[raaaf]

Hi all

Great tips already on this forum, but some problems I'm facing I still need some answers to... just in case Jim is on holiday, I thought I better post here.

I'm building a two box Bugle - wooden box for the power supply, metal for the Bugle, (had them kicking around) and I sourced the components locally - but could not find a small potted transformer to fit. The shop suggested using a toroidal one and just wiring it to the PSU board, so that's what I bought (30VA I thought would improve things?).

However - not so simple, for me at least. If anyone can help with my points below I'd be much obliged:-

1. The tranny has no earth lead, as such. Two wires for the 230v primary and four for the +/- 15V and two 'grounds'. Jim's manual mentions the power supply can be floated... so I thought the best way might be to run a separate earth lead from the mains earth in the PSU box through to the Bugle box and earth it at the single earth point on the Bugle board (bypassing the PSU board entirely). Would this be the best idea? Or does the PSU board need an earth too? If so - where? The central hole of the (not there) transformer mount?

2. The tranny outputs I believe connect to the two pairs of holes behind (inside) the long line of holes on the PSU board where I take the regulated outputs from. Would the 'hot' holes for each pair be outer, nearest the caps, and the 'grounds' be the inner ones?

3. Is there any point shielding the DC wire loom connecting the two boxes? (The Bugle box will be ally, the PSU box is wood, so not shielded).

4. On the Bugle board, the signal inputs and outputs... each one has like a triangle of holes with a smaller hole in the middle. I'm thinking the signal connects to the 'point' hole of the triangle, and the earth/returns connect to the smaller holes in the middle, is this right?

Thanks,
Steve

[raaaf]

Hi again,

I have some issues getting the pics off my phone, so thought I'd use these as a reference..

http://www.audiocircle.com/index.php?topic=91702.0

In the first pic - Aerobat has connected the signal leads from the PSU board to the Bugle, but one 'ground' (or signal return) is connected to the mains earth, and the other not connected to anything.

To elaborate on Q1 - my take on how to do this was completely different. I was proposing to take both 'grounds' through to the Bugle, and not earth the PSU board to mains earth at all. So the entire PSU board floats, and it's reference to earth would be through the two signal return grounds coming back from the Bugle. As each rectifier and filter side look symmetrical, I figured each would need its own earth reference?

Also re Q2 - his pic of the transformer looks pretty clear. The two 18v secondary windings are easy here as it's fixed by the transformer pinout. Mine is separate, so it's not. But having more of a think about this - I guess it doesn't matter which secondary wire I connect to which AC input hole pair, as there's no plus or minus at this stage. Just a difference. And the board itself sorts it out once it's been rectified... right?

Thanks
Steve

[jcg0322]

Steve,

I sent a bugle/psu wiring diagram to your email. It covers both 120 and 240 VAC. Let me know if this is what you needed.

Thanks,
Jack

[raaaf]

Excellent, Jack - thanks a lot. That's helped a fair bit for Q1. Q2 and 4 I think I know the answers to... and as for shielding the power supply loom I can always try it without and change it later if necessary. Now I can get my kitchen table back... 

[poty]

I'm building a two box Bugle - wooden box for the power supply, metal for the Bugle, (had them kicking around) and I sourced the components locally - but could not find a small potted transformer to fit. The shop suggested using a toroidal one and just wiring it to the PSU board, so that's what I bought (30VA I thought would improve things?).

All you mentioned is possible, but wooden box for the PS could be not good idea. Power supply is the most polluting device in any system, so it has to have some shielding, which in case of wooden box could be achieved only by some iron pages inside. The second consideration is closely connected to grounding questions and precisely - to safety question. To maintain safety you should make something, which prevents the high voltages to be "presented" on any external part of the device. Usually it is achieved by connecting "ground" wire from mains to metal box-case. In your design - you can connect the wire to any metal part (for example - wiring panel) of your PS.

1. The tranny has no earth lead, as such. Two wires for the 230v primary and four for the +/- 15V and two 'grounds'. Jim's manual mentions the power supply can be floated... so I thought the best way might be to run a separate earth lead from the mains earth in the PSU box through to the Bugle box and earth it at the single earth point on the Bugle board (bypassing the PSU board entirely). Would this be the best idea? Or does the PSU board need an earth too? If so - where? The central hole of the (not there) transformer mount?

Actually - several questions. You can bypass PSU board entirely, but you can't bypass safety measures on the PS. The safety ground from mains must not be detachable! In your case - disconnecting the Bugle device from its power supply leaves the safety ground in air (not connected to everything).  The Bugle grounding, connections and everything else relating to the 2-box layout have already been discussed in the forum (I think, as minimum) twice. The last time it was Ken Willis who built the Bugle in that way. You can ask him directly or find the discussion (Sep 2011). In short:
- connect ground wire from mains near the 230v input to a metal part of the PS case (let's call it "Mains Ground");
- connect the PSU to Bugle Unit by 4-wire cable. The wires are: +15V, Common, -15V, safety ground. In the Bugle case bypass +15V-to-Common and -15V-to-Common with short-legs capacitors to prevent hi-frequency pollution. Connect safety ground wire to the Mains Ground in PSU and to the Ground lug in the Bugle unit.

2. The tranny outputs I believe connect to the two pairs of holes behind (inside) the long line of holes on the PSU board where I take the regulated outputs from. Would the 'hot' holes for each pair be outer, nearest the caps, and the 'grounds' be the inner ones?

The initially specified transformer wiring diagram you can see at http://media.digikey.com/pdf/Catalog%20Drawings/Transformers/ToroidTransform-schemat.jpg

3. Is there any point shielding the DC wire loom connecting the two boxes? (The Bugle box will be ally, the PSU box is wood, so not shielded).

I don't think it is nessesary. If you want to protect Bugle from the external EMI more then, together with already mentioned capacitors, you can use small inductors in series with +15V and -15V lines.

4. On the Bugle board, the signal inputs and outputs... each one has like a triangle of holes with a smaller hole in the middle. I'm thinking the signal connects to the 'point' hole of the triangle, and the earth/returns connect to the smaller holes in the middle, is this right?

The wiring diagram for the specified RCA could be found here: http://www.cui.com/Product/Resource/DigiKeyPDFRedirect/3190/RCJ-01X.pdf

[raaaf]

Thanks for the help - it sounds excellent. Better than it has any right to! Jim worked some magic here I think. A bigger transformer and some better caps, U3 us an LM4562, and it's quite stunning, even with only a few hours on it. Is there some recommended break-in period?

[e1cie1o]

Hi Steve,

Do you happen to still have the document that Jack sent?  He doesn't have it anymore, and it would be really helpful.

Thanks!

-Phil