I know this amplifier with Eimac tube but is TH version
https://drive.google.com/file/d/0B9FdcTDiNMIEZGpLRzc2ZDBTeDg/view
Hope can inspire You at some point
Greetings
https://drive.google.com/file/d/0B9FdcTDiNMIEZGpLRzc2ZDBTeDg/view
Hope can inspire You at some point
GreetingsI've got a pair of VT-127A tubes that are similar operating but a completely different bottle and I one day plan to make into a SET amp with them but that's years away. It is exceedingly rare to find actual amps made with these guys since they are so high voltage the cost becomes a prohibitor even if the tubes themselves aren't all that expensive.
What kind of amp are you looking to make with these? The datasheet gives a good layout of what you need for class AB AF output but you're looking at 250-400+W of output power if you follow the data sheet so you'll need HUGE transformers with high voltage ratings and a well-designed driver that can swing 300V grid to grid.
Single ended with these guys is a bit more sane as you'll only get about 20W output on a good day, the driver doesn't have to run much more than 100V, and the B+ supply only needs to supply maybe 300W.
I've got some 25T(and 24G) to get my feet wet with the high-power RF as an SE amp bit before working with the 100TL.
That schematic posed by Soundhappy should actually be close enough to work. The amplification factor of the TH is about double the TL but it'll definitely drive fine with the tube swapped.
What kind of amp are you looking to make with these? The datasheet gives a good layout of what you need for class AB AF output but you're looking at 250-400+W of output power if you follow the data sheet so you'll need HUGE transformers with high voltage ratings and a well-designed driver that can swing 300V grid to grid.
Single ended with these guys is a bit more sane as you'll only get about 20W output on a good day, the driver doesn't have to run much more than 100V, and the B+ supply only needs to supply maybe 300W.
I've got some 25T(and 24G) to get my feet wet with the high-power RF as an SE amp bit before working with the 100TL.
That schematic posed by Soundhappy should actually be close enough to work. The amplification factor of the TH is about double the TL but it'll definitely drive fine with the tube swapped.
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A nice and good recourse is http://www6.plala.or.jp/Michi/100TH SE amp.html
All of his amps are interesting. These RF-Tubes needs general driving into positive grid voltage, so a very well designed driver is needed. I would prefer solid state to drive these bastards.
Same with the 127a / 227 / 327.
All of these RF tubes are not for beginners.
All of his amps are interesting. These RF-Tubes needs general driving into positive grid voltage, so a very well designed driver is needed. I would prefer solid state to drive these bastards.
Same with the 127a / 227 / 327.
All of these RF tubes are not for beginners.
Hi. I also have a lot of those. The reason, why I didn't built already one, is I have no solution how to fix them in the chassis there are no sockets for these lovely looking radar tubes. Do you have any idea?
I was thinking of doing two half-circles of metal that attach to both grid and plate lugs with one towards the back and one towards the front and using stand-offs to rigidly mount the tube to the chassis. The 2kV B+ isolator for mounting to and passing through the chassis could look neat as well.
I wish I could say I have a lot of them as they are super cool but I only have the two.
I wish I could say I have a lot of them as they are super cool but I only have the two.
No need to run the Hi mu tubes at high voltages; I have built many push pull amps using 100TH,811a, 572b, 805 The 811a with 600 volts 100 watts out put transformer 2.2k. Used 6bl7 cathode followers. I don't think they sound good SE. 811a, 805's where used for record cutting amps. I have not tried Mosfets, the 6bl7 can handle 600 volts very simple circuit. Never seen a 100TL very expensive and rare
There is a reason why people don't use these . VT127A has Ra of around 6k . It's a 75TH with a 5V , 10.5A filament . Not easy to work with . I had to build mounting bases from blocks of teflon and had to have heatsink connectors custom made . The choke input , choke smoothed DC filament supply for the 2 x VT127A weighed 30kgs . I ran these zero bias at around 600V using a 7236 cathode follower and TZ20 driver . The amp needed feedback , was too large to put in a box (built on a Tek scope trolley) and was a potential deathtrap due to the exposed topcaps
75TL is the one to find... much prettier and easier to use but extremely rare . If you are really keen to build an amp using these big old triodes , HK54 is worth looking in to
316a
It can't really drive anything unless the next stage is a cathode follower The curves are not the best indicator of linearity as this is typically used as a modulator, like an 811A, rather than an input stage running at a few mA.
