Lightspeed remote control
Hi Dean,
Feel free to use the remote control for personal use. Modifications are fine as long as you are up to sorting out any complications you may cause with your modifications.
1. The current source is essential as without it you will fry the reference chain and probably the electronic pot as well. IXYS do the IXTP 02N50D depletion mosfet, which is rated at 200ma.
2. I use the LF347 and the 45K DS1802.
3. You have answered your own question.
4. Nelson Pass did some extensive testing of the Silonex parts used in the Lightpeed and published his findings way back in the forum thread. He concluded that the Silonex work best over a specific range of LED current and I have specified the 39K resistors to mimic this range. It works well in my system and I have not felt the need to change anything. Feel free to work out your own range but watch out for the max LED current.
5. The 1M resistors are a hang-up of mine from suffering a mechanical pot failure in a valve preamp. The resistor guarantees bias maintenance under such conditions.
I hope this helps.
Regards
Paul
Hi Dean,
Feel free to use the remote control for personal use. Modifications are fine as long as you are up to sorting out any complications you may cause with your modifications.
1. The current source is essential as without it you will fry the reference chain and probably the electronic pot as well. IXYS do the IXTP 02N50D depletion mosfet, which is rated at 200ma.
2. I use the LF347 and the 45K DS1802.
3. You have answered your own question.
4. Nelson Pass did some extensive testing of the Silonex parts used in the Lightpeed and published his findings way back in the forum thread. He concluded that the Silonex work best over a specific range of LED current and I have specified the 39K resistors to mimic this range. It works well in my system and I have not felt the need to change anything. Feel free to work out your own range but watch out for the max LED current.
5. The 1M resistors are a hang-up of mine from suffering a mechanical pot failure in a valve preamp. The resistor guarantees bias maintenance under such conditions.
I hope this helps.
Regards
Paul
Buy gain I take it you have too much volume level at the start of the volume controls travel? If so please give the make and specs of your cdp output/impedance and your poweramps input and if it's tube or solid state if tube what the input tube is. And your speakers efficiency.
Cheers George
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George. Yes too much volume at the start. My battery is giving about 7v so that may account for some of it? I have yet to add a 7805
Output impedance of the cdp is 50ohms (nice) output impedance of my power amps is 47k (I think) Gainclones. Speakers are 97dB Horns.
Thanks
Rob.
Output impedance of the cdp is 50ohms (nice) output impedance of my power amps is 47k (I think) Gainclones. Speakers are 97dB Horns.
Thanks
Rob.
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Your 7 volts instead of 5 could be the problem and I can see the NSL32SR2S's not lasting too long either. Once you have lowered down to 5v this may fix your problem if it does not then I can see only two ways maybe three of fixing your problem because of the high efficiency of your speakers and high gain of the Gainclone
My preferred way would be to increase the feedback on your power amp, this lowers the gain but in a Gainclone this may be impossible to do as the feedback network can be within the amp chip itself.
Second least preferred way is to put a two resistor voltage divider at the input of the power amp.
There is a third way you could reduce gain around the I/V stage or the output buffer in the cd player if they are not using unity gain stages there.
Cheers George
My preferred way would be to increase the feedback on your power amp, this lowers the gain but in a Gainclone this may be impossible to do as the feedback network can be within the amp chip itself.
Second least preferred way is to put a two resistor voltage divider at the input of the power amp.
There is a third way you could reduce gain around the I/V stage or the output buffer in the cd player if they are not using unity gain stages there.
Cheers George
Puffin
Between now and whenever you regulate down to 5V please NEVER turn the volume all the way up or all the way down. Whatever you used for a current limiting resistor/s was meant for 5V and now may be letting through more current than your LDRs will like. George isnt kidding about the LDRs not lasting long with to much voltage. Just like any LED, they will fry if given the chance.
Also, I have noticed that if you match under one voltage and you use another voltage they are not as well matched under that new voltage. LDRs purchased from me were all matched at 5VDC. If run current source they will also not match as well.
