The 9 VAC devices may operate on 12 to 13 VDC without problems, because it's LIKELY the first thing that happens is the voltage is full-wave rectified. It's not always the case though. I have a modem that will and one that won't. The one that won;t also has LEDs that change color and probably uses the AC to change to yellow.
Also note that 9 VDC does not come from 9 VAC. If you DON'T regulate (not recommended) you would need about 7.5*1.4-1.2 or 7.5 VAC to get about 9.3 VDC. The 7.4 is the secondary voltage, the 1.4 is an approximation to sqrt(2) and the 1.2 is 2 diode drops from a full wave bridge. Linear regulators usually require at least 3V more DC unless they are of a low-drop out type.
What I would consider is a custom transformer or two custom transformers. One to supply the 9 VAC and one to supply the 9 VDC. They would generally be easy for a manufacturer to make because the windings are wound at the same time. I had one made once. e.g. 8 windings x 9 VAC and one to make the DC once you decided on a regulator (i,e,) ebay.
Other options include buying say a 24 VDC supply and multiple isolated buck converters. Before investing a lot of dollars, you could try some ideas out. Audio and linear supplies go together nicely. Meanwell makes some very reasonable DC supplies. Some are even adjustable somewhat (+-10% usually which won't work for you)
UNLESS you inputs are differential (e.g. XLR connections) then you may end up with way to much hum when you try to consolidate.
==
I went through an exercise where I wanted to "clean-up" my wall warts similar to you, but for my Network stuff in the ceiling. I'm in the US and the wall warts just don't get along with the receptacles.
The first thing I usually do is:
1) Label the wall wart with the device name.
2) Label the cord with the size e.g. 9 VDC 5.5/2.1 C+; The 5.5 is 5.5 mm outer / 2.1 mm inner and the Center positive etc.
3) Label the cord with the device name.
4) The device gets the same markings.
5) Add it to my spreadsheet data-base
I decided to put them on a rack shelf with "octopus cords" and my reliability increased 100 fold.
So, if I grab a random cord, I already know a lot about it and I'm not likely to plug in the wrong one.
The Adapt-a-plug, typically available at Radio Shack **broken link removed** allows polarity reversal and sizing options. I don't like them because it's too easy to reverse the leads and it's designed for low currents.
There are also adapters available that will take a 5.5/2.1 or 5.5/2.5 to other sized plugs, but will not reverse the polarity. I decided that keeping the supplies independent was a good idea.
I created a "universal" supply that I can use in an emergency. I took one of these **broken link removed** and placed it in a translucent box (Hammond enclosure) and put a 5.5/2.1 and a 5.5/2.5 connector for the input, so ALMOST any 12 V 1A wall wart will work for a lot of devices. I also have a 24 VDC supply around, but not a wall wart.
If the polarity needs reversing, it's easy to do on the terminal strip. The output is an Adapt-a-plug pigtail I usually tape or heat-shrink the polarity. So, now I have an EMERGENCY wall wart until I can get a suitable replacement.
I've used the "emergency supply" for a year 24/7 for a 6V device.
The DSL modem uses Power Over Ethernet and I also have all of these devices on a UPS.
FWIW: I would like to make a DC UPS with a particular form factor to run a repeater that would have multiple outputs, but I want a convenient way to either monitor or negotiate the voltage, current, polarity and power limit. i.e. some smarts in the connector.
e.g. EEPROM.
And for a DUMB idea. Take a 24 VDC ($40) supply and use it to make multiple 15 V isolated ($40) supplies and finally down-convert to 9 VDC with an ebay module ($15 ea). I don't like it. It's where the custom multi-winding transformer with a bridge rectifier and capacitors could work. Fuses and power indicators could be added for each supply.
DIN rail construction is easy. I've done it in a rack case. You can buy naked PCB holders for the rail too.
When you build a project, you quickly find out that the case, power supply and real estate (the PCB) takes over the cost. The wall Wart avoids UL approvals and the like. 9V is an ODD voltage. The original wall wart does offer some power protection even if it's the leads melt internally. Surge suppression is likely missing in a typical Wall Wart. Even AC can cause issues. I finally put 24 VAC surge suppression on a furnace.
