Pearl 2 Crackling on Left Channel

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hirscwi

hirscwi

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Joined 2014
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I have a Pearl 2 phono preamp that I built 4 or 5 years ago. It has been working fine until yesterday. Now I am getting a crackling or static sound from the left channel with certain higher notes (for example a flute). The remainder of the music is unaffected but the crackling sits on top of the music and is intermittent (related to higher frequency notes). The right channel is fine. If I swap the Pearl 2 for another phono preamp, all is well - so it must be the Pearl 2.

I really like the Pearl but have no idea where to start troubleshooting this problem. Any suggestions will be greatly appreciated.
 
hirscwi

hirscwi

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Joined 2014
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Problem Is Back - with a Vengence

The problem is back and more severe.

By chance I tried to set the DC to zero using P1. It is not stable. It will jump from negative .7vDC (not millivolts) to positive 1.0 v with no adjustment. That's as close to zero as it gets.

I don't completely understand this circuit but am wondering if the Q2 (ZVP3310) is bad as I've read they are not reliable.
 
hirscwi

hirscwi

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Joined 2014
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I replaced the ZVP3310 along with the CCS (Q10 and Q11 - ZTX450). It seems to be working just fine now.

I do have a question about zeroing the DC at the test point (using P1). The closest I can get to 0 is about 25mV and it sometimes climbs to 200 mV after a few minutes. Is this normal? I am measuring with the cartridge connected to the circuit.

Thanks for the assistance.
 
codyt

codyt

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Joined 2019
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I recall that being normal when I built mine. I did end up putting a bit of capacitance in series with R14, which keeps offset rock solid.

hirscwi said:
I replaced the ZVP3310 along with the CCS (Q10 and Q11 - ZTX450). It seems to be working just fine now.

I do have a question about zeroing the DC at the test point (using P1). The closest I can get to 0 is about 25mV and it sometimes climbs to 200 mV after a few minutes. Is this normal? I am measuring with the cartridge connected to the circuit.

Thanks for the assistance.
Click to expand...
 
M

mymindinside

Member
Joined 2007
Hirscwi, what precautions did you take to keep the ZVP3310 ESD safe while installing it?
I'm starting on my Pearl2 and dont want to fry mine while stuffing the boards..

One method i've seen recommended is to short the gate pin to source (with foil or a clip). I do have a wrist strap but am not sure where to connect it on my workbench, don't have an accessible ground point.

Just in case, i do have some spares...
 
Super_BQ

Super_BQ

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Joined 2001
hirscwi said:
For what it's worth, I had to replace both ZVP3310s because I was getting quite a bit more gain from the right channel after replacing the ZVP3310 on the left channel. Must have been different gain codes?
Click to expand...

After uncovering my Penultimate Zen (aka Zen v4) monoblocs. I've discovered 1 channel is also louder than the other. It's quite noticeable with Klipschorns. The affected amp also seems to show little mid-range sound.

Will double check if the cables could be the source of the problem because i'm not keen on unsoldering all the TO-247 IRF transistors (3 per board x 2 as i'm running 2 boards per channel in balanced mode).

I do know the Zen v4 uses the same ZVP3110 and ZTX450 transistors. I have plenty of spares for which they were purchased around the same time I built these monoblocs (circa 2002).
 
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