Updates and where to find them are listed here
 
1. 22/23 November: Added comments to 'Part (a) Highs'  based on listening with my old Stax Lambda Pro. Obviously, the Corda Concerto was not involved.
 
2. 20/21 December: See post 48 (p.4) for tentative comments of Beyer T1 with Stagedac/Concerto versus Bifrost/Lyr.
 
Review
 
The following review compares a non-usb Bifrost with an Eastern Electric MiniMax DAC (tube switched out). In a follow-up post, I will compare the Bifrost and Stagedac.
 
These units were connected via TOSLINK to a MacMini with mostly ALAC and WAV material hosted in iTunes. Where noted, some material was iTunes purchased (256Kbit). There was no special cabling - about cables I am in the “don’t know” camp - except that I use a New Zealand made ‘twisted pair’ interconnect called Taranui. It uses high quality plugs, looks good, and cost only slightly more than a department-store cable.
 
Amplifiers used were the Corda Concerto and, in part (b) of this comparison [still coming], the Schiit Lyr with stock GE 6BZ7 tubes.
 
Phones used were Audez’e LCD2 rev 1 and Beyerdynamic T1. In part (b), my aging Stax Lambda Pro makes a cameo appearance.
 
Both DACs were calibrated using pink noise to listening levels of 80 (actually consistently around about 80.4) dBA on my SPL meter (+/- 1.5dB claimed accuracy @ 1KHz).
 
The Bifrost delivers 2.0Vrms and the MiniMax 2.5Vrms. With the Concerto’s 8db gain (high gain mode) used for all the listening in part (a), this difference corresponded to 2dBA. Conveniently, this was ‘3 clicks’ out of 64 on the Concerto’s volume control. This was an easy adjustment to make when switching DACs, thanks to a LED adjacent to the volume control. The LED toggles between lit and unlit with each ‘click’. This previously slightly puzzling feature of the Concerto now makes complete sense.
 
Part (a) was conducted at 36-80 hours of active burn-in (see below). Assuming factory testing occurred as described, 24 hours can be added to this figure. Hours left turned on but with no music playing would add another 20 hours.
 
Next, I get straight into the details of listening and what I found. Read these details as what differences ‘sounded like’, rather than ‘what they are’ necessarily. Of course, this is all to my ears, IMHO, YMMV and so on. This said, I only report ‘large’ differences. The smaller or more subtle it is, the less it's worth reporting. Variation in hearing and perception from person to person will soon mask small effects.
 
Because it could strike some readers as unnecessary, boring or self-indulgent, I have placed details about me, my preferences and how I approached this review at the end. Indeed, skipping this part is recommended!
 
 
I have no view concerning burn-in. I am happy to follow designers’ recommendations whether to worry about it or not, and how long to use.
 
In this case, my first impression of the Bifrost (see below) led me to check Hero Kid’s excellent inventory of Jason’s announcements and responses. Although it struck me as a fairly casual issue to Jason - he had to be asked after all - his answer on this point was that all units are burned in for 24 hours at the factory, and their amplifiers benefit from 50-100 hours after that. He suggested a similar period would apply to the Bifrost.
 
Burn-in used mostly various iTunes playlists, and in one case two hours of pink noise.
 
I may have noticed subtle changes in the Bifrost’s sound beyond 36 hours, but I wouldn’t bet on this being the electronics. It could just as easily have been me learning its sound.
 
 
First impressions
 
The Bifrost arrived one or two days sooner than expected. I had just listened to five tracks earlier that morning. With the Bifrost barely warmed up, I listened again. I had not equalized levels at this stage; this was not an A/B. Based purely on audio memory, my impressions were the Bifrost was exceptionally clear, had excellent attack, seemed over-bright and a touch thin, and - straight out of the box - just might be a little wearing with extended listening.
 
36 hours
 
At this point all sense of over-brightness and/or thinness had gone. Clarity remained, attack featured less, and the unit now sounded very natural. At this stage, I started serious A/B listening.
 
Because I established brightness had “gone” with the LCD2 rev 1 - which is sometimes described as ‘dark’ - I re-checked using the T1 a few hours later. Again, the Bifrost no longer seemed bright to me compared to the MiniMax.
 
However, I shall come back to this point.
 
Similarities
 
Sound-stage. I’m not really a sound-stage sort of person, especially with headphones. Even when I do notice, it soon disappears from my attention as I get into the texture and weave of the music. Nevertheless, the following was an interesting experience.
 
When I decided to start serious listening, I cued my first track to the MiniMax. Several repeats later, I switched to the Bifrost. “Aha”, I thought, “the Bifrost has a much wider sound-stage, and focuses much more precisely too”. Somewhat elated at how easily this first ‘difference’ had shown itself, I switched back - after a few more repeats - to the MiniMax.
 
“Aha”, I thought, “the MiniMax has a much wider sound-stage, and...” - well, I’m sure you get the idea.
 
