[platinum]

Hi it's been quite a bit since my last visit.
 
 
I am having a problem with my BX5a. My DAC was sent to be fixed (used balanced XLR usually), and won't come back anytime soon.
Last night I tried to hook up the same RCA-TRS cable I used (before I switch to XLR) to the output of 1212m 0202 sound card, with a RCA female->TRS male adaptor.
One speaker gave a very loud bang and the blue LED went off. It sounded like the speaker is blown. Fact is one of the fuse in the speaker blown.
The other one worked well till a few hours ago. I connected the remaining BX5a to the TV with the RCA-TRS mentioned above. Fuse blown.
 
Then I went to buy some T2A fuse to replace those in the speakers. The blue LED came back on, both speakers. I don't have other devices that use XLR as output so I kept trying different unbalanced source and cables. Fuse blown, the story goes on.
 
I almost came to the conclusion that the BX5a is defective, or at least the TRS input part. But what do others think? How likely are the XLR input are still alive?
 
Capacitors inside looks good.
OPAMP are JRC 4580, are they the trouble maker?
the amps are TDA 2052 with mute function. possible that the amp came back from 'idle' after plugging in the cable, and something went wrong?

 

[Ham Sandwich]

What cable are you using?  Do you have a picture or a link for the same cable?
 
I've never seen a RCA to TRS (or TRS to RCA) cable.  It makes no sense.  You can find TRS to dual RCA cables but that's the wrong cable for your application and that particular TRS is for a stereo input/output not balanced input/output.
 
What you want is a TS to RCA cable.  TS is Tip Sleeve.  TRS is Tip Ring Sleeve.
 
Or you can use a TS to RCA adapter plugged in the BX5a and use a regular RCA cable.
 
I don't know what RCA jack you're plugging in to.  The 1212M has a pair of balanced TRS inputs and a pair of balanced TRS outputs.  There is no RCA audio jack.
 
The cable you want is a pair of TRS to TRS cables.  Connect the balanced output of the 1212M to the balanced input on the BX5a.

 

[platinum]

Thanks for your reply.
I guess i mixed all those terminology up, let me clarify:
 
I have a RCA-TS cable, with the adapter it can be a TS-TS cable. I think I have the exact same adaptor as in the link you posted.
 
I have used the cable itself for signal from unbalanced RCA sources on these speakers (i.e. TV and DAC), they worked before.
one of my speaker died on connecting the cable+adaptor to the 1212M a few days ago (fuse blew). while the other one worked.
then the other day I connected the other speaker to the RCA output of the TV (without the adaptor), this speaker died as well.
 
I played with other RCA-RCA cables+adaptor (i.e. now RCA-TS), the fuse in the speaker blew.
so I think both speakers will die on anything connected to it's TS/TRS terminal.
any thoughts?

 

[ccbass]

I'm lost as hell.  Assuming you're that 0202 card, you STILL have balanced outputs.
 
Before you were using XLR to TRS cables for each channel from your DAC to your BX5a's.  Instead of going from your DAC to your speakers, you're going directly from the 0202 to your speakers. 
 
NOW.
 
That 0202 outputs L/R in two balanced TRS outputs. 
 
You need EITHER:
 
TWO TRS to XLR cables.
or
TWO TRS to TRS cables.
 
 
Without trying to decode everything you're saying, I believe what you ended up doing is shorting the circuit and that caused the fuse to blow.   

 

[Ham Sandwich]

I took a quick look at the manual for the 1212M.  It doesn't look like the TRS inputs/outputs are auto-sensing based on using a TS or TRS plug.  You have to manually set their level (-10 dBV for consumer, +4 dBu for professional) in the driver.
 
If the output level in the driver is set to +4 dBu and you're using the TS to RCA adapter to convert to unbalanced you could be overdriving the signal and causing the amp in the BX5a speakers to clip badly and that may possibly be causing the fuse to blow.  Maybe.

 

[platinum]

Thank you for your reply.Problem solved:i changed all opamps then things goes well. going from 4580D to LM4562 is a pretty big upgrade as well.