[sdiy] High impedance measurement buffer for audio?

[rburnett at richieburnett.co.uk]

Almost anything you connect in the path is going to degrade the signal 
to some extent compared to going straight into your high end audio 
interface.

How high an impedance would you consider as "not loading" for your 
purposes?

For instance you could use a x10 or x100 scope probe and then amplify 
the signal back up afterwards.  Will definitely add some noise though.  
Some old scopes used to have a Ch.1 output via BNC on the back that you 
could feed to other test and measurement gear.

-Richie,

On 2026-10-26 09:04, Mattias Rickardsson via Synth-diy wrote:
> Hi all,
> 
> I often probe around in both audio circuits, power circuits and other
> circuits. I often want to direct the probed signal both to an audio
> interface and to measurement equipments like oscilloscopes. But when
> the test point is sensitive, I don't want to load it and affect the
> signal.
> 
> Do you have any good recommendations for a device solving these needs:
> 
> 
> - High impedance measurement input for a +/- 20V range
> - Buffered outputs to both audio & lab equipment simultaneously
> - No gain needed
> - Very low noise and low THD needed, it shouldn't degrade the signal
> before going to my high-end audio interface
> - High bandwidth preferred, far higher than audio
> 
> Could be a commercial product or a custom-built solution. Are you
> aware of any obvious solution that I've missed? Or is the low-noise
> low-THD requirement a tricky thing here? :-)
> 
> /mr
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