I declare this a dead heat. Both the MiniMax and Bifrost do sound-stage very well to my ears.  As I say, I’m not really a sound-stage guy, so if others reliably hear differences or pick up subtleties I don’t, I won’t argue.
 
Speaking strictly for myself, I found this ‘first-change’ or ‘novelty’ effect interesting, and something to watch out for. By the way, the effect disappeared after a while. I guess I learned to screen it out.
 
Detail. With one qualification which I detail below in ‘differences’, I found both DACs very detailed and resolving. Otherwise, I could not identify any reliable differences at all.
 
Differences
 
This is the crux of this comparison. In some ways, the differences are easy to describe; in another way, somewhat hard. I tried hard, but could not avoid a flowery analogy at the end.
 
Bass. The MiniMax does bass just slightly better. The difference is significant enough a bass-head just might prefer the MiniMax. It is easiest to detect with low-tuned bass-guitar and drums. With bass-notes, the Bifrost just seems to play the string’s core note, whereas the MiniMax presents more of the textural and timbral change as the note decays on the string. With drum, the Bifrost focuses more on the ‘tap’ or ‘beat’ of the drum stick on the skin of the drum, whereas the MiniMax reveals this and more of the ‘boom’ of the body. In one track, with kick-drum, the reverberation or resonance seemed to be picked up and repeated by the platform or stage. The Bifrost presented this information just as capably, but it’s the MiniMax that renders it more viscerally.
 
Two more examples are worth citing. Both DACs revealed the ringing of the body of a cello (Susan Sheppard, BachCello Suites, iTunes plus) equally capably, yet the MiniMax prolonged the ringing of the lower notes, the Bifrost the higher notes and harmonics. This was a somewhat unique listening experience.
 
This was equally evident listening to sections of Beethoven’s piano sonatas (no 29 and 32, his late work which frequently features hands wide apart on the keyboard., i.e. lots of low bass and upper mid combined). With the sustain pedal held down, the MiniMax holds on to the lower notes for longer, and tends to add a ‘richer’ sound to the chords than the Bifrost. However, the Bifrost produces the upper harmonics more articulately.
 
Which DAC is the more accurate or neutral sounding? Although I played piano for many years, it’s impossible to say. My suspicion is the MiniMax has been deliberately voiced on the warm side. It slightly exaggerates the bass and lower mid, and just slightly ‘swamps’ information the Bifrost may be presenting with more balance. The effect of this is to make the Bifrost seem the brighter of the two on a lot of material, or just ‘clearer’ on other material.
 
Clarity and ‘blackground’. The Bifrost has retained its initial impression of clarity throughout my listening. As I think my notes above suggest, the MiniMax has a warmth that adds just a touch of lushness. To repeat, the tube was left out of circuit throughout. Although I really don’t think there is any real difference in detail, the Bifrost can sound the more detailed.
 
The notion of ‘blackground’ - of dead silence between notes - seems to appear most often in discussions of some (usually solid-state) amps. Yet this is an easy description to apply to the Bifrost. When there really is a pause in the music, sound emerges noticeably more suddenly with the Bifrost. When the music is playing continuously, there is still a sense of sharper, clearer edges or better definition to the notes. I hasten to add this is not ‘digititis’. The Bifrost sounds very natural. Again, if I have pinned things down accurately in the section above, it is likely the MiniMax sustains bass and lower-mid notes and resonances longer. These play over the top of and ‘swamp’ micro-details and micro-textures which are there but one has to listen harder to hear them. The Bifrost does not have this ‘problem’, revealing these fine textures and details with relative ease.
 
Highs. I hesitated slightly whether to include this note, as it’s more subtle than what I’ve described above. However, I think there is just enough evidence to say the Bifrost does detail in the highs just noticeably better than the MiniMax. There is a fraction more detail: for example, more splash with cymbals, more definition (and ‘sharpness’, where near walls are involved) in the echo and reverberation of the venue, more air in general.
 
Update 1- Stax Lambda Pro comparisons: Use of the Stax 'phones did make some differences easier to hear. With slower, less energetic tracks especially with less direct high content e.g. from hi-hats, any difference - if it is detectable at all - is a subtle one of being more "lit" (Bifrost) or slightly darker (MiniMax), as noted in the original summary below.
 
There is an energetic hi-hats layer in Feral (Radiohead, WAV) present through most of the track. Quite noticeable and not at all subtle was greater extension, shimmer and hence 'detail' with the Bifrost. The MiniMax contrastingly seemed 'dull', almost as if the cymbals were being held.
 
The fast, energetic guitar/percussion track Hanuman (Rodriogo e Gabriela, iTunes+) brought out another aspect. The MiniMax gave more body to the guitar chords, whereas the Bifrost put more emphasis in the higher-frequency components of the percussion. Bifrost could thus seem to have more attack, although I am satisfied both were equal in this area. Interestingly, both 'versions' were equally terrific to listen to. I suspect this might be true of many energetic tracks, which provide enough fast-paced material that each DAC highlights a different aspect of what is in the music, rather than seeming to have anything missing. 
 
