Lightspeed Attenuator a new passive preamp - Page 296 - 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 January 2010, 11:17 PM   #2951
tinitus is offline tinitus  Europe
diyAudio Moderator R.I.P.
 
Join Date: Nov 2005
Lightspeed is Lightspeed, as is

If you like to devellop a more advanced diy optocoupler version, it might be better and more interesting to have this in a seperate thread, along with relevant commercial stuff
Would you like help to have it moved to new thread
Please, its a positive suggestion, you decide
  Reply With Quote
Old 21st January 2010, 02:53 PM   #2952
tinitus is offline tinitus  Europe
diyAudio Moderator R.I.P.
 
Join Date: Nov 2005
I will soon start moving posts to new thread

Nothing wrong with your posts, but you are messing up a good thread, thats all

New thread here

http://www.diyaudio.com/forums/analo...p-general.html


Those interested in "LIGHTSPEED", please continue
  Reply With Quote
Old 21st January 2010, 07:51 PM   #2953
romana is offline romana  United States
diyAudio Member
 
Join Date: Jul 2008
I'll rephrase the question and make it George-specific:

Has anyone built multiple versions of George's basic DIY LS circuit that are identical, save for using different quality parts on the audio signal side? Specifically, I'm looking for a comparison of the Farnell or Mouser BOM parts vs. the usual "audiophile grade" stuff. If so, have you heard a difference that can be attributed to the upgrade?

This isn't meant to be critical of George's choices or of the BOMs as posted -- those parts are perfectly good quality and ones that I would normally choose for a typical project. I'm just curious to know how far anyone has taken George's LS design without modifying the circuit and, given the few parts involved, if a better (often more expensive) grade is worth the extra cost.

That's it!
~R

PS. If anyone wants to continue talking about other designs on the alternative thread, that works for me, too.
  Reply With Quote
Old 22nd January 2010, 11:28 AM   #2954
diyAudio Member
 
Join Date: Feb 2009
Default Just build one and enjoy.

The only parts in the signal path are the LDRs. I soldered mine directly to the XLR sockets and haven't potted them (yet) thinking the ambient air in the small box stabilizes at some point. The rest of the circuit is not in the audio path. How much time and money do you want to spend to light up LEDs? I haven't made variations because Lightspeed sounded great from the start. What's the point of discussing the possible differences in sound if you don't believe George or others who have said that Lightspeed is very good. George has generously shared his design which simple and inexpensive to build. Instead of obsessing about 'what-ifs', just build one and enjoy. Not meaning to offend, just opining.
  Reply With Quote
Old 22nd January 2010, 12:10 PM   #2955
udailey is offline udailey  United States
diyAudio Member
 
Join Date: Mar 2008
The minimalist Lightspeed is awesome. Changes to power supply type can make differences. Small differences. Impedance makes differences. I have build a LOT of Lightspeeds. Most of them on protoboard. I dont remember even one time thinking I should swap that Dale resistor back in instead of the Xicon. I have always said that a junk potentiometer is as good as a P&G to control the Lightspeed. Now, I think thats mostly true but not 100%. A pot that does not make good connection still can insert some noise. I had an OLD pot that was actually seized up. I tried to use that one and had to wrench on the pot to get it to break free and turn. Once turning it worked fine. However, when I would turn it I could hear some noise on the speakers. This noise came from the poor contact the wiper was making. So maybe some sparking or similar going on inside the pot. Anyway, if the noise gets to the LEDs it can get in the resistor side of the LDR.
Another pot I had was not turning smoothly. A little jerky. This is a pain. What happens is you are trying to turn it up just a little and the pot sticks so you use more pressure to turn it and then it jumps and the volume is up high.
So, I dont think the resistors in the Lightspeed will matter AT ALL. Get cheapies. I think the pot is a little bit of an issue but if you want a cheap pot use an ALPHA from Mouser. They are really smooth and work wonderfully with a Lightspeed. No noise and only $2.50. Thats as audiophool as I would get with the pot. George has said many times a Linear supply is best. So many of us go buy a wallwart. Well this is a beginners project so thats a good thing to tell a beginner and they will soon have sound no beginner has a right to DIY!! But the sound can get better than a wallwart. George has found some wallwarts that are well made and sound good, but what if you get that junker out of the junk drawer that was probably the death of your last router it was plugged into anyway? I think you can do better. Build a linear supply with a small toroid, use a few quality diodes and snub them, smooth with a few thousand uF of snubbed electrolytics and then regulate a few times. You can get away with using the tiny LM317LZ for this circuit and they are less than 50 cents each.
Other than that? Dont worry about using PRP resistors or Black Gate caps. Its not going to help you. More important is to build unlike an audio engineer and more like a power electronics engineer. Do your diodes ring and cause power spikes? Do your caps do their job smoothing?
Ensure all solder joints are good and not cold joints. That could insert some noise.
Now, understand, I am just humoring your questions here. What I mean by that is that you dont need to go to these extremes. George doesnt and he just got written up in Stereophile and they loved his product. The man cant keep up with orders, so obviously Stereophile arent the only ones that love his product. I love his product and I have not met anyone that has listened to it that can criticize it. It only takes about an hour to build. Lay it out on paper today for a perf board. Tomorrow wire and solder the thing together. Its really that easy.
Uriah
__________________
purchase LDRs anytime Also try my Resistor Replacers or LDR based Input Selector Email me. diyldr@gmail.com
  Reply With Quote
Old 22nd January 2010, 12:34 PM   #2956
diyAudio Member
 
