My_Ref Fremen Edition - Build thread and tutorial

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#3,041
OlegSh said:
Dario, the problem is a bit more complicated. In the case of fault RCA connectors and the binding posts tied to amps GND can become live while the amp would still operate fine and speakers would produce sound. For this to happen the live mains wire inside the chassis has to touch the GND of a floating amp. Such fault will sit there for a long time waiting for someone to reconnect the inputs or speaker wires on the working amp and get killed.
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Hi Oleg,

thanks for the instructive clarification. 🙂

But IMHO such a failure is unlikely in a properly built device and it's still no different than most DIY projects, isn't it?

Also, here in Europe at least, should be mandatory to have protective devices (life savers in most cases) like these (already posted in this same thread):

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AKA residual-current circuit breaker and thermal magnetic circuit breakers.
 

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#3,047
OlegSh said:
I've connected the PGND of each amp board to chassis using a ground lift circuit. The chassis is permanently connected to PE.
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Happily, my home has PE ground everywhere, so a floating audio ground amp is no problem. But I am curious about your ground lift circuit. Do you actually put audio ground some DC volts above PE ground? I see tube circuit guys do this for noise reasons and then also include a "ground breaker", usually a thermistor or a couple of diodes in parallel with each other and a capacitor.

Jac
 
#3,048
For the ground loop isolator I used the circuit from the ESP web page. I used the parts I already had in my drawer, just made a small PCB for it. The capacitor lead spacing should be much smaller to more effectively pass RF interference to chassis but I used what I had. The pics of the assembled circuit are here.
 
#3,049
OlegSh said:
For the ground loop isolator I used the circuit from the ESP web page. I used the parts I already had in my drawer, just made a small PCB for it. The capacitor lead spacing should be much smaller to more effectively pass RF interference to chassis but I used what I had. The pics of the assembled circuit are here.
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Excellent solution, it was on my to do list but never managed to try...

Cute and neat PCBs 🙂
 
#3,050
ClaveFremen said:
Wow... a lot of confusion...

I never said not to use PE, the chassis MUST be connected to PE.

It's obvious that the house should have PE in each outlet, at least here in Italy it's mandatory, or EVERY object branched to electricity without double insulation would be potentially dangerous.

The My_Ref it's no different.

What should not be connected (for best performance) to PE are the My_Ref Fremen Edition modules, exactly like My_Ref Rev C. and My_Evo (Evolution Rev. A) since this is a floating amp.

This is a DIY project, not a finished commercial one, we should also not forget it.

Dealing with electricity is always potentially lethal and the utmost care should be taken.

If the amp is encased in a metal case connected to PE, with fuse and insulated output connectors, properly built and connected to an outlet with PE it's perfectly safe, just like the big part of the projects presented here on DIYAudio.
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ClaveFremen said:
This is unnecessary controversy...

You know this project and me pretty well and you already know that I never recommended that madness... can't you simply be constructive and stop this nonsense?
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Not nonsense.
It has been alledged that a poster gave dangerous advice.
You are confirming that it did not come from you.
So who's advice was followed or misinterpreted?

Using ambiguous names when a perfectly unique name exists does not help searching for where the problem came from.
 
#3,051
AndrewT said:
Not nonsense.
It has been alledged that a poster gave dangerous advice.
You are confirming that it did not come from you.
So who's advice was followed or misinterpreted?

Using ambiguous names when a perfectly unique name exists does not help searching for where the problem came from.
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Andrew... my first name and nickname are both in my signature from when I registered my account here on DIYAudio.

While using only first names could be misleading it was pretty obvious that Bas was referring me.

He was referring to the modules, I guess, and not chassis, he's a long time and expert member.

Nevertheless it could be time to add to the project documentation a small section about security even if it's a more general topic.
 
#3,052
OlegSh said:
For the ground loop isolator I used the circuit from the ESP web page. I used the parts I already had in my drawer, just made a small PCB for it.
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I agree, nice solution and nice pcb. The link to ESP is great as well. It is easy to read and a nice discussion of the problem.

Along the same lines, the picture shows another approach that SY likes to use. I think any of these would let someone without PE build something safe.

Jac
 

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#3,053
Yes, the inverse parallel Power Diodes can take a lot of Fault Current if there is an incident.

I have tested such a circuit using the dual parallel Power Diodes inside a 25A Bridge rectifier. It also had a 600mW 10r resistor and 100nF ceramic cap across it. Nether were damaged and the rectifier seemed to survive the "explosion" that happened when I connected it directly across the mains Live to PE, from a safe distance!
 
#3,054
AndrewT said:
Yes, the inverse parallel Power Diodes can take a lot of Fault Current if there is an incident.

I have tested such a circuit using the dual parallel Power Diodes inside a 25A Bridge rectifier. It also had a 600mW 10r resistor and 100nF ceramic cap across it. Nether were damaged and the rectifier seemed to survive the "explosion" that happened when I connected it directly across the mains Live to PE, from a safe distance!
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Cool! I'm happy to learn that someone actually tried it. And that it worked.

Jac
 
#3,055
Hi
The i-pod and My_Ref amp plays beautifuly without any noise.😀
CD player with volume control and RCA signal cables gives background noise.
CD player and preamp have RCA outputs that are connected to the chassis.
The noise from the CD / preamp will then follow the signal to My_Ref amp.
I have tested without PE on power (dangerous) and it makes no difference to the background noise. It may not be ground-loop if I do not have ground
connected? How can I remove the noise from the signal. In my main system, CD / Preamp / Amps- I do not have noise when using XLR balanced cables.
Do you think audio isolation transformers will help. If the noise is already in the signal, will it also be transmitted through a transformer?
Maybe I should bet on transformers from XLR to RCA.
Want to use my old amps for bass (240W bridged) and My_Ref amps amplifiers for mid and high. My DSP uses RCA and my amps use XLR.
I do not know if I can connect this stereo together without noise.
Some tips for what I should do to succeed.😕
 
#3,057
Ordering from mouser presents a few problems, 3 items are out of stock and factory lead times are as high as 21 weeks.

I tried to find alternatives, but there are so many options (and sometimes none)... Would someone provide me with alternatives to these items? It would be much appreciated 🙂

- 571-42437-2-LP
- 647-UFG1E220MDM1TD
- 532-4880M
 
#3,058
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