LuminAria Article Available

[Michael Rothacher]

Good news, AudioXpress will feature LuminAria in this week's Audio Voice e-newsletter.

That means you'll be able to read and download the original article here:

You Can DIY!: LuminAria SIT Preamplifier | audioXpress

I'd like to thank the editors at AudioXpress for making this available and I hope you will be encouraged to show your support by subscribing.

I hope to have a new SIT preamp article for you this winter.

Mike

🙂

 

[crt]

thank you, just finish download it

 

[Antoinel]

Thank you Mr. Rothacher for this high quality, valuable and educational article.

 

[Michael Rothacher]

You're certainly welcome. My pleasure 🙂

When I did this, it was meant to be a "show the work (design and calculations)" piece, so there are some things I ultimately did differently for my own copy. The main difference being fixed bias, which Tim has done here as well to nice effect.

Also, just in case it comes up. The PCB's shown in the article have never been publicly available. They were special prototype boards I used that had all kinds of extra jumpers and pads so I could try a lot of different stuff, so I don't intend to release them. Maybe I'll do one for the next one...

 

[nicoch58]

Thanks ! great

 

[kasey197]

Mike thanks for this. I especially like the approach you used for the input buffer. Did you ever get a chance to measure the buffer standalone thd vs freq when fed with a high source impedance generator (say 20k)? I'd lash it up to try but don't have the part to hand.

 

[Michael Rothacher]

You're welcome. Glad you enjoyed it. I'll check on that. It's been a few years now 🙂 I doubt I would have gone as high as a 20k source impedance. What music source are we planning to use? The eff. input capacitance is around a hundred pf, so you can figure out the FR from there.

In actuality, the buffer is made this way, because it was intended to (also) work with a certain unobtainium part I had on hand in the same circuit with some resistor value changes. That part has an input capacitance of a couple pf.

 

[wdecho]

I hope to have a new SIT preamp article for you this winter.

Mike

🙂[/QUOTE]

With an available SIT? I enjoyed reading the article also and it is a shame the SIT is pretty much unattainable.

 

[Michael Rothacher]

I do feel a bit guilty about writing about unobtainium. I wish I had more control over that. Unfortunately, whenever Nelson or I mention a part number, they seem to start to vanish. Maybe we should start a chip fab 🙂

I should probably get back to more obtainable stuff, but this stuff is just so darn fun.

 

[kasey197]

You're welcome. Glad you enjoyed it. I'll check on that. It's been a few years now 🙂 I doubt I would have gone as high as a 20k source impedance. What music source are we planning to use? The eff. input capacitance is around a hundred pf, so you can figure out the FR from

That would be 50 percent of a 47k pot hung in front of the buffer 😀

It's not the FR per-se that is of direct interest but the impact of the fet's varying input capacitance on THD if a reasonably high impedance pot is used.
No worries though - enough hints so far from you so that I can do the rest 😉

 

[Michael Rothacher]

I thought you were interested in the buffer's intrinsic performance, since the volume pot is somewhat an arbitrary choice, smarty pants 😀

You can take it from here.

 

[Michael Rothacher]

The blue dashed line is taken with the input volume control at 50% if my old notes are to be believed. I'm sorry I missed that you were interested in THD not FR.

 

[Zen Mod]

that article is for long (right after publishing) time one of my fave

 

[Michael Rothacher]

Thanks, ZM 🙂

 

[jps1964]

... the homepage articles and youtube videos too!