Balance problem that I cannot solve

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glynnw

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Balance problem that I cannot solve
« on: 17 Aug 2019, 07:01 pm »
 Using LDR3X Rev 2.F - I am having a balance problem, similar to one I had a year or two ago.  The balance moves from right to left as the volume increases. Problem still there when I switched to different input impedances so I stuck with 20 ohms, where I get the loudest signal.  I have a couple of spare LDR modules, which I think are good.  I followed the procedure that worked last time - replacing the left shunt LDR, running recalibration, and playing music.  This didn't fix it.  Next I switched that "good" LDR to the right shunt, ran recalibration and then again the problem wasn't fixed.  I pulled from my closet of cool crap an older Tortuga preamp (too old to have a number on the board - no switchable LDRs) and it worked fine - no balance issues.    If I simply buy 4 new LDRs and put them in, should this solve the problem?  Meanwhile this older unit sounds great and I even have 2 remotes for it.

Warpspeed CE

Re: Balance problem that I cannot solve
« Reply #1 on: 17 Aug 2019, 11:45 pm »
Hopefully the Tortuga does not fall victim to its own complexity...

RDavidson

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Re: Balance problem that I cannot solve
« Reply #2 on: 18 Aug 2019, 01:59 am »
Hopefully the Tortuga does not fall victim to its own complexity...

Is this comment coming from the maker of the Warpspeed LDR preamp?

tortugaranger

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Re: Balance problem that I cannot solve
« Reply #3 on: 19 Aug 2019, 07:01 pm »
Hopefully the Tortuga does not fall victim to its own complexity...


Are you concerned?

tortugaranger

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Re: Balance problem that I cannot solve
« Reply #4 on: 19 Aug 2019, 07:08 pm »
Using LDR3X Rev 2.F - I am having a balance problem, similar to one I had a year or two ago.  The balance moves from right to left as the volume increases. Problem still there when I switched to different input impedances so I stuck with 20 ohms, where I get the loudest signal.  I have a couple of spare LDR modules, which I think are good.  I followed the procedure that worked last time - replacing the left shunt LDR, running recalibration, and playing music.  This didn't fix it.  Next I switched that "good" LDR to the right shunt, ran recalibration and then again the problem wasn't fixed.  I pulled from my closet of cool crap an older Tortuga preamp (too old to have a number on the board - no switchable LDRs) and it worked fine - no balance issues.    If I simply buy 4 new LDRs and put them in, should this solve the problem?  Meanwhile this older unit sounds great and I even have 2 remotes for it.


Hi Glynn,

Sorry for the delay in responding....chock a block weekend and on the road all day today. The only explanations that fit are either there are 2 LDRs out of spec on one channel (both the shunt and series) or that each channel has a bad LDR (could be shunt or series).  I just now saw where you ordered a full set (4) of replacements. That should take care of it. At this stage in the evolution of these LDR controller/attenuators the calibration feature works very reliably with any 4 LDRs that are reasonably within spec.

Cheers,
Morten

glynnw

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Re: Balance problem that I cannot solve
« Reply #5 on: 20 Aug 2019, 12:52 am »
chock a block weekend and on the road my eye---I bet you were out sailing.   Thanks for the followup.  I can't wait to get this fixed and move on.  The old unit sounds OK, but just seems to lack some of the refinement the newer board supplies with its ability to be tailored to my system a bit.

tortugaranger

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Re: Balance problem that I cannot solve
« Reply #6 on: 20 Aug 2019, 12:40 pm »
chock a block weekend and on the road my eye---I bet you were out sailing.


Ha! I wish. The reality was all day Saturday and Sunday hanging drywall in kitchen etc. as part of a major home remodel project that has now lasted what seems like every weekend going back into infinity.

Tubeburner

Re: Balance problem that I cannot solve
« Reply #7 on: 31 Aug 2019, 02:48 pm »
glynnw, did the LDR's fix the problem?

tortugaranger

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Re: Balance problem that I cannot solve
« Reply #8 on: 31 Aug 2019, 08:48 pm »
glynnw, did the LDR's fix the problem?


He wrote me saying it did resolve the balance problem. If you have no obvious balance problem but are just experiencing an overall drop in volume it's conceivable it's the LDRs but that would be highly unusual. You mentioned you had to cal each time before using it. What is happening before you run cal and what does running cal change?

Tubeburner

Re: Balance problem that I cannot solve
« Reply #9 on: 31 Aug 2019, 08:54 pm »
Morten, my volume is very low. Running Cal was fixing this problem, but the Cal is not fixing this issue any longer. Volume is very low, thin sound. I assume one LDR has gone bad, but how do I tell? The numbers during the Cal are there, I just don't know what I should look for.

tortugaranger

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Re: Balance problem that I cannot solve
« Reply #10 on: 31 Aug 2019, 09:20 pm »
Morten, my volume is very low. Running Cal was fixing this problem, but the Cal is not fixing this issue any longer. Volume is very low, thin sound. I assume one LDR has gone bad, but how do I tell? The numbers during the Cal are there, I just don't know what I should look for.


I can send you a set of LDRs and you can swap them out and see if that resolves the problem. It's unusual for both channels to have a bad LDR at the same time but it's possible and would account for both channels being low on volume.

Tubeburner

Re: Balance problem that I cannot solve
« Reply #11 on: 31 Aug 2019, 09:23 pm »
Yes, please send me a set and I'll put them in. Thank you.

tortugaranger

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Re: Balance problem that I cannot solve
« Reply #12 on: 1 Sep 2019, 01:46 pm »
While this is nothing new, it's worth repeating that LDRs can drift and sometimes go out of spec. Most do not. Some do. It's been my experience that most LDRs will last indefinitely and that a small subset will go bad. Most that go bad do so early on  (first few weeks) although some can fail after a few months.

We deliberately design our LDR based preamp products with removable plug-in LDR modules and built-in LDR calibration. That way, should an LDR go bad, it's a relatively simple matter of opening up the unit, plucking out 1 or 2 LDRs, plugging in new ones, running a calibration cycle (~10 minutes), and you're back in business.  You don't need matched LDRs in our preamps. The calibration feature adjusts individual LDR attenuation tables to account for the differences between each LDR's performance and thus normalizes their behavior as though they're all inherently exactly the same.

The most reliable way to tell if an LDR has gone bad is to recognize when volume balance has shifted substantially left or right and/or when one channel stops responding to volume changes. In an extreme case where both left and right channels both have a bad LDR (very rare in my view) the overall volume level may be substantially reduced and the sound quality noticeably degraded. Replacing 1 or more LDRs (4 total) will typically resolve this.

More info on identifying and replacing a bad LDR can be found here in our on line product documentation. https://www.tortugaaudio.com/support/product-documentation/?section=ldr-replacement-instructions