• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Those Magnificent Television Tubes

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TonyTecson

TonyTecson

Member
Joined 2003
nuvistordave said:
6KN6; still pretty cheap; also 42KN6. Kewl thing about these is no need to
bother with multiple secondary taps on OPT; those cathodes will handle the load.
(I bought out Antique's stock when they went on sale 20 years ago happy hunting)
There are 3 types:
1) The original Sylvania 'Doubles' These have 3 A fil current and match the pinout
on the tube data sheet.
2) Japanese Singles: Green stripe on bottom; 3A and 6KN6 pinout.
3) American Single Plate: These are actually 6KD6's; 36KD6; 2.75A fil current and
their pinout has the extra grid wires as on the 6KD6 pinout.
Click to expand...

yes, i can get those for less than 8 dollars in manila...
 
D

deicide67

Member
Joined 2008
I’m tinkering with the 21LG6 in triode. I’ve managed good results at 400V B+ at 80mA into a 5K load.

Has anyone tried this tube in triode at say, 450-480VDC? The power transformers I would like to use are going to give me a B+ or around 475V.

I know I can just watch for screen melt down, but I figured I’d check first to see if anyone has tried it at my proposed B+.

Thanks!
 
D

DonYY

Member
Joined 2018
I have a pair of screen driven 6DQ5 sweep tubes with 800V on the plates that work just fine as an AM transmitter modulator. Generally speaking, sweep tubes can handle very high voltages, have big cathodes that allow large currents to be drawn, but come up short on plate dissipation by comparison. I don't think you could hurt the tubes with 475V. Not even close.
 
N

nuvistordave

Member
Joined 2009
Time to build an OTL with my massive stash of 42kn6's.
Crazy drive cathode follower output and circlotron bridged
Single ended. 3 heaters in series runs right off the mains
No problem but should run a speaker fuse just in case.
90 to 100 volts on the plates should work fine
It should be able to drive around 80v p - p into 8
Ohms. Only for a short time though since the plate
Efficiency is rather low. Should be fun...
 
Kay Pirinha

Kay Pirinha

Member
Joined 2011
nuvistordave said:
Time to build an OTL with my massive stash of 42kn6's.
Crazy drive cathode follower output and circlotron bridged
Single ended. 3 heaters in series runs right off the mains
No problem but should run a speaker fuse just in case.
90 to 100 volts on the plates should work fine
It should be able to drive around 80v p - p into 8
Ohms. Only for a short time though since the plate
Efficiency is rather low. Should be fun...
Click to expand...
:eek: :eek: :eek:
Best regards!
 
DIYBras

DIYBras

Member
Joined 2015
6CL6...

smoking-amp said:
News? ....

<snip>

Oh, and 6197 (6CL6) tubes were on sale for a while on Ebay for $0.32 each in big quantities. (I see them at around $1 each now.) Got a few of them. Similar to a 12BY7 except higher knee voltage. Very consistent tubes on the curve tracer, almost randomly matched. Should make a good hefty driver tube.
Click to expand...

Some time ago I made a hybrid amp, with Lateral MOSFETs in PP, with 6CL6 choke-loaded in PENTODE mode, with G2 feedback from output. I'm based on some Patrick Turner project. Resulted in high DF (110 re 8R load, only for curiosity, I'm not fan of outrageous high DF and not believe in any benefit in having eg. DF>10 unless crossover in loudspeaker is all over the place), and only moderate low distortion (0,3% or so at 1W), higher than triode driver without output feedback. Sounded very good, with a lot of 2H.
I borrowed it for a friend of mine, and he uses this amp since then.
 
DIYBras

DIYBras

Member
Joined 2015
TonyTecson said:
nice to see you posting again smoking-amp...... :D

re 6CL6, i used that tube as voltage amp in my el34 paralleled set and i replaced that with an el84, the tube bias runaways after 30 minutes of play....otherwise they are very nice sounding...
Click to expand...
In my project I've mentioned the 6CL6 behaved very good, without any runaway trouble, but it have cathode bias (resistor).
 
DIYBras

DIYBras

Member
Joined 2015
DonYY said:
I have a pair of screen driven 6DQ5 sweep tubes with 800V on the plates that work just fine as an AM transmitter modulator. Generally speaking, sweep tubes can handle very high voltages, have big cathodes that allow large currents to be drawn, but come up short on plate dissipation by comparison. I don't think you could hurt the tubes with 475V. Not even close.
Click to expand...
Yes for anodes only, and some people (David Berning, for example), uses some H tubes with 1650Vdc on anodes, with it's chopper impedance converter. I've seen some projects for direct ESL drive, with near 3kVdc PSU or more (!!) on some types.
 
DIYBras

DIYBras

Member
Joined 2015
nuvistordave said:
Time to build an OTL with my massive stash of 42kn6's.
Crazy drive cathode follower output and circlotron bridged
Single ended. 3 heaters in series runs right off the mains
No problem but should run a speaker fuse just in case.
90 to 100 volts on the plates should work fine
It should be able to drive around 80v p - p into 8
Ohms. Only for a short time though since the plate
Efficiency is rather low. Should be fun...
Click to expand...
All direct from the mains or only the heaters?
I've made an little OTL for a 1600R speaker feed directly from the mais (using PCL86+EL86, like in some Philips OTL TV audio section, with some touch), but I use it with a Chinese USB/Bluetooth device that plays FLAC and WAV (for daily use) and a Digital Audio receiver with TOSLINK, for movies and Hi-Res music** (so is user-insulated form the mains)

**Homemade receiver with CS8416 + an ESS9023 from DIYINHK.
 
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