That looks great dear Terry ! build to last
"Eso es un amplificador de hombre" = "That is a man amplifier" very good 😀
best regards
Juan
"Eso es un amplificador de hombre" = "That is a man amplifier" very good 😀
best regards
Juan
Looks fantastic Terry. I love seeing all-diy cases. You really love checkerplate - I've seen it used in your other amps too.
Terry IMPRESSIVE! The complete homemade chassis is a step above most DIY builds. Mine won't look like that. Glad those heatsinks worked out. Your an inspiration to the community, thx for the pics.... Peace.....
OK, I listened all day yesterday and some more this morning. It has a really good sound but I have a hum I can't seem to get rid of. The right channel is worse than the left. My big CD player gave up the ghost so I am using a Memorex stand alone CD player directly into the amp. The right channel of the amp is worse than the left. I tried a few different routings of the wires and no change. I used a jumper in place of the resistor on the input ground. I haven't tried putting a resistor there. Do you think that might help?
Thanks, Terry
Thanks, Terry
This is something hard to discover...i cannot help
not being at your side, in your home, shoulder by shoulder with you.
Sometimes cables, sometimes routing, sometimes coupling, sometimes ground loop, sometimes supply hum, sometimes coaxial shield broken, sometimes volume potentiometer without ground..needing a ground wire into the metalic case...well..there are so many reasons of that.
Sometimes it is Radio Frequency captured that drains current and them the supply start to produce hum.
It is a matter of search...try and error basis..... hard to find stuff my dear.
I am sorry to know you still have some kind of problem.....at least you are enjoying.... with the hum removed you will enjoy much more because hum has an annoying effect to sonics.. and also produces a bad psychological mood.... a kind of depression.... a sadness.
regards,
Carlos
not being at your side, in your home, shoulder by shoulder with you.
Sometimes cables, sometimes routing, sometimes coupling, sometimes ground loop, sometimes supply hum, sometimes coaxial shield broken, sometimes volume potentiometer without ground..needing a ground wire into the metalic case...well..there are so many reasons of that.
Sometimes it is Radio Frequency captured that drains current and them the supply start to produce hum.
It is a matter of search...try and error basis..... hard to find stuff my dear.
I am sorry to know you still have some kind of problem.....at least you are enjoying.... with the hum removed you will enjoy much more because hum has an annoying effect to sonics.. and also produces a bad psychological mood.... a kind of depression.... a sadness.
regards,
Carlos
I will try and add the resistor. There is no hum without the CD player plugged in and the CD player doesn't cause hum when plugged into my other amps only this one. I used shielded cable from the RCA to the boards, just as I have done with all my other amps. I know it is very difficult to diagnose without being hands on. I just thought someone else may have experienced this and found a solution. I will keep after it until I find the problem and then post back with the solution.
Thanks, Terry
Thanks, Terry
Terry, if the hum is present when the CD player is plugged in I suspect you have a ground loop somewhere:
- Check that the RCA jacks are insulated from the chassis.
- If you are using a single core shielded wire then connect one end of the shield to the ground lug on the RCA and the other end of the shield to the ground terminal on the PCB. Don't connect input ground to chassis ground.
- I like your heavy bus bar for the filter cap ground; however, the single star ground means you will get dirty currents from the first set of caps circulating around your star ground causing voltage fluctuations and a potential source of hum.
- Better to create two ground points: the first between the ground pins (E1) between the first set of caps, the second between the second set of caps (E2). Use heavy guage wire to connect the transformer ground common to E1. That way the 'dirty' currents are resolved as close to the source as possible. Connect the speaker grounds, amplifier board grounds, and chassis ground strap to E2.
Speaking of chassis ground:
If the hum is present only when connected to a certain source, you probably have a ground loop through the inputs and mains wiring. You can build a loop breaker consisting of a some rectifier diodes, capacitor and resistor like the one described by Rod Elliott (http://sound.westhost.com/earthing.htm). Of course you must take care to ensure no other ground points (aside from the mains safety earth, of course) contact chassis ground without going via the breaker - otherwise it defeats the purpose.
- Check that the RCA jacks are insulated from the chassis.
- If you are using a single core shielded wire then connect one end of the shield to the ground lug on the RCA and the other end of the shield to the ground terminal on the PCB. Don't connect input ground to chassis ground.
- I like your heavy bus bar for the filter cap ground; however, the single star ground means you will get dirty currents from the first set of caps circulating around your star ground causing voltage fluctuations and a potential source of hum.
- Better to create two ground points: the first between the ground pins (E1) between the first set of caps, the second between the second set of caps (E2). Use heavy guage wire to connect the transformer ground common to E1. That way the 'dirty' currents are resolved as close to the source as possible. Connect the speaker grounds, amplifier board grounds, and chassis ground strap to E2.
