Hi. What Zout would be prefered for driving 13 meter balanced cables? According to spec they should be ca 1000 pF but I measured them with a DE-5000 to be around 1500 pF. I know zero ohms would be ideal but what would be a realistic figure?
Something a little higher than zero ohms 🙂 because 1500pF could provoke instability in some opamp output stages.
Even a 1k output impedance will get you past 100kHz (-3db) so I would say just aim for something in the 100 to 500 ohm region. In practice even a few tens of ohm will prevent stability issues.
Even a 1k output impedance will get you past 100kHz (-3db) so I would say just aim for something in the 100 to 500 ohm region. In practice even a few tens of ohm will prevent stability issues.
Thanks. I was thinking of choosing 50 or 100 after opamp. I take it either will work and wont make much of a difference according to your kind answer?
100 ohm is the original design, I was thinking of piggybacking since I am matching from a pack of 100 ohms. But maybe I just stick to 100 then. Its ESP design. Thanks.
They will see 2K8 per hot/cold or 5K6 in total on the other side. I dont matching, I think about the construction in the meentime. I match the recieving input as well, maybe it does something for the CMRR. If not to my self confidence 😉
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So a 100 ohm working into 2k8 causes a 3.75% drop in level. A worst case 1% resistor tolerance means a 99 ohm causes a -3.64 % drop and 101 ohm a -3.71% drop.
So its half of a quarter of nothing 😉 and that assumes the 2k8 is exactly 2k8. There will be a tolerance there as well. So its a non issue.
So its half of a quarter of nothing 😉 and that assumes the 2k8 is exactly 2k8. There will be a tolerance there as well. So its a non issue.