dirkwright
Well-known member
- Joined
- Mar 24, 2012
- Messages
- 83
Hello, I'm an amateur hobbyist and I'm designing a DAC for my own use. I'm using a current output DAC by TI, the PCM1794A.
http://www.twistedpearaudio.com/digital/cod.aspx
http://www.ti.com/lit/ds/symlink/pcm1794a.pdf
I read, and partially understood, an application note from Analog Devices about using transformers with current output DACs:
http://www.analog.com/static/imported-files/application_notes/AN_912.pdf
After studying this article and what others have done, I have concluded that I really need a high level, low impedance transformer with either a center tapped primary or two primaries that can be put in series. I would prefer a voltage step up also. I looked through the Jensen and Cine Mag catalogs and didn't find anything. I really like Jensen transformers, but in this case it looks like the Lundahl LL1674 is a good choice. I know that K&K Audio use it for this purpose, but I'm not sure if they use it with a current output DAC. (I haven't studied their web site well enough to know yet) I'm aware that Sowter probably makes one that would work as well. There seems to be conflicting requirements for this kind of transformer, from what little I know. On the one hand, line level input transformers are usually high impedance, on the other hand, low impedance input transformers are usually low level, as in microphone input transformers. The expected output voltage on the secondary would be about 2Vrms. So, I want to know if I've exhausted the available transformers or if there are others out there that I don't know of that would work well and maybe cost less than the Lundahl. The Lundahl sells for about $140 each. Any help is appreciated.
http://www.twistedpearaudio.com/digital/cod.aspx
http://www.ti.com/lit/ds/symlink/pcm1794a.pdf
I read, and partially understood, an application note from Analog Devices about using transformers with current output DACs:
http://www.analog.com/static/imported-files/application_notes/AN_912.pdf
After studying this article and what others have done, I have concluded that I really need a high level, low impedance transformer with either a center tapped primary or two primaries that can be put in series. I would prefer a voltage step up also. I looked through the Jensen and Cine Mag catalogs and didn't find anything. I really like Jensen transformers, but in this case it looks like the Lundahl LL1674 is a good choice. I know that K&K Audio use it for this purpose, but I'm not sure if they use it with a current output DAC. (I haven't studied their web site well enough to know yet) I'm aware that Sowter probably makes one that would work as well. There seems to be conflicting requirements for this kind of transformer, from what little I know. On the one hand, line level input transformers are usually high impedance, on the other hand, low impedance input transformers are usually low level, as in microphone input transformers. The expected output voltage on the secondary would be about 2Vrms. So, I want to know if I've exhausted the available transformers or if there are others out there that I don't know of that would work well and maybe cost less than the Lundahl. The Lundahl sells for about $140 each. Any help is appreciated.