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Cambridge Audio CXA81 Review (Sample 2)
- Thread starter amirm
- Start date
Honestly I don't think CA is a such kind of brand. Making such statistics is out of scope of ASR I think.
We should have data to make these claims, but we do not.
We are all focusing on USB connected problem that has little impact on SINAD (~8db).
But SINAD of the power amplifier section is 85db @5W (16.5bits of dynamic range at full power) ,
hence at its best it is a mid-chart amplifier from this point of view.
I still think that is "not competitive for its price tag".
It would be interesting to know (for me of course) the SINAD when volume knob is at 10 since this is the way I use it.
Also SINAD @1W would be interesting.
But SINAD of the power amplifier section is 85db @5W (16.5bits of dynamic range at full power) ,
hence at its best it is a mid-chart amplifier from this point of view.
I still think that is "not competitive for its price tag".
It would be interesting to know (for me of course) the SINAD when volume knob is at 10 since this is the way I use it.
Also SINAD @1W would be interesting.
audio_tony
Major Contributor
All the Cambridge Audio gear I've encountered has the chassis grounded to mains earth.
So if the USB cable is connected to a PC (or the AP) which I assume to be grounded to mains earth - this is creating a ground loop surely?
The attached image shows the USB input layout for the 851D DAC which I suspect is quite similar to the CXA81
With the earth lift activated, there is a 100 ohm path to chassis ground via R91
Measuring from mains ground to USB ground I measure ~26 ohms, as expected this rises to 126 ohms with the earth switch open.
So if the USB cable is connected to a PC (or the AP) which I assume to be grounded to mains earth - this is creating a ground loop surely?
The attached image shows the USB input layout for the 851D DAC which I suspect is quite similar to the CXA81
With the earth lift activated, there is a 100 ohm path to chassis ground via R91
Measuring from mains ground to USB ground I measure ~26 ohms, as expected this rises to 126 ohms with the earth switch open.
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Ajax
Senior Member
I don't see a future for this type of product within knowledgeable audio groups such as ASR, especially when compared with a Topping (or SMSL) DAC combined with say a Hypex based power amp. Such a combination will provide SOTA performance with twice the power at half the cost.
OP
- Thread Starter
- #126
Of course you do. You would have a computer just like me. And you would have a powered downstream external amplifier. AP is actually better than your situation as its unbalanced inputs are floating.
OP
- Thread Starter
- #127
They offered to send a random sample from one of their retailers. I told them that I trusted them to not hand pick one and send one from factory which they did. So while it is possible there are variations in each unit, I don't consider them trying to game this evaluation.
I’d need to see a sketch of how your testing equipment is wired together, as I’m just assuming.
I imagine you have something like: computer -> CXA81 -> AP -> computer.
My setup is just: computer -> CXA81
And I heard no difference in hiss with the volume at 100% with or without a USB cable connected. I’ll try to think of another test to try.
I imagine you have something like: computer -> CXA81 -> AP -> computer.
My setup is just: computer -> CXA81
And I heard no difference in hiss with the volume at 100% with or without a USB cable connected. I’ll try to think of another test to try.
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There is absolutely a future for this type of product in my opinion. Best audio component would be a 2 channel integrated that would measure SOTA. Not everyone wants a bunch of little boxes that measure perfect on the bench. I see why people buy a Cambridge.
I would suggest that every class I audio product with USB input should have the USB link galvanically isolated. There is a zillion of possible component combinations where the non-isolated USB makes an issue. I know several owners of nice Topping DACs like D90 who have audible issues only for the reason of non-isolated USB in the class I DAC. I do not understand why the manufacturers are so careless. It is the manufacturer’s design flaw, no excuses appreciated.
Ajax
Senior Member
I understand a lot of people prefer an attractive simple system, my own preference would be for a DAC with an integrated streamer.
It's personal preference to some degree, and I was just putting forward a better performing option for those interested in seeing alternatives. The reality is that you are paying for something readily available at half the price, and with more power. The hypex amps with their extra power provide a lot of flexibility with speaker selection, which is more important to me. They run cool and can be placed out of sight, so you will still only see the one box in any case, which can also be controlled by a remote.
