On that load line, for what ever its g2 voltage is( 5 or 600V IIRC ), it should be reduced so the g1=0V line happens at that current delivery. I don't quite see this GU46 running U-L. Local FB pentode will deliver the required output impedance...which is a fine quantity to reduce...
cheers,
Douglas
In which way you want to apply that Local FB pentode ?
Eg2 was 600V in the Ep-Ip chart (post 21). Below is the Ep-Ip characteristic with Eg2=450V. The operating conditions are Ea0=1000V, Eg1=-34V, and Ra-a=5k. The Spice model isn't that accurate, so please ignore the saturation region, instead use the diode line shown in green to get the estimates for Ia_max and Ea_min, in this case, they are 720mA and 200V respectively, so Po is still around 280W as calculated before.On that load line, for what ever its g2 voltage is( 5 or 600V IIRC ), it should be reduced so the g1=0V line happens at that current delivery. I don't quite see this GU46 running U-L. Local FB pentode will deliver the required output impedance...which is a fine quantity to reduce...
cheers,
Douglas
I still have GU81m, and sockets. Same thing happened to me. Try a scaled down version maybe?
cheers,
Douglas
No to forget cooling for the nearly 1kW of heat produced.And 2x 16A heater with a current limit of 23A at the start.
Mona
err...4X 16A heater...LOL unless we're talking about a single monoblock. The GU81m was a slightly tamer 12V at 12A, give or take.
It all comes down to the OPT...and IMO a proper one is too big to behave itself.
cheers,
Douglas
E-Linear. 10 or 20% of it. With an EL34 LTP input stage. EL34's g2 around 100V. A pair of 6L6GC with their g2 around 175V will also do, but it will be lower gain than the EL34.
cheers,
Douglas
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Yup, this is one expensive space heater.
On a more serious note, below is the Ep-Ip characteristic with an even lower Eg2 of 300V. The operating conditions are: Ep0=1000V, Eg1=-20V, Ra-a=10k, with a Po of "just" 170W.
I can't help myself... I do not want these tubes to rot in the cellar.
What about SE usage? Like ClassZ or the Russian model GU-46 zugunder...
?????? ????????? ?? ??-46 "Zugunder" but this guy used 3kV (?) In the anode, driver seems to be 6SN7 followed by 6SJ7.
Thomas
What about SE usage? Like ClassZ or the Russian model GU-46 zugunder...
?????? ????????? ?? ??-46 "Zugunder" but this guy used 3kV (?) In the anode, driver seems to be 6SN7 followed by 6SJ7.
Thomas
Yup, this is one expensive space heater.
On a more serious note, below is the Ep-Ip characteristic with an even lower Eg2 of 300V. The operating conditions are: Ep0=1000V, Eg1=-20V, Ra-a=10k, with a Po of "just" 170W.
View attachment 651264
If you bump the load 2x, you notice it can swing a lot higher delta towards cut off than towards saturation. If you must run a 10k a-a, might as well bump B+ to 1k5V...
Then the 300mA idle current will net higher anode dissipation.A good 10k a-a is difficult around 60W...not much chance of success going bigger.
cheers,
Douglas
Interesting, the SE project does not seem to draw as much attention as a high power output push pull approach does.
This would be my first SE project, so I would stick to ClassZ's approach, as proposed by Jazbo.
Such a SE OPT will also be a challenge, will it? Any important points to consider / take in account when going for such a big SE OPT?
Thomas
This would be my first SE project, so I would stick to ClassZ's approach, as proposed by Jazbo.
Such a SE OPT will also be a challenge, will it? Any important points to consider / take in account when going for such a big SE OPT?
Thomas
The OPT is going to be a problem since the output power is quite high (by SE standard), ClassZ's design used a Hammond 5k but it was just for 30W, not sure you would want to repeat that given all the effort and costs put into the project. Although his driver circuit could be adapted for your needs.
Well, I am currently trying to find some transformer builders to find out where they see their limitations for OPTs.
I think it could be an alternative to use two paralleled OPTs instead of one, wouldn't it?
This would half the required wattage and ampere they need to handle, probably optimize mids and highs, and be 10k in instead of 5k?
Does this work for pp and se?
Lets forget about weight at the moment...
I think it could be an alternative to use two paralleled OPTs instead of one, wouldn't it?
This would half the required wattage and ampere they need to handle, probably optimize mids and highs, and be 10k in instead of 5k?
Does this work for pp and se?
Lets forget about weight at the moment...
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Yes, paralleling OPT’s is a viable option, but you do not need to double the primary impedance, since putting two OPT’s in parallel does not change the turns ratio. For off-the-shelf OPT, the Hammond 1642SE may work, it can handle 300mA, and has 4-8-16 taps, so you can get the load matching required. In the above example, you can put the 8R speaker on the 16R tap to get a primary impedance of 2.5k, which is close enough.
866A can handle average 0.5A /2A peack @2KVolts
lower voltage more current available
for no noise HV you need 2.5VCT transformer
Triad F-3X for two 866A, 2.5VCT 10A
110V transformers, so two in series in Europe for 4 tubes 866A
F-3X Triad Magnetics | Mouser France
lower voltage more current available
for no noise HV you need 2.5VCT transformer
Triad F-3X for two 866A, 2.5VCT 10A
110V transformers, so two in series in Europe for 4 tubes 866A
F-3X Triad Magnetics | Mouser France
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I got the first offer for SE OPTs
- 2.5k primary, 4 + 8R secondary, 170W, 1200V at 600mA, Ei 150/92 core, 14kg each, approx. 360Euros pp
- 5k primary, 2 + 4R secondary, 80W, 1200V at 300mA, Ei 120/73 core, 7kg each, approx. 180Euros, to be used in parallel
Custom wound, an additional winder did not yet call back.
- 2.5k primary, 4 + 8R secondary, 170W, 1200V at 600mA, Ei 150/92 core, 14kg each, approx. 360Euros pp
- 5k primary, 2 + 4R secondary, 80W, 1200V at 300mA, Ei 120/73 core, 7kg each, approx. 180Euros, to be used in parallel
Custom wound, an additional winder did not yet call back.