CC Source in a Spud?

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Dave the bass
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#61 Re: CC Source in a Spud?

Post by Dave the bass »

pre65 wrote: Sat Jul 29, 2017 9:15 pm So, would 3.5K (approx) be optimal ?
It depends on what your idea of 'optimal' is I'd guess Phil, where did the 3K5 figure come from out of interest? Explain yer innermost thoughts :)
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#62 Re: CC Source in a Spud?

Post by pre65 »

Dave the bass wrote: Sat Jul 29, 2017 9:27 pm
pre65 wrote: Sat Jul 29, 2017 9:15 pm So, would 3.5K (approx) be optimal ?
It depends on what your idea of 'optimal' is I'd guess Phil, where did the 3K5 figure come from out of interest? Explain yer innermost thoughts :)
Ooh err, are you a psychoanalyst ? :)

I estimated that a 3K5 loadlone would cross the loadlines at 90 degrees.

Don't laugh. :oops:
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#63 Re: CC Source in a Spud?

Post by Dave the bass »

pre65 wrote: Sat Jul 29, 2017 9:40 pm

Ooh err, are you a psychoanalyst ? :)

I estimated that a 3K5 loadlone would cross the loadlines at 90 degrees.

Don't laugh. :oops:
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Thats sound reasoning Phil, I see where you're coming from.

I made a picture for 3K5

Image
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#64 Re: CC Source in a Spud?

Post by IslandPink »

Yes but you need to be further up in current, nearer the dissipation limit - then you don't get down into the 'mush' on the lower right hand end of the swing. So you need to have a different cathode resistor to change the operating point so the whole line can move up.
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#65 Re: CC Source in a Spud?

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I thought there were procedures regarding current and voltage to establish fixed points on the axis and thence to plot the load line ?
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#66 Re: CC Source in a Spud?

Post by Dave the bass »

Doink! Penny Drop! Thats why the 8/10/14K loads so sound lush and lovely....they don't enter that 'mush' region to the right so 'sharply' ... the high Z loadlines carry on in the more linear section.

Dagnabbit! We've done learning! Ta team!

EDIT. Double doink penny drop, that relates to the post Nick made about the looking at the dots and spacings too. Got it! today is a good day.
Last edited by Dave the bass on Sat Jul 29, 2017 10:17 pm, edited 1 time in total.
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#67 Re: CC Source in a Spud?

Post by Dave the bass »

pre65 wrote: Sat Jul 29, 2017 10:11 pm I thought there were procedures regarding current and voltage to establish fixed points on the axis and thence to plot the load line ?
"SOA"? Safe operating area? Is that what you're thinking of?
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#68 Re: CC Source in a Spud?

Post by IslandPink »

Yes - so for example get your starting point to 6W by going for 175V and 35mA, then draw the same line and it cuts through the grid lines a lot more evenly.
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#69 Re: CC Source in a Spud?

Post by pre65 »

Dave the bass wrote: Sat Jul 29, 2017 10:15 pm
"SOA"? Safe operating area? Is that what you're thinking of?
Fcuk knows, load lines are something I can understand on data sheets but I can't remember much about plotting them.

The (very) old bwain is not too good at remembering things these days. :(
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#70 Re: CC Source in a Spud?

Post by Dave the bass »

IslandPink wrote: Sat Jul 29, 2017 10:19 pm Yes - so for example get your starting point to 6W by going for 175V and 35mA, then draw the same line and it cuts through the grid lines a lot more evenly.
Yep, I see it, I see it.....but I refer the honourable Gent to the General Parameters box in the loadlines!

150V is quoted max for Anode... I have gone beyond that on 1 pair 6C45, no kittens died. There was also no audible 'gain' IMO.
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#71 Re: CC Source in a Spud?

Post by Nick »

That 150v is dc. You can go beyond that temporaly. Draw the max dissipation curve on the graph. Then find a idle point close ish to that. Or not but at least you know what area not to go into.
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#72 Re: CC Source in a Spud?

Post by simon »

There's some stuff about load lines about half way down this page that might help, our Dave and our Phil?

http://simonsnewadventuresinhifi.blogsp ... e.html?m=1
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#73 Re: CC Source in a Spud?

Post by Nick »

I would try 180v 35ma. Working the valve hard but worth a try. Maybe 2k5 load
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#74 Re: CC Source in a Spud?

Post by Dave the bass »

Cooooooolio!

Max Anode dissipation is the pink arc on each set of Anode curves, 7.8W apparently. Thanks for the help all. OK, I'll revise the OP, I know its a bruiser of a valve and the Anode is made of stuff our-Ali eats for breakfast, I was being a soft southern Jessie as normal!

My reasoning for picking the 2V bias is it allows me to make full use of the swing available (in theory) from the source, made sense to me.
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#75 Re: CC Source in a Spud?

Post by Paul Barker »

Dave the bass wrote: Sun Jul 30, 2017 9:41 am Cooooooolio

My reasoning for picking the 2V bias is it allows me to make full use of the swing available (in theory) from the source, made sense to me.
Nicks quiescent operating point would be at around -2v so thta box is ticked. You might want a low output impedance source though for best performance. A cf buffer if not.
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