I’ve encountered an issue. Trying to measure a monoblock 2000W@2ohm amplifier. Whenever the voltage goes above 17V or so, the input of the QA403 starts to clip. I verified with the scope that it’s not the amplifier. The input of the QA is set on +42dBV. Usually I use REW, but this time opened the QA software and have the same results.
Just a few hour previously I measures successfully up to 28V. I made my connections the same as I dis countless other times…
Any ideas?
How are you connected to the amplifier (balanced or SE)? Is it a BTL amp or single ended? Is it a BTL class D with DC offset with respect to “ground”?
Also, clearly you are using an external attenuator to measure such powers (2000w@2R). How is that configured?
The connections are single ended. I am not sure if the amp is BLT (facepalm). No external attenuator is being used as I want to measure only up to 40V as the QA can.
Ok I figured it out. The amplifier is BLT and I need to use a probe with differential connections to the QA. All is sorted and now everything is working. Mod, feel free to delete the thread.
If the amp is BTL (PS, just had a BLT for breakfast!), you’ll need to use the differential inputs, otherwise you will likely drive one leg of the amp into a short (BNC outers are all common on the QA403).
Mod, feel free to delete the thread.
Hi @RAW-CAt, I’ll leave in place if you don’t mind. this is a fairly common problem and bit me the first time measuring class single-supply D push pull. I just posted some spice simulations at the link below to help illustrate this. In short, when measuring a push-pull amp, you probably want a 3-resistor attenuator. But when measuring a single-ended amp, you probably want a 2-resistor attenuator.