[ufospls2]

Hey guys,
 
I've read the posts on the first page about double amping etc. but I'm still a bit confused. My options are the Woo Audio WA8 OR a Chord Mojo with the ALO Audio Continental V5, or the Chord Mojo on its own. Im really interested in a tube amp, as my desktop set up is solid state, so a change would be nice. I know the Mojo can be set to line level, so does that avoid the problems with "double amping" if I was to use it as an input into a Continental V5? Or should I just go for the Woo Audio WA8 and avoid the problem all together, as well as stacking problems? 

 

[jarnopp]

Hey guys,

I've read the posts on the first page about double amping etc. but I'm still a bit confused. My options are the Woo Audio WA8 OR a Chord Mojo with the ALO Audio Continental V5, or the Chord Mojo on its own. Im really interested in a tube amp, as my desktop set up is solid state, so a change would be nice. I know the Mojo can be set to line level, so does that avoid the problems with "double amping" if I was to use it as an input into a Continental V5? Or should I just go for the Woo Audio WA8 and avoid the problem all together, as well as stacking problems? 

I think you have far more options than those to stack a portable DAC/amp, but if you have listened to those combos, I would go with the sound you prefer. Also, it depends on how you will use it. The WA8 looks cool, but only 4 hours battery life. Both the WA8 are dac/amp devices so you don't need an additional amp unless your headphones require it or you like the sound combo better. The ALO does need a dac, but not necessarily either of the two you mention.

Finally, thE Mojo itself is probably more powerful than either of the other amps, and if you prefer e sound of the Mojo into either, you probably will not want "line out" which simply sets the output to 3v. You likely will want something lower, like 2v or less, which you can get by lowering the volume 3-4 clicks on the Mojo.

My advice would be to have an extended audition with the WA8 and Mojo side by side with your preferred headphones and go with the sound you like best. You can always add more power later if you need it.

 

[x RELIC x]

Hey guys,

I've read the posts on the first page about double amping etc. but I'm still a bit confused. My options are the Woo Audio WA8 OR a Chord Mojo with the ALO Audio Continental V5, or the Chord Mojo on its own. Im really interested in a tube amp, as my desktop set up is solid state, so a change would be nice. I know the Mojo can be set to line level, so does that avoid the problems with "double amping" if I was to use it as an input into a Continental V5? Or should I just go for the Woo Audio WA8 and avoid the problem all together, as well as stacking problems? 

Basically, when talking about transparency to the original music, the WA8 will add more (tube) distortions to the music than the Mojo (I'm not saying in any way the WA8 won't sound good). The Mojo's analogue output stage is exceedingly clean, with very low distortion that's better than most desktop DACs line out. The line out 'mode' in the Mojo is nothing more than a shortcut on the volume to 3V, nothing is bypassed (four clicks down from there is 1.9V). The capabilities of the DAC means that Rob Watts doesn't need three different opamps to help the noise in the output plus a headphone amp like 'conventional' DAC/amps.

Basically you can think of the Mojo (and Hugo, Hugo TT, and DAVE) as a full time variable line out from the DAC and not worry about double amping distortions as the Mojo's output is clean and stable through the volume range. So the benefit to the user is a very good DAC with a very transparent line-out / headphone out combo as a bonus. Treat it like that and go from there. Use on its own, or add an external amp to your preference. Chord DACs really are different from other 'conventional' DACs so some mental adjustment to understanding the tech inside is not unusual.

From the third post of this thread:

Spoiler: Regarding Mojo's output

Quote:
Originally Posted by Rob Watts View Post

Quote:
Originally Posted by AndrewH13 View Post


Just a thought. Why do other DAC/headphone amps have amp sections when Hugo/Mojo get by without one, and many including Chord say it is more transparent? Have Chord got the patent for ampless amps

Because they can't using chip based DAC's. Chip DAC's have two current outputs. So you need two I to V converters (amps) then a differential to single ended amp, then a headphone buffer to deliver the current. You also need a lot of analogue filtering wrapped around these amps. So why are normal DAC's so complex in the analogue domain? Two reasons:

1. Silicon DAC's are horribly noisy, as the substrate and grounds are bouncing around due to switching activity. So to counter this, it is done differentially, which means the ground noise is cancelled. It also hides the problems of the reference circuitry, which can't be made with low enough impedance on silicon. This translates to more distortion, and crucially noise floor modulation.

2. Delta sigma converters run at low rates - best is at 12 MHz - this means that there is a lot of noise that must be aggressively filtered out in the analogue section. This also applies with R2R DAC's too as these have even worse problems due to the very slow switching speed.

