Yes, it is a image for a wrong example posted in a old thread about a wrong GM70 datasheet.
Commstech you are correct. There is an English language only data sheet that shows an incorrect pin out.
Fullrangeman, the pins are soldered to the heavy wires that come out of the base of the tube. I don't see a safe way to remove the aluminum shell, and would rather not have one implode while attempting it.
Fullrangeman, the pins are soldered to the heavy wires that come out of the base of the tube. I don't see a safe way to remove the aluminum shell, and would rather not have one implode while attempting it.
Epcos makes an NTC thermister which is perfect for this: B57153S0479M000 – 4.7Ω cold and <150mΩ @ 3A. I prefer these (passive) devices to solid-state as they don't add any tube/SS interaction to the filament, (which in this case is clearly in the signal path).
Kevin, I just realized something; are these the GM-70's that were "lost in shpping" and that you were waiting forever for? If so, I'm glad you finally got them, (and that you'll be getting "proper" replacements for them).
I'd be very interested in hearing your impressions of them vs. Ulyanov/Foton once you get some intact ones.
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Yes, these were the ones that were "lost" in U.S. customs for three weeks..
The replacements will not be "Souz" as far as I know, they will be date code 1973 which will make them the earliest ones I have.
The graphite ones currently in the amp are of unknown manufacture, from a lot with tubes ranging from 1978 to 1988, all have OTK inspection marks on them. They're very consistent performers and are well made.. They've been in the amps since January and given a recent health issue they must have close to 1200 hours of use so far, no inclination to replace unlike the coppers which were clearly ready at just a little over 1000 hours. No bias adjustments have been necessary over that time, unlike one of the coppers which had dropped about 20mA over the year.
The replacements will not be "Souz" as far as I know, they will be date code 1973 which will make them the earliest ones I have.
The graphite ones currently in the amp are of unknown manufacture, from a lot with tubes ranging from 1978 to 1988, all have OTK inspection marks on them. They're very consistent performers and are well made.. They've been in the amps since January and given a recent health issue they must have close to 1200 hours of use so far, no inclination to replace unlike the coppers which were clearly ready at just a little over 1000 hours. No bias adjustments have been necessary over that time, unlike one of the coppers which had dropped about 20mA over the year.
Sorry you won't get to try the "Souz" – I think your seller should give you a partial refund since the chance to try a different make was (I believe) one of the reasons you bid on the Souz. Still, getting some from '73 will be nice; (earliest I have are October '74).
Bet they're Ulyanov's. Ulyanov were the chief makers of large triodes (ГМ-70, 6S33S, ГУ-48) during the late '70's and often made logo-less OEM versions that other manufacturers re-branded and sold as their own. Many of the Ulynaovs from that period have shown up in bulk lots throughout the Russian territories. They're quite good – dependable, rugged, and very consistent – (almost any two would constitue a "matched pair" by most tube sellers' standards).
Yeah, I remember debating copper vs. graphite with you a while back, and you being an advocate of copper plates (and not without good reason), but have now joined the ranks of us who actually prefer the graphites overall, and I don't blame you. If midrange were the only consideration, I'd use nothing but copper, but when you weigh in bass extension, power handling, and stability (not to mention price) it's hard to justify running copper plates.
Curiosity and the reasonable price were the primary reasons I bid on those tubes - was not sure what I was getting.. I suspect the replacements will be interesting given their vintage.
I suspect you are right about the unmarked tubes, I've suspected for a long time that Ulyanov was a high volume maker of this type and the 6C33..
Interesting story on the graphite vs copper, for some reason at the last tube change I decided to give the graphites another listen, and ended up thinking this really isn't bad at all, consistency and what seems to me like a very balanced performance overall won me over. I don't think there is any problem with the midrange with this tube, perhaps the fact that it has slightly better bottom end is largely responsible for the comments. I particularly like the absence of strange crackles and rustles during warm up which some of my coppers do. I have two new pairs which I recall are slightly different pair to pair - I think they were made by different makers but would have to dig them out to be sure.
I suspect you are right about the unmarked tubes, I've suspected for a long time that Ulyanov was a high volume maker of this type and the 6C33..
Interesting story on the graphite vs copper, for some reason at the last tube change I decided to give the graphites another listen, and ended up thinking this really isn't bad at all, consistency and what seems to me like a very balanced performance overall won me over. I don't think there is any problem with the midrange with this tube, perhaps the fact that it has slightly better bottom end is largely responsible for the comments. I particularly like the absence of strange crackles and rustles during warm up which some of my coppers do. I have two new pairs which I recall are slightly different pair to pair - I think they were made by different makers but would have to dig them out to be sure.
Good point. I also think that the "exclusivity factor" helped the copper plates attain their mythical status. As I've said before, when the '70 was first introduced to the world, there wasn't such a widespread bias toward the copper plates; (in fact, some people used to knock them for their lower dissipation).
The harder they became to get, however, the more people touted copper plates as "superior". And yes, you can hear some difference in midrange definition, but it's just not that big. I have one pair of copper plates that I use when I rearrange my system for bi-amp or tri-amp, but when I'm running full-range – (which is most of the time) – it's graphite.
UK shipping companies are just as bad as any others.
In the 1970s I sat in a train waiting for it to leave and the freight car was being loaded. They just chucked the packages across the platform and into the car.
More recently post 2000 I was driving a car and there was an obstacle course of stuff all over the road and as soon as there was enough clear road ahead I spotted a couriers van with the back doors wide open traveling along laying the obstacle course I was driving through. Another driver got along side and stopped him.
In the 1970s I sat in a train waiting for it to leave and the freight car was being loaded. They just chucked the packages across the platform and into the car.
More recently post 2000 I was driving a car and there was an obstacle course of stuff all over the road and as soon as there was enough clear road ahead I spotted a couriers van with the back doors wide open traveling along laying the obstacle course I was driving through. Another driver got along side and stopped him.
The replacement tubes arrived today, and I have to say I have never seen a better job of packing. Needless to say the tubes arrived in perfect condition, and all passed rudimentary inspection with flying colors.
The replacement tubes are likely Ulyanov with a 1973 date code which makes them my earliest.
I will keep searching for the Souz version as I am still curious.
I now have a dozen designated spares, eight of which are unquestionably good, two well used coppers which I ran over 1K hours, and a couple of graphite type with each with a little bubble in the glass. The current graphite plates in the amps are getting up there in hours, but sound and perform fine.
The replacement tubes are likely Ulyanov with a 1973 date code which makes them my earliest.
I will keep searching for the Souz version as I am still curious.
I now have a dozen designated spares, eight of which are unquestionably good, two well used coppers which I ran over 1K hours, and a couple of graphite type with each with a little bubble in the glass. The current graphite plates in the amps are getting up there in hours, but sound and perform fine.
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