Summary. As a final observation, my extended listening sessions often made me feel the MiniMax could be described as relatively dark, the Bifrost as ‘light’. I have deliberately avoided repeating the word ‘bright’ as I don’t think that accurately describes the Bifrost. Both DACs are very detailed and resolving. Yet there are differences between them: subtle but noticeable. With the exception of what I noted in the low bass, the same information can be heard with both DACs.
 
The difference - especially from the upper mids on up - is one of emphasis, and here I cannot resist a visual analogy. Picture a clear sunny day, perhaps in the fall. Everything can be seen clearly, but the MiniMax puts things in the shadows where they are lit more softly and perhaps a touch more romantically or - if you prefer - ‘organically’.
 
On the other hand the Bifrost puts things right out there in the sunlight. I’m not talking harsh, midday sun here; just crisp clarity. There is light and shade, and there is texture and there is detail.
 
Overall impressions
 
I am surprised by some of these findings with my “usual” rig. The MiniMax was my preferred DAC in my headphone rig, partnered with the Concerto most often, the Schiit Lyr nearly as often, and both usually driving the LCD2. I usually described the MiniMax as transparent, detailed, resolving, and especially “lively”, driving the Concerto in particular with a lot of life.
 
I am now inclined to think the Bifrost has the better synergy in the Concerto - LCD2 chain. I am no longer sure I can describe the MiniMax as ‘transparent’, or perhaps I mean it has a very slight but musical coloration. On the other hand, in my listening so far I find this suits the (Concerto-driven) Beyerdynamic T1.
 
Is the Bifrost ‘as good as’ or even ‘better than’ the MiniMax? The MiniMax is a mid-priced and perhaps mid-fi DAC but it has won a reputation as something of a giant-killer and a real bargain. Reportedly, the recently released MiniMax-Plus may be better, sounding more detailed and having better blackground. In other words, bringing it closer to some of what I’ve described about the Bifrost.
 
I really cannot answer this question: I have far too little experience with DACs for one thing. What I can say is the Bifrost seems to me to be a different DAC with different qualities from the MiniMax but the same capabilities and no faults or weaknesses that I could detect. This seems to me a really fine achievement for a first DAC from a young company (albeit a very experienced design team) at this price-point.
 
Some may recognize the qualities they are looking for in the MiniMax after reading what I’ve described above; others the Bifrost. That, after all, is what a review should be about in my humble opinion.
 
 
[due late November]
 
 
Boring bits about me
 
I have been a “speaker audiophile” since 1985, when I bought my first component system. Although I bought a pair of Stax Lambda Pro in 1992, and Grado RS1 about four years ago, I did not really take headphone listening seriously until I heard the LCD2. I am still a speaker person, and consider I am inexperienced with headphones.
 
Incidentally, considering highs with speakers tend to attenuate rapidly in a typical listening room, this may explain why the LCD2 sounds ‘natural’ to me. That said, my speakers ironically seem to significantly out-perform the Audez’es in this area, at least with much material.
 
I am not a bass-head, but considering my preference for Beethoven over (for example) Mozart, and the fact my Stax Lambda-Pro “didn’t do it for me”, it might be said I like bass. I appreciate the bass texture available with the LCD2 for example. I played piano for many years - not professionally but good enough to be able to play most of what I wanted to, and to accompany some of my classically trained friends - with far better skill levels than me I would add. I used to enjoy improvising for many hours.
 
I regard piano to be the one instrument I know intimately. Actually, to this I can add I’m pretty good at unscrambling words in recorded conversations of 4-6 people talking simultaneously, together with noting inflections and other changes in their voices. This needs a distinct set of listening skills. No, I’m not an electronic eavesdropper. This concerned experiments conducted in our social laboratory years ago. Unfortunately, I got to spend many, many hours transcribing these conversations in excruciating detail.
 
Apart from classical, other genres I listen to - probably more than classical these days - are Euro-jazz (e.g. Eberhard Weber, Thomas Diethelm); blues, blues-rock, gothic, some electronic, pop/rock. Actually, pretty much anything.
 
Most of the work I do is pure research, and development of robust, reliable and valid measures is often a key aspect. As will be obvious from the above, my review contains none of these things: in fact, it couldn’t, as the tools I use require development of scales that are then validated with samples of raters and ratings. I am largely untroubled by this. Audio is one of the things I do to relax. Until we have the makings of a comprehensive model that can account for all the data in this hobby - e.g. how people apparently hear things they shouldn’t be able to - we have little scientific basis to say anything at all.
 
Nevertheless, I did try to follow some method. My first problem was to identify tracks from those I am very familiar with which showed differences between the test units, supposing I could find any. By the way, it turned out finding these tracks wasn’t hard. Once I found the first few of these, I constantly returned to them as my ‘reference points’ as I gradually brought in other material. I spent about 3/4 of my time A/B’ing tracks or parts of tracks. The rest of the time was spent on extended listening.
 
