Phase Linear Model 2000 Series 2 Preamp restore/upgrade/etc

AZG

AZG

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Hi all,
Here is my PL 2000 Series 2 that I recently acquired. I have it paired with a Model 300 power amp along with a Model 1000 autocorrelator. The unit appears to be working just fine - all functions and controls work and the pots seem clean. The volume control is VERY sensitive and I typically do not bring it past 1/4 turn.

Modifications:
- RC4136 opamp upgrade to dual OPA2134 using BrownDog 060601 adapter


Issues/Questions:

1. Volume Bleed - tested only in phono stage, there is a volume bleed at 0 position on the volume knob.

2. Noise/Hum - there is both a hum and a hiss. the hum sounds like your typical 60hz hum and the hiss is more like soft static. both are significantly louder in phono stage (even when no phono input is connected), but present in all stages. noise increases as the volume is turned up.

3. Thud/Snap during On/Off - this is intermittent and does not always occur. "thud" during power on and "snap" during power off.

4. New AC wiring - the original 220v wiring was replaced with a 3 prong AC power cord (see photos)

5. Burn mark on input selector - not sure if this is an issue, but see photo


IMG_2075.jpg IMG_2077.jpg IMG_2085.jpg IMG_2081.jpg IMG_2080.jpg IMG_2079.jpg IMG_2078.jpg IMG_2083.jpg


Any thoughts?
 
62vauxhall

62vauxhall

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If by volume bleed do you mean there's still a bit of signal with the control all the way down? It may be the nature of that particular volume pot. I have a Hafler DH101 that does the same thing and I was convinced the pot was worn out. I consulted the "resident expert" at Musical Concepts who said it was normal. I happen to have an acquaintance who's had a DH101 and he told me his has done that since day1.

But the level is slight and I only noticed it while on the floor in front of the speakers. Maybe PL used the same part as Hafler?
 
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AZG

AZG

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fitz43 said:
Let us know how they work out.
Click to expand...

Will do. I just got my 2000 and 300 back from a local guy who did a recap on both units. He replaced the caps in the preamp with Elna Silmic IIs and the main outputs with Solen polys. Then in the amp, he used more Silmic IIs, some ClarityCap polys for a bypass and Nichicon's for the filter caps. He said that it will take about 70 hours for the caps to fully open up. I guess I'll just plug my ipod into the aux input and let it rip...way less work than tending to a record!
 
laatsch55

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On the op-amp swap from the 4739 to the 5532, it will probably oscillate. I tried most op-amps of that 5532 style in place of the 4739's, and in all cases I got an oscillation....
 
AZG

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laatsch55 said:
BTW, did you get the hum stopped?
Click to expand...
The hum is gone for all intents and purposes. If I crank the volume to way beyond practical listening levels, it is audible...but it is completely gone from the levels that I listen at.

Re: the oscillation, is that something that only shows up on a scope, or is it an actual audible thing?
 
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It does show up on a scope, I never tried to listen to it in that condition so I can't say it's audible. But I highly doubt an amp would love that kind of input...
 
AZG

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laatsch55 said:
It does show up on a scope, I never tried to listen to it in that condition so I can't say it's audible. But I highly doubt an amp would love that kind of input...
Click to expand...
So is the 4739 just THAT unique and nothing else can replicate its behavior?
 
laatsch55

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That was pretty much what was decided, I even had Joe on the project. It's how the phase lag/lead is treated in the 4739 compared to others, open loop gain was also a contributing factor.
 
AZG

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laatsch55 said:
That was pretty much what was decided, I even had Joe on the project. It's how the phase lag/lead is treated in the 4739 compared to others, open loop gain was also a contributing factor.
Click to expand...
Well damn. I guess I just wasted $30 haha
 
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Oh, if you could damage equipment doing it.......I would have managed that. Not having a scope does put a damper on that project.....
 
AZG

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laatsch55 said:
Oh, if you could damage equipment doing it.......I would have managed that. Not having a scope does put a damper on that project.....
Click to expand...
So I socketed the IC on the phono stage and then popped in the 5532 in place of the original 4739 and gave it a listen (no scope to actually test the output) and it sounded fine to me. I realize this isn't much of a test, but I have the unit ready to go whenever I find someone who can scope it for me. I went ahead and popped the 4739 back in and all is well.

On a separate note, I was reading some stuff about opamps and stumbled across this article (http://nwavguy.blogspot.com/2011/08/op-amp-measurements.html) and decided to try out some LM4562MA amps mounted to the browndog adapter in place of the 4136. I had been using the dual 2134s prior to this. I immediately noticed way more noise (hum) from the 4562s and then a very loud (hopefully not damaging) "thud" in my woofers when I disengage/engage the Tone controls on the preamp. Any thoughts on this? Is the dual 2134 the tried and true best guy for the job in place of the 4136?
 
wattsabundant

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AZG said:
So I socketed the IC on the phono stage and then popped in the 5532 in place of the original 4739 and gave it a listen (no scope to actually test the output) and it sounded fine to me. I realize this isn't much of a test, but I have the unit ready to go whenever I find someone who can scope it for me. I went ahead and popped the 4739 back in and all is well.

On a separate note, I was reading some stuff about opamps and stumbled across this article (http://nwavguy.blogspot.com/2011/08/op-amp-measurements.html) and decided to try out some LM4562MA amps mounted to the browndog adapter in place of the 4136. I had been using the dual 2134s prior to this. I immediately noticed way more noise (hum) from the 4562s and then a very loud (hopefully not damaging) "thud" in my woofers when I disengage/engage the Tone controls on the preamp. Any thoughts on this? Is the dual 2134 the tried and true best guy for the job in place of the 4136?
Click to expand...
The opamps should have decoupling caps on the power supply pins. A .1uf ceramic cap to ground is typical. The 4562's may be oscillating. The decoupling caps may solve that.

You really need to have a look on a scope.
 
AZG

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wattsabundant said:
The opamps should have decoupling caps on the power supply pins. A .1uf ceramic cap to ground is typical. The 4562's may be oscillating. The decoupling caps may solve that.

You really need to have a look on a scope.
Click to expand...
Are you saying no matter which opamps are used, there should be a decoupling cap between the V+ and ground (what about V- to ground?) or is it just in the case of the 4562?
 
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Any op-amp. Check.out my 3300 ser II threads, good pics of that process on the backside of the board. I used wima poly pro caps...
 
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