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Pass Aleph P 1.7 preamp builders thread
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Old 3rd April 2018, 03:16 PM   #521
Zen Mod is offline Zen Mod  Serbia
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Pass Aleph P 1.7 preamp builders thread
will try tonight to clear your mess
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Old 3rd April 2018, 07:59 PM   #522
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Q: Can it have anything to do with the fact that the volume control and the source switch are mounted on a steel plate so it is that one that has to be grounded....??

......if you lay your hand on this steel plate, does the humming change? (better or worse?)
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Old 16th April 2018, 08:24 AM   #523
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Q: Can it have anything to do with the fact that the volume control and the source switch are mounted on a steel plate so it is that one that has to be grounded....??

......if you lay your hand on this steel plate, does the humming change? (better or worse?)
The steel plate is already connected to ground so that is not it either the problem. Tnx for the thought.

If I now don't get it right then the other solution is to apply a potentiometer/attenuator that I know is working so then my question is, do I think right when I want to apply this way, showing only one channel??

Potentiometer.jpg

And if the thought descriebed in the picture is correct that mean that I need to use a 4-gang potentiometer/attentuator to get both channels right and left, balanced all way to the output, or....??

I hope I am getting this right cause I am not shure but logic is saying yes.
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Old 16th April 2018, 09:00 AM   #524
Zen Mod is offline Zen Mod  Serbia
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picture is OK , and you need 4 gang for stereo
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Old 2nd June 2018, 01:59 PM   #525
TIC37 is offline TIC37  Sweden
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Default Finished

Ok I have finished it (for the moment)!!
Sound is very good and refined but I have just a small issue buggering me.

When I try to set the trimpots it is no problem getting the two channels within 1 or 2 mV AC of each other but when I set them I have about 640 mV over the 22R resistors and I can't get it down.
I saw earlier in the thread that 400-450 mV was to aim for but I can't get them there.

Then there is another thing I am wondering about. I have from my DAC appr. 1.850 V AC in to the preamp when playing a 1000 Hz testtone but the signal out from the preamp is only about 1.650 V AC out from the preamp, shouldn't I get some more gain??
If I try to go higher on the trimpots then I also raise the voltage over the 22R resister slightly going up to about 650 mV.

Anyone who have any idea??
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Last edited by TIC37; 2nd June 2018 at 02:01 PM. Reason: Clarification of AC voltage
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Old 2nd June 2018, 03:40 PM   #526
Zen Mod is offline Zen Mod  Serbia
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sorry , which one is ref. schematic ?
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Old 2nd June 2018, 04:05 PM   #527
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sorry , which one is ref. schematic ?
Original om Kojas board
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