I would parallel 5 of them if I used them. I even have to parallel 2 in my speaker crossover for power handling. But thanks for the warning
Andy,
I showed my circuit to Rod Coleman and he felt the 15V tx would be OK. I had already bought the regs, and I might say he sent them before the money reached him! I used the wrong email address, but it's all sorted now.
The preamp I heard had the glow tubes removed, and sounded good to me, so I will stick with that. I need to walk before I run, so I'm not going to deviate from what (little) I know.
For hardwiring I plan to use turret tags, I just need to find some plain board, preferably PTFE, or failing that FR4.
And I've ordered the cheap AZ1 from a Bulgarian seller to start me off, but a meshplate is what I will want when it's working. And a couple of globe 26s. Plus the UX4 sockets will be paralleled to try 80s.
The PSU will be in separate box, matching the preamp box; Rui Lourenco's and Thomas Mayer's designs are what I am looking at, but my wife thinks they are bit a square looking, so I am showing her lots of shapes to find out what she likes. I did this with the speakers, and she chose the veneer and the black leather fronts. Even the grills are her choice. This way I get away with more.
Oh, and things like using the cap size before the choke to drop the voltage is one of the many new things I am learning here. Thanks for that.
I showed my circuit to Rod Coleman and he felt the 15V tx would be OK. I had already bought the regs, and I might say he sent them before the money reached him! I used the wrong email address, but it's all sorted now.
The preamp I heard had the glow tubes removed, and sounded good to me, so I will stick with that. I need to walk before I run, so I'm not going to deviate from what (little) I know.
For hardwiring I plan to use turret tags, I just need to find some plain board, preferably PTFE, or failing that FR4.
And I've ordered the cheap AZ1 from a Bulgarian seller to start me off, but a meshplate is what I will want when it's working. And a couple of globe 26s. Plus the UX4 sockets will be paralleled to try 80s.
The PSU will be in separate box, matching the preamp box; Rui Lourenco's and Thomas Mayer's designs are what I am looking at, but my wife thinks they are bit a square looking, so I am showing her lots of shapes to find out what she likes. I did this with the speakers, and she chose the veneer and the black leather fronts. Even the grills are her choice. This way I get away with more.
Oh, and things like using the cap size before the choke to drop the voltage is one of the many new things I am learning here. Thanks for that.
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Andy,
I showed my circuit to Rod Coleman and he felt the 15V tx would be OK. I had already bought the regs, and I might say he sent them before the money reached him! I used the wrong email address, but it's all sorted now.
The preamp I heard had the glow tubes removed, and sounded good to me, so I will stick with that. I need to walk before I run, so I'm not going to deviate from what (little) I know.
For hardwiring I plan to use turret tags, I just need to find some plain board, preferably PTFE, or failing that FR4.
And I've ordered the cheap AZ1 from a Bulgarian seller to start me off, but a meshplate is what I will want when it's working. And a couple of globe 26s. Plus the UX4 sockets will be paralleled to try 80s.
The PSU will be in separate box, matching the preamp box; Rui Lourenco's and Thomas Mayer's designs are what I am looking at, but my wife thinks they are bit a square looking, so I am showing her lots of shapes to find out what she likes. I did this with the speakers, and she chose the veneer and the black leather fronts. Even the grills are her choice. This way I get away with more.
Oh, and things like using the cap size before the choke to drop the voltage is one of the many new things I am learning here. Thanks for that.
Rod puts his faith in his ingenious designs, Thomas Mayer is a fan of chokes in his filament supplies. I'm in between the two. I do hear a difference with choke input - it's slightly smoother. You'll get a quasi-choke input effect with a small input cap and you can vary that to tune the output voltage.
You will be wasting the AZ1 mesh if you use electrolytic PSU caps. You need to use all polypropylene PSU caps. I've been through all these kind of permutations, and I'm pretty definite on that one.
Looks like it's coming together!
The only place I would use 'lytics is in the filament supply, to get the big values. I wouldn't even consider them in the HT supply. I don't even use them in speaker crossovers, unless I need hundreds of microfarads.
The two bread boxes are up in the loft (aka the electronics workshop) ready to have everything laid out in them before I cut down the big heatsinks for the Coleman regs. And the rubber dampers should be here soon, so I will make up several of those suspension units and see what size holes I will need in the top plate for the valve platforms.
