I've recently completed my first valve amp build and now would like to add an UL/Triode switch. Kindly take a look at my attached drawing and also the original schematic and tell me if the way I drew it is correct.
Orange - Blue, anode to screen via 10 ohm stopper for triode?, and
Orange - Blue/Yellow, Ultra linear tap to screen via 10 ohm stopper is that it ? Also I believe it is not wise to switch when powered up. So only change switch positions when not powered.
Possibly a few more labels on the objects would help people identify transformer, HT supply and junction board, etc.
Orange - Blue/Yellow, Ultra linear tap to screen via 10 ohm stopper is that it ? Also I believe it is not wise to switch when powered up. So only change switch positions when not powered.
Possibly a few more labels on the objects would help people identify transformer, HT supply and junction board, etc.
Oh yes. You've got the UL tap from the OT to one side of the switch and a wire from the plate to the other side. A good quality DPDT switch - it doesn't have to be rated for the full voltage because it won't be switching that voltage, just carrying it, but don't cheap out. And the 100 ohm resistor soldered to the g2 pin to protect the OT in case the tube shorts out.
I built a EL84 SE amp with this switch, works nice. I put the switch very close to the tubes, to keep those HV wires short. It also discourages an inept used from using the switch as it's surrounded by hot tubes 😸
I built a EL84 SE amp with this switch, works nice. I put the switch very close to the tubes, to keep those HV wires short. It also discourages an inept used from using the switch as it's surrounded by hot tubes 😸
When i built my vta-70 i ignored the switch. It is built UL and will remain that. The day i want a triode amp i will get one.
Eh, if he wants an amp with switches, build it! I like mine in UL, but switch to triode every now n then. Fun to play with different speakers, too.
Any time.
You can see the switch in my build, just above the 2 large orange drop caps. White/Blue wires coming from the OTs to the left side of the switch, also from the switch to Pin 9 on each power tube. Not so easy to see the wires from the plates to the switch, you can see the long yellow wire coming from the left socket.
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You can see the switch in my build, just above the 2 large orange drop caps. White/Blue wires coming from the OTs to the left side of the switch, also from the switch to Pin 9 on each power tube. Not so easy to see the wires from the plates to the switch, you can see the long yellow wire coming from the left socket.
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I would also add another DPDT switch to allow you to remove (center off) and also change the Schade feed back resistor (plate to plate) value when it's in triode mode, try 300-470K in triode mode. It will sound really flat in triode mode with a 180K. Honestly 180K sounds pretty low value even for UL. Note changing that resistor value does change the tone of the amp, lowering it tones down the high frequencies, raising the value makes the amp sound more bright/ lively.
Thank you so much, I've tried it out and it works...much appreciated.