T20 is a similar-looking tube. Mu of 20. Much easier to use. It's specs are similar to a 3C24 or 15E.
316a
The curves are not the best indicator of linearity as this is typically used as a modulator, like an 811A, rather than an input stage running at a few mA.T20 is a similar-looking tube. Mu of 20. Much easier to use. It's specs are similar to a 3C24 or 15E.
316a
I worked this tube 100TH and got 40w with Michimori type driver, but a problem is the cooling of the electrodes in the grid and the anode. Unfortunately i only have one tube so the project is in stand by, but if interested, i can review the project data
this is the 100TH tested scheme
this is the 100TH tested scheme
Attachments
I built an amp using VT127A which was very challenging and ended up being too big and heavy to fit in a box . VT127A is nothing like a 100TL , it is similar to a 75TH but with a 5V 10.5A filament . 100TL are very rare , do you have a pair or are you just considering building an amp based on these ?
316a
100TL curves do not look like a convenient or good audio amp. You could run zero-bias near 1000V and near 100W Pdiss. However the damping factor is poor, and the grid is a very ugly load on the driver. With grid negative it is nearly infinite impedance. With grid 40V positive, 4k impedance. At peak swing near 110V the grid sucks 70mA which is like a 1.7k impedance. About 4 Watts of peak power. Few tube drivers can drive such a load. Note a very sudden shift of grid impedance right around zero bias, right at your smallest signals.
Attachments
Hallo 316a,
Thanks für the Info. On one Datasheet from the Eimac 217A was the Info, that the 100TL also can be used. That was the reason for my thinking. In real, I have no 100tl yet...put some 127A. So...lets build with the 127A BUT i found no got schematic or plan. Is it possible to send me more Infos about your 127 amp? Pm ist also perfekt. BTW...I have two 75t (l or h), I dont know.....are there optical diffents? Greedings
Hallo PPR,
Thanks for the Info...“again what learnt“
Thanks für the Info. On one Datasheet from the Eimac 217A was the Info, that the 100TL also can be used. That was the reason for my thinking. In real, I have no 100tl yet...put some 127A. So...lets build with the 127A BUT i found no got schematic or plan. Is it possible to send me more Infos about your 127 amp? Pm ist also perfekt. BTW...I have two 75t (l or h), I dont know.....are there optical diffents? Greedings
Hallo PPR,
Thanks for the Info...“again what learnt“
75TH (high mu) 75TL (low mu) . 75TL are extremely rare . The VT127A is very challenging to use . First you need to find good tubes . Then you need to manufacture a mounting base (I used a block of teflon and screw connectors) and locate or manufacture heat dissipators . Then there is the filament supply . I used choke input , choke smoothed DC , the supply itself weighed 30kg . I ran mine single ended at 600V , zero grid bias with a 7236 choke-loaded DC coupled cathode follower at the limits (75mA) of the 5K output transformer I had to hand . You need some colour in the VT127A anode for correct operation , which I could not achieve . I also had to use anode to anode feedback to the driver . It was a fun project but I was never happy with it and it got torn down , it would also have been too big to fit in a box
316a
316a
Hi,
There are no letters on...so I cant See L or h. I have These Tube so 10 years..and no Memory about the purchase.
I have 8 nos tubes 127a, so I hope there are some good ones. The mountingbase, chassis/ box is absolute no Problem. For me, the schematic is the Point. 600v, 5k opt, and so on sound good , First of all. The filament power, i woud use a switching power supply (meanwell)....
What are the point, that you are not so happy with the amp? What about the sounding?
There are no letters on...so I cant See L or h. I have These Tube so 10 years..and no Memory about the purchase.
I have 8 nos tubes 127a, so I hope there are some good ones. The mountingbase, chassis/ box is absolute no Problem. For me, the schematic is the Point. 600v, 5k opt, and so on sound good , First of all. The filament power, i woud use a switching power supply (meanwell)....
What are the point, that you are not so happy with the amp? What about the sounding?
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Good luck using a switch mode supply , I had issues using Eltek (telecoms grade) switchmodes , cold startup current too high , even for a 20A rated supply . You may find that choke input , choke smoothed with an NTC in series with the mains transformer primary (slow start) is the way forward for filaments . I can only suggest prototyping before considering a box . Although VT127A had a lively , powerful sound , it was very euphonic compared to that of a 2A3 amp
316a
316a
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