I was adding the heat dissipation connectors to Steve's amps.... I had forgotten that we had discussed those for him in Colorado and he reminded me about them in Maryland... so I had a pair of the medium sized Eimac originals..... the first went very smoothly.... but the second.. well.. I can hardly say this, but it broke the tube right at the top pin/glass interface... I was holding the heat dissipation connector with my left hand and a small straight screwdriver with my right... all I did was tighten the thing on there... barely any pressure at all... crack!
the glass is thin at the seals... where it meets the uranium glass... so just take my gaff as a warning... go *super* easy when doing anything around those pins...
and don't worry Steve... I had an NOS pair in my stash.. so you still have a brand new set...
I haven't broken one like that but Josh has mentioned doing so in the past. I always go gentle on those connectors too. sucks they are so fragile that way! I wonder if that one maybe had some sort of inherent flaw in the glass seal area?
The plate/grid leads are made of tungsten which is quite brittle and won't bend/deform at all, so the glass is what gives, probably. >:-/
I can add up what I have and maybe I have an unmatched single I could part with.
With all the hoopla around these tubes lately (all the DIY builds and chatter about same), they are getting a lot harder to find than even a couple years ago. :-/
I just noticed this. I may have a better solution for you. Is the pair you are replacing mine with the winged version? If so I'll trade you the single winged tube from the pair in which one was broken for a matched pair of 75TLs without the wings if that works for you.
Just a quick question from an outsider ..
( I sometimes end up copied on correspondance from Thom or Lynn )
Are you guys using the Eimacs mainly for power reasons or are they outstanding on tone & sound quality too ?
If the latter then how do they compare against things I'm familiar with, like Ge VT4cs or any sort of 212s ( 4212s ) of which I've heard three types .... or smaller favourites like 2A3s ?
Just interested .
with the risk of making it even harder to get the next pair on eBay, I will say that the 75tl is my absolute favorite tube at the moment.... I normally just say "top five" or some such thing, but it is pushing all my buttoms at the moment....
but it isn't easy to get five watts from 10Hz to 50kHz from it... fair warning...
well, I think it's some of both. They do have a really high dissipation rating for the size of the plate, etc. (but then the filaments are a bitch)... as far as tone comparisons... I find them very clean. ultrafast but smooth, without the overly warm sound that some other tubes can bring. e.g. not overly lush, but very true and clear sounding. (at least to me... )
well, from the specs, it looks like an A2 tube... but it doesn't have to be... I just finished up Steve's amp.. it is running just a bit over 500V and gets little more than a watt out.. A1.... but that is all the power he needs and it certainly sounds very sweet on his speakers at this operating point...
but i run mine at nearly a thousand volts... and get more power... five watts where I have the current set now... but that can go up to about ten watts by twiddling some knobs...
and.. let's see.. filaments.. well, they aren't so bad... don't let Ed scare you... they are the same power as an 845... so no sweat... to me, it is the 5k Ri that is the killer... if you canfind me an iron guy bettter than dave, private message me.... (big hearty laugh) .. my amp that uses dave's iron runs the 75tl at 1000V, 60mA, and has bandwidth well beyond 20 to 20... with that 5k Ri...
so, yes.. the tube has cylindrical structure... and thoriated majesty... and big sound... I encourage you to try one when you get the urge....
