Okay, Jon! HaHa!
banbadoo, I am wondering if the increase in volume is drastic or just jumpy. I can see this happening with LDRs that have been burnt a little. So maybe in soldering them in you did shunts first and burnt them a little, then got a bit better at soldering them and did a fine job on series. When they get burnt its possible to drive them low in resistance but then have them jump up to a high level that they wont move from til you drive them lower in resistance again. Just a possibility. I am about out of ideas. I thought initially you probably just needed 100k, or as Ryelands said, that the track was dirty.. both problems would have been likely fixed with the 100k. Well, keep us posted on the second set of LDRs. I know you were probably careful with them but be even extra careful this time and be careful on all 4 of their leads.
Its just this way:
Apply flux to pad and leads.
Heat the pad/not the lead.
Apply solder to the iron while its still on the pad.
Quickly roll over to the lead and as soon as it jumps UP the lead a little you need to remove the iron.
Blow on the leads.
Wish you luck and congrats on your big knob.
Uriah
banbadoo, I am wondering if the increase in volume is drastic or just jumpy. I can see this happening with LDRs that have been burnt a little. So maybe in soldering them in you did shunts first and burnt them a little, then got a bit better at soldering them and did a fine job on series. When they get burnt its possible to drive them low in resistance but then have them jump up to a high level that they wont move from til you drive them lower in resistance again. Just a possibility. I am about out of ideas. I thought initially you probably just needed 100k, or as Ryelands said, that the track was dirty.. both problems would have been likely fixed with the 100k. Well, keep us posted on the second set of LDRs. I know you were probably careful with them but be even extra careful this time and be careful on all 4 of their leads.
Its just this way:
Apply flux to pad and leads.
Heat the pad/not the lead.
Apply solder to the iron while its still on the pad.
Quickly roll over to the lead and as soon as it jumps UP the lead a little you need to remove the iron.
Blow on the leads.
Wish you luck and congrats on your big knob.
Uriah
I've been using a Lightspeed Attenuator for about a half a year now, and I have a confession to make: I just didn't like it. It's much clearer than a pot or stepped attenuator, but it's always had a "hollow" sound to it that really bothers me. I've the LDA by itself, with a B1 and with a DCB1. I've tried it with 3 different amplifiers, and with two different sets of speakers. Everybody loves these things so I assumed I had made some mistake when I built it. But I couldn't get to sound right no matter how much I fussed with it.
Yesterday I hooked the LDA up between my PC and amplifier to listen to some FLAC. Usually I never needed to turn the volume up on the LDA more than 1/4th the way to get full volume. But I had left the volume on the PC down at 18% or something like that, so I had to turn the LDA up to 50% or so...
...and the hollowness that had been bugging me completely went away! If I turn the PC volume up and the LDA volume down it comes back.
So I'm thinking of adding some additional resistance to the LDA so I can run it in the 50%-60% range rather than 20%-30%. I'll try using the 68r and 1k values recommended in that buildanamp.com article to see if that helps.
Yesterday I hooked the LDA up between my PC and amplifier to listen to some FLAC. Usually I never needed to turn the volume up on the LDA more than 1/4th the way to get full volume. But I had left the volume on the PC down at 18% or something like that, so I had to turn the LDA up to 50% or so...
...and the hollowness that had been bugging me completely went away! If I turn the PC volume up and the LDA volume down it comes back.
So I'm thinking of adding some additional resistance to the LDA so I can run it in the 50%-60% range rather than 20%-30%. I'll try using the 68r and 1k values recommended in that buildanamp.com article to see if that helps.
Hi blue lander
If you are not using boards purchased from buildanamp.com then DONT switch to 68R resistors. You will burn your LDRs. The 68R in my near-lightspeed circuit are aided by a 200R trimmer in the protection of the LDRs.
I can tell you my assumption. LDRs really dont do well with higher than 2.5V or so going through them. When the volume it turned up on your computer it is outputting higher than 2.5V. This is my guess. I have put 6V through them with a tubed pre and the distortion is audible at this point. I have not tested with lower voltages but graphs posted earlier in this thread by Mr Pass and old test data by Silonex shows that it is better to add a gain stage AFTER the LDRs or to use unity gain devices if you want to stick something in front of them.
Its just my guess but I know that in my system I keep the volume at half on the computer.