I also re-calibrated frequently. This was more important than I expected. To my surprise, listening levels changed by 2-3 dBA from time to time, possibly a time-of-day effect. I live in an intensive farming area with a great deal of heavy equipment. It may be power into my home was sagging come - e.g. - milking time.
 
Two problems I paid some attention to were: (a) effective listening stops when I get tired; (b) effective listening also stops if my mind is “chattering” (thinking - or is it those voices I can't get rid of?) while the music’s playing. When either of these occurred, I took a break.
 
There are many cognitive priming and other effects that, possibly, might invalidate a review like this. Without disputing the possibility these applied here - meaning in fact there is no difference between these DACs, or alternatively that I failed to hear other large differences because these effects masked them - it is interesting to note that on three occasions I thought I had falsified a difference previously found...only to discover I was actually listening to the other DAC. This made me modify my procedure to ensure I knew exactly which ‘experimental condition’ (DAC) I was collecting data for at each step.

 
 
A picture tells a thousand words. The following tells nothing except that I take bad pictures, but I include it anyway:
 

Shown in my ‘DAC stack’ are the DACs themselves, arranged in the same order as the “dial” I used to set levels (see toward the end of this report for a picture and explanation).
 
Highest is the Schiit Bifrost, as it needed the highest volume setting to reach the listening level set. Below this the Meier Corda Stagedac, and finally the Eastern Electric MiniMax DAC takes the lowest tier.
 
Compared over some two weeks, I found these DACs to perform well within the standards expected of recent-generation audiophile-grade product. By this, I mean standards such as ‘acceptable’ neutrality (more about my use of this word below); musicality; and being free of obvious flaws.
 
Yet I heard differences that gave each its own subtle sound-signature or flavor.
 
These are as follows.
 
Schiit Bifrost. This DAC tends to the bright side. It offers outstanding clarity throughout the range. This clarity works well in conveying bass detail, but at the expense of slightly less bass presence; for example lower harmonics are either absent or less emphasized. This DAC tends very slightly toward dryness; i.e. harmonics decay more quickly than with the Stagedac, and considerably more quickly than the MiniMax (the latter may be because of the MiniMax’s favoring of lower harmonics in the mix - see next). I suspect this subtle dryness contributes to the Bifrost’s clarity.
 
Given the characteristics described above, one might ask whether this DAC has flaws such as being over-dry or lean, edgy or sibilant. It is none of these things. It has clarity and a touch of brightness or - as I described it in part one a more “lit up” quality -  whilst still conveying body and sounding convincingly ‘natural’.
 
Eastern Electric MiniMax DAC. This DAC tends to “the dark side”, bringing with it more bass and/or lower mid warmth that gives greater harmonic richness throughout the range. Occasionally, this obscures fine detail in the upper mids, but also brings some bass excitement; see comments under Stagedac. Otherwise, impressions remain exactly as reported in part 1.
 
Despite the greater warmth, there are no flaws such as muddying of the sound or unnatural darkness. Detail is there, just as it is with the Bifrost. What is different is the subtle change in emphasis.
 
Corda Stagedac (Crossfeed: OFF; Tonal balance compensation: OFF; Filter position: 2*; Oversampling: 8x; Volume control: DEACTIVATED). This DAC tends to the neutral side. Unlike the other two, it favors neither the upper nor lower registers. Because of this, it might seem boring on first listen if one comes to it directly from a darker or brighter DAC.
 
This impression changes at once upon listening to vocals. The Stagedac produces an up-close, intimate, very detailed portrayal of voice, especially in the lower and middle vocal range (i.e. male voices and lower to middle female voices). The effect corresponds closely to what is described in head-fi’s wiki Describing Sound - A Glossary under Presence Range and Presence. If a heightened presence range is the explanation, it is a very light boost noticeable with voices but not - that I could detect - with instruments.
 
Nevertheless, the effect on vocal detail is not subtle. Fine adjustments in voice level, subtle timbral changes, and larger details such as a slight ‘croak’ in the back of the throat at one point in one track were presented absolutely clearly. This last detail I had not noticed before. It was also "decoded" with the Bifrost - but only once I knew it was there (from the Stagedac) and listened for it. The Bifrost still presented it less clearly than the Stagedac. The Stagedac gave more detail and the sound seemed to last longer. The MiniMax presented this detail “muffled”. It remained difficult to tell it apart from other instruments or something in the studio.
 
Another track I have listened to since the late 1980s (Plants in my head) contains a low-level falsetto for the first 45 seconds. I had not noticed previously that this 'voice instrument' (Diethelm is a guitarist and this essentially is instrumental jazz music) sounded almost continuously throughout this 45 second introduction. With the other DACs, the lowest level of his vocal accompaniment simply could not be heard in the middle of this 45 seconds. 
 
