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"White Noise Head amp kit" - Page 46

post #676 of 682
sorry for reactivating this older monster-thread, but my questions are related to the mkI wna ha and i feel no longer comfortable posting them in the mkII-thread.

today i removed the input caps (c1) and jumpered j1 with 0,6mm² silvered copper wire. i got some serious cracking in the phones, when turning the pot (between ~10-2 o'clock). the recently recommended zobel net still is installed, i also grounded the pot. any ideas? should i use 0-ohm bridges for j1?
post #677 of 682
Thread Starter 
Quote:
Originally Posted by BrokenEnglish
sorry for reactivating this older monster-thread, but my questions are related to the mkI wna ha and i feel no longer comfortable posting them in the mkII-thread.

today i removed the input caps (c1) and jumpered j1 with 0,6mm² silvered copper wire. i got some serious cracking in the phones, when turning the pot (between ~10-2 o'clock). the recently recommended zobel net still is installed, i also grounded the pot. any ideas? should i use 0-ohm bridges for j1?
Hi Udo,

Are you totally sure that your source has output caps fitted? I think you should measure the DC offset from your source before removing the input caps on the WNA... if it's zero then fine, there should be no cracks in the phone and it's perfectly good to remove the caps from J1 and replace with wire jumpers..... if there is DC offset keep the caps in place.

Mike.
post #678 of 682
Quote:
Originally Posted by PinkFloyd
Hi Udo,

Are you totally sure that your source has output caps fitted? I think you should measure the DC offset from your source before removing the input caps on the WNA... if it's zero then fine, there should be no cracks in the phone and it's perfectly good to remove the caps from J1 and replace with wire jumpers..... if there is DC offset keep the caps in place.

Mike.
thanks, mike. i measured dc of my source before: 0,5 mV max; also i know that my (unmodded) emu0404 has output caps; also my second amp don't has input caps. cracking remains with or without signal. output dc = 0mV. i'll try zero ohm bridges now.
post #679 of 682
Thread Starter 
Quote:
Originally Posted by BrokenEnglish
thanks, mike. i measured dc of my source before: 0,5 mV max; also i know that my (unmodded) emu0404 has output caps; also my second amp don't has input caps. cracking remains with or without signal. output dc = 0mV. i'll try zero ohm bridges now.

Hi Udo,

report back after you try the zero ohm jumpers.

All the best.

Mike.
post #680 of 682
no effect with the zer-ohm bridges: cracking starting from ~12 o'clock, slight high pitched hum with max. volume. things are bettered, when i increase the distance from board to case-ground. a sort of oscillation?

ok.. malefactor detected: my uberized psu! ...i'm using an shielded cable from my psu to the amp, that most likely acted as an antenna for rfi. will switch that cable. no probs with my simpler psu. thanks again for your constant attention, mike!
post #681 of 682
Thread Starter 
Quote:
Originally Posted by BrokenEnglish
no effect with the zer-ohm bridges: cracking starting from ~12 o'clock, slight high pitched hum with max. volume. things are bettered, when i increase the distance from board to case-ground. a sort of oscillation?

ok.. malefactor detected: my uberized psu! ...i'm using an shielded cable from my psu to the amp, that most likely acted as an antenna for rfi. will switch that cable. no probs with my simpler psu. thanks again for your constant attention, mike!

hmm it doesn't seem to like that new PSU for some reason
post #682 of 682
more issues... it's better with the simpler psu, but it's not away: i measure some spikes of output voltage while turning the pot, max. 5mV, that go down to 0mV after few ms with constant pot-position... nothing to worry about, but not good at all... i guess, the lm6171 is still not tamed...

i rerouted some cabling, increased the pcb-bottom-distance... no effect.

i also tried upping the qc again and am still not happy with the result: i said, i missed some highs after my first trials... but that's not the truth. after more listening i'd say, there's a sort of drop in the upper mids with more qc. basses seem to be more powerful, but at the expense of poorer resolution. i'll go back to the former values (r5=120, r6=75).

removing the input caps produced a noticeably clearer sound... really lovely. i'll drop an email to david... maybe he'll find a way for some additional power-rail bypassing or bandwith limiting, as recommended by tangent. i'd definitely prefer to leave the input caps out.

hm... hmmm... hmmm... ... still love my wna... and i'll get, what i want! i'm just a step away... can feel it...
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