tv tubes have lower G2 ratings, but as tubelab tortured a lot of those, there are sweep tubes that can be used as a triode, 6AV5 is one of them as i recall...
it is also well known that not all sweep tubes can operate triode with the g2 tied to plate....
as SY posted here, the 6LF6 can be operated in enhanced triode mode, with g1 at 0 volts and G2 as input pin....and the EL509 can sub for the 6LF6...
my pp 6LU8 12 watter is a fine example of pentode mode, plate at 300+ volts and G2 at 120volts regulated, sound fabulous to my ears....
I have not tested this tube but, according to GE 6KD6 data it seems to be quite similar to PL509. So it should be used very well.
I would recommend you to try the simplest version with cathodyne phase splitter. Keep Ug2 adjustable, then you can search the optimum condition
for the output tubes.
Ug2 and Ug1 should be stabilized. I also recommend to have bias- and drive balance adjustments as in my schematic.
You can use 6SL7 as a front end tube instead of 6F12P if a bit lower sensitivity is sufficient for you.
I have used below circuit with 5881/6L6. I can be used as well.
I would recommend you to try the simplest version with cathodyne phase splitter. Keep Ug2 adjustable, then you can search the optimum condition
for the output tubes.
Ug2 and Ug1 should be stabilized. I also recommend to have bias- and drive balance adjustments as in my schematic.
You can use 6SL7 as a front end tube instead of 6F12P if a bit lower sensitivity is sufficient for you.
I have used below circuit with 5881/6L6. I can be used as well.
An externally hosted image should be here but it was not working when we last tested it.
Last edited:
tv tubes have lower G2 ratings, but as tubelab tortured a lot of those, there are sweep tubes that can be used as a triode, 6AV5 is one of them as i recall...
it is also well known that not all sweep tubes can operate triode with the g2 tied to plate....
Back in the beginn of the 70th, when I did all this measurements, it was not known. There where curves about Uag2/-Ug1 for quite similar but smaller tubes like QE05/4, EL36,E130L but not much data was avaiable for the EL509 or the later 519.
Nice that nowdays so many are back into tubes. I had to endure quite a lot during the days when I tried to talk people into triode amplifiers, or just get them to listen, no one took me for seriously and even the crappiest 60W+ 2N3055 amps where praised to heaven...
Last edited:
Thanks Artosalo, your'e of great help !
Well, the tubes are actualy from an Yaesu FTDX400 transceiver, put in new, but used for only month or two, so I guess they should be in good shape !
I hope I won't destroy them by trying to adjust them for best performance...
@ gorgon53 : I agree with you about that kind of people who "didn't get it", at that time when I was building my firs serious amplifier, about 20 years or so, my choice was mosfet's, and then 6-7 years later came the real deal : TUBES
Although, I didn't build many tube amps, just a preamp and one small SE amp, I helped and was there many times with people who had a bit more "resources", cause in those days, in my country, the situation was a bit....
I don't want to swear....
So, a few moths ago I decided to re-activate my pasion for good amlifiers, and here I am
Cheers Everyone !
Well, the tubes are actualy from an Yaesu FTDX400 transceiver, put in new, but used for only month or two, so I guess they should be in good shape
!I hope I won't destroy them by trying to adjust them for best performance...
@ gorgon53 : I agree with you about that kind of people who "didn't get it", at that time when I was building my firs serious amplifier, about 20 years or so, my choice was mosfet's, and then 6-7 years later came the real deal : TUBES
Although, I didn't build many tube amps, just a preamp and one small SE amp, I helped and was there many times with people who had a bit more "resources", cause in those days, in my country, the situation was a bit....
I don't want to swear....So, a few moths ago I decided to re-activate my pasion for good amlifiers, and here I am
Cheers Everyone !
sadly true....there are however $ tubes like the 13GB5, 6gv5 and many others..
