A few weeks ago I had to substitute my Pass B1 and Aleph 4 with my trusted Arcam AVR280.
Unfortunately my Pearl 2 instantly destroyed the input ICs on the Arcam.
After a bit of investigation I found that the Pearl 2 outputs briefly swing to almost +24VDC on power on.
The B1 can cope with that.
The Aleph 4 has zeners on its input to protect it.
I'm just replacing my B1 with a P1.7 together with a RCA to XLR convertor, simply to be able to use balanced connectors.
I can't find anything on the THAT340P datasheet to tell me if the new pre-amp can survive the 24V pulse from the Pearl 2 ?
I've got a reverse zener input box that I can use but I'd rather not use it if I don't need it.
There is an error on the schematic for the pre-amp, it is powered with +/-20V not 30V as shown.
Unfortunately my Pearl 2 instantly destroyed the input ICs on the Arcam.
After a bit of investigation I found that the Pearl 2 outputs briefly swing to almost +24VDC on power on.
The B1 can cope with that.
The Aleph 4 has zeners on its input to protect it.
I'm just replacing my B1 with a P1.7 together with a RCA to XLR convertor, simply to be able to use balanced connectors.
I can't find anything on the THAT340P datasheet to tell me if the new pre-amp can survive the 24V pulse from the Pearl 2 ?
I've got a reverse zener input box that I can use but I'd rather not use it if I don't need it.
There is an error on the schematic for the pre-amp, it is powered with +/-20V not 30V as shown.
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Both channels are working but they both briefly produce an almost Vcc pulse.
The pulse only lasts for a brief half second or so.
The pulse only lasts for a brief half second or so.
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Do you have caps on the Pearl 2 output? Not sure how DC is getting through.
My Pearl 2 will put my AV receiver into protection mode on power up. I try to be careful to follow a power on sequence, TT>Phono Pre>Pre>Amp.
My Pearl 2 will put my AV receiver into protection mode on power up. I try to be careful to follow a power on sequence, TT>Phono Pre>Pre>Amp.
Yes the Pearl 2 has output caps but the DC pulse can still get through.
The Pearl 2 is built on two original Pass DIY boards with all the recommended components.
The PSU is remote.
The Pearl 2 is built on two original Pass DIY boards with all the recommended components.
The PSU is remote.
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I find it difficult to believe that the Pearl 2 is the cause of the problem as it has been working perfectly with the B1 and Aleph 4 for nearly 5 years.
Here's some discussion about the Pearl 2 burping/oinking on startup.
https://www.diyaudio.com/forums/pass-labs/204336-building-pearl-2-a-22.html#post5589303
Hi Mark, I concur with that thread. It is a simple case that one rail draws more than the other on startup.
Going back to my original question, can the THAT340P cope with that pulse ?
My PSU uses dual bridge rectifiers with a pretty huge 22000uF / rail power supply.
Going back to my original question, can the THAT340P cope with that pulse ?
My PSU uses dual bridge rectifiers with a pretty huge 22000uF / rail power supply.
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fix that first
either decrease output shunt resistor to,say, 10K or , if that not helps, install small delayed relay for output muting
either decrease output shunt resistor to,say, 10K or , if that not helps, install small delayed relay for output muting
I've built a buffer box with 1K resistors in series with the signal and reverse 9.1V zeners across the inputs. Exactly as implemented on the inputs of the Aleph 4. It works and does protect the inputs. But if I could do without it I would.
Hi Zen - that is perfectly true.
I've just clamped the inputs as per the Aleph 4
Two 1K0 resistors and 4 x 9V1 zeners.
I've just clamped the inputs as per the Aleph 4
Two 1K0 resistors and 4 x 9V1 zeners.
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This post is more an informational post about a slight design flaw in these otherwise incredible pre-amps.
Wouldn't all that be solved by turning on Pearl first, then pre? I don't know, my Pearl 2 has been hooked up to various preamps with no trouble. That said, I power Pearl, then pre, then power amp.
Russellc
Russellc
Pass DIY Addict
Joined 2000
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Yep, this is my protocol as well. Either power on the Pearl first, or make sure the input select is set to a non-Pearl input.
In one setup, I run the Pearl into the Korg pre, then to my MoFo. Powering the Pearl sends a surge into the MoFo that trips the protection of the laptop power brick that I use for the MoFo. That's when I figured out the protocol above 😉
The Arcam inputs were destroyed with it OFF.
I do turn on the Pearl 2 first.
The input selector chip is connected directly to the input sockets and has no protection against over-voltage on the inputs.
I do turn on the Pearl 2 first.
The input selector chip is connected directly to the input sockets and has no protection against over-voltage on the inputs.
Not to be difficult, but calling the Pearl 2 flawed in design is a bit much. No insult intended, but post seems to be informational on how to misuse Pearl 2, sorry.
I made mistake of powering Pearl 2 with pre and amp on, selector mistakenly on phono. Got an ugly snap, but no damage. That taught me what I already new...power on source, then pre, then amp. Or, in my case as another pointed out, with selector not set to phono.
Maybe I am misunderstanding the issue, but why would one power on a source selector is set to with pre and power amp on?
Hope your clamp solves problem, but I'm not seeing need, unless other users in home who don't understand turn on protocols?
Russellc
As I have already mentioned.
In the case of the Arcam, all inputs are permanently connected directly to the input selector IC.
It makes no difference if the amp is ON or OFF. The input selection is digital.
Unless you are in the habit of disconnecting all the source equipment before turning on the amplifier, which is a bad practice.
In the case of the Arcam, all inputs are permanently connected directly to the input selector IC.
It makes no difference if the amp is ON or OFF. The input selection is digital.
Unless you are in the habit of disconnecting all the source equipment before turning on the amplifier, which is a bad practice.
I can't imagine that the Arcam is the only device that uses this method of input selection.
OK, I accept that this might not be a unique problem of the Pearl 2.
This is supposed to be informative of a problem that can exist between two sources.
OK, I accept that this might not be a unique problem of the Pearl 2.
This is supposed to be informative of a problem that can exist between two sources.