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Algar_emi 22nd September 2007 01:54 AM

My AYA-DAC ver 2.0c Accessories PCB's
Hi. I'm building this intringuing TDA-1541 DAC with a friend, the AYA-DAC ver 2.0c, see:

However this particular design need as a supply a custom transformer with more than 8 separates AC secondaries.

I design a custom PCB that accept 5 separates transformers and can supply all the AC suppllies needed by the AYA-DAC. The transformers are not expensive, about 6U$ each for the three 8Vac transfos and 8U$ each for the two 18Vac transfos. They are easily available from Digikey. This alternative will give the same supply insulation as a custom transformer but at a much cheaper price. The choosen transformers are split bobbins type that has low coil couplings providing an excellent insulation without using a static shield as needed when using a toroidal transfo. This is the type of transformer recommend for preamp use by John Curl himself as discussed on the Blowtorch thread

The PCB will have these features:
-Pads available for AC input and fuse socket
-Provision for an input C-L-C EMI AC input filter
-Dual Primaries transfo and easy solder jumper Main Ac voltage selection (120-240, 110-220V)
-Provision for an Main Power-On Switch
-Built in Power-On Led circuit and header 2-pins socket
-AC Output on the same screw terminal as used on the AYA Dac.

I'm planning to build and test a prototype in the next few weeks.
Pass the word on Yahoo.

I'm building my own PCB. I may build some more if some other users are interested.

Algar_emi 22nd September 2007 02:03 AM

2 Attachment(s)
Take note that I had two pre-requisites when designing the PCB. It has to fit into a nice case that I already had in stock. This explain some of the strange mounting hole locations. It also had to fit into the maximum PCB sheet material that I'm using. Here the first version of this PCB.

Algar_emi 22nd September 2007 02:12 AM

2 Attachment(s)
I'm also designing an active BNC digital input PCB, based on the same AD8611 High-Speed 4ns comparator used into the Headphone DAC project. This version version is using a local 3.3V regulator supplies from the DAC 5V supply. This is probably not the final version of this PCB. I want to add a relay to switch between to inputs, this active one and the original AYA DAC transfo coupled. By using a front mounted switch it will be possible to switch between these two inputs.

There is also provision to use this bare PCB only as a mounting PCB for the true 75 ohms BNC, 31-10-75 Amphenol connector that I will use.

Since both inputs are using a different approach, active and transfo coupled, it will be possible to choose the one with the best sound for your application.

Here my first pcb version. The bottom layer is the gnd plane.

Algar_emi 22nd September 2007 02:16 AM

2 Attachment(s)
This is the active input schematic from the Headphone-DAC schematic.

Algar_emi 23rd September 2007 04:53 AM

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Here the input PCB ver 1.2 that support 2 inputs, one active before the transfo, the other directly to the transfo as the original design. A small SMD Omron relay selects what input. The direct connection is selected by default. Just add a switch and you can easily select the input.

Algar_emi 4th October 2007 08:25 PM

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Here the input and transfo PCB schematics.

Algar_emi 5th October 2007 06:17 PM

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The transfo PCB is fully functionnal, here a view. As needed by the dac, there is 5 X 8Vac and 3 X 18Vac separate outputs.

Algar_emi 5th October 2007 06:19 PM

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And the digital input PCB. The active section output resistor R30 will be tuned to get a 75R output impedance going out of the comparator.

Kip 5th October 2007 09:25 PM

I am interested in your transformer PCB. I am building the same dac and purchased two large transformers, but they are more difficult to fit into a chassis. Let me know if you are interested in selling a PCB.

Algar_emi 6th October 2007 12:40 AM

Yes, no problem. I can make a small run of these PCB. They are excellent quality FR4 PCB. You can solder plate the traces yourself or I can do it for you for a small fee. It will be all drilled ready to use. I'll do a small change to it to use a more common fuse holder. I can do it in the next weeks. Send me an email.

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