Lightspeed Attenuator a new passive preamp - Page 418 - 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 20th June 2011, 07:46 PM   #4171
udailey is offline udailey  United States
diyAudio Member
 
Join Date: Mar 2008
I dont think that auto cal on 0VAC will work very well. Theoretically yeah. However, it has to work for more than just a few people. For instance I use JRiver. Each song melds into the next so there is never 0VAC. Okay thats just for me and a handful of JRiver users. The other problem would be that I think the calibration would take a minimum of 5 to 10 seconds to be decent and maybe a bit longer to be good enough for balanced if it were a balanced circuit. Take an LDR up to 10k and watch it waiver and thats why it will take a while. If the circuit averaged the values it got for a few seconds then acted on that value.. This wouldnt matter for single ended very much but for balanced it would matter a lot.
While I was eating lunch I thought about this.. what if we have a reference channel. So either L or R or one line of one balanced channel is hard set, meaning that we dial those values in or match those 2 LDRs real well, like with the previous trimmer idea. Then everything else must conform to the voltages we get out of those 2 LDRs...?
So we could either match or go by a 12-24 step volume increase for one shunt and one series LDR. Then the circuit could try to force the other channel, if single ended, or the other 3 if balanced... to match the reference LDRs.
OR perhaps even easier we could do the real great matching on one pair of LDRs for series and create this circuit to assume that the series are matched and it will then force the shunts to be 'value X' that will output a voltage equal on both channels!!
Still, for balanced you could do the trimmered 12-24 step volume adjustment for the series LDRs and then this circuit to force shunts to output the same voltage on each.
__________________
purchase LDRs anytime Also try my Resistor Replacers or LDR based Input Selector Email me. diyldr@gmail.com
  Reply With Quote
Old 21st June 2011, 12:09 AM   #4172
diyAudio Member
 
georgehifi's Avatar
 
Join Date: Sep 2003
Location: Manly Australia (Jewel of the Pacific)
Send a message via MSN to georgehifi
I commissioned an expert/friend on this way back, one thing that can't be done without introducing extra distortions is an auto calibrating system that monitors the resistances of all NSL's and keeps them equal for balance/ channel balance purposes.
What can be done without introducing anything, is a semi auto calibration arrangement where at the beginning of listening at a pre set volume a cal set button is pressed and this calibrates all the NSL's for correct balance, trouble with this is it has to be done every time the volume is changed.
1: You start the track pick your volume you want listen at.
2: Stop the track press the auto cal button.
3: Then start the track again and then listen.
As you can see this only hooks up the auto cal sensing circuit while not listening and the resistances, then removes it when you are ready to listen.

But who would want to live with this, best off just quad matching your NSL's and KISS

Cheers George
__________________
Avatar : Production Lightspeed Attenuator
www.lightspeedattenuator.com
  Reply With Quote
Old 21st June 2011, 03:56 AM   #4173
diyAudio Member
 
kstlfido's Avatar
 
Join Date: Mar 2006
Location: Berkeley, CA
Been lurking as usual!

I still use my Maximus' lightspeed. Still working fine and still not in a box!

This balance issue has been w/ my lightspeed since day 1. As I turn up the volume, the image shifts to the right slightly.

I had an idea; a more passive approach (and I like the use of old meters), using an old balance meter (pointer rests in a vertical state). Feed voltages (decoupled somehow) from the Dallas pot chips to the meter.

Meter starts in center position at 0 volume, no deflection.

Play source white noise or music. Then turn up the volume and adjust balance to center image. Take note on meter deflection (either by it's scale or mark my own scale). Repeat for different steps of volume. Sort of crude, but could work and look rather cool!

I have no idea how to implement this yet. Just a thought.. and my 2c!

Cheers- Kent
  Reply With Quote
Old 21st June 2011, 03:58 AM   #4174
diyAudio Member
 
Join Date: Jul 2003
Location: Dona paula, Goa
the switched 4way could have 400r for both series LDRs elements and 200r for both shunt LDR elements.
But I would not connect that equivalent 600r load to my sources.
__________________
regards Andrew T.

The above situation is a result of hasty reply and will never occur with a quad pot.

All u need is a preset across each pot except one, with which the LDRs will be calibrated.

Enjoy

Gajanan Phadte

Note:in this configuration, both the volume controls will have same value of Z and NOT balanced output for both channels.

Last edited by gmphadte; 21st June 2011 at 04:06 AM.
  Reply With Quote
Old 21st June 2011, 04:15 AM   #4175
diyAudio Member
 
georgehifi's Avatar
 
Join Date: Sep 2003
Location: Manly Australia (Jewel of the Pacific)
Send a message via MSN to georgehifi
Your preset idea works at a predetermined level, but when that's changed so too will all the presets have to be re-aligned, as the 4 x NSL's are all different in their mA to resistance curves no 2 are the same.
It is still best to quad match as I've outlined for a KISS approach, why complicate things without having any advancement in sound quality.

Cheers George
__________________
Avatar : Production Lightspeed Attenuator
www.lightspeedattenuator.com
  Reply With Quote
Old 21st June 2011, 09:26 AM   #4176
DRONE7 is offline DRONE7  New Zealand
diyAudio Member
 
Join Date: Aug 2008
Quote:
Originally Posted by georgehifi View Post
It is still best to quad match as I've outlined for a KISS approach, why complicate things without having any advancement in sound quality.

Cheers George
With you all the way here George !

Young people these days, never heard of Occam or his beard removal device.
  Reply With Quote
Old 21st June 2011, 09:36 AM   #4177
diyAudio Member
 
Join Date: Jul 2003
Location: Dona paula, Goa
Young at 51.
What a complement.
  Reply With Quote
Old 21st June 2011, 09:44 AM   #4178
diyAudio Member
 
Join Date: May 2011
Location: NY
This is my fist to learn it. I would like to thank you for sharing this great information with us. I am really glad to learn about this because it helps me to increase my knowledge.
ofcause I will be grow up.
  Reply With Quote
Old 21st June 2011, 03:07 PM   #4179
udailey is offline udailey  United States
diyAudio Member
 
Join Date: Mar 2008
Lets not forget its DIY and even if just thinking aloud, this kind of discourse is fun.
The metering idea is a good one and with slightly matched LDRs it would do the job well since impedance would still be about equal.
I am missing what gmphadte is saying. Could you explain a bit more?
__________________
purchase LDRs anytime Also try my Resistor Replacers or LDR based Input Selector Email me. diyldr@gmail.com
  Reply With Quote
Old 21st June 2011, 07:58 PM   #4180
DRONE7 is offline DRONE7  New Zealand
diyAudio Member
 
Join Date: Aug 2008
Quote:
Originally Posted by gmphadte View Post
Young at 51.
Just a spring chicken
  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 11:11 PM.


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