In Post # 95, the coupling caps were 100nF (0.1uF).
A DC coupled cathode follower driver to the output state control grid . . .
makes it possible to do Class A2 (SE) or Class AB2 (Push Pull) . . . whether or not you want the number 2 behind the Class.
Some outputs run OK with grid current, others not.
A DC coupled cathode follower driver to the output state control grid . . .
makes it possible to do Class A2 (SE) or Class AB2 (Push Pull) . . . whether or not you want the number 2 behind the Class.
Some outputs run OK with grid current, others not.
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painted,
Use a big enough core, and it will not saturate.
Use lots of grid current on an output tube's g1, and it can cook the grid.
Depends on the type of the tube.
Some tubes are specifed to have No g1 current.
Some tubes are specified To Have g1 current.
Some tubes that are specified to have No g1 current, but can have a limited amount.
All tubes can be abused somewhat.
But some can safely be abused more than others.
Your Mileage May Vary.
Use a big enough core, and it will not saturate.
Use lots of grid current on an output tube's g1, and it can cook the grid.
Depends on the type of the tube.
Some tubes are specifed to have No g1 current.
Some tubes are specified To Have g1 current.
Some tubes that are specified to have No g1 current, but can have a limited amount.
All tubes can be abused somewhat.
But some can safely be abused more than others.
Your Mileage May Vary.
For EL34 I would not bother with a cathode follower - there is little benefit going above about +2v on the grids. Driving from 47k plate resistors is just fine - just have say 4k7-10k grid stoppers to help with blocking - anything bigger will effect the HF phase response and make NFB more tricky.
My order from Edcor finally shipped, boy did that take a while. Still, it was just about 6 weeks! Now I just need PSU parts, which I was planning to order from Antek, but the 200VA 350v transformer I was looking at is currently out of stock and won't be back in stock until mid November. Does anyone have a 350V transformer that can do 250ma that they're willing to part with? If not, I guess I can just wait until it's back in stock, but that might be a while.
Thanks!
Thanks!
In my experience (which does not include the Hammond nor the Antek power transformers) it pays off to have a cool running and not too much vibrating transformer. Overspecced is nice for this reason as it helps regulation as well. If I order a custom build 300W unit it costs circa €100 and that is money well spend because altering the chassis afterwards is awkward.
Antek has the 4T360 in stock. $57 is still reasonable for a power trafo.
If the one you wanted would actually be in stock mid November, that’s not a very long wait. But they don’t re-stock very often - I’ve seen some models stay out of stock a long time so it could be longer. Supply chains across the globe have been pretty well disrupted. Try getting speaker drives from COVID hot spots right now - it’s like pulling teeth. Still waiting on all my PRV 12” for my kick bins that I just finished painting. It will be till well into next year. Right now they are trickling in one or two at a time. Antek gets big shipments that they pre-order a few times a year, from what I understand. When I needed some 1.5kVA units a couple years ago they didn’t have them and weren’t getting any soon. But he did offer to pull some out of pre-built power supplies they had in stock and I took him up on it. With the tube trafos, that’s not an option. I’d see what happens on the promise date, or a week or two after, and if they’re still not in stock get the bigger one. It’s only $20 more
If the one you wanted would actually be in stock mid November, that’s not a very long wait. But they don’t re-stock very often - I’ve seen some models stay out of stock a long time so it could be longer. Supply chains across the globe have been pretty well disrupted. Try getting speaker drives from COVID hot spots right now - it’s like pulling teeth. Still waiting on all my PRV 12” for my kick bins that I just finished painting. It will be till well into next year. Right now they are trickling in one or two at a time. Antek gets big shipments that they pre-order a few times a year, from what I understand. When I needed some 1.5kVA units a couple years ago they didn’t have them and weren’t getting any soon. But he did offer to pull some out of pre-built power supplies they had in stock and I took him up on it. With the tube trafos, that’s not an option. I’d see what happens on the promise date, or a week or two after, and if they’re still not in stock get the bigger one. It’s only $20 more
So it looks like they did get the 2T350’s in. I bet you got them quick, didn’t you? I ordered 5 trafos for 3 projects at 7 in the morning last Friday, they shipped by 9, and were here first thing Monday morning.
Are you doing a choke input or can you get away “chokeless” for initial testing (500 volts)?
Are you doing a choke input or can you get away “chokeless” for initial testing (500 volts)?
Cap input, so I can get away without a choke for testing. They were in on the 10th, I had to send him a message to get the website updated. The shipping speed was truly excellent, I had it the day before the USPS estimated delivery date, which was today. Got here in 3 days, no problem.
As far as a choke goes, I think I'm going to get a Hammond one from Mouser as I have to place an order there anyway. That'll get mounted under whatever chassis I make, but for now, I'm testing everything on a board, as I don't want to waste time on something that doesn't work well electronically!
As far as a choke goes, I think I'm going to get a Hammond one from Mouser as I have to place an order there anyway. That'll get mounted under whatever chassis I make, but for now, I'm testing everything on a board, as I don't want to waste time on something that doesn't work well electronically!
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