I am a novice and trying to learn to build my own tube preamplifier. in the attached wiring diagram I have tried to wire 3 inputs, selector switch, LED lights and volume control. Would appreciate DIY members to please review my wiring diagram to see if it is correct or needs to be modified. Thanks so much for your assistance.View attachment scan0013.pdf
The two channels' grounds should be kept separate, and each returned to the single main audio ground
of the common power supply. That ground point may then be connected to the chassis at one point.
The LED circuit needs rework.
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What's the selector switch that you are using? Choose a resistor for 1-10mA current in the LEDs,
depending on the brightness that you want. Use a single resistor from the LV power supply,
and connect it to the anode of all the LEDs, switching the selected cathode to ground to light it up.
Use the LV filament supply, not the HV supply, for this.
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the RCA input ground/return (the RCA barrel) should be run close coupled with the signal flow wire (or coaxial cable) all the way to the selector switch input. That makes 6 cable pairs for the 6 inputs.
The switch output is also a cable pair (or coaxial cable) that goes to the vol pot input. That makes 2 pairs for the stereo signal.
The output from the vol pot is a cable pair that goes to the amplifier PCB. That makes 2 pairs for the stereo signal.
In all of the preceding there is NO CONNECTION from any of these signal wires to any part of the chassis, nor to any part of the power ground/zero volts.
The switch output is also a cable pair (or coaxial cable) that goes to the vol pot input. That makes 2 pairs for the stereo signal.
The output from the vol pot is a cable pair that goes to the amplifier PCB. That makes 2 pairs for the stereo signal.
In all of the preceding there is NO CONNECTION from any of these signal wires to any part of the chassis, nor to any part of the power ground/zero volts.
Rayma thank you very much for your help.
The switch I plan to use is the C&K Components A30415RNCQ.
C&K Components - A30415RNCQ - 4 PositionS 3P 2.5A@125VAC; 350MA@250VDC PC Terminal Rotary Switch - Allied Electronics
This was the example I found on the internet and I was trying use. Does the grounding look OK in the drawing?
http://customers.hbci.com/~erix/images/amp_images/mad_mods/rotary_switch.pdf
Thank you for the information in hooking up the LED's. If I understand i should use LV to anode (positive) and then cathode (negative) to the selector switch.
The following is the LED I am planning to use:
Dialight - 609-1122-130F - RED 12VDC BLACK HOUSING 9MM LED PANEL MOUNT INDICATOR - Allied Electronics
Thank you very much for your assistance.
Taipan
The switch I plan to use is the C&K Components A30415RNCQ.
C&K Components - A30415RNCQ - 4 PositionS 3P 2.5A@125VAC; 350MA@250VDC PC Terminal Rotary Switch - Allied Electronics
This was the example I found on the internet and I was trying use. Does the grounding look OK in the drawing?
http://customers.hbci.com/~erix/images/amp_images/mad_mods/rotary_switch.pdf
Thank you for the information in hooking up the LED's. If I understand i should use LV to anode (positive) and then cathode (negative) to the selector switch.
The following is the LED I am planning to use:
Dialight - 609-1122-130F - RED 12VDC BLACK HOUSING 9MM LED PANEL MOUNT INDICATOR - Allied Electronics
Thank you very much for your assistance.
Taipan
AndrewT thank you very much for your help.
If I understand correctly, I should have 3 positive leads from the "inputs" and the 3 ground leads from the "inputs" going to the switch (in lieu of chassis ground as shown in my drawing). I would then go with a 5P/4T selector switch?
4 poles for positive/ground and left/right and the 1 pole for LED's. Understand I should hookup cathode (negative) leads to the selector switch.
From the switch "out puts" I would take the out put from the "positive input" and "ground input" and connect them to the volume control. I found this on the internet and was using it for an example a selector switch/LED lights/volume control.
http://customers.hbci.com/~erix/images/amp_images/mad_mods/rotary_switch.pdf
Again, thanks so much for your assistance.
Taipan
If I understand correctly, I should have 3 positive leads from the "inputs" and the 3 ground leads from the "inputs" going to the switch (in lieu of chassis ground as shown in my drawing). I would then go with a 5P/4T selector switch?
4 poles for positive/ground and left/right and the 1 pole for LED's. Understand I should hookup cathode (negative) leads to the selector switch.
From the switch "out puts" I would take the out put from the "positive input" and "ground input" and connect them to the volume control. I found this on the internet and was using it for an example a selector switch/LED lights/volume control.
http://customers.hbci.com/~erix/images/amp_images/mad_mods/rotary_switch.pdf
Again, thanks so much for your assistance.
