Suitable replacement for BX63A?

[DerekTheGreat]

Hello everyone!

I suspect the subwoofer output of my BX63A is going south. I've got some testing to do, but wanted some food for thought in the event there is something wrong with it. I stumbled upon this doofrad called "Mini DSP." (https://www.minidsp.com/products/min...minidsp-2x4-hd) Boasts quite an array of features and it seems like a nice replacement for the BX63A in my system. What do you folks think? Would you folks recommend something else?

Backstory: I've sent in a Crown PS-400 for service once and then again for warranty work as it was still exhibiting the same fault. Their tech says nothing is wrong with it despite vigorous testing. It was sent in for service because channel two would begin to fade out over time. I'd see the IOC light get dim and also feel decreased output from the associated subwoofer. I felt that since I was using a "Y" splitter on the subwoofer output, there was no way it was the BX63A. I even swapped the input cable from channel 1 to channel 2 with no change. Out of curiosity/frustration, I plopped my SR-II amplifier in place. Problem solved- equal output out of the amplifier and subwoofers. Well, fast-forward to last week when I noticed channel 1 on the SR-II fading out and then receiving the PS-400 & paperwork stating they could not find a problem with it. I'm really going to feel sheepish if testing reveals there is indeed nothing wrong with that PS-400....

[Riley Casey]

While the MiniDSP is certainly very capable if you want to stick with analog the circuitry in the B63 is much more 'repairable' than a Crown amp. Might give that a try first.

[rusty jefferson]

Derek, I can't conceive of a way that you would be getting varied output from one side of the 'y' connectors.

.... I even swapped the input cable from channel 1 to channel 2 with no change....

I'm not sure what this means. Are you running 1 amp in stereo, and if so, when you reverse the inputs into either amplifier does the weaker signal move from left to right (or vise versa) or not? Is one of the subs always weaker no matter which channel of the amplifier is feeding it?

[DerekTheGreat]

While the MiniDSP is certainly very capable if you want to stick with analog the circuitry in the B63 is much more 'repairable' than a Crown amp. Might give that a try first.

Hi Riley,

Not necessarily. My turntable is the only analog source I've got. I wouldn't mind keeping the BX63A, but if (big if..) it needs repair, that's beyond my capabilities. Would you happen to know anyone who would be willing to repair it?

Derek, I can't conceive of a way that you would be getting varied output from one side of the 'y' connectors.

I'm not sure what this means. Are you running 1 amp in stereo, and if so, when you reverse the inputs into either amplifier does the weaker signal move from left to right (or vise versa) or not? Is one of the subs always weaker no matter which channel of the amplifier is feeding it?

That's what I think too. How the hell would that be possible? What I meant when I swapped each channel was exactly what you said, the cable that WAS feeding channel one got swapped over to two and vice versa. The result was the problem didn't move, channel 2 was still weak. The amp was running in stereo. When I sent it in for service, I put the Crown SR-II I had in it's place. Now that amp is weak on channel 1. Meanwhile, these guys have looked at the amp twice and told me nothing was wrong with it. Before I sent the PS-400 back in, I fed it with the Adcom GFP-555 I've still got hanging around and played it for about four hours. It was hooked up in a different room. No issues with it in that room. However, when I hooked it up to the SL-1/BX63A, it began to get weak on the one channel again. Which of course lead me to send it back in for warranty work.

[Possibly] Interesting note about the SR-II's weak channel: I noticed the signal strength indicators weren't equal between each channel some three weeks ago, left being weak. So too was the output from the left subwoofer. I turned up the volume on the preamp and all of a sudden the signal was equal between the two again. Things were fine up until the other day where now it is weak at all times. Haven't had time to investigate it. Worth noting that the output from the 813C's is equal between left and right.

[rusty jefferson]

So it sounds like both legs of the 'y' have driven 1 channel of the amplifiers fine, but both legs also demonstrated weakness in the other channel that did not go away when the input was changed. Is that right?

I'd try removing the 'y' and plugging one cable into the crossover and into the good channel. Play that 1 sub long enough to verify it's working well. Then turn the amps off and move the input to the other channel and see how that works with the other channel. If/when the problem arises switch the speaker connections on the amplifier and repeat the above. This should help determine if it's the crossover, a bad connection, a bad sub, or an amplifier problem.

[Ian Mackenzie]

Have you looked at the pre amp and your cables?


Can you describe how you have the signal path wired up from the pre amp to the input of the power amps ?

What’s the Y connector for? If for some reason the Y connector poses a low impedance to the BX63A this may potentially cause an intermittent fault. Or if the Y connector or a faulty cable shorting the output of the BX63A.

There is really nothing to fail or go wrong in the BX63A with the exception of the electrolytic coupling caps on the sub outputs.

Are you using the sub out in bridge mode?

[rusty jefferson]

...What’s the Y connector for?

The 'y' connector is the output of the BX63A crossover feeding a summed mono signal to a 2 channel amplifier for a pair of subwoofers.

[Robh3606]

Did you make sure the potentiometers are not the issue with the BX-63A??? Could be as simple as that. I had a issue with mine once and it was the pots.

Rob

[Ian Mackenzie]

The 'y' connector is the output of the BX63A crossover feeding a summed mono signal to a 2 channel amplifier for a pair of subwoofers.

Okay. That being the case l wonder what the input impedance of each channel is and if the power amp has input level controls?

[Ian Mackenzie]

Did you make sure the potentiometers are not the issue with the BX-63A??? Could be as simple as that. I had a issue with mine once and it was the pots.

Rob

That’s a possibility. An old or worn pot track could cause this kind of problem.

[rusty jefferson]

I've had both issues with both the potentiometer and the failing power supply capacitors in the BX63A. That unit was professionally rebuilt for me a few years ago with quality parts. I don't believe the crossover output could be fine on one leg of the 'y' and problematic on the other leg. When I had those issues many years ago it showed itself on both channels simultaneously.

I think it's advisable to check as I described, both amplifier channels and subwoofers independently from a single output without the 'y' and see if the problem presents itself. It could be a bad connection, cable, amplifier, sub/driver, or least likely (I think) the crossover. My 2 cents.

[Ian Mackenzie]

I don’t believe it’s clear what the problem is and therefore the cause. It’s easy to interpret a fault incorrectly.

Pots are normal either on or off if the tracks are worn.

Capacitor however if leakage is present can play up. If the value went down it would account for less bass output. Two amp inputs halves the input impedance and that raises the -3 db time constant of the capacitor. If that cap it bad a parallel connection will only make it worse. If it’s the power supply cap then the active parts of the circuit may not function correctly.

It’s a simple service issue for s tech with an oscilloscope.

[rusty jefferson]

I give up.

Derek, you can call me to help troubleshoot this if you don't get it worked out here.

[Robh3606]

Exercise every switch in the crossover. Load, in and out ect. I have had channels drop out and be intermittent from a dirty mute switch so look simple first.

Are you using the 1/4 plugs on the PS-400 Try rotating them to see if you hear noise. If you do power down and plug and unplug and rotate to clean the contacts. Had one channel drop in level dirty contacts in the 1/4 plug.

Rob

[grumpy]

More fun:
Also possible to use both BX63A sub outputs (to get the Y out of the variables). just swap the sub's speaker lead (plus to minus or red to black) on amp channel connected to the BX63's "-" output channel.

Faulty speaker (e.g., voice coil), or loose-ish connection in it's cabinet (terminal panel to driver)?

Certainly tough diagnosing via email.