[Early B.]

For months, I've speculated that the sound is louder from my right speaker. I finally downloaded an SPL meter on my phone and measured each speaker. The right speaker is about 6 dB louder. I have no balance controls. How do I proceed to troubleshoot?

Thanks.

[JohnR]

Would help if you said what the rest of the equipment is what test gear you have (DVM? Signal generator on computer) but one simple (istic) way would be to swap left/right cables starting with the speaker cables and working backwards. Whereever the sound level difference doesn't change, the problem component is the one on the output end of the cables. (That's assuming it's not the cables that are the problem.)

[JohnR]

Whan I say swap left/right I don't mean swap the cables completely, just one end.

[Early B.]

Well, that was simple to diagnose. Thanks, John.

I swapped speaker cables and realized that one of my monoblocks is louder than the other. Now what do I do? 

[JohnR]

This is the Liberty Audio B2B 100s? If one is 6dB louder than the other, it suggests that the quieter one is not being driven by both "halves" of the signal. I suppose the obvious thing would be the mono/stereo switch on the back.

If that's not it, you have swapped L/R channels on the input cables to confirm it's the monoblocks? (NO change in level confirms that it's the monoblocks. Also, always have power off when doing cable swaps.)

A complete left-right swap of the monoblocks will confirm that they are indeed behaving differently. If that's the case then I'm not sure there's much to do except contact the manufacturer. [Edit] Actually I think I'd be inclined to take a DVM and measure for DC on the speaker outputs, juuust in case.]

[Early B.]

OK, I swapped the L/R channels on the input cables and confirmed that it's the monos.

[poseidonsvoice]

Early,

Interesting read, particularly that you had lived with this setup for a while before noticing the 6dB difference in output level. It’s amazing how we can second guess ourselves at times! Did you buy it used? Thanks to John for helping you figure it out. I don’t know if you are using that Liberty amp with the balanced inputs (with balanced XLR cables), so make sure the switch is set to BAL and other switch is set to MONO. If using balanced inputs I would suspect either pin 2 or 3 not making a perfect connection to the input board somewhere between the XLR jack and the board (A Fluke DVM, oscilloscope or oscillator would be handy, too bad I don’t live near you).  It is also interesting how low the input impedance of the balanced/XLR inputs are...3.6K ohms! Good thing you have the PBN preamp driving it!

The amp design in and of itself appears to be a classical MOSFET design with DC voltage regulation thrown in. I like how detailed their website is.

https://libertyaudio.com/service/b2b-100-all-mos-fet-stereo-power-amplifier/

Measurements (for those interested): https://www.soundstage.com/index.php?option=com_content&view=article&id=1113:bhk-labs-measurements-liberty-audio-b2b-100-stereo-mono-amplifier&catid=97&Itemid=154

Good luck!

Anand.

[rockadanny]

Bummer! I was worried about this sort of issue when I was putting my system together, whether the cause would be speaker, amp, preamp, CDP, my room, whatever. That is why I chose a preamp with separate L/R signal controls. My Mapletree Audio 2A/SE has a single overall volume control, but also separate L/R gain controls as well. And I am glad I did because, for whatever reason, one channel is slightly louder than the other, which was easily rectified by preamp settings. Of course, another solution would be mono-block amps with volume controls. Sorry, I realize this doesn't help your current configuration.



Best of luck in your pursuit! 

[Early B.]

I don’t know if you are using that Liberty amp with the balanced inputs (with balanced XLR cables), so make sure the switch is set to BAL and other switch is set to MONO. If using balanced inputs I would suspect either pin 2 or 3 not making a perfect connection to the input board somewhere between the XLR jack and the board (A Fluke DVM, oscilloscope or oscillator would be handy, too bad I don’t live near you).

Not sure if this could be the problem, so here goes -- I'm using the XLR jacks with adapters on both the preamp and amps because I have RCA cables. I'd love to replace those ICs with XLR cables someday.

[avahifi]

Normally, if you use RCA to XLR jack adaptors and you have balanced amplifiers that actually have two independent internal audio channels, then the RCA to XLR input converter plugs will only send a signal to only one of the the two internal channels resulting in 6 dB lower output and of course a large loss in power.

