In my opinion, the Lightspeed is the greatest improvement you can make to a high end stereo for only $450.00! I have a pair of McIntosh 240 tube amps which I opened up, and took the gain pots out of the signal path. I run the tape outputs from my preamp into the Lightspeed when I play records as this bypasses the volume, balance, tone, and other contorls on the preamp. I run a dual control attenuator through a single control attenuator so I have master volume, and balance. The Lightspeed, and that simple modification to my amps made a huge difference. Listening to music is much more fun and engaging now.
An externally hosted image should be here but it was not working when we last tested it.
Bins
I think its your grounding. However if its not your grounding, your supply looks fine. Maybe you have a cold solder joint or such. It is very possible that the noise comes from the wall wart. Try a 9V battery. Use alligator clips. Clip it to the rails right after that 7810. Maybe the noise goes away. If not, make sure you dont have the signal ground and earth ground mixed in the lightspeed and never connect signal gnd to the 0V.
Uriah
I think its your grounding. However if its not your grounding, your supply looks fine. Maybe you have a cold solder joint or such. It is very possible that the noise comes from the wall wart. Try a 9V battery. Use alligator clips. Clip it to the rails right after that 7810. Maybe the noise goes away. If not, make sure you dont have the signal ground and earth ground mixed in the lightspeed and never connect signal gnd to the 0V.
Uriah
I use a 470uf before the 7805 the a 100uf after then a .1uf . I do not earth the neg rail to signal ground, it floats with the neg of the wall wart.
Cheers George
Attachments
Hi,
I would dump the 7810. It is not needed. Indeed, it probably needs more headroom than the 12V input, which may be the problem. If you want to use both then find a 14V+ wall-wart. The 7805 works fine w/ 12V input.
Hi George,
I will remove that 7810 section and will try with the 7805 section alone. Since my cabinet is made up of wood, I will try with an explicit signal ground point. As you suggested earlier, I will also cover the LDR's with aluminium foil to avoid RF interference.
@Uriah: The supply ground and signal ground are not mixed up. Any way, I will check once again. I will also check for a cold joint....
Will impedance mismatch be an issue ?
Best regards,
Bins.
I will remove that 7810 section and will try with the 7805 section alone. Since my cabinet is made up of wood, I will try with an explicit signal ground point. As you suggested earlier, I will also cover the LDR's with aluminium foil to avoid RF interference.
@Uriah: The supply ground and signal ground are not mixed up. Any way, I will check once again. I will also check for a cold joint....
Will impedance mismatch be an issue ?
Best regards,
Bins.
I wouldn't think so. I'd say it's more the wooden case.
Also try not earthing the negative side of the supply, let it float.
Cheers George
Hi George,
The negative side of the supply is not earthed as shown in the supply schematic which was posted earlier. It is actually connected to the DC supply socket's outer terminal. So, I think the light speed ground is the place to check for the noise issues:
1. RF Interference - Can this be avoided using aluminium shield around the LDR's (The shield will also be connected to the LDR's common ground point) ?
2. Ground - Can I take the RCA ground's to a final earth point and ground it explicitly ?
3. Cold Joints.
Best regards,
Bins.
The negative side of the supply is not earthed as shown in the supply schematic which was posted earlier. It is actually connected to the DC supply socket's outer terminal. So, I think the light speed ground is the place to check for the noise issues:
1. RF Interference - Can this be avoided using aluminium shield around the LDR's (The shield will also be connected to the LDR's common ground point) ?
2. Ground - Can I take the RCA ground's to a final earth point and ground it explicitly ?
3. Cold Joints.
Best regards,
Bins.
Hi,
The interconnects that I am using is having RF shield. So, I don't think it is not the source for hum... I think the supply lines, transformers etc inside the mono blocks can also be a reason for the hum. I will try an aluminium casing instead of wood to tackle this issue. Also the RCA pins will be start grounded.
Best regards,
Bins.
The interconnects that I am using is having RF shield. So, I don't think it is not the source for hum... I think the supply lines, transformers etc inside the mono blocks can also be a reason for the hum. I will try an aluminium casing instead of wood to tackle this issue. Also the RCA pins will be start grounded.
Best regards,
Bins.
I just plugged in one of my oldest Lightspeeds and was using it most of the day yesterday. I get the same noise you are describing. Well, I assume its the same. Its mounted in an open frame so anything could get in there. I have used it at 3 different residences in 2 different states and have the same buzz in my speakers. Its for sure the Lightspeed and its for sure my choice in power supply when I built that one. Still sounds incredible but its a junky little Rohm switching power supply. I blame my noise on the fact its a switching supply.
