i was just bout to start a thread on the topic!
i was thinking of a pair of 6l6 in screen drive because they are so much cheaper. what do you thing? are the 6l6s any use in screen drive. are their screens linear enough? roughly, what kind of transconductance do the screens have?
thanks!
i was thinking of a pair of 6l6 in screen drive because they are so much cheaper. what do you thing? are the 6l6s any use in screen drive. are their screens linear enough? roughly, what kind of transconductance do the screens have?
thanks!
I have no idea about the suitability of a 6L6 for screen drive, but you could be asking in the right place. You might still want to start that new thread anyway so you can get better visibility for the question. I'm using the 509s because I was able to get 8 of them for a good price from an Ebay seller in Lithuania, and they have been characterized for screen drive..
The 6L6 is not a good choice for this service. Take a look at the plate current/voltage curves at Vg1 = 0 and varying Vg2. Notice the required voltages for even modest currents? The tubes that work for this are high perveance sweep tubes. Their characteristics in this connection look uncannily like those of zero-bias triodes.
Wrenchone, that low load can get you some impressive peak power (not sustained without melting the tubes), but it takes some hefty drive. Figure 200V peak (400V p-p) if you can manage a 700V B+.
Wrenchone, that low load can get you some impressive peak power (not sustained without melting the tubes), but it takes some hefty drive. Figure 200V peak (400V p-p) if you can manage a 700V B+.
oh okay. thanks! i will carry on looking!
any other tubes you can recommend other than the 509/519?
any other tubes you can recommend other than the 509/519?
horizontal sweep tubes
there are lots of them you can use, compactrons like the 6LQ6/6JE6, 6KD6,6LF6 etc.
look here for more info:http://www.davidberning.com/ea-2101.htm
there are lots of them you can use, compactrons like the 6LQ6/6JE6, 6KD6,6LF6 etc.
look here for more info:http://www.davidberning.com/ea-2101.htm
i dont suppose any of them current production valves huh... i was looking at the 6lf6 and its a 12pin base, where would i go looking for these valves and bases?
i suspect there are still some of those at SIM LIM Tower.
novar 9pins and 12pin compactron tube sockets are still being made, many are made in china, perhaps it is earier to bring in from singapore. i am trying to look for vendors from honkong, could be a lot cheaper to buy there from the states.
fyi, i worked in singapore from 1997 to 2001 at the jurong isalnds.
novar 9pins and 12pin compactron tube sockets are still being made, many are made in china, perhaps it is earier to bring in from singapore. i am trying to look for vendors from honkong, could be a lot cheaper to buy there from the states.
fyi, i worked in singapore from 1997 to 2001 at the jurong isalnds.
oh thats cool! i have not been able to source the 11 and 12pin sockets here in singapore and they seem terribly expensive from overseas.
i did a ebay on the 6lf6 and they dont look abundant nor cheap. guess i'll have to keep looking....
i did a ebay on the 6lf6 and they dont look abundant nor cheap. guess i'll have to keep looking....
Hey, Hacknet, I had a "d'oh!" moment. 6L6 is lousy for screen drive, but as long as you're thinking high power drivers, it's a perfect candidate for AB2.
hey hacknet,
perhaps you can come to manila if you don't find sweep tubes there. very cheap here, cost of tubes offset the plane fares.
perhaps you can come to manila if you don't find sweep tubes there. very cheap here, cost of tubes offset the plane fares.
SY,
looks like i have found operating points for my 6CM7 drive circuit as follows:
1.input LTP(unit1) at B+ of 300volts, plate at 100volts, 4mA and 50K plate load dc coupled to next stage.
2. 2nd stage LTP, at B+ of 600v, plate at 220volts, 7mA and 40K plate load.
will be using CCS for both LTP's and IRF820 mosfet followers, and the psu will consist of 2 fwb bridges with one stacked on top of the other, this will give me 600 and 300 volts supplies.
with a mu in half for the ist ltp at 11 and 20 for the next, open loop is about 220, now for for a peak drive of 150 volts pk to the screen of the output tube , input is 0.68 volts pk.
i expect to get around 60 watts output from my 4.2K ouput transformer. so that will be 22volts rms at 8 ohms. now if i want an input sensitivity of say 1volt rms, then i need a closed loop gain of 22.
is there anything i missed? your thoughts please.
thanks
looks like i have found operating points for my 6CM7 drive circuit as follows:
1.input LTP(unit1) at B+ of 300volts, plate at 100volts, 4mA and 50K plate load dc coupled to next stage.
2. 2nd stage LTP, at B+ of 600v, plate at 220volts, 7mA and 40K plate load.
will be using CCS for both LTP's and IRF820 mosfet followers, and the psu will consist of 2 fwb bridges with one stacked on top of the other, this will give me 600 and 300 volts supplies.
with a mu in half for the ist ltp at 11 and 20 for the next, open loop is about 220, now for for a peak drive of 150 volts pk to the screen of the output tube , input is 0.68 volts pk.
i expect to get around 60 watts output from my 4.2K ouput transformer. so that will be 22volts rms at 8 ohms. now if i want an input sensitivity of say 1volt rms, then i need a closed loop gain of 22.
is there anything i missed? your thoughts please.
thanks
Interesting... I just gave up on my El509-II PP. The idea was to put a pair of 2K5 torrodial OPT in use and I tried it with the 509s in enhanced triode mode. Used an Lundahl interstage (LL1671) driven by a 6BX7 PP to drive the G2s of the 509s. B+ was 500V... The driver itself worked ok 🙂 - but I was unable to balance the PP 509 stage 
. I had the tubes burn in for hours, balanced the idle current, applied signal to the stage, measured at idle again - out of balance. I am talking 5-10mA here, deadly for the torrodial OPT. I tried G1 and G2 stabilized then, but that did not help either. Finally, tried to constant current the output tubes and ok, achieved balance that way, but had some sort of a compression effect at large signals, that didn´t make me too happy. End of the story: currently putting the OPT in use with good 'ol 6CA7s (4x) with great results and have the 509-IIs waiting for a nice G2 driven SE try...
