Disconnected the jury-rigged amp and am now starting to migrate the parts into the new replacement / reclaimed enclosure.
Installed the transformer in the front left of the case.
Ran the two pairs of primaries to the filtered & fused switched AC inlet in parallel, each black/red pair twisted, one pair twisted tighter.
Here are the two pairs of twisted wires side by side in the photo below. I used tie wraps to hold the twisting in place. They are pretty much side by side and you can make out in the photo that one has a fairly long twist and the other is tighter.
Joined the red-to-red and the black-to-black on the same terminal connector. (The wire is stranded not solid core.) Soldered them both on then sleeved with heat shrink tubing. Connected them to the terminals -- the center two terminals are unused and not connected to protective earth, neutral nor hot. Photo below.
I hope it's okay that I left the cable longer than necessary -- I can shorten if need be.
As you can see the purple static wire (or whatever it is) isn't connected to anything. Where should I connect this? I was told not to hook it to the location protective earth is at.
(The little silvery squares on the base and back right side are aluminum foil tape covering unused holes.)
Installed the transformer in the front left of the case.
Ran the two pairs of primaries to the filtered & fused switched AC inlet in parallel, each black/red pair twisted, one pair twisted tighter.
Here are the two pairs of twisted wires side by side in the photo below. I used tie wraps to hold the twisting in place. They are pretty much side by side and you can make out in the photo that one has a fairly long twist and the other is tighter.
An externally hosted image should be here but it was not working when we last tested it.
Joined the red-to-red and the black-to-black on the same terminal connector. (The wire is stranded not solid core.) Soldered them both on then sleeved with heat shrink tubing. Connected them to the terminals -- the center two terminals are unused and not connected to protective earth, neutral nor hot. Photo below.
An externally hosted image should be here but it was not working when we last tested it.
I hope it's okay that I left the cable longer than necessary -- I can shorten if need be.
As you can see the purple static wire (or whatever it is) isn't connected to anything. Where should I connect this? I was told not to hook it to the location protective earth is at.
(The little silvery squares on the base and back right side are aluminum foil tape covering unused holes.)
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Do I need to twist these secondaries tighter? I suppose I could shorten the wire a bit as well since the dc supply board is close.
Also, should one secondary pair be twisted tighter than the other?
(Ignore the black and white wires running from the dc supply board to the back.. these were part of the quick & dirty jury rigged setup I did just to get it going. They will be replaced and perhaps twisted as well? (I'll worry about that when I get there--gonna be a few days before this is done, waiting on heat sink which I'll get Sunday.)
Also, should one secondary pair be twisted tighter than the other?
An externally hosted image should be here but it was not working when we last tested it.
(Ignore the black and white wires running from the dc supply board to the back.. these were part of the quick & dirty jury rigged setup I did just to get it going. They will be replaced and perhaps twisted as well? (I'll worry about that when I get there--gonna be a few days before this is done, waiting on heat sink which I'll get Sunday.)
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I recommend you twist EVERY signal pair without exception.
Well there is one exception: the 3wires from a dual polarity PSU has +ve , zerovolts and -ve. Twist these as a triplet.
Ensure the loops at the terminals are kept as small as possible. This is all about LOW LOOP AREA.
Loop Area increases interference.
Well there is one exception: the 3wires from a dual polarity PSU has +ve , zerovolts and -ve. Twist these as a triplet.
Ensure the loops at the terminals are kept as small as possible. This is all about LOW LOOP AREA.
Loop Area increases interference.
look at the four twisted pairs inside a CAT5 or 6 cable.
They twist the signal pairs to minimise loop area and thus minimise interference.
They also change the twists of the pairs to minimise cross talk between the very closely located signals.
If cross talk between very closely located signal pairs is a concern, then copying this twisting technique should not do any harm.
They twist the signal pairs to minimise loop area and thus minimise interference.
They also change the twists of the pairs to minimise cross talk between the very closely located signals.
If cross talk between very closely located signal pairs is a concern, then copying this twisting technique should not do any harm.
Is the purple/violet wire a screen connection?
If so then it should be connected to the enclosure with the shortest possible tail to minimise the inductive impedance that would allow the highest interference frequencies to pass harmlessly into the enclosure.
Increase the lead length and you increase the impedance to passing that interference.