There are two kinds of sweep tubes. The vertical (frame) output tube in a TV set operates as a class A linear amplifier. Think of it as an audio amp that always plays one note, either 50 or 60 Hz. Early TV's used audio output tubes like the 6V6. The 6LU8 is one of these. They typically have high voltage screen grids, and some are specified for triode operation. All are suitable for SE or P-P audio amps.
The horizontal (line) output tube operates as a current limited switch, and was not designed for linear operation, or triode connection. Many of these tubes do work quite well as linear amplifiers and have characteristics suitable for high powered audio amps. Most of these tubes have low screen voltage ratings. Most work quite well for audio P-P amps, but most don't like class A.
I built a push pull 300B amplifier (the 300Beast) about 12 years ago. It had sound qualities and dynamics unlike any SE amp, or any of the typical pentode push pull amps of the day. I attributed these qualities to the low plate resistance and ability to operate without feedback of the 300B triode. I set out to find a way to get more power and avoid the use of expensive tubes. Big triodes are expensive, so I experimented with triode connected pentodes. A triode wired 6L6GC works OK and a triode wired KT88 works better, but neither has the dynamics that the 300Beast amp has. I remembered a guitar amp that I had built nearly 20 years ago that ran a pair of 6LW6 sweep tubes and made over 150 watts. Could a triode wired sweep tube work? Some do, some don't.
The 6AV5 does work well in triode. Most can run at 300 volts, and some will live at 350 volts. In contrast the 6AV5 will live at 650 volts on the plate in pentode mode. A 6AV5 in triode does have dynamics like the 300B. Could a bigger sweep do better?
Some sweep tubes like the 6CD6 will not work at all in triode. Anything over 200 volts leads to runaway. I returned to the biggest tube in my collection, the 6LW6. I bought a bunch of these way back when they were $5 each. Some of them seemed unstable at 350 volts, and some seemed solid at 450 volts. I picked a few that worked at 450 volts and build an amp that ran a pair in each channel and made about 75 watts on 450 volts with a 3300 ohm OPT. It sounded great.....but.....it blew up regularly.
A pentode tube at idle doesn't know if it is triode wired, UL or pentode connected since the plate and screen are idling at the same voltage. The amp would play great for weeks, or months, then without warning, one of the 6LW6's would go into uncontrolled runaway. Fuses and sacrificial 10 ohm cathode resistors kept real bad stuff from happening. Once a tube ran away, it would do it again. I lowered the plate voltage twice and still had a runaway event at 350 volts. Almost always it happened after playing the amp loud for a whole CD, then letting it idle. After blowing 7 tubes, I gave up on that amp, and triode wired sweep tubes in general. I discovered the 3B21WB and the 7403. These tubes live at 550 volts in triode....but they are hard to find.
THe original experimrnts using trioded 6L6GC and KT88 were done with the hardware developed in this thread:
http://www.diyaudio.com/forums/tubes-valves/133034-6l6gc-ab2-amp.html?highlight=6l6gc+ab2
The 6LW6 and 7403 and a few other tubes were also run in that amp. They worked great in that amp and got occasional use for nearly a year. The amp has been mounted on a "universal breadboard" with swappable driver and output boards for several years now in search of audio nirvana. That driver design was fully differential using cascaded LTP's much like the original 300Beast.
I had experimented with Schade style feedback using the techniques outlined in Schade's original 1939 publication on the 6L6GC and other typical audio tubes without finding magic several times over the past 20 years.
Pete Millett unintentionally changed all that. Pete applied Schade in a rather simple way (a single resistor) to sweep tubes in a rather mild mannered 18 WPC amp. I bought a board making the comment that I would be dissapointed with anything less than 50 WPC.
I (and everyone) was surprised to see just how this thing worked. EVERY sweep tube that I tried in it worked, little ones, BIG ones, and everything in between. Dynamics, this thing has it, power...how much do you want????? How about 250 WPC from a single pair of tubes. Even the small sweep tubes like the 6AV5 crank out 75+ WPC.
