Bigdrive
Active Member
I have just finished a "garage comparison" A/B test of 2 717's and to me the results were surprising.
The contender's……
A restored 717 (my third one following lees stereo guide) thank you sir for that guide I have always loved the results. I change all the 726's and most transistors on the preamp. Main power supply caps also had to be changed. All push buttons, speaker controls and preamp switch at the back completely disassembled and ultrasonically cleaned. Bournes 3296 25 turn trimmers installed. Put on a scope and tested and adjusted to spec. Ran for 40 hours and is ready to be given back to my sister.
The other, is a newly purchased 717 for myself (I really like the sound). I was able to see the unit before purchase and it would be a 9.5 out of 10, almost a museum piece. Its like it was put into a plastic bag for the last 25 years. The rca's are all like new. Inside it has a medium amount of dust but all the screws were even torque and no paint mark scrapes from a screw driver or old lines of multiple screw marks on the metal. This unit has not been opened up before. The power cord is soft and the white line on the cable is white and the cable tie clear and new looking. Inside all the small wire bundle plastic ties are clear and in the proper original spots. No signs of nicotine at all. Glue is still present and all caps are original. This to me is a untouched unopened 717. Unit was scoped and adjusted to spec. It was identified at this time the balance pot requires cleaning, but was not done. a quick check on the load bank for power and it made rated power without clipping.
Set-up.....
Computer to DAC that was split going to each AUX input on both machines. Speaker A on both units going to my A/off/B switch with its output going to Polk ati9 (still under warranty). Volumes matched with clicks counted. Room is 15x12. Speakers are symmetrically placed and listen position within the triangle and dead center.
Testers...…
My wife and I. 59 years old. My hearing good to 11,000hz and my wife's good to 13,000hz.
Now for the results...…
This is what I would call a garage test as it was not in a lab or strictly controlled. We tested 5 songs that we know well and was not over any length of time. We did try and change the songs by what we were hearing and we did discuss the out come at the end of each song. I knew which amp was which but my wife did not all she heard was the click of a switch. Sometimes during a song I would switch at will and other times I told her to call it when she wanted a switch. She sat in the sweet spot, I did not.
Overall, they sounded the same! Sometimes the Lees was clearer up near the middle freqs if there was little other music but if there was lots of music it was the other way around. Bass sometimes was better with lees and sometimes it was the same. At the end of the test it was even, meaning on a full blind test I would not be able to tell which one was which. To me that is surprising, but to others I am sure they are saying "well you did good, its not suppose to sound different"....and to us it did not. A quick note, I follow Ben and all his work and have the greatest respect for his work and great posts. I think if you want it to sound the best possible, send it to lees stereo!
I always wanted to do this so I posted my opinion and it is not meant as a change the caps or not thing as that's been worked to death. My new unit will have the caps replaced and the glue removed and I will follow lees guide.
Cheers,
The contender's……
A restored 717 (my third one following lees stereo guide) thank you sir for that guide I have always loved the results. I change all the 726's and most transistors on the preamp. Main power supply caps also had to be changed. All push buttons, speaker controls and preamp switch at the back completely disassembled and ultrasonically cleaned. Bournes 3296 25 turn trimmers installed. Put on a scope and tested and adjusted to spec. Ran for 40 hours and is ready to be given back to my sister.
The other, is a newly purchased 717 for myself (I really like the sound). I was able to see the unit before purchase and it would be a 9.5 out of 10, almost a museum piece. Its like it was put into a plastic bag for the last 25 years. The rca's are all like new. Inside it has a medium amount of dust but all the screws were even torque and no paint mark scrapes from a screw driver or old lines of multiple screw marks on the metal. This unit has not been opened up before. The power cord is soft and the white line on the cable is white and the cable tie clear and new looking. Inside all the small wire bundle plastic ties are clear and in the proper original spots. No signs of nicotine at all. Glue is still present and all caps are original. This to me is a untouched unopened 717. Unit was scoped and adjusted to spec. It was identified at this time the balance pot requires cleaning, but was not done. a quick check on the load bank for power and it made rated power without clipping.
Set-up.....
Computer to DAC that was split going to each AUX input on both machines. Speaker A on both units going to my A/off/B switch with its output going to Polk ati9 (still under warranty). Volumes matched with clicks counted. Room is 15x12. Speakers are symmetrically placed and listen position within the triangle and dead center.
Testers...…
My wife and I. 59 years old. My hearing good to 11,000hz and my wife's good to 13,000hz.
Now for the results...…
This is what I would call a garage test as it was not in a lab or strictly controlled. We tested 5 songs that we know well and was not over any length of time. We did try and change the songs by what we were hearing and we did discuss the out come at the end of each song. I knew which amp was which but my wife did not all she heard was the click of a switch. Sometimes during a song I would switch at will and other times I told her to call it when she wanted a switch. She sat in the sweet spot, I did not.
Overall, they sounded the same! Sometimes the Lees was clearer up near the middle freqs if there was little other music but if there was lots of music it was the other way around. Bass sometimes was better with lees and sometimes it was the same. At the end of the test it was even, meaning on a full blind test I would not be able to tell which one was which. To me that is surprising, but to others I am sure they are saying "well you did good, its not suppose to sound different"....and to us it did not. A quick note, I follow Ben and all his work and have the greatest respect for his work and great posts. I think if you want it to sound the best possible, send it to lees stereo!
I always wanted to do this so I posted my opinion and it is not meant as a change the caps or not thing as that's been worked to death. My new unit will have the caps replaced and the glue removed and I will follow lees guide.
Cheers,
- when judging amps, we might simply not hear improvements at the very very top.