The DDS-200 is a low distortion AM transmitter that is designed to drive a very clean linear amplifier and produce the nice sound that you can get with a plate modulated transmitters or with some of the better SDR's on the market. I use it regularly on the air and many in the AM fraternity have given me some nice reports on the audio quality. The transmitter is based on the AD9851 (or you can use the AD9850) DDS chip which is now analog modulated on the R set pin12. I also had to combine the (2) separates DDS outputs together using a center tap 1 to 1 output transformer so installing these mods will give you a very clean output of 1 Volt PEP. This 1 Volt output is stepped up through a 3 stage IPA to ramp up the level to a nice 200 watts PEP and then fed through a set of band pass filters. The DDS-200 "DC to Daylight" audio is setup for an AM broadcast processor requiring line level, balanced in via an XLR connector on the rear chassis.
I have this "Little Beast" tagged teamed up with a 4CX3000A amp running in Class AB1 which runs very easily in the harsh environment of the AM linear mode. One other function that the DDS-200 provides is a nice stable source of CW drive for all my plate modulated transmitters so it was a fun project with many benefits for my station. If your interested in putting one of these together, See the (Analog Devices Application Note AN-423) which will give you a new take on those $40.00 ebay signal generators just waiting to become your next HI-FI AM transmitter. I'm in the process of upgrading this design by separating the DDS and modulation function into separate chips and building a final using a pair of LDMOS BLF188XR's for a stand alone transmitter. Also included will be a computer interface which will allow complete frequency, power level and memory capability via my PC.