[dbasford]

Hi! First of all I should mention that this is my first DIY project, but I'm really excited to enter the DIY world.

I'm building the Bugle and power supply and I've decided to take the 2 chassis approach. I'm learning a lot of this as I go and doing a bunch of research, but still have a few questions and clarifications. I'm from Canada so 115V supply.

1. My biggest dilemma is the grounding scheme for these 2 enclosures and what umbilical to use. What I've got so far is to ground the earth from the power main IEC connector directly to the chassis of the power supply. From the power supply chassis ground go through the umbilical to the chassis ground of the Bugle. Then ground from the Bugle chassis to the ground lug on the Bugle pcb. I think i can combine the two ground inputs on the Bugle pcb together, then run them back through the umbilical, split them back to the 2 ground outputs on the power supply. If this will work or there is anything better let me know.

2. Do I need to ground the power supply board to the power supply chassis in some way?

3.What is a good gauge for the ground hook up wire?

4. Depending on how you recommend I ground this, I could have 3-7 wires in the umbilical. What is a good cable for this? connector? gauge? shielded and/ or twisted pair? ground one end of the shield or both?

5.If I use unbalanced or balanced RCA interconnects, does it change how I have to ground at all? Should these be shielded?

6. I am buying a power switch for the power supply that is illuminated. Its LED can come in 6V/12V/24V/110V/220V ratings. It has a forward voltage of 3V and forward current of 20 mA. With the 30 volt supply on the pcb it looks like i need a 1350ohm resistor. Should i choose the 24v rated led switch, which would have a 1050ohm resistor, then change R3 and R10 on the power supply to 150ohm each to make up the 300 ohm? I am curious why you use 2 resistors here and not just one? or should I get 110V and wire it to the AC some how?

7.What gauge hook up wire for the IEC to PCB connections? twist them and/or shield wrap them?

8. What kind of wire and gauge for the RCA to PCB connections? twist them and/or shield wrap them? What kind of shield wrap do you guys use? Saw someone use coaxial for this, how well would that work?

9. What do you guys use for the chassis ground connection? Just a nut, bolt, and solder terminal?

Well think that's all I got for now. May the karma gods shine on anyone who helps me out as I'm really excited to start building this.

Thanks!

[poty]

Hello,
Not far ago one of Bugle-mate "Aerobat" did this config. You may search the circle and find exactly what he did - it may answer many of your questions. I'll try to present my view on the build:

1. My biggest dilemma is the grounding scheme for these 2 enclosures and what umbilical to use. What I've got so far is to ground the earth from the power main IEC connector directly to the chassis of the power supply.

Right.

From the power supply chassis ground go through the umbilical to the chassis ground of the Bugle.

Right.

Then ground from the Bugle chassis to the ground lug on the Bugle pcb.

Right.

I think i can combine the two ground inputs on the Bugle pcb together, then run them back through the umbilical, split them back to the 2 ground outputs on the power supply.

Deducing that you are speaking about the middle point of the power supply - Right. You can use only one wire to connect to either side of the Bugle power supply and amplifier PCB.
To eliminate hi-frequeny pollution on the umbilical cord I'd prefer to use low capacitanse and short leaded caps (10nF or smaller) at the amplifier end (directly on the connector) between each power supply wire to the ground and use small inductance in series (around 100uH) with the power lines (like in the Piccolo).

2. Do I need to ground the power supply board to the power supply chassis in some way?

It is not nessesary.

3.What is a good gauge for the ground hook up wire?

20AWG I think should be OK for the application.

4. Depending on how you recommend I ground this, I could have 3-7 wires in the umbilical. What is a good cable for this? connector? gauge? shielded and/ or twisted pair? ground one end of the shield or both?

Counting from the above - it should be 4 wires. Good cables for that - like those used for XLR -connections. I think I saw XLR connectors with 4 contacts also. Shielding may be used depending on how many "pollution sources" you have in the nearby environment, but generally it is not nessesary. Grounding would be achieved through the PCB, so additional grounding is not nessesary.