IMO the only upside with the Cambridge is for those wishing to connect a turntable and require an analogue input. In that case I would get a secondhand Benchmark DAC 2, which when combined with the hypex amp would be the same money as the Cambridge.
My 2c as they say.
SoundSoundS
Member
- Joined
- Apr 6, 2021
- Messages
- 13
- Likes
- 4
I must say i never understood this hypex hype. I've never heard a nice (not good), nice hyper amp by it's own. They all sound like crap even if they porvide twice as much power for the same price. Unless u put a nice (maybe tube) pre/power amp , which again will add cost. Hence why you would see most expensive Hyper implementations doing so. So if i had to choose between twice more powerfull SOTA lifeless crap , or less powerfull nice sounding OK amp, guess what ?
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OP
- Thread Starter
- #133
Not a good idea. You wind up giving clean bill of health to a lot of products that have issues. People go and buy them and complain your tests were no good because they don't use such isolation.
This doesn't mean you blindly measure. I go through quite a few steps to minimize or eliminate ground loops. And AP's floating input helps most of the time (but when it doesn't, you have many alternatives).
I am not sure that you understood what I wrote, as you have used only partial citation of my sentence. I would want for every manufacturer of the class I product with USB input to make this USB input galvanically isolated. I am not talking about your measurements.
OP
That would be ideal.Ya a good integrated with phono pre and several line level inputs is (and has always been) the best audio component. You can always add the latest DAC to get your "i am better than the rest of you based on measurements" superiority going that direction. But in reality most DACs sound pretty much the same to normal ears unless things are completely broken.
I own Hypex and probably more other amplifiers than anybody else on this forum, and don't get hung up too much on one is better than others. Hypex is good agree, but the are not better amps just because of measurements.
Would love to see a review on ASR of 2 products. Denon PMA-1600 and the LUXMAN L-505uXII. Think the Denon is in same price family as this controversial Cambridge and just based on common sense probably better than the Cambridge. The Luxman more bucks... but in reach in that category depending on where you look.
I am afraid that any integrated amplifier will be compromised in the "N" part of the THD+N measurements, so the SINAD score will not be great and the product will be underestimated just because of this lower SINAD, here.
However, to stick with the DUT Cambridge Audio, it should have been designed to better results than we can see here.
It's about the cost and effort. It's just very recently (months) that ready-to-use fully integrated High-Speed USB2.0 Isolator chips are available. Before that everybody had to cook their own design with two FPGA's on either side of the isolation barrier which is crossed with an universal digital isolator chip.
In a DAC, you could of course isolate at a later point, right at the DAC chip's digital data and control lines.
@amirm,
Thanks for this follow-up review and nice to see you unmistakingly nailed the core issue of this product: The device quite likely pollutes its own audio signal from suboptimal internal layout and cabling.
Some of the balancing current that enters at USB (and other digital connectors) shares a ground path with the audio GND, flowing right across the main analog PCB instead of being diverted away from the analog section and its ground reference.
Internal view suggests it's even simpler and the DAC chip is on the digital input PCB (the three SO8-chips -- DualOpAmps -- seem to indicate this), creating an unbalanced local output signal which they tried to bring down to the main PCB with a short cable connector. If the GND of the cable carries any other current than signal return then this current impresses the error voltage.
It's very easy to get Signal integrity wrong in a complex product like we have here.
Thanks for this follow-up review and nice to see you unmistakingly nailed the core issue of this product: The device quite likely pollutes its own audio signal from suboptimal internal layout and cabling.
Some of the balancing current that enters at USB (and other digital connectors) shares a ground path with the audio GND, flowing right across the main analog PCB instead of being diverted away from the analog section and its ground reference.
Internal view suggests it's even simpler and the DAC chip is on the digital input PCB (the three SO8-chips -- DualOpAmps -- seem to indicate this), creating an unbalanced local output signal which they tried to bring down to the main PCB with a short cable connector. If the GND of the cable carries any other current than signal return then this current impresses the error voltage.
It's very easy to get Signal integrity wrong in a complex product like we have here.
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