As far as looks go, I am leaning towards Art Deco, with maybe a sun or starburst veener motif on the front. More research needed!
The two bread boxes are up in the loft (aka the electronics workshop) ready to have everything laid out in them before I cut down the big heatsinks for the Coleman regs. And the rubber dampers should be here soon, so I will make up several of those suspension units and see what size holes I will need in the top plate for the valve platforms.
As far as looks go, I am leaning towards Art Deco, with maybe a sun or starburst veener motif on the front. More research needed!
I'm pretty lowbrow, frankly. I just buy motor run caps off ebay. The main thing is that they're polypropylene! Things like these:
Universal 25 UF Microfarad Motor Run Start Capacitor (400V 450V 500V) | eBay
Ducati 4.16.10.25.64 20uf Plastic Case Motor Run Capacitor | Rapid Online
http://www.ebay.co.uk/itm/CAPACITOR...hash=item3f4a3e1712:m:mycQ64b1eLBFSpG4nMuWQKg
They look a bit better without the screw:
http://www.amazon.co.uk/sourcingmap...15&keywords=motor+run+capacitor+polypropylene
Mind - we're nowhere near Jeffrey Stephenson here, "the Frank Lloyd Wright of PC case design...."
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Do you need soft start? You have directly heated tubes and a directly heated rectifier. They will all come up together in a second or two.
For a powerful amp, yes. For a preamp, not needed.
If you must have it, you can just use two power switches, one to turn on the filament supply, and the other that turns on the high voltage; you can flip the first, wait as long as you think is necessary, then flip the second. If you put them in series (HV after filament) you can never accidentally flip on the HV without having the filament power on first.
Isn't that delayed start?
And I've been assuming that the HT would be delayed by the sloth of the valve rectifier. Or should that be softened?
My question was actually prompted by noticing the raw filament voltage peaking at 24V before settling to 16V. If I opted for soft start in the PSUD2 simulation, it only peaked by about 1V. I wondered if that was a realistic sim, and if so would it be bad for the Coleman regs? I had a look at the regulator notes, but couldn't see an answer. Or if it's there, I couldn't understand it.
And I've been assuming that the HT would be delayed by the sloth of the valve rectifier. Or should that be softened?
My question was actually prompted by noticing the raw filament voltage peaking at 24V before settling to 16V. If I opted for soft start in the PSUD2 simulation, it only peaked by about 1V. I wondered if that was a realistic sim, and if so would it be bad for the Coleman regs? I had a look at the regulator notes, but couldn't see an answer. Or if it's there, I couldn't understand it.
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Yes, technically that is a delayed start but if your worry is hitting the tubes with HV before they're warm it will protect them against that. Really only an issue with big HV tubes.
I wouldn't worry about soft starting the filament supply. If you use Coleman regs they have soft start built in, anyway, for the filament.
I wouldn't worry about soft starting the filament supply. If you use Coleman regs they have soft start built in, anyway, for the filament.
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It's no problem, if you use 35V supply capacitors.
As you can see in my simulation, if the filament is conducting (in the case of small DHT tubes it is 10-20 sec), the hump is about 500ms wide.
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Phew! That's a relief. I hoped that might be the case, but it was worth checking.
Now I have to wait for bits and bobs to arrive from the far flung corners of the empire. Or Bulgaria in one case. So I will have time to re-read this thread, and maybe understand more of it this time.
Understanding LTspice is going to be my main challenge, even though there are tutorials. Simple things like using the "F" keys are alien to me, so that will be fun. I am the sort of person who can pick things up quickly if I can watch someone else do them, but learning by studying is harder.
So apologies in advance for stupid questions.
I hoped that might be the case, but it was worth checking.Now I have to wait for bits and bobs to arrive from the far flung corners of the empire. Or Bulgaria in one case. So I will have time to re-read this thread, and maybe understand more of it this time.
Understanding LTspice is going to be my main challenge, even though there are tutorials. Simple things like using the "F" keys are alien to me, so that will be fun.
I am the sort of person who can pick things up quickly if I can watch someone else do them, but learning by studying is harder. So apologies in advance for stupid questions.