3e Audio amps very loud popping noises

[ozlegend]

I have recently built a 6-channel amp for use with DEQX active speakers, Legend's Tikandi Be mk3. They use 3e Audio's amp modules, one stereo 260-2-29A module (shown on the LHS of the attached photo) and four mono 480-1-29A modules (RHS of photo). Between them is a 1200W SMPS with 80,000+ additional reservoir caps.
However when I turn on the amp I get a very large "bang" through the speakers, almost enough to destroy their Be tweeters. I thought it might be the power supply but it measures 47.0 V with no ripple seem through a CRO.
I also get a very large "bang" when I change music tracks with my JRiver MC program. This does not occur when I use another amp with Hypex NCx500 modules.
I measured the DC output of each module and it varied between 10 and 40 mV that does not seem enough to produce the heard effects?
The TI datasheet for the TPA3255 unit on which these modules are built says they have "Click and Pop Free Startup and Stop'.
I queried all this with 3e Audio through the AliExpress website but received no reply, only a refund for the recent stereo module which was good but still leaves with an overall amp that I cannot use - which is a shame because from limited playing of music I quite liked their sound.
I wonder if any one else has had similar problems and/or can suggest a solution?
Thanks in advance!
Rod

 

[MCH]

TI evaluación board for that chip has a voltage supervisor that keeps the amp muted until the working voltage is reached + some delay. This is supposedly to avoid pops at on. At DIY audio you have pages and pages on how to tune and improve that circuit, but it is not something internal to the chip.
I would imagine the 3e audio boards have some sort of version of this, and perhaps it can be "tinned", but I don't know.

Edit: if you are using single ended inputs I would look at that first.

 

[anonyless]

just a thought, have you tried contacting 3e audio on the forum?

 

[solderdude]

Have you tried it without the huge capacitor bank ?
Also the big yellow caps are useless.
I know people think it is the 'audiophile way to go' (huge capacitors and extra decoupling using non-suited caps in parallel) but is not recommended from a technical viewpoint.
Decoupling is good but only where it actually works which is not directly in parallel to reservoir caps.
Any 'decoupling HF' that is achieved is gone because of the wires to the amp boards.
SMPS usually don't like to see high capacitors on its output.

 

[Sokel]

Have you tried it without the huge capacitor bank ?
SMPS usually don't like to see high capacitors on its output.

They probably follow the hypex trend to avoid bus-pumping when playing low freqs.
It's not a universal solution though.

 

[ozlegend]

Have you tried it without the huge capacitor bank ?

Thanks. Yes I originally tried it without the huge capacitor banks (which I have used in the past to improve bass performance) but it had no effect on the huge "hang" problem on turn-on or changing tracks.

 

[ozlegend]

TI evaluación board for that chip has a voltage supervisor that keeps the amp muted until the working voltage is reached + some delay. This is supposedly to avoid pops at on. At DIY audio you have pages and pages on how to tune and improve that circuit, but it is not something internal to the chip.
I would imagine the 3e audio boards have some sort of version of this, and perhaps it can be "tinned", but I don't know.

Edit: if you are using single ended inputs I would look at that first.

I am using balanced XLR connections between the amp and the DEQX HDP4 preamp/processor.
I will see if I can find a solution on diyaudio thanks but it may be difficult/messy to implement with the 5 modules in the 6-channel amp. I would have thought it would be implemented by 3e Audio as part of their design. It also may not change the very large bang when changing between digital audio tracks stored on a hard drive for JRiver.

 

[pma]

What a mess!

 

[solderdude]

Thanks. Yes I originally tried it without the huge capacitor banks (which I have used in the past to improve bass performance) but it had no effect on the huge "hang" problem on turn-on or changing tracks.

Probably a ground wire loop/issue.

 

[ozlegend]

Thanks, I will investigate the ground issue further and advise.

 

[ozlegend]

Probably a ground wire loop/issue.

I could find no evidence of ground loops eg hum etc. However a strange thing has occurred. Now that the stereo amp module is no longer in the system, having been returned with refund to 3e Audio via AliExpress, the "bang" problem has disappeared from the remaining mono amp modules. So perhaps the stereo amp module was a "rogue" and causing the problem? I guess the only way to sure is to order another another stereo amp module to find out.

 

[3eaudio]

@ozlegend

Without any source input connection to the amp , does turn on the amp ,do you still get "bang" through the speakers?

 

[3eaudio]

There may be some misunderstanding on our support team.
you can talk to us via Aliexpress or email,or here to get support from us.

 

[ozlegend]

@ozlegend

Without any source input connection to the amp when I connect the amp to a source, a DEQX DP , does turn on the amp ,do you still get "bang" through the speakers?

Without any source input I get no bang and the amp is very quite through my speakers. However I now get a very loud hum when I connect a source, a DEQX processor/preamp that I use for my 3-way active speakers.
It may be better to try and resolve these problems by private communications via email. Can I have your email address please? This may be easier than going through AliExpress that I find difficult.
Thanks
Dr Rod Crawford PhD(Oxford)

 

[3eaudio]

i remember some other people had similar case regarding Hum noise.
typically it is gound loop between amp and input source and power supply.
maybe you can show more detail on your setup? if there is a diagram will be better

1. what is the power supply?
2. input source model number?