The effect of this heightened vocal presentation is that emotional layers and nuances are far more present than with either of the other DACs. A number of LCD2 owners have commented on its ability to make vocals, female especially, sound intimate, emotional and real. I normally use the Stagedac in my speaker rig. I had not previously found this vocal quality to be part of my LCD2. With the Stagedac, the LCD2 was indeed all of these things; at times, fantastically so.
 
I searched hard for evidence of this 'highly expressive' quality in instruments such as violin, viola, guitar etc. I listened carefully to one of Beethoven’s String Quartets; his Piano Sonata no 32; Bach cello; jazz and other pieces. Whilst this was an excellent listening experience overall, I found the Stagedac no more expressive than the Bifrost with non-vocal material. In other words, to notice this difference there is need for voice in the mix.
 
Continuing with instruments the MiniMax, whilst less “clear” than the Bifrost in particular, compensated with its richer presentation of (e.g.) lower piano chords and cello, and almost palpable presentation of (e.g.) low double-bass.
 
One other effect I found pronounced in the Stagedac is that it renders notes in the upper mid range more sweetly, and with longer decay than the Bifrost. Whilst it did not seem to me to sustain harmonics to the same degree as the MiniMax, remember I found the MiniMax has a bass and lower-mid focus that sometimes washes out subtle detail higher up. Like the Bifrost, the Stagedac lives higher up in the sound-spectrum.
 
A sweeter, more bell-like quality to upper piano notes and a more ‘unbroken’ or ‘continuous’ quality to brushwork on cymbals is the result, especially compared with the Bifrost. The Bifrost sounds subtly drier, giving upper piano notes a slightly leaner, less resonant, more damped quality; and brushwork just very slightly - I am forced to exaggerate greatly here! - more of a fast “tap-tap-tap” than brushing sound. Of course, this is consistent with the Bifrost's clarity: its ability to clearly separate individual notes.
 
Possibly related, the Stagedac often produced a more ‘delicate’ sound with instruments present at lower levels in the mix. This was noticeable - for example - with the second guitar (right hand side) of Johnny Cash’s Give my love to Rose. It stood out, even though it was softer. With the other two DACs, it tended to be disappear more into the overall sound.
 
In fact, this last quality was also evident with vocals. A voice might drop almost to a whisper, yet it still stood out clearly in the mix compared to the MiniMax and even Bifrost. There was no loss of contact with the vocal line and its intended emotional message.
 
Sitting between the MiniMax and Bifrost, the Stagedac reaches both the highs and the lows in a less pronounced way but with excellent definition. Overall, it sounds closer to the Bifrost than the MiniMax - on a relative scale with MiniMax representing “lows” and Bifrost “highs”, I would put the Stagedac about 3/4 toward the Bifrost side.
 
An important note is that with about one fifth of my 11 test tracks, I could hear no differences between the Stagedac and Bifrost at all. The two cases were Feral (Radiohead, The King of Limbs, WAV) and Hanuman (Gabriela y Gabriela, 11:11, iTunes-plus download). Statistically, a sample of 11 is small, and insufficient to generalize to a firm ratio; YMMV! This may be material-dependent.
 
With the exception of what the Stagedac achieved in my system with vocals, it seems to me the Stagedac comes closest to Lunatique’s definition of “neutral”. That is, it presents excitement where there is excitement, boring where there is boring. 
 
From brief exchanges with Dr Meier concerning his amplifiers a few months ago, I suspect this is exactly his goal.
 
* The Wolfson WM8741 chips used in the Stagedac offer the ability to select among 3 filtering and 3 oversampling levels. Dr Meier chose to implement these options. I had no intention of conducting this comparison at every one of the nine combinations! My first inclination was to choose “classic” sin(x)/x approach to decoding. However, few Stagedac owners use this setting. I have not noted any particular consensus concerning the 3 or 4 most common settings. As differences are hard to hear, I settled on filter 2 - slightly reduced pre- and post-ringing - as a compromise.
 
Summary. Whilst I appreciate these DACs are based on different chips, one could easily believe all are cut from the same basic cloth. All bring high levels of detail, but how this is handled - presumably in the analog circuitry that follows - brings subtly different qualities to the listening experience.
 
Once again, I cannot nominate a “best DAC”. Each seems to be "best at" something important. As before, the choice is dictated by preferred sound signature or, it may be, best compromise.
 
In fact, my ‘findings’ create one or two problems. One might reasonably have hoped “all DACs sound the same”. It would then have been simple. Buy the cheapest and be done with it.
 
That said, in most ways these DACs do sound the same. That is, all the detail is there, the frequency range is respected albeit subject to subtle tailoring here and there, they are all musical and - to my ears and level of expectation - free of flaws.
 
As well, if one did not carefully compare with other DACs, one might well be completely happy with any one of these for a long time.
 
All the same - this is the second problem - why not these qualities in one DAC: palpable bass; vocal magic; great clarity? Instead, it appears different engineers have subtly different ideas of “neutral” or “good”. Deliberately or not, these carry over into subtly different sound signatures. Maybe one cannot have one thing without losing something somewhere else. The result is each acquires distinct strengths and weaknesses.
 
