Luminaria?

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board is in production…

Spice was very interesting…. but it took me nevertheless many hours to get with the SK82 model and some changes in the circuit the right values to have a low distortion success…….

So it seem every build must be trimmed with care…….

it is the second time after my SIT-1 clone simulation that I saw the load line cancelation so clearly….

but this cancelation is very fragile, so it is good that Nelson implemented the meter with the green area.

This is not a feature it is a must…….!
:):):)
 

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Me too Generg....

Hi all!

Have my spare 2SK82(KD-33) waiting. And I have bought the AudioExpress with the Luminara-article.
So when my FrugalHornXL is finished tomorrow - the planning for items can begin...
Or maybe wait for the autumn??

We will see - now I`m included in this tread - and can get updates....:cool:

Best

Olav
 
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You brave ones can also experiment with the load value a bit as well. Just remember, this wasn't a plug-and-play beginner project. It was a proof of concept piece, but an adventurous spirit will be rewarded. :)

And, don't forget, you have to think about how you're using the volume controls as well, especially if things start to sound too rolled-off (dark).

I'm still listening to mine.
 
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So let me put a brave question......:)

When go tomorrow on distortion tour....

This way first.... I adjust the 50-60mA und the 90V you started with, look at the distortion....and when I do not like it

I change with the pot the SIT gate bias until I find a good point......

Or better I let the gate bias stay and change the drain resistor?......

Or better a mix of both, I bet this will give more time for confusion......:)

Or I better....

:D

I hope you understand a bit.....
 
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Adjust for 50-60mA @ 90V or so first. Look for low distortion but don't worry specifically about hitting 30ppm. Look at your spectrum, adjust and listen.

Remember the volume controls are affecting the frequency response. Review this section of the article. If your friend thinks the preamp sounds too "dark", the more likely cause is the volume control settings, rather than spectral specifics. I'll assume he built the buffer section and has volume controls at the input and output, yes?

Rinse and repeat.

Save the drain load for another time.

Most important: have fun :)
 
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So, so true :)

Incidentally, you should settle on a convention for initial adjustment, e.g. both volume controls wide open, then later after you've figured out the best way to use the volume controls, e.g. output open, input for volume control, etc. then you might consider adjusting at the nominal listening settings.

Make sense?
 
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LUMINARIA

so…….:D

I had to augment the drain resistor to 700R and the bias voltage for my SK82 was around -14.5V and the working point was then 105V/55mA and the distortion looks good.

It is difficult to get the 230/120V Xformer here. The one I use now is a bit weak and gets hot.

No hearing at the moment, the system is balanced and I have to change the amps, get a stronger transformer…. he will not work for two channels…..

So some time will pass…..

Thanks Mike, it works technically perfect, hearing will come….

forgot, distortion is for 1V output in 5k load
:):):)
 

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o.k. I just measured again and it is more clear now…

one channel has about 10x gain, the other around 6,2x.

I now can manage the distortion very well, but how to influence the gain?

Changing the drain resistor did not change the gain really, so I am afraid I have to match the SK82 for the right and left channel……

HUHUUU, not so easy I suppose to find two really equal….

let us do some 100dB negative feedback that puts away these differences…

so we will have no gain any more and they are finally equal…..:D
 
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O.K. :D

I took two KE instead of the KD my friend had implemented and I cared that they had a similar curve shape in the low current area around 60mA.

The curves were made with Locky-z curve tracer that is not so ideal for this purpose because the gate bias negative voltage is subtracted from the DS voltage and the headroom is only 24V for all…..

Nevertheless it worked….. :_)

gain is very equal now 1,03V output and the distortions are very similar.

One channel hat a rising and falling k2 but when I changed the supplementary drain resistor from 100R (Mikes uses 600R, I added this 100R to get the distortion down with my SK82) to 68R the situation was stable. Do not know why.

Possible conclusion two matched KE are better than two unmatched KD…. :)

Mike many thanks so far for this experience with the possibilities of a SIT in a Pre…. it was very interesting.

I hope my stronger transformer will come soon and I can start to hear.

:spin::spin::spin::spin:
 
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Very well done, Gerd, as always.

If you take a look at my prototype you may notice I have an extra pot near the drain resistor for tweaking the load. :)

Incidentally, Luminaria gets its name from the audio critic expression "lit from within", and that's about how it ought to sound when all the stars are in proper alignment.
 

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O.K. thanks Mike for the compliments….. :)

first hearing impressions with my version, that differs to yours in some points.

+ very big room

+ very live like

+ wonderful voices

+ very good details in the highs

+ good positioning

- bass to shy or too less punch

So I am very eager to hear them with the Vishay thin film resistors for drain you use.
I saw this point only now on your new picture clearly and I know from the L`Amp how much difference the material of the drain resistor does.

Mine are at the moment wire wound and these tend to a softer and not punchy sound.

In the SIT-1 Nelson uses also thin film resistors.

I plan to exchange them the next days and maybe even the source resistor so this micht be too much. Sound may become too thin, I will see….. :)

Would you tell me the value of the small blue pot you made parallel to the drain resistor?
 
The Full energy.....

Hi Generg.

Do you build the full pack-amp(Luminaria) - with both Buffer and the SIT-pre? I have some of the stuff to the SIT-pre and will start with this part in the autumn. Then I can build the buffer at a later time - when I want some more juice to the sound. Just finished the FHXL with my old Alp10.2 and it is superb - but must give time to other projects in the house (+ Wife and kids in summer).

Wonder if I`m gonna order 2 piece 60VAC transformator(200 or 300 watt) to 2 bridges - and wire the DC in seriell to give 145 volt.
Should be a good solution - I think......:yinyang:

Best
Olav