You are dead right about grounding - the best way to learn about it I've found is to play around and see what sounds best. This is better than any theory and way more fun than reading dry textbooks 🙂
Having another chassis point for your 0V connection (other than the IEC-chassis node) results in the problematic common-mode currents running through the chassis - best avoided.
Having another chassis point for your 0V connection (other than the IEC-chassis node) results in the problematic common-mode currents running through the chassis - best avoided.
Visually, the inside of the box is quite nice. Electronically, it is not.
I would have put the PCB close to the back side of the box with its connexions near the sockets, the tranformer near to the front;
added a separate PCB dedicated to the power supply between the PCB and the transformer;
added an extended axis to the volume control pot.
Connecting the ground of the RCA and/or loudspeaker sockets directly to the chassis (which has a very impedance) can be sometimes very effective again spurious noises.
I would have put the PCB close to the back side of the box with its connexions near the sockets, the tranformer near to the front;
added a separate PCB dedicated to the power supply between the PCB and the transformer;
added an extended axis to the volume control pot.
Connecting the ground of the RCA and/or loudspeaker sockets directly to the chassis (which has a very impedance) can be sometimes very effective again spurious noises.
Hi Everyone,
Here's the lastest regarding the Yulong Amp One:
1) I tried a wire from the braided cable on the inputs to earth ground per Abraxalito's suggestion. No change.
2) I did discover the volume pot needed a wire run from it to that braid. I've never realized the volume got noisy as you turned it up because the amp plays loudly with the volume in a low position. So, I did that.
3) I took an alligator clip wire and poked all around for various ground connections - trial and error. Nothing to report.
4) I REWIRED the speaker leads entirely. I put in much longer leads, that run near the input cable now. And twisted them. I can't say it was a waste of time, but it didn't really change the hum problem. Now all the signal type wires are about as far away from the toroid as you could hope for. By the way, I made sure those binding posts were snug, as well as the RCA jacks while I was in there and touched up any solder joints I thought were needing attention with respect to ground.
5) I think maybe I'll order some higher value capacitors. I've asked before, but nobody responded. They are 3,300 uF now. What value should I get. The are 1.25" high and as I recall they measure 18.25 mm in diameter. Is there a certain cap designation I need to be looking for given these measurements?
6) I don't really know what I'm talking about here, but isn't there some scheme with diodes that might help as in a "normal" tube type power supply. I have one of those inexpensive bridge rectifers in my parts box.
OK guys, thank you again for your continued help.
Mark
Here's the lastest regarding the Yulong Amp One:
1) I tried a wire from the braided cable on the inputs to earth ground per Abraxalito's suggestion. No change.
2) I did discover the volume pot needed a wire run from it to that braid. I've never realized the volume got noisy as you turned it up because the amp plays loudly with the volume in a low position. So, I did that.
3) I took an alligator clip wire and poked all around for various ground connections - trial and error. Nothing to report.
4) I REWIRED the speaker leads entirely. I put in much longer leads, that run near the input cable now. And twisted them. I can't say it was a waste of time, but it didn't really change the hum problem. Now all the signal type wires are about as far away from the toroid as you could hope for. By the way, I made sure those binding posts were snug, as well as the RCA jacks while I was in there and touched up any solder joints I thought were needing attention with respect to ground.
5) I think maybe I'll order some higher value capacitors. I've asked before, but nobody responded. They are 3,300 uF now. What value should I get. The are 1.25" high and as I recall they measure 18.25 mm in diameter. Is there a certain cap designation I need to be looking for given these measurements?
6) I don't really know what I'm talking about here, but isn't there some scheme with diodes that might help as in a "normal" tube type power supply. I have one of those inexpensive bridge rectifers in my parts box.
OK guys, thank you again for your continued help.
Mark
Bigger caps is a good idea but they'd probably not fit on the PCB. Do you want to build up a new bank of caps on a separate PCB (but still inside the box)? If so then if the hum problem is poor layout, doing this might fix it.
Assuming you're game for a new PCB with caps on it, then I suggest adding chokes (or resistors if you're scared of winding chokes) too, making CLCLC or CRCRC.
Assuming you're game for a new PCB with caps on it, then I suggest adding chokes (or resistors if you're scared of winding chokes) too, making CLCLC or CRCRC.
that would be my thought, you have AC coming off your transformer that are not twisted, twisting cancels hum.