Mere speculation. A practical effect this comparison has had on me is to make me re-evaluate my system configurations. I pretty much subscribed to the “they’re all the same” principle, and even though I noticed the vocal dexterity of the Stagedac when I first received it, I thought no more of it! With the MiniMax, I noticed little more than good dynamics and musicality. As for the Bifrost, let us not forget the price/performance ratio here. For me this has been a worthwhile and illuminating exercise.
 
To do mischief to Socrates (or Heraclitus or whoever said it first): "Audiophile, know thy equipment!".
 
Other observations
 
The Lyr did not change the relative sound signatures of Bifrost and MiniMax. My impressions of the Bifrost and MiniMax remained exactly (i.e. indistinguishably) as reported in Part 1 with the Concerto. This would seem to show that both amps are ‘transparent’ or, if you prefer, transparent enough.
 
What about synergies? Disappointingly, I cannot comment on this. I did not directly AB the Concerto and Lyr. The Concerto was used for one 10 day period; the Lyr in another 2-3 week period. I did surmise the Bifrost and Lyr would be a special pairing; similarly the Stagedac and Concerto.
 
There may be differences in synergy among the various combinations of amp and DAC. Not surprisingly, given they were not AB’d, differences were not evident. But as well - see below - other changes might easily have obscured them.
 
LCD2 dependence on DAC and amp. It has become a rule of thumb on head-fi that the LCD2 and 3 require a certain amount of power (generally about 2W) to sound their best, and that they scale well with amplifier quality (whatever this may mean).
 
A few proposed that DAC is equally important. I am now a believer! It is a surprise - to say the least - that one of the LCD2’s paramount qualities (voice) as reported by many turns out to be rather DAC-dependent - at least in my system.
 
Problems
 
Lyr and GE6BZ7s. Although these are not my preferred tubes, previously I have thought well of this stock option. The GE 6BZ7s are reasonably neutral, provide good detail, and are not syrupy as I found the stock JJs to be. Imagine my surprise after completing the Concerto and Stax Lambda Pro phase of this review on finding the Lyr’s sound had become muddy, slow and unsubtle.
 
I reasoned it would take only an hour or two to re-adjust to this. It took over two days before they sounded ‘right’ again. I have no idea whether this was an effect of coming directly from the Stax; moving from my usual tubes which I hadn’t heard for over two weeks; or some other factor (temporary insanity?). An interesting test for the future perhaps.
 
This highlights the degree to which the Lyr's sound alters with tube-rolling, even though it is a hybrid rather than pure tube-amplifier. The Concerto is what it is, take it or leave it. The Lyr is a much more slippery animal.
 
Therefore, the question cannot be not "does the Lyr have great synergy with the Bifrost (or whatever)", but "does this Lyr/tube combination have great synergy with..."?
 
Level matching. Unlike the Concerto, the Lyr provides no easy way to re-set levels. In the case of the 3-way comparison - each DAC provides a different output voltage - I would have had to re-measure SPL to re-set the volume control every time. A nightmare!
 
I thought of various ideas in the course of 3 days to make this easier (too many ideas has always been a problem of mine); speed and practicality decided this choice, below:
 

A plastic cap fits over the Lyr’s volume knob, anchored tightly in place with two small pieces of thin, hard rubber. This ensures the cap does not slide over the knob as I turn it. A pointer is glued to the cap. It reaches about 3.5 inches (9cm) from the centre of the knob to its sharp point. You can see a set-square does duty as my scale. The ruler (cm/mm side to pointer) was set as close as possible to the pointer (without touching) to reduce parallax.
 
SPL levels were set as before to a target of 80dBA. As before, my meter oscillated between 80.0-80.4 dBA during each calibration event; that is, within the same measurement this was the range of values shown. I checked levels at the beginning of every session, the end, and - initially - at every changeover and/or at approximately 20 minute intervals if there wasn’t a changeover. This became less and less necessary as this crude gauge turned out to be very accurate at re-producing levels.
 
For interest the numbers for each DAC were:

• 3.2mm Bifrost (2V rms, needed the most gain)
• 2.7mm Stagedac (2.2V rms)
• 2.2mm MiniMax DAC (2.5V rms, needed the least)

 
(These figures don’t quite square with the rms values: the Stagedac should be closer to the Bifrost than MiniMax side. Instead it is halfway. Given each of these values has a tolerance of +- .05V as presented, the levels on my scale are within bounds. Simplest would be to think my Stagedac put out 2.25V rms).
 
(Mathematically inclined readers will soon turn these figures into relative amounts of turn on the knob from the dimensions I've given. BTW, position 2 is pretty close to 10 o'clock. The position shown in the picture is position 1, the Bifrost).
 
