Uprgrading my Metrum Octave DAC


I currently have a Metrum Octave DAC with an audiphileo-2 feeding it. I'm thinking of auditioning some other DACs in the sub $3000 range to replace it. I would prefer to have a one box solution, so am considering:

the Ayre QB-9 or maybe a wavelength Brick

Has anyone compared either of these to the Octave, or have any other suggestions?
linaeum66
I have not heard those, but have done extensive reading before buying my Octave, and I actually plan on getting an Audiophilleo 2, just like you. I seriously doubt you will find a significantly better sounding one-box solution for $3k. Moreover, the two units you list are very, very good ones, but dating from several years ago. This doesn't make them bad, but over the past 3 years cost/prices have come down a lot and I doubt you would getting much bang for your bucks.

Having said that, if what you enjoy is the sound of upsampling DACs, then all I said above is worthless.

BTW, do you run your AP2 directly into your Octave, without a coaxial cable in between?
As good as many find the Octave,the new Metrum Hex is said to be a substantial improvement(that`s impressive). See the current 6 moons review and comments.
Regards,
Forgot to mention the perfect wave MKII as another potential. I realize the ayre and brick are a few years old now, but from what I've read, they still hold their own with modern DACs.
Forgot to mention the perfect wave MKII as another potential. I realize the ayre and brick are a few years old now, but from what I've read, they still hold their own with modern DACs.
I did see the 6moons review and from that, it appears (by photos and deduction) to primarily be two Octaves in parallel, with additional logic for the new inputs provided.

Also, I don't like how the single ended outputs now require a transformer. Technically speaking, transformers are not where it's at. But I realize that the sum of all parts could be something special. (maybe I read that wrong, it seems crazy) (unless that's effectively the low pass filter in this output)

I do like that Cees is not using the same old topologies, chips and methodologies that all the other vendors seem to be permutating through.

I've had my Octave, driven by the AP directly connected to the SPDIF RCA input (wish it was a BNC) for about a year now.

Can't find anything that can touch it. Don't like the surreal sound of upsampling..

BTW, in case you have not discovered it yet, driving a TUBE preamp with the Octave sounds unbelievable. In this config, the tube preamp acts like the perfect low pass filter for the filterless Octave.

I'm using a SP17.

RM
Mccance,

I hear you: I have my Octave connected to a Lamm LL2, into a McIntosh MC275 and I'm pretty happy. I, too, wish the Octave had BNC instead of RCA.

What's your source, before the AP? I have a Squeezebox Touch, with software mods, and I'm looking at adding an AP2 in between to reduce jitter. Maybe a dedicated server later on to replace the SBT.
Lewis,

HNY to ya.

My source is a MBP running iTunes and Pure Music.

I use the free Apple Remote app to control the music selection and the SP17 remote for volume.

I can use any number of iDevices around here as a remote.

Burning my files as just wave files. Takes out the whole "which file type sounds better" issue since this is the original file.

I'm 99% 44/16 with maybe 10 higher rez albums. They sound generally a little smoother -maybe -but I find that it's really much more dependent on the original recording than the resolution.

Right now I'm just enjoying the music and about to embark on room treatments.
The Octave DAC is hard to beat, but the source is actually more important. There are two things to consider:

1) drive the Octave with a lower jitter source like Off-Ramp 5, Diverter HR or Synergistic

2) sell it and use a Wired 4 Sound DAC2 driven with I2S from an Off-Ramp 5 - this is a world class sound

Other than that, consider more expensive DACs that enable you to eliminate your preamp. The steps to good digital sound are:

1) reduce source jitter
2) eliminate or reduce the effects of digital filtering in the DAC
3) eliminate active preamp and drive the amps directly
4) couple to the amps directly using a good transformer and balanced cables

Steve N.
Empirical Audio
Steve,

Which transformer would you recommend if implementing #4?
Interesting Idea about coupling DAC directly to amp. Which DACs do you know of that are capable of doing this? I guess you just need a DAC with the right output impedance, why do you need balanced cables though?
Steve,

HNY to you.

