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Cambridge Audio Solo Phono Preamplifier Review

amirm

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#1
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:

Cambridge Audio Solo Audio Review.jpg

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

Cambridge Audio Solo Back Panel Connectors Audio Review.jpg

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:
Cambridge Audio Solo Audio Measurements.png


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:
Best Phono Preamplifier Stages Reviewed.png


Speaking of noise, here is our signal to noise ratio:
Cambridge Audio Solo Signal to Noise Ratio Audio Measurements.png


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

Cambridge Audio Solo Frequency Response Audio Measurements.png


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:

Cambridge Audio Solo THD+N versus Level Audio Measurements.png


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:

Cambridge Audio Solo THD+N versus Frequency Audio Measurements.png


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:

Cambridge Audio Solo Overload Recovery Time Audio Measurements.png


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.

--------
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/
 

DDF

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#2
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.
20 Hz will be swamped by room modes. 300 Hz minor bump is right near a typical speaker floor bounce notch and could be a minor blessing in disguise.
 

JPierre

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#4
Not bad for under $200, although it's a shame that its frequency response isn't flat.
 
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#5
You did not note the lack of CE, UL or othe safety / regulatory certification. You often mention this when it's lacking on AC line powered gear, but did not mention it here. It should be mentioned, it's fairly important.
 

JohnPM

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#6
You did not note the lack of CE, UL or othe safety / regulatory certification. You often mention this when it's lacking on AC line powered gear, but did not mention it here. It should be mentioned, it's fairly important.
The regulatory info labels are on the bottom of the unit. Cambridge Audio have been manufacturing HiFi equipment for 50 years, their products undergo full certification testing and have all the regulatory approvals required for the markets in which they operate.
 

Tks

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#7
That new test looks pretty cool.

By the way, what is the reason for a device to have such FR swings? (I assume its different reasons depending on device type?)
 

anmpr1

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#8
How difficult could it be to place the balance control on the front? Balance control is important for phono if your DAC/preamp does not have it, and many don't. Especially with mono records in order to get the center image correct.

A subsonic filter is helpful. I have an opamp/tube Bellari phono stage that incorporates a subsonic filter. One can easily see the improvement it makes in woofer 'pumping' when switched, as it filters out LF garbage you get from records on a turntable.

In another system I've inserted a dbx 215 equalizer which has a subsonic filter, and also can function as a balance control.

For MM, cartridge loading adjustments are handy, but unless you have a scope and can measure, it's difficult to get anything exact. With records, there is really nothing 'exact' anyhow, so it winds up as just another adjustment you can make if you are inclined.

For me, the big thing is hum. If you can reduce hum to negligible levels you are ahead of the game. I can't get worked up over phono tweaks anymore, although I admit doing the basics (offset and overhang, tracking force and anti-skate), and then leave it at that.
 

wemist01

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#9
Love all the reviews. My listening system and lack of storage space is biased towards digital, so I would not consider any phono stage that does not include a USB out so that LPs can be digitized. And this appears to be a rare feature on the models you test. I've been tempted to send you what I have, but the Pro-Ject USB II box that I used to use (MC setting can clip output from a Denon 103R) has already been replaced once or twice, and I'm not eager to extract my Parasound ZPhono USB from my system. Lack of space makes for awkward wiring arrangements. I'm happy read whatever is posted here, but if you have a chance to test any phono stages with USB out, I'd be very appreciative.
 

LTig

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#11
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.
I also have serious doubts. Those recover delays are extremely long (ages WTR electronics), even for the AP. There must be something wrong.

And I don't think that the test signal is really relevant to the real world. So I ripped a record with ticks to see how they look like. As reference regarding the level of typical music content I also ripped a test record:

  • An organ piece by Bach. I got this for 1€ in the trash bin of a local record store. Full of ticks.
  • Both sides of the DHFI 2 test record (bought new some 35+ years ago)
I hooked my Van den Hul MC-1 Special pickup directly to the inputs of my RME ADI-2 PRO fs. Samplerate was 192 kHz, input sensitivity +4 dBu pluse 6 dB extra gain which amounts to -2dBu = 615 mV rms = 1.74 V pp. Ripping was done with Audacity.
The 1 kHz 0 dB test tone was at -57 dBFs which amounts to -59 dBu = 2.45 mV pp = 0.87 mV rms. The MC1-S is specified to deliver 0.65 mV, so we're close to that.

Here is a screenshot of Audacity showing 3 zoomed parts of the recording:

ticks_and_50u.png


  1. the highest tick in the BACH recording. Its level is at -44 dBFS = 4.9 mV rms = 13.8 mV pp. It length is 44 samples (see screenshot below) which amounts to 230 µs.
  2. the highest tick in the DHFI recording. Its level is at also at -44 dBFS.
  3. a part of the horizontal tracking test signal (300 Hz with 50 µm excursion) which should be the highest signal a pickup has to handle. Its level is at -54 dBFS = -56 dBu = 1.5 mV rms = 4.4 mv pp.
The ticks are some 12 dB higher than the tracking test signal, and some 15 dB higher than the 1 kHz 0 dB test signal.

Here is a zoomed in screenshot of the first tick:

tick1.png

I like to suggest that we define a better test signal for measuring the overload characteristic of phono preamps. Maybe something like a 1 kHz signal at 0 dB/-20dB and such a peak as shown above added in Audacity, with +20/+25/+30 dB higher peak level.

