I have not cleaned the boards yet as you can see from the bypass cap at the backside. It bypasses the 10uF green nichicon (if it makes a difference I don't know but hopefully it will not harm anything). Think I will buy some Isopropanol and try to clean the stuff off. I took some care not to touch the fine wires when wrapping the tape around the Edcors. I also checked afterwards that there was still connection and no shorts.
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@TungsenAudio - you are too gracious. Thank you very much. I also appreciate the extra information about how you've chosen and used transformers in your applications. I had settled on the AS-4218. When reading previous posts and your posts noting that the case was required/recommended, I had it all ready to move to the cart, but the case is currently out of stock. So, I looked for the "next size up"...
The short version is - I goofed AGAIN.
After your kind reply, I went back to the web site and read more carefully. You nailed it. I in-fact was looking at the AN-5218 and AN-6218. While the ANs specifically note "audio" in their spec sheets, it clearly shows they don't have the "static shield" from the AS line. This is exactly the same thing that threw me while trying to determine how to find properly rated resistors within a manufacturer across product lines. I did not notice a subtle change in naming convention and was looking at incorrect spec sheets. The devil is in the details.
Once again, thank you!
The short version is - I goofed AGAIN.
After your kind reply, I went back to the web site and read more carefully. You nailed it. I in-fact was looking at the AN-5218 and AN-6218. While the ANs specifically note "audio" in their spec sheets, it clearly shows they don't have the "static shield" from the AS line. This is exactly the same thing that threw me while trying to determine how to find properly rated resistors within a manufacturer across product lines. I did not notice a subtle change in naming convention and was looking at incorrect spec sheets. The devil is in the details.
Once again, thank you!
There are a couple other (perhaps crazy) things that I like to do with my transformers:
1) Run the mounting bolt through a pair of rubber stoppers that are wedged in the center hole of the toroid. The transformer is held in place by compressing the stoppers so they grip the inside of the transformer and dampen potential vibration. I don't use the steel plate over the top when mounting with rubber stoppers.
2) Mount the transformer to a 3/8" thick slab of acrylic, which is then bolted to the bottom of the chassis. I regard this as especially important when mounting a pair of transformers inside the same chassis. The combination of aluminum and acrylic is effective at damping line frequency vibration. The acrylic slab lets the main bolt be a blind mount, rather than sticking out the bottom of the amp.
These techniques aren't viable or recommended when using the factory steel case around a toroid. It's best to let the steel case be in electrical contact with the chassis to form a Faraday cage as well as a magnetic shield around the transformer.
1) Run the mounting bolt through a pair of rubber stoppers that are wedged in the center hole of the toroid. The transformer is held in place by compressing the stoppers so they grip the inside of the transformer and dampen potential vibration. I don't use the steel plate over the top when mounting with rubber stoppers.
2) Mount the transformer to a 3/8" thick slab of acrylic, which is then bolted to the bottom of the chassis. I regard this as especially important when mounting a pair of transformers inside the same chassis. The combination of aluminum and acrylic is effective at damping line frequency vibration. The acrylic slab lets the main bolt be a blind mount, rather than sticking out the bottom of the amp.
These techniques aren't viable or recommended when using the factory steel case around a toroid. It's best to let the steel case be in electrical contact with the chassis to form a Faraday cage as well as a magnetic shield around the transformer.
Antek Transformer gave me pause when I received my first one.
Being nothing near .. as visually neatly built as a Torroidy for example.
But they have worked Flawlessly... with Zero noises.
Unlike My old Dynaco or Sony ones which humm like a Telephone Pole mounted Transformer.
Distracting to invent problems.. to 'fix'.
Being nothing near .. as visually neatly built as a Torroidy for example.
But they have worked Flawlessly... with Zero noises.
Unlike My old Dynaco or Sony ones which humm like a Telephone Pole mounted Transformer.
Distracting to invent problems.. to 'fix'.
