Cambridge Audio Duo Phono Stage Review (Updated)

[Multicore]

I don’t even listen to vinyl that often, it’s just for fun. So the thought of spending $350 (more than my Cartridge) on a Preamp hurts a little, but I can afford it. What do you guys think?

I think you should get this and buy me a beer with the money saved. It's a great wee unit.

ART DJ Pre II Phono Preamplifier

Buy ART DJ Pre II Phono Preamplifier featuring Phono Preamp for Recording and Playback, Switchable Input Capacitance: 100pF/200pF, Low Cut Filter Switch, Gain Trim and Signal Gain/Clip LED, Low Noise, Precisely Conforms to RIAA Standard, Low Impedance Output, All Aluminum Black Anodized Case...

www.bhphotovideo.com

 

[USER]

I guess I'm a little stuck on what to do.

If I can give you one thing to think about it is that you likely want a preamp that will allow you to have a TOTAL capacitance (phono preamp + cable capacitance, in the more simple view) of less than 200pF for optimal loading of that cartridge. It's quite boosted above 5kHz to begin with. A-T cartridges tend to behave better the lower you go.

See many measurements of the cartridge here:

Introducing the Phono Cartridge Measurement Library

After years of development we are finally launching our phono cartridge measurement library. These measurements were created using the brilliant cartridge response python script written by @scott wurcer and @JP. Information about its origins can be found in the following threads...

audiosciencereview.com

As far as rumble filter effectiveness goes, I can't really speak to what will work best on your system.

 

[Multicore]

I just realized for the first time that the phono preamp is another fundamental limitation on the SQ of vinyl. So, even 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?

There's a thread for that elsewhere with the latest and most carefully standardized measurement protocols. Iirc, in practice if you reach do 50 dB you're SOTA.

 

[formdissolve]

Time for a lesson (and I'm not giving one, I'm asking for one). @amirm wrote "Moving coil input naturally has lower SINAD due to much higher gain"

I know SINAD isn't the end all be all, but many consider MC's as better than MM's. Does this issue of much higher gain essentially eliminate any advantages MC's have over MM's?

When it comes to vinyl playback, it's not as simple as "best SINAD" - there are lot more factors at play and is far more subjective than digital playback. I'll almost always prefer MC over MM (in my system) even with the higher noise floor from the gain stage. It's best to try both out and see for yourself in the end.

 

[andrewskaterrr]

If I can give you one thing to think about it is that you likely want a preamp that will allow you to have a TOTAL capacitance (phono preamp + cable capacitance, in the more simple view) of less than 200pF for optimal loading of that cartridge. It's quite boosted above 5kHz to begin with. A-T cartridges tend to behave better the lower you go.

See many measurements of the cartridge here:

Introducing the Phono Cartridge Measurement Library

After years of development we are finally launching our phono cartridge measurement library. These measurements were created using the brilliant cartridge response python script written by @scott wurcer and @JP. Information about its origins can be found in the following threads...

audiosciencereview.com

As far as rumble filter effectiveness goes, I can't really speak to what will work best on your system.

Well I think I have 35-40ft of Canare L-3CB which is 55 pF/m, that puts me well above 200pF

 

[kencreten]

I appreciate all of Amir's and everyone's work. But I'm ... I don't care about phono sections. I don't play vinyl anymore. I don't know how everyone else is, but the few vinyl records I have from the past, have already been converted to digital. I don't want to go back to the caves.

 

[Kaiju]

good looking amp, thanks Amir.

 

[andrewskaterrr]

I appreciate all of Amir's and everyone's work. But I'm ... I don't care about phono sections. I don't play vinyl anymore. I don't know how everyone else is, but the few vinyl records I have from the past, have already been converted to digital. I don't want to go back to the caves.

So just because YOU don't, no one should?
Why, because people like me are actively looking for a proper Phono Stage for our records. Once I buy one I'll be done. My Muffsy PP-4 DIY is making pops and static noises. I don't even listen that often, but when I do, I want it to be played back properly, not with extra Frequency Response variance, rumble feedback, or loud pops/clicks. It will also improve digital conversions like you talked about.

 

[Thomas_A]

So just because YOU don't, no one should?
Why, because people like me are actively looking for a proper Phono Stage for our records. Once I buy one I'll be done. My Muffsy PP-4 DIY is making pops and static noises. I don't even listen that often, but when I do, I want it to be played back properly, not with extra Frequency Response variance, rumble feedback, or loud pops/clicks. It will also improve digital conversions like you talked about.

How is your Muffsy grounded? I fixed my intermittent issues with the star ground mod.

 

[andrewskaterrr]

How is your Muffsy grounded? I fixed my intermittent issues with the star ground mod.