With all due respect (and there's a LOT), it's hard to say what THE most important piece is. You could back up even farther than your "source" suggestion and talk about the recordings.

An excellent recording on 44/16 followed by high-end but mediocre downstream components will still sound better than a crap recording (mastering) on whatever rez you wish, followed by anything you wish.

To me, it ALL matters and it all matters about equally because if ANY piece is broken, it all comes tumbling down.

It's not much different than the analog chain: master>>LP>>cartridge>>tonearm>>TT>>cabling>>phono preamp>>preamp>>etc., etc.

Which one of those do you want to be really crappy? None.

Same for digital. And in my experience, this is what a large percentage of the audiophile population does not get and it results in Vinyl biggots that think digital is crap, no matter what.

Basically, they have just never heard it done right.

Regarding your list 1-4, I disagree with 3 and 4.

#3) An preamp is a preamp whether it's in the DAC or external. If you plan to control the volume, you are going to need one. The Octave does not even have a buffer and takes the output directly from the DAC chips. I choose to let a SP17 do the rest, partly because I love the ARC sound and partly because it's also a phono preamp and offers various input switching, remote volume, etc.

#4) Not interested in transformers, or capacitors anywhere they can be eliminated, especially directly in the signal path. (and yes I know the SP17 is full of caps, but that's the default world of tube amp design). Balanced cables were designed for common mode noise rejection in long runs of cables, primarily in the recording studio and performance arenas. They don't do much for a 7 inch run.

RM
"An preamp is a preamp whether it's in the DAC or external. If you plan to control the volume, you are going to need one. The Octave does not even have a buffer and takes the output directly from the DAC chips. I choose to let a SP17 do the rest, partly because I love the ARC sound and partly because it's also a phono preamp and offers various input switching, remote volume, etc."

This statement use to be true, however there are new digital-only volume control technologies that allow the DAC line-out to feed the Amps directly, and I'm not talking about iTunes volume controlling 100% of the volume here. I'm taking about completely eliminating the preamp.

"Not interested in transformers, or capacitors anywhere they can be eliminated, especially directly in the signal path."

I understand your reticence, however there are also new transformer technologies available that improve sound quality dramatically. I use simple a buffer transformer after my DAC. Makes a world of difference. Here is why:

http://www.audiocircle.com/index.php?topic=108715.0

Steve N.
Empirical Audio
"Which DACs do you know of that are capable of doing this? I guess you just need a DAC with the right output impedance, why do you need balanced cables though?"

Any DAC with low output impedance can be used, lower than 50 ohms is good. If you drive the music from a computer, then the software player can control the volume. The problem with using most DACs line-out and controlling volume using software is the danger of having max volume and blowing up speakers. As for audio quality, as long as you use a max of -10dB and no more, the sound quality will not be impacted. This means using DACs with variable gain. The danger of speaker damage is still there. Therefore, I dont recommend this technique.

One DAC that you can drive line-out and actually control volume on is the Overdrive SE. This uses a digital volume technology that does not change the data. It changes the reference voltage of the D/A. The advantage of this is that it adds no actual parts to the signal path and changes nothing in the gain stage when the volume is adjusted. The THD actually decreases as the volume is lowered, unlike any other volume technology. This volume controls all digital inputs, so it can be used with computer or Transport.

Steve N.
Empirical Audio
Steve,

I won't debate what your transformers sound like since I have not heard them. Knowing what I do about you, they probably sound awesome. I will say that transformers and extremely low distortion are typically exclusive. And, it's hard to imagine much "new transformer technology" when it's still just coil A energizing coil B. (and all the issues with that) (and there are plenty)

As far as not being able to do true balanced topology with solid state, I'm not sure why you take this stance. Every differential amplifier stage is true-balanced by default on both the input and output of the topology.