Speaking of chassis ground:
If the hum is present only when connected to a certain source, you probably have a ground loop through the inputs and mains wiring. You can build a loop breaker consisting of a some rectifier diodes, capacitor and resistor like the one described by Rod Elliott (http://sound.westhost.com/earthing.htm). Of course you must take care to ensure no other ground points (aside from the mains safety earth, of course) contact chassis ground without going via the breaker - otherwise it defeats the purpose.
I will try your suggestions. This amp did the same thing when not in a case where the input was just a shielded cable with RCA plug on the end connected only to the input. In that case I had a single star ground to which the grounds from each board, each speaker and the center tap of the transformer all tied together. This is how every amp I have is done. On this amp I was careful to make sure the input RCA's are insulated from the case. The ground wire in the shielded cable is is contact with the shield and only attaches to the ground lug on the input and of course the at the RCA. I have some shielded cable with two separate leads inside. I will try using the two leads and only attach the shield at one end as see if that helps.
You can't do twisted DC power cables because the lugs are on opposite ends of the PCB.
I actually had hoped that attaching the star to earth ground was going to help since I didn't have an earth ground during the original testing and the hum was persent.
The CD player I am using is powered by a wall wart so I doesn't have an earth ground. Also, when doing the original testing, I fed it from a ZUNE which operates from a battery. As soon as both channels were connected there was a hum. I'm out of time for today but I will get to this tomorrow and get back to you.
Thanks, Terry
You can't do twisted DC power cables because the lugs are on opposite ends of the PCB.
I actually had hoped that attaching the star to earth ground was going to help since I didn't have an earth ground during the original testing and the hum was persent.
The CD player I am using is powered by a wall wart so I doesn't have an earth ground. Also, when doing the original testing, I fed it from a ZUNE which operates from a battery. As soon as both channels were connected there was a hum. I'm out of time for today but I will get to this tomorrow and get back to you.
Thanks, Terry
OK Terry, it sounds as though you might have a problem with the actual circuit, and I can't really help you with that unfortunately.
It sounds like you are using two core shielded (microphone) cable. In that case I would connect the RCA ground to amplifier input ground using one wire and then connect the shield directly to the amplifier chassis at a location near the RCA jack. Leave the other end of the shield (near the amplifier board input) disconnected.
It sounds like you are using two core shielded (microphone) cable. In that case I would connect the RCA ground to amplifier input ground using one wire and then connect the shield directly to the amplifier chassis at a location near the RCA jack. Leave the other end of the shield (near the amplifier board input) disconnected.
Does it also hum if you short input signal to input signal ground, at the RCA jacks? Is it only if BOTH channels are connected (or shorted)?
Sometimes (usually?), only humming when input shorted or connected to source would mean that the input signal and ground paths have a gap between them and the enclosed loop area lets the AC fields in the air induce currents in the loop (Faraday's Law). Without anything connected there is no loop so no hum.
If your RCA jacks are isolated from the chassis and your internal cables are good and their ground is routed to the input on the PCB, that would only leave the external cable and downstream on the PCB. Does the input signal trace get separated from the input ground, on the PCB?
The other way to mitigate it would be to make sure that every wire pair to and from the transformer is tightly twisted, all the way to each end, and that none of the pairs ever get separated, even for things like the power switch and fuse.
Sometimes (usually?), only humming when input shorted or connected to source would mean that the input signal and ground paths have a gap between them and the enclosed loop area lets the AC fields in the air induce currents in the loop (Faraday's Law). Without anything connected there is no loop so no hum.
If your RCA jacks are isolated from the chassis and your internal cables are good and their ground is routed to the input on the PCB, that would only leave the external cable and downstream on the PCB. Does the input signal trace get separated from the input ground, on the PCB?
The other way to mitigate it would be to make sure that every wire pair to and from the transformer is tightly twisted, all the way to each end, and that none of the pairs ever get separated, even for things like the power switch and fuse.
I am glad people is helping
I really cannot help.... i do not know what is going on...i am not skilled in such hum as i never had this before.
I have traditional practice...the transformer center tap goes to the chassis..the secondary center tap...also i keep AC wires distant from audio wires.... the transformer is placed also distant and having angle not to send hum to the circuit...i use good shield cables to all audio connections, ... chassis is all grounded, if i have doubts i run wires inter connecting panels, heatsinks and all stuff to the main ground..the center ground...called star ground.
AC and audio never goes in parallel, if needed to join them, they may cross one each other not to induce hum.
Potentiometers metalic cases goes to ground by a wire that is connected to the ground (star ground) and soldered to the star ground and also soldered to the potentiometer metalic case...
Transformer (E/I) goes to ground..the metalic cover is grounded..no insulating material used.
Heatsink is grounded too..if resistance is high because of oxide (aluminum oxide creates almost instantaneously), then i run wires, and long screws into the heatsink with some oil, to insulate aluminum from the air, or it goes creating oxide in less than a minute.