One man mentioned a while back, I forget who or what thread, that adding a 1k resistor in front of his control pot in series with the 5VDC extended the usable range of his LDRs. So now he can turn the control pot more to 2 or 3 oclock instead of the 10 oclock he was dealing with.
I have 96dB speakers. I can not turn them higher than 9 oclock with a gainclone either. This is one of the things we get used to using LDRs. One thing you can try someday if you see one for sale is a multiturn pot of the same value as your control pot, but for now, regulate down as right now you are using 40% more power to the LDRs as was intended, add a 700-1kOhm resistor in series with 5VDC to protect and extend.
Uriah
Between now and whenever you regulate down to 5V please NEVER turn the volume all the way up or all the way down. Whatever you used for a current limiting resistor/s was meant for 5V and now may be letting through more current than your LDRs will like. George isnt kidding about the LDRs not lasting long with to much voltage. Just like any LED, they will fry if given the chance.
Also, I have noticed that if you match under one voltage and you use another voltage they are not as well matched under that new voltage. LDRs purchased from me were all matched at 5VDC. If run current source they will also not match as well.
One man mentioned a while back, I forget who or what thread, that adding a 1k resistor in front of his control pot in series with the 5VDC extended the usable range of his LDRs. So now he can turn the control pot more to 2 or 3 oclock instead of the 10 oclock he was dealing with.
I have 96dB speakers. I can not turn them higher than 9 oclock with a gainclone either. This is one of the things we get used to using LDRs. One thing you can try someday if you see one for sale is a multiturn pot of the same value as your control pot, but for now, regulate down as right now you are using 40% more power to the LDRs as was intended, add a 700-1kOhm resistor in series with 5VDC to protect and extend.
Uriah
George and Uriah. Thanks for you input on this. I have made a 5v PS tonight (well 4.9v) The pot is still as sensitive. I bought some cheap unmatched LDRs whilst waiting for the next batch from Uriah. So if I have damaged them it is no great shakes. In fact they can't be that badly matched as I have a rock solid soundstage and excellent centre vocals etc.
Uriah if i understand correctly I simply add a 1k resistor to the 5v+ lead and then connect the other end of the resistor to the pot?
I have used this for a few hours now and it is very revealing and sounds great.
Uriah if i understand correctly I simply add a 1k resistor to the 5v+ lead and then connect the other end of the resistor to the pot?
I have used this for a few hours now and it is very revealing and sounds great.
After a few adventures along the way I have mine running out in the workshop right now!! Works AOK and I seem to have good useable range (at least out there anyway).
This is destined to reside in a b1 buffer so will be really interesting to see how it compares to the stepped pot thats in there right now.
Thanks to all for the help along the way.....
Fran
This is destined to reside in a b1 buffer so will be really interesting to see how it compares to the stepped pot thats in there right now.
Thanks to all for the help along the way.....
Fran
No wonder, I thought you were using what I recomend NSL32SR2S, or NSL32SR2 or if you must NSL32SR3 which won't go low enough in level and are even harder to match, no wonder you have this problem there are so many different LDR's out there their resistance span varies greatly, stick with the NSL32SR2S's and all will be fine.
Cheers George
There's some of your problem they don't go as low in volume as the
NSL32SR2S.
Resistance Table
Full Light Full Dark
NSL32SR2S 40ohm to 5 megohm
NSL32SR3 150ohm to 25 megohm
Big difference as you can see, also the matching becomes way harder to get four matched together. And when you match 4 together you get a far better logarithmic feel to the volume control, than you do when you only match the series and then the shunts separately
Cheers George
NSL32SR2S.
Resistance Table
Full Light Full Dark
NSL32SR2S 40ohm to 5 megohm
NSL32SR3 150ohm to 25 megohm
Big difference as you can see, also the matching becomes way harder to get four matched together. And when you match 4 together you get a far better logarithmic feel to the volume control, than you do when you only match the series and then the shunts separately
Cheers George