I published a conservative build at 125 WPC, using $5 tubes and several people built it. Stable?? I have run it at full tilt for hours, and played guitar through it. No runaway, no boom, just LOUD. Yes, I tested 6KD6's they make over 200 WPC. Interested???
Read the very long thread:
http://www.diyaudio.com/forums/tube...-p-power-amp-design.html?highlight=driver+pcb
Pete made a more universal driver board. I did some testing with cheap sweep tubes, extracting 100 to 150 WPC from 13GB5's that are currently under $1 each!
All in this thread:
http://www.diyaudio.com/forums/tube...ush-pull-driver-pcb.html?highlight=driver+pcb
I have a pair of Petes new boards, my original driver boards, several hundred sweep tubes, 2 or 3 power supplies capable of delivering a killowatt, and one of Landfall Systems new cases. I will be building something big (100+ WPC) in the next few months, and I will start a new thread to chronicle the build. After that, I have the parts for a 300 to 500 WPC amp.
Between my work schedule and the chemo, I have not had the time or energy to work on this project much, but that is changing....
Back in the 60's I was interested in electronics. This interest mostly consisted of taking things apart to see what was inside. I was about 10 years old, with ADHD, so putting them back together again was out of the question.
I "made" my first guitar amp by stripping the wires of a guitar cable and twisting them to the phono cartrige leads in an old Magnavox HiFi and a long career of annoying the neighbors with screaming guitars was launched.
There was a ham radio guy in the neighbohood who worked as the engineer at a radio station. He attempted to teach me how tubes and other "stuff" worked, but my impatient brain only gathered what I wanted to hear. He did convey the message that the vertical sweep section of a TV could be easilly modified to make an audio amp. The oscillator stage, became a gain stage by lifting a cap, and the output stage needed no changes. The vertical output transformer was equally at home driving a speaker as it was driving a deflection yoke.
I made several small SE guitar amps this way. The first Bottlehead S.E.X. amps were made the same way. All the vertical output transformers were used up, so the new SEX kits use real OPT's.
Single Ended eXperimenter's Kit
The ham guy later showed me how to use ordinary power transformers for push pull OPT's and introduced me to the horizontal output tube. I now had the capability to make some wickedly loud guitar amps, but not the knowledge to know what I was doing. It would be several years later in high school electronics class, where the mysteries of impedance matching, bias, and load lines were unlocked. I finally understood why the little 6BQ6's were louder than the bigger 6DQ6.
Madman: you didn't say what country you were in, but implied that it wasn't here. If you have a good set of 6KD6's and aren't sure of how to proceed, it might be wise to sell them to someone who will pay what they are worth, then use the cash to buy a dozen cheap tubes to experiment with and have money left over for things like transformers. I have been collecting sweep tubes for 40+ years. I don't keep the expensive ones since the cheap ones usually have the same guts inside. If a sweep tube ever got used in an RF amplifier, the supply dwindled over the years since many of these amps ate tubes. This drove the price up. The tubes that weren't used in RF amps have been sitting all alone on a shelf somewhere waiting for someone to figure out what to put them in. They are still cheap.
I "made" my first guitar amp by stripping the wires of a guitar cable and twisting them to the phono cartrige leads in an old Magnavox HiFi and a long career of annoying the neighbors with screaming guitars was launched.
There was a ham radio guy in the neighbohood who worked as the engineer at a radio station. He attempted to teach me how tubes and other "stuff" worked, but my impatient brain only gathered what I wanted to hear. He did convey the message that the vertical sweep section of a TV could be easilly modified to make an audio amp. The oscillator stage, became a gain stage by lifting a cap, and the output stage needed no changes. The vertical output transformer was equally at home driving a speaker as it was driving a deflection yoke.
I made several small SE guitar amps this way. The first Bottlehead S.E.X. amps were made the same way. All the vertical output transformers were used up, so the new SEX kits use real OPT's.
