Following the recent discussion of using the Extron ADA 6 as a distribution amplifier for 1/5/10 MHz reference signals, I dug out the schematic of the amplifiers and typed up my notes re: modifications (see attached). Note that the ones I have are "plain" ADA 6's, not "MX" or "MX-HV." I do not know if the MX or MX-HV units use this circuit or, if they do, if the component numbers are the same. However, the gain-switching circuitry is present on the "plain" ADA 6 PC cards (but the switch itself is not), which leads me to believe that at least the MX version was built with this same card. There may be other Extron video DAs that use this circuit -- in particular, models that have a PC card parallel to the rear panel and mounted to it by the BNC connectors may do so. There is another, discrete design that Extron apparently produced at the same time, one example of which is the ADA 3 180. This design cannot drive 50 ohm loads to +13dBm (1 Vrms) without severe distortion (negative peak clipping), so you need to attenuate the typical 1 Vrms input signal 6 dB to stay out of clipping. Unfortunately, there is no easy way to modify this design to drive +13dBm into 50 ohms (and, IMO, there is a lot not to like about it for any use, including RGB video). I have a schematic of that circuit, too, if anyone needs it. Best regards, Charles

What I have been referring to as the "plain ADA 6" is properly known as the ADA 6 Component: <www.extron.com/download/files/userman/ADA6ComponentB.pdf> Judging from the dates on some of Extron's documents, it appears to be a newer model than the ADA 6 300 series -- which is consistent with Bruce's comment that his ADA 6 300MX had through-hole resistors. Accordingly, it is possible that the ADA 6 300 models do not share the circuit I attached to my last e-mail. As always, use due diligence! Best regards, Charles >Following the recent discussion of using the Extron ADA 6 as a >distribution amplifier for 1/5/10 MHz reference signals, I dug out >the schematic of the amplifiers and typed up my notes re: >modifications (see attached). > >Note that the ones I have are "plain" ADA 6's, not "MX" or >"MX-HV." I do not know if the MX or MX-HV units use this circuit >or, if they do, if the component numbers are the same. However, the >gain-switching circuitry is present on the "plain" ADA 6 PC cards >(but the switch itself is not), which leads me to believe that at >least the MX version was built with this same card. > >There may be other Extron video DAs that use this circuit -- in >particular, models that have a PC card parallel to the rear panel >and mounted to it by the BNC connectors may do so. > >There is another, discrete design that Extron apparently produced at >the same time, one example of which is the ADA 3 180. This design >cannot drive 50 ohm loads to +13dBm (1 Vrms) without severe >distortion (negative peak clipping), so you need to attenuate the >typical 1 Vrms input signal 6 dB to stay out of >clipping. Unfortunately, there is no easy way to modify this design >to drive +13dBm into 50 ohms (and, IMO, there is a lot not to like >about it for any use, including RGB video). I have a schematic of >that circuit, too, if anyone needs it. > >Best regards, > >Charles