[time-nuts] Extron ADA 6 as 1/5/10 MHz DA

Charles P. Steinmetz charles_steinmetz at lavabit.com
Wed May 22 13:59:37 EDT 2013

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,


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