Question re Izzy Wizzy phono stage

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RhythMick
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#16 Re: Question re Izzy Wizzy phono stage

Post by RhythMick »

izzy wizzy wrote: Wed Jul 21, 2021 8:41 am Here it is. It's a bit of a mess but seems to work fine.

My LTSPICE is setup like the Tutorials on Intact Audio with the files by Stephie Bench so uses drop down tube models. I'm not sure this will work with LTSPICE using the regular models.

Make sure you have the latest version.
Many thanks
RhythMick
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#17 Re: Question re Izzy Wizzy phono stage

Post by RhythMick »

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Apologies for the dumb question. Working my way through my design and the DC coupling values to the next stage. I think I know the answer but really just want to check.

Output taken from D3a anode is an AC signal riding on a DC offset. That will present at the grids of the valves on the LTP pair. Am I correct in saying that the DC value will be the same as the D3a anode.

I'm pretty sure that's right - there's no DC path to ground through the RIAA. Just not trusting myself quite enough having not done RIAA before.
izzy wizzy
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#18 Re: Question re Izzy Wizzy phono stage

Post by izzy wizzy »

Yes. DC at 5687 grids is the same as D3a anode. There's no dc current in the series resistor or the 510k to the other 5687 grid.

I didn't want to take the 510k much higher in value as that departed too much from max grid R for 5687. It's possible to increase it to 1M with maybe no ill effect. The maybe is not something I've tested.

It's a common topology in power amps.
Last edited by izzy wizzy on Tue Aug 31, 2021 10:06 pm, edited 1 time in total.
RhythMick
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#19 Re: Question re Izzy Wizzy phono stage

Post by RhythMick »

Thanks for confirming.

In true Mick style I've departed from the safe path and gone off-piste. I'll draw up what I'm building and post for general merriment and laughter if nothing else.

It'll all end in tears...
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