Lastly, digital volume attenuation is hardly "new." Yes, there are methods of accomplishing this with technically no distortion. To me it's all unnecessary and yet another way to have your bitstream modified via DSP and I have no interest in that.

I'm not saying any of this sounds bad or is "wrong," I'm just more of a purist when it comes to digital manipulation, as in I want none at all if possible.

RM
"Every differential amplifier stage is true-balanced by default on both the input and output of the topology."

In your dreams. Most good balanced output stages are either tube or discrete, so there are several issues that make them imperfect:

1) DC offset
2) common-mode noise
3) difference in amplitude between + and - signals (impossible to make these identical with active circuits)
4) isolation of ground between DAC and amps

A good transformer solves all of these and makes the amps sound better in the process.

"Lastly, digital volume attenuation is hardly "new." Yes, there are methods of accomplishing this with technically no distortion. To me it's all unnecessary and yet another way to have your bitstream modified via DSP and I have no interest in that."

You are not getting it. This is not DSP. This is not software. This is not even a digital chip somewhere in the signal path. This is something entirely different. This is control of the D/A reference voltage. No modification to the digital stream. Nothing else like it.

Steve N.
Empirical Audio
Steve N., you mentioned that WAV files are superior to FLAC files. Can you explain why ?
Mabonn - I can only speculate why they sound inferior to .wav.

I suppose it must be due to the real-time behavior of the CODEC software in the computer. Statically, the data is not changed, but somehow when these compressed formats are played dynamically, it changes things. I have heard it over and over in different systems.

We can debate this until the cows come home, but that is the experience I have had. Also, all of the partners I have had at RMAF shows had the same experience.

Steve N.
Empirical Audio
1) DC offset - almost none
2) common-mode noise - common mode noise is reduced in a diff amp stage
3) difference in amplitude between + and - signals (impossible to make these identical with active circuits) - hello current source
4) isolation of ground between DAC and amps - entirely different topic

You're right in that it's not perfect. You should also realize that none of this is perfect. Especially a transformer!

Transformers are for isolation and impedance matching. They are inefficient and sloppy. They are not extremely linear.

I've heard good music coming through a xformer, who hasn't. I just would not use one unless I had to.

Let's just agree to disagree. From a design methodology standpoint I prefer to keep nonlinear devices, like transformers and capacitors, out of the signal path, and bias devices in their linear region.

Here's a little review for you:
http://www.ecircuitcenter.com/Circuits/BJT_Diffamp1/BJT_Diffamp1.htm

If you bias this with a current source, it's almost perfect. Certainly as perfect as any transformer.

Balanced in, balanced out, and you set the bias voltages so you bias your next stage, which can also be fully balanced. Nothing new.

RM
In other matters, does anyone have any DAC suggestions?
Steve N., I ripped several hundred CDs (using XLD) as FLAC files. Can they be converted to WAV files, or do I have to rip them all over again? thanks, Matt
01-02-13: Linaeum66
In other matters, does anyone have any DAC suggestions?

Linaeum,

I very much apologize for the thread hijack. Didn't intend to do it and won't discuss the "other topic" any further with Steve on this thread.

I have the Octave with a Audiophilleo driving it. Just like you. I would not try to improve it unless I could demo the pieces in my own system for a few days at a time. I find reviews to be almost useless, unless they are way negative, then it's pretty safe to stay away.

Personally, I would like to try Steve's OR5 via SPDIF into the Octave, if I was to try anything. But this would not solve your two-box issue.

RM
Matt - you can convert all of your FLAC files to .wav using dbpoweramp on PC or XLD on Mac.

Steve N.
Empirical Audio
Hello Linaeum. Was wondering what you ended up with and why. I'm looking into pulling the trigger on a USB to S/PDIF converter for my Metrum Octave in the next couple of months, and the Audiophilleo is among the top 3 in my list, so interested in your findings.