Chris:Berkeley Audio Design Alpha DAC Review

[roccoriley]

In the review above you say " I used the Lynx card as my digital I/O for the AES/EBU output and I used the Mac's built-in TosLink output as another digital I/O. Hardly a fair comparison, "

 

Could you comment further on that observation? For example, one could conclude that the Lynx is adding/modifying the raw data and the next question would be what mods is it making as opposed to the unmodified data coming from the toslink card to the DAC. This would suggest that the data arriving at the DAC would be different from these two sources, right??

 

And also: " As a test I connected the Alpha DAC to a pre amp and was so disappointed I reverted to the pre amp-less configuration in under two tracks. "

 

I would appreciate if you could comment on the manufacturer's feelings about the difference in quality. (For example, my amp only has one set of inputs from the preamp therefore if the sound is degraded by a preamp I would have to manually disconnect the preamp cables and connect the DAC cables.) Was your preamp "Audiophile Quality" (whatever that means anymore)? Would this effect be expected from any preamp or just certain ones?

 

Thanks

 

RR

 

 

 

 

 

 

 

[audiozorro]

A good way to determine what that means and how to achieve it for your system is provided here:

 

http://www.high-endaudio.com/RC-Linestages.html

 

 

[jonmarsh]

First, setup normally, Chris's point is that with the Berkeley it's very easy to see that by sampling rate and HDCD indicators if your digital system is NOT modifying the digital stream- and in the case of the Lynx, that should definitely be the case- it's simply one of the easier/better ways to achieve a fairly low jitter SPDIF or AES/EBU output from the Mac Pro. Using the TOSLINK output would be like using a space saver spare on an NSX or Lambo. It will get you there, but certainly not in style.

 

What is an "audiophile" quality preamp? Where does that performance/price range start/end? It's a similar question to "What is an audiophile quality DAC?"

 

I'm not Chris, but I have been using the Alpha DAC with an Ayre K5, which is about a $3K preamp with zero loop feedback configuration fully balanced input to output (i.e., the active circuits are all balanced, even for the unbalanced inputs). It has many positive reviews, and it a very good performer in it's price class, often compared with units at 2X the price. It also has input selection and volume control via a remote- But it's fortunate, IMO, that it has a Home Theater bypass mode, because that is how I use it with the Alpha DAC. IMO, the Ayre does slightly soften and cloud the sound- VERY slightly, but in comparison to my DIY passive preamp, it is audible. Now, since Ayre makes the quite stunning KXR preamplifier also, for about 6X the cost, you could say that a fully reference preamp is available- at a price. Is that where audiophile quality starts or ends? Or is it at $3K or some other lower point? Your call to make. But unless you have a real reference quality preamp, not just "audiophile quality", then having an option for bypass mode may be a good thing IF the remainder of your system configuration renders the differences audible. In many cases, you may be quite happy retaining the convenience and functionality of your preamp. Since I'm running balanced with both the Alpha outputs and the Ayre outputs to my power amp, there are no compatibility or configuration issues.

 

Hope this helps.

 

~Jon

 

[The Computer Audiophile]

Hi RR - Good questions. As stated above, the Lynx I/O card is a far better digital I/O implementation than the Mac's built-in optical output. While, "one could conclude" that the Lynx is adding something, I'm not quite sure the path one would be taking to that conclusion. The data arriving at the DAC is the exact same, but there are likely significant differences in timing at the very least.

 

The decision to use a preamp or not is very personal and depends on one's system. I have yet to hear a system that sounds better when adding a preamp to the Alpha DAC -> amp combination. Eliminating extra circuitry, interconnects, and any other possible sound degradation is a good thing in my opinion. However, one may need a preamp if their system requires more gain than a DAC can provide.

 

In a way using a preamp in some instances would be like wearing eye glasses even though you don't need them.

 

[cfmsp]

 

"In a way using a preamp in some instances would be like wearing eye glasses even though you don't need them."

