Wiim Ultra Phono Stage

[StevenSGT98]

I posted this under the Wiim Ultra review, but thought it may be a better fit here.

I did a Google search and have found that both line in and phono in are contained on a sub board. The phono circuit appears to be analog until it reaches, or is close to reaching, the ADC. The opamps are SA5532A, one for each channel. There is an electrolytic on each channel and are Rubycon, but the images I found aren’t of sufficient resolution to determine the values. RIAA appears to be implemented in the analog stage. Opamps on the dac itself are Opa 1611 and 1612.

Perhaps someone who knows design can describe a little more what they see in that phono stage?

Steven

 

[JSmith]

the images I found aren’t of sufficient resolution to determine the values

This video may assist, for now;

JSmith

 

[StevenSGT98]

This video may assist, for now;

JSmith

I did watch this before posting. Using incorrect screwdrivers and lack of static armband made me a bit nervous. I’m sure that’s where the still images I found on another forum actually came from. That being said, the video does a nice job of identifying chips, but I found no reference to the output caps other than perhaps a finger point to them and a brief mention.

If I understand the board layout, RIAA is passive after amplification. I wonder what its noise contribution is. According to the video it appears the line in and the phono stage go into the same 4 channel adc. The SINAD in the phono stage is around 65db. SINAD on the line in is around 86 to 87 db. Since the ADC is limited to this, it sets the maximum SINAD the analog inputs can achieve, with the exception of mains noises. Since RIAA boosts the low end by 20db, it appears the noise attributed to the opamp stage is 1 to 2 db above RIAA, appearing most of that 21db or so is line noise.

It makes me wonder if the noise floor being higher than some of the other stages is more a function of gain as it’s in the low 40’s vs some other stages that are in the mid 30’s.

One thing that Amir didn’t include is a graph of noise by itself that some of the newer reviews include.

Thoughts?

Steven

 

[dtaylo1066]

So is one better sending a MM phono signal to the WiiM's phono preamp input or to its line input via an external phono pre? I am currently sending my TT out to the phono in.

 

[ISchmidt]

The internal preamp should be used only in emergency case

 

[dtaylo1066]

The internal preamp should be used only in emergency case

Thanks. I will try the switch and see how it goes.

 

[StevenSGT98]

The internal preamp should be used only in emergency case

I don’t think anything is to be gained by using a stand alone stage, unless the headroom is just lousy, creating harsh clipping on ticks and pops, which I’m not sensing. What I’ve done is set up the analog in for 24/192 to give it as much breathing room as possible. The Ultra also has adjustable pre gains of +-10 db on all the inputs. This appears to be carried out in the digital domain. I’m uncertain if it has any affect on noise. For instance, the phono stage is generating 41db of gain. Would dropping the gain -5db to 35db reduce the noise floor?

The aux in is best used for analog sources. For most applications in analog it’s just fine. Other digital devices are better taking a digital path in. I would have no qualms about using it for a tape deck, etc, and I’m sure an external phono stage would be ok. It just won’t benefit the same as it would feeding a lower distortion preamp directly. As a stand alone aux in the SINAD is about 86db. Not terrible. But with the inherent noise in vinyl, does it really matter? What’s more important is eq (which is fine) and total harmonic distortion.

For my ears into a modest system (Denon DP-45f table, AT440ml/b cart, Denon 1907 AVR direct, Von Schweikert VR4 jr speakers), the Ultra is quite nice actually. Even the AT isn’t overly bright or harsh, as I’ve heard that cart do in a higher capacitance environment.

Steven

 

[StevenSGT98]

As an add on, streaming the phono to other Wiim’s in the house sounds great ;-)

 

[StevenSGT98]

Another nice little feature of the phono stage I’ve come to appreciate is active muting. It works very well.

 

[Bfeebabes]

The riaa phono sound is fine and if i want low noise i'll use digital rather than vinyl. Still enjoy vinyl through the wiim. Main issue i experience is high microphony on mm/mc. If i tap the wiim case i can hear it through speakers. Very audible on mc. If i lift the wiim off the stand and tap turntable or stand then i don't hear it anywhere near as loud. Any one with experience of this? Is this normal on phono stages generally and especially high gain mc ones? Be good if someone with a WiiM ultra and mc tested theirs to see if its just me/my unit or if it's normal. I assume that a bit of decoupling sorbothane between the wiim and hifi stand will help.