5.If I use unbalanced or balanced RCA interconnects, does it change how I have to ground at all? Should these be shielded?

Balanced RCA interconnects? I may fire long lasting discussions about whether we can use RCA for balanced connectivity, but since you use unbalanced amplifier the conversion should be done before the input RCA connector, so there should be no difference in the grounding scheme.

6. I am buying a power switch for the power supply that is illuminated. Its LED can come in 6V/12V/24V/110V/220V ratings. It has a forward voltage of 3V and forward current of 20 mA. With the 30 volt supply on the pcb it looks like i need a 1350ohm resistor. Should i choose the 24v rated led switch, which would have a 1050ohm resistor, then change R3 and R10 on the power supply to 150ohm each to make up the 300 ohm? I am curious why you use 2 resistors here and not just one? or should I get 110V and wire it to the AC some how?

The power supply PCB uses 2 resistors to achieve some symmetry of the circuit and the ability to use 2 LEDs as indicators. You can use one "half" to power your switch's LED or both - just count the nessesary addition resistance (I prefer to lower nominal current to 10 or even 5 mA, so you can use 24V switch with one half of the power supply without any resistors).

7.What gauge hook up wire for the IEC to PCB connections? twist them and/or shield wrap them?

My choices:
- the ability to sustain the AC voltage by the isolator is more important than the gauge in the application;
- I prefer twisting;
- Shielding is not nessesary in 2-chassis combination.

8. What kind of wire and gauge for the RCA to PCB connections? twist them and/or shield wrap them? What kind of shield wrap do you guys use? Saw someone use coaxial for this, how well would that work?

My choices:
- gauge is not important;
- short distance (2" or less) - twisting, longer distances - shielded (or coaxial) cables;
- I use existing choice of ready-to-use shilded cables in most cases.

9. What do you guys use for the chassis ground connection? Just a nut, bolt, and solder terminal?

Single connectors like those used in the Cornet 2 for example.
I think you should start building as soon as it takes time. Then you can always try one way or other easily as soon as it involves only a small number of external connections.

[dbasford]

Awesome! Thanks for the helpful responses. I checked out what Aerobat did and learned some useful things.

Just a few clarifications and questions.

I am not quite sure where you want the capacitors and inductors. Since I only have one ground wire coming from the power supply(not including the chassis ground wire), i would need just one cap and attach one lead to the negative terminal of say B1 (from the schematic) to the wire coming from the chassis XLR connector? Does which lead you use matter for this cap? Why does a short lead help if you are just attaching a wire to it anyway?

As for the type of cap to use I think ceramic caps are used for this application? I got mouser down to about 500 different ones, what other things should I be looking for? Got any favorites?

For the inductors, would i have the leads attached to TP1 and TP10(from schematic) then wire to their respective connectors on the chassis XLR connector? Direction of the inductor matter?

I know very little about inductors right now, what things should I be looking for to narrow down the vast quantity on mouser? Favorites?

I've seen some posts say you can get rid of c7/ c10 if you are using the power supply and not batteries. Why is this? Should I just leave them be?

With a 4 pin XLR connector, it looks like the shield can act as a chassis ground if I attach it to the shell on each end, and the shell then contacts the chassis connector which is grounded to the chassis through the screws. My question is can I get away with a normal 3 pin XLR now if I use the shield to ground the chassis' together, or do I stick with 4 pin and just not connect the shield to the shells at all, or just one end?

Does the male/ female order matter for the XLR cable? I seems like convention is to do male/ female, but it is cheaper overall to do female/ female cable.

I started looking for a cable to use with my 4 pin XLR connectors and what a nightmare. I can't find a shielded, 4 conductor, 20AWG, cable that I can buy by the foot at all. Any ideas for this? Good sites to buy by the foot that wont set me back 40$ a foot?

So go with the 24V switch and just put wire in R3 and R10 correct?

Any point of getting an IEC power entry module with a filter?

Well that turned into more questions than I thought. Thanks for all your help again!

