Lightspeed Attenuator a new passive preamp - Page 431 - diyAudio
Go Back   Home > Forums > Source & Line > Analog Line Level

Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 16th November 2011, 07:38 PM   #4301
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Georgehifi will sell you a light speed.
Udailey will sell you matched pairs of LDRs for a clone of the George creation or sell you matched pairs for his version of an LDR control.

But, most importantly, Read the Thread.
__________________
regards Andrew T.
  Reply With Quote
Old 16th November 2011, 11:41 PM   #4302
diyAudio Member
 
Join Date: Jun 2011
I did read it some time ago, but it won't help as I am not the person who built it
  Reply With Quote
Old 17th November 2011, 02:26 AM   #4303
diyAudio Member
 
georgehifi's Avatar
 
Join Date: Sep 2003
Location: Manly Australia (Jewel of the Pacific)
Send a message via MSN to georgehifi
Quote:
Originally Posted by redmaster View Post
If LDR design is not perfect and it's very difficult to find pair of LDR with 0.1dB difference - could you please advise me, what type of passive att. would be good ? - in a 'human - 99%' price range
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
__________________
Avatar : Production Lightspeed Attenuator
www.lightspeedattenuator.com
  Reply With Quote
Old 17th November 2011, 02:32 AM   #4304
udailey is offline udailey  United States
diyAudio Member
 
Join Date: Mar 2008
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.
__________________
purchase LDRs anytime Also try my Resistor Replacers or LDR based Input Selector Email me. diyldr@gmail.com

Last edited by udailey; 17th November 2011 at 02:36 AM.
  Reply With Quote
Old 17th November 2011, 02:59 AM   #4305
tinitus is offline tinitus  Europe
diyAudio Moderator R.I.P.
 
Join Date: Nov 2005
Quote:
Originally Posted by udailey View Post
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.
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
  Reply With Quote
Old 21st November 2011, 04:46 AM   #4306
diyAudio Member
 
Join Date: Jul 2003
Location: Dona paula, Goa
I will threadjack a bit, as this is Lightspeed related

I built a mute feature with the lightspeed using a relay, by shorting the shunt pot and opening the series pot, using a relay with one changeover contact.

This is for information of all, if u have any use for it.

Enjoy

Gajanan Phadte
  Reply With Quote
Old 21st November 2011, 01:10 PM   #4307
udailey is offline udailey  United States
diyAudio Member
 
Join Date: Mar 2008
Thats no threadjack! Thats great info for everyone. Thanks for sharing.
__________________
purchase LDRs anytime Also try my Resistor Replacers or LDR based Input Selector Email me. diyldr@gmail.com
  Reply With Quote
Old 21st November 2011, 01:19 PM   #4308
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
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.
__________________
regards Andrew T.
  Reply With Quote
Old 21st November 2011, 07:30 PM   #4309
diyAudio Member
 
Join Date: Jun 2011
Quote:
Originally Posted by georgehifi View Post
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
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
  Reply With Quote
Old 21st November 2011, 07:36 PM   #4310
diyAudio Member
 
Join Date: Jun 2011
Quote:
Originally Posted by udailey View Post
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.
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 ?
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



New To Site? Need Help?

All times are GMT. The time now is 03:26 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2