If you have E130Ls for sale you can always drop me a PM, I'd love to try a pair instead of the EL36 I'm using as drivers now.
90´mA/V, grid stoppers not optional 😱
EL 3010 is easiest to use as anodefollower, just as the E130L, but E130L is a bit easier to tame
I know those where the last tube type developed by telefunken, but i thinck that in 1967, when i first got to know about that tube, semis would not yet have been up to this job. But i do not really know for sure, later on yes, there is even a semiconductor based replacement, the EL3010-E if i remember correctly.
Now Im curious!
Andy, have you tried EL36?
I think we have discussed that tube before. Very nice triodes, 3,5k should be a good plate load if you run them at a moderate plate voltage but a high-ish plate current. Say 230-240V and 60-70mA or so. Cheap as dirt if you go for the P-version and use a 24V transformer for the heaters.
Errh! This is the Williamson (actually with KT66s) so one of the classic 'pentodes as triodes'. I have my reservations on the Williamson but who am I to disagree wid da Golden Pinnae 😊
I do not know anything about those, other than some of them where, some years ago, up for sale on ebay.
I've been trying to find the Rp in triode for KT61. Anyone know? There are curves on Frank but I've forgotten how to extrapolate the Rp from the curves.
Correct, ..........I´m currently using 12GN7 with CCS in cathode as push pull diff drivers in triode mode with 25dB gain but they can react bit flighty when near grid cutoff approaches. The balance is near perfect. An obvious way to soften them up is to included unbypassed cathode resistors, allowing degenerative feedback,which unfortunately increases anode impedance. Can´t win ......but is an indication to do the circuit work carefully and use lowish value grid stoppers 1Kohm, as input capacitance is on the high side. The sister tube 12BY7 with slighty lower gm # transconductance is easier to work with but both have bandwidths that can operate well into the RF domain. These video tubes have larger area cathode than others and can be pushed quite hard up the curves but they are robust.
Design carefully.
Bench Baron
Hi Andy,
Have you looked at RS1003 (SRS551) tubes as an option? May match well with 3k impedance txr. Ale moglia had put up the characteristics on his website.
Similar to F2a, as being long lasting ( 10,000 hrs) . More available if you do search on people who have used this tube
Have you looked at RS1003 (SRS551) tubes as an option? May match well with 3k impedance txr. Ale moglia had put up the characteristics on his website.
Similar to F2a, as being long lasting ( 10,000 hrs) . More available if you do search on people who have used this tube
Attachments
I found spreadspectrum's post that contains superimposed curves for 300B, KT88 in triode and KT88 with plate to grid feedback. The plate to grid feedback curves best the linearity of the 300B.
Steve
Steve
Ah yes. The poorly named and often maligned "anode follower" (or "plate follower").
I was thinking of making a line stage using a 6SN7 with plate-grid feedback to reduce its gain to about 2X and its Zout to less than 1k ohms. Why not do that with an output stage, right?
Does anyone remember Michael Koster's 'Schadeode', with a depletion mode MOSFET as the input stage, DC coupled to a 6L6GC output, with a 100k feedback resistor acting as the drain load resistor for the MOSFET, completing the plate-grid feedback around the 6L6? I threw it into LTspice and it performs pretty spectacularly. This is the first drawing, I think. It was refined later, but I can't find the later posts...
I was thinking of making a line stage using a 6SN7 with plate-grid feedback to reduce its gain to about 2X and its Zout to less than 1k ohms. Why not do that with an output stage, right?
Does anyone remember Michael Koster's 'Schadeode', with a depletion mode MOSFET as the input stage, DC coupled to a 6L6GC output, with a 100k feedback resistor acting as the drain load resistor for the MOSFET, completing the plate-grid feedback around the 6L6? I threw it into LTspice and it performs pretty spectacularly. This is the first drawing, I think. It was refined later, but I can't find the later posts...
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I am not sure why the link I posted takes you to the 14th post. That is not what I intended to show.
The first post in the thread by SpreadSpectrum has links to the schematic and curves.
Steve
The first post in the thread by SpreadSpectrum has links to the schematic and curves.
Steve
For comparison, here's the SpreadSpectrum circuit. It's the same idea as Michael Koster's but more refined. The source follower is a nice touch, imo, as is the use of the +/-400V DC power supply. Slick!
My next project will be a version of this using russian GU-32 tetrodes and cheap Edcor transformers. If it turns out well I might try the same circuit with big high mu triodes later on.
