Will blue and yellow power supply wires cause a problem passing by the input and output wires and rca's as you can see in picture? With there length being as they are that is the only way I can route them unless I add more wire and run them away from rca's and run them behind boards or along front face plate.
The DC power supply wires crossing the signal wires should not be a problem. See page 63 of the article that I referenced which shows signal wires and DC power wires in close proximity. It actually minimizes loop area.
AC wires and transformer close to signal wires and circuitry are problematic.
Also note that sometimes the orientation of the toroid transformer may affect noise. Rotate to find minimum noise orientation. Also use your ohmmeter to make sure that the ground of the RCA jacks are not in contact with the chassis.
AC wires and transformer close to signal wires and circuitry are problematic.
Also note that sometimes the orientation of the toroid transformer may affect noise. Rotate to find minimum noise orientation. Also use your ohmmeter to make sure that the ground of the RCA jacks are not in contact with the chassis.
Boards are drilled and mounted just need to solder back. Do I need to use star ground from ground wire under board or star ground fron RCA negative inputs like before trying to stop noise? Ben Mah when I put volt meter on negative of RCA jack and preamp chassis it is making a connection. What problem can this cause noise? What is best way to stop contact if that's what needs to be done?
The RCA wires should connect to the boards as shown in 6L6's build guide:
Pearl (one) Build
As far as the RCA jacks, check continuity before wiring them up. With no connections, the RCA jack ground should not have continuity with the chassis. There should be plastic washers on both sides of the chassis to insulate the RCA jacks from the chassis.
As for grounding to chassis, please check 6l6's build guide, and perhaps others can help you. I do not have a Pearl so I do not have any direct experience.
Pearl (one) Build
As far as the RCA jacks, check continuity before wiring them up. With no connections, the RCA jack ground should not have continuity with the chassis. There should be plastic washers on both sides of the chassis to insulate the RCA jacks from the chassis.
As for grounding to chassis, please check 6l6's build guide, and perhaps others can help you. I do not have a Pearl so I do not have any direct experience.
Hum is greatly reduced, at volume at 50% you need to put your ear up against speaker to hear hum. Before at 30% you could hear it at 6 feet away. After switching power on one side of box left channel had no hum but right still did so I reconnected star ground from bottom of board and hum disappeared. I'm just wondering if reconnecting star ground off of negative RCA jacks might make it even quieter. I'm still considering moving power supply to its own box to maybe get that last bit of hum out. Thanks everyone for there time and effort helping me reduce hum could not have done it without everyone's help, this is really a great place for someone like me getting there feet wet in DIY electronics, thanks again everyone.
@ben mah
Thanks for ground loop presentation. Good stuff.
I had two questions:
On page 63 would the loop area be better or worse if the transformer and rectifier section were flipped (ie like my Hafler DH-200)?
On page 71 I'm not sure why the turntable is not in the loop area like it was in the diagram on the previous page. Or, conversely, why the loop between AC cords to the preamp and power amp remain.
Thanks for ground loop presentation. Good stuff.
I had two questions:
On page 63 would the loop area be better or worse if the transformer and rectifier section were flipped (ie like my Hafler DH-200)?
On page 71 I'm not sure why the turntable is not in the loop area like it was in the diagram on the previous page. Or, conversely, why the loop between AC cords to the preamp and power amp remain.
page 63: Transformer at the front and power supply at the back is the usual arrangement for First Watt amps. I believe that this arrangement has advantages. It keeps the transformer away from the back of the amp where low level audio signals enter. Transformers emit strong magnetic forces that are bad for audio. AC wires are bad too so they should enter at the middle of the case in stereo amps and kept to the centre of the case on its way to the transformer.
page 71: I believe you are correct. The loop area should still be there, albeit much smaller. The thing to do is to group the AC cords together as much as possible.
page 71: I believe you are correct. The loop area should still be there, albeit much smaller. The thing to do is to group the AC cords together as much as possible.
I recently put together the PassLab Pearl 2 phono preamp from the mail order kit and am getting a consistent hum coming in both channels. I remember reading in multiple forums that you need to get the grounding issue right, but they never tell you what issue they were having or how it was resolved. I also separated the power supply from the left and right channel boards by a meter long shielded cable (3 conductor plus braided shield), to no effect. The Pearl seems to be very sensitive transformers in close proximity. Moving the main unit away from other equipment helps a little, but doesn’t eliminate the hum completely. The main case is steel and the front panel is plastic. The phono input shields are grounded at the inputs. The DC power cable shield is grounded to the power supply case and to the preamp case. Any suggestions or is anyone else experiencing this issue? If you get past the hum the phono preamp sounds really good.
A few issues:
1. Power supply: Looking at your picture of the power supply, Ground at AC power has two green wires. One goes directly to chassis ground. The other goes bridge rectifier for ground lift. From bridge rectifier there is a yellow wire with stripe that goes to PS board ground. There is also a green wire from PS board ground to chassis ground. This wire needs to be removed. The PS ground should only connect to the chassis ground through the bridge rectifier.
2. Main board and chassis: There should only be one Ground point on the chassis. At the power entry there is a ground point to the chassis and it is not clear to me what is connected to it. The V+, V-, and Ground from the power supply should go directly to the main boards.
The RCA connectors should be isolated from the chassis and connect directly to the main boards. Check to make sure that they are isolated.
As mentioned, there should only be one ground point. Only the turntable ground and the ground from both boards connect to it. The ground point on the boards is between C4 and C12.
1. Power supply: Looking at your picture of the power supply, Ground at AC power has two green wires. One goes directly to chassis ground. The other goes bridge rectifier for ground lift. From bridge rectifier there is a yellow wire with stripe that goes to PS board ground. There is also a green wire from PS board ground to chassis ground. This wire needs to be removed. The PS ground should only connect to the chassis ground through the bridge rectifier.
2. Main board and chassis: There should only be one Ground point on the chassis. At the power entry there is a ground point to the chassis and it is not clear to me what is connected to it. The V+, V-, and Ground from the power supply should go directly to the main boards.
The RCA connectors should be isolated from the chassis and connect directly to the main boards. Check to make sure that they are isolated.
As mentioned, there should only be one ground point. Only the turntable ground and the ground from both boards connect to it. The ground point on the boards is between C4 and C12.
Attachments
Well Ben Mah, I wanted to give you a BIG THANK YOU for helping me figure out that grounding issue with the Pearl 2. It really wasn't clear to me from the directions (instructions) provided when building it. I still have a little hum but I think that will get cleared up once I get a new case. Thanks again