Cambridge Audio Solo Phono Preamplifier Review

[restorer-john]

The lowest signal my analyzer can generate in 10 Hz. So I set it to that. Then I sample the output at multiples of it (I think 64 times a second) to fully capture that waveform. Then, I program the generator to operate at two levels, one at 0.1 volt and the other 40 dB lower than it. The peaks are very short as to simulate a pop/glitch. Here is what I get:

You aren't proving anything with this 'test' Amir.

Again, why are you using 10Hz? The stage will be deliberately designed to roll off well above that either in the front end (capacitors) or the NFB/Servo or both.

Clicks and pops are best represented by 1-5KHz tonebursts, not 10Hz infrasonics. Why re-invent the wheel on this?

 

[anmpr1]

Recordings on Type IV tapes sounds pretty damn good. I sold my tape deck 20 (?) years ago and didn't look back, but I do remember it fondly.

My Pioneer couldn't bias/EQ metal. I think it went up to Type 3. Reviews showed it to be relatively flat out to 12-13KHz, and then dropping off. Most review measurements were done at both -20dB and 0dB. HF/distortion was always worse approaching 0dB level.

I remember one of the first popular priced decks with really good performance was the Teac 450. Of course there were the more costly high enders from Nakamichi, ReVox, and Tandberg, etc. There is a review of a Nakamichi Dragon here at ASR, but I don't know that it was in tip top like new shape. You can probably still get a high end Nak repaired somewhere. They were probably the best and most popular of the lot. I can't imagine trying to get something from Tandberg serviced, today. Maybe it can be done.

I had a mid-line Denon cassette deck with fluorescent meters that made decent recordings with metal tapes. But after a few years the logic control went south, and the controls stopped working. It just wasn't made to last. By then, it was all digits, so I never replaced it. I don't even know if high bias and/or metal tapes are sold, anymore. I see people selling NOS tapes. Not sure how they last over time. I know old open reel tape is variable.

 

[Tom C]

I don’t see an analysis of accuracy of RIAA correction, which is the primary purpose of a phono stage. Did I miss it?

 

[LTig]

I don’t see an analysis of accuracy of RIAA correction, which is the primary purpose of a phono stage. Did I miss it?

Yes, it's there (frequency response).

 

[amirm]

I don’t see an analysis of accuracy of RIAA correction, which is the primary purpose of a phono stage. Did I miss it?

Yes. The frequency response is that. The generator uses inverse RIAA equalization. So a correct Eq in the device would show flat line.

 

[Tom C]

I see. OK, thank you.

 

[AudioSceptic]

My Pioneer couldn't bias/EQ metal. I think it went up to Type 3. Reviews showed it to be relatively flat out to 12-13KHz, and then dropping off. Most review measurements were done at both -20dB and 0dB. HF/distortion was always worse approaching 0dB level.

I remember one of the first popular priced decks with really good performance was the Teac 450. Of course there were the more costly high enders from Nakamichi, ReVox, and Tandberg, etc. There is a review of a Nakamichi Dragon here at ASR, but I don't know that it was in tip top like new shape. You can probably still get a high end Nak repaired somewhere. They were probably the best and most popular of the lot. I can't imagine trying to get something from Tandberg serviced, today. Maybe it can be done.

I had a mid-line Denon cassette deck with fluorescent meters that made decent recordings with metal tapes. But after a few years the logic control went south, and the controls stopped working. It just wasn't made to last. By then, it was all digits, so I never replaced it. I don't even know if high bias and/or metal tapes are sold, anymore. I see people selling NOS tapes. Not sure how they last over time. I know old open reel tape is variable.

Amazon lists some Sony, Maxell, and TDK cassettes.

 

[watchnerd]

And people are flocking back to analog.... In my other life as a photographer, it also doesn't make sense. But I guess nostalgia is an emotional response and that's much stronger than facts and data.

I got my first TT in 2013 and have accumulated all my LPs since then.

In my case, I don't have nostalgia for LP, as it was already on its way out by the time I was a kid, with cassettes taking over, and eventually, CDs.

So my enjoyment of LP isn't based on remembering my past, but instead based on the fun I have playing with all the variables involved in LP playback and learning new stuff.

 

[watchnerd]

This is a review and detailed measurements of the Cambridge Audio Solo Phono Preamplifier. It is on kind loan from a member. The solo costs US $179.99 including free shipping from Amazon.