If your mains have ground..then you know the standard procedure.
Because of these basic procedures i have never faced hum...when you never face you do not learn how to cure the evil.
I am such kind of guy that learned things doing...i use to replace a capacitor by a smaller and also a bigger and watch the scope, and watch the simulator and listen the sound...this is he way i have learned... thousands and thousands of hours doing... and listening...all i know was learned by experience..doing things.... so..things i have not faced i have not the knowledge.
Good luck, and thanks to all of you guys, by the helping hand.
regards,
Carlos
I really cannot help.... i do not know what is going on...i am not skilled in such hum as i never had this before.
I have traditional practice...the transformer center tap goes to the chassis..the secondary center tap...also i keep AC wires distant from audio wires.... the transformer is placed also distant and having angle not to send hum to the circuit...i use good shield cables to all audio connections, ... chassis is all grounded, if i have doubts i run wires inter connecting panels, heatsinks and all stuff to the main ground..the center ground...called star ground.
AC and audio never goes in parallel, if needed to join them, they may cross one each other not to induce hum.
Potentiometers metalic cases goes to ground by a wire that is connected to the ground (star ground) and soldered to the star ground and also soldered to the potentiometer metalic case...
Transformer (E/I) goes to ground..the metalic cover is grounded..no insulating material used.
Heatsink is grounded too..if resistance is high because of oxide (aluminum oxide creates almost instantaneously), then i run wires, and long screws into the heatsink with some oil, to insulate aluminum from the air, or it goes creating oxide in less than a minute.
If your mains have ground..then you know the standard procedure.
Because of these basic procedures i have never faced hum...when you never face you do not learn how to cure the evil.
I am such kind of guy that learned things doing...i use to replace a capacitor by a smaller and also a bigger and watch the scope, and watch the simulator and listen the sound...this is he way i have learned... thousands and thousands of hours doing... and listening...all i know was learned by experience..doing things.... so..things i have not faced i have not the knowledge.
Good luck, and thanks to all of you guys, by the helping hand.
regards,
Carlos
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OK, here is what I discovered today. The hum happens when I connect the two input grounds together. There is a very slight hum with nothing plugged in but you have to get close to the speaker to hear it. If you short the input it is dead quiet. As soon as you connect something to both inputs there is a fairly loud hum. I installed the 10R,1W in the input ground. I had a jumper there. That made a slight difference, but not much. I tried shorting the grounds at the input and lifting one of them at one of the boards as suggested by Dr Leach. The hum got worse. I'll try rerouting some of the wires tomorrow.
Thanks, Terry
Thanks, Terry
Oh!.... it seems ground loop.
Elect a center ground, or star ground...connect there your secondary center tape and run your shielded cable again.
Do not forget to ground the input volume potenciometers metalic case.
Star ground is the point of junction of all ground wires and shield from cables.
regards,
Carlos
Elect a center ground, or star ground...connect there your secondary center tape and run your shielded cable again.
Do not forget to ground the input volume potenciometers metalic case.
Star ground is the point of junction of all ground wires and shield from cables.
regards,
Carlos
Attachments
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Hi Caros,
I have the center tap right in the center of the cap bank. It is attached to a bolt that attaches to the ground plate and the bottom of the case. You can see in the picture below. I have highlighted the ground wires. There is no volume control in the amp. I will replace the shielded cables this morning but they are run exactly the same way as all my other amps.
Thanks, Terry
I have the center tap right in the center of the cap bank. It is attached to a bolt that attaches to the ground plate and the bottom of the case. You can see in the picture below. I have highlighted the ground wires. There is no volume control in the amp. I will replace the shielded cables this morning but they are run exactly the same way as all my other amps.
Thanks, Terry
Attachments
I don't know how popular this is, but I have grounded a amplifier this way before,
Using star ground as normal but with a wire that bridges the grounds of both inputs at the sockets, to the chassis at sockets,
And a wire from there to the star ground, and this is only place where star ground is connected to chassis.
Correct me if this is totally wrong
Maybe should connect centre taps to left side of capacitor plate and ask other grounds to star point on right side of plate
Using star ground as normal but with a wire that bridges the grounds of both inputs at the sockets, to the chassis at sockets,
And a wire from there to the star ground, and this is only place where star ground is connected to chassis.
Correct me if this is totally wrong
Maybe should connect centre taps to left side of capacitor plate and ask other grounds to star point on right side of plate
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Common PSU is conected to two amp modules, and input cables shields are than conected again together. Ground loop, sensible to induction form magnetic fields. Transformer somewhere nearby. Result is induced current, causing voltage drop at cables shielding resistance, this is known issue.
Minimize loop area (twist input cables together, place power modules as close as possible) and minimize currents in input ground loop (use correctly 10R resistor separating power ground and input ground).
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