2. amps-preamps
  3. 191540-10159

Pass Labs XA30.5 Fuse Issue/Question

Hi all!

I recently acquired a Pass Labs XA30.5 from our friends at The Music Room and paired it with my Harbeth P3ESR speakers. It worked perfectly for about a week, delivering great sound with the needle hovering around 12 noon, even at high (to me) SPL. However, after a week, the fuse blew.

To get back to listening, I checked the back panel, purchased a set of 4A slow blow fuses (as labeled), and installed a fresh one. That’s when things started getting strange.

The unit powered on as usual, but as soon as I increased the volume to a moderate level, the needle swung wildly and pinned itself to the far right before the fuse blew again. I assumed it was just a bad fuse, so I replaced it with another. Same result. I tested the amp with a different set of speakers and a different source/preamp, but the same issue occurred every time.

I’m completely puzzled. It seems unlikely that all the replacement fuses are bad—could they be mislabeled? Does this pattern suggest any other potential issues?

I’ll reach out to Pass Labs if I can’t figure this out, but I wanted to check if anyone here has experienced something similar with their Pass equipment.

Thanks!

 

zm
jw944ts's avatar
jw944ts
325 posts
 

Pass labs is very user-friendly...do not hesitate to call them

baylinor's avatar
baylinor
1,413 posts
 

Sending it back to the music room for a full refund would be my only move. Done it before with zero issue as long as it's done within the return period. 

 

zm OP
121 posts
 

Thanks everyone for your responses! After learning the hard way in my early audiophile days, I’m super careful about avoiding shorts and triple checked all connections, so I don’t think that’s the culprit here.

@noromance, I think you zeroed in on something important - the amp is totally stable at low levels and will run indefinitely in that state. It only begins acting crazy when pushed to higher levels - your inference about a problem with one or more of the transistors coming online as power increases sounds very plausible!

@audphile1, the amp is connected to a Core Power Technologies Equi=Core 1800 conditioner.

I’ll be calling TMR today to get their read on the situation and sounds like the amp going back might be the most likely outcome. I appreciate everyone’s input.

curiousjim's avatar
curiousjim
4,689 posts
 

While Pass Labs are great to work with, calling TMR should definitely be your first step.  They are pretty good about this stuff and should pay for the return shipping as well.

All the best.

czarivey
5,946 posts
 

the output stage cannot generate sufficient current meaning that either power transistor replacement or filter caps or both.

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