GK-71 - economical build.
- andrew Ivimey
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#46
Nadbness .... ooops can't even blame cyrillic script but I love it. My blah blah 509s had a plasma flame but nothing as wild as these!
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#47
VTTCs with staccato modulation, for some reason, produce a very different plasma discharge to most solid-state TCs (SSTCs ot DRSSTCs) or SRSG (traditional synchronised rotating spark gap) coils - more like a modern QCW TC (the latest designs).andrew Ivimey wrote:Nadbness .... ooops can't even blame cyrillic script but I love it. My blah blah 509s had a plasma flame but nothing as wild as these!
Built one a few years ago with an 833 - I love the smell of ozone in the morning...
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#49
VTTC - Vacuum Tube Tesla Coilsimon wrote:I didn't understand any of those acronyms. And if I had I don't think I'd have known what they meant. Cool vid though.
SSTC - Solid State Tesla Coil (quite basic & simple)
DRSSTC - Doubly Resonant Tesla Coil (more advanced version of SSTC when both primary & secondary coils are tuned & driven - requires current sensing feedback from the primary - can be made HUGE)
QCW - Quasi Continuous Wave - a type of DRSSTC with the addition of a main bus supply that is servo-driven, effectively an extremely powerful arbitrary waveform generator - can generate sparks many times the length of the secondary coil. QCW is the current state of the art in solid-state Tesla Coils
SRSG - Synchronous Rotary Spark Gap Tesla Coil - pretty much the original Tesla Coils design - uses an NST (Neon Sign Transformer), a capacitor and a spark gap driven by a synchronous motor.
A plasma speaker is essentially an RF Tesla Coil running at several MHz with a class E driver which is audio modulated.
Last edited by jack on Wed Aug 21, 2013 12:13 pm, edited 1 time in total.
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#50
You'd need all of the above to make my bwain spark.
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Edmund Burke
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#52
Hot news.
I now have a pair of GK-71.
I've just started the ACF pre, so might see how that goes before starting on the power amps.
I now have a pair of GK-71.
I've just started the ACF pre, so might see how that goes before starting on the power amps.
The only thing necessary for the triumph of evil is for good men to do nothing.
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G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
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#53
I'm having a think in a quiet moment (I get them occasionally) about driving the GK-71.
Rather than copy Mark and use 4P1L I wondered whether 12HG7 as a pentode would be worth a try.
Just to be different.
Rather than copy Mark and use 4P1L I wondered whether 12HG7 as a pentode would be worth a try.
Just to be different.
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
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- IslandPink
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#54
Certainly possible .
You'll get plenty of gain , maybe too much !
Something like 30 or 35mA with a 6k load would be good .
What do you think of the GK-71 then, for £12 each ?
You'll get plenty of gain , maybe too much !
Something like 30 or 35mA with a 6k load would be good .
What do you think of the GK-71 then, for £12 each ?
"Once you find out ... the Circumstances ; then you can go out"
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#55
Not bad.IslandPink wrote:Certainly possible .
You'll get plenty of gain , maybe too much !
Something like 30 or 35mA with a 6k load would be good .
What do you think of the GK-71 then, for £12 each ?
Pete Millett used a 4K load on his 813 amp.
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
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#56
Shock horror.
I've decided my dual mono PSU is not up to the job of supplying the necessary oomph for GK71, so I've started on something different. My chokes are limited in ma so the PSU will split after the rectifier (hybrid bridge) into two sections.
Still not sure if I can get to Owston in November, but I'd like to have something new to bring if I do get the chance.
I've decided my dual mono PSU is not up to the job of supplying the necessary oomph for GK71, so I've started on something different. My chokes are limited in ma so the PSU will split after the rectifier (hybrid bridge) into two sections.
Still not sure if I can get to Owston in November, but I'd like to have something new to bring if I do get the chance.
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
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#57
Would a driver valve with an amplification factor of 35 be enough to drive a GK71 ?
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#58
Dunno, depends what it is
Maybe I can work towards a better answer -
(i) Is 35 enough gain for your system ?
(ii) What is the B+ going to be for the GK-71 , and are you flexible about the supply voltage for the driver ?
Maybe I can work towards a better answer -
(i) Is 35 enough gain for your system ?
(ii) What is the B+ going to be for the GK-71 , and are you flexible about the supply voltage for the driver ?
"Once you find out ... the Circumstances ; then you can go out"
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#59
I was thinking of my 6N7 (or whatever the CV number is - CV1285 I think).
http://www.r-type.org/exhib/aac0112.htm
Twin triode with a common cathode. Probably with a CCS on the anode as I'm plum out of anode chokes.
Some many years ago our very own Paul Barker reckoned they would be ace for driving GM-70.
http://www.r-type.org/exhib/aac0112.htm
Twin triode with a common cathode. Probably with a CCS on the anode as I'm plum out of anode chokes.
Some many years ago our very own Paul Barker reckoned they would be ace for driving GM-70.
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
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#60
I'm not sure how you'd use this one, but I'm sure Paul , Nick or James could comment better . It seems to be aimed at Class B usage, and the data sheet shows quite low current for Class A operating points . I'm concerned about grid current on the input for the higher current class B type operating points . It'll need to run at maybe 25mA to drive a GK71 properly , although I still have no idea what your B+ is going to be, or why you can't answer that question - it will tell me what sort of current and voltage swing you are aiming to acheive into the grid of the GK-71 .
"Once you find out ... the Circumstances ; then you can go out"