[poty]

Wow, I triggered a lot of mesh. Sorry for that as soon as English is not my native language.
Changing my answer almost instantly. In the first message I was not clear about the additional capacitors and inductances. I use them in a way of "best practice" - so it is not mandatory at all. In my Cornet 2 - it helps, in the Bugle - maybe yes, maybe no. Bugle uses opamps which is not so sensitive to clear power supply. I like to use the precautions (rather cheap and simple) even in not obvious cases.

I am not quite sure where you want the capacitors and inductors.

First - look at http://hagtech.com/pdf/piccoloman.pdf
On the last page you'll find the schematic. Your attention should be catched by J3 (DC) L1 and C20. J3 is the power supply connector. For powering Piccolo you need only one supply, for Bugle - two. If you repeat the L1-C20 input on both hot (not ground as you mentioned in your questionare) lines - you'll have what I mentioned in my answer.
See the picture in the attachment.
It is possible to solder the capacitors straight on the PCB in place of batteriy holders (in that case - after the L1), but it's still better to solder the "ground side" directly near the place of ground lug on the PCB.
About L1 - you can use something like 652-77F101J-TR-RC from Mouser. The filter to search may have:
- 90-200uH,
- current >50mA,
- small enough to solder directly on the connector,
- low impedance (say < 3 Ohm, which gives us about <0.1V in lost).

As for the type of cap to use I think ceramic caps are used for this application? I got mouser down to about 500 different ones, what other things should I be looking for? Got any favorites?

Be simple for the part. The cap should be:
- small in size,
- 9000pF-100nF of value,
- voltage >50V,
- suitable for high-frequency application (low inductance, switched power supply, RF-type and so on).
Example: 140-50Z2-103M-RC from Mouser.
If you are going to use the second way (soldering directly on the PCB) I'd use film capacitors though, general use one should be enough. You can use the same type as C8, C11, for example: 75-715P200V0.015 from Mouser.

Direction of the inductor matter?

No, it doesn't.

I've seen some posts say you can get rid of c7/ c10 if you are using the power supply and not batteries. Why is this? Should I just leave them be?

No problem, you can save them on place. You have already C3, C6 in the Power Supply section - that is why you can go cheeper and eliminate C7, C10, but it is not rule - just more simple.

With a 4 pin XLR connector, it looks like the shield can act as a chassis ground if I attach it to the shell on each end, and the shell then contacts the chassis connector which is grounded to the chassis through the screws. My question is can I get away with a normal 3 pin XLR now if I use the shield to ground the chassis' together, or do I stick with 4 pin and just not connect the shield to the shells at all, or just one end?

If you manage to connect the 2 chassis by shield - you can go with 3-pin XLR, but I'd use 4-wire under the shield to make the impedance of the connection lower.

Does the male/ female order matter for the XLR cable? I seems like convention is to do male/ female, but it is cheaper overall to do female/ female cable.

Technically there is no difference, so as the only engineer and user of the system you can use any version.

I started looking for a cable to use with my 4 pin XLR connectors and what a nightmare. I can't find a shielded, 4 conductor, 20AWG, cable that I can buy by the foot at all. Any ideas for this? Good sites to buy by the foot that wont set me back 40$ a foot?

I've bought on http://www.partsconnexion.com, but on local market as well. It is possible to use 2 plain (1 or 2 wire) shielded cables (something like this: http://www.partsconnexion.com/product7558.html ) with or without outer shielding like this: http://www.partsconnexion.com/heatshrink_braid_tinned.html In my case to made the cable good looking I use something like this: http://www.partsconnexion.com/heatshrink_braid_poly.html outside the copper mesh.

So go with the 24V switch and just put wire in R3 and R10 correct?

Yes, I think it'll work. Instead of connecting to R10 you can try to connect to the middle point also.

Any point of getting an IEC power entry module with a filter?

I don't think it is nessesary.

[dbasford]

Hey! that schematic is exactly what i needed thanks.