There is also a sneaky one you might want to consider. Look for florescent and halogen lights near the amp as well as power cables in the wall. Sometimes just moving to a new location has a dramatic effect on hum. It might sound silly but if anything in the build is acting as an antenna (untwisted wires) there may be some field effect.
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That may be what the hum is from. I had that exact same problem when I built my amp. I moved a ground wire a couple of inches farther away from the toroid and all was silent.😉
Your input shielded cable is 2+shield and the shield is connected on both the sides. Disconnect shield from the RCAs and connect one additional bare wire from the pcb. Also short the two grounds at the RCA.
The speaker wires are too close to the transformer.
Gajanan Phadte
The speaker wires are too close to the transformer.
Gajanan Phadte
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Duh!
You know, you're right. I should have done that while I had it open yesterday. I think that should be my next move.
That's a pretty fundamental thing to power supplies, yes. Twisting the wires.
Mark
You know, you're right. I should have done that while I had it open yesterday. I think that should be my next move.
That's a pretty fundamental thing to power supplies, yes. Twisting the wires.
Mark
Hi Gajanan,
Let me see if I'm understanding you.
1) OK, remove the braid from the RCA's. Then, on the other end where that braided wire connects to the board I am to connect another, bare wire, and run it back to where the braided wire formerly connected to the RCA's?
2) Then what?
3) What do you mean "short the two grounds at the RCA"? Describe how to do this please. (I have some RCA shorting plugs made up.)
4) I have totally re-done the internal wiring running to speaker binding posts. They are longer now, and twisted, and pushed way over towards the input cable.
Thanks,
Mark
You're right about capacitor sizing
Abrax,
Yeah, I was poking around for maybe 6,800 uF caps yesterday and determined they are too large. I could lay them down in the newly acquired space I gained by moving the speaker cabling. If so, I could get even larger caps. It's kind of difficult to locate capacitors with values this large and with the proper voltage. It seems like often the voltages decrease as the values get larger. Which sort of makes no sense to me, but like I mentioned before, I am certainly no expert.
I'm not actually sure how new caps in another location would hook up. I'll have to give it more thought. If I were to do that I'll have to of course pull the board and try to read the traces of how the present capacitors are hooked up. I'm not really sure if I have the expertise to do that right now.
Now, if I do pull that board, what do I have to do with the transistors as far as re-attaching. This is something I don't know too much about. There seems to be a little heat insulator pad on each, and I know sometimes there is a silicone grease applied to transistors. Just re-apply the grease upon re-installation?
I could learn how to wind inductors. Probably something I should know anyway.
Mark
Abrax,
Yeah, I was poking around for maybe 6,800 uF caps yesterday and determined they are too large. I could lay them down in the newly acquired space I gained by moving the speaker cabling. If so, I could get even larger caps. It's kind of difficult to locate capacitors with values this large and with the proper voltage. It seems like often the voltages decrease as the values get larger. Which sort of makes no sense to me, but like I mentioned before, I am certainly no expert.
I'm not actually sure how new caps in another location would hook up. I'll have to give it more thought. If I were to do that I'll have to of course pull the board and try to read the traces of how the present capacitors are hooked up. I'm not really sure if I have the expertise to do that right now.
Now, if I do pull that board, what do I have to do with the transistors as far as re-attaching. This is something I don't know too much about. There seems to be a little heat insulator pad on each, and I know sometimes there is a silicone grease applied to transistors. Just re-apply the grease upon re-installation?
I could learn how to wind inductors. Probably something I should know anyway.
Mark
If you are going to pull the board, consider swapping the transformer to the front of the case and adding an extension for the pot. That will shorten the speaker out leads considerably and eliminate part of the problem. Keep all the new wiring as close to the chassis as possible.
Good idea!
That's an excellent idea. I really had not thought of that. And it fits in with your saying "Arrange whatever pieces come your way", right?
Thanks. That could easily happen should I decide to go that far with a rebuild. These amps really do sound good. I don't know why they never caught on.
Mark
That's an excellent idea. I really had not thought of that. And it fits in with your saying "Arrange whatever pieces come your way", right?
Thanks. That could easily happen should I decide to go that far with a rebuild. These amps really do sound good. I don't know why they never caught on.
Mark
1) you r correct.
Then what. Then it is done. The shield carrying the signal ground sometimes pickup surrounding noise. Normally they do but may not for such a short, in chasis cable.
3) On the picture, it looks like the two outers of the RCA sockets is not connected to each other, i.e. it looks like
.....
Gajanan Phadte
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