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Amp Schematic for 100TL
Amp Schematic for 100TL
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Old 28th November 2018, 01:42 PM   #11
316a is offline 316a  England
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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.

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Old 29th November 2018, 07:16 PM   #12
popa marius is offline popa marius  Romania
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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
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Old 19th August 2019, 12:00 PM   #13
nautilussigma is offline nautilussigma  Germany
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Hello,

the time go's by...so, at the time there no schematic for the 100TL (or the V-127a I learned) ....so, i will again ask for help...
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Old 19th August 2019, 01:36 PM   #14
popa marius is offline popa marius  Romania
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Hello,
Specifically what i can help you with this tube 100 th ?
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Old 20th August 2019, 03:22 PM   #15
316a is offline 316a  England
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Quote:
Originally Posted by nautilussigma View Post
Hello,

the time go's by...so, at the time there no schematic for the 100TL (or the V-127a I learned) ....so, i will again ask for help...
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
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Old 21st August 2019, 03:54 AM   #16
PRR is offline PRR  United States
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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.
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Old 21st August 2019, 10:57 AM   #17
nautilussigma is offline nautilussigma  Germany
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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“
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Old 21st August 2019, 11:37 AM   #18
316a is offline 316a  England
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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
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Old 21st August 2019, 01:34 PM   #19
nautilussigma is offline nautilussigma  Germany
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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?

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Old 22nd August 2019, 03:27 PM   #20
316a is offline 316a  England
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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

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