I think you should give the 9V battery solution a try. Its super easy. RF interference probably wouldnt sound like hummmm.
Uriah
I think you should give the 9V battery solution a try. Its super easy. RF interference probably wouldnt sound like hummmm.
Uriah
Nice amps!!! HexadecimalX, when you bought both the single and dual Lightspeed Attenuators from me I wondered how this was going to sound, good to hear it's working well for you.
It's good from your photo that you set the duals around midday position, as this gives the best 2hd figures for the matched quad set of NSL32SR2S inside, as it gives a null point of 2hd.
Also I would like to know what speaker setup you are using, as with all my customers, I keep loose records of their setups for future reference.
Just to try an experiment reverse the Lightspeeds to see if there is a difference (master single first and the dual after)
Cheers George
The source of hummmmmm....
Hello Uriah,
Please see the details of the power supply I am using : http://www.farnell.com/datasheets/36265.pdf. I think it is the power supply that is causing the issue. Please confirm.
Best regards,
Bins.
Hello Uriah,
Please see the details of the power supply I am using : http://www.farnell.com/datasheets/36265.pdf. I think it is the power supply that is causing the issue. Please confirm.
Best regards,
Bins.
Hi George,
Finally, I was (we were) able to identify the problematic element. I am going for a 12V battery to drive the light speed. What should be the required capacity (Ah rating). Will a 12V battery with 2.1 Ah enough for the purpose or do I need to go for a higher Ah value ?
Best regards,
Bins.
Finally, I was (we were) able to identify the problematic element. I am going for a 12V battery to drive the light speed. What should be the required capacity (Ah rating). Will a 12V battery with 2.1 Ah enough for the purpose or do I need to go for a higher Ah value ?
Best regards,
Bins.
Last edited:
Like I posted before, this is Lithium-ion and enough to give 12hrs of listening before a short 1 hour recharge.
http://cgi.ebay.com/12V-Lithium-ion...emQQptZLH_DefaultDomain_0?hash=item5886dafa1d
Cheers George
http://cgi.ebay.com/12V-Lithium-ion...emQQptZLH_DefaultDomain_0?hash=item5886dafa1d
Cheers George
Last edited:
Hi,
I am going to use the 12V rechargeable cell to drive my light speed (Feels like being in a classical Nagra world with battery packs). I have found a simple circuit to use with the battery section to indicate the state of the charge remaining (Green -> Fully charged; No Color -> Neutral; Red -> Low Battery)
Best regards,
Bins.
I am going to use the 12V rechargeable cell to drive my light speed (Feels like being in a classical Nagra world with battery packs). I have found a simple circuit to use with the battery section to indicate the state of the charge remaining (Green -> Fully charged; No Color -> Neutral; Red -> Low Battery)
Best regards,
Bins.
Attachments
Hello Andrew,
The indicator circuit is not always connected to the battery. It is actually used to check the status of the battery when required.
Best regards,
Bins.
The indicator circuit is not always connected to the battery. It is actually used to check the status of the battery when required.
Best regards,
Bins.
I would use rechargeable batteries. And get two sets 
Still, I would test your power supply with 9V before you rebuild everything. If its not the power supply making the noise you sure wont be pleased that you changed everything. But yeah, the switchmode should go anyway sooner or later.
Uriah
Still, I would test your power supply with 9V before you rebuild everything. If its not the power supply making the noise you sure wont be pleased that you changed everything. But yeah, the switchmode should go anyway sooner or later.
Uriah
Hello Uriah,
When I provided the light speed with 9V, the noise is gone. Thanks a lot for your earlier suggestion. In my final version, I will use a 12V supply.
Will adding a LED to indicate the ON/OFF state contribute to noise ???
Best regards,
Bins.
When I provided the light speed with 9V, the noise is gone. Thanks a lot for your earlier suggestion. In my final version, I will use a 12V supply.
Will adding a LED to indicate the ON/OFF state contribute to noise ???
Best regards,
Bins.
I would use rechargeable batteries. And get two sets
Still, I would test your power supply with 9V before you rebuild everything. If its not the power supply making the noise you sure wont be pleased that you changed everything. But yeah, the switchmode should go anyway sooner or later.
Uriah