Lightspeed Attenuator a new passive preamp

[udailey]

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.

[udailey]

Thats super cool software. What is it?

[redmaster]

Originally Posted by udailey

Thats super cool software. What is it?

that's RME digicheck,
you have to got RME interface I think....
it's amazing tool

[georgehifi]

Originally Posted by redmaster

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 ?

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

[redmaster]

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

[udailey]

You should compare the two. I can do the same test with metal film resistors and then replace with an LDR and get better sound. Still measures the same. This doesnt bother me because my ears are hearing something the equipment isnt showing me.

[udailey]

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.

[redmaster]

Originally Posted by udailey

You should compare the two. I can do the same test with metal film resistors and then replace with an LDR and get better sound. Still measures the same. This doesnt bother me because my ears are hearing something the equipment isnt showing me.

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

[georgehifi]

Originally Posted by redmaster

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

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

[udailey]

Originally Posted by redmaster

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

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