Anyone contemplating building the Pearl 2 should be made aware of the following.
Don't get me wrong, it is a beautiful RIAA MC pre-amplifier but it does have one serious problem.
The O/P will swing to almost Vcc on power up. 24V DC was sufficient to kill my power amp input stage.
It is simply corrected by adding either a mute or a clamp at it's output.
I normally couple mine with an Aleph 4 which has these clamps at its inputs anyway. As the Aleph is currently faulty I decided to use it with my Arcam AV280 which unfortunately doesn't have the same protection.
Don't get me wrong, it is a beautiful RIAA MC pre-amplifier but it does have one serious problem.
The O/P will swing to almost Vcc on power up. 24V DC was sufficient to kill my power amp input stage.
It is simply corrected by adding either a mute or a clamp at it's output.
I normally couple mine with an Aleph 4 which has these clamps at its inputs anyway. As the Aleph is currently faulty I decided to use it with my Arcam AV280 which unfortunately doesn't have the same protection.
Why single out the Pearl?
Both really. Any device which produces large power on/off transients should be properly secured with an auto muting circuit. Analogue switches and chip VC ics should also be secured if directly connected to the inputs. It is amazing how many high end commercial devices have not been properly though out in this respect. Krell and ARC immediately come to mind.
Apparently the OP did turn on the Pearl 2 before the Arcam:
https://www.diyaudio.com/forums/solid-state/342299-hmm-ac-coupling-safe.html#post5905380
I'm wondering if the Arcam might actually by in stand-by mode when this happened.
Also some preamps that are 'on' when plugged in so it might be advisable to
add a relay to the Pearl 2 output?
https://www.diyaudio.com/forums/solid-state/342299-hmm-ac-coupling-safe.html#post5905380
I'm wondering if the Arcam might actually by in stand-by mode when this happened.
Also some preamps that are 'on' when plugged in so it might be advisable to
add a relay to the Pearl 2 output?
Here;s a graphic to show you what's going on. The output cap is going to hold its charge according to: e^-(t/RC)
You could clamp the output -- I haven't experienced the issue though since the AUX-IN of my preamplifier is capacitatively coupled. Try it and report back.
You could clamp the output -- I haven't experienced the issue though since the AUX-IN of my preamplifier is capacitatively coupled. Try it and report back.
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> You could clamp the output
Then why waste 95% of a good 24V rail to make only 0.6V peak output?? We could get that much out of a fresh AA cell. And hi-fi system levels often exceed 0.6V.
Turn-on thump is a real problem in some systems. I note that many mass-market chip-amps claim to have reduced it (by slow turn-on).
In this case I would *also* cast an eye at the following switching-stage which would not swallow a 24V pulse. That's big, but not hard to defend against. In "professional" work inputs are routinely defended against "any" voltage that might appear on stage or studio wires, even power-amp outputs. At line-level, another 10k in series is not a big deal, and 100V in 10k is 10mA, which most switch-chips will eat OK.
Then why waste 95% of a good 24V rail to make only 0.6V peak output?? We could get that much out of a fresh AA cell. And hi-fi system levels often exceed 0.6V.
Turn-on thump is a real problem in some systems. I note that many mass-market chip-amps claim to have reduced it (by slow turn-on).
In this case I would *also* cast an eye at the following switching-stage which would not swallow a 24V pulse. That's big, but not hard to defend against. In "professional" work inputs are routinely defended against "any" voltage that might appear on stage or studio wires, even power-amp outputs. At line-level, another 10k in series is not a big deal, and 100V in 10k is 10mA, which most switch-chips will eat OK.
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Precisely why I use a power conditioner with a delay function built in. The main reason is one button to turn on the system, and the key feature I wanted was this delay function. Phono and Preamp come on to warm up, then the power amps come on. Opposite for power-down sequence. I got a panamax unit on US AudioMart. Price was right and it had the functionality I was looking for. I'm sure it's one of many such products on the market.
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