Author Topic: Phantom power for AMZ Multi-Purpose Opamp PCB?  (Read 286 times)

pjohns0

Phantom power for AMZ Multi-Purpose Opamp PCB?
« on: March 27, 2021, 02:11:08 PM »
I have a couple AMZ Multi-Purpose Opamp PCBs and was wondering 2 things:

1. Is there a simple way to power this with phantom power from an audio console?
2. If not, is there already protection built into the circuit to protect it if phantom power is accidentally sent to it? If not, are a couple of electrolytic caps on pin 2 and 3 all that's required to block phantom power from destroying the circuit?

Thanks in advance.

antonis

Re: Phantom power for AMZ Multi-Purpose Opamp PCB?
« Reply #1 on: March 27, 2021, 03:43:51 PM »
C1, C2 & C9 are SIGNAL input DC blocking caps..
(as C5 & C6 are signal output ones..)

C7 & C8 are power supply reservoir (smoothing) caps..
(C7 also provides a Vref AC ground point..)



IMHO, your main concern should be op-amps maximun rated supply voltage (lower than +48V) so you better feed them via a voltage regulator IC..
(like 78XX fixed or 317/350 adjustable series..)
"I'm getting older while being taught all the time" Solon the Athenian..
"I don't mind  being taught all the time but I do mind a lot getting old" Antonis the Thessalonian..

PRR

Re: Phantom power for AMZ Multi-Purpose Opamp PCB?
« Reply #2 on: March 27, 2021, 04:43:03 PM »
...1. Is there a simple way to power this with phantom power from an audio console?...

To do what?

Maybe you really want a Direct Box?
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pjohns0

Re: Phantom power for AMZ Multi-Purpose Opamp PCB?
« Reply #3 on: March 27, 2021, 05:31:19 PM »
@PRR Exactly what I am making with the OPAMP board from AMZ. One of its many stated uses is as a direct box circuit...

PRR

Re: Phantom power for AMZ Multi-Purpose Opamp PCB?
« Reply #4 on: March 27, 2021, 07:44:51 PM »
"The complete information, schematics and modifications are available to buyers of the pcb. A link will be emailed to you upon purchase so you can review the information and collect parts while the board is being shipped to you."
http://www.muzique.com/tech/opamp_multi.htm

I could work it out for you, but Jack knows more than I do.

I do not see where Phantom Power is claimed.
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anotherjim

Re: Phantom power for AMZ Multi-Purpose Opamp PCB?
« Reply #5 on: March 29, 2021, 05:23:05 AM »
Well, I can see the pcb could be used to provide a balanced output.

Deriving P48 power from the XLR isn't so trivial.

The easiest way would be to use an audio transformer. A centre tapped winding from the XLR will have the +power on the centre tap and the 2 outputs drive the other transformer winding. You'd need a resistor and Zener to drop the 48v to suit the opamp chip.

This transformerless solid-state idea might work.
https://sound-au.com/articles/mic-electret.htm#s3#

You won't need R1 through to R5 and C1 and Q1. Your outputs feed C2 and C3. The +power taken from the Zener which can be higher than the 10v.
Croeso i Diystompboxes.

If they didn't hear you then you didn't say it.

amz-fx

Re: Phantom power for AMZ Multi-Purpose Opamp PCB?
« Reply #6 on: March 29, 2021, 08:21:08 AM »
I have a couple AMZ Multi-Purpose Opamp PCBs and was wondering 2 things:

1. Is there a simple way to power this with phantom power from an audio console?
2. If not, is there already protection built into the circuit to protect it if phantom power is accidentally sent to it? If not, are a couple of electrolytic caps on pin 2 and 3 all that's required to block phantom power from destroying the circuit?

I provide support for all of the boards that I sell, and I try to answer all questions about them. I suggest that you write me and I will be glad to help. Here is a short version of the answers you need:

1. You cannot connect it to a mic input and use the phantom power feature for a couple of reasons. The pcb power input is not designed to harvest the phantom power, and there are 6.8k current limiting resistors in the mic input which limit the current below that which the board needs to operate properly.
2. To protect from accidental +48v phantom power being turned on, C5 and C6 should be rated for 63v and I suggest that you use non-polar electrolytic capacitors, which are readily available from Mouser.

Write me if you have more questions: http://www.muzique.com/email.htm

I could work it out for you, but Jack knows more than I do.

Thanks, Paul. You are too kind.

Best regards, Jack


PRR

Re: Phantom power for AMZ Multi-Purpose Opamp PCB?
« Reply #7 on: March 29, 2021, 03:08:05 PM »
Rod Elliott has that core topology with the fairly significant changes needed for Phantom.
https://sound-au.com/project35.htm  "Active" Fig 3

He does not offer a PCB for this project. His #35 "could" be built in the AMZ board, with a LOT of improvisation and off-board wiring.

I know this is a DIY place but.......   You can buy high-feature DIs for under $30; Sweetwater shows a B-ringer 2-channel for $19.
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