Warm-up. I turned off the Lyr overnight and when working away. I noticed on checking SPL right after turn-on it was 1dB down. I didn’t adjust this right away, instead checking it again 15 minutes later. It had ‘returned’ to its normal level. 
 
Lyr owners, assuming this was not a coincidental mains-power effect, it is worth bearing this in mind. If you listen loud, allow warm-up time before you set your listening level. It may get louder on you without you noticing!
 
Why didn’t I include the Stagedac in testing with the Concerto (Part 1)? Ahem, concerning the Concerto’s volume control, I noted the convenience of there being exactly three ‘clicks’ to equalize the levels of the MiniMax and Bifrost at my chosen listening level. Unfortunately, the Stagedac’s output is about halfway between. I cannot move the dial “one and a half clicks”. I’m sure there are ways round this, but none I can do quickly. Perhaps at a later date.
 
Tracks used (redbook, ALAC unless otherwise noted)
 
Main listening:
 
Lydia                                    Fur patrol                Pet
       Fur Patrol is a New Zealand pop/rock band, slight goth/grunge feel; female vocalist
Give my love to Rose          Johnny Cash             American IV: The Man Comes Around
Moby Dick                            Led Zeppelin            How the West was won
String Quarter #14, 7th        The Lindsays            Beethoven: The String Quartets, 9
Piano Sonata no 32             Michael Houstoun     Beethoven late piano sonatas
Feral                                    Radiohead                The King of Limbs (WAV)
Hanuman                             Rodrigo y Gabriela   11:11 (iTunes-plus)
Ces petits rien                      Stacey Kent              Breakfast on the morning tram
Cello suite no 1: gigue         Susan Sheppard       Bach Cello Suites (iTunes-plus)
Plants in my head                Thomas Diethelm      Shaved
Catch your body                  Thomas Diethelm      Shaved
 
 
Occasionally auditioned to double-check qualities noticed in a main track:
 
Bass ‘N’ Drums                    John Paul Jones        Zooma
Eternal                                 Joy Division                Closer
Ephemeris                           Michael Manring        The book of flame (iTunes-plus)
Makes perfect sense to me Michael Manring        Soliloquoy (iTunes-plus)
Activity from the head of his Ward                         It Might Be Useful For Us To Know
 
Afterthoughts (it might be an advantage to skip this section)
 
I commented on some aspects of my personal review experience in part 1; for example the effect of tiredness and chatter. Another I discovered was a tendency after a lot of listening to one track to recall and replay it in my mind while I was listening. Particularly disturbing was a tendency to anticipate the next part in the music. Attentionally, this meant I was not fully attending to the music, and therefore to hearing what might “really” be happening. This was further reason to take a break or switch to a different track.
 
In fact, it’s impossible to be sure one is not “replaying” and therefore “directing ones’s own attention” as one listens. It’s an effect of learning. It’s hard to unlearn things. Try listening to a speaker in your native language as if it were a tongue you had never learned., i.e. try to hear it as you first did, a meaningless jumble of sounds.
 
A mitigating factor here is that this “self-direction” I am hypothesizing may be an advantage. Cognitively, our minds tend to reduce our mental workload by following “scripts” - expectations of what happens in what order, what actions we need to take, and so on. When something happens different from the script - someone acts or something happens different from expectation - it draws our full attention.
 
If piece of equipment B really does sound different from A, the best time to notice this is immediately following a long series of repeated listenings to A; and vice versa. Subjectively at least, this was a method that seemed to “work” for me.
 
(Btw, although I did some cognitive psychology to post-graduate level - mostly memory and language - this is most certainly not my field! I am happy to stand corrected on any of my comments above).
 
Another aspect which I gave thought to before the idea of doing a review ever came up is that even a short piece of music contains a lot of information. For me at least, it is far more information than I can assimilate. I suppose it is not dissimilar from assimilating every detail of a visual scene. I can (and did, with the piano sonata once or twice) follow along with the sheet music (a lot easier!), but this is a different form of information; it tells me nothing about differences in what I actually hear.
 
This gives music (and not just music) one of its most important qualities. It is possible to hear a familiar piece many times and yet hear something different each time.
 
However, this makes reviewing - for me anyway - a tricky process. There was a constant need to be skeptical. Ok, I heard this with DAC 2 which I didn’t hear with DAC 1. Was it really not there with DAC 1, or did I just not notice it?
 
Go back. Check. Ok, yes it is there in DAC 1 after all. But now I’ve just learned it was there, and now know to look for it. Unless DAC 1 is defective I certainly should hear it. So, is there perhaps something about the overall balance of DAC 2 that pushed this detail more up-front and into my attention, whereas DAC 1 left it in the background?
 
Obviously, I have no clear answer to this question, even though I assumed it to be at least partly true in writing some of this report!
 

great write up. had the EE and ordered the Bifrost.  only sold the EE for financial reasons, otherwise i would have kept it.

Cheers Caracara. That's a pity you had to sell the EE. OTOH, the Bifrost is really good. It's going to be interesting to listen to it paired with the Lyr...

