L'Amp: A simple SIT Amp

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#2,441
gadut said:
did you find any strange sound before? great news SIT survived. once i set Vbias in opposite way, so it was biased with +4V 😀 i heard distorted music but i needed about 10sec to realize something was wrong on the circuit, but got no any smoke

it seems that SIT can absord human error, to give more courage on experiment.
Click to expand...

I did not, but i had left the place for a moment and when i came back the amps had fallen to half, i.e. one channel did not draw any amps anymore.
After a first panic attack i measured drain to ground voltages and found that one channel did not conduct anymore. "Goodness it must have gone poof!"

Jost
 
#2,443
plasnu said:
I'm wondering if the adjustable cathode bias like below is possible for for L'amp.

https://sites.google.com/site/yourtubeamp/mods-and-maintenance/bias/adjustable-cathode-bias
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Is possible, but like some circuits like this, with source bias (appearing here and there in various posts), again is good to return the speaker ground directly to SIT source, to relax the source decoupling cap and exclude them from output current path.
With proper component values will obtain smooth and more or less like PASS-SIT-1 range to tune output distortions. Some lab tweaking maybe will be needed.
 
#2,444
DIYBras said:
Is possible, but like some circuits like this, with source bias (appearing here and there in various posts), again is good to return the speaker ground directly to SIT source, to relax the source decoupling cap and exclude them from output current path.
With proper component values will obtain smooth and more or less like PASS-SIT-1 range to tune output distortions. Some lab tweaking maybe will be needed.
Click to expand...

Then I'll try to think what is the best way (value) doing it.
 
#2,447
Side effect of the WE connection, I mean.

What I've found to work for a given pair of reasonably matched SITs is to use a 50 watt rheostat to dial in the best value for the source resistor then I order the 50 watters as needed to make that value. There is thermal drift on my rheostat though so I have to measure it "hot".
 
#2,449
2sk180

I finally have an idea to make my amp with traditional chassis for easy adjustment. It's coming up nicely and please do advise if there is anything I could make it better.
 

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#2,458
This would be a controversial subject, but I would like to hear how you guys choose output DC blocking capacitor.

It seems like even Mr. Pass is bypassing Electrolytic with film on his SIT amps, so I guess the choice of the capacitor would make some considerable difference in sound, but I don't know how to choose the right ones. Probably, computer grade ultra low ESR bypassed with huge fancy film would be ideal, but since I follow Mr. Pass's philosophy, I'm trying to avoid using "too-fancy" audiophile parts as much as possible. So I would like to know what numbers (ESR, voltage, film cap size, etc) should I concern.
 
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#2,459
use what Nelson is using

and just slab big honkin' motor run cap in parallel

say 30-50uF

this side of Big Splash , we have Icar and Ducati

on your side there is GE and ....... you probably know

I believe in info that substantial number of Audiofool grade caps are nothing else than beautified motor-run caps
 
#2,460
I am using motor run caps in my crossovers. Best sound yet. I have a couple of sets of crossovers one with PIO caps and right now I am preferring the one with motor run caps. I agree wholeheartedly Zen.

(I believe in info that substantial number of Audiofool grade caps are nothing else than beautified motor-run caps)
 
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