# working out Z out for tube with IXYS IXP10M45S plate load

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#### duderduderini

Hi There
I would like some guidance as to how to work out Z out of a tube with its plate load being supplied by the IXP10M45S.
I have read the article at maarten@platenspieler.com and I figure It probably should be MU follower formulas given the output is taken from the anode of the driven tube.
Given the Current regulator does not have the plethora of caps and resistors though, I am wondering if it may be accurate.
I would appreciate any help
Thanks
Nick

#### EC8010

It's just ra (at the operating point). As simple as that.

#### duderduderini

so if we use e180f as triode

Hi Ec
Hope your xmas woas good and that 2008 is fine for all.
The datasheet for the e180f seems to only provide data in pentode op.
At this point i have the setip working at 5.5 mA and 153V so is it as simple as V/I?
Thanks

#### EC8010

If you look on the E180F data sheet, you should find it gives a value for mu(g1-g2). This is the same as the triode mu. You can find gm at your operating current using the pentode data, and from that use ra(triode) = gm x mu(g1-g2).

#### duderduderini

At the risk of sounding completely stupid

Hi Again
Ok mu=50
Gm.. is that transconductance or is it derived by operating point (150V @ 5.1mA) ?
Thanks

#### duderduderini

Thanks for the triode datasheet

I will try increasing current.. i find with other tubes that they can sound a bit unpleasant at higher anode currents.. Is that my imagination?
The 180F at 5.1 doesnt sound objectionable at this point but i will double the current and see for myself
Once agin thanks for the datasheet.
Nick

#### duderduderini

So is this the Ra

Hi
using Ec's formula ra(triode) = gm x mu(g1-g2).
refering to the triode sheet for the 180F
mu=60
gm =17.6 so rA=1056
on the triode data sheete refered to in this post a valus for Rp is given of 3.4k
Ra is not the same as rp i take it?
Thanks

#### EC8010

Re: So is this the Ra

duderduderini said:
using Ec's formula ra(triode) = gm x mu(g1-g2).

That's because the twit EC had his brains out of gear. He meant to say ra = u/gm. If he had spent less time on formatting and more on thinking, he wouldn't have confused you. My apologies.

#### duderduderini

I am always confused

Hi EC
dont worry.. i sppend much of my life in a confused state these days as I find it helps with the vagaries of modern life. Thanks to all for your help.
I plan to construct an riaa stage based on the e180f in triode mode and the ixys current regulator..
Will see how it works.
Thanks
Nick

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