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Old 21st April 2012, 07:40 PM   #1
JohanB is offline JohanB  Sweden
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Default Those Magnificent Television Tubes

There are a lot of these tubes out there. I don´t mean the picture tube, but all the other ones. F. ex. the well known audio tubes 6CG7, 12BH7 and 6CW7 etc. are actually designated for TV-sets.

There are a lot of other quality tubes in Europe & US, costing almost nothing, like PL84, ECF82, PC86, PF86 ECF83, PL81 etc (P stands for 300mA heater current & E for 6,3V voltage)

F.ex. the EC/PC86 triode will outperform ther popular ECC88/6922 types with lower noise and higher gain & linearity.

In US there are 450 & 600mA heater current tubes I think.....(due to 115V mains & series connected heaters)

When a manufacturer sold a tv-set with 20-30 tubes and guarantee, the incorparated tubes have to be of very high quality.

If you have made an amp or other things with these tubes, please give a hint or schematic diagram in this thread.

Regards, Johan

Last edited by JohanB; 21st April 2012 at 08:09 PM.
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Old 21st April 2012, 08:06 PM   #2
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F.ex. the EC/PC86 triode will outperform th popular EC88 types with lower noise and higher gain & linearity.
That's an interesting triode. Data sheet here. It would seem the same sort of extraordinary precautions against parasitic oscillation employed with the 6С45П (6s45p) and the 5842 are in order, when the EC86/PC86 is wired common cathode.
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Old 21st April 2012, 08:18 PM   #3
JohanB is offline JohanB  Sweden
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Originally Posted by Eli Duttman View Post
That's an interesting triode. Data sheet here. It would seem the same sort of extraordinary precautions against parasitic oscillation employed with the 6С45П (6s45p) and the 5842 are in order, when the EC86/PC86 is wired common cathode.
The EC/PC86 were originally made for the UHF input/mixer/oscillator so better put a few hundred Ohms resistor close to the grid input to keep it calm.
Not extra ordinary, but the same precautions as recommended for the ECC88/6922.

Johan
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Old 21st April 2012, 09:52 PM   #4
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It's a grounded grid amplifier type, with high gm and multiple grid connections. That kind of tube comes damned close to oscillating in the cardboard box. Wire 3X 3.3 KOhm carbon comp. stoppers in a "cone" to the 3 grid connections. Put ferrite beads on the heater supply wires. Finally, put a 100 Ω carbon film stopper on the plate. When wiring up "in box oscillators" common cathode, take no prisoners!
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Old 21st April 2012, 10:15 PM   #5
JohanB is offline JohanB  Sweden
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Originally Posted by Eli Duttman View Post
It's a grounded grid amplifier type, with high gm and multiple grid connections. That kind of tube comes damned close to oscillating in the cardboard box. Wire 3X 3.3 KOhm carbon comp. stoppers in a "cone" to the 3 grid connections. Put ferrite beads on the heater supply wires. Finally, put a 100 Ω carbon film stopper on the plate. When wiring up "in box oscillators" common cathode, take no prisoners!
Oscillating in the box....HeHe...A little overkill with the ferrite beads....

Another very interesting tube for compressor/expanders is the very low noise vario-mu EC/PC900 Originally made for regulated TV VHF input amplifier
Square root caracteristic over more than four decades.......Makes very low distorsion in a push-pull configuration.

Johan
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Old 22nd April 2012, 04:21 AM   #6
AJT is offline AJT  Philippines
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the 6LU8's makes very good audio power amps....
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Old 22nd April 2012, 05:11 AM   #7
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Originally Posted by JohanB View Post
If you have made an amp or other things with these tubes, please give a hint or schematic diagram in this thread.

Regards, Johan
Been there; done that: Le Renard

The 6BQ6s, especially, make great audio finals, even though there is no mention of such use mentioned anywhere in the spec sheet. These sound as good as the 6V6, but can handle a lot more power, and some spec busting doesn't hurt at all, but improves the sonic performance.

The 6BQ7s also make excellent cascoded LTPs. This is another type that doesn't mention audio applications, and it does have some squirrelly plate characteristics (undocumented variable-u feature?) that makes it a bit more difficult to find a good audio load line. However, for this particular application, it works quite good.
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Last edited by Miles Prower; 22nd April 2012 at 05:21 AM.
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Old 22nd April 2012, 06:32 AM   #8
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Quote:
Originally Posted by Eli Duttman View Post
It's a grounded grid amplifier type, with high gm and multiple grid connections. That kind of tube comes damned close to oscillating in the cardboard box. Wire 3X 3.3 KOhm carbon comp. stoppers in a "cone" to the 3 grid connections. Put ferrite beads on the heater supply wires. Finally, put a 100 Ω carbon film stopper on the plate. When wiring up "in box oscillators" common cathode, take no prisoners!
Eli, I agree, this is the right approach.

When I use PC86s, I remove the socket-contacts for the two grid terminals located next to the two anode terminals, and one of the anode terminals also.
Use pin 1 for anode & pin 6 for grid, and remove the unnecessary metal connected to the other terminals! If you are not working at UHF, multiple terminals are a weakness, not a benefit - they present transmitting (anode) and receiving (grid) 'antennas' - undesirable feedback paths that cause oscillation.

I also used ferrite chip-beads in the anode (Murata BLM21A121S), and high values of carbon-comp grid stoppers.

The PC86, and other tuner triodes are designed for cascode operation, and this is where they give their best. e.g. Shunt-Cascode, Single-stage: B+ = 200V, gain = ~280, highly linear swing all the way from 0V to 160V, output Z = 20K.....

Some very nice Russian near alternatives are available, too - e.g. 6С3П with a normal 6,3V heater.
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Old 22nd April 2012, 09:28 AM   #9
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Some make very nice triodes, see here: High Gm driver pentodes
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Old 22nd April 2012, 12:12 PM   #10
JohanB is offline JohanB  Sweden
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About the extremely well built and plentiful EL/PL36, (EL360) 6CM5/25E5

EL36: Applications in Audio

Some links are gone in this article, but still very intresting.

Johan
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