01-01-2012, 01:05 PM
let me explain how i first came to be interested in this subject.
about 15 years ago a guy came to the shop with a beam echo advantic integrated amp that was very distorted on one chanel with one el84 glowing red.this was caused by one of the hunts 0.1mf coupling caps going very leaky, this was changed along with the one from the other half of the output stage useing grey radio spares ones, as the glowing valve had suffered it was changed for a pinical el84. the amp was checked using a pair of old music centre speakers.no distortion so amp was collected only to come back a week later with the complaint that the left and right chanels sounded different.useing the same workshop setup i could hear no difference.so i went up to the guys house to hear for my self ,the difference was suttle but there,after swapping the speakers and the inputs over to make sure it was the amp i agreed to have another look. back in the workshop i hooked the amp up to an audio gen and a scope across a 10 ohm dummy load,monertering both channels and reeding both sine and squar waves at 1kc/10ks and16kc i could see no difference, so i phoned my father who has built valve amps as a hobby for years,he told me the obvious in a push pull amp output valves should allway be a matched pair and in a stereo amp in matched quads so out came the pinical and in went a pair of mullards.back to the coustomer sounded better but could still hear a difference so back to shop as the only other thing i had done was the coupling caps so in went four 0.1mf mullarad mustards,amp returned .about 10 days latter was askes to go up there again this time he was happy and said both channels now sounded the sameand if anything he was hearing more in the music than befor he was happy to pay the £30 bill and i learned that valves and caps have there own sound. i may start a thread about hifi myths and facts
rob t
ps i dont know why caps sound different but they do
about 15 years ago a guy came to the shop with a beam echo advantic integrated amp that was very distorted on one chanel with one el84 glowing red.this was caused by one of the hunts 0.1mf coupling caps going very leaky, this was changed along with the one from the other half of the output stage useing grey radio spares ones, as the glowing valve had suffered it was changed for a pinical el84. the amp was checked using a pair of old music centre speakers.no distortion so amp was collected only to come back a week later with the complaint that the left and right chanels sounded different.useing the same workshop setup i could hear no difference.so i went up to the guys house to hear for my self ,the difference was suttle but there,after swapping the speakers and the inputs over to make sure it was the amp i agreed to have another look. back in the workshop i hooked the amp up to an audio gen and a scope across a 10 ohm dummy load,monertering both channels and reeding both sine and squar waves at 1kc/10ks and16kc i could see no difference, so i phoned my father who has built valve amps as a hobby for years,he told me the obvious in a push pull amp output valves should allway be a matched pair and in a stereo amp in matched quads so out came the pinical and in went a pair of mullards.back to the coustomer sounded better but could still hear a difference so back to shop as the only other thing i had done was the coupling caps so in went four 0.1mf mullarad mustards,amp returned .about 10 days latter was askes to go up there again this time he was happy and said both channels now sounded the sameand if anything he was hearing more in the music than befor he was happy to pay the £30 bill and i learned that valves and caps have there own sound. i may start a thread about hifi myths and facts
rob t
ps i dont know why caps sound different but they do
if its made by hand it can be repaired by hand