Single Ended eXperimenter's Kit
The ham guy later showed me how to use ordinary power transformers for push pull OPT's and introduced me to the horizontal output tube. I now had the capability to make some wickedly loud guitar amps, but not the knowledge to know what I was doing. It would be several years later in high school electronics class, where the mysteries of impedance matching, bias, and load lines were unlocked. I finally understood why the little 6BQ6's were louder than the bigger 6DQ6.
Madman: you didn't say what country you were in, but implied that it wasn't here. If you have a good set of 6KD6's and aren't sure of how to proceed, it might be wise to sell them to someone who will pay what they are worth, then use the cash to buy a dozen cheap tubes to experiment with and have money left over for things like transformers. I have been collecting sweep tubes for 40+ years. I don't keep the expensive ones since the cheap ones usually have the same guts inside. If a sweep tube ever got used in an RF amplifier, the supply dwindled over the years since many of these amps ate tubes. This drove the price up. The tubes that weren't used in RF amps have been sitting all alone on a shelf somewhere waiting for someone to figure out what to put them in. They are still cheap.
I had completely forgotten about this thread that involved me about 4 years ago. Suprised that is is still going!
The PL509/519 is very linear as a triode but is suited in this mode to lower voltages such as direct coupled amplifiers.
The KT90 was at EI just PL509 parts with 6v3 heater fitted to Octal base but with a different pitch of screen grid winding to aproximate a 450 volt KT88 type circuit. I was at the factory about 12 years ago before they went awol and sold to Western Electric suposedly. Equipment rotting somewhere in Nis.
The PL509/519 is very linear as a triode but is suited in this mode to lower voltages such as direct coupled amplifiers.
The KT90 was at EI just PL509 parts with 6v3 heater fitted to Octal base but with a different pitch of screen grid winding to aproximate a 450 volt KT88 type circuit. I was at the factory about 12 years ago before they went awol and sold to Western Electric suposedly. Equipment rotting somewhere in Nis.
Tubelab : Similar story for me, born in '76, in the eighties started to get interested in electronics and almost everything with wires in it
The country is Serbia, the northern part called Vojvodina, the most calm region of the country, but the politics, bad economy, blah, blah, blah, long story...
So, the situation has changed a bit, but, for example still no PayPal, so no worldwide parts purchase available, gotta work with what I have here
Oh well, thanks for the good advice, probably will do so, hope to find someone who needs those 6KD6's badly
Also, wish I had someone like you arond when I was younger, like you had that "Ham radio Guy" in those days to show you the right path, he was of big influence I suppose.
Cheers !
The country is Serbia, the northern part called Vojvodina, the most calm region of the country
, but the politics, bad economy, blah, blah, blah, long story... So, the situation has changed a bit, but, for example still no PayPal, so no worldwide parts purchase available, gotta work with what I have here
Oh well, thanks for the good advice, probably will do so, hope to find someone who needs those 6KD6's badly
Also, wish I had someone like you arond when I was younger, like you had that "Ham radio Guy" in those days to show you the right path, he was of big influence I suppose.
Cheers !
Last edited:
some links you may find useful....
http://www.diyaudio.com/forums/tubes-valves/78822-horizontal-tv-tubes-used-amplifier.html
http://www.diyaudio.com/forums/tube...-screen-drive-amp-design-comments-please.html
http://www.diyaudio.com/forums/tube...odes-tetrodes-suitable-screen-grid-drive.html
http://www.diyaudio.com/forums/tubes-valves/60346-vertical-deflection-tubes-audio-output.html
http://www.diyaudio.com/forums/tubes-valves/78822-horizontal-tv-tubes-used-amplifier.html
http://www.diyaudio.com/forums/tube...-screen-drive-amp-design-comments-please.html
http://www.diyaudio.com/forums/tube...odes-tetrodes-suitable-screen-grid-drive.html
http://www.diyaudio.com/forums/tubes-valves/60346-vertical-deflection-tubes-audio-output.html
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.