Sep 12th, 2015
Concerning the Phase Linear 1000 noise reduction unit-I should probably make a complete understanding of the modifications and improvement done to the 1000. As an overview, the unit has audio crosstalk between channels, as well as, ground and hum problems because of design flaws in its power supply and circuit layout. This problem also affects to performance of the unit in subtle ways. My modification corrects the grounding power supply, improving the noise and fidelity. (In essence, I make a star/one point ground system so that no matter what other devices are hooked up to the in and outs, ground loops should not occur.)
More over, I do some changes in gain stages to improve the noise floor and more accurate channel to channels levels. Some of these modifications were advised by Phase Linear many years ago. Most units also have incorrect secondary power supply faults, the individual boards need some correction to reduce cross talk and oscillatory problems which cause some "fuzziness" to the audio when processing. And most importantly too is the fact the switches can be stubborn to clean although recently I have found a way to solve this. The main board and the plug in boards also develop cracks (every unit will have these problems which is often confused with claims of bad switches etc.)
The unit still does a great job of noise reduction and range expansion (which is much improved with the modifications) I also shield some areas and certain critical capacitors are upgraded. The unit still retains its same "tube-a-phonic" sound but all functions track more accurately. Replacement of a higher quality op amp is also a possibility to be done but strangely this does not dominate the greater problems, in fact the use of the 4136 op amp which is in general a poor performing op amp nonetheless, gives the audio a little of its "harmonically" enriched sound which seems to be preferred.
I've been modifying these units for twenty plus years and have come to realize many people want its sound character left intact but want to reduce the noise, poor channels separation, intermittent connectors and improved calibration of the enhancement effects is very audible and desirable.
At this point in time I can still do the modification and repairs for about $180-(if you ship in a good box) this includes all shipping and parts to return.