It's not. I didn't have issues for 2 years, and then it started a few months back. Nothing changed, it just sat unused for like 6 months and it started. From my testing nothing effects it, it just randomly does it. I'm wondering if it's a bad part, but I didn't see any leaky caps last time I opened it. I did bypass the power board though because that was causing interference issues. No clue why he tells you to wire that in only for extra work and noise.

 

[SuicideSquid]

I appreciate all of Amir's and everyone's work. But I'm ... I don't care about phono sections. I don't play vinyl anymore. I don't know how everyone else is, but the few vinyl records I have from the past, have already been converted to digital. I don't want to go back to the caves.

Amir tests lots of gear that I'm never going to use. It's still interesting.

Oh, I was trying to be generous and a little funny. I find most vinyl forums to be hubs of misinformation and usually roll my eyes when I read such anecdotes. Old ears and stubbornness is a bad combo! Most people don't know how to set-up their turntables so it's as uncontrolled an environment as can be. Nonetheless I believe that it is generally accepted that we can distinguish a 0.5 dB difference--not that we can necessarily make a value judgement on it (correct me if I am wrong, anyone)--so a spec of plus minus 0.65 dB I think should disqualify a phono preamp.

I believe the threshold for being consciously aware of a difference in volume is about 2dB. Smaller differences can show up in blind testing (where people can consistently say one source sounds "better" than another when they're actually the same, but for a 1dB difference in volume, for example). But +/- 0.5dB is the point where, for me, I shrug my shoulders, say "good enough", and see how the device measures in other respects. Mediocre there too? Probably a pass. Great noise and distortion measurements? Might be worth my time, especially with vinyl where there are so many other things that colour the sound that a 1dB overall deviation from flat on the phono preamp is certainly going to get lost in the wash.

 

[Thomas_A]

It's not. I didn't have issues for 2 years, and then it started a few months back. Nothing changed, it just sat unused for like 6 months and it started. From my testing nothing effects it, it just randomly does it. I'm wondering if it's a bad part, but I didn't see any leaky caps last time I opened it. I did bypass the power board though because that was causing interference issues. No clue why he tells you to wire that in only for extra work and noise.

The usual suspects are bad solder joints, bad connections, bad chassis grounding.

 

[andrewskaterrr]

The usual suspects are bad solder joints, bad connections, bad chassis grounding.

So I checked my connections today and they’re good. Would bad solder joints start making noise 2 years later? What should I ground to? The PSU is only 2 prong, and the only thing I could ground to besides the TT is the outlet itself.

 

[andrewskaterrr]

The usual suspects are bad solder joints, bad connections, bad chassis grounding.

Also, do you think the PP-4 may be better than these units? The only measurements I’ve seen are the company’s own, which show it being just barely better than the Solo in SINAD and FR.

 

[Thomas_A]

So I checked my connections today and they’re good. Would bad solder joints start making noise 2 years later? What should I ground to? The PSU is only 2 prong, and the only thing I could ground to besides the TT is the outlet itself.

My issues were internal with respect to grounding; chassis contact (need to be filed away to see bare metal in chassis corners) and using star ground (all ground lugs for RCA contacts soldered together). Caused intermittent dropouts in one channel etc; but fixed it.

 

[Thomas_A]

Also, do you think the PP-4 may be better than these units? The only measurements I’ve seen are the company’s own, which show it being just barely better than the Solo in SINAD and FR.

I'll do some measurements of my unit, when time permits.

 

[TheBatsEar]

Actually, I’ve measured mine. It’s about 20 dB. I play music more than 60 dB louder. So, what’s your point?

Count yourself lucky. Mine is above that, more like 50dB. There is the airport in the next city, the train station about 1 km away, the train tracks 200m away, the Autobahn maybe 500m away, the school near me.
I looked up the situation in other cities, it's not rare to have more than 60dB sustained background noise.

My point is this, we all know that records and the technology around it is limited, but it's not as bad as some think it is.

 

[andrewskaterrr]

My issues were internal with respect to grounding; chassis contact (need to be filed away to see bare metal in chassis corners) and using star ground (all ground lugs for RCA contacts soldered together). Caused intermittent dropouts in one channel etc; but fixed it.

Ya I had tried to file away the corner as best as possibly, and I even was messing with the screw in that corner yesterday, but it didn’t seem to be the issue. I’ll take it apart this weekend and check it out again. I don’t have drop out issues though, it’s just weird noise that comes and goes. I’ll try to record a video if it.

 

[andrewskaterrr]

My issues were internal with respect to grounding; chassis contact (need to be filed away to see bare metal in chassis corners) and using star ground (all ground lugs for RCA contacts soldered together). Caused intermittent dropouts in one channel etc; but fixed it.

 

[Thomas_A]

Nasty. Can’t say what it is. Needs to be measured.