I am gonna pick up this inductor http://ca.mouser.com/Search/ProductDetail.aspx?R=5800-121-RCvirtualkey54200000virtualkey542-5800-121-RC because it has really low impedance. My question about using inductors in the bugle is won't they introduce EMI. Is the amount they produce negligable? Or should I shield them in some way?

For the capacitor I will use the one you suggested, as I could not find ones that were specified for high frequency applications or low inductance. I noticed that in the picolo schematic, it uses 100uF capacitors for this application, where as you suggested to use only up to 100nF. I am curious why such a large difference?

Ok for building the umbilical I have a few more questions.

Should I use 4 20awg wires with a copper braid, then techflex, or two 2 conductor cables with shields built in and techflex to hold them together? Is putting a copper braid over the already shielded wires going to do much?

Should the 2 power wires be twisted together and the 2 grounds, or just twist all 4 together?

If I use a copper braid, do I need to put an insulator like teflon or pvc between it and the techflex?

It is my understanding that shielding is useless unless it is grounded, so I'm going to connect the shield(s) to Pin 1 on the power supply side. Do you think that is ok?

When connecting things like switches and chassis xlr connectors to a metal enclosure, do you use washers between the nut and enclosure, or is just the nut enough?

Thanks again!

[poty]

I am gonna pick up this inductor ... because it has really low impedance. ... using inductors in the bugle ... won't they introduce EMI? Is the amount they produce negligable? Or should I shield them in some way?

The choise is OK. The max electromagnetic field strength of the inductors is in the core and the amount is so small (and even smaller because of the input capacitors) that it won't have any impact on the Bugle.

For the capacitor I will use the one you suggested, as I could not find ones that were specified for high frequency applications or low inductance. I noticed that in the picolo schematic, it uses 100uF capacitors for this application, where as you suggested to use only up to 100nF. I am curious why such a large difference?

While the two circuits look similar they serves different purposes and work with different loads. In the "sliced Bugle" version the capacitors prevent high-frequency pollution from entering power supply for amplifying stages. The electrolytics are bad for this task at the frequencies. The ceramic ones are much more suitable. (more than that - you have already had the electrolytic capacitors on the PCB of the Bugle! ).

Should I use 4 20awg wires with a copper braid, then techflex, or two 2 conductor cables with shields built in and techflex to hold them together? Is putting a copper braid over the already shielded wires going to do much?

20 AWG or thicker should be for ground wire. The supply wires themselves could be thinner.
You can go either way. Even one shielding of the wires is not necessary without strong understanding of its usefulness, so double shielding won't improve anything.

Should the 2 power wires be twisted together and the 2 grounds, or just twist all 4 together?

In this case (DC) I'd not twist them at all.

If I use a copper braid, do I need to put an insulator like teflon or pvc between it and the techflex?

Sometimes it helps. I had to do this, because the copper braid catch on the techflex with its jaggies and the umbilical was rigid. But I don't think you should paid a lot to this (in attention and money). Some inexpensive PVC should be suffice.

It is my understanding that shielding is useless unless it is grounded, so I'm going to connect the shield(s) to Pin 1 on the power supply side. Do you think that is ok?

Why do you think the shielding would be not grounded? As soon as we connect the 4-th wire and the shielding together - it will be connected on both sides to the cases. From the power supply side it will be connected directly to the mains ground wire, so will have the smallest impedance to the "ground".

When connecting things like switches and chassis xlr connectors to a metal enclosure, do you use washers between the nut and enclosure, or is just the nut enough?

It depends. Switches usually don't have internal connection of their body to any electrical parts inside so you can just install them directly. XLR connectors are more difficult. If you use shielded cable it is possible you have to connect the shield to the metallic "shell" of connectors. In that case it may be better to divide shielding connection and grounding connection (shield would be connect to the cases through the "shells", the 4th wire - to the ground stars). Then you do not have to use any washers. If the shield and shell are isolated - then you do not have to use washers either, just connect the shield and the 4th wire together. There are many possibilities...