Now, maybe its not this at all. Another thing it could be is that your Lightspeed has a resistance curve that looks like a smile. Usually the lowest Rtot of the Lightspeed is at around mid-volume. You might find that its the Rtot you are enjoying. If you want to try a lower Rtot then you would increase the value of those resistors feeding the LDRs and increase the Voltage feeding them. You could try 6,7,8V if you are using an LM317 to feed or some other variable regulator. Remember this: when you are turning the lightspeed's volume control you do not want the minimum resistance of any of the LDRs to go lower than 40R. This is where changing the value of the resistors feeding the LDRs comes into play because they will keep the LDRs from going below 40R but the higher voltage you feed them then the higher resistance you will need to keep above 40R. If I were experimenting to find a solution and if I thought it was Rtot that was sounding better for you, I would build up a protoboard to hold a few trimmers that would be in series with the protection resistors and then I would dial up the voltage until I got something like 4-7k Rtot and try that out. Rtot=total resistance between input and ground.
Uriah
If you are not using boards purchased from buildanamp.com then DONT switch to 68R resistors. You will burn your LDRs. The 68R in my near-lightspeed circuit are aided by a 200R trimmer in the protection of the LDRs.
I can tell you my assumption. LDRs really dont do well with higher than 2.5V or so going through them. When the volume it turned up on your computer it is outputting higher than 2.5V. This is my guess. I have put 6V through them with a tubed pre and the distortion is audible at this point. I have not tested with lower voltages but graphs posted earlier in this thread by Mr Pass and old test data by Silonex shows that it is better to add a gain stage AFTER the LDRs or to use unity gain devices if you want to stick something in front of them.
Its just my guess but I know that in my system I keep the volume at half on the computer.
Now, maybe its not this at all. Another thing it could be is that your Lightspeed has a resistance curve that looks like a smile. Usually the lowest Rtot of the Lightspeed is at around mid-volume. You might find that its the Rtot you are enjoying. If you want to try a lower Rtot then you would increase the value of those resistors feeding the LDRs and increase the Voltage feeding them. You could try 6,7,8V if you are using an LM317 to feed or some other variable regulator. Remember this: when you are turning the lightspeed's volume control you do not want the minimum resistance of any of the LDRs to go lower than 40R. This is where changing the value of the resistors feeding the LDRs comes into play because they will keep the LDRs from going below 40R but the higher voltage you feed them then the higher resistance you will need to keep above 40R. If I were experimenting to find a solution and if I thought it was Rtot that was sounding better for you, I would build up a protoboard to hold a few trimmers that would be in series with the protection resistors and then I would dial up the voltage until I got something like 4-7k Rtot and try that out. Rtot=total resistance between input and ground.
Uriah
Finished my second lighspeed earlier today. I finally managed to "tweak" it so the volume control is not so sensitive. It feels more "linear" turning til knob..
But this one have a severe channel imbalance. Have to turn the balance knob during volume increase/decrease alot. Infact at some listening values the balance (4.7kohm pot) is not enough. I will maybe try a 10kohm for this.
My speakers are approx 97 dB sensitive and at the lowest volume setting the sound is at "normal" listening level.
Is it possible to adjust this with another resistor in series with the 100k pot?
I notice ~1.6Vdc from the psu to the lightspeed pcb at lowest volume setting. 5v at maximum.
I am using (this time) an alps 100k dual log.
I was very careful soldering .....
Resistors on the pcb is now 180ohm and 8.6kohm.
But this one have a severe channel imbalance. Have to turn the balance knob during volume increase/decrease alot. Infact at some listening values the balance (4.7kohm pot) is not enough. I will maybe try a 10kohm for this.
My speakers are approx 97 dB sensitive and at the lowest volume setting the sound is at "normal" listening level.
Is it possible to adjust this with another resistor in series with the 100k pot?
I notice ~1.6Vdc from the psu to the lightspeed pcb at lowest volume setting. 5v at maximum.
I am using (this time) an alps 100k dual log.
I was very careful soldering .....
Resistors on the pcb is now 180ohm and 8.6kohm.
Just an idea...As you have such sensitive speakers, are you able to reduce the gain on your amplifier?
Its a pain when there is a lot of gain and then efficient speakers. One solution we have found on this forum is to stick a 10R-100R trimmer in series with the 5V that feeds the 100k pot. I know this sounds nuts but it works. You tweak the trimmer til you get a Rtot that is quieter at min volume. This trimmer can dramatically change Rtot so get a 20-25 turn trimmer so you can have great control over it.