Here's what I measured from the 509-PP (constant current source, no nfb), before I finally gave up:
Poutmax ~ 30W
1W out, THD:
100Hz 1,4%
1kHz 1,3%
10kHz 1,2%
20kHz 1%
20W out, THD:
100Hz 2,9%
1kHz 2,5%
10kHz 2,3%
20kHz 1,8%
Is that just the 509-IIs or did you have similar problems? Anyway, still like these little bottles and will find them a place in an amp some time (and no, not as a pass regulator
)
Marcus
. I had the tubes burn in for hours, balanced the idle current, applied signal to the stage, measured at idle again - out of balance. I am talking 5-10mA here, deadly for the torrodial OPT. I tried G1 and G2 stabilized then, but that did not help either. Finally, tried to constant current the output tubes and ok, achieved balance that way, but had some sort of a compression effect at large signals, that didn´t make me too happy. End of the story: currently putting the OPT in use with good 'ol 6CA7s (4x) with great results and have the 509-IIs waiting for a nice G2 driven SE try...Here's what I measured from the 509-PP (constant current source, no nfb), before I finally gave up:
Poutmax ~ 30W
1W out, THD:
100Hz 1,4%
1kHz 1,3%
10kHz 1,2%
20kHz 1%
20W out, THD:
100Hz 2,9%
1kHz 2,5%
10kHz 2,3%
20kHz 1,8%
Is that just the 509-IIs or did you have similar problems? Anyway, still like these little bottles and will find them a place in an amp some time (and no, not as a pass regulator
)Marcus
If those indeed are run as screen drive, try something radical- reduce the idle current. A lot. No, I mean a LOT. Try 3-5mA.
SY said:
class AB2 push pull..? whats the magic with push pull..? i'm running a pair of full rangers and i dont exactly need the power, what would you recommend?
Oh, well, why would you want to do screen drive then? The big advantage there is power and efficiency. If you don't need any real power, a pair of EL84s run very conventionally will give 6-8 clean watts in class A. Leave the sweep tubes for those of us whose speakers like to see a lot of volts sloshing around.
The 6LF6 came with an octal base, it is called the 6LW6. There was an article in Glass Audio magazine about 6 years ago that demonstrated a 90 watt per channel amp with 'LW6's.
http://www.audioxpress.com/reviews/media/GA399MA.pdf
Before that article ran you could buy these tubes for under $10 each. Now they are getting scarce. They exist in 26 and 36 volt versions that are often a lot cheaper.
The 'LW6 is my favorite sweep tube. I have achieved 140 watts RMS from 2 tubes in P-P. I haven't found the limits for triode wired SE yet but it is past 15 watts. This was drive and power supply limited. Triode wiring limits the supply voltage to the max screen rating, but these ratings are conservative. Pentode wiring with G1 or G2 drive could produce even more power. See the following thread for some of the tests (triode mode).
http://www.diyaudio.com/forums/showthread.php?s=&threadid=37403&highlight=
I grabbed a screenshot of the EL509 enhanced triode curves from the Svetlana data sheet and set out to do some load line plotting assuming an 8 ohm load, using a starting point of 800V, 10W plate dissipation. I ran plots using the turns ratio data for the Hammond 1650T (120W rating, 950 ohm for 1/2 primary) and the Hammond 1650R (100W rating, 2500 ohm for 1/2 Primary), and plotted points for 30W, 50W, and 70W peak power into 8 ohms. The results show that the 1650R comes fairly close to pushing the tube into non-linear operation for 70W peak (still some margin, though). The peak current is very solidly inside the tube ratings at 70W peak (~200ma) It takes about 60V of swing to get from quiescent operation to 70W peak.
It takes 70V of swing to manage 70W peak power using the 1650T, and the peak current for 70W is almost 400ma.
Both of these transformers could work for me with some caveats. 70W peak is not a bad haul at all from a couple of triodes. However, I'd probably be better off with a primary impedace somewhere between the two extremes. The Hammond 1650N is a small compromise at 2150 ohms per 1/2 primary. It's a smaller (60W)transformer, but that doesn't bother me all that much. I'm not really interested in pumping out huge gobs of RMS power, as I have fairly sensitive speakers. Clean peak power capability interests me more.
Does anyone kow of a readily available output transformer with 60-100W capability and a total primary impedance of about 3k?
It takes 70V of swing to manage 70W peak power using the 1650T, and the peak current for 70W is almost 400ma.
Both of these transformers could work for me with some caveats. 70W peak is not a bad haul at all from a couple of triodes. However, I'd probably be better off with a primary impedace somewhere between the two extremes. The Hammond 1650N is a small compromise at 2150 ohms per 1/2 primary. It's a smaller (60W)transformer, but that doesn't bother me all that much. I'm not really interested in pumping out huge gobs of RMS power, as I have fairly sensitive speakers. Clean peak power capability interests me more.
Does anyone kow of a readily available output transformer with 60-100W capability and a total primary impedance of about 3k?
SY said:
i was thinking of something sexy, deveating from the norm.. would el84s in a2 make any sense?
hacknet said:
Hi hacknet,
we've tried SE A2 for EL84. No-No. It didn't work, you'll have to push massive currents in the grid (we measured up to 20mA at +5Vgk) and you gain only a watt or so. After that, 2 of our 4 tubes died
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