The 8068 is another great oddball tube..
I wouldn’t know about the 8417 but i imagine its harder to design with
Even back in the day.. audio wasnt the primary marked. and stuff was built to a price.
Ever wondered why the anodes in the 50s where black carbonized? and nowadays there Gray?
Activation of Anode Material - YouTube
I wouldn’t know about the 8417 but i imagine its harder to design with
Even back in the day.. audio wasnt the primary marked. and stuff was built to a price.
Ever wondered why the anodes in the 50s where black carbonized? and nowadays there Gray?
Activation of Anode Material - YouTube
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Tipping Off A 5687 Dual Triode Tube - YouTube
If you have the materials, you can roll tubes in your garage
If you have the materials, you can roll tubes in your garage
I think, but cant prove definitvely that its just a stretched beam tetrode based on some existing tooling.
But in any case, personally i dont think its worth it, just because there are types like the GU50 around which is a crazy well built tube but has some drawbacks like : Large spread in production parameters and low VG2 specification. However in triode these are absolutely fantastic and something that overbuilt is NEVER going to be made again.
But in any case, personally i dont think its worth it, just because there are types like the GU50 around which is a crazy well built tube but has some drawbacks like : Large spread in production parameters and low VG2 specification. However in triode these are absolutely fantastic and something that overbuilt is NEVER going to be made again.
Another way to say it is that type 8417 was a bridge too far. They could *just* be made in their day, and can't be made at all today. Type 7591 is almost the same degree of difficulty.
We also can't land a human on the moon this decade, for many similar reasons.
YOS,
Chris
Yep missing a lot of data. Vg2 is always 225V. Interesting they quote a g1 max current but only at one operating point. Looks like UL is at an HT of 600V max or so. Heater current is good.
Think if I was planning an amp would use cascade LTP (2x2sk170 JFET and 12ax7 at ~.5ma with gain of 400). Then ECC88 cathode buffer.
Think if I was planning an amp would use cascade LTP (2x2sk170 JFET and 12ax7 at ~.5ma with gain of 400). Then ECC88 cathode buffer.
Having hand wound 23 uM wirebonding wires onto a coil shaper for experiments in our lab on a near daily basis for some months I can recommend to just don't do it because you'll start to look this this guy -->
I don't know what to think of the shape of that KT170 bottle, it is a bit of an ugly duckling if you ask me
Some commercial amplifiers were made with type 8417, even a Dynaco (model MkIV) but it all happened at the end of the vacuum valve era. A lot of these have since been converted to less impressive but more sustainable valves in the 6550/KT88 family. Done some myself. Regretted it, but did it.
Today's remnant of those glory years are the compactron sweep valves - built to blast out soap operas an average of 8 hours per day, full tilt boogie, for years. Back when the US military needed reliable valves they preferably chose from large production lines. Small production "boutique" manufacture was only as a last resort. When lives depend on consistency, you want big production numbers. Even Raytheon made sweep valves, and still available affordably, but not forever.
YOS,
Chris
Today's remnant of those glory years are the compactron sweep valves - built to blast out soap operas an average of 8 hours per day, full tilt boogie, for years. Back when the US military needed reliable valves they preferably chose from large production lines. Small production "boutique" manufacture was only as a last resort. When lives depend on consistency, you want big production numbers. Even Raytheon made sweep valves, and still available affordably, but not forever.
YOS,
Chris
We had the same thing here with another tube, the EL503/520.
If you want to know more about that tube, there is the German language article by Jogis. Die EL503 - Story
The EL503 was never produced in quantities like the 8417. So there was never enough production for spares to be available. So now prices for these tubes are crazy... 100USD for one NOS is not unheard of.
The EL503 was the final audio power tube Philips developed i think, and its sad that production ceased shortly afterwards. as you can get 50W out of a pair PP with 250V anode. at like 2.5K anode-anode. With only 12V RMS drive.
The E130L is also capable of doing this with even less drive, but this tetrode requires an extra 150V screen supply.
But the E130L is an industrial tube that was FAR more expensive back in the day, so no audio companies used it.
If you want to know more about that tube, there is the German language article by Jogis. Die EL503 - Story
The EL503 was never produced in quantities like the 8417. So there was never enough production for spares to be available. So now prices for these tubes are crazy... 100USD for one NOS is not unheard of.
The EL503 was the final audio power tube Philips developed i think, and its sad that production ceased shortly afterwards. as you can get 50W out of a pair PP with 250V anode. at like 2.5K anode-anode. With only 12V RMS drive.
