Hi there
I've just made a complete **** out of myself and am a bit ashamed about it. Yet it is such a folly a have to tell.
Last week i finally got my dad to let me 'modify' his marantz pm78 amp. I have done his cdp, got him to recone his ar3a1 speakers so this was a start for the final stroke (he wants me to build him a tube amp).
I did nothing special to the amp. I changed the single poor and most important opamp for a 2134 and put in some bypasses and extra capacitance for the preamp psu.
After a few days i got the impression the mods had been succesfull. Yet when we sat down to listen tonight i noticed some strange sound in the left loudspeaker. there was something rattling, a coil scraping a magnet, osccilation or ringing.
Hence i started to check all connections, buttons and settings but nothing was found. So i started to ponder the possible consequences of my mods.
Maybe the change in opamp had shifted dc levels and reverse biased or blown an couling cap? maybe i had a bad soldering joint or cracked one? maybe the psu changes had caused ringing or oscillation?
After a few mindcrunching hours we sat down to listen and analyze the strange sound again when my dad had an inspiration.
He removed the christmas cookie jarr me mum had placed upon the speaker. Gone was the sound!
Damn those christmas ornament loving women and their cookie jarrs! It was the cookies rattling around, how could i've missed this!
Still feeling a bit embarrased
regards
Joris
I've just made a complete **** out of myself and am a bit ashamed about it. Yet it is such a folly a have to tell.
Last week i finally got my dad to let me 'modify' his marantz pm78 amp. I have done his cdp, got him to recone his ar3a1 speakers so this was a start for the final stroke (he wants me to build him a tube amp).
I did nothing special to the amp. I changed the single poor and most important opamp for a 2134 and put in some bypasses and extra capacitance for the preamp psu.
After a few days i got the impression the mods had been succesfull. Yet when we sat down to listen tonight i noticed some strange sound in the left loudspeaker. there was something rattling, a coil scraping a magnet, osccilation or ringing.
Hence i started to check all connections, buttons and settings but nothing was found. So i started to ponder the possible consequences of my mods.
Maybe the change in opamp had shifted dc levels and reverse biased or blown an couling cap? maybe i had a bad soldering joint or cracked one? maybe the psu changes had caused ringing or oscillation?
After a few mindcrunching hours we sat down to listen and analyze the strange sound again when my dad had an inspiration.
He removed the christmas cookie jarr me mum had placed upon the speaker. Gone was the sound!
Damn those christmas ornament loving women and their cookie jarrs! It was the cookies rattling around, how could i've missed this!
Still feeling a bit embarrased
regards
Joris
Banned
Joined 2002
Jazz Im dealing with the same thing. In this free subwoofer i have i have fixed it and put in a new plate amp its a cheap little thing a 8" woofer and a 50 x 2 watt amp inside with a external electronic crossover. any way there are so many little holes o the back of this plate amp i hear all of them and it ****es me off yes the box is ported but i still hear every little squeak ****es me off to because its like right there in my face * par say * so a new box i believe is the answer with a separate enclosed area for the subwoofer plate amp.. i hope..
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