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Avondale SE200 Announcement on FB

James Evans said:
Hi Graham, I don't think it's the amp at all, with the pi disconnected and using an old cdp as source it's completely silent. Sadly I don't listen to cds ;) I could maybe try my active pre (Exposure 7) in place of the passive but that adds its own flavour over the passive. With the Qudos I was running the pi directly into it, no pre at all.
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Some faults don't have a single cause - they're caused by an interaction between 2 (or more, $DEITY help us) components. Thus swapping/altering either component can this fix the fault, and it would be easy (but wrong) to claim that this proves the changed component was the faulty one.

A trivial example/metaphor is trying to fix a 6 hole wheel onto a 5 bolt hub. It won't work, and you could make it work by changing either (or even both...) components.
 
One thing that did spring to mind is that as things stand it's really only the power amp base plate that is connected to mains earth, the rest of the panels are all black anodised and screwed together (with black screws), so I was thinking of scraping away the plating at one point on each panel to make a proper connection between them all.
 
Tried it in 2nd system, same issue, regardless of source/pre attached. Hmm, will wait and see once the ETC transformer comes back and it's fully dual mono again.
 
Quick bit of morning debugging… each channel powered in isolation, connected to sources, no noise on each channel. Power them both, noise. Not exactly loud but a buzzing in each speaker that’s not there when powered individually. I have no way of powering both channels individually at the moment. If I remove one channel of the pi the noise vanishes. If I have my hand on the passive pre case and touch the amp case at the same time it feels tingly. Points to an earthing issue I think but I’m not sure where.
 
Another test, removed power from one cap board, so only powering one channel, but kept 0v in place so unpowered channel’s 0v still connected back to tx. Noise remains. That was with source still connected to both channels
 
James,

How is the transformer being earthed? I can only see the one wire leading to the earth terminal - presumably the incoming mains. Are you relying on an earthing connection being achieved through one of the transformer mounting bolts?

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As you can see both transformer earthed back to the incoming mains earth via a 4mm brass bolt through the base plate.

Regards

Richard
 
Hi Richard, I’ve got the encapsulated toroid in the amp at the moment, so no earth connection from that back to mains earth
 
The thing I can’t figure out is why the noise is not present using an old Sony cdp as source. In my 2nd system the noise is present regardless of config (not tried the old cdp there). 2nd system is 1210gr, emerald phono, pi stack, either exposure 7 or passive pre. Doesn’t matter which pre or source, or no source at all, the same buzz is present (again, low level, but there).
 
Quick update, the TX went back to ETC to have a look at. They tightened the frame bolts slightly and gave it another coat of varnish. I popped down there to pick it up and powered up on their bench it was completely silent. Powered up here just sat on the table it is much quieter, still a gentle buzz. In the amp it is noisier again, so I'm going to try and isolate it from the case a bit and see if any of that is the coupling to the case amplifying it.

I do also have a low level mains hum through the speakers with this transformer that I don't have using a Tiger toroid that Graham kindly sent to test with. (totally mechanically silent as well). Not sure what I can about the hum through the speakers other than try to put the psu in another case (high on the can't be arsed scale)

Transformer buzz/hum aside these SE modules are superb, definite step up on the qudos amp. The low level detail retrieval is astounding. I'm hearing albums I haven't listened to for a while for the first time again. Genuinely a totally different experience.
 
James Evans said:
Not sure what I can about the hum through the speakers other than try to put the psu in another case (high on the can't be arsed scale
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Make a cardboard template then cut out a baked bean can and mount in place................ it can't do any harm and must act as something of a shield - it's what I intend doing. If effective I might consider buying a piece of mu-metal.

These SE boards definitely have something don't they???

Regards

Richard
 
Richard Lines said:
Make a cardboard template then cut out a baked bean can and mount in place................ it can't do any harm and must act as something of a shield - it's what I intend doing. If effective I might consider buying a piece of mu-metal.

These SE boards definitely have something don't they???

Regards

Richard
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I do have a spare case fascia (alu) that I stood full length of the case between the tx and amp board on one channel and it made not a jot of difference.

And yes, I'm very impressed so far with the SE200s!
 
If your using a passive pre amp and a source component that does not have a connection between signal ground and earth you will get noise.☹️
solution is to transfer the connection between signal ground and chassis earth to inside the power amp, try it with a piece of wire?
If it works also consider a ground lift switch on the back panel of the power amp, the reason for this is when you plug in a source component like your old CD player which already has this connection you may get a ground loop hum because then you have 2 connections between signal ground and chassis earth, so in this case just lift the switch.

Alan
 
337alant said:
If your using a passive pre amp and a source component that does not have a connection between signal ground and earth you will get noise.☹️
solution is to transfer the connection between signal ground and chassis earth to inside the power amp, try it with a piece of wire?
If it works also consider a ground lift switch on the back panel of the power amp, the reason for this is when you plug in a source component like your old CD player which already has this connection you may get a ground loop hum because then you have 2 connections between signal ground and chassis earth, so in this case just lift the switch.

Alan
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HI Alan, thing is, using the Tiger toroid that Graham leant me, no hum in speakers, totally silent, this whopping great EI TX, hum, it's low level, I need to be stood by the speakers to hear it, but it's there nonetheless. I did try connecting signal ground and chassis earth, either with a piece of wire, or via a 15R resistor, no difference. Maybe i'll give it another go though, just to make sure.

The rasp pi stack is currently running directly into the power amp btw, passive pre is out of the chain (single source, digital vol)
 
Quick sanity check this morning, realised that when I’d tested linking sig 0v to chassis earth previously I’d only done that with the potted RS toroid, which was itself causing noise it seems.

So, put the tiger back in this morning and there was indeed still a bit of hum at the speakers, quick croc clip test joining sig 0v to chassis and hum near enough gone, really quiet now. Have now put a connection from each channel’s sig 0v to chassis earth via a 15r 2w per channel. No noise. Switches can come at a later date (prob never 😉)

Now the test is to see if the wow factor low level detail thing is still there with the tiger powering things.

Fun fun fun
 
Curious to hear what you hear with the Tiger v the noisy lump of iron 😀

Am running the SE200 here as I speak to you with a 800VA Tiger, same except I have put some regs on the front end. Agreed its a nice sounding amp but I'm guessing the when ETI powered its more resolving?
 
OzBrit Audio said:
Curious to hear what you hear with the Tiger v the noisy lump of iron 😀

Am running the SE200 here as I speak to you with a 800VA Tiger, same except I have put some regs on the front end. Agreed its a nice sounding amp but I'm guessing the when ETI powered its more resolving?
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The amp does indeed sound better using the ETC transformer. Frustrating, as it buzzes away and is clearly audible as soon as you walk in the room. I've got foam backed tape on the bottom of it and rubber washers on bottom side, between it and case, and on topside under the nuts, makes no difference. I sit just over a metre from it (single bedroom/office) and listen nearfield, so there's no escape. In quiet passages it's clearly audible. Hum from speakers totally eradicated now though, which is a definite positive.
 
James Evans said:
The amp does indeed sound better using the ETC transformer. Frustrating, as it buzzes away and is clearly audible as soon as you walk in the room. I've got foam backed tape on the bottom of it and rubber washers on bottom side, between it and case, and on topside under the nuts, makes no difference. I sit just over a metre from it (single bedroom/office) and listen nearfield, so there's no escape. In quiet passages it's clearly audible. Hum from speakers totally eradicated now though, which is a definite positive.
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Try wrapping it in thick neoprene foam.
 
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