 

Interesting comparison, Chris, since it is rather well known that different colored lenses (in glasses) increase one's acuity in certain aspects of our vision. Rose colored glasses, as an example, do serve a quite useful function, say, when skiing ungroomed terrain in flat light, by increasing contrast (I believe).

 

Differences between amps and preamps are likely of a similar magnitude, altho not as obvious due to our better visual acuity, as opposed to aural acuity.

:0

 

 

 

[roccoriley]

Thanks for all your comments.

 

Chris; I see that you have a MAC with Lynx card. I suspect that at some time or other you may, possibly, have conducted an A/B comparison with the MAC/Lynx vs: MAX Firewire, both to the same DAC. If you have done so could you please comment on any differences you observed?

 

Thanks Again!!!

 

[jonmarsh]

Couldn't agree with you more, Chris- sometimes you may feel you "need" a preamp for control features (remote, input selection) or cable drive for long signal runs, but I've never seen where it "improves" the signal- you can only lose resolution the more components in the chain. It's not like using a UV or polarizing filter on a camera, IMO.

 

[Charles Hansen]

A good preamp always improves the sound. If it doesn't it's because the preamp isn't good enough. The editor of a magazine was testing the KX-R. He put it into his system and ran a bypass test using the variable outs on his DAC. He went back and forth several times, noting that according to all logic, it should sound worse with the preamp in the chain. But it didn't, it sounded better. That has been my experience too. I can't explain it, but I have experienced it.

 

[barrows]

Jon,

 

The K5 is an excellent preamp, while I agree with your comment that it "softens" the sound a little, what is really great about the Ayre is all the things it gets right-it does not truncate the harmonics and decays the way so many preamps can.

Jon, have you gotten the MP upgrade for your K5? If not, do not hesitate in getting this done. I expected a slight improvement in performance from this mod, but I was quite impressed with the improvement-I will avoid the typical audiophile hyperbole here, but believe me, anyone who has a K5xe should get the MP upgrade done as the improvement is not subtle.

 

[Charles Hansen]

Hi Barrows,

 

I sent JonMarsh a private message saying the same thing. Thanks for saying the things that I wasn't supposed to say myself on a public forum! I'm glad you are enjoying your preamp.

 

[jonmarsh]

Thanks for the comments and follow up- I have been hearing only good things about the MP upgrade, and from my perspective, it's mostly just a question of scheduling- Ayre is pretty busy doing these now, and I'm just plain pretty busy (in Europe two weeks on business right now, back in CA about the 25th of this month.

 

[Audio_ELF]

The pre amp is not only designed for volume control and source switching, but in many cases will change the impedance presented by a source (CD player, DAC, etc) into a good impedance for the power amplifier - in many cases the desired impedance of a power amp is not the same as the impedance of the output of the source.

 

Thats not to say that a source can't be set up to present an impedance which is suitable for a power amp.

 

Eloise

 

[jonmarsh]

Certainly a valid generalization in many cases; it depends greatly on the specifics of the source components and load components. This loading aspect is one reason the Ayre KX-R offers an input impedance of 2 MegOhms, but for the same reasons, the Ayre MX-R monoblock power amps offer the same high input impedance. With this situation, it's usually the cable capacitive loading that will have the greatest impact on the source component.

 

OTOH, the K5xe does not reflect that design philosophy change at Ayre, showing an input impedance of 20 kOhm single ended and 40K balanced- similar to many conventional solid state power amplifiers, such as Aragon 8008 series. This gives a better noise figure when the input isn't terminated. OTOH, the V5/V6 series has an input impedance of 100 kOhm, so in some cases we might argue for driving the amplifier direct- if loading is a factor.

 

This disparity in input impedance does illustrate the issues with resistive based attenuators for passive preamps, and makes a case for the benefits of transformer based options, apart from cost, bandwidth, and expense.

 

The source impedance and current drive will vary depending on the technology type and design- it's not unusual to see 75-300 ohm source impedance for soild state components, but of course, somewhat higher for vacuum tube equipment, depending on topology and tubes used.