• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required as is 20 years of participation in forums (not all true). Come here to have fun, be ready to be teased and not take online life too seriously. We now measure and review equipment for free! Click here for details.

Basic question about connecting mains (IcePower DIY build)

hyperknot

Active Member
Joined
Aug 17, 2019
Messages
106
Likes
65
#1
I have a VocoPro Feather Amp FA-500 board, which I bought for its 100% genuine IcePower 125ASX2 board + case + connectors, and because it's been on a good sale at $100 (+ shipping + import duty ended up $175). The official IcePower board itself would be 200+ GBP in Europe.

Out of the box, it sounded downright bad, but it's because of a really bad input buffer board they've included. After using it for a while I finally got to open it and remove everything non-IcePower related (input board, LED, power switch circuit + the fan).

I bought the Ghent Audio cable kit and directly connected RCA sockets to the board, now it's exactly like how a Ghent Audio kit would be. Except for the mains.

I'm puzzled about mains, here are my points (sorry if they are not logical, that's the reason I'm asking here):
- I heard that an electric appliance is either double insulated or single insulated
- Single insulated == 3 plug socket, Double insulated == 2 plug socket or these are different things?
- Single insulated == metal case, double insulated = plastic case?
- The VocoPro amp has 2 plug socket and a full metal body
- Every DIY Class D build I see (Ghent Audio, Nord, Apollon, Audiophonics) uses 3 plug sockets, connecting the earth pin to the case in a sanded point.
- VocoPro is FCC certified ("This product has been tested and found to comply with the requirements listed in FCC Regulations, Part 15 for Class "B" digital devices.")
- The VocoPro has the heatsink around some components (transformers?) directly touching the outside of the case
- The IcePower board in the VocoPro is "suspended" by tiny metal L shaped holders connected to the case by metal screws

Now here is my most puzzling part: when I opened the device, the power switch circuit was extremely fiddle, two legs were directly soldered in a 90-degree angle, just over a tiny point, without any wire. In the datasheet, this board might use up to 6.75 Amps, which I'd guess requires way bigger wires than just soldering two tiny legs in a 90 degree joint. Nevertheless, I've removed the switching circuit and soldered the mains socket's legs directly to JST mains cable. It works now, but there is no way to switch off the amp now, I have to plug the cable every time.

My questions:
- Please help me find the logic between the points I've raised above. We are not talking about a cheap Aliexpress device here, but one from a known Californian company, with FCC certifications, assembled in Taiwan.
- How should I implement the mains connection and the mains switching of the device?
- I'm leaning towards using a 3 plug socket (requires cutting the metal plate somehow) and connecting the earth pin to a sanded part of the metal case. But this is not how this device was designed to operate. Wouldn't this cause any problems?
- How do you add a switch to a device? For example, I like the ones at the front, do I have to bring the live wire to a switch at the front and then back to the power socket? What kind of switch can I use which doesn't look bad (probably metal), yet is safe to be connected to the front / touched by a user?
- Does connecting the case to the earth affect any of the sockets? I'm using RCA sockets where both 0 and live are isolated from the case, is this by design? Would balanced XLR sockets require connecting the 0 pin to the case?
 
Last edited:

stereo coffee

Active Member
Manufacturer
Joined
Jan 2, 2019
Messages
139
Likes
42
#2
I have a VocoPro Feather Amp FA-500 board, which I bought for its 100% genuine IcePower 125ASX2 board + case + connectors, and because it's been on a good sale at $100 (+ shipping + import duty ended up $175). The official IcePower board itself would be 200+ GBP in Europe.

Out of the box, it sounded downright bad, but it's because of a really bad input buffer board they've included. After using it for a while I finally got to open it and remove everything non-IcePower related (input board, LED, power switch circuit + the fan).

I bought the Ghent Audio cable kit and directly connected RCA sockets to the board, now it's exactly like how a Ghent Audio kit would be. Except for the mains.

I'm puzzled about mains, here are my points (sorry if they are not logical, that's the reason I'm asking here):
- I heard that an electric appliance is either double insulated or single insulated
- Single insulated == 3 plug socket, Double insulated == 2 plug socket or these are different things?
- Single insulated == metal case, double insulated = plastic case?
- The VocoPro amp has 2 plug socket and a full metal body
- Every DIY Class D build I see (Ghent Audio, Nord, Apollon, Audiophonics) uses 3 plug sockets, connecting the earth pin to the case in a sanded point.
- VocoPro is FCC certified ("This product has been tested and found to comply with the requirements listed in FCC Regulations, Part 15 for Class "B" digital devices.")
- The VocoPro has the heatsink around some components (transformers?) directly touching the outside of the case
- The IcePower board in the VocoPro is "suspended" by tiny metal L shaped holders connected to the case by metal screws

Now here is my most puzzling part: when I opened the device, the power switch circuit was extremely fiddle, two legs were directly soldered in a 90-degree angle, just over a tiny point, without any wire. In the datasheet, this board might use up to 6.75 Amps, which I'd guess requires way bigger wires than just soldering two tiny legs in a 90 degree joint. Nevertheless, I've removed the switching circuit and soldered the IEC socket directly to JST mains cable. It works now, but there is no way to switch off the amp now, I have to plug the cable every time.