The E130L is also capable of doing this with even less drive, but this tetrode requires an extra 150V screen supply.
But the E130L is an industrial tube that was FAR more expensive back in the day, so no audio companies used it.
What a beautiful website! My German is over half a century rusty, so will take me a while to drill down, but looks worth the time. Thanks so much.
Chris
ps: 100USD for a classic valve is *nothing*. European oxide cathode beam valves, American brand-name thoriated tungsten filament 50-watters, or anything that rich guitar players think might help them sound like Hendrix - somebody will splurge big.
We DIYers *should* be free from these cults.
Chris
ps: 100USD for a classic valve is *nothing*. European oxide cathode beam valves, American brand-name thoriated tungsten filament 50-watters, or anything that rich guitar players think might help them sound like Hendrix - somebody will splurge big.
We DIYers *should* be free from these cults.
Lets Begin a list of sleeper tubes? Im sure i can have the Mods make it a sticky.
Just a list of anything available NOS under 10USD per tube.
First thing on the list: EF184/6EJ7 they literally made the tube by the millions. NOS can be found in practically every brand for decent prices. Same applies for the EC family of tubes. Want something as linear as E288CC but dont want to pay the price? EC86 E86C/EC806S may do the trick.
Just a list of anything available NOS under 10USD per tube.
First thing on the list: EF184/6EJ7 they literally made the tube by the millions. NOS can be found in practically every brand for decent prices. Same applies for the EC family of tubes. Want something as linear as E288CC but dont want to pay the price? EC86 E86C/EC806S may do the trick.
USD $200 for a tube that has a finite life......I don't think so.
Why spend $400 for 250 watts when I'm getting 200 to 300 watts from $30 to $40 worth of tubes (2 X 36LW6 or 2 X 26HU5). See posts #55 and 56 here:
UNSET is coming?
It has been known for a long time that having the plate on pin 3 and the heater on pin 2 leads to arcing between the two pins since the heater is usually grounded or operated at a low voltage level. The arc often happens in the tube socket or inside the base of the tube. Early TV sets used 6L6 types as the sweep tube. Arcs happened, so the 6BG6 was born, a 6L6 with the plat pin on a top cap. Later vintage smaller TV's used an octal (6AV5) with a different pinout to fix the arcing problem.
The 8417 had issues with it's cathode coating. Tiny flakes could migrate to the close by control grid causing shorts or leakage leading to a runaway tube.
This was solved with a "diffusion bonded cathode" in the pulse regulator triodes used in TV sets. It's mentioned in the data sheet for many of them look at the GE 6HV5A data. It's a 35 watt frame grid triode with a Mu of 300 and a Gm of 65000. I have yet to tame that beast.
I'm hesitant to mention actual valve numbers because "scalpers" (I'm certain that the same thing must occur everywhere - folks buy concert tickets early for resale at "scalping" prices) will ruin things for DIYers. A certain sticky thread on a certain forum with insight and hard data from a certain dedicated DIYer might, just might, be a great source, for those on that certain forum.
I'll PM you about "the valve from the underworld." if I can figure out how to do it.
YOS,
Chris
I'll PM you about "the valve from the underworld." if I can figure out how to do it.
YOS,
Chris
Oh man a tube too far. I saw a picture in the other thread about the 13BG5, any chance you could say how those fared in screen drive?
I have an old material datasheet from Transene that shows that there was a special cathode paste formula used in tubes with very close Grid spacing. Nowadays they cut back the varieties of emission liquid they sell to about three or four products last time i checked.
I know because i know someone who is rolling tubes in his garage, about 80miles from where i live.
Last time i heard he had made some dull emitter tubes.
I have an old material datasheet from Transene that shows that there was a special cathode paste formula used in tubes with very close Grid spacing. Nowadays they cut back the varieties of emission liquid they sell to about three or four products last time i checked.
I know because i know someone who is rolling tubes in his garage, about 80miles from where i live.
Last time i heard he had made some dull emitter tubes.
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Having hand wound 23 uM wirebonding wires onto a coil shaper for experiments in our lab on a near daily basis for some months I can recommend to just don't do it because you'll start to look this this guy -->
I don't know what to think of the shape of that KT170 bottle, it is a bit of an ugly duckling if you ask me
I used to work with 50awg magnet wire but it looks like 23uM has me beat. I agree the bottle is ugly.