The solo only supports Moving Magnet (MM) cartridges so there are no controls in front other than a (soft) power switch:

View attachment 37586​

The solo feels and looks good, setting it above typical budget audio products. Love the attention to detail on the back:

View attachment 37587​

Notice the upside down labels so that when you look at it from the top as you often do, you can still read them.

Also great to see is a balance control.

Inclusions of an internal power supply completes a nice picture.

I had previously reviewed the Cambridge Audio Duo. The hope is that the Solo has the same performance as the moving magnet subset of that unit. Let's get into the measurements and see if that is the case.

Phono Stage Measurements
For our dashboard, I now use a 5 millivolt input. The duo was tested at 11+ millivolts so they are not exactly comparable:
View attachment 37589

Performance is essentially limited by mains noise which is common in phono stages. There are infinite ways to change grounding here and above is my best shot after a few minutes. Key is that there is no distortion products. If you can manage ground loops/hum, the amp is fully transparent to your cartridge. Here is how the Solo ranks:
View attachment 37590

Speaking of noise, here is our signal to noise ratio:
View attachment 37591

I was expecting a flat response like the Duo produced. Alas, I did not get that:

View attachment 37592

I looked up the spec as noted in the graph and indeed, it is twice as bad as the Duo spec. Threshold of hearing for broad frequency response variations in low frequencies is just 0.5 dB so these swings could be audible.

Here is what our noise and distortion looks like relative to input level:

View attachment 37593

The Schiit Mani is $50 cheaper so good to see the Solo beats it by good margin including not clipping even at high input level of 100 millivolts.

We can run the same test relative to frequency:

View attachment 37594

These measurements may be hum dominated though so hard to tell if what is shown is distortion or just noise.

Finally here is a new test I am developing. Many times by accident I overdrive these phono preamps and I see them take a while to produces a valid signal even after I have reduced the input level. The goal here is to simulate the same thing happening with a pop/tick from the cartridge against a much lower baseline signal. And do so within the constraints of my analyzer.

The lowest signal my analyzer can generate in 10 Hz. So I set it to that. Then I sample the output at multiples of it (I think 64 times a second) to fully capture that waveform. Then, I program the generator to operate at two levels, one at 0.1 volt and the other 40 dB lower than it. The peaks are very short as to simulate a pop/glitch. Here is what I get:

View attachment 37595

At the bottom in dashed blue is the Audio Precision analyzer testing itself. We see that it takes it about 0.4 seconds to drop from that peak down to baseline level.

The one in red is the same signal now routed through the Cambridge Solo. The measured time now (shown through two red cursor lines) is 1.6 seconds.

My confidence is not high in this test yet but it is something I am going to run in the future until I figure out its limitations/value.

Conclusions
The Cambridge Audio Solo is an attractive, well-designed phono stage. Alas, it is not a defeatured Duo. Performance is a step down in the important frequency response. So my recommendation is to stretch your dollars and buy the Duo. It supports both MC and MM cartridges and has a headphone amplifier to boot.

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

Google is marking the word "defeatured" above as spelled wrong. Quick search on Google no less, shows it to be correctly spelled. Seems to me, they must not have enough engineers to write a proper spell checker for Chrome browser. I like to act as their agent to collect money for them to hire the right people to remedy this. So please donate generously so that we can all benefit from articles with less typos using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/

Methodology question:

I didn't notice a test of the RIAA EQ accuracy. Maybe I missed it.

Are we assuming that RIAA EQ accuracy is a non-issue these days?

Nothing wrong with that assumption, per se. Just clarifying the POV.

 

[LTig]

Methodology question:

I didn't notice a test of the RIAA EQ accuracy. Maybe I missed it.

Are we assuming that RIAA EQ accuracy is a non-issue these days?

Nothing wrong with that assumption, per se. Just clarifying the POV.

See #25. Lots of blind people today.

 

[watchnerd]

See #25. Lots of blind people today.

Thank you.

Adding this note from Amir to the review: "The generator uses inverse RIAA equalization" would help.

And I did search on RIAA in the first page....so I wasn't 100% lazy. Maybe 50% lazy....

 

[watchnerd]

I do wonder how long the vinyl resurgence will last

I find it interesting how often this question comes up in vinyl related threads.

I collect mechanical watches. I don't often see people ask how long the "mechanical resurgence" will last. Maybe in the first 10 years after the quartz watch revolution happened, they did. FFWD to 2019, and for the time being, new mechanical watches are still being made, at multiple price points.

My wife's friends from Japan are visiting this weekend. They found my turntable and LP collection interesting.

