This One has Me Confused

[KEM]

I recently purchased a Pass XP-12 to replace my aging ML 38s. After installation, I noticed gobs of high frequency distortion, especially in Operatic female voices.

I measured every component in the signal chain separately. All are performing in spec. The XP-12 has very impressive test results. I use a Benchmark A/D and RTA (real time analysis) software as well as REW.

Re-installing the 38s gets me immediately back to more mellow sound.

In my system, I have an EQ and crossover between the XP-12 and my Bryston 2.5b^3 power amp. I removed the EQ and the XO, plugging the XP-12 directly into the power amp. The distortion remains.

I am puzzled. I am a measurement guy. I use REW extensively. I can measure and troubleshoot almost any problem in my system. This one is a stumper.

Can anybody suggest a measurement or a way to solve this apparent component mismatch?



My system in order from source to output :

Shelter 901 MKIII MC or Koetsu RS MC cartridges

Parasound Zphono XRM phono preamp

Technics SL-1200G TT

Oppo BDP-105 Universal player (digital)

Bryston BDA-3 D/A ( feeds the Oppo signal to the XP-12 or 38s)

Sansui TU-X1 tuner

XP-12 (38s) line amp

dBx 1231 EQ

Rane AC22 2 way crossover

Bryston 2.5B^3 power amp

Usher 604 floorstanding speakers

HSU ULS-15 sub (when using the XO)



Thanks,

Kevin

 

[terryforsythe]

Is it possible it is defective?

 

[kemmler3D]

Broken / defective would be my guess also. THD is spec'd at 0.001 (percent? Doesn't say) but either way it shouldn't be obvious. Unless it has some insane rise in distortion with frequency (unlikely even for a Pass product) I'd say you should look into a warranty claim.