 

[solderdude]

I could find no evidence of ground loops eg hum etc. However a strange thing has occurred. Now that the stereo amp module is no longer in the system, having been returned with refund to 3e Audio via AliExpress, the "bang" problem has disappeared from the remaining mono amp modules. So perhaps the stereo amp module was a "rogue" and causing the problem? I guess the only way to sure is to order another another stereo amp module to find out.

The ground input and 'common' power may connect together at 2 different points (maybe even through the interlink cables) resulting in some small DC current from the amplifier power ground into the input ground of the amp. This can create a small DC voltage over the input ground wire.

Certainly with multichannel amp designs a proper ground wiring is essential, certainly when all amps are connected with relatively long wires from power supply and inputs.
Afterall... all grounds from the power supply go to one point and the inputs also have ground wires that connect to enclosure or via signal inputs together.

 

[ozlegend]

Thanks for the 2 replies above.
I suspect that I have not connected the negative side of the power supply to earth may be the problem - I assumed that this would have been done internally in the SMPS. In previous amps where I have used linear PS the centre 0 of the + and - were always connected to ground.
The 3e Audio manual on their TPA32xx modules is not entirely clear on this - eg J11 and J12 which give the Power Supply Input connections on p8 do not appear on Board Drawing p6.
Does "ground" always mean mains supply "earth"?

 

[solderdude]

There is safety ground (physical earth via 3rd prong in the mains outlet).

There is the enclosure. When it is possible some internal voltage (opposite physical ground/safety ground) in some fault condition can make contact with a conductive chassis/enclosure that can be touched then the enclosure must be connected directly to safety ground (no components in between.

Then there is 'signal ground' also called 'common' or 'return' which is usually either one of the power supply rails (when using a single power supply) or the center-tap of a dual power supply.

When mounted in a metal enclosure that signal ground (at one point only) can be connected to the chassis.
Either directly (as is often the case) which makes the amp more resistant for outside interference/hum.
Or (what one sees in some pro products) with a switch. This is called ground lift.
Another option is to connect the signal ground to the chassis via a resistor (with a capacitor in parallel to it).

A problem can occur when for instance the power supply is connected to one side of the board (and the 0V line is connected to the chassis) and the input 'ground/common/return' is connected via wires to an input where the 'ground/common/return' is connected to the chassis as well (but at another point).
When the mains ground is also connected to the chassis this is asking for problems (hum, etc.)

 

[ozlegend]

Thanks. I found the SMPS 0 /-ve output was not connected to earth so temporarily made this connection and the gross hum disappeared. To do it permanently I had to disconnect quite a lot of connections such as speaker output wires that I had kept short so tomorrow moring Oz time I will reconnect everything to see how it sounds with inputs and speakers connected,

 

[charlielaub]

I would estimate that this is all resulting from how you have wired your input connections. Keep in mind that the hot or cold leads of a balanced interconnect do not necessarily have to behave well on their own. Rather they only need to behave THE SAME WAY but with opposite polarities. So these pops that you are getting should be almost noiseless if the balanced interconnection is properly wired and used. I didn't see details about what source equipment is connected to the amplifier, but this is also a potential source of problems like hum and pops, etc. Never use a single-ended-to-balanced adapter that does not use a transformer or have active circuitry to make this conversion as that is just asking for trouble. Whatever is driving the interconnect leading to the amplifier should be a balanced source. If you need to connect unbalanced equipment to the amp, then use a proper converter such as a Henry Matchbox (good) or Samson S-convert (alas, discontinued), etc.

I can make out that you are using balanced inputs, and there are three wires from the input jacks leading to EACH amplifier board, including the ground connection. This has formed a lot of ground loops within your amp chassis. According to what I have come to understand about balanced interconnects between equipment, it is wrong to connect the ground lead anywhere but to the chassis right next to the input jack. Unlike single ended connections for which the ground is the current return, the hot and cold leads of a balanced interconnect form a current return path to the source equipment themselves. These are the only wires that should connect the source and receiver balanced circuits. The function of the ground lead of the balanced interconnect is to connect the chassis of each equipment together. Also, the chassis of both source and receiver components should connect to the power supply ground at exactly ONE POINT. This is typically done right next to the power inlet where the chassis ground wire is also connected, with all wires terminated with ring terminals that are stacked up on a machine screw, and a toothed washer against the chassis metal. A nut tightens everything together and the toothed washer bites into the chassis metal. This forms a star ground system and minimizes loops that can pick up... HUM AND NOISE.

So, the corrective fix I think you should try is:
1. Remove all the ground connections between balanced input jacks and amp boards.
2. Connect the ground tab of each input jack to the chassis right next to it
3. Connect the chassis at one point only to the power ground. Let's call this the start grounding point.
4. Run one wire only from the star grounding point to the power supply ground
5. For each amplifier module, run one wire between each amp module PCB and the power supply ground point (not to the star ground on the chassis)

See the attached articles for detailed info about how and why to wire a balanced interconnect this way.