D3a in triode mode

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RhythMick
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#46 Re: D3a in triode mode

Post by RhythMick »

IslandPink wrote: Fri Jul 16, 2021 5:46 pm What's the frequency ?
1KHz square wave, 100mV pk input
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IslandPink
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#47 Re: D3a in triode mode

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It's not great is it - but is D3a in ultra-linear supposed to be any better than output valves are in ultra-linear, ie. not very linear ?
Is the gain 200+ as you said, so that would be 20V Pk out ( is that Pk to Pk ? )
A few odd-order distortion products could produce that.
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Nick
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#48 Re: D3a in triode mode

Post by Nick »

And ringing. Band limit the input and it will look better.
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RhythMick
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#49 Re: D3a in triode mode

Post by RhythMick »

I've never used ultra linear before, only trying it on suggestion from Jac (and while I have everything accessible for experimentation).

Band limit the input ... Translating that as a low pass filter on the input limiting to say 20Khz?

Ok I'll work on that for fun and learning.
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#50 Re: D3a in triode mode

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IslandPink wrote: Fri Jul 16, 2021 7:44 pm It's not great is it - but is D3a in ultra-linear supposed to be any better than output valves are in ultra-linear, ie. not very linear ?
Is the gain 200+ as you said, so that would be 20V Pk out ( is that Pk to Pk ? )
A few odd-order distortion products could produce that.
100mV peak, 14.7Vpk out. This mode gives gain of 147. Just not very linear. I'll probably shy away from it and stick with either triode or pentode.

It seems odd to me anyway because G2 is bound to be at a higher voltage than the anode by 1200R (one coil) x 17mA = 20V
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#51 Re: D3a in triode mode

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RhythMick wrote: Sat Jul 17, 2021 10:19 am
IslandPink wrote: Fri Jul 16, 2021 7:44 pm It's not great is it - but is D3a in ultra-linear supposed to be any better than output valves are in ultra-linear, ie. not very linear ?
Is the gain 200+ as you said, so that would be 20V Pk out ( is that Pk to Pk ? )
A few odd-order distortion products could produce that.
100mV peak, 14.7Vpk out. This mode gives gain of 147. Just not very linear. I'll probably shy away from it and stick with either triode or pentode.

It seems odd to me anyway because G2 is bound to be at a higher voltage than the anode by 1200R (one coil) x 17mA = 20V
And by that logic of course I should put something like a 10k resistor between choke and G2 to drop 50V at 5mA
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Nick
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#52 Re: D3a in triode mode

Post by Nick »

Remember ultra linear can be done with resistors and caps as well as inductors.
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RhythMick
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#53 Re: D3a in triode mode

Post by RhythMick »

I tried 8k between choke mid point and G2 and it made no difference to the shape of then output.

I'll set UL aside to maybe come back to in a few years when I understand more.
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