I hadn't heard of the manufacturer Antek until Nelson Pass recommended them for one of his projects. Since then I've used Antek transformers in many pieces of DIY gear, and I have been extremely pleased with every one of them. Antek is now my number one preferred supplier. It's a delightful coincidence that both Antek's warehouse and my residence are in the US, so the (domestic) shipping costs are lower.
poseidonsvoice - I used 1/8" thick X 2" wide extruded aluminum I had laying around. I bent it to 90' in a vice and then drilled a hole for the mounting bolt. I wasn't happy with how high it ended up on the bracket, so I drilled another hole to lower the transformer. The bottom of the bracket is held by 2 - 10mm x1.0 bolts and lock nuts.
Strong enough to hold the ANTEK transformer and metal shield without any sag over time or vibration.
Strong enough to hold the ANTEK transformer and metal shield without any sag over time or vibration.
@TungstenAudio - Again, Thank You! Copied and pasted into learning notes for future projects or mods to this project. I had no idea that the steel enclosure (when used properly) formed a Faraday cage.... That is cool. Maybe I can put a certain someone's cell phone in it. 
I did consider and will still consider both of the concepts you shared. At this moment, I think I'm going with the Antek steel case. Even though it's a tad over my head, I think I understand that the Edcors can be sensitive to EMI from the power transformer. The Antek shielded design (AS line) + steel case + using a higher power transformer + physical part separation in a bigger case and thoughtful layout all seem to contribute to improving the potential outcome. Since the Edcor gets talked about a lot as contributing to the sonic character of the amp, I'm trying to wrap my head around how to best work around that consideration. Mainly, I'm going to steal others's ideas with abandon.
Since, I'm not sure I'll be comfortable playing with the 3M tape or Mu metal at this point. I'm focusing on all I can do on the power transformer side to lower the potential for problems.
I got a few extra Edcors in case I want to try shielding them after I get the amp working properly (and because shipping is more expensive than the part). Top of mind was a post or two mentioning that those very, very small wires are susceptible to damage if mistreated. I'm a clod, and I'd be bummed if I took my working amp out of commission by trying to "fix" something that was never broken. But..... I know myself too well. I'll try the mu metal and/or tape at some point. Also, at some point, I'll try to understand why Mr. Pass had an intern to sort them and the simulation Mark and another gentleman were discussing. That will lead me to want to "pick the best ones". It's way outta my pay grade for now. It can all come after I get a working amp.
Edited to add thanks to @Bare, Elwood, and Mark for additional thoughts that got posted while I was typing my novel.
I did consider and will still consider both of the concepts you shared. At this moment, I think I'm going with the Antek steel case. Even though it's a tad over my head, I think I understand that the Edcors can be sensitive to EMI from the power transformer. The Antek shielded design (AS line) + steel case + using a higher power transformer + physical part separation in a bigger case and thoughtful layout all seem to contribute to improving the potential outcome. Since the Edcor gets talked about a lot as contributing to the sonic character of the amp, I'm trying to wrap my head around how to best work around that consideration. Mainly, I'm going to steal others's ideas with abandon.
Since, I'm not sure I'll be comfortable playing with the 3M tape or Mu metal at this point. I'm focusing on all I can do on the power transformer side to lower the potential for problems.
I got a few extra Edcors in case I want to try shielding them after I get the amp working properly (and because shipping is more expensive than the part). Top of mind was a post or two mentioning that those very, very small wires are susceptible to damage if mistreated. I'm a clod, and I'd be bummed if I took my working amp out of commission by trying to "fix" something that was never broken. But..... I know myself too well. I'll try the mu metal and/or tape at some point. Also, at some point, I'll try to understand why Mr. Pass had an intern to sort them and the simulation Mark and another gentleman were discussing. That will lead me to want to "pick the best ones". It's way outta my pay grade for now. It can all come after I get a working amp.
Edited to add thanks to @Bare, Elwood, and Mark for additional thoughts that got posted while I was typing my novel.
