SanthoshA
Active Member
So the X11 is ready to rumble?
Same Q here. (Kinda)
Yes the X11, is ready and i had it running for couple of hours yesterday !.
All Bias and DC offset calibrations were re-done for the restored driver board.
Adjustments were a breeze with the multi turn trim pots, and i am so glad i replaced all of them.
The offset differences in AC voltage across the left and right channels, is now beyond my equipment's capacity to measure .
I have exactly the same AC voltage across the left channel and the right channel measured with a 1Khz sine wave. I am really happy as this issue got fixed during the restoration.
I am going to give it some time to break in post which i will post my listening impressions.
Overall , the differences are so huge that it cannot be compared to how it was sounding earlier before the restore. I would rather focus on how good the On Semi's sound compared to the original output transistors and probably do a RTA measurement of the speakers response apart from just providing my listening experiences/feedback.
I am planning to do two measurements, one with On Semi and the other with the NMA1718 and NMC1718 output transistors, i do not have a good set of speakers, i have some very old vintage speakers, and any signature change induced by transistors can or cannot be the same for each person.
Since i am using speakers as a reference, i believe we can only make out any peaks/dips in the frequency response graphs induced by changing transistors. To be frank i am also not sure if we will really see a difference in the frequency response with output transistor changes but i am just going to give this a try.
I am now building a dummy load to test the amplifiers full potential, i have the ARCOL Non-inductive resistors , but i lack a proper heat sink to do the tests, the resistor can hardly hold till 60watts without a proper heat sink.
A To-Do List:
1. Check For Oscillation in output (Bias and DC Offset Stabilization also)
Inspect sine wave across speaker terminals in the scope, and watch for distortion or clipping
2. Mount original output transistors
3. Fix PCB trace on one channel driver board
4. There is still a minor restore pending on of the smaller PCB's F-3454
5. Clean RCA sockets
I might do these points after doing the load tests(apart from point 1 as it is mandate for any load testing), i am trying to localise a heat sink if possible in my area, but it is quite challenging to source one for the load testing.
And the Metal Film upgrade is real worth the effort !