Class D test amp noisy with Apple devices

[Rick Sykora]

Am evaluating budget amplifiers for use in testing and building of active speakers. My latest is one of these:

https://www.parts-express.com/sure-electronics-aa-ab31316-1x400w-class-d-audio-amplifier-board-(t-amp-technology)--320-3344

Am using the recommended Meanwell power supply and a nice $25 case I bought on ebay. My normal setup is a Dayton APA-150 and want to replace it with a more pure amplifier. To test the amp, I use an adapter cable from the headphone jack to the RCA input of the amp. Everything is fairly cool with the APA-150, but the t-amp is have all kinds of nasty distress with my old iphone SE.

It is mainly hiss and hum. I have tried different grounding to no effect, but when I plugged my Amazon echo into the t-amp, all was good again. Any ideas?

 

[Zek]

Your url leads to the login page.

 

[HemiRick]

https://www.parts-express.com/sure-...-amplifier-board-(t-amp-technology)--320-3344

 

[Colonel7]

Am evaluating budget amplifiers for use in testing and building of active speakers. My latest is one of these:

View attachment 77948
https://b2b.parts-express.com/sure-...-amplifier-board-(t-amp-technology)--320-3344

Am using the recommended Meanwell power supply and a nice $25 case I bought on ebay. My normal setup is a Dayton APA-150 and want to replace it with a more pure amplifier. To test the amp, I use an adapter cable from the headphone jack to the RCA input of the amp. Everything is fairly cool with the APA-150, but the t-amp is have all kinds of nasty distress with my old iphone SE.

It is mainly hiss and hum. I have tried different grounding to no effect, but when I plugged my Amazon echo into the t-amp, all was good again. Any ideas?

Not sure of your specific case but I've seen complaints about annoying behaviors on the Sure/Wondom T designs above 100w.

 

[JeffS7444]

How well-shielded is your iPhone cable? Your amp likely uses something like a Tripath TDA1400 chip, and my prior experience with the mid-powered Tripath TA2020 suggested it was an EMI-emitting beast. IIRC one of Tripath's technical notes suggested playing an AM radio in the vicinity of the amp and I seem to recall hearing strong interference at distances of ~ 1M. This is why for anything much larger than little Tripath's TA2024 (which works fine) I much prefer other makes of chip such as Texas Instruments's, which are specifically designed for low EMI.

 

[Rick Sykora]

How well-shielded is your iPhone cable? Your amp likely uses something like a Tripath TDA1400 chip, and my prior experience with the mid-powered Tripath TA2020 suggested it was an EMI-emitting beast. IIRC one of Tripath's technical notes suggested playing an AM radio in the vicinity of the amp and I seem to recall hearing strong interference at distances of ~ 1M. This is why for anything much larger than little Tripath's TA2024 (which works fine) I much prefer other makes of chip such as Texas Instruments's, which are specifically designed for low EMI.

Thanks, but same cable as used with the Amazon device.

Of course, the echo is only wifi and not a cell phone, but wifi-only iPad is problem too. Will try turning off the cellular service to see...

 

[Rick Sykora]

So, a few more observations:

1. Turning off cellular service did not make a difference.
2. Changed out all the cables in favor of better ones and no improvement.
3. Tried my old HP notebook as source (is the target for use with this amp) and it is quiet.

All of the sources are battery powered, so no adapters come into play. Along with more hum and buzz, the Apple devices often cause an ugly power-up transient too. Whatever is going on, appears to more clearly something about the Apple output...

 

[Bob-23]

https://www.youtube.com/results?search_query=rossmann+apple

 

[AnalogSteph]

I suspect it might have more to do with the headphone jack / plug match than everything else, and would try using a suitable (Apple pinout) headset splitter Y cable if available. Alternatively, does the iPhone SE work with a Lightning audio dongle? Neither should be breaking the bank.

 

[Rick Sykora]

I suspect it might have more to do with the headphone jack / plug match than everything else, and would try using a suitable (Apple pinout) headset splitter Y cable if available. Alternatively, does the iPhone SE work with a Lightning audio dongle? Neither should be breaking the bank.

Yes, thought of this too. Do not have any of those adapters around. My iPhone Xr came with earbuds that had a lighting connector already. It has to be something like that. I plugged in a Android phone and no issue either.

 

[Rick Sykora]

Thank you all for your suggestions!

I will eventually try the lightning connector connection, but for now have plenty of free Android phones that work fine.

 

[Nebbermind]

https://www.youtube.com/results?search_query=rossmann+apple

And I thought that would bring us to the solution

 

[Nebbermind]

I suspect the iPhone electronic was not designed to be able to drive the amp. So it may be pushing it to its limitations and caused the distortion