn't right. Hell, one of the 2 new ones sounds like a freakin' trash truck driving by. It's almost too loud to talk over if you turn the amp up to even a bit less than a small stage level! If it's not the tubes how is it some are way worse than others. These things are just crap. They may be ok in a fender thats a totally clean amp. But with a preamp who's gain is about the same or a bit less than something like a peavey classic 30 and the gain at 2:00, it's WW3.

[daz]

Heres another thing i noticed about these. The hum comes and goes. The first time i plugged that really loud one in it was unusable. I plugged it in today to make sure it was the loud one and it wasn't loud this time. Still not good but no where as bad. I've noticed this with all of them. If i leave one in and play it over the course of a few days it will go back and fourth between humming loudly and quieting down a lot. They're still always very loud at stage volumes tho, as the hum gets louder in v1 with the gain pot. Might be better in v2 if it weren't for the fact they can't handle cathode voltage of a cathode follower. I wonder if that may be a hint as to why they are hummers to begin with.

[Steve A.]

daz

Is this an amp you built yourself or was it bought in a store? If we knew the model number or the schematic used perhaps we could offer more specific advice.

Steve Ahola

[Steve Conner]

I suggest you try elevating the heater circuit with a positive DC voltage if you haven't already. It can really help.

In a cathode biased amp, you can just connect the heater winding CT (or the midpoint of your two 100 ohm resistors) to the power tube cathodes, assuming they're bypassed.

[daz]

I suggest you try elevating the heater circuit with a positive DC voltage if you haven't already. It can really help.

In a cathode biased amp, you can just connect the heater winding CT (or the midpoint of your two 100 ohm resistors) to the power tube cathodes, assuming they're bypassed.

Steve, got any schematics to show how i could do that? You don''t use the circuit ground for the negative side do you?