Chassis layout & placement of parts & Trannys HELP!!

I'm rapping up my 8 channel pre-amp & could use some advise.
Original build thread:
http://www.groupdiy.com/index.php?topic=15010&highlight=api
There's not much room to move shit around. My biggest concern is the Toroidals placement. The pics below show a few of my (only) options besides mounting the Toroidal external but that creates another question... "IF" I were to mount external should I mount just the tranny or both (tranny & supply card)
Also, I'd be using a 4 PIN Nutrix to connect the two & I'm not sure what to do with the grounds (Chassis, power & audio)

I'd rather put it ALL in the chassis but worried about Tranny HUMMMMMMmm.
What if any, is the rule with Toroidal placement :?:

#1


This is the same as #1


#2


#3


Thanks,
Kevin

I would attach a steel xfmr cage to the back.
ugly, but who goes back there?

maybe alternate your outputs 90 degrees for less cross talk.

[quote author="CJ"]

maybe alternate your outputs 90 degrees for less cross talk.[/quote]

I assume you mean the output trannys :?:

I'm not sure I understand or if I even have enough room to move the trannys too much. Do the trannys have a sensitive side???

MOST IMPORTANT!
- Does a Toroidal radiate a field & from where?

Any more detailed advise or opinions out there?


Thanks,
Kevin

As CJ suggests, you could turn half of the output transformers 90 degrees, it might help.

Since just about every layout is a bit different, it would say the best way to deal with this is to leave enough loose wire there and experiment with the transformer orientations "live". And yes toroidal transformers emit quite the steady field, to all directions. It's one of its advantages in fact: low non-directional radiation in comparison to 8-10 times stronger directional fields of conventional EI transformers. As was suggested earlier, putting it outside in it's own cage would be a good idea in a tight layout like this.

[quote author="Kingston"]As CJ suggests, you could turn half of the output transformers 90 degrees, it might help.
[/quote]

OK, I'll try.
I wish I made my circuit boards just a hair shorter

[quote author="Kingston"]
And yes toroidal transformers emit quite the steady field, to all directions. [/quote]

I knew they were quieter but never really understood how or why...
GOOD INFO :thumb:


Just so I know, how do you deal with the grounds when mounting the WHOLE PS in an external box?

Thanks,
Kevin

I have four or five pvc 16 ga wires coming off an octal socket,

gnd
+6 heater
+48 phantom
+275 B+

sometimes +12 if needed for tubes/relays

That's cool...

If I use a 4 pin Nutrix

1= GND
2 = 48v
3 = +24
4 = -24

My BIG question is - There is "Circuit Ground" & "Chassis GND" & "Earth" GND.
I'm used to routing everythings being "in the case" and I'm confussed...

Is it OK to join ALL those grounds in the case to ONE GND line going to the Power Supply?

& since I'm using the JLM ACDC supply, it connects the grounds on the PS card to the case/earth thru a 10 ohm resistor... so I guess I can connect the earth (from the wall line in) to the external Power supply & that would connect "earth to circuit" there.?

Then the Chassis to Circuit can connect in the main pre-amp chassis?

RogerFoote wrote:
Just mount the transformers in a seperate box on the floor of your rack... Then your main concern is switching the power to the primaries.

Click to expand...

If your reffering to ALL the OT's... that's WAY too much hasle.
My main concern is the HUM from the WRONG Toroidal placement & now after being brought to my attention, the OT placement.
There's enough space to get them a little further apart (and turn 90%) without the Tranny in there & even more if I move the WHOLE supply outside.

Thanks,
Kevin

Hey Kevin,

What happened to the + rail reg on the ACDC? And where are the 48v pump charge caps? Is that just a dead ACDC youre using to show the layout...?..

Re power transformer, Id take it out of the case for sure, mount it either in a sepperate box or one thats bolted on the back of the case like CJ said. There are ways to minimise the hum inside the box but you can never get it as quiet as you can with an external transformer.

Re grounding, the mains earth wire must go directly (no joins or other interuptions) to the case of whatever box the power transformer is in, be that the same as the preamps or a sepperate box on the floor.

The ground for the power and audio are the same, they all come from the star point on the ACDC, right next to the power terminals. The ACDC's ground is then connected to the case via one of the holes that the standoffs mount in. If youre looking at the board with the regs at the top and the power rail output at the right, its the top right hand hole. That means there is 10ohms (with a 0.1 bypass cap) between audio/power ground and the case, which will help to avoid ground loops.

I would mount the ACDC inside the case and just have the power transformer in a sepperate box. We use 5 pin XLRs as the connector in this circumstance, but anything that isnt a standard audio connector and can handle whatever current you need safely will do. If you have the transformer sepperate theres no need to bring mains ground to the mic pre case.

Also, what CJ was talking about with moving the output transformers 90 degrees is reducing crosstalk between the channels as they will all couple with their neighbours when theyre that close together. Changing their orientation will stop this. However if you cant hear any crosstalk then dont worry about it.


M@

I know it's not done yet, but that is a really nice looking unit. :thumb:

What happened to the + rail reg on the ACDC? And where are the 48v pump charge caps? Is that just a dead ACDC youre using to show the layout...?..

Click to expand...

Yes... It's a dead one (using to show the layout)
I still can't get the 48v section to work right & even thought I'm pretty good at de-soldering, the thru-holes on the ACDC are a PITA... too many ruined traces to count or fix.

