What would I do if I move to a much larger room and the power of Milq’s full 6C33C would not be enough? Surely it would be possible to go for transmission tubes but they all high plate impedance and high voltage.
If I parallel all my bass drivers and have around 1R load impedance then it will be a transformer with zillion turns… Also, I am not a big fun of the transmission tubes’ bass.

Adding more drivers in bass array look promising but not necessarily effective or practical. So, it would be interesting to find a high current tube that might be sitting in Milq’s bass channel socket. Since I so like the sound of 6C33C it would be worth to mention that the 6C33C has a bigger brother: 12C42C

The 12C42C was a next tube in the succession or 6C19C, 6C41C, 6C18C/6C33C. The 6C41C had one plate the 6C18C/6C33C were two plated and the 12C42C was simialr tube to the 6C33C but with 3 plates!!! It is not enough to be become purring – look at the 6C33C data:

Filaments: 12.6 and 5A
Anode voltage: 120V
Anode Current: 1A
Plate impedance: 65R
Maximum Anode dissipation -120W

Whonna to drive dead woofers with single ended triode? Get the Bell Laboratories 320A tube.

The 320A Vacuum tube was designed for use as an oscillator, modulator, or amplifier at the higher power levels
and high frequencies.

Filament ratings: 35 volts at 435 amperes
Average thermionic emission: 90 amperes
Characteristics at 18 kV plate voltage and 8 amperes plate current:
Amplification factor: 30
Plate resistance: 965 ohms
Transconductance: 31,100 micromhos

Maximum plate voltages: 12.5 kV modulated, 18 kV non modulated, 20 kV RMS AC
current: 15 amps DC
dissipation: 150 kilowatts

Maximum grid dissipation: 2 kilowatt

http://www.goodsoundclub.com/pdf/GU48.pdf

Romy the Cat wrote:

There was a cool Russian-made tube GU-48...  I do not think that it would be worse; in fact I think it might be even better…

Nope, the Russian tubes generally much, in fact much worse than western equivalents. There were however some exceptions. Those options were due to various reasons. The tubes like GM70, YO186, 1P24B, 6E5P, 6N30P, BO188, GM57, UB180, 6C33C, 6N6P, M457, ТО-143, YO104 were very-very good. The GU81, GU48, GU29 were generator tubes and they are presumably OK; I did not hear any good-made amps with it.  The GM70 is transmitting tube as well and it is exceptionably good tube also, way more superior then 211/845 tubes but it is kind of not used yet tube as no one so far made any decently sounding amp with it, at least among those that I heard. So, the Russian transmitting tubes from the GU line might be fine tubes. To make an amp with them is a totally different subject…

What surprises me however is why you have expressed an interest in the high power tubes? You are with horns and even you LF sections have over 100dB sensitivity. What will you do with 120W SET?

Anyhow, I do not have a circuit for this type of amp. The circuit is not a problem, to know how to get sound out of those tubes is the problem and I have no knowledge about it. In the world of transmitting tubes the tube never was a problem. The right output transformer is the problem. It might be VERY expensive to make it properly and it might be very unnecessary due to the existence of DSET concept. Still, to hear a 120W SET over a few days might be a fan experience …

Romy the Cat wrote:

What surprises me however is why you have expressed an interest in the high power tubes? You are with horns and even you LF sections have over 100dB sensitivity. What will you do with 120W SET?

drdna wrote:

The subwoofer still needs a substantial power source. Right now it is being driven by a solid state amplifier.  It would be interesting to see what impact the SET could have here if any.

I see, I did not know that subwoofer needs a substantial power source. If so then sure it might be interesting. To make from GU-48 a powerful LF DSET would not be difficult.  The output transformer will be very simple as well. The high voltage transformer for transmission tubes usually screen up HF as they need excessive high voltage isolation but for LF only DSET it would be no brainer. Make 500mA transformer with larger lamination you will be able to found and coils with 3000V-4000V isolation. I think if you find somebody why would  make it large enough to get 5Hz-7Hz at FULL POWER then it will be around 500-700 transformer. Everything else will be relatively easy if you can talk like this about an amp hat will have 1.5kV on plate. BTW, the GU-48 has high gain, so who know it might be even a single stage amp…

I keep thinking about power and how much extra power and gain I would need in a new room, Sure, it is not difficult to raise a white flag and do for SS amplification but I so would like to stay with SET amplification for my bass channels! I am looking at the Milq bass channel and breaking my head thinking how I can get more power and gain. I do not have the exact numbers how much in shortage I will be but my current that my current Milq will not be able to handle nether power nor gain. In my current room I have a perfect match between room volume, sq of transducer and amplification:

http://www.goodsoundclub.com/Forums/ShowPost.aspx?postID=6057#6057

I have a feeling that if I have extra 6dB of gain and 4 times more power then I might be able to deal with new room. Sure, the only measurement in location would show. What I know is that I VERY much willing to preserve my SET bass but to get more POWER!

Maybe use +/- same design (with boosted/own PS, if necessary), but fuse the 6C33C plates together for 3 dB, or double-double for 6 dB.  Might be closest thing to a known quantity.

Best regards,
Paul S

Romy the Cat wrote:

I have a feeling that if I have extra 6dB of gain and 4 times more power then I might be able to deal with new room. Sure, the only measurement in location would show. What I know is that I VERY much willing to preserve my SET bass but to get more POWER!

cv wrote:

Consider a triode connected 13E1. 95W dissipation, will probably work beautifully with the existing OPT if you adjust the gap down and if you can rewire your arrays to present a somewhat higher impedance. Something like 400V-450V / 200mA-ish will give you a plate impedance of about 300 ohms, and it probably wants to see a load of around 1k5.

There is a tube out there might be a good candidate to drive ULF from DSET

http://tubedata.tubes.se/sheets/127/7/7242.pdf

It is a low voltage triode with 100W on plate, 9 times gain and 80R plate impedance.  3 of them might form a very nice near 100W ULF DSET and it will not be too hard to make it.  Did anybody have seen/heard the SETs built around 7242? With total sun 30R on plate the ultra-high current DSET OPT will  have just a few turns and it might be very interesting…