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Old 20th December 2017, 09:55 PM   #11
AKSA is offline AKSA  Australia
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Location: Melbourne, Australia
Hi Filipe,

Here's a quick reply for you!

You could use shield AC twisted wire from IEC to Switch (and from switch to transformers as well!) but I do not believe that it will reduce the noise because it's low frequency. If it were 1kHz it would be a big issue.

When you examine the Earth spade on the Maya, you will see that they are connected to the 0V rail reference on the pcb using two 3A back to back diodes. Put another way, current will only flow through this wire to star/chassis earth on the enclosure when a DC figure is outside the insulating window of -0.6V to +0.6V. It will never pass AC signal from the amp 0V reference down to star/chassis/power earth. This is quite intentional, because if you put in a 10R 2W resistor in parallel with the BtB diodes you actually bring mains ground into the amp 0V reference, and it can cause hum. Not always, but often. This system avoids the issue whilst affording protection in any DC arising in the amp (or even at mains ground!).

Shielded twisted pair for the input wire is very similar to balanced input and is good thinking. I do use good quality coax, it is my preference, but twisted, shielded is probably slightly better. Your shield and the neutral wire should both be connected to OUTER on the RCA plug, and at the other end to the neutral pin on the Maya module, as marked. The hot signal wire is then connected, as you have done it, from center point on RCA socket and at the other end, to the HOT pin on the Maya module.

I don't think you can do it any better, and it should be very, very quiet. By separating the two AC power supplies on the modules, with connection of ground only at the DC level (that is, no center tap on the transformer) hugely improves the S/N ratio of the amplifier because connecting a transformer CT secondary point to the 0V reference on an amplifier invites parasitic noise from the transformer directly into the modules. I really do not like using a full wave rectifier across positive and negative rails with ground to CT; it's the usual technique, but it's noisy, particularly if transformers are built with the CT slightly to one side of the 0V midpoint of the secondary.

How is the performance now it's completely run in, Filipe? Have you had a few audiophile friends have a good listen? What do they think?

Merry Christmas to you and your family!

Hugh
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Old 10th January 2018, 09:17 AM   #12
Cvikolak is offline Cvikolak  Slovakia
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Hi Hugh, Hi everyone.

I am a new member and first of all a lot of health in the new year.
I'm interested in this post even though I do not know the Maya module.

Hugh, Hi Hugh, Hi everyone.

I am a new diyAudio Member and first of all I wish a lot of health in the new year.
I'm interested in this post even though I do not know the Maya module.
Hugh, I assume that the maya module is mono (not stereo), I am attaching the basic cabling scheme, it is well understood? It means that Maya has a separate signal ground and power ground?
An externally hosted image should be here but it is no longer accessible. Please upload images instead of linking to them to prevent this.


Hugh, where I can find detailed information about the Maya module? Is selling and has a final price?

Thanks

Jan
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Old 10th January 2018, 10:05 AM   #13
Cvikolak is offline Cvikolak  Slovakia
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.... sorry, basic schema once again
Schéma cabling.jpg
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Old 10th January 2018, 10:59 AM   #14
AndrewT is offline AndrewT  Scotland
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You are showing close coupled/twisted wire pairs for all the inter-module connections. Well done. So many Members here get this completely wrong.

You are showing a weird arrangement for the two solid "EARTH" wires.
What are you trying to achieve?

You have two broken lines from transformer to Safety Earth.
What are these?
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Old 10th January 2018, 12:14 PM   #15
Cvikolak is offline Cvikolak  Slovakia
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Hi Andrew,
I assume that the Maya modules have separate signal ground and power ground (green wires), but I'm not sure it must be confirmed by Hugh.
If this is the case, it's perfect for minimal noise and hum.

Broken lines (green) - this is the case if the transformers have grounded shielding.

Thank for your remarks

Jan
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Old 10th January 2018, 02:10 PM   #16
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by Cvikolak View Post
Hi Andrew,
I assume that the Maya modules have separate signal ground and power ground (green wires), but I'm not sure it must be confirmed by Hugh.
If this is the case, it's perfect for minimal noise and hum.

Broken lines (green) - this is the case if the transformers have grounded shielding.

Thank for your remarks

Jan
If each Power Amplifier has separated Signal Return and Speaker Return, then a voltage referencing connection needs to be made between the two, either on board or across the board. Definitely not to a remote Chassis connection.

If however that remote chassis connection is a Safety connection, then it should not be a long wire across the chassis. It can be a short wire to the chassis adjacent to the PCB terminal.