Also note that 9 VDC does not come from 9 VAC. If you DON'T regulate (not recommended) you would need about 7.5*1.4-1.2 or 7.5 VAC to get about 9.3 VDC. The 7.4 is the secondary voltage, the 1.4 is an approximation to sqrt(2) and the 1.2 is 2 diode drops from a full wave bridge. Linear regulators usually require at least 3V more DC unless they are of a low-drop out type.
What I would consider is a custom transformer or two custom transformers. One to supply the 9 VAC and one to supply the 9 VDC. They would generally be easy for a manufacturer to make because the windings are wound at the same time. I had one made once. e.g. 8 windings x 9 VAC and one to make the DC once you decided on a regulator (i,e,) ebay.
Other options include buying say a 24 VDC supply and multiple isolated buck converters. Before investing a lot of dollars, you could try some ideas out. Audio and linear supplies go together nicely. Meanwell makes some very reasonable DC supplies. Some are even adjustable somewhat (+-10% usually which won't work for you)
UNLESS you inputs are differential (e.g. XLR connections) then you may end up with way to much hum when you try to consolidate.
==
I went through an exercise where I wanted to "clean-up" my wall warts similar to you, but for my Network stuff in the ceiling. I'm in the US and the wall warts just don't get along with the receptacles.
The first thing I usually do is:
1) Label the wall wart with the device name.
2) Label the cord with the size e.g. 9 VDC 5.5/2.1 C+; The 5.5 is 5.5 mm outer / 2.1 mm inner and the Center positive etc.
3) Label the cord with the device name.
4) The device gets the same markings.
5) Add it to my spreadsheet data-base
I decided to put them on a rack shelf with "octopus cords" and my reliability increased 100 fold.
So, if I grab a random cord, I already know a lot about it and I'm not likely to plug in the wrong one.
The Adapt-a-plug, typically available at Radio Shack **broken link removed** allows polarity reversal and sizing options. I don't like them because it's too easy to reverse the leads and it's designed for low currents.
There are also adapters available that will take a 5.5/2.1 or 5.5/2.5 to other sized plugs, but will not reverse the polarity. I decided that keeping the supplies independent was a good idea.
I created a "universal" supply that I can use in an emergency. I took one of these **broken link removed** and placed it in a translucent box (Hammond enclosure) and put a 5.5/2.1 and a 5.5/2.5 connector for the input, so ALMOST any 12 V 1A wall wart will work for a lot of devices. I also have a 24 VDC supply around, but not a wall wart.
If the polarity needs reversing, it's easy to do on the terminal strip. The output is an Adapt-a-plug pigtail I usually tape or heat-shrink the polarity. So, now I have an EMERGENCY wall wart until I can get a suitable replacement.
I've used the "emergency supply" for a year 24/7 for a 6V device.
The DSL modem uses Power Over Ethernet and I also have all of these devices on a UPS.
FWIW: I would like to make a DC UPS with a particular form factor to run a repeater that would have multiple outputs, but I want a convenient way to either monitor or negotiate the voltage, current, polarity and power limit. i.e. some smarts in the connector.
e.g. EEPROM.
And for a DUMB idea. Take a 24 VDC ($40) supply and use it to make multiple 15 V isolated ($40) supplies and finally down-convert to 9 VDC with an ebay module ($15 ea). I don't like it. It's where the custom multi-winding transformer with a bridge rectifier and capacitors could work. Fuses and power indicators could be added for each supply.
DIN rail construction is easy. I've done it in a rack case. You can buy naked PCB holders for the rail too.
When you build a project, you quickly find out that the case, power supply and real estate (the PCB) takes over the cost. The wall Wart avoids UL approvals and the like. 9V is an ODD voltage. The original wall wart does offer some power protection even if it's the leads melt internally. Surge suppression is likely missing in a typical Wall Wart. Even AC can cause issues. I finally put 24 VAC surge suppression on a furnace.