If so then it should be connected to the enclosure with the shortest possible tail to minimise the inductive impedance that would allow the highest interference frequencies to pass harmlessly into the enclosure.
Increase the lead length and you increase the impedance to passing that interference.
Great idea. However, I've already ordered a replacement piece of aluminum bar that is machined and already cut to the perfect height and width (3/8" thick). Was only $15 for two of these pieces with $10 shipping.
Trying to picture what you mean about "LOW LOOP AREA" and "ensure the loops at the terminals are kept as small as possible". Can you give me some more details so I can properply picture what you are saying?
The purple wire is the purple wire connected to the transformer and is mentioned in this diagram. I don't know what it does. Is this a screen?
An externally hosted image should be here but it was not working when we last tested it.
Okay so ground this wire to the chassis right next to the transformer. Not at a star terminal point potentially shared with CHG (chassis ground) pin on the amp PCB's? THe amp pcb's actually have a pin on each channel that is labeled "CHG" for chassis ground.
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Ok, I'll go straight down to the chassis with it and screw it down there. I need to sand the paint off the chassis first before I screw it down.. need to do the same for the protective earth. The paint is fairly resistant.
So I guess the chassis ground location for the amp boards would be in yet another location near the amp pcb's? (i.e. separate from protective earth and the purple screen wire.)
So much for this "star" thing I hear about.. where they put all the ground wires in one location under a single nut.
The PE wire and the screen are not audio. They do not need to be connected for the audio side to work.
First you must connect all the signal pairs.
Then find what (few) connections are missing on the build compared to the sch. Add in those missing connections. It is usually these missing connections that use a starred reference voltage. One of these missing connections is from Signal Return to Speaker Return. The amplifier needs a common voltage reference for these two sides to know what voltage to send to the output.
So most likely the star will consist of six wires: two signal returns, two speaker returns, and the two CHG labeled holes from the amp pcb's (1 on each board)? There is no CHG (chassis ground) hole on the DC supply board -- DC board has just eight output wires: two each of the four: V-, V+, V- GRND, V+ GRND.
EDIT: Brian from Chimpamp.com (where i bought the boards) has the speaker return, signal return, V+ ground, V- ground traces all connected together to the CHG hole on the PCB for each of the two amp boards. So my star would just be the two CHG wires together on the chassis right between the two amp boards?
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as I said connect ALL the Signal Pairs and then look to see what is missing. That your PCB already has some connections to that CHG may indicate you have no missing voltage references.The CHG could well be your starred voltage reference.
Willy nilly adding extra star connections will inevitably result in duplicated connections and that usually ends up humming/buzzing due to loop/s in signal wiring.
Willy nilly adding extra star connections will inevitably result in duplicated connections and that usually ends up humming/buzzing due to loop/s in signal wiring.
Okay so I'll connect the two CHG holes together to the enclosure base, close to the boards and centered behind them -- sanding the paint first. Again, everything seems to be connected to the CHG hole: signal & speaker returns along with V+ and V- grounds. I see nothing else to solder to.
And that should be all I need.
And that should be all I need.
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Will do thanks!
Thank you guys for building this amp together with me. It's evolving based on what you guys say
With all your awesome help, it's a great learning experience for me and I'll have one nice amp Thanks again!
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Just so I am clear. When you saying LOOPING, is that like a failed attempt at twisting a wire pair together? e.g. worst case scenario being where one wire goes straight while the other spirals around it?
If this is the case, then I need to re-twist both secondary leads to the dc supply board. Because I didn't perfectly twist them, there is some spiraling here and there -- subtle but there.
Also, do I need to twist one secondary pair a tad tighter than the other and run them in parallel -- like I did with the AC inlet dual primaries? One secondary pair is for V+ and the other is for V- in my case.
Additionally, is it reasonable to leave the last inch or so untwisted for easy connection?
If this is the case, then I need to re-twist both secondary leads to the dc supply board. Because I didn't perfectly twist them, there is some spiraling here and there -- subtle but there.
Also, do I need to twist one secondary pair a tad tighter than the other and run them in parallel -- like I did with the AC inlet dual primaries? One secondary pair is for V+ and the other is for V- in my case.
Additionally, is it reasonable to leave the last inch or so untwisted for easy connection?
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