Red if you can hear .1dB or even 1db difference in channel balance on a Lightspeed, you are definately Superman. The best speakers cannot get anywhere near that.
The production Lightspeed Attenuator is within + - 1db and I have never had anyone with a problem in over 6 years of doing them, but then they are not Superman either.
What you need is volume control done in the digital domain before the dac, perfect channel balance as the recording engineer wanted you to hear it. But then you will probally get bit stripping if not more than 75% of full output.
Cheers George
Redmaster
Your LDRs are either not matched or somehow damaged. You need to either get or match your own LDRs OR you can fix what you have.
To fix it you will turn the volume up all the way. Put a 1k trimmer in series with the power going to the LED side of the LDR that has the lowest resistance. Trim them into balance. Then turn the volume down all the way and find the channel that has the lowest resistance. Put a 100k trimmer from the positive side of the LED power to 0V and trim down until the LDR has a value similar to the other.
On both solutions we are only correcting the series LDRs. You might have the shunts out of whack so just measuring resistance might not do it for you. You may have to trim both of these trimmers while you listen so that you get the stereo image in the center.
If you cant manage this you can send it to me and I can adjust it or just stick new LDRs in it for you.
Going with an ALPS when you have this beauty so close to working right is a shame. The ALPS has no chance against a Lightspeed.
Uriah
ps I agree with George that .1dB is just a goal that can hardly be achieved. Even the ALPS has a +/-10% channel balance, maybe 5% if lucky.
Your LDRs are either not matched or somehow damaged. You need to either get or match your own LDRs OR you can fix what you have.
To fix it you will turn the volume up all the way. Put a 1k trimmer in series with the power going to the LED side of the LDR that has the lowest resistance. Trim them into balance. Then turn the volume down all the way and find the channel that has the lowest resistance. Put a 100k trimmer from the positive side of the LED power to 0V and trim down until the LDR has a value similar to the other.
On both solutions we are only correcting the series LDRs. You might have the shunts out of whack so just measuring resistance might not do it for you. You may have to trim both of these trimmers while you listen so that you get the stereo image in the center.
If you cant manage this you can send it to me and I can adjust it or just stick new LDRs in it for you.
Going with an ALPS when you have this beauty so close to working right is a shame. The ALPS has no chance against a Lightspeed.
Uriah
ps I agree with George that .1dB is just a goal that can hardly be achieved. Even the ALPS has a +/-10% channel balance, maybe 5% if lucky.
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0.1db is surely not audible
but 1db might be
I clearly hear 1db on my balance adjustment
maybe for different reasons I dont know about
but I would think it depends on what you are used to
like if you have been used to +1db in one channel
and suddenly have -1db in opposite
such change is surely audible
regarding ALPS, is that measured, or from spec sheet ?
many xo components I have measured have often been much more accurate than the specs imply
byw, it would be very audible if you have early frequency rolloff in one channel
use a double pole double throw (dpdt) relay and use the other changeover contacts to reduce the currents through the LEDs.
This could be used to protect the LED/LDR from long term deterioration if left in the max or min volume by accident.
Invoke the Mute at power off. Use the Play to delay signal transmission at start up.
Now that extra contact in the signal route has a benefit.
This could be used to protect the LED/LDR from long term deterioration if left in the max or min volume by accident.
Invoke the Mute at power off. Use the Play to delay signal transmission at start up.
Now that extra contact in the signal route has a benefit.
no I can't here 0.1 dB, but I can hear 0.5dB very well
only in my studio, acoustically treated room helps a lot;
but I need up to 0.2dB, if it's possible with this design.
what about a 2 separate Left and Right volume knobs with precise vu metering ?
so you just turn up both knobs and you can see if both channels are even
do you think it's a good idea ?
thanks for input gents,
the thing is I'm not a great with soldering iron (well I managed to solder all cables at my studio, but that's it) and I don't understand yours technical 'jargon' ...
shame as the gentleman who built it for me gave up project and I need someone badly to help me..
if any of you live in UK or EU, are happy to help me- you are more then welcome
here is a video file,
LDR l+r imbalance - YouTube
please note how it starts from imbalance, get even in the 'middle' around -20dBFS, and then starts getting imbalance again, but now another channel is louder
I am happy to have 0.2dB, but if it's 1dB difference - then in my situation it's not good
do you think 2 separate ldr volume pots and precise VU meter could be an option ?
