I am done with AES -- a short rant.

[dsavitsk]

The moment of truth has arrived. A package from AES bearing the new, hand selected, supposedly physically matched, 71a's showed up at my door. And the verdict?

They are the same brand, clearly made in different years (probably different decades) and one is considerably taller than the other. That is to say, they are not even close. This is just bewildering.

[kevinkr]

I have had the same problem with 71A, and whats more 50% of the NOS/NIB ones I have purchased have been bad - and as you know they are somewhat expensive. I currently have a mismatched pair in my headphone amplifier and can neither measure nor hear any audible differences. (It sounds really good!)

I've also got ones that are same date code, same brand and mismatched in height so go figure..

The problem with the 71A is that it quite quickly became obsolete and only a replacement type made to keep outdated am radio receivers in operation - most were made during the worst years of the depression and QC does not appear to have been the primary consideration, either that or mis-handling of my NOS/NIB tubes must have been egregious. (Two have severely mis-aligned filaments relative to the grids, they work but are not great.)

Kevin

[HollowState]

Hmmm, the only difference I see is in the external overall height. The internal plate structure and mica supports look the same to me. I'd be more curious as to how they test.

[Andrewbee]

I have been dealing with A.E.S. for probably 20+ years, from when George Fathauer still owned the company (I think he sold it ~ 1995). The only issue I ever had was a incorrect tube, something like an ECC82 instead of an ECC83 and that was long ago. I told them about it and they sent me the correct one and told me to keep the incorrect one. I just got ~$200.00 worth of stuff (mostly resistors and caps) from them. I have no complaints.
I would say that the service has fallen off over the last few years (things like picking specific tube types / brands) but when I think about it, if as a business owner you have people wanting specific tubes you are going to lose efficiency/money if you have a member of your staff spending perhaps an hour to find a couple $10.00 items.
Multiply this a few times a day.
It probably costs more to store and inventory many of the tubes they have than to sell them at a couple bucks each.
One of the harsh realities of business.

[dsavitsk]

Originally posted by Andrewbee
if as a business owner you have people wanting specific tubes you are going to lose efficiency/money if you have a member of your staff spending perhaps an hour to find a couple $10.00 items.

Were these $10 items, you might have a point, but that fact that they are going to be sent back again suggests that they might have saved themselves the hassle. Also, the fact that they have now lost a pretty decent customer might matter.

[dsavitsk]

Originally posted by kevinkr
I have had the same problem with 71A, and whats more 50% of the NOS/NIB ones I have purchased have been bad - and as you know they are somewhat expensive. I currently have a mismatched pair in my headphone amplifier and can neither measure nor hear any audible differences. (It sounds really good!)

I've also got ones that are same date code, same brand and mismatched in height so go figure..

The problem with the 71A is that it quite quickly became obsolete and only a replacement type made to keep outdated am radio receivers in operation - most were made during the worst years of the depression and QC does not appear to have been the primary consideration, either that or mis-handling of my NOS/NIB tubes must have been egregious. (Two have severely mis-aligned filaments relative to the grids, they work but are not great.)

Frustrating. I am working hard enough on this project to make it look nice that I'm just not willing to put up with it.

Maybe it is time to find a different tube, then. Any suggestions on a 4 pin DHT with a low mu and the lowest rp possible? Filament needs to be under 500mA or so, too.

[kenpeter]

Would a 6A3 burning only 5V draw low enough current?

[kevinkr]

Originally posted by dsavitsk


Frustrating. I am working hard enough on this project to make it look nice that I'm just not willing to put up with it.

Maybe it is time to find a different tube, then. Any suggestions on a 4 pin DHT with a low mu and the lowest rp possible? Filament needs to be under 500mA or so, too.

The 71A does not have particularly low rp, I think you could select the 45 as an alternative as it's rp is similar.. (It's also wonderful sounding in headphone service.) The 6B4G or 6A3 are other options and have much lower rp than the 7A or 45..

Some of the German post office DHT might work well in this application but have odd sockets and 4V filaments. You might want to look at the AA, BA, and BAS.. They are available on eBay for not obscene amounts of money and are quite linear.. Most of the information about using them is in German unfortunately as they have not traveled far afield. (Although I do have some.) RFT, Siemens and Valvo all made these types.

[Cobra2]

I ordered a few "sale"-tubes a week+ ago (in pairs & quads), and; - all are different !!!
I guess if 10 people put in the same order, they all would get the same tube-spread.
They do however work ok.

Arne K

[Poindexter]

I've held my peace so far, but I'm gonna say it again.  A tube with the rp of both of these, but about three times the gm, and otherwise really kewl specs (though it's not qui-ite as linear as the 71A), available, cheap, is a teevee video amplifier tube hight 6T4.  There are, of course, other very similar tubes from the era for the same duty, all with similar chars, some differing only in pinout.  I picked the 6T4 over others as a replacement to the irritatingly microphonic 6AQ5 just because Jack was holding. You might want to look at some of these, if you're not married to the gorgeous coke bottle.

They do, in their favor, have heaters that stick 2-3mm out the ends of the cathode sleeves, so they glow very romantically.

Just a data point,

Poinz