L'Amp: A simple SIT Amp

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#1,181
hi everyone,

i received my transistors recently and will start building soon.🙂

i have not built many amps so my instinct tells me one could have a nice upgrade using ''fancy'' output capacitor,compared to say pana FC.

i ve been tempted by the nichicon KG and Mundorf m-lytic. also maybe mundorf bipolar Ecap?

what do you guys use and which one would you like to try in the future?
 
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#1,184
🙂 i think nowadays there is no bad ones you can choose for that purpose ( panasonic, nichicon, elna, rubycon, epcos, Rifa ,etc..) but the bigger you can choose the bypass ones the bigger impact it will have one sound . i have found that 10uf onpen up the highs and high medium but could'nt here any improve with lower than 1uf bypass with this 10000uf output cap.
Nelson usually use 3 or 4uf 🙂
 
#1,185
It is very interesting to read this articles mentioned in the F3 thread

http://www.diyaudio.com/forums/pass-labs/137145-f3-builders-thread-46.html#post3038615

Combined with Nelson's words in the 6moons article about the SIT-1 where he states that the SIT-1 has an output impedance of about 40 and the SIT-2 of about 240. (thanks juanitox for the hint 😀 )

Now I understand better why the SIT-1 sounds not as thin as the L'amp with thickfilm resistors. 40R output impedance against 5R. With current amps Nelson mostly seems to prefer about 50R. So the SIT -2 will use a resistor of at least 100 Ohm parallel to the output to get the impedance of the current amp down.

Now I understand better why my MU follower with two R100 had such strong bass and highs with my open baffle.....I suppose the current amp output impedance was in the region of the SIT-2 and the impedance rise of the tone Tubby in the lower frequency range and the rise of the PM6A in the higher region
made a spectacular loudness effect........! 😀😀
 
#1,189
??

in both OM's Papa is stating output impedance of 4R

even if I may allow possibility of copy-paste of entire data page from one OM to other (they're identical completely ) , at least one of them is having 4R as output impedance

:clown:


edit:

refreshing page sometimes can reveal replies posted in a meantime

:rofl: dumb ZM
 
#1,190
yes indeed Zen Mod,

I mixed up the load resistance and the output impedance and of course still is valid what Mike wrote in his first article

" The effective load is our light bulb resistance in parallel with our 8 Ohm speaker, or about 5 Ohms."

besides my mixing up the nomenclature I only wanted to draw attention on the load resistor size and a possible connection to the sound impression.....🙂

I hope it is no problem to copy these words from 6moons

"Nelson Pass. It's interesting that the harmonic values vary quite a bit on the SIT-1 with operating points but the actual sound not as wildly. Another case where the explanations probably are way too simple. I adjust the SIT-2 for the same distortion waveform at 1 watt as the center point of the dial on the SIT-1 but they are still not exactly the same. The SIT-1 sees about 40 ohms in parallel with the load and the SIT-2 about 150 ohms."
 
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