BTW: I amplified the organ recording by 40 dB, did the RIAA equalization with the RIAA EQ and amplified the result again by 7 dB. Then I listened to it with headphones. Boy, the RME is fantastic! I could here the noise before the needle drop but not while the music was playing. This is unbelievable performance!:D
 

LLL

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#12
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.
 

audio_tony

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#13
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 do wonder how long the vinyl resurgence will last, once people realise those "vinyls" deteriorate over time, require careful looking after, a new stylus every couple of hundred hours etc.

My suspicion is that in 5 - 10 years time, apart from a band of dedicated enthusiasts, vinyl record replay will once again be consigned to the annals of history.
 

anmpr1

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#14
I do wonder how long the vinyl resurgence will last, once people realise those "vinyls" deteriorate over time, require careful looking after, a new stylus every couple of hundred hours etc.

My suspicion is that in 5 - 10 years time, apart from a band of dedicated enthusiasts, vinyl record replay will once again be consigned to the annals of history.
Records themselves do not deteriorate over time. I have many I bought in the '60s and '70s that play as new. You just have to take care of them.

Replacement styli are definitely limited. Shure-Stanton-Pickering-Empire-ADC, all the old popular brands, are no longer in the phono cartridge business. AT and Ortofon are alive. Audio-Technica can be had a lower price point. Ortofon typically charges more. Grado still makes lower price point cartridges along with higher priced models. It's not an overly expensive hobby to get into as long as you stay within a budget, and away from the moving coil scene.

Your guess as to how it will be in five or ten is as good as anyone's. I'd give records a better chance at surviving than open reel or compact cassette revivals I've read about (but never witnessed). Even CDs pretty much lost their appeal once folks could download digits. Personally, if I wanted a digital 'record' I wouldn't buy a CD, but look for it on line. It's just a matter of convenience that way. And I can always burn a CD if I need one. I never thought I'd use a PC as a front end, but since I've loaded all my digits to my HD, I don't even have a CD player hooked up. All my CDs are packed up in boxes somewhere. My car has a CD player, but I've never used it. I guess I should try it before the warranty expires. LOL
 

audio_tony

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#15
Records themselves do not deteriorate over time. I have many I bought in the '60s and '70s that play as new. You just have to take care of them.
This I know - I have about a 100 or so left from my collection started in about 1976

I was more considering how many will be played on Crossley type record players, and then left out of covers, stored badly etc.

I also realise that a cheap player doesn't necessarily cause record wear, however I suspect many will be played when the stylus is long, long past it's best.

Replacement styli are definitely limited. Shure-Stanton-Pickering-Empire-ADC, all the old popular brands, are no longer in the phono cartridge business. AT and Ortofon are alive. Audio-Technica can be had a lower price point. Ortofon typically charges more. Grado still makes lower price point cartridges along with higher priced models. It's not an overly expensive hobby to get into as long as you stay within a budget, and away from the moving coil scene.
Yep, been through all this over the years (I have up on LPs back in 1989 or so). Of course apart from the budget brands you mention, there are still many exotic types available, way beyond my reach!

Your guess as to how it will be in five or ten is as good as anyone's. I'd give records a better chance at surviving than open reel or compact cassette revivals I've read about (but never witnessed). Even CDs pretty much lost their appeal once folks could download digits. Personally, if I wanted a digital 'record' I wouldn't buy a CD, but look for it on line. It's just a matter of convenience that way. And I can always burn a CD if I need one. I never thought I'd use a PC as a front end, but since I've loaded all my digits to my HD, I don't even have a CD player hooked up. All my CDs are packed up in boxes somewhere. My car has a CD player, but I've never used it. I guess I should try it before the warranty expires. LOL
Yeah it was just a random 'pie in the sky' number - I'd have to be able to see into the future to even be remotely correct...

As for cassette - I'm not sure about that format either, although it does win out in terms of portability.
But then how long before MD makes a come back lol?

I still like to buy CDs (I have a few CD players still) although I do rip them and my primary listening source is streaming off my own NAS.
 

anmpr1

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#16
As for cassette - I'm not sure about that format either, although it does win out in terms of portability.
Of all the formats I owned, I liked cassettes better, even though they sounded worse than just about anything. I just liked putting them in, setting the level, watching the meters rock out, and hoping the tape didn't run out before the record I was copying. Then pop it out and carry it to my car.

FWIW, my favorite was a mid line Pioneer CT F-9191. Really nice looking aluminum front, large VU meters, wood case, and solid logic control buttons. Back then I'd buy Maxell UDXL II 90s by the case for next to nothing.
 

audio_tony

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#17
Of all the formats I owned, I liked cassettes better, even though they sounded worse than just about anything
I still have my cassettes dating back to the late 70's and most of them still sound really good - particularly as my system improved over the years - the difference is quite noticeable.

I used to work for a car radio installation company, and the installers would often borrow my cassettes to demonstrate a high quality install they had just completed.

Some of my later cassettes recorded in the early 90's from CD still sound fantastic.

No complaints about cassettes from me!
 

Killingbeans

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#18
Some of my later cassettes recorded in the early 90's from CD still sound fantastic.

No complaints about cassettes from me!
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.
 

restorer-john

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#19
I like to suggest that we define a better test signal for measuring the overload characteristic of phono preamps. Maybe something like a 1 kHz signal at 0 dB/-20dB
I've already suggested this to Amir- not sure if he saw the post....

The long standard EIA toneburst test is perfect for the front end. 20 cycles at 0dB and 480 cycles at -20dB.
 

restorer-john

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#20
Some of my later cassettes recorded in the early 90's from CD still sound fantastic.

No complaints about cassettes from me!
Same here. All my recordings were marked with the deck they were recorded on (I have lots) to ensure they were played back on the same machine. I have recordings from the mid 80s that are perfect.
 

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