Mezmerize DCB1 and VSPS phono 1 transformer

[pizzacat666]

Hi, I am a beginner. I have an Antek AS-1215 - 100VA 15V Transformer with dual 15v secondaries and 2 bridge rectifiers (KBPC2504T) ready. I want to use this transformer to power both the DCB1 preamp and the VSPS phono pre from RJM audio. Problem is the VSPS phono preamp calls for rectified dual rail DC while the DCB1 wants center tapped AC. How can I accomplish this? I have attached schematics for all these.

I know I can't obtain +Vcc - 0 - -Vcc for the VSPS using the bridge rectifiers if I first connect the xformer secondaries in series for the DCB1. I think I need to connect the secondaries to the bridge rectifiers first and then I can power the VSPS. I think I can then connect the DCB1 to the rectifiers as well. The rectified DC power will then go to another set of bridge rectifiers onboard the DCB1 pcb--will this be a problem? My only thought is one of the diodes in each pair will be constantly blocking DC and could get too hot?

Thank you

 

[pizzacat666]

No one can tell me if it's ok to feed DC to the AC input of the DCB1 board?

 

[Salas]

Hi

Don't mix AC configurations. Either buy another transformer or share DC from one rectifier scheme to the reservoir capacitors of those two units.

 

[Salas]

In other words, in your last drawing don't go to AC_in of DCB1 but to its big capacitors pins underneath the board.

 

[pizzacat666]

In other words, in your last drawing don't go to AC_in of DCB1 but to its big capacitors pins underneath the board.

Thank you so much for replying! I understand exactly, but want to make sure I have this right. I drew where I think the supply wires should go.

 

[stocktrader200]

DC will not affect the AC input. I would use a small 5 -10Va 15Vac torroid for this project.

 

[pizzacat666]

DC will not affect the AC input. I would use a small 5 -10Va 15Vac torroid for this project.

Thank you for responding. I decided to go with the 100va because the original BOM recommends a 50va, but I plan to run slight hot rod with 9ohm Rset resistors and also want to power an additional phono board from the same power supply.

Plus when you are paying $10 tax and shipping for xformer from Antek I would just as soon pay $3 more for the 100va over the price of the 50va one.

 

[Salas]

Thank you so much for replying! I understand exactly, but want to make sure I have this right. I drew where I think the supply wires should go.

Correctly wired. Those capacitors remain of course. Though you will not need the DCB1's bridge diodes anymore. They do no harm if they remain when external raw DC is fed to the reservoirs, but they do no work either.

 

[pizzacat666]

Well my LSK170bs from NAC got here today so I finished the preliminary build. Currently using the onboard rectifiers since I am still waiting on the VSPS pre to come. Thought you might want to see my "trashy" temporary chassis. I'm a little sketched out but its better than nothing.

Those heatsinks make good hand warmers!

 

[PRR]

You want to send that photo to DigiKey.

Also FYI: "Your item was delivered at the front door or porch at 12:30 pm on September 17, 2020 in BELLINGHAM, WA 98225." (So I guess that's not the box for the LSKs.)

 

[Ketje]

The problem is not the supply, your solution by puting DC on the AC-in will work, but the common ground.Can be a source of hum.
Bettter use two supplys, like that you can have only one ground connection between preamp and buffer/selector.
Mona

 

[pizzacat666]

You want to send that photo to DigiKey.

Also FYI: "Your item was delivered at the front door or porch at 12:30 pm on September 17, 2020 in BELLINGHAM, WA 98225." (So I guess that's not the box for the LSKs.)

Yeah that chassis is for my cookie monster. The lm1875 amp built on an old cookie sheet and using a peanut butter jar to hold the power sockets. It will be an F5 once the pcbs are back in stock in the store.

 

[pizzacat666]

The problem is not the supply, your solution by puting DC on the AC-in will work, but the common ground.Can be a source of hum.
Bettter use two supplys, like that you can have only one ground connection between preamp and buffer/selector.
Mona

Ok that is a good reason to get another transformer, but I will see if I notice a hum problem first before I spend the money and lay out space in a chassis for another transformer. Was also thinking of setting up a micro to control volume and inputs and a push button start which means I need 5v supply and possibly yet another transformer.

 

[stocktrader200]

PRR , you got that info from the string of numbers on the digikey box?

 

[pizzacat666]

PRR , you got that info from the string of numbers on the digikey box?

Yeah, how did you know so much ?

 

[pizzacat666]

I finally got back to this project over the holiday. I wired the phono pre using the diagram on this page
safety - Is this the correct way to wire my transformer? - Electrical Engineering Stack Exchange

So center tap from transformer goes straight to common on the phono preamp board. The other two taps from the transformer go to a full bridge rectifier, and I get plus/minus 15V off that bridge rectifier for the phono preamp.

The same transformer is powering the Mezmerize DCB1 pre.

There is no audible hum at reasonable volume. When I crank it up above where I would ever listen, you can hear some annoying hum with no music playing. I will keep checking for hum since there is common ground and it could start being an issue but so far so good.