I promised PDF of my PCB, but I installed it and forgot to take backside picture.
I'll do it next time when I'll open my DCB1.
Anyone can recommend a good 100k liniar motorized pot ?
I'm using a Bours one from Mouser but the resistence variation is bad and total input resistence of lightspeed is pretty inconsistent.
I'm using a Bours one from Mouser but the resistence variation is bad and total input resistence of lightspeed is pretty inconsistent.
A few of my customers have used the Alps 100kohm A taper kits from ebay. Don't use linear if you've built it to Lightspeed specs that I've posted, otherwise it will come on too fast.
Here is a ruff search link
remote volume potentiometer | eBay
Cheers George
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Adrian, I have experienced the same as you (see my post #5260).
The big blue ALPS motorized potentiometer is a little bit better than the BOURNS potentiometer.
As I have written: I will replace my analog potentiometer by a digital one.
I have etched a couple of small prototype PCBs representing the schematic of my post: a digital potentiometer (MCP42100), being followed by a VCCS.
The MCP42100 will be controlled by the PIC using the SPI protocol.
If you like to have (and if you have a PIC evaluation board) I will send you the small prototype PCB.
Best regards - Rudi
The big blue ALPS motorized potentiometer is a little bit better than the BOURNS potentiometer.
As I have written: I will replace my analog potentiometer by a digital one.
I have etched a couple of small prototype PCBs representing the schematic of my post: a digital potentiometer (MCP42100), being followed by a VCCS.
The MCP42100 will be controlled by the PIC using the SPI protocol.
If you like to have (and if you have a PIC evaluation board) I will send you the small prototype PCB.
Best regards - Rudi
I have found a substantial powersupply for those not too keen on building one, or using a linear wall wart like I supply with the Lightspeed, this is well thought out and quite cheap, and comes in all voltages and the right leads.
From reports on the huge Lightspeed thread over on Audiogon, users that have tried it, have some positive remarks. At $44 why build one.
TeraDak U9VA Linear Low noise Power Supply
Cheers George
From reports on the huge Lightspeed thread over on Audiogon, users that have tried it, have some positive remarks. At $44 why build one.
TeraDak U9VA Linear Low noise Power Supply
Cheers George
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Once you tally up everything, a nice chassis, IEC sockets, IEC cord, switch, usb port ect, and that transformer is not cheap. And if you have a close look at it there's a bunch of Panasonic "Gold" FM caps. This is quality goods inside. Just that chassis would be $30
Cheers George
Cheers George
This is a great concept and I had to try it--thanks for sharing it. I built it using an Alps 100K pot. Only issue I have is sound bleed-through at no volume. At this point, I am reading 1.83 VDC being fed to the center LEDs while the outer LEDs are at almost 5 VDC. Did I wire the Alps backwards perhaps? Sound and tracking are spot on and is quite good. Depth is very much increased.
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Hi Whaleman, if you built it as per my posted circuit, you will always have a very small signal at minimum volume, as the series LED/LDR cannot go to 0ohms.
Also if you use a 100kohm log dual pot you will get better low level adjustability. And if you used the NSL32SR2S as quad matched set it will get closer to zero level as they have lower more consistent impedances at 20mA.
Cheers George
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Well first of all a big thank you to George for sharing this concept. Have been using it for quite some time now and with excellent results. Have tried different implementations of LDR preamps on this forum but I just love the original George configuration.(Expensive passion preamp now gathering dust).
But I have come to realise that this Lightspeed is very susceptible to power supply. I know that George advocates a 12 volt wall wart with 7805 subsequent regulation, but I am finding that difficult to implement. To be specific I have a wallwart feeding a 220uf cap bypassed with 0.1uf cap into the 7805 reg and then out to a 10uf cap bypassed with 0.1uf cap.This sounds overbright.Am I wrong here since this does not sound as good as a wallwart smps I prefer to use.Would love to get this right and wring just a little more out of the Lightspeed if thats possible. I should perhaps add I am using the Lightspeed to drive a 2024 T amp which I know is not ideal impedance wise.
But I have come to realise that this Lightspeed is very susceptible to power supply. I know that George advocates a 12 volt wall wart with 7805 subsequent regulation, but I am finding that difficult to implement. To be specific I have a wallwart feeding a 220uf cap bypassed with 0.1uf cap into the 7805 reg and then out to a 10uf cap bypassed with 0.1uf cap.This sounds overbright.Am I wrong here since this does not sound as good as a wallwart smps I prefer to use.Would love to get this right and wring just a little more out of the Lightspeed if thats possible. I should perhaps add I am using the Lightspeed to drive a 2024 T amp which I know is not ideal impedance wise.
Hi Tony, glad you like the Lightspeed design.
Today it is hard to find linear wall warts to power the Lightspeed. Most now are switch mode, and yes while they work fine they do sound brighter.
I have measure the difference and the smp ones and they have quite a bit more H/F noise factor on the output of the Lightspeed, up to 10 x higher, even though it goes through a discrete 5vdc regulated 7805 power supply last.
I believe the switching noise of the smp wall warts are coming in via the earth plane, this is why I always say use linear wall warts.
Way back in this thread I posted screen shots of the noise differences on the output of the Lightspeed Attenuator using smp and linear wall warts.
Cheers George
Today it is hard to find linear wall warts to power the Lightspeed. Most now are switch mode, and yes while they work fine they do sound brighter.
I have measure the difference and the smp ones and they have quite a bit more H/F noise factor on the output of the Lightspeed, up to 10 x higher, even though it goes through a discrete 5vdc regulated 7805 power supply last.
I believe the switching noise of the smp wall warts are coming in via the earth plane, this is why I always say use linear wall warts.
Way back in this thread I posted screen shots of the noise differences on the output of the Lightspeed Attenuator using smp and linear wall warts.
Cheers George
Thanks George, appreciate it. I did get these LDRs and will bread board it since the chassis I was trying to implement it was quite tight.
PS: Typo. that should have been shunt ldr's not series, in my quote above.
Cheers George
Thanks. The shunt LDRs being the outer ones in the schematic? These had the full voltage at no volume. I did hear some very three dimensional qualities to the sound the time that I did have it in the circuit.
Tony
Put bigger caps on your psu and put ~100uf and a small film or ceramic on legs of each ldr. This will help.
Put bigger caps on your psu and put ~100uf and a small film or ceramic on legs of each ldr. This will help.
I am trying to understand how tweaking the LED side of things affects the sound of the light sensing resistors since the circuits are independent of each other except for the light. Especially if you are using a wall wart...just wanna know...I do have capacitors on the legs of the LDRs.
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