Cambridge Audio Duo Phono Stage Review (Updated)

[amirm]

This is an updated review of the Cambridge Audio Duo phono preamplifier. It is on kind loan from a member and costs US $349.

The Duo has a solid build and is attractive to boot for its price. Back panel shows independent sets of inputs for moving magnet and coil cartridges:

I like the inclusion of balance control and built-in power supply.

The original version was tested very early on when I had gotten into phono stage testing. My protocols have evolved since then making it hard to compare those measurements to current phono stage reviews.

Cambridge Audio Duo Measurements
It was challenging to reduce ground loops in both channels. After some messing around, I got close to optimal on both channels:

This lands the Duo essentially at the top of the class:

We still have that odd spikes around 19 kHz. Moving coil input naturally has lower SINAD due to much higher gain:

Distortion is vanishingly low when measured without noise:

RIAA equalization is essentially perfect in both modes:

Headroom could be a bit better:

Fortunately the same performance remains up to 10 kHz:

Conclusions
While the cost has gone up $50, the Duo is still reasonably priced for a solid package both physically and electronically. The only miss is with respect to overload due to output maxing out at 10.5 volts. Otherwise we have excellent frequency response and state of the art in distortion in a phono stage.

My excellent recommendation rating for Cambridge Audio Duo remains.

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As always, questions, comments, recommendations, etc. are welcome.

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/

 

[fricc]

Hi Amir, thanks for this new measurement!
I'm a bit confused though, why did we need an update? What did we learn that is new from the previous measurement?
Cheers,
- Fabio

 

[amirm]

I'm a bit confused though, why did we need an update? What did we learn that is new from the previous measurement?

There was a substantial change in methodology. For the first few reviews, I was keeping the output level constant and changing the input level of the preamp to get that level. This causes input levels of MM to be 11 millivolts in the case of this phono stage (from what I recall). This led to complaints that this was too high a level for MM cartridge. So I changed things around where now the input level is fixed (5 mv for MM and 0.5 for MC), and output is variable. The former method gave an advantage to Duo in that it allowed it to have twice as high an output, resulting in better SINAD.

The new method is not without its faults. We are now mostly measuring noise in the dashboard. And gain of the phono stage can bias the results. But it is what we have. The committee decision won.

 

[MCH]

Thanks Amir for redoing this.
Iirc the difference with the Solo version (cheaper and smaller, more attractive for people not using MC I would think) specs wise was a less stringent spec in freq response for the solo. I don't know if the measurements show any remarkable difference in that department that makes the duo worth it.

 

[ZgSTar]

Thank you. Exactly the device I need! Guys, how would you make this wireless to connect it with the preamp that can't sit next to it? Any wireless repeater you'd recommend that will not impact sound quality too much?

 

[TheBatsEar]

Thank you. Exactly the device I need! Guys, how would you make this wireless to connect it with the preamp that can't sit next to it? Any wireless repeater you'd recommend that will not impact sound quality too much?

I think the WiiM pro has the ability to take in analog signal and then beaming it to other DLNA streamers.

Cheers @amirm for the re-measurement, you are a legend

 

[JSmith]

Cambridge Audio Duo

Is this one and the same as the Alva Duo? (seems to be)

Cambridge Audio ALVA Duo Moving Coil & Moving Magnet Phono Preamp

Squeeze every inch of detail from your record collection with our highest quality moving magnet and moving coil phono stage, with integrated headphone amp; the Duo Phono Preamplifier.

www.cambridgeaudio.com

If so;

Either way, thanks for the follow up testing.


JSmith

 

[Rja4000]

The original version was tested very early on when I had gotten into phono stage testing. My protocols have evolved since then making it hard to compare those measurements to current phono stage reviews

Great to re-measure this one !
Thanks !

 

[amirm]

Is this one and the same as the Alva Duo? (seems to be)

I don't know for sure. I looked and this one doesn't say Alva. Maybe they added that to it to justify the extra $50 in cost.

 

[JSmith]

I don't know for sure. I looked and this one doesn't say Alva.

I searched the part number on the main board, and results for both come up, so I think it's the same.

Maybe they added that to it to justify the extra $50 in cost.

Ha, quite likely!


JSmith

 

[TheBatsEar]

Mine doesn't say Alva anywhere, not on the label on the bottom or the box.
It's 3 years old.

 

[JSmith]

Mine doesn't say Alva anywhere, not on the label on the bottom or the box.

I think Amir must be correct, in that they just added the Alva to make it sound more regal. The first pic I posted is the "Alva Duo" and the 2nd is noted just as "Duo", however they appear identical internally and share the same part number on the PCB.


JSmith

 

[Plyske]

So just to be sure: if an MC is not of interest, the Solo is better than the Duo based on measurements?

 

[AudioSceptic]

I don't know for sure. I looked and this one doesn't say Alva. Maybe they added that to it to justify the extra $50 in cost.

I think its full name has always been Alva Duo (and the Solo is the Alva Solo, of course; their MC pickup is Alva MC). <https://www.cambridgeaudio.com/gbr/en/products/hi-fi/phono-stage> It's strange that it's not on the actual product, or is it underneath?

Edit: I've found several photos on ebay, and none say "Alva Duo", just "Duo", underneath. It does say "Alva Duo" on the box.

 

[AudioSceptic]

So just to be sure: if an MC is not of interest, the Solo is better than the Duo based on measurements?

Read Amir's review <https://www.audiosciencereview.com/...ge-audio-solo-phono-preamplifier-review.9666/>. OTOH the Solo is a lot cheaper, as it should be, with no MC, no HP amp, and no volume control.

 

[fricc]

There was a substantial change in methodology. For the first few reviews, I was keeping the output level constant and changing the input level of the preamp to get that level. This causes input levels of MM to be 11 millivolts in the case of this phono stage (from what I recall). This led to complaints that this was too high a level for MM cartridge. So I changed things around where now the input level is fixed (5 mv for MM and 0.5 for MC), and output is variable. The former method gave an advantage to Duo in that it allowed it to have twice as high an output, resulting in better SINAD.

The new method is not without its faults. We are now mostly measuring noise in the dashboard. And gain of the phono stage can bias the results. But it is what we have. The committee decision won.

Thanks for the clarification. Indeed measuring the device in its normal operating range is a good idea

 

[oceansize]

Alva is the name we give our products designed to unlock that characteristic warm vinyl sound. It includes a pair of new Alva turntables, our custom-designed moving coil cartridge, and two award-winning phono pre-amplifiers.

Cambridge Audio site

 

[Multicore]

I think my downstream unit (MiniDSP Flex) can get by without inputs greater than 10.5 V. I actually wonder what home entertainment gear with phono inputs doesn't clip with spikes > 10.5 V.

 

[MediumRare]

I just realized for the first time that the phono preamp is another fundamental limitation on the SQ of vinyl. So, even when everything else in your chain is perfectly transparent (the disc, the cartridge, etc.) the best SINAD you’re ever going to get with MC is ~-63 dB. That’s even worse than most speakers above ~300 hz. Am I missing something? What do measurements of vinyl test recordings deliver in best-case systems?

 

[USER]

For anyone interested know that I bought this one years ago refurbished from Cambridge Audio on eBay. The receipt says "c grade" but as you can see, no cosmetic issues. YMMV, of course. Great to see the product performing as it should!