Yes, that has been used. I'm liking ECC40 and similar tubes - I have one or two of them. 10K Rp. I'm using 2 of 156C in series at the moment and the combination is sounding nice to my ears. I have E180CC as well, bit less Rp at 7.2K.
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Do you perhaps have a CT secondary? If so you can use say a 6x4 on the two outer windings + hybrid graetz bridge for a high voltage section.
Interesting idea. Most of my PSUs are without any CT however, so I use a Graetz bridge.
Can you solve the question of how to connect 2 of 156C in a humbucking way, Bas, using the diagram in post #17?
I'm wondering if it's C. The North-South windings on the guitar pickups are a bit confusing....
Sorry, I did really stretch the point . . . 1200V B+, plate load resistor, and 6SN7, all that just to drive a 300B.
But, I have seen stranger things in Tubes / Valves threads. And there are lots of builders who make 1200V B+,
they never thought of doing that just to power a driver for a low power triode like a 300B.
But as someone already posted in this thread:
Use a lower rp plate resistance triode, so that you can use a lower resistance RL plate load resistor.
Or, use a voltage-doubler to get twice the B+ to power the driver tube; and a non-voltage-doubler to power the 300B.
The doubler putting out perhaps 600V is only 1/2 the difficulty of a 1200V B+.
Creative power supplies are in several threads of Valves / Tubes for 1X and 2X from the same secondary winding.
(or am I wrong?)
But, I have seen stranger things in Tubes / Valves threads. And there are lots of builders who make 1200V B+,
they never thought of doing that just to power a driver for a low power triode like a 300B.
But as someone already posted in this thread:
Use a lower rp plate resistance triode, so that you can use a lower resistance RL plate load resistor.
Or, use a voltage-doubler to get twice the B+ to power the driver tube; and a non-voltage-doubler to power the 300B.
The doubler putting out perhaps 600V is only 1/2 the difficulty of a 1200V B+.
Creative power supplies are in several threads of Valves / Tubes for 1X and 2X from the same secondary winding.
(or am I wrong?)
Andy
Maybe this link answer your question about how to Connect the two chokes…
https://intactaudio.com/fil.html
Maybe this link answer your question about how to Connect the two chokes…
https://intactaudio.com/fil.html
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Joined 2009
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I've used a Hammond power supply filter choke for a plate load on a 6SN7 front end and it works very well - it's the only option when you don't have the headroom in your B+ to give the tube the plate voltage you want. This is why I used it and I was not disappointed by the sound quality. However, in a smallish chassis the plate choke picked up HUMMMMMM, mostly from the power supply which I never quite tamed to my satisfaction. So if you are going to use a plate choke my advice is don't finalize the layout of the amplifier until you have first built a prototype/breadboard version where you can move parts around until you get it silent. Then cut the holes.
I've not tried active loads yet but when I do it's likely I'll first look at Wavebourne's Tower III amplifier - assuming I ever find a copy of the design because the attachments in his posts from that era have evaporated.
I've not tried active loads yet but when I do it's likely I'll first look at Wavebourne's Tower III amplifier - assuming I ever find a copy of the design because the attachments in his posts from that era have evaporated.
Using devices in series is certainly interesting. For instance a CCS on top and a choke on the bottom, with less inductance necessary than just a choke.
Or a resistor plus a choke in series. I assume once again the choke goes on the bottom?
Or a resistor plus a choke in series. I assume once again the choke goes on the bottom?
Have not posted for some time but I believe the hybrid CCS top with a bottom choke is very worth fleshing out. A choke behaves like a CCS by resisting the change in current so it is intuitive.
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It's a forbidden network because of the voltage at the node where the current sources are connected to each other; if they have exactly the same value, any voltage will do, if they have different values, there is no solution for the node voltage. That is, there is either an uncountable infinity of solutions or none at all.
That only applies to ideal current sources, though. If one is a current source circuit with a finite output impedance and the other is a choke, it could very well work. One may have to be a bit careful with series resonances, if the current source circuit's output impedance is capacitive.
That only applies to ideal current sources, though. If one is a current source circuit with a finite output impedance and the other is a choke, it could very well work. One may have to be a bit careful with series resonances, if the current source circuit's output impedance is capacitive.
2 chokes in series behave as 1 larger choke. Same with capacitors, resistors etc. Combining an active and passive current source should give a hybrid or greatly expand the chokes performance.
As a big fan of DHT triodes I have to say, give the C3g a chance. I just built a spud C3g triode hp amp, 15mA 2.5V bias with three SiC diodes, parafeed load.
The same observations from the big PX4, VT52 tube amps applied here, it's all in the PSU quality and proper loading with iron, 100H Sowter choke and film caps. Generic commercial DHT amps don't sound as involving and detailed. Also I think C3g has low miller in triode compared to true ECC triodes.
ECC40 is a great alternative, one of the best IDHTs but I've broken about 5 so far, glass is fragile and even moderate rolling will cause a crack and loss of vacuum.
If you can live with a lower mu, VR102(BL63) pops up in the UK from time to time, check the MH4 valve for curves. http://www.r-type.org/exhib/aaa0300.htm
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Don't know VR102 and the mu is too low, but I do have some MH4 and that's a good choice. I also have a pair of C3g which I haven't used yet.
But I'm interested in the CCS and choke idea - must try that. There's even a SRPP version with a choke between top and bottom valves.
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Do you have a link to the SRRP w choke. It sounds like it validates the idea. I had thought of this a long time ago but never implemented it. Could be a way to use a simple CCS and less expensive choke to tremendous benefit. Really interested in fleshing this one out.
I don't chase these sort of solutions anymore. The first comment I have is that 10K plate resistance and 15 mA plate current represent an unusual combination in the first place. In general, after trying this and that, I now only use resistive load or a high quality transformer (only where it really gives an advantage). A well sorted 3-stage amp is easily better than an "extreme" 2-stage solution. For example you can DC-couple a highish gain input stage that works around 90-120V (plenty of good choices here) with a low gain DHT or similar. If high gain + high voltage drive (otherwise 15 mA seem more like overkill) is needed it is likely that the output tube will work at rather high voltage (with the exception of regulator triodes), so the overall supply is not an additional requirement.