WiiM Amp line-in sensitivity

[musig]

Dear all,
sorry if this has been answered somewhere else, I couldn't find it. Which is the input sensitivity af the line-in circuitry?

Thank you

 

[Petevid]

Too low to work satisfactorily with common turntable phono preamps from the likes of Pro-ject

 

[cooky560]

It's a standard RCA input, probably somewhere from 800mV to 2V. You can get a phono stage to connect a turntable to it

 

[Petevid]

It's a standard RCA input, probably somewhere from 800mV to 2V. You can get a phono stage to connect a turntable to it

I’m using one. It’s a Pro-ject phono box e, probably one of the most common pre amps out there.

It has an output voltage of 500mV which is pretty common for turntable pre-amps.

 

[cooky560]

Phono Box – Pro-Ject Audio Systems

Phono Box: Best buy classic for pure vinyl listening pleasure! Today, many amplifiers do not have a specific phono cartridge input. Phono Box is an ideal phono

www.project-audio.com

I had no issues connecting this box to my wiim amp, it seems like the same box only for MC carts, so it should be ok.

 

[musig]

The reason why I asked this question is because my setup is able to produce lower max volume sound with the WiiM Amp than with the previous amplifier I used, a Mission Cyrus 2. The line inputs of the Cyrus have a sensitivity of 0.650V and I suspect that the WiiM Amp has a much higher one.

 

[Petevid]

Yes musig, same here.

It’s a shame we can’t get high volume from a phono pre amp that has a standard 500mV output through the line input. Does this mean the sensitivity of the line input is too low though?

 

[musig]

Yes musig, same here.

It’s a shame we can’t get high volume from a phono pre amp that has a standard 500mV output through the line input. Does this mean the sensitivity of the line input is too low though?

Well, the input sensitivity is a design choice, I guess that in this case the WiiM Amp has a higher one and this leads to a lower max volume. I think it would be nice to have the official information, it is an important value that determines the way to match this amp with sources.

 

[Petevid]

Yes, I agree.

 

[harkpabst]

... it seems like the same box only for MC carts, so it should be ok.

If it is the "same box only for MC" then ... well ... it's not the same box, right?

In fact, the Phono box and Phono box E are different animals. The MM sections are specified to have the same gain (40 dB), though. It's 60 dB for the MC input (only found on the non-E Phono box). Depending in what exact MC cartridge you are using you might (or might not) get a higher output voltage. Different MC cartridges vary quite a bit in output voltage. Differences of 6 dB or more are not uncommon.

 

[Woody]

I'm seeing the same thing using output from TV via Optical and HDMI. Have to crank the amp up significantly more than I do for streaming music.

 

[harkpabst]

According to @WiiM Support the Amp uses the Texas Instruments PC1861 ADC. According to its spec sheet this ADC needs 2.1 V input voltage for digital full scale single-ended (or 4,2 V for a balanced input). The RCA input is single-ended by nature and I wouldn't expect WiiM to have added an additional gain stage before the ADC (maybe a buffer or just some protection circuitry).

If these assumptions are correct, then the input voltage would in fact be 2.1 V. Anything lower than that could not drive the WiiM Amp to full power.

I would further assume that some digital gain could be added and be made adjustable through the WiiM Home App. This would reduce the SNR available from the ADC, but it might still be worth it for people trying to match a typical phono stage with the amp, given that LP records are an inherently much more noisy source anyway.

 

[musig]

According to @WiiM Support the Amp uses the Texas Instruments PC1861 ADC. According to its spec sheet this ADC needs 2.1 V input voltage for digital full scale single-ended (or 4,2 V for a balanced input). The RCA input is single-ended by nature and I wouldn't expect WiiM to have added an additional gain stage before the ADC (maybe a buffer or just some protection circuitry).

If these assumptions are correct, then the input voltage would in fact be 2.1 V. Anything lower than that could not drive the WiiM Amp to full power.

I would further assume that some digital gain could be added and be made adjustable through the WiiM Home App. This would reduce the SNR available from the ADC, but it might still be worth it for people trying to match a typical phono stage with the amp, given that LP records are an inherently much more noisy source anyway.

First of all thank you for this investigation, it gives us precious information that can explain effects that we notice while using the WiiM Amp. Besides, I think that this is a specification that WiiM should provide because it makes a lot of difference knowing it in advance. In a use case like @Petevid 's one I would have made a different choice because phono preamps often have much lower output voltage.

 

[DavidGriffiths]

Slightly offtopic but there appears to be a problem with the sensitivity. If I have the auto-detect thing turned on for line-in then sometimes even with the turntable turned off it will switch away from HDMI to line-in. So I only turn that on when I use the turntable.