 

[AudioSceptic]

The Cambridge CP2 (MM + MC) has been reduced from £150 to £99. Does anyone know if it's closer to the Duo (its successor) than to the Solo? I can't find measurements anywhere.

 

[audio_tony]

I collect mechanical watches. I don't often see people ask how long the "mechanical resurgence" will last.

It's a totally different field though isn't it? Additionally, watches are things of beauty, a vinyl record is.... just a record.

I know of so many people who have jumped on the vinyl bandwagon, simply as a fashion statement which has soon faded.

Also, a watch is a watch - there is no alternative (excluding clocks etc.) but there are several different ways to listen to music.

You wouldn't try and wear a clock on your arm though would you?

I stand by my statement.

 

[watchnerd]

It's a totally different field though isn't it? Additionally, watches are things of beauty, a vinyl record is.... just a record.

I know of so many people who have jumped on the vinyl bandwagon, simply as a fashion statement which has soon faded.

Also, a watch is a watch - there is no alternative (excluding clocks etc.) but there are several different ways to listen to music.

You wouldn't try and wear a clock on your arm though would you?

I stand by my statement.

I happen to think both LPs (with their cover art and liner notes, photographs) are things of beauty. And I think my TT is gosh darn pretty, too. Watching it spin around brings me joy.

As for watches, yes, there are alternatives in the forms of cell phones.

Anyway, time will tell.....

(pun intended)

Back to the regular thread.

 

[audio_tony]

Anyway, time will tell.....

 

[AudioSceptic]

I got my first TT in 2013 and have accumulated all my LPs since then.

In my case, I don't have nostalgia for LP, as it was already on its way out by the time I was a kid, with cassettes taking over, and eventually, CDs.

So my enjoyment of LP isn't based on remembering my past, but instead based on the fun I have playing with all the variables involved in LP playback and learning new stuff.

Had any fun checking your tracking alignment (Löfgren, Baerwald, etc.)?

 

[amirm]

Again, why are you using 10Hz? The stage will be deliberately designed to roll off well above that either in the front end (capacitors) or the NFB/Servo or both.

It doesn't matter what the frequency is in this case. I am trying to simulate this from graph posted earlier:

I can't produce an impulse like that by itself. What I can do is create it with a burst tone. The 10 Hz frequency was picked because I am using the continuous recorder in AP software. It is like the EEG plots. That system samples up to 256 times a second. Using 10 Hz I can sample it fast enough so that it won't alias. You can see the sine wave clearly in the graph showing this happened.

The step function is clearly amplified by the phono stage so there is no issue of it ignoring it.

The measurement time is over 1 second so whatever I do has to capture very long periods and hence the use of the recorder.

The fact that the original sine wave is filtered out mostly is a good thing, allowing us to see the time domain response of the step function better.

The recovery time has definitely been extended by the phono stage relative to AP's own input stage.

All this said, yes, this is work in progress. I don't know if the data is useful, nor whether AP's response in capturing that amplified glitch is correct.

 

[amirm]

Here is a zoomed in screenshot of the first tick:

Thanks for the graphs and measurements. I am puzzled how this zoomed version matches the sample I just post above. The case I am trying to simulate is the worst case where we go from near silence to the spike that LP produces. I have heard them loud enough to make me jump out of my seat!

 

[LTig]

[..]
I can't produce an impulse like that by itself. What I can do is create it with a burst tone. The 10 Hz frequency was picked because I am using the continuous recorder in AP software. It is like the EEG plots. That system samples up to 256 times a second. Using 10 Hz I can sample it fast enough so that it won't alias. You can see the sine wave clearly in the graph showing this happened.

Agreed - still I think the AP may be the wrong tool here[1]. A 2 channel DSO will be better suited:

• play a stereo EIA toneburst signal with foobar2000 to any USB soundcard
• connect the leftt channel of the soundcard output to channel 1 input of the DSO
• connect the right channel of the soundcard output to the input of the DUT
• connect the output of the DUT to channel 2 input of the DSO
• trigger the DSO with the first high level cycle of channel 1
• check the behaviour of the DUT on channel 2 of the DSO
• create a screenshot of the DSO for publishing

If you have no DSO use the Scope in REW, it should work (never used it, but there are trigger settings).

You could use Audacity to create any test signal you want. I could send you the EIA toneburst signal as WAV or FLAC (today I updated my gensig tool to create it). Just tell me number of channels, samplerate and duration.

[1] Those recovery times are very suspicious to me. If I find the time I test my DIY phono preamp with the EIA tone burst.