----------------------------------------------------

Matt,
I appreciate the detailed responces you give.

I'm very thankful when others reply with advise but it's VERY had to get a FULL grip from their short responces. :wink:

CJ,
I went to Home Depot & found a small metal enclosure (small ceiling fan electrical box) that fits on the back perfectly but it doesn't have a lid & the back of my case is aluminum so...
Is the aluminum good enough between the Toroidal & the pre or should I add another metal plate between the tranny & case :?:

Damn it's tight in there but I was able to get every other OT @ 90% from each other... Thanks CJ :thumb:

Learning about the circuits is WAY easier than the Chassis labor, etc...

Thank you guys VERY MUCH!
Almost there

Kevin :green:

[quote author="MikoKensington"]I know it's not done yet, but that is a really nice looking unit. :thumb:[/quote]

Thanks man.

It all started here:
http://www.groupdiy.com/index.php?topic=15010&highlight=api


Kevin

wow, nice project!

btw, field radiation from toroids is biggest at the wire outlet.
i would take layout #2 and rotate the first row output transformers 90 degrees for less crosstalk in between channels as suggested by cj.
you could also mount the acdc pcb on the same side as the mains transformer.

This is how Chandler do it - as I read it..
http://www.soundonsound.com/sos/jan05/images/chandlerpsu.l.jpg

IEC inlet bottom right.. AC Ground blue wire bolted to chassis next to Inlet
0V line not being bolted to chassis

http://www.soundonsound.com/sos/jan05/images/chandlerpreamp.l.jpg

Power in is the second XLR in the middle (check the second picture)
Disecting the second picture I see (please correct me if I am wrong)
Left XLR - input - white audio ground wire going to middle left green coating then bolted to chassis
Right XLR - output transformer - no ground wires
Middle XLR - DC Power 0V - Black wire going to middle left green coating then bolted to chassis

So with the TOTAL external supply (Grounds!)...

XLR pin #1 can go to the chassis
Chassis can connect to the audio GND (Ov) at the jack that's coming in from the external supply?

Then in the external box:

Earth goes to the case
CT of the Toroidal goes to the JLM 0v in, which in turn connect the 0v & audio GND to the earth ground thru a 10 ohm resistor?

:?: :?: :?: :?: :?: :?: :?: :?: :?: :?: :?: :?: :?: :?:

Does this sound right?
I'm ready to drill my holes this things driving me nuts :razz:

Kevin

I don't know the JLM board.

If your ext pwr supply and preamp are both rack mounted on a steel frame, then there is you chassis/ul/safety ground.

Ground wire going to the preamp is your electronic ground, and that is all you really need.

Try the box on the back, remember not to complete a turn thru the torroid, as we all have learned by now with mounting bolt, and fire that thing up!

I'm having trouble getting the IEC & Toroidal to fit on the back after installing the I/O jacks

... this is why I'm asking about the TOTAL external supply.
The grounds are the only thing stoping me besides the labor.

I do have a small electical box that fits pretty on the back & over the tranny but the IEC AC jack has to be mounted sidways & barly fits between that box & the last XLR jacks.

I'm still working on it but it looks like I may be stuck with the ALL external -
which will NOT be mounted to the rack bars (Like CJ said) chassis/ul/safety ground.


This sucks... all that work & now I'm stuck. Anyone who has followed my original build thread knows. I've learned a shit load though & realized you can't build an API pre out of Yamaha parts... but it still sounds great. :green: Trannys In & Out, 24v rails & DOA...
I wanna track some drums already damnit!

Try the box on the back, remember not to complete a turn thru the torroid, as we all have learned by now with mounting bolt, and fire that thing up!

Click to expand...

I read almost a year ago, you telling someone else about that and I NEVER forgot it. Good lookin out :thumb:

Kevin

OK, How does this look :roll:



The back panel is aluminum & the box steel. Will the aluminum be enough to help sheild or should I go further & add a plate between the Tranny & the back :?:
Also, I know the bolts are too long holding the box... I'll be cutting them down.


Kevin

That looks good, plug it in.

You don't HAve to have both pw supply and pre mounted on a steel rack, but you might want to run an extra ground wire from chassis to chassis.
Experiments like this are easy, connect the wire, dis connect the wire, and see which one hums less.

I would think with that layout youll still have hum problems as your IEC is right next to ch8's in/out jacks and your mains wire has to run right past ch8's input transformer to get to the power switch, which i assume is on the front at the right.

Also the aluminium back wont stop the feild from the power transformer so all youve done by mounting it externally is move it an inch or two further away, and sheilded anything that happens to be behind it in the rack :shock:

Maybe its too late now but Id be mounting the transformer in a completely external box and running it's secondary wires back to the ACDC in the case. Thats what we do with all our pres and we have noooooo hum. Every time weve tried mounting a power trans inside the case there is hum, even with only 2ch of pres.


M@

[quote author="mattmoogus"]Every time weve tried mounting a power trans inside the case there is hum, even with only 2ch of pres.[/quote]

I had a similar experience with the NYD two-bottle two channel version. hum went down more than 20dB with PSU out of the box.

Especially with 8 channels you might seriously want to consider an external PSU. I mean, while recording you might get away with a few preamps humming but 8 channels humming at once might propagate through a mix, creating all kinds of troubles when trying to tackle it in the mix. :wink:

(I'd take the AC to DC out of the unit as well and convert at the external PSU.. just in case, as it might win further 3db or so less noise)