Quote:
Originally Posted by aerius
Then seeing how getting rid of the small 22uf electrolytic capacitor in the power supply helped with noise, I thought to myself, what if I got rid of all the electrolytics and replaced them with film caps? Problem, I had to find some large film caps. So I went to check out the local surplus stores and found these things called motor run capacitors, and I did some research on them and found out they were actually large film caps. Bingo! I bought a few of them and stuck them into the power supply.
Result? Whoa, well, I got a lot more than I expected. Besides getting rid of almost every last bit of noise, the amp is now noticeably faster and more detailed, especially in the bass & lower midrange. Piano & electric bass notes which used to blend together are now distinct & separate, and I'm hearing details & textures in the bass which I've never heard before. I'd say the difference is almost as big as going from the Senn 600 to the 650 on a PPA, Gilmore Lite, or the previous version of my tube amp.
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what values did you get? any more details on this you can shed?
anyway, an update for me!!:
first, i replaced the tubes with ge tubes from ebay. well, they made a noticeable change. change to the good, i don't know. but i think i hear more detail (which is head-fi speak for it probably didn't do anythign).
next
i replaced all the resistors with vishay's (except for 4 koa spears since mouser didn't have vishay's with that particular value). i also replaced the 4 film caps with wima polyfilm. i then added the cap across the hv line and the 6 snubber caps for the filament line (both suggested by the siteswithstyle site). i also put a uf4007 on the dc+ line right after the bridge rectifier (i was too cheap to replace the whole bridge).
anyway, the sound was... much much much different afterwards. it lost the warm fuzzy feeling. i now have an amp that sounds much more forward, much more detailed. the mids are starting to lack a little, but the highs are strong and hard without any noise. the lows are... different. i'm not sure if it's better or not, but it's just different for now. The biggest difference i hear, though, is the soundstage. the soundstage for my k501's completely changed. with almost every source/amp i've tried the k501's on, i always hear the sound coming from behind me, like at the back of my head. now, it's froming from almost in FRONT. the vocals, though, come from front and up, like from my forehead. i don't know why, but it does. it's really weird. i believe the component upgrade has to be the absolute best $20 i've ever spent on this amp.
so the following is the list of mods i personally did:
pentode->triode
replace resistors with vishay dale mil grade
remove c1 and c4
replaced film caps with wima polyfilms
add a 5 ohm across both output signals (required, really)
doubled electrolytic cap values and put .33uf caps across those
put a .01uf monolithic cap across hv
put 6 1uf caps across the filament line
replace volume pot with stepped attenuator (with vishay dale rn60d's)
replaced tubes with ge tubes
shielded output and power transformers
put ultrafast uf4007 diode on dc+
emi filter on power line (i don't know if that does anything at all)