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Hafler pre amp
- Thread starter Jeremy64
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62vauxhall
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From owning a DH-110 for a bit, I learned that the transistors (J112 ?) in the muting circuit have somewhat of a reputation for failure.
There was cause for me to investigate because the power amp I had connected at the time, was producing a lot more heat on one channel than the other and this was occurring when both pre & power amps were just idling.
Since the power amp was known good, I measured for DC voltage at the DH-110's output jacks and found 6V present at one of them. After Google searching the symptom, obtaining & installing two new transistors, problem solved.
As a sidebar:
I came to acquire the 110 from trading a pair of speakers. The previous owner told me it had been gone through by a local tech I am acquainted with and implied some or all of the capacitors were replaced. The process of replacing those transistors revealed otherwise - absolutely all capacitors on the board were original. That pissed me off so I went ahead with a complete re-cap myself.
Once done, the DH-110 sounded to me "harsher" than it did before. So if you wind up with a DH-110, don't do a wholesale cap replacement "just because".
There was cause for me to investigate because the power amp I had connected at the time, was producing a lot more heat on one channel than the other and this was occurring when both pre & power amps were just idling.
Since the power amp was known good, I measured for DC voltage at the DH-110's output jacks and found 6V present at one of them. After Google searching the symptom, obtaining & installing two new transistors, problem solved.
As a sidebar:
I came to acquire the 110 from trading a pair of speakers. The previous owner told me it had been gone through by a local tech I am acquainted with and implied some or all of the capacitors were replaced. The process of replacing those transistors revealed otherwise - absolutely all capacitors on the board were original. That pissed me off so I went ahead with a complete re-cap myself.
Once done, the DH-110 sounded to me "harsher" than it did before. So if you wind up with a DH-110, don't do a wholesale cap replacement "just because".
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j112s are to mute on power up and power down. if the channel distorts or silences the channel you
can replace them - I normally use a socket at this time. you can run the 110 without the j112s.
my recaps sound better, depends on what caps you use. the last 110 I did used the Nichicon MUSE
ES green bipolar caps. sounded great. also let it burn in.
can replace them - I normally use a socket at this time. you can run the 110 without the j112s.
my recaps sound better, depends on what caps you use. the last 110 I did used the Nichicon MUSE
ES green bipolar caps. sounded great. also let it burn in.
