Discrete Micpre layout. Please view and comment.

[jwhmca]

Hello All,

First of all Thank you all for this Great site.... Truly amazing!

Things you should know about this design:
1. This is a Yamaha discrete OpAmp
2. The "PanelRTN" connector brings back from the Polarity, phantom and Instrument fontpanel switches/input jacks.
3. This is a +-15vdc system .
4. Single sided board
5. I will be using a Output transformer.
6. I plan to mount the "Feedback" for the Opamp on the bottom.

Things that I am concerned/ have questions about:

1. Does the Phantom power supply "routing" pose an issue? Is it okay to have it running so close to the output?
2. Should there be some kind of separation between the "Instrument jack and the mic line?
3. The "VU" send in the +48 connector... is it okay to have it tapped off the output like that? will it cause some strange problems on the output?
4. My grounding scheme...?

Thank you all for your Thoughts!

http://i907.photobucket.com/albums/ac273/jwhmca/Micpre1.jpg

 

[Samuel Groner]

A schematic would make life much easier for us...

Samuel

 

[jwhmca]

True it might... I should clarify: I am only really concerned with layout at this point

 

[jdbakker]

I should clarify: I am only really concerned with layout at this point

That's nice, but without a schematic it is much more of a pain to give you proper feedback on your layout. You're not wiring pieces of metal together, you're connecting nodes of a circuit.

JDB.

 

[strangeandbouncy]

. . . . love and marriage, love and marriage, go together like a horse and carriage . . . .



     . . . . . . . this I tell you, Brother, You can't have one without the other . . . . . . !



   better heed the Samuel, if you want help with this, then any comments about layout are considerably easier WITH the schematic . . . .




      kindest regards,


           ANdyP



              . . . . . . . .           (DoobyDoobyDoo . . . . . .)

 

[jwhmca]

You guys are absolutly right. The only reason I had not included it yet was I was hoping to get answers to very specific questions first... Namely the ones I listed. I'm really not trying to be obstinate...!

I have to finish some details of the actual schematic and transfer some of the design from my Brain to the Capture software.

 

[3nity]

you should move the 100pF and 10K from under the DOA, those Yamaha's DOA's  dont fit any sockets.

 

[jwhmca]

Thanks for the reply!

Those parts I was going to put on the bottom of the board... trace side.

 

[3nity]

if the image view you show is from top the hookup to the DOA is wrong!
V+ should be where Out is,  GND at V-, V- at GND and Out at V+.

 

[jwhmca]

The image is looking up from the bottom... I believe the DOA is correct.

 

[PRR]

I think it is deeply flawed in ways which would be MUCH more obvious on a -full- schematic than a partial pictoral.

Why is Phantom Power flowing to the "PanelRTN" connector?

I don't even see an "Instrument jack".

Where does -48V come and go?

Where is +48 broken?

Why is VR1 so far away from the -In pin? You often want to minimize stray C here; also the -In is a high-gain buzz-sucker.

The "rtn" end of the gain-set network SHOULD come to the low end of the source, in this case the transformer secondary, perhaps the BluBlk lead. As drawn you have inserted all other garbage between the two inputs of the opamp. In particular the OutPut return current and the opamp AB pulses flowing to the 100u caps and the power supply common.

Your output may be OK "near" the mike input. But my eye would prefer to avoid the issue by zoning things: small/sensitive stuff, middle stuff, high-level stuff, at different ends of the board.

 

[jwhmca]

Thanks for the input and I still apologize for the lack of schematic... I see your point, a schemtaic would answer most of your questions/issues.

in the meantime:

"Why is Phantom Power flowing to the "PanelRTN" connector?"

The "panelRTN" feed and return for the Polarity switch.

"I don't even see an "Instrument jack". "

It's on the front panel not part of this layout.


"Where does -48V come and go?"

Not sure what this means...? +48 ground?

"Where is +48 broken? "

Switch on the front panel before it gets to this board.

"Why is VR1 so far away from the -In pin? You often want to minimize stray C here; also the -In is a high-gain buzz-sucker. "

VR1 is a front panel control... not really sure how do get it much closer?

"...SHOULD come to the low end of the source, in this case the transformer secondary"

Umm it does... just in a round about way. Is that what you mean it should not go around the board? I mean they are both at ground.

"In particular the OutPut return current and the opamp AB pulses flowing to the 100u caps and the power supply common."

Where else do they get grounded?

 

[jwhmca]

I understand! Thanks PRR!