I have 5 matched pairs supplied by Udailey that I will part with. Problem is I lost the sheet with measurements that show which of the 10 are pairs. If someone wants them as is PM me. Otherwise at some point I will get around to measure them and put each pair in the swap thread so they get used. 
Ok, Thanks a lot George.
Now, be possible run without noise with Bridge of Zen? It have 15dB of gain.
Jose
A New Level of Fidelity
All,
I finally got my 11 channel LDR box up and running last week, and have been listening to a variety of sources, trying see if my initial reaction was subjective. I must say, the improvement is dramatic. Where have I been?
My case has two other variables - 1) for 2-channel music I have an Adcom SLC-505 with an Alps volume control, I think, that is 30 years old and is of course now switched out of the path, and 2) the 3 front channels are bi-amped and the active crossovers were after the volume pot, so the sound picked up some noise. Right now the LDRs are dead last before the power amp inputs. The music is full line level until the last possible point.
It is quieter now, and the left channel is consistently a little louder than the right. I have not yet adjusted the trimmers because I'm still marveling at the sound. Percussive instruments like piano in front of an orchestra, have better delineation and imaging. Plucked strings, especially on bass instruments, have more impact. I put on Secret Story by Metheny and Mays, and I was aware of the plucking of the bass guitar underneath the many layers.
There must be something happening with wipers on tracks that affects transients, especially with age and wear. I had no idea my volume potentiometer was such a bottleneck for sound quality.
Paul
All,
I finally got my 11 channel LDR box up and running last week, and have been listening to a variety of sources, trying see if my initial reaction was subjective. I must say, the improvement is dramatic. Where have I been?
My case has two other variables - 1) for 2-channel music I have an Adcom SLC-505 with an Alps volume control, I think, that is 30 years old and is of course now switched out of the path, and 2) the 3 front channels are bi-amped and the active crossovers were after the volume pot, so the sound picked up some noise. Right now the LDRs are dead last before the power amp inputs. The music is full line level until the last possible point.
It is quieter now, and the left channel is consistently a little louder than the right. I have not yet adjusted the trimmers because I'm still marveling at the sound. Percussive instruments like piano in front of an orchestra, have better delineation and imaging. Plucked strings, especially on bass instruments, have more impact. I put on Secret Story by Metheny and Mays, and I was aware of the plucking of the bass guitar underneath the many layers.
There must be something happening with wipers on tracks that affects transients, especially with age and wear. I had no idea my volume potentiometer was such a bottleneck for sound quality.
Paul
Volume potentiometer carbon or conductive plastic, start to deteriorate from the first time they are rotated.
The wiper metallic (usually brass) is very light sprung dimple contact with the conductive track as to keep wear down.
Add to this.
Dissimilar materials (bass/carbon brass/conductive plastic) with light contact between them with even small current passing through can give you a "diode effect" Google it and do some reading.
Cheers George
I would love to have a set, what price and would you be willing to ship to Scotland?
Cheers.
I suggested the same 3 or 4 years ago.
Fine trim the relative right to left current control resistances to get perfect R/L channel balance at every step.
And get the volume steps at the volumes you actually want to listen at.
Loud, normal, quiet, that's just 3 steps.
Add on an alternative of -3db to each and you get 6 steps.
Easily done with a rotary switch - 2way 6positions or buy a expensive one from China and change the existing resistors. Mine cost ~£6 for two stereo 100k 12 step switchers
I suggest the NSL32SR2S quad matched as they have a constant lower impedance 40-50ohms at 20mA, and you need this to get down low in level for whatever the reason, also the quad matching gives a better log feel to the rotation of the led controller (VC).
The only problem with this way your suggesting is if one ldr can get to 40ohms with 20mA and the other can't, so you may have to give it 30mA or 40mA especially if they are just the NSL32SR2, and at that current it won't last long at all you'll cook it in no time. This also goes for the other projects here on other threads that don't use matched NSL32SR2S LDR's.
Cheers George
The only problem with this way your suggesting is if one ldr can get to 40ohms with 20mA and the other can't, so you may have to give it 30mA or 40mA especially if they are just the NSL32SR2, and at that current it won't last long at all you'll cook it in no time. This also goes for the other projects here on other threads that don't use matched NSL32SR2S LDR's.
Cheers George
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I forgot if there was or not a discussion regarding why the resistors in LDR are supposed to be better than resistors in stepped attenuator?
(A) The quality of the series resistors?
(B) The quality of the contact?
Anyone that is contemplating building an LED/LDR attenuator should have done sufficient reading and homework to realise that too much LED current will damage the devices.
Any fine trimming of current controlling resistances should keep to the general advice on maximum long term current. Gross trimming for unmatched LED/LDR is outside the scope of any "Lightspeed" type attenuator.
Any fine trimming of current controlling resistances should keep to the general advice on maximum long term current. Gross trimming for unmatched LED/LDR is outside the scope of any "Lightspeed" type attenuator.
(A) LDR is not as linear as an ordinary resistor. People differ on whether this matters.Jay said:
(B) An LDR volume control has no contacts, so people who are concerned about contacts but not concerned about resistor linearity should choose an LDR control.
All volume control methods have weaknesses.