My questions:
- Please help me find the logic between the points I've raised above. We are not talking about a cheap Aliexpress device here, but one from a known Californian company, with FCC certifications, assembled in Taiwan.
- How should I implement the mains connection and the mains switching of the device?
- I'm leaning towards using a 3 plug socket (requires cutting the metal plate somehow) and connecting the earth pin to a sanded part of the metal case. But this is not how this device was designed to operate. Wouldn't this cause any problems?
- How do you add a switch to a device? For example, I like the ones at the front, do I have to bring the live wire to a switch at the front and then back to the power socket? What kind of switch can I use which doesn't look bad (probably metal), yet is safe to be connected to the front / touched by a user?
- Does connecting the case to the earth affect any of the sockets? I'm using RCA sockets where both 0 and live are isolated from the case, is this by design? Would balanced XLR sockets require connecting the 0 pin to the case?
Suggest you read and understand this article in full. https://sound-au.com/articles/mains-safety.htm as it may save your life !!
 

hyperknot

Active Member
Joined
Aug 17, 2019
Messages
106
Likes
65
#3
Suggest you read and understand this article in full. https://sound-au.com/articles/mains-safety.htm as it may save your life !!
Thanks for that article, I went through it. Now with proper namings, that VocoPro amp I bought is a Class II appliance, and I'm very surprised about it.
Reason 1: the internals were definitely not double insulated, some of those joints looked really bad.
Reason 2: every other DIY Class D amp I know are Class I appliance.

The Yamaha WXA-50 (using the same module) is a Class II device, but it looks really well isolated. This one was not.


Also the article recommened that it's a good idea to convert Class II hifi devices to Class I, so I'll go with it. After reading the whole article, I see no reason why converting it to Class I would be a bad idea, it's just a plus safety feature, in case anything wrong happens.
 

hyperknot

Active Member
Joined
Aug 17, 2019
Messages
106
Likes
65
#4
I found the ICEpower 50ASX2's Designer's Manual, and to my biggest surprise, it's pretty much showing the current state of my amp as the reference implementation which was used for the approval phase.

It's designed to be used as a Class 2 device, with direct connections to mains, exactly as I've set it up now.

1578971463859.png

1578971472880.png


So it's good to know that what I have now is actually the reference implementation, I might just leave it as it is and use a cable with an input switch built in.
 
Joined
Jan 8, 2020
Messages
61
Likes
22
#5
The Icepower modules do not need to be grounded, because the input ac EMI filter does not use live to earth filter caps. You can still ground the chassis if other audio equipment on your setup uses 3 prong ac plugs, which may eliminate ground loop noise. But you are safe with the 2 prong plug. From my experience, a single 125ASX2 in stereo will not guarantee very good audio quality. I'd suggest using two 125ASX2 modules in BTL mode, combined with Ghent's RTX phase splitter if you only have RCA pre-outs.
 

AnalogSteph

Active Member
Joined
Nov 6, 2018
Messages
125
Likes
98
Location
.de
#6
Look at just about any big-name Japanese brand mass-market hi-fi component from the last 40 years - the vast majority of them are Class II appliances with metal cases. If done right, this is not an issue. It just takes some more effort than a Class I which just about any idiot can build safely. Is the device in question UL listed or certified by other similar organizations (CSA, VDE, BSI...)? (The FCC is only interested in EMI, electrical safety is assumed at that point.)

As a rule of thumb:
Unbalanced connections: go Class II
Balanced connections: go Class I

When using unbalanced connections, Class II is just about inevitable because otherwise you'd get lots of ground loop issues. Even historically, some power amps were made as Class I, which is fine as long as there is no outdoor antenna, PC or similar involved, all of which tend to have some sort of earth connection.

I'm not sure why you'd want to make a powerful Class D amp with only balanced inputs like the model in question as Class II, but anyway. There are some countries especially in Asia where having a protective earth in your mains outlets is not exactly a given, but I mean, shouldn't any SMPS past 75 W be Class I?

OK, now seeing that the reference design uses unbalanced inputs, it makes more sense. Still, odd choice for this one.

If you were to convert a Class II device with balanced inputs to Class I, you would also have to reroute the shield connection on the input jacks, which now is quite likely to be going straight to signal ground. It should be rerouted straight to chassis instead, as per AES48-2005 - possibly easier said than done.
 
Last edited:

hyperknot

Active Member
Joined
Aug 17, 2019
Messages
106
Likes
65
#8
OK, so I'm trying to put these all together step by step. From what I understand here the important certification was on the IcePower module, the module itself was approvded so it can simply be put in a case which also gets approved?

So Class II design is allowed because all the 6 mounting screws are in isolated points, and the metal heatsink touching the case is on the secondary side, thus there shouldn't be any risk in high voltage going to the case?

IcePower-125ASX2-module2.jpg


1579010836194.png

1579010849773.png

1579011191836.png
 
Joined
Dec 24, 2019
Messages
15
Likes
4
#9
This was very helpful. I built a ICEPower 125ASX2 amp with Ghent Audio case and was experiencing some broad-spectrum noise when connected to my PC using a Dragonfly DAC (it was dead quiet with my phone). Lifting the ground wire inside the case cleaned it up.
 
Top Bottom