well George,
I have to be honest with you . . . I will not quite believe this until I hear it with my own ears
Partly because Peter already did a comparison between a tantalum audiophile resistor and LDR in the series position and he marginally preferred the tantalum.
hehehe, so . . . . so far it's two for LDR and one against.
Thing is, people have different ideas about what sounds "good" so it may just come down to a matter of taste.
The bottom line for me is that I am very happy indeed that you introduced us to these devices regardless of the final method of implementation.
Just now with my 2.2k TF020's in series & LDR in shunt I have a clarity, transparency and smoothness combined like I never heard before anywhere.
thanks
I have to be honest with you . . . I will not quite believe this until I hear it with my own ears
Partly because Peter already did a comparison between a tantalum audiophile resistor and LDR in the series position and he marginally preferred the tantalum.
hehehe, so . . . . so far it's two for LDR and one against.
Thing is, people have different ideas about what sounds "good" so it may just come down to a matter of taste.
The bottom line for me is that I am very happy indeed that you introduced us to these devices regardless of the final method of implementation.
Just now with my 2.2k TF020's in series & LDR in shunt I have a clarity, transparency and smoothness combined like I never heard before anywhere.
thanks 
Well, I listened to the OPC271 (it looks like the same model posted here previously) with an NCD amp bypassing my original volume control. I can say the improvement was VERY significant! The low level details were more noticeable, soundfield depth was better. It is true that this impedance compatibility is of great concern. A few friends actually hooked the OPC271 based volume control to an active speaker with volume control; even with the original speaker 50KOhm volume control turned full up, the sound quality dropped significantly. So we know that when properly used, the sound quality is much better.mikelm said:well George,
I have to be honest with you . . . I will not quite believe this until I hear it with my own ears
Partly because Peter already did a comparison between a tantalum audiophile resistor and LDR in the series position and he marginally preferred the tantalum.
hehehe, so . . . . so far it's two for LDR and one against.
Thing is, people have different ideas about what sounds "good" so it may just come down to a matter of taste.
The bottom line for me is that I am very happy indeed that you introduced us to these devices regardless of the final method of implementation.
Just now with my 2.2k TF020's in series & LDR in shunt I have a clarity, transparency and smoothness combined like I never heard before anywhere.
merlin2069er said:
Hi JG, here is your answer to your email about soldering and terminal strips.
"Hi JG, that's ok as it is a crush (high pressure) contact that has far
better contact than a wiper in a potentiometer which is only a feather
weight touch contact.
You can solder them in just do it quick, maybe with the help of an aligator
clip heat sink on each leg as you solder it to take the heat away from the
ldr.
Post up your findings when you've decided on how it sounds."
As for your queery in your last post, first if you do not have an ocilloscope and frequency generator, this is the way to set up the 1k trimpot. ( there is only one 1k trimpot to be used only on the louder channel).
First listen to some known music that has a good central image with NO 1k pot in place or short it out, then play the music and decide which channel is the louder by looking at the central image.
Then only have the 1k pot on that channel not the other channel, then start to turn the pot up till the image becomes central, what you've done is bring the louder channel down in line with the other channel, there you have it the crude way of calibrating the Lightspeed to your system.
Cheers George
Stop the match please ! Everyone interested in the best solution must do the comparison by himself...
It's very easy to do btw. You just have to use a couple of CDs (same of course) and fix a listening level (of course again you need some stuff to work with, here a sound level meter will be useful). Then you have to measure the series value of the LDRs. You can do two experiments :
- the first is to replace the "free" LDR with a LDR fed by the current giving the "same" series value.
- the second is to replace the series LDRs by the equivalent resistors (you can use the highest precision you may find).
Thats all folks !
If you guys still didn't hear any difference, stop high quality audio and buy any Chinese low cost integrated amp after go drink all the saved money !...
My Very Best to you all,
It's very easy to do btw. You just have to use a couple of CDs (same of course) and fix a listening level (of course again you need some stuff to work with, here a sound level meter will be useful). Then you have to measure the series value of the LDRs. You can do two experiments :
- the first is to replace the "free" LDR with a LDR fed by the current giving the "same" series value.
- the second is to replace the series LDRs by the equivalent resistors (you can use the highest precision you may find).
Thats all folks !
If you guys still didn't hear any difference, stop high quality audio and buy any Chinese low cost integrated amp after go drink all the saved money !...
