Measured effect of cable routing/component placement

[GXAlan]

In DIY amplifier kits, there is often talk of cable routing and effects on measured performance. Here I would like to show the difference with real, premium electronics using worst case topologies.

Test Setup
Topping D90 MQA
Belden 8423 0.8m XLR balanced cable
Marantz PM-10 integrated amp
Vishay Dale 1% non inductive resistor
E1DA Cosmos ADC Grade A

The Marantz PM-10 is a fully balanced pre-amplifier and does better than -101 dB for 5W SINAD which is pretty impressive for a full fledged integrated amp with tone controls, a remote control, etc. It uses a bridged pair of HypeX NC500OEM modules.

First, the D90 stacked on top of the PM-10. This is the preamp section of the integrated. The AC cable is over the toroidal transformer.

Take a look at the 60Hz harmonics. The DC is a side effect of the E1DA Cosmos.

Now we rotate the Topping D90 90 degrees.

Here is the Topping D90 moved away from the integrated.

Conclusions
None of this is audible, but imagine seeing the top and bottom measurement for two different amplifiers? How much extra would you pay for the better measuring unit?

I could run more tests to figure out exactly what is interacting with what but the main point is that today’s instruments are capable of measuring so much! If you are an audiophile who likes to tweak and tinker, before buying cable lifters, fancy power conditioners, etc. you should consider buying an ADC to test your own gear in your own home.

Is the Topping D90 being affected by the Marantz or is the Marantz being affected by the Topping? I will have to try additional measurements…

Topping D90 MQA - teardown

Topping D90 MQA - teardown This is the MQA version of the D90 reviewed by Amir here: https://www.audiosciencereview.com/forum/index.php?threads/topping-d90-balanced-usb-dac-review.10519/ back in Dec. 2019. As per the above measurements “the D90 is instrument grade digital to analog convert and...

www.audiosciencereview.com

Here is an internal photo of the PM-10

 

[radix]

A little vertical spacing might help reduce the noise too. And maybe cook the D90 less?

 

[GXAlan]

A little vertical spacing might help reduce the noise too. And maybe cook the D90 less?

I tried vertically spacing it with a shoebox and it didn’t make a big difference.

Oh, this is just a test setup. The PM-10 runs cool since it’s class D. I only just picked up the D90 this morning and wanted to see how it changes measured performance of gear I have measured previously with the UB9000.

 

[GXAlan]

As the update, the Topping does show differences in AC noise. In this case, the Marantz is out of the signal chain.

I'm just physically positioning the D90 in the different positions as above.

 

[Hapo]

...did you try placing a brick on it...???...

 

[GXAlan]

The Topping is being measured, not the PM-10. The PM-10 under the Topping reveals the 60 Hz spikes even if the PM-10 is turned off

Edit: to clarify, the first set is measuring at the amplifier output. D90 to PM-10 to E1DA through resistive load. The second set of graphs is just measuring the D90 directly to the E1DA via XLR cables but putting in the same physical positions (rotated 90 degrees on top of the amp and then far away).

 

[RandomEar]

Well, seeing that XLR cable for the D90 in the first pic close to the mains power cord (rear left of the Marantz, when viewed from the front of the amp) might explain that 60 Hz peak

(Not saying it couldn't come from inside the PM-10, just that this particular arrangement looks suspicious.)