to get close to this amplifier you need to have very clear ideas and know which speakers to match it with
With the single pair, which is then the native scheme, it has obvious limits in the low range, articulation and dynamics of the medium-low, but medium and high and voices are very interesting.
You want to work around, which would then no longer be a 108 and not even a clone of 108, you can get very interesting results
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Shorting or not the inputs has no effect on the offset as there is an input coupling cap. I prefer adjusting with a dummy load at output, but do not think the absence of a load can in any way affect the health of the amp. The original does indeed blow the fuses when powered without a load but this is due to the activation of the crowbar protection. When no load is connected the power on spike at output is sufficient the trigger the protection which blows the fuses.
Anyway, none of this has any relevance to audible noise.
I will try to take all of my components out of the power outlet to check if there is a link in the chain that causes that noise. As for a dummy load, what would you suggest ( to be in the safe side, just in case )?
If you are trying to light an led with 12 volts, I think that 47K resistor is too much.
Is there noise when nothing is connected and the input is shorted?
For dc adjustment power rating is not critical at all. Whatever you have, 3W is just fine. The worst that can happen is a blown resistor.
Otoh, it is not a bad idea to invest into high power, heatsinkable resistors, so you can test AC performance, max power, clipping behaviour, etc. I have a bunch of 50W 22R resistors and a toggle switch can select parallel and series/parallel combinations using 5 resistors. I think i get around 4ohms and 7.4ohms as test loads.
This noise is too low, I have to get really close to my speakers in order to hear it, but it wasn't present about a month ago. I will check for bad connections and possible interference from neighboring devices. And since it's no harm to do so, I will also check the dc settings, just to be sure that everything flows well.
As for shorting the inputs, also about a month ago I've accidentaly pulled an interconnect from my preamplifier and when I powered the power amp it produced a noise in speakers like a short. I turned off everything, checked the cables, found the mistake, fixed it and it worked fine. But this makes me double think the possibility of shorting the inputs while the amplifier is connected to my speakers.
As for shorting the inputs, also about a month ago I've accidentaly pulled an interconnect from my preamplifier and when I powered the power amp it produced a noise in speakers like a short. I turned off everything, checked the cables, found the mistake, fixed it and it worked fine. But this makes me double think the possibility of shorting the inputs while the amplifier is connected to my speakers.
No I take from the amplifiers 46 VDC supply. But still I think the 47 kohm is to much. Depends on the Quality off the LEDs.
By at least a factor of 10. Where is that Ohm's law when you need it?
Well, is it here..??
LED Resistor Calculator
You can not use that calculator. Modern LEDs is so much efficient then earlier.
4 pairs? My interest is piqued.
Is it for higher power, 1 ohm loads or class A? What voltage rails do you have?
Yes, 4 pairs, but we can not talk about Dartzeel anymore
substituted Q 9, 10, 90 and 100 from MJE in to 220 with power transistors the same as the final, the polarizations for the 4 pairs, R 19 and 20 and Z 1 and 2 have been changed
changed C 15, 16, 17, 18
0.22 ohm resistors on emitter power end transistors
Powered input and driver with VCC stabilized at 60 VDC
Powered final stages of power with VCC stabilized at 50 VDC
Replaced C 6 and C 7 with higher quality cap
Bel finale, but another final, a result of stature