My Very Best to you all,
Member
Joined 2009
Paid Member
I know this thread is exploring the finer points, but I'm yet to realize the starting point !!
My needs are 6 channels. I can't see this working out if I have to match 12 LDRs so I will have to go with "Mark1.5" with LDRs in both series and shunt positions but I will only attempt to match the shunt LDRs. That's still 6 of 'em so it won't be perfect. The left-over LDRs that weren't well enough matched for the shunt positions will be used as fixed series resistors.
Here's where some advice will be helpful.
1) Any concerns if I use +/-20V regulated supply rails ? - I will have these in the chasis already for the pre-amps and I'd like to avoid using yet another psu.
2) Is my general schematic OK ? (attached) - I have used some fixed resistors which I'll select to try and balance out some of the differences between LDRs - at least it makes a bad situation better.
3) I have separate signal and power grounds. The signal grounds will meet the chasis at some point but I want to reserve the option to choose where and possibly to use a ground-lift resistor in the process.
4) I haven't put any adjustment resistors in parallel with the actual LDRs, I assume that although this may improve matching it will hurt the sound quality.
Am I missing anything ?
p.s. The name 'TGM' is a reference to the amplifier it will be used with, see: http://www.diyaudio.com/forums/showthread.php?s=&threadid=140461
My needs are 6 channels. I can't see this working out if I have to match 12 LDRs so I will have to go with "Mark1.5" with LDRs in both series and shunt positions but I will only attempt to match the shunt LDRs. That's still 6 of 'em so it won't be perfect. The left-over LDRs that weren't well enough matched for the shunt positions will be used as fixed series resistors.
Here's where some advice will be helpful.
1) Any concerns if I use +/-20V regulated supply rails ? - I will have these in the chasis already for the pre-amps and I'd like to avoid using yet another psu.
2) Is my general schematic OK ? (attached) - I have used some fixed resistors which I'll select to try and balance out some of the differences between LDRs - at least it makes a bad situation better.
3) I have separate signal and power grounds. The signal grounds will meet the chasis at some point but I want to reserve the option to choose where and possibly to use a ground-lift resistor in the process.
4) I haven't put any adjustment resistors in parallel with the actual LDRs, I assume that although this may improve matching it will hurt the sound quality.
Am I missing anything ?
p.s. The name 'TGM' is a reference to the amplifier it will be used with, see: http://www.diyaudio.com/forums/showthread.php?s=&threadid=140461
Attachments
Cased Up LS
Hi All,
I've finally cased my LS up and have just been enjoying some time machine-gunning CDs through it. I put it on the scope with a rudimentary sig-gen and it seemed to be pretty much spot on without any tweaking (thanks Uriah!). In fact, I found that tweaking the trimpot didn't have any particular effect on the P-P voltage, so I just set them both to 225R (for what it was worth).
George, the sound is superb! Thank you! I am using rather soft-ish amps (and one needs a service), but I'm absolutely gob-smacked by the detail and timbre I'm getting now.
If you haven't tried a Lightspeed, just do it!
I posted some pics over at Rock Grotto:
http://rockgrotto.proboards.com/index.cgi?board=m&action=display&thread=4066&page=1#49030
Cheers
Jon
Hi All,
I've finally cased my LS up and have just been enjoying some time machine-gunning CDs through it. I put it on the scope with a rudimentary sig-gen and it seemed to be pretty much spot on without any tweaking (thanks Uriah!). In fact, I found that tweaking the trimpot didn't have any particular effect on the P-P voltage, so I just set them both to 225R (for what it was worth).
George, the sound is superb!
Thank you! I am using rather soft-ish amps (and one needs a service), but I'm absolutely gob-smacked by the detail and timbre I'm getting now.If you haven't tried a Lightspeed, just do it!
I posted some pics over at Rock Grotto:
http://rockgrotto.proboards.com/index.cgi?board=m&action=display&thread=4066&page=1#49030
Cheers
Jon
I know this relationship between LEDs & vol control exists:
But is there a formula that defines the ideal relationship/operation? i.e. given the series R the shunt R can be calculated or vice versa?
Or in other words if both series & shunt LDRs were ideal devices how would the table of series & shunt resistances look at various vol settings (0-63dB)?
But is there a formula that defines the ideal relationship/operation? i.e. given the series R the shunt R can be calculated or vice versa?
Or in other words if both series & shunt LDRs were ideal devices how would the table of series & shunt resistances look at various vol settings (0-63dB)?