Outstanding write-up AD. Concise and honest. Looking forward to the rest.

Very nice, thanks for posting this, and I'm looking forwart to part 2 
 
 
 

The notion of ‘blackground’ - of dead silence between notes - seems to appear most often in discussions of some (usually solid-state) amps. Yet this is an easy description to apply to the Bifrost. 
 
<snip>
 
Reportedly, the recently released MiniMax-Plus may be better, sounding more detailed and having better blackground.

Click to expand...

 
Hmm, I'm not sure I quite understand the part about having a black background (or "blackground"  ). If a DAC exhibits a non-black blackground, it is, in my opinion, really absolutely terribly designed.

@olor1n - cheers, means a lot from someone whose posts I enjoy very much 
 
@RazorJack - yes, you noticed I covered myself with this review is about how they sounded rather than what's really going on! 
 
Electrical engineering is well outside my area of knowledge or comfort, so you must take this as surmise. I think the warmth I noted - my perception is more prominence or (equivalently) longer decay times to sound in the lower mid to bass area - is masking what would otherwise be clean, clear separation of notes with the MiniMax. As I can't see how this would be a property of the DAC chip itself, I must suppose Alex Yeung did something with the analog stage to induce a more "organic", less "black" sound. If so, he may have decided to "turn this down" a little with the MiniMax Plus.
 
I must add the difference is subtle but noticeable, and somewhat material dependent. Whereas it stood out with the piano and cello, and the rock material I cited, with  Rodrigo e Gabriela's 'Hanuman' (iTunes Plus download - haven't been able to source CD yet), the effect was just detectable and probably only noticeable because I'd learned how to listen for it. I thought this track would be a good test case because there's lots of percussive content, 'slap' and so on. Honestly though I couldn't decide which was the better DAC with this track. It sounded terrific with either; in fact, the "novelty" or "first-change" effect applied strongly here. Every time I switched it sounded "better" with the new DAC. I gave up and called it a tie.

Ah I guess I get it now. If the designer indeed intended such a coloration, I suppose there are people who like it.
 
One thing I've learned during my time on head-fi is that I'm quite picky when it comes to blackgrounds/noise floors, which is why I'll probably forever be a solid-state guy (and vinyl just for fun and collecting). If the artist decides to keep an audible background hiss on the final recording that's fine with me, but I want my gear to be dead silent when it's supposed to be.

Solid review. Critical and honest.  Much appreciated.  Will stay tuned for the rest.

@RazorJack, thanks for the link. I see what you mean.
 
@sridhar3 - thank you very much!

Arrived! Sorry it took me a while to check into your thread AiDee.
 
Superb review. I really enjoyed reading it it thrice before I clicked on "reply". Partly because there is such a wealth of information in the review, and because I had wanted to know you a little better I agree that the background of a reviewer makes a huge difference. The reason we pay obscene amounts of money to a medical specialist translates to why I value the detailed opinion of a technically inclined, serious music practitioner with a very keen ear more.
 
Although your review was inspired by the receipt of the much anticipated BiFrost, your opinion has caused me to choose the MiniMax, purely because the music which I frequently listen to (Dire Straits, Pink Floyd, female tenors) do better with details in the shadows. On top of that, I find my current set ups, 1) the RSA SR-71B+LCD2R2's and 2) Audiolab 8000A+Monitor Audio M2s a little too balanced so I am hoping that a darker source might add a little more warmth to my music.
 
Overall, thank you very much for the fantastic review!

@Blurpapa, thank you very much for your kind words. I'm very glad my review was useful 

Great work AiDee.
 
Interesting that the secondary harmonics or reverberations are more present with the Minimax even without the tube.  It should be a very close outcome with the tubeness added from the Lyr in stage 2 of the review.  Drum roll....  Will the added power and hybrid design of the Lyr be enough to capture the lead in bass impact and texture, whilst still maintaining mid and top end detail.....stay tuned.........
 
A point to people reading the review.  My thoughts are that the RCA tubes being used in the Lyr dont bring out as much bass texture as some others that I have.  Amperex Orange Globes for instance.  Most of the glowing reviews of the RCA seem to be from people with LCD2 whereas I use HE6.  Apart from another excuse to get some LCD2/3's this should be kept in mind that the response curve for peoples total rig needs to compliment.  ie a bit of added top end is good for LCD2 whereas as I HE6 owner I am looking for added bass texture.
 
Enough rambling from me.  Thanks again AiDee.  Looking forward to part two.

Thank you Kremer!
 
Good point about the tubes...I thought about which to use, and finally decided I should roll back to the stock GE6BZ7 as they're well thought of, were shipped with a reasonable number of Lyrs, and so might give a somewhat common reference point.
 
Nevertheless, a variable hard to control!
 
Thanks again 

Very nice write up. I'm trying to convince myself I need to order up a Bifrost in the next few months. I'm eagerly anticipating the Lyr portion.