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If you have many Edcors you could try to match a pair of them. I have four of them and I selected two where the coils was closets (DC resistance (ohm) and induction (H)). The correct way is probably to measure the transfer curve.
To get a silent power transformer I select an oversized (500 VA pr. channel in my case). Then I hope most magnetic flux stay inside the core and as it only runs idle all time it will be silent.
To get a silent power transformer I select an oversized (500 VA pr. channel in my case). Then I hope most magnetic flux stay inside the core and as it only runs idle all time it will be silent.
Is the grounding of the EDCOR cover for noise or safety reasons? I wrapped my cover in kapton tape for safety reasons, but didn't ground it. Would it be better to ground it?
I am running a single Antek 300 VA in my stereo M2. I don't hear any noise issues. I don't know anything about electronic design, so please bear with me. Would 2 x 500 VA be considered over-specified for the M2X (or M2)? Are there any other advantages to putting a larger transformer in, if noise isn't an issue?
Noise. The shield has to be connected to something to have a ground reference. But try it both ways.
Perfect.
Yes
No
In early posts, 6L6 suggests testing the daughter boards before installing:
"If you decide to solder your Austin boards anyway, please make sure you’ve got adequate lab equipment to, at the very least, apply the requisite ±25V DC power supplies and measure the supply current. If you’ve got an incorrectly assembled board, it’s vastly preferable to have it catch fire on your lab bench, near your lab fire extinguisher, rather than inside your M2X amplifier."
So I hooked up the three sets I've completed so far with V+ to pin 3 and ground to pin 1.
Results:
Tucson = 0 mA current draw
Mountain View = 10 mA current draw with the LED illuminated
Austin = .25A
Austin has me worried, so I left it connected for 5 minutes with no change to the current draw or voltage (+24vdc). No smoke, flames or sparks, although the transistors are hot to the touch after 5 minutes. Both boards have the same current draw and transistor heat after 5 minutes of testing.
I'm going to recheck the transistor placement, although I copied the pin placement off the datasheets on Mouser and Digikey (I checked both websites for each tranisitor) and used it to place on the circuit board.
Has anyone else tried testing the daughter boards on the bench, if so, are my results good or bad?
"If you decide to solder your Austin boards anyway, please make sure you’ve got adequate lab equipment to, at the very least, apply the requisite ±25V DC power supplies and measure the supply current. If you’ve got an incorrectly assembled board, it’s vastly preferable to have it catch fire on your lab bench, near your lab fire extinguisher, rather than inside your M2X amplifier."
So I hooked up the three sets I've completed so far with V+ to pin 3 and ground to pin 1.
Results:
Tucson = 0 mA current draw
Mountain View = 10 mA current draw with the LED illuminated
Austin = .25A
Austin has me worried, so I left it connected for 5 minutes with no change to the current draw or voltage (+24vdc). No smoke, flames or sparks, although the transistors are hot to the touch after 5 minutes. Both boards have the same current draw and transistor heat after 5 minutes of testing.
I'm going to recheck the transistor placement, although I copied the pin placement off the datasheets on Mouser and Digikey (I checked both websites for each tranisitor) and used it to place on the circuit board.
Has anyone else tried testing the daughter boards on the bench, if so, are my results good or bad?
So, I would like to do this, but also would like to build a dual mono supply. If the power supply is in a separate case, would I still need some capacitance for smoothing in the case that has the M2 boards?
Looks like everyone is going crazy with shielding/covering/grounding the Edcors on the M2X. I have not done anything for Edcors just they are little farthest as Mark/6L6 suggested in the build thread from the power transformer and closer to the back panel. Now among all the amps that I have built surprisingly this is the most hum free one
So I would suggest that may be you need to try first power up the amp and see if the Edcors really need all the dressing up if you get the hum or hiss. If you are lucky like me then their is no need to perform any more tweaks.
So I would suggest that may be you need to try first power up the amp and see if the Edcors really need all the dressing up if you get the hum or hiss. If you are lucky like me then their is no need to perform any more tweaks.