Greetings Fred:
I was a Sansui sales representative from the mid '70s to mid '80s and am very familiar with the AU-X1. What you said about it being "too sophisticated for its own good" is about as right-on as anything. The main problem had to do, oddly enough, with its "Super Feedforward" design, which was its main selling point. Since the SSF circuit was very stable in the AU-919, the engineers decided to try overkill in the creation of the X1. It was the unit's extremely high slew rate that caused it to oscillate at just about the drop of a hat, which always resulted in the output transistors going up in smoke. I found out the hard way that just about anything could trigger the unit into oscillation, including RF interference, connection to a speaker comparator, thin gauge or "resistive" speaker wire (this amp really NEEDED Monster Cable or Live Wire to work best; forget about "zip" cord) or even a speaker system with a less-than-flat (read that "easy") impedence curve. I also found out that one must NEVER power the unit up without speakers connected; it would blow up. Usually, leaving a headphone plugged in would prevent this from happening. When it did work, however rarely that might be, it sounded GREAT and was certainly the best transistorized integrated amp that ever came out of Japan (did A-B comparisons against the top Pioneer, Kenwood, Technics and Onkyo integrated units of the time; the only unit that came close was the AU-919 running in "bypass" mode). It was during one of these comparison tests that one of my associates decided to buy an X1. A couple of years and four sets of output transistors later, he sold the unit. He felt it was too unreliable. From the repair angle, my technician absolutely HATED the X1. According to him, each of the six demo units that we were running had blown up at least twice (this is where we discovered all the "don'ts" about this amp) and some as many as four times. He was glad that we did not sell that many units but did average an X1 every other month (for the same reason!).
I hope this helps. As repair parts are becoming increasingly difficult to find for the X1, I would recommend that you consider selling yours (assuming it still works) and, if you are still partial to the sound of Sansui amps of that era, consider getting an AU-919 (still quite a few floating around eBay). When a 919 is run in the "bypass" mode (a front panel switch), it is one of the sweetest sounding amps and closely rivals the X1, without all the trouble. It does significantly reduce the power (if memory serves, it bypassed the entire line stage and fed the power amp directly) but you will be rewarded with exceptional sound AND reliabilty.
If I may be any further assistance, please email me.
Sincerely,
I was a Sansui sales representative from the mid '70s to mid '80s and am very familiar with the AU-X1. What you said about it being "too sophisticated for its own good" is about as right-on as anything. The main problem had to do, oddly enough, with its "Super Feedforward" design, which was its main selling point. Since the SSF circuit was very stable in the AU-919, the engineers decided to try overkill in the creation of the X1. It was the unit's extremely high slew rate that caused it to oscillate at just about the drop of a hat, which always resulted in the output transistors going up in smoke. I found out the hard way that just about anything could trigger the unit into oscillation, including RF interference, connection to a speaker comparator, thin gauge or "resistive" speaker wire (this amp really NEEDED Monster Cable or Live Wire to work best; forget about "zip" cord) or even a speaker system with a less-than-flat (read that "easy") impedence curve. I also found out that one must NEVER power the unit up without speakers connected; it would blow up. Usually, leaving a headphone plugged in would prevent this from happening. When it did work, however rarely that might be, it sounded GREAT and was certainly the best transistorized integrated amp that ever came out of Japan (did A-B comparisons against the top Pioneer, Kenwood, Technics and Onkyo integrated units of the time; the only unit that came close was the AU-919 running in "bypass" mode). It was during one of these comparison tests that one of my associates decided to buy an X1. A couple of years and four sets of output transistors later, he sold the unit. He felt it was too unreliable. From the repair angle, my technician absolutely HATED the X1. According to him, each of the six demo units that we were running had blown up at least twice (this is where we discovered all the "don'ts" about this amp) and some as many as four times. He was glad that we did not sell that many units but did average an X1 every other month (for the same reason!).
I hope this helps. As repair parts are becoming increasingly difficult to find for the X1, I would recommend that you consider selling yours (assuming it still works) and, if you are still partial to the sound of Sansui amps of that era, consider getting an AU-919 (still quite a few floating around eBay). When a 919 is run in the "bypass" mode (a front panel switch), it is one of the sweetest sounding amps and closely rivals the X1, without all the trouble. It does significantly reduce the power (if memory serves, it bypassed the entire line stage and fed the power amp directly) but you will be rewarded with exceptional sound AND reliabilty.
If I may be any further assistance, please email me.
Sincerely,