Grounded shielding sounds like an inter-winding screen.
If you have an inter-winding screen, then the effectiveness of the screen (it is a capacitive filter) depends on the impedance to the Enclosure/Chassis. A low impedance allows the screen to be more effective at higher frequencies. Again a long wire to a remote Chassis connection is not the best way to achieve low impedance. A short wire/strip/braid to the enclosure, adjacent to where the wire comes out of the transformer insulation is better than a long wire trailing across the Chassis.
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Old 10th January 2018, 03:17 PM   #17
Cvikolak is offline Cvikolak  Slovakia
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Quote:
Originally Posted by AndrewT View Post
If each Power Amplifier has separated Signal Return and Speaker Return, then a voltage referencing connection needs to be made between the two, either on board or across the board. Definitely not to a remote Chassis connection.

If however that remote chassis connection is a Safety connection, then it should not be a long wire across the chassis. It can be a short wire to the chassis adjacent to the PCB terminal.

Grounded shielding sounds like an inter-winding screen.
If you have an inter-winding screen, then the effectiveness of the screen (it is a capacitive filter) depends on the impedance to the Enclosure/Chassis. A low impedance allows the screen to be more effective at higher frequencies. Again a long wire to a remote Chassis connection is not the best way to achieve low impedance. A short wire/strip/braid to the enclosure, adjacent to where the wire comes out of the transformer insulation is better than a long wire trailing across the Chassis.
I totally agree with everything..... yes it's an inter-windig screen (excuse my English) ..... the attached schematic is just a principle and it is not a real amplifier. The real construction (design) would be other .....

Attached is a picture of ASPEN Maya module with connecting points .... but it will probably not allow very short connections.

dsf3185.jpg

Thanks

Jan
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Old 10th January 2018, 09:31 PM   #18
AKSA is offline AKSA  Australia
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Hi Jan,

Welcome to the forum! You have done a very good analysis of the pcb...... bravo!

The signal and speaker ground are linked with a 10R resistor on the pcb.

The chassis is isolated from the speaker ground with two back to back high current diodes. This for normal purposes the signal and speaker ground are isolated from the chassis and IEC ground unless there is a voltage appears between them of +/-0.6V. This would then ground the module to the chassis in the event of a failure, without any risk of electrical damage or breach of a safety.

There is a DC voltage protection on the speaker hot wire as well. Should there be more than DC 2V plus or minus an electronic relay disconnects it with a few milliseconds. This is an optodrive on two series high current mosfets. It also waits to connect the speaker at switch on so the amp has settled.

Hugh
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Old 11th January 2018, 01:28 PM   #19
Cvikolak is offline Cvikolak  Slovakia
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Quote:
Originally Posted by AKSA View Post
Hi Jan,

Welcome to the forum! You have done a very good analysis of the pcb...... bravo!

The signal and speaker ground are linked with a 10R resistor on the pcb.

The chassis is isolated from the speaker ground with two back to back high current diodes. This for normal purposes the signal and speaker ground are isolated from the chassis and IEC ground unless there is a voltage appears between them of +/-0.6V. This would then ground the module to the chassis in the event of a failure, without any risk of electrical damage or breach of a safety.

There is a DC voltage protection on the speaker hot wire as well. Should there be more than DC 2V plus or minus an electronic relay disconnects it with a few milliseconds. This is an optodrive on two series high current mosfets. It also waits to connect the speaker at switch on so the amp has settled.

Hugh
Thanks Hugh,

Perfect, you also offered the world a great solution to the hum and noise problems. It can not connect incorrectly.
It sounds like a simple task, but it certainly needed a lot of effort and time.

All the modules I know need different bizarre solutions to remove hum and noise and the result is often not satisfactory, incorrect cable connection will make hum and noise.



P. S.
Hugh, where we find technical information and price? I did not find it on your web site.
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Old 11th January 2018, 09:25 PM   #20
AKSA is offline AKSA  Australia
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Jan,

Thank you for your analysis. Your diagram is perfect with the one exception that secondary #1 AC is connected via two spades on one end of the module and the secondary #2 AC is connected on the other end of the module. You have the connections correct; just the point at which they link up on the module. Because I was bringing AC into a amp pcb, I decided to install the power supplies, two of them positive and negative, at each end of the amp to minimise interference. It has worked out well and is utterly silent. I have found that good quality toroids are important too; one Maya did not present with silent background until I replaced the cheaper chinese toroids with high quality versions, then it was silent as the grave.

Not shown is the signal ground. I have the speaker 0V ground midpoint on the pcb, but the signal ground, the feedback shunt cap and the servo reference cap are all connected to the midpoint 0V spade via a 10R smd resistor. This is very important to ground lift the very sensitive input grounds.

I have been remiss with my website for years and hoping to fix it early this year. I have attached a pdf brochure of the Maya which describes most of the technical features, at least enough to get an idea that it is rather unusual and and evolution rather than a revolution.

Thank you for your continuing interest in Aspen!

Cheers,

Hugh
Attached Files
File Type: pdf MAYA200 BROCHURE.pdf (654.9 KB, 29 views)
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Last edited by AKSA; 14th January 2018 at 05:24 AM.
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