Join Date: Jan 2002
Uriah-

I have emailed you concerning your lighter note attenuator per your signature twice and have not received any reply. Can you please send me the info privately? Thank you....
  Reply With Quote
Old 23rd January 2010, 01:37 AM   #2957
alazira is offline alazira  United States
diyAudio Member
 
alazira's Avatar
 
Join Date: Jun 2007
Location: Las Vegas
Blog Entries: 1
Quote:
Originally Posted by romana View Post
I'll rephrase the question and make it George-specific:

Has anyone built multiple versions of George's basic DIY LS circuit that are identical, save for using different quality parts on the audio signal side? Specifically, I'm looking for a comparison of the Farnell or Mouser BOM parts vs. the usual "audiophile grade" stuff. If so, have you heard a difference that can be attributed to the upgrade?

This isn't meant to be critical of George's choices or of the BOMs as posted -- those parts are perfectly good quality and ones that I would normally choose for a typical project. I'm just curious to know how far anyone has taken George's LS design without modifying the circuit and, given the few parts involved, if a better (often more expensive) grade is worth the extra cost.

That's it!
~R

PS. If anyone wants to continue talking about other designs on the alternative thread, that works for me, too.
Hi Romana,

As has already been said, the only part in the signal path is the resistor side of the optocoupler (aside from wire and connectors of course). Using boutique parts for the LDR power supply will probably yield minimal/no difference. Consider that the power is constant and doesn't vary unless you change the volume. That being said, I did test wal-wart (cheap one, not like the one George uses) vs 9v battery vs 12v SLA battery and did find differences.

1. walwart - very noisy
2. 9v battery - very quiet but sounded a bit "mushy" compared to the walwart
3. 12v SLA - as quiet as the 9v and no hint of mushyness (not a real word)
  Reply With Quote
Old 23rd January 2010, 08:44 AM   #2958
Jaap is online now Jaap  Netherlands
diyAudio Member
 
Jaap's Avatar
 
Join Date: Dec 2002
Location: Netherlands
Quote:
Originally Posted by alazira View Post
Hi Romana,

As has already been said, the only part in the signal path is the resistor side of the optocoupler (aside from wire and connectors of course). Using boutique parts for the LDR power supply will probably yield minimal/no difference. Consider that the power is constant and doesn't vary unless you change the volume. That being said, I did test wal-wart (cheap one, not like the one George uses) vs 9v battery vs 12v SLA battery and did find differences.

1. walwart - very noisy
2. 9v battery - very quiet but sounded a bit "mushy" compared to the walwart
3. 12v SLA - as quiet as the 9v and no hint of mushyness (not a real word)
I do not get it. You tell us that it does not matter but in practice you have found big differences in sound. Isn't it time to change your believes ?

I would think that all the noise from the power supply is modulated on the lightsource and thus is transferred to audio.
  Reply With Quote
Old 23rd January 2010, 08:53 AM   #2959
soongsc is offline soongsc  Taiwan
diyAudio Member
 
soongsc's Avatar
 
Join Date: Mar 2005
Location: Taiwan
Quote:
Originally Posted by alazira View Post
Hi Romana,

As has already been said, the only part in the signal path is the resistor side of the optocoupler (aside from wire and connectors of course). Using boutique parts for the LDR power supply will probably yield minimal/no difference. Consider that the power is constant and doesn't vary unless you change the volume. That being said, I did test wal-wart (cheap one, not like the one George uses) vs 9v battery vs 12v SLA battery and did find differences.

1. walwart - very noisy
2. 9v battery - very quiet but sounded a bit "mushy" compared to the walwart
3. 12v SLA - as quiet as the 9v and no hint of mushyness (not a real word)
I'm curious as to what kind of noise you hear with the walwart. What does it really sound like?
__________________
Hear the real thing!
  Reply With Quote
Old 23rd January 2010, 10:17 AM   #2960
diyAudio Member
 
georgehifi's Avatar
 
Join Date: Sep 2003
Location: Manly Australia (Jewel of the Pacific)
Send a message via MSN to georgehifi
If done the way I have outlined, that is, a 12vdc LINEAR regulated >300mA wall wart then feeding to a 5vdc regulated supply (properly smoothed) this is not distinguishable from a Lithium Ion 1800mAh rechargeable battery, as has been blind tested by a dozen so called audiophiles on a high rez system, no one could reliably detect which was which. But if a smp 12vdc regulated wall wart was used, then almost everyone could tell a difference.
Cheers George
Attached Images
File Type: jpg Lightspeed Attenuator MkII Circuit.JPG (38.8 KB, 418 views)
__________________
Avatar : Production Lightspeed Attenuator
www.lightspeedattenuator.com

Last edited by georgehifi; 23rd January 2010 at 10:23 AM.
  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 09:27 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