Yes for sure you can do this a wonderful job with 2 Volume pots. It can be perfect matched voltage output from the two channels. Their total resistance might be a bit different but you will have what you wanted. Most folks complain about adjusting even one pot LOL so two pots doesnt come up often.
Even matched tweeters from B&W for their 801's monitors are within +- 1db that's 2db spread overhaul, as stated to me by B&W when I owned a pair that needed them replaced when one blew.
If you have a detectable shift difference in image while music is playing at different levels, then it's bigger than .5db, also what you have shown to me indicates not a good quad matched set at 5 different mA points, from 1 to 20mA
Yes if you want to fix this problem without having to rematch your set, (you may have unmatched them with too much heat while soldering) you can use dual left and right 100k single pots, as I do offer this as an option in the production Lightspeed Attenuator for those who have system/speaker or room imbalance problems.
But I also state in the Lightspeed advertising pdf that it is more user unfriendly as they (the two separate pots) take time to get balanced when different cd levels are used and volume is changed.
Cheers George
I am really passionate about 'transparency' of ldr's audio,
I read on another forum ppl talked about passive attenuators, someone mentioned atty a design, the 1in 1 out passive attenuator as being completely transparent. Transparent means - you record output of device and then swap phase 180 and sum it with original file - if it nulls - means 100% transparent - you can always say you can hear difference, but null test doesn't lie
I am interested about yours opinion
I read on another forum ppl talked about passive attenuators, someone mentioned atty a design, the 1in 1 out passive attenuator as being completely transparent. Transparent means - you record output of device and then swap phase 180 and sum it with original file - if it nulls - means 100% transparent - you can always say you can hear difference, but null test doesn't lie
I am interested about yours opinion
Oh, by the way I did this recently and am publishing a little project about it on diyaudioprojects.com
I want them to get to release the tiny circuit but then I will link here so you guys can check it out. Its not the biggest deal in the world but I replaced a resistor in my amp with a LDR and the difference was not small. Replaced a PRP.
I want them to get to release the tiny circuit but then I will link here so you guys can check it out. Its not the biggest deal in the world but I replaced a resistor in my amp with a LDR and the difference was not small. Replaced a PRP.
null testing is not about measuring,
you swap phase 180 degrees and add to original file, when it nulls - means it's identical, and your ears/brain 'hear' something which does not exist,
null test is very efficient way to judge audio
When I've talked about the transparency of the Lightspeed Attenuator having the least sonic signature (true to the source) of any preamp.
It's compared to direct connection into a poweramp from the source. Any other preamp passive or active has a far greater sonic signature than the Lightspeed with this way of comparing.
All volume pots switched or resistive track sound different as they all have a lightweight wiper contact (diode effect) of varying degrees, this is why if you clean and tighten your rca plugs your sound changes usually for the better, the wiper in a volume pot is even worse for this as it is a very small area of very light pressure when compared to an rca plug, and the diode effect is trying to rectify the ac music signal especially during heavy transients.
The Lightspeed is so close to a direct connection, it is almost undetectable when A/Bing. I still believe that direct connection is the perfect way of staying true to the source, but you do need a digital volume control in the cdp/dac done in the digital domain before the dac chip and to be able to use it in the top 20% of the full output range, otherwise you do run the risk of bit stripping if below 20% of full output.
Cheers George
I understand what you are saying now. I wonder if we did something like this with a .1% SS amp and a .1% tube amp if we would hear the warmth of tubes left over.
Uriah