Sgregory: I re-read that section of MJ VA last night and it seems to apply to LC topology as you mentioned.........
If you visualize a CLC design with varying C1 values from very small to large enough to no longer increase B+ as the spectrum between an LC and a C filter, I would assume that as the value of C1 gets small the ripple current grows and starts getting important. I just played around in PSUDII and this appears to be the case.
I suppose that when using a large value of C1 (above 10uf or so) in a CLC filter one has to worry only about nominal idle current for sizing the choke.
Perhaps one of the experts can chime in and enlighten us a bit on this.......
If you visualize a CLC design with varying C1 values from very small to large enough to no longer increase B+ as the spectrum between an LC and a C filter, I would assume that as the value of C1 gets small the ripple current grows and starts getting important. I just played around in PSUDII and this appears to be the case.
I suppose that when using a large value of C1 (above 10uf or so) in a CLC filter one has to worry only about nominal idle current for sizing the choke.
Perhaps one of the experts can chime in and enlighten us a bit on this.......
boywonder,
You are correct.
There is an upper limit to the size of the capacitor as well when using a SS rectifier, based on the winding impedance of the PT. I am pushing that limit with the OPUS ;-)
I played around with the math a while back but found it much easier and intuitive to use PSUDII.
You are correct.
There is an upper limit to the size of the capacitor as well when using a SS rectifier, based on the winding impedance of the PT. I am pushing that limit with the OPUS ;-)
I played around with the math a while back but found it much easier and intuitive to use PSUDII.
Been a bit quiet here, hasn't it? Good job I'm not holding my breath whilst waiting to see who will dive in and build the thing. I'm in no hurry, I've downloaded everything I need. Ta, very much.
I'm currently building a 5-20. I'm calling mine the Mallard 5-20. Get it? Similar to yours but with EL34s with a Bias circuit.
Your one, when I build it will be the Mallard 5-50. I have a different source of transformers in the UK.
VVT Transformers.
For my bias supply I'll use a small tranny with 2x 120v primaries and 2x 12v secondaries. Wiring the 2x 12v in parallel and the 2x 120v in parallel. Connect the 12v winding across a 6.3v supply on main tranny and get 60v out of "primary" on small tranny. I could ask for extra 60v taps on the main tranny but this way is cheaper. Less than $10.
Its been interesting reading, so far. Many thanks.
I'm currently building a 5-20. I'm calling mine the Mallard 5-20. Get it? Similar to yours but with EL34s with a Bias circuit.
Your one, when I build it will be the Mallard 5-50. I have a different source of transformers in the UK.
VVT Transformers.
For my bias supply I'll use a small tranny with 2x 120v primaries and 2x 12v secondaries. Wiring the 2x 12v in parallel and the 2x 120v in parallel. Connect the 12v winding across a 6.3v supply on main tranny and get 60v out of "primary" on small tranny. I could ask for extra 60v taps on the main tranny but this way is cheaper. Less than $10.
Its been interesting reading, so far. Many thanks.
It is a gate stopper to prevent oscillation. Does the same thing as the grid stopper on a tube.
Nice to see some activity here. I'm still collecting parts (for this and 2 other projects.) My high voltage junk box is still rather sparse. Maybe I should trade in some big heatsinks. 🙂
..Todd
..Todd
Thanks for the info. It was getting to me, just like an itch that you can't quite scratch.
Would you believe it. I ordered all my trannies from VVT Transformers today. 2x VTK15145-1300 magnetics kit drop thru.
£146.08 inc Tax & Delivery in the UK. Not only did I save £100 on two kits but they are adding 60v taps at no extra charge. They are good for my 25w monoblocks. 😀
UK Non JavaScript Price List
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I have all the iron as well, but we are in the middle of moving across the country and I have no idea when I'll get a chance to build the thing. Hopefully in the spring. In the mean time, I'm thinking about refitting the driver section into a Dynaco ST70 to see how it performs. I can likely manage that limited amount of construction.
Hi smbrown,
What iron do you have for this?
Keep us posted on how that ST-70 experiment goes.
..Todd
What iron do you have for this?
Keep us posted on how that ST-70 experiment goes.
..Todd
Another site I found today supplies Danbury Transformers. They've been around many years.
Valves And Transformers (Contents)
Valves And Transformers (Contents)
Though I've not done my own math analysis of the ECC88 stage, a quick glance at the 12/27/2010 schematic looks as though there is 183 volts across the ECC88. I think the Vmax spec for that tube is 130 volts. Did I miss something ?
Having just checked the Phillips datasheet, "it may be worse than that jim", errr Glassguy.
It appears that the 130v max is at Cold. The working max is 90v per anode. I get the impression that this valve is meant to be a cascode amp only.
Oh and appologies to any Star Trek fans on 'ere.
It appears that the 130v max is at Cold. The working max is 90v per anode. I get the impression that this valve is meant to be a cascode amp only.
Oh and appologies to any Star Trek fans on 'ere.
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Well, the guys here that spec'd that tube and its operating points are seasoned veterans, so I suspect that the tube will be happy operating at the points outlined on the schematic. Or perhaps there's a mistake drawn into the schematic. I just don't believe these guys would have taken this amp so far without noticing that tube won't get the job done.
That's why I was hoping one of them (or any of the resident tube amp whiz's here) would chime in on the subject.
..Todd
That's why I was hoping one of them (or any of the resident tube amp whiz's here) would chime in on the subject.
..Todd
I'll wait and see, as Shakespeare wrote " With bated breath and whisp’ring humbleness. " 
Quote from "The Merchant of Venice"
Quote from "The Merchant of Venice"
I think I recall seeing in one of Morgan Jones' tube publications, the ECC88 was considered an excellent choice for a Cascode stage. I've not been following this amp project closely since it's inception, however I've occasionally looked in on the progress. A couple of things I thought would have shown up in this amp development scheme would be a Cascode input stage, and the Long Tail driver stage using a 12BH7. I think the 12BH7 idea was introduced at some point, but apparently never developed much interest.
The 12bh7 was a good sounding tube and worked very well is the LTP driver. I may go back to it soon.
I'm mulling over shoe-horning an Hashimoto HW-60-5 onto a test bed 5-20 Frankenstein in my possession , whist of course not an ideal fit into the existing circuit I'm curious as to how much further a modern production double c core transformer can squeeze out of the old girl and I would be grateful for any thoughts or input on this "for the hell of it" project !
http://www.tube-amps.net/HP_HW_60_5.htm
http://www.tube-amps.net/HP_HW_60_5.htm
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