Taipan
Your switch does not need any extra contacts for the signal returns.
For one channel, your three signal flow/hot arrive at the switch and connect to three contacts. The three returns common under the switch from this common you run the output ground/return as the second wire with the switched hot/flow signal to the vol pot.
Repeat for the other channel.
For one channel, your three signal flow/hot arrive at the switch and connect to three contacts. The three returns common under the switch from this common you run the output ground/return as the second wire with the switched hot/flow signal to the vol pot.
Repeat for the other channel.
Avoid connecting any of the "grounds" to the chassis. They all do connect together (exactly how is another matter).
Just one point on that web of grounds may connect to the chassis, sometimes through a resistor or other
component.For the LEDs, connect as you mentioned, and then the moving selector contact is grounded,
to complete the circuit.
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AndrewT,
Thanks again for your assistance. I still learning so trying to understand your last note.
From your last note i understand for one channel the hot leads would be connect to the switch. The common/ground leads would not be connected to the switch put tied together and a lead going from this connection to the volume control.
Below is the drawing have been using as a guide. If you use this drawing it should correctly describe the the hot leads connection from the inputs to switch and from switch to volume control as I believe your are stating:
http://customers.hbci.com/~erix/images/amp_images/mad_mods/rotary_switch.pdf
Now for the common/ground leads:
- In the drawing it shows a green wire going from the chassis to the volume control (first disc then tied to second disc via jumper wire) and then to the amp.
- From your note I would assume in lieu of the green lead from the chassis (as referenced above), you would have the one ground lead coming from the 3 common wires tired together (from common channel) with a lead going on the first disc on the volume control (where the green wire is shown in the diagram; common lead and hot lead from the same channel on disc one). Then on the second disc you connect the lead (from 3 common input tied together from other channel) from ground to volume control (where green wire in the diagram; common lead and hot lead from the same channel on disc two).
If my understanding regarding the above is correct how do you take the ground leads from the volume control to amp? In the diagram it shows a jumper wire (wire in green) from disc one to disc two then the lead to amp. would you then tie the leads from the grounds in disc 1 and disc 2 together to the amp?
Thanks again for your help. It greatly appreciated.
Taipan
Thanks again for your assistance. I still learning so trying to understand your last note.
From your last note i understand for one channel the hot leads would be connect to the switch. The common/ground leads would not be connected to the switch put tied together and a lead going from this connection to the volume control.
Below is the drawing have been using as a guide. If you use this drawing it should correctly describe the the hot leads connection from the inputs to switch and from switch to volume control as I believe your are stating:
http://customers.hbci.com/~erix/images/amp_images/mad_mods/rotary_switch.pdf
Now for the common/ground leads:
- In the drawing it shows a green wire going from the chassis to the volume control (first disc then tied to second disc via jumper wire) and then to the amp.
- From your note I would assume in lieu of the green lead from the chassis (as referenced above), you would have the one ground lead coming from the 3 common wires tired together (from common channel) with a lead going on the first disc on the volume control (where the green wire is shown in the diagram; common lead and hot lead from the same channel on disc one). Then on the second disc you connect the lead (from 3 common input tied together from other channel) from ground to volume control (where green wire in the diagram; common lead and hot lead from the same channel on disc two).
If my understanding regarding the above is correct how do you take the ground leads from the volume control to amp? In the diagram it shows a jumper wire (wire in green) from disc one to disc two then the lead to amp. would you then tie the leads from the grounds in disc 1 and disc 2 together to the amp?
Thanks again for your help. It greatly appreciated.
Taipan
Rayma, thanks so much for your input. Looks like i need to do some more research on grounding. Thanks again for your help.
Taipan
Taipan
AndrewT,
Thanks again for your assistance. I still learning so trying to understand your last note.
From your last note i understand for one channel the hot leads would be connect to the switch. The common/ground leads would not be connected to the switch put tied together and a lead going from this connection to the volume control.
Below is the drawing have been using as a guide. If you use this drawing it should correctly describe the the hot leads connection from the inputs to switch and from switch to volume control as I believe your are stating:
http://customers.hbci.com/~erix/images/amp_images/mad_mods/rotary_switch.pdf
Now for the common/ground leads:
- In the drawing it shows a green wire going from the chassis to the volume control (first disc then tied to second disc via jumper wire) and then to the amp.
