Phantom PCB

[letterbeacon]

With the gain fully cranked I measure (crudely with a VST plugin in my DAW) noise at about -61dBfs. Listening to it I can mostly just hear hiss but if you concentrate you can hear a tiny amount of hum lower in volume than the hiss.  For a SE pre amp with AC heaters and CC resistors, that's not bad I reckon.

 

[ruffrecords]

With the gain fully cranked I measure (crudely with a VST plugin in my DAW) noise at about -61dBfs. Listening to it I can mostly just hear hiss but if you concentrate you can hear a tiny amount of hum lower in volume than the hiss.  For a SE pre amp with AC heaters and CC resistors, that's not bad I reckon.

I would say for ac heaters that is very good.

Cheers

Ian

 

[PeteC]

Hi Ian,

I am just building up a Phantom PSU to use with my P2P REDD47 build.

I am using the circuit you posted here. Thanks for sharing the details.

3 questions if its Ok....

1) can I use a 1watt 4.7K resistor on the adj pin rather than 2watts - I have some 1 watters but no 2watts - I calc the dissipation to be just under 0.5watts.

2) can I use 0.2uF snubbers rather than 0.1u (100nf) - does it make any difference ?

3) I ordered a small supply of TL783s from China but that was several weeks ago  :  so wondered whether I could sub a LM317 or 337 as I'm getting impatient to complete the preamp !

Cheers
PeteC

 

[ruffrecords]

Hi Ian,

I am just building up a Phantom PSU to use with my P2P REDD47 build.

I am using the circuit you posted here. Thanks for sharing the details.

3 questions if its Ok....

1) can I use a 1watt 4.7K resistor on the adj pin rather than 2watts - I have some 1 watters but no 2watts - I calc the dissipation to be just under 0.5watts.

That is probably marginal; it may get rather hot. If you want to play very safe you can use 4 x1 watt 4.7K. Wire them as two parallel pairs then wire these two pairs in series. That gives you 4.7K at 4 watts.

2) can I use 0.2uF snubbers rather than 0.1u (100nf) - does it make any difference ?

the value is not critical 0.2uF will be fine. Just make sure is is rated at 275VAC or the equivalent (400VDC)

3) I ordered a small supply of TL783s from China but that was several weeks ago  :  so wondered whether I could sub a LM317 or 337 as I'm getting impatient to complete the preamp !

The LM337 has a different pin out so I would not advise using it. The LM317 appears to have the same pinout as the TL783 so it is a possible sub. Just be aware that its maximum differential voltage is only 40V whereas that of the TL783 is 125V. This means if you short the phantom supply you could blow the chip.

Cheers

Ian

 

[Andy Peters]

3) I ordered a small supply of TL783s from China but that was several weeks ago  :  so wondered whether I could sub a LM317 or 337 as I'm getting impatient to complete the preamp !

LM337 is a negative regulator, so using it in the phantom-power circuit could be very exciting!

-a

 

[buildafriend]

Not immediately, but I'll need some eventually and I'll check back with you to see if you still have any.

 

[PeteC]

whoops ! I meant LM338 not 337  - but think I'll wait for the TL783s having read up more today.
cheers
PeteC

 

[PeteC]

Reading up op the LM338 ( I have several lying around ) I see that max voltage Vout-Vin is 40v : so as long as I don't short to ground I should be able to use this in my phantom PSU until my TL783s turn up I guess.
I have a 2x25v toroid for 50v input.
Rectified should give me 70.5v into Ian's circuit.

Plan is to use 150ohm, and 5.6K setting resistors to generate c. 48v out.

Anything I'm overlooking ?

Cheers
Pete

 

[ruffrecords]

That should do for now.

Cheers

Ian

 

[PeteC]

funnily enough the TL783's just turned up today !

Ian - do you have any pcb's left from your group buy ?
I have most of the perfboard done for the REDD47 phantom supply - but might be worth having a couple of good 48v boards for future projects.

Cheers
PeteC

 

[ruffrecords]

funnily enough the TL783's just turned up today !

Ian - do you have any pcb's left from your group buy ?
I have most of the perfboard done for the REDD47 phantom supply - but might be worth having a couple of good 48v boards for future projects.

Cheers
PeteC

Yes, I have some left. Let me know your email address and where you are located and I'll send you a Paypal invoice.

Cheers

Ian

 

[Fetkubrick]

Hello!

Does anyone have a BOM for the PCB? So I get components (capacitor, heat sink and more) that fits on the PCB. I´m away for the holidays and the PCB is at home...

 

[ruffrecords]

Hello!

Does anyone have a BOM for the PCB? So I get components (capacitor, heat sink and more) that fits on the PCB. I´m away for the holidays and the PCB is at home...

This heatsink will do for most applications:

http://uk.farnell.com/aavid-thermalloy/6098bg/heat-sink-to-220-202-14-c-w/dp/1213463

As long as the heatsink you choose conforms to this overall cross section size and has 1 inch spaced fixings it should fit on the PCB. The main 4700uF smoothing capacitor is a snap fit 10mm pin spacing type. Depending on how many phantom mics you intend powering you can reduce the size of the heatsink and capacitor. The latest version of the design replaces the 4K7 2W resistor with a 5K6 2W one and the 120 ohm resistor with 150 ohms. The 5K6 really does need to be a 2W type. Everything else is pretty standard.

Cheers

Ian

 

[MidnightArrakis]

This heatsink will do for most applications:

http://uk.farnell.com/aavid-thermalloy/6098bg/heat-sink-to-220-202-14-c-w/dp/1213463

As long as the heatsink you choose conforms to this overall cross section size and has 1 inch spaced fixings it should fit on the PCB. The main 4700uF smoothing capacitor is a snap fit 10mm pin spacing type. Depending on how many phantom mics you intend powering you can reduce the size of the heatsink and capacitor. The latest version of the design replaces the 4K7 2W resistor with a 5K6 2W one and the 120 ohm resistor with 150 ohms. The 5K6 really does need to be a 2W type. Everything else is pretty standard.

Cheers

Ian

Ian: All of the schematics, BOMs, images and whatnot on this thread concerning the "48V Phantom Power Supply" either are not available or just don't work anymore. Is it possible for you to either repost this information and/or send me the information directly??? I would sincerely appreciate it very much. THANKS!!!

/

 

[ruffrecords]

Ian: All of the schematics, BOMs, images and whatnot on this thread concerning the "48V Phantom Power Supply" either are not available or just don't work anymore. Is it possible for you to either repost this information and/or send me the information directly??? I would sincerely appreciate it very much. THANKS!!!

/

Yes, it is a very old thread and many of the links are to my old web site which no longer exists. The phantom power supply design is very old at a time when the documentation I produced was sparse. All there is is what is on the DIY page of my current web site: Custom Tube Consoles - DIY

Scroll down and click on the Power folder. In there you will find its schematic and a print of the PCB layout. That is all there is. All the capacitors should be 100V rated. The resistors are 1/4W except the one labelled as 2W. The PCB Gerbers are also available as you probably know in the OpenSourcePCBs folder.