Another solution is to stick a 100k pot AFTER the first 100k pot. You would put it on the line that feeds the dual series LDRs. The 100k trimmer goes to ground. At minimum volume you start to tweak the 100k trimmer and the lower its resistance the higher the max resistance of the series LDRs. So you have your shunts at very low resistance and you have your series at high resistance at min volume and you should get respectable low volume this way.
Uriah
Another solution is to stick a 100k pot AFTER the first 100k pot. You would put it on the line that feeds the dual series LDRs. The 100k trimmer goes to ground. At minimum volume you start to tweak the 100k trimmer and the lower its resistance the higher the max resistance of the series LDRs. So you have your shunts at very low resistance and you have your series at high resistance at min volume and you should get respectable low volume this way.
Uriah
Thought I would mention that I found a cool software a few days back. People claim its better than Foobar and I have not been critically listening as I have been ripping my CDs to FLAC since I found the software.
Its not a ripping software though, just a listening software.
It takes near zero room on your computer, installs in a snap and is super simple to use. If you are a minimalist, this is for you.
Minimalist Audio Player: Cue Sheet Support And StealthAudioPlayer
Also have the exact opposite, J.River. Am trying it for a month to see if I want to buy it. I like it so far as well. I like that I can control it with my Android phone.
I wont post more about this but thought you guys might want to give that StealthAudioPlayer a shot.
Uriah
Its not a ripping software though, just a listening software.
It takes near zero room on your computer, installs in a snap and is super simple to use. If you are a minimalist, this is for you.
Minimalist Audio Player: Cue Sheet Support And StealthAudioPlayer
Also have the exact opposite, J.River. Am trying it for a month to see if I want to buy it. I like it so far as well. I like that I can control it with my Android phone.
I wont post more about this but thought you guys might want to give that StealthAudioPlayer a shot.
Uriah
Bambadoo,
If excessive gain is the problem, as would be indicated by a gain pot set to the lowest settings, I think the best solution is to reduce the source output as you suggested you might do. From what I've read and heard the LDRs do not like high voltages from a distortion standpoint. So, operating them at lower voltages gets you the benefits of lower distortion and a smaller series resistance in actual use. Both probably good things.
If excessive gain is the problem, as would be indicated by a gain pot set to the lowest settings, I think the best solution is to reduce the source output as you suggested you might do. From what I've read and heard the LDRs do not like high voltages from a distortion standpoint. So, operating them at lower voltages gets you the benefits of lower distortion and a smaller series resistance in actual use. Both probably good things.
Need your opinion before I replace the LDR.
I tested my Lightspeed with Signal Generator and four channel scope at 1khz.
I can't balance the (at either of the pot adjustment) signal when volume control is at minimum. The difference is more than double between left and right but can perfectly balance when I turn the volume control at about a quarter up and adjust the pot.
Did try to adjust both pot without power, both can be adjusted from 1r to max.
Thanks,
Joe
I tested my Lightspeed with Signal Generator and four channel scope at 1khz.
I can't balance the (at either of the pot adjustment) signal when volume control is at minimum. The difference is more than double between left and right but can perfectly balance when I turn the volume control at about a quarter up and adjust the pot.
Did try to adjust both pot without power, both can be adjusted from 1r to max.
Thanks,
Joe
If you only had from the audio generator a max of 200mV all should be fine. You have other problems. Sounds like the series or shunts are not matched well, try swaping the shunts, then test again, or then the series, and test again. This is when it's good to have 2 x 8 pin DIL sockets, then they can be changed around without soldering, once your happy then solder them into the sockets with a fine hot tip.
Cheers George
Cheers George
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George,
Thanks for the socket suggestions.
Uriah,
Thanks for the offer. I still have a brand new match pair that I bought from you almost a year ago, most likely it will work fine.
Also have an orphan that I removed from the other board, I'll try that first.
My other board is not fully balance but it's perfect for my defective room.
Joe
Thanks for the socket suggestions.
Uriah,
Thanks for the offer. I still have a brand new match pair that I bought from you almost a year ago, most likely it will work fine.
Also have an orphan that I removed from the other board, I'll try that first.
My other board is not fully balance but it's perfect for my defective room.
Joe