- From your note I would assume in lieu of the green lead from the chassis (as referenced above), you would have the one ground lead coming from the 3 common wires tired together (from common channel) with a lead going on the first disc on the volume control (where the green wire is shown in the diagram; common lead and hot lead from the same channel on disc one). Then on the second disc you connect the lead (from 3 common input tied together from other channel) from ground to volume control (where green wire in the diagram; common lead and hot lead from the same channel on disc two).
If my understanding regarding the above is correct how do you take the ground leads from the volume control to amp? In the diagram it shows a jumper wire (wire in green) from disc one to disc two then the lead to amp. would you then tie the leads from the grounds in disc 1 and disc 2 together to the amp?
Thanks again for your help. It greatly appreciated.
Taipan
Thanks again for your assistance. I still learning so trying to understand your last note.
From your last note i understand for one channel the hot leads would be connect to the switch. The common/ground leads would not be connected to the switch put tied together and a lead going from this connection to the volume control.
Below is the drawing have been using as a guide. If you use this drawing it should correctly describe the the hot leads connection from the inputs to switch and from switch to volume control as I believe your are stating:
http://customers.hbci.com/~erix/images/amp_images/mad_mods/rotary_switch.pdf
Now for the common/ground leads:
- In the drawing it shows a green wire going from the chassis to the volume control (first disc then tied to second disc via jumper wire) and then to the amp.
- From your note I would assume in lieu of the green lead from the chassis (as referenced above), you would have the one ground lead coming from the 3 common wires tired together (from common channel) with a lead going on the first disc on the volume control (where the green wire is shown in the diagram; common lead and hot lead from the same channel on disc one). Then on the second disc you connect the lead (from 3 common input tied together from other channel) from ground to volume control (where green wire in the diagram; common lead and hot lead from the same channel on disc two).
If my understanding regarding the above is correct how do you take the ground leads from the volume control to amp? In the diagram it shows a jumper wire (wire in green) from disc one to disc two then the lead to amp. would you then tie the leads from the grounds in disc 1 and disc 2 together to the amp?
Thanks again for your help. It greatly appreciated.
Taipan
Rayma thanks for the link. I will study the information. i am sure the information will extremely helpful. Thanks again for your assistance. Greatly appreciated.
Taipan
Taipan
I recommend you leave out "grounding" and instead think about "circuits".
Current flows around loops. It starts at the Source and MUST RETURN to the Source via a loop.
That loop NEEDS two wires. A Flow wire and a Return wire. Circuits cannot work without that loop. Learn to make ALL connections using the two wires. That is fundamental to getting any and every circuit to work.
But a word of caution. Loops are aerials. A big loop picks up more emi than a small loop.
Your two wire connection has the potential to becoming a very big loop. You must keep all your varying current loop areas very small. That means the Flow wire and the Return wire must be close coupled all along the route. Even the terminations must be layed out to minimise the loop area.
DC does not cause emi, it is varying currents that cause emi. All your AC signals cause emi. pulsed DC cause emi.
Concentrate your efforts on making all you Flow and Return connections with a very small loop area. Twisting a pair of Flow and Return wires does not reduce the loop area, instead the alternating loops pick up or emit alternating phase of emi. The alternating phases help to attenuate the emi. A good alternative to twisted pair with low loop area is flexible coaxial cable. I find twisted pair using cat5e or twisted 0.6mm insulated hook-up wire is much easier to work with compared to coax.
Only after you have completed all your connections with two wires, do you then compare your layout to the original schematic and find the (very) few places where a voltage reference between two separate circuits requires a voltage reference connection. You then need to add in this final connection using a trace or wire and it's two ends need to tap into the two circuits so that you do not force a conductor to share two very disimiilar currents.
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How to wire a source selector switch and a volume pot comes up so often that it ought to be a sticky thread. That would save people from the trouble of doing a forum search.
DF96- I agree with you thought. It would be great to have a resource on how to wire a source selector switch and volume pot. I would assume the questions comes up often. Not only would save me time but also would help the kind people who trying to help me learn this process.
AndrewT said it for me, that's the layout i settled for after trying a few others in my DCB1.
Twisted pair from each right channel input RCA socket to the switch, the grounds for each channel common (grouped together) close to the switch with one core continuing on to the pot's right channel ground pin
Repeat for the left channel.
Keep right and left channel signal grounds (returns) separate from each other.
Twisted pair from each right channel input RCA socket to the switch, the grounds for each channel common (grouped together) close to the switch with one core continuing on to the pot's right channel ground pin
Repeat for the left channel.
Keep right and left channel signal grounds (returns) separate from each other.
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