I note that the amp instructions say that you must have a full balanced output preamp with true balanced XLR jacks and cables at both ends to provide balanced high-power from each amplifier. 

Assuming this is true, I can't see how your connections would result in a gain 6db lower on one channel than the other unless something else is wrong.  Using RCA connections should result in both amplifiers using only one channel each and both having lower gain.

Frank

[poseidonsvoice]

Normally, if you use RCA to XLR jack adaptors and you have balanced amplifiers that actually have two independent internal audio channels, then the RCA to XLR input converter plugs will only send a signal to only one of the the two internal channels resulting in 6 dB lower output and of course a large loss in power.

I note that the amp instructions say that you must have a full balanced output preamp with true balanced XLR jacks and cables at both ends to provide balanced high-power from each amplifier. 

Assuming this is true, I can't see how your connections would result in a gain 6db lower on one channel than the other unless something else is wrong.  Using RCA connections should result in both amplifiers using only one channel each and both having lower gain.

Frank

Exactly. What Frank said. That being said...

EB,

Do you have a balanced source with XLR cables just to test? Isn’t your PBN Olympia pre a balanced design? What dac is connected to your PBN Olympia? Gustard? You don’t need fancy unobtanium XLR cables, just good old Canare/Mogami/Belden will do.

Alternatively, just use one monoblock, switch it back to “STEREO” and “RCA” and use that amp only with RCA cables. Then test the other monoblock.

Why do you need all that power for your speakers, assuming balanced/differential inputs and monoblocks?

Best,
Anand.

[Early B.]

Assuming this is true, I can't see how your connections would result in a gain 6db lower on one channel than the other unless something else is wrong.  Using RCA connections should result in both amplifiers using only one channel each and both having lower gain.

Yeah, there may be something wrong. I just ruled out the cables as the culprit. I had a pair of cheap XLR cables laying around and swapped those out. Same problem -- right speaker is louder than the left one. I've checked the settings on the amp several times and they're correct. I'm thinking it's one of the amps. I didn't have this problem until I got the second amp.


   

[Early B.]

Why do you need all that power for your speakers, assuming balanced/differential inputs and monoblocks?

I didn't buy the monos for the power -- I acquired them for the sound. I had one amp initially, but when I got the second one, the sound quality improved significantly. Going mono is worth every penny, in my opinion.

BTW -- I tested the second amp when I got it a few months ago. Both amps work fine as a stereo amp.
 

 

[poseidonsvoice]

I didn't buy the monos for the power -- I acquired them for the sound. I had one amp initially, but when I got the second one, the sound quality improved significantly. Going mono is worth every penny, in my opinion.

BTW -- I tested the second amp when I got it a few months ago. Both amps work fine as a stereo amp.

Then it’s back to the original premise. There might be something wrong with the XLR input circuitry (which could be a solder joint, failed component, etc...), given the evidence you have presented thus far.

Again, good luck! And let us know what else you discover...

Best,
Anand.

[OzarkTom]

Unbalanced sound drives me nuts. If this was my system, I would send both amps back to the manufacturer. If impossible, I would buy two of these. These are XLR's. You will find very little or no difference in sound.

https://www.amazon.com/Nobsound-Fully-Balanced-Single-Ended-Pre-Amplifier-Controller/dp/B01MXC9HHW/ref=asc_df_B01MXC9HHW/?tag=bingshoppinga-20&linkCode=df0&hvadid={creative}&hvpos={adposition}&hvnetw=o&hvrand={random}&hvpone=&hvptwo=&hvqmt=e&hvdev=c&hvdvcmdl={devicemodel}&hvlocint=&hvlocphy=&hvtargid=pla-4584345016300326&psc=1

 

[Early B.]

Problem solved. I spoke with the manufacturer and he walked me through the proper hook-up.

[poseidonsvoice]

Problem solved. I spoke with the manufacturer and he walked me through the proper hook-up.

Yippee!

Don’t leave us hanging on what the solution was!

Best,
Anand.

[Folsom]

Don’t leave us hanging on what the solution was!

^^^^