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Old 12th May 2008, 01:20 AM   #11
d3imlay is offline d3imlay  United States
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Default Re: What about their preamps

Quote:
Originally posted by GeeVee


I bought it, and now I am unsure if it is worth the effort to get it up and running.

Any thoughts???

Regards
George.
Before you pay some one to look at it, pull the covers and look for cracked solder joints on all of the boards and the mother board.
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Old 12th May 2008, 08:46 AM   #12
djk is offline djk
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"I am unsure if it is worth the effort to get it up and running."

The delay chip is no longer available.

The jacks are usually shot too, NLA. I suppose you could fabricate a board to mount new ones.

The 4136s are not so hot, and no pin-for-pin sub is available.

A while back I dumped a working one cheap.
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Old 12th May 2008, 09:54 AM   #13
d3imlay is offline d3imlay  United States
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Quote:
Originally posted by djk
"I am unsure if it is worth the effort to get it up and running."

The jacks are usually shot too, NLA. I suppose you could fabricate a board to mount new ones.

The 4136s are not so hot, and no pin-for-pin sub is available.

A while back I dumped a working one cheap.
The 4136 can be replaced by an adaptor board if necessary. Search for browndog 4136. The jacks are subject to cracked solder joints and break easy. They're ok if you insert the plug without side to side twisting.
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Old 13th May 2008, 02:21 PM   #14
GeeVee is offline GeeVee  Australia
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Default PL4000

Thanks for your comments djk, d3imlay.

Well the PL4000 is up and running, but it was not without its heartache and a lot of work.

The job was not helped by the fact that someone else must have tried to repair it before me, and made a mess of it.

This is what was required:

1.Clean all of the switches

2.Relpace the voulme pot (was completly shot), and also required some creative modifications.

3. Rebuild the power supply.

4. Replace over 40 electrolytics, including some matching for the delay.

5. Redo some wiring, including all of the 240V

6. Has 2 broken RCA jacks

7. Resolder countless joints, and repair some cracked tracks.

8. Stabilize from further damage lifted tracks.

9. Pull the entire face plate off and a good clean.

I have not hooked it up yet, but on the bench it appears to have a very clean wave on the scope, and no signs of anything abnormal, except for the joy stick control, which seems to balance across the diagonal rather than true side to side.

I will yet you know how it sounds when I hook it up this weekend.

Anyway, here is a pic of the final rebuild.

Regards

George.
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File Type: jpg pl4000.jpg (73.7 KB, 163 views)
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Old 14th May 2008, 11:30 AM   #15
GeeVee is offline GeeVee  Australia
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Default PL4000

Well

I could not wait untill the weekend, and managed to test the preamp tonight.

In summary, what a fantastic sounding preamp, and in particular, the phono stage.

I am very glad that I decided to fix er up, rather than ditch it.
However, it does have some rather unusual charecteristics.

1. Engaging the "correlator" - what ever that is, results in an immediate loss of treble, regardless of the setting. Best left off.

2. The Threshold control / PK expander control does not work well on pure acoustic and vocal recordings. Seems to have a pumping effect.
However, on material that has very fast, lower register attacks,such as a kick drum, the audio effect is quite good.

But after all of that, I simply defeated or turned off all of the whiz bag stuff.

In summary, suprisingly good, and well worth it, provided you can find one without paying too high a price.

Hope someone finds this usefull.

Regards
George.
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Old 14th May 2008, 12:28 PM   #16
AMV8 is offline AMV8  United Kingdom
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GeeVee

I have a PL 4000 and also Carver C 4000 pre amps.

If you have not met the "autocorrelator" before, here is how Bob Carver describes it...
"This circuit removes 8db of background noise from any source. It discriminates betweenwaveforms typical of music and random noise. It constantly compares and computes what can pass and what must be blocked over a wode range of frequencies..........You may sense a loss of highs even though we assure youthat frequency response is unaffected! This is due to psyco-accoustic affect where our hearing mechanism equates the presence of high frequency noise content with "definition/airiness" of the source. After you have lived with the autocorrelator for a while you will be offended by the noise you had endured before"

I hope this helps.

Don
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Old 14th May 2008, 02:01 PM   #17
GeeVee is offline GeeVee  Australia
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Default PL 4000

Hi Don

Thanks for your comments. That certainly is interesting.

The tests that I did tonight, were only fo about 2 hours, with 50% of the time spent with the preamp / system running as background music, to check that no problem developed after it had warmed up.

Therefor 1 hour of solid listening may not be enough to formulate and opinion on the autocorrelator.

Yes you are correct, there was an immediate reduction in the high frequency, so at the very least it would appear that the autocorrelator is opperating correctly.

I am not quite sure what to make of Mr Carver's statement. If our ears do equate this noise to "definition/airiness", then could this be a good thing?

After all, definition and airiness are qualities that I do look for.
But--- Perhaps my definition of airiness is not the same as Mr Carvers.

This is very interesting, and I will look into this further.

Once again, thanks for your comments.

I would be very interested to know what your personal thoughts are, since you own a PL 4000 also.

Regards
George.
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Old 14th May 2008, 04:41 PM   #18
AMV8 is offline AMV8  United Kingdom
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George

Initially I approached the "add ons" on the Phase linear 4000 and the Carver C4000 pre amps from a sceptical point of view. I took the view that if other "greats" in audio did not propose similar things they were probably just gimics from Bob Carver.

However after extended listening, I began to change my view. I think the autocorrelator works on some recordings; but not on others. I have found it most effective on "dirty" recordsand on some cd,s. I have not found it effective on "clean" records. I think you have to try it a few times on different sources and different recordings.

I find the Pl 4000 and the Carver C4000 surprisingly good to listen to. And, these amps were built in the 1970,s and 1980,s!

Don
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