Musical Fidelity X-P100 Pre-amp issue - HELP NEEDED!

Roddw1

Standard Member
Greatly appreciate any help/input/advice form any forum members familiar with the mystifying problem below:-

Been the proud owner of both the MF X-P100 pre and X-AS100 power amp for years now and trust me when I say that when used in tandem they really do sing. Just got them back from a local & highly reputable engineer as I was getting a lot of scratching on the input channel switch selector on the pre and nothing output from the right channel of the power amp. All is now working noiselessly BUT I now have a further issue in the sense that ONE channel is now outputting to the speakers at a lower volume to the other. Engineer has been back and we've tried all the obvious things such as checking for faulty cables, swapping speaker & preamp inputs from R to L etc but problem is still there. If I change from R to L the lower output changes in tandem and the issue remains irrespective of what input channel is selected. The mind boggling thing is that both channels work it's just that one is doing so at approx 50% volume. Engineer is convinced it's an issue with the Pre-amp but at this stage both of us are totally stumped.

Anyone ever come across an issue like this with MF or any other pre/power combo - where all seems to be working perfectly but one channel is outputting to the speakers at near twice the power?
 

RBZ5416

Distinguished Member
Engineer seems a lofty title for someone who returned the items with a fault & now can't isolate it.

Just take a 3.5mm jack to phono cable from a phone/tablet/PC straight into the power amp with the volume of the source at zero. Increase the volume of the source device until you have a reasonable level. If the fault's still there it's the power amp & if not, the pre.
 

Roddw1

Standard Member
Thanks. He's serviced/repaired a lot of my kit and to be fair this was a house visit today to see if it was something obvious. I could try the above once I get a 3.5mm/phono (thanks again) but it is not an output problem as such (the amp is outputting sound to both speakers) it's just noticeably unbalanced (i.e. left audibly louder than right and vice versa if I reverse speaker connections).
 

RBZ5416

Distinguished Member
If you don't have a 3.5mm cable just swap the inputs to the power amp. If the fault switches sides it's the pre & if not it's the power.
 

Paul7777x

Well-known Member
If it is the preamp, I can only suggest you check the j-fet outputs (If I remember correctly).

Or get in touch with MF for a replacement set.
 

Roddw1

Standard Member
If it is the preamp, I can only suggest you check the j-fet outputs (If I remember correctly).

Or get in touch with MF for a replacement set.
Thanks - no idea what a j-fet output is but definitely worth trying! The mystery here is that if some component goes then you'd think the output on that channel would go also, but in this case it hasn't, it's just weakened.
 

RBZ5416

Distinguished Member
The manual makes no reference to a balance control so I guess it doesn't have one. But is the volume maybe one of those split controls?
 

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