So to run with a single amp section you need the DAC to be single ended and to run the noise shapers at much higher rates to reduce your filtering requirements. Because the analogue section with Mojo is discrete, I can use extremely low impedance and low noise reference supplies - something that is impossible on silicon. This has the other benefit of eliminating noise floor modulation (actually there is a lot more to it than this as there are countless other sources of noise floor modulation in a DAC). To make the filtering easier, the pulse array noise shapers run at 104MHz - over an order of magnitude faster than normal. There are other benefits to running the noise shapers at 104MHz, principally the resolving power of the noise shaper. Now soundstage depth is determined by how accurately small signals are reproduced. The problem with noise shaping is that small signals get lost - any signal below the noise shaper noise floor is lost information. But by running the noise shaper at much faster rates you solve this problem too - indeed Mojo noise shapers exceed 200dB THD and noise digital performance - that's a thousand times more resolving power than high end DAC's.

If I get time today I hope to publish noise floor modulation measurements showing Mojo has zero measured noise floor modulation. This level of performance does not happen on any other non pulse array DAC's at any price, and its the primary reason why Mojo sounds so smooth and musical.

Rob

This quote is from the Hugo thread but also applies to the Mojo (bold emphasis added by me):

Spoiler: From Hugo the thread

Originally Posted by Rob Watts View Post

I have been seeing some comments describing Hugo as excellent DAC with a good headphone amp. Both comments, in my view, are wrong and way off the mark - and seeing these comments are starting to bug me, so I would like to get it off my chest. So forgive me if I am overstepping the mark - commenting on honest posts about a product I have designed, but I thought it might be useful for Head-fi'rs to read my views.

First, I would like to talk about what as a designer I am trying to accomplish, as it has a bearing on one's opinion of Hugo's sound. Imagine going around CES and carefully listening to all the high end hi-fi on show, so you can carefully listen to all the major high end brands available today. Next, listen center stage row 10 to an orchestra. Now, in my opinion, high end Hi-fi sounds from very bad to absolutely awful compared to live acoustic music. The key difference in the sound is variability - live acoustic music has unbelievable variations in the perception of space, timbre, dynamics and rhythm. Additionally, each instrument sounds separate and as distinct entities. By comparison, high-end audio is severely compressed - depth of sound stage is limited to a few feet (listen to off stage effects in say Mahler first - in a concert the off stage effects sound a couple of hundred feet away but on a hi-fi it is an ambient sound a few feet away). Timbre is compressed - you don't get a really rich and smooth instrument playing at the same time as something bright. The biggest problem is the dominance effect - the loudest instrument is the one that drags your attention away - this constant see-saw of attention is the biggest reason for listening fatigue, a major problem with Hi-fi.

So I am approaching designing of Hi-fi from the POV of accepting that there are enormous differences between conventional Hi-Fi and real music, and that I want my equipment to be as transparent as possible. Now some peoples idea of transparency is to use distortion to artificially enhance the sound, and this is a real problem with listening tests - a superficially brighter sound, giving the impression of better detail resolution, is often distortion. So a real challenge is defining what true transparency is. My definition, is to latch onto the idea of variations - if a modification makes the sound more variable, then its more expressive, and hence more transparent, even if it sounds, in tonal balance, darker or smoother and superficially less impressive. Now, if you think that your Hi-Fi sounds better than live acoustic music - then fine, we will agree to disagree. You are looking for a sculpted sound, not a truly transparent one, and I would strongly advise never to buy equipment designed by myself, as I am striving for equipment with no added sound.

So how does this relate to Hugo? Hugo was on the tail end of a long series of incremental improvements in digital design. I have spent the last 7 years on R and D to fundamentally improve aspects of DAC performance - improvements in the jitter rejection, RF noise filtering, noise shaper topologies, WTA filter length, analogue design plus a lot of other things. Moreover, Hugo took advantage of a big step forward in the capabilities of FPGA's - I could do important things that I knew influenced the sound but that previously were not possible due to FPGA limitations. So Hugo was at the confluence of two events - a big step forward from 7 years work in understanding digital design plus a major step forward in FPGA capability. It is just an accident that it happened with a portable headphone product.

So Hugo was the first instance when all these improvements came together. When I finally heard the pre-production unit with all the improvements in place I could not believe the sound quality improvements that I first heard. It completely changed my expectations of what was possible from digital audio - I was hearing things that I have never heard from Hi-fi ever - in other words, the gap from Hi-fi to live acoustic music was suddenly very much closer. Most notable was rapid rhythms being reproduced with breathtaking clarity - before piano music sounded like a jumble of notes, now I could hear each key being played distinctly. The next major change was timbre variations - suddenly each instrument had their own distinct timbre qualities, and the loudest instrument dominance effect was gone. Also gone was listening fatigue - I can listen for 12 hours quite happily.

But by far the biggest change was not sound quality, but on the musicality. I found myself listening and enjoying much more music, in a way I have never experienced before with a new design (and anybody who knows something of my designing career knows that is a lot of designs).

So my conclusion is this: Hugo does things that no other DAC at any price point does. Now I can say readers saying, well OK he would say that anyway, it's his baby. True - I can't argue with that POV. But let's examine the facts:

1. The interpolation filter is key to recreating the amplitude and timing of the original recording. We know the ear/brain can resolve 4uS of timing - that is 250 kHz sampling rate. To recreate the original timing and amplitude perfectly, you need infinite tap lengths FIR filters. That is a mathematical certainty. Hugo has the largest tap length by far of any other production DAC available at any price.

2. RF noise has a major influence in sound quality, and digital DAC's create a lot of noise. Hugo has the most efficient digital filtering of any other production DAC - it filters with a 3 stage filter at 2048 FS. The noise shapers run at 104 MHz, some 20 times faster than all other DAC's (excepting my previous designs). What does this mean? RF noise at 1 MHz is 1000 times lower than all other DAC's, so noise floor modulation effects are dramatically reduced, giving a much smoother and more natural sound quality.

3. The lack of DAC RF OP noise means that the analogue section can be made radically simpler as the analogue filter requirements are smaller. Now in analogue terms, making it simpler, with everything else being constant, gives more transparency. You really can hear every solder joint, every passive component, and every active stage. Now Hugo has a single active stage - a very high performance op-amp with a discrete op-stage as a hybrid with a single global feedback path. This arrangement means that you have a single active stage, two resistors and two capacitors in the direct signal path - and that is it. Note: there is no headphone drive. Normal high performance DAC's have 3 op-amp stages, followed by a separate headphone amp. So to conclude - Hugo's analogue path is not a simple couple of op-amps chucked together, it is fundamentally simpler than all other headphone amp solutions.

This brings me on to my biggest annoyance - the claim that Hugo's amp is merely good. Firstly, no body can possibly know how good the headphone amp in Hugo is, because there is not a separate headphone stage as such - its integrated into the DAC function directly. You can't remove the sound of the headphone amp from the sound of the DAC, it's one and the same.

Struck by these reports, I decided to investigate, as I see reported problems as a way of improving things in the future. I want to find weakness, my desire is to improve. So I tried loading the OP whilst listening on line level (set to 3v RMS). With 300 ohm, you can hear absolutely no change in sound. Running with 33 ohm, you can hear a small degradation - its slightly brighter. This is consistent with THD going from 0.0004% to 0.0007%. Note these distortion figures are way smaller than desktop headphone amps. Also note that with real headphones at this level you would be at typically ear deafening 115dB SPL. Plugging in real headphones (at much lower levels) gives no change in sound quality too. This has been reported by other posters - adding multiple headphones to Hugo does not degrade sound at all.

So how do we reconcile reports that desktop headphone amps sound better? I don't believe they do, its a case of altering the sound to suit somebody's taste. Now as I said at the beginning of this post, that is not what I want to do - I want things to sound transparent, so that we can get closer to the sound of live acoustic music. Adding an extra headphone amp will only make things worse as extra components degrades transparency. Another possibility is that people are responding against Hugo's unusually (for a headphone amp) low output impedance of 0.075 ohms. Now, compared to headphone amps of 2 to 33 ohms impedance, this will make the sound much leaner with less bass. Additionally, the improvements in damping can be heard as a much tighter bass with a faster tempo. So if you find your headphone too lean, the problem is not Hugo's drive - your headphone is just been driven correctly.

Just to close to all Hugo owners - enjoy! I hope you get as much fun from your music as I have done with Hugo.

 

[ufospls2]

I think you have far more options than those to stack a portable DAC/amp, but if you have listened to those combos, I would go with the sound you prefer. Also, it depends on how you will use it. The WA8 looks cool, but only 4 hours battery life. Both the WA8 are dac/amp devices so you don't need an additional amp unless your headphones require it or you like the sound combo better. The ALO does need a dac, but not necessarily either of the two you mention.

Finally, thE Mojo itself is probably more powerful than either of the other amps, and if you prefer e sound of the Mojo into either, you probably will not want "line out" which simply sets the output to 3v. You likely will want something lower, like 2v or less, which you can get by lowering the volume 3-4 clicks on the Mojo.

My advice would be to have an extended audition with the WA8 and Mojo side by side with your preferred headphones and go with the sound you like best. You can always add more power later if you need it.

 
 

 

 
 
 
Thanks you both for the detailed and helpful replies. I'll just need to audition both and continue to think. 

 

[commingled]

Fancy Mojo case.  Pretty expensive though.
 
http://audiovideo.com.pl/akcesoria/5311-futeral-chord-mojo-case.html
 
edit: I didn't know about the Moon Audio case, but it seems to be sourced elsewhere, otherwise it would be more expensive in Europe.  At the time of this post, 379 Polish zloty = 95.38 U.S. dollars, so folks in the EU are better off buying it from here.

 

[theveterans]

Some desktop amps don't use multiple op amps, but a discrete analog output

 

[EagleWings]

  Fancy Mojo case.  Pretty expensive though.
 
http://audiovideo.com.pl/akcesoria/5311-futeral-chord-mojo-case.html
 
edit: I didn't know about the Moon Audio case, but it seems to be sourced elsewhere, otherwise it would be more expensive in Europe.  At the time of this post, 379 Polish zloty = 95.38 U.S. dollars, so folks in the EU are better off buying it from here.

 
The maker of this case is Chord themselves. Moon-Audio is just the retailer. It retails in US for $100.

 

[michaelgordon]

i have a couple of questions about cables.
 
From a few posts back someone mentioned they had ordered a silver OTG cable from penonaudio.  Does anyone know if this may help with interference ferite chokes didnt and tried multiple cheap cables. its this one http://penonaudio.com/OTG-Pure-Silver-Cable
 
If not im currently using a Fiio L17 to connect my Cayin N6 to the mojo would this http://penonaudio.com/3.5mm-Male-to-3.5mm-Male-Pure-Silver-Cable be any better or would getting a proper coax make any difference?
 
and lastly if i were to get an Astell & Kern dap are there any alternatives to the moon audio / sysconcepts optical cable as they are quite expensive and shipping to the UK is also very expensive.

 

[Mython]

   
.... someone mentioned they had ordered a silver OTG cable from penonaudio.  Does anyone know if this may help with interference ferite chokes didnt and tried multiple cheap cables. its this one http://penonaudio.com/OTG-Pure-Silver-Cable

 
No, that cable won't improve on any RF issues you might be experiencing, as it isn't shielded in any way, and silver certainly isn't immune to RF. That's not to say it isn't a good cable; just that it won't improve any RF issues one might be experiencing.
 
Proper Co-Axially shielded cable will provide a degree of RF protection, and is definitely worth trying, but no method is 100% immune to RF. Some people's phones kick out more problematic levels (and sometimes more problematic frequencies) than others, depending on the unique conditions within which the phone is operating, which is why some people find they have to use airplane mode when they hook-up Mojo with their phone. Whilst it is tempting to blame Mojo, RF issues are absolutely not unique to Mojo, at all.
 
 
Having said all that, I'm not clear on the exact circumstances within which you are personally experiencing RF issues - are you saying you are having RF issues when using a Cayin N6 DAP?
 
 
Quote:

   
and lastly if i were to get an Astell & Kern dap are there any alternatives to the moon audio / sysconcepts optical cable as they are quite expensive and shipping to the UK is also very expensive.

 
 
Sorry, I'm distracted with other things, this evening, so I'm rushing to answer this, hence the earlier oversights in my response - the short answer is 'No' - there are no very-neat equivalent optical cables (AFAIK) at a substantially cheaper price - Alo do a short one:
 
http://www.aloaudio.com/portable-optical
 
....but the terminations are inappropriate, so adapters would be necessary, and that's an extremely bad idea with optical.
 
 
.

 

[michaelgordon]

Thanks.  I was having interference form screen use when using phone, with screen off it was better but still not perfect it didnt sound like RF more like clicking & popping..  
 
Im not getting anything with the Cayin, sound is great just wondering if a proper coax cable or the silver would improve things at all as i keep seeing posts about the fiio coax cable being well received.
 
I had a look at post 3 but couldnt see any optical cable recommendations so thought i would ask just in case before i buy the DAP as it will add another £70 onto the cost of the AK to probably not get much better than the Cayin N6.  In an ideal situation id get rid of the interference and be able to use the phone but have given up on that idea now.

 

[Mython]

Yeah, apologies - it's been a while since I updated the info in the optical connections section of post #3, and after I posted my reply, I checked-back and yeah.... I remember, now, that there simply aren't many ultra-short optical cables (with suitable terminations for AK -> Mojo usage) available at the moment. I thus updated my original reply.
 
I have to run, now, so sorry I couldn't give you the happy answer you were hoping for

 

[Peter Hyatt]

   
The maker of this case is Chord themselves. Moon-Audio is just the retailer. It retails in US for $100.

I've pre ordered from Moon Audio.  I purchased the Mojo from them, and then the AK T8 ie.   
 
The Mojo's value to me exceeds the cost and is well worth protecting with a well made leather case, as I take it with me always.  I think shipping is set for early June!  

 

[EagleWings]

Loving the A10 and Mojo combo. Both work in tandem, in bringing out the best in each other. 95% of my music files are 256 or 320 MP3. I was planning on upgrading my library from MP3 to 16/44 FLAC, but the thought of it was scary. Mojo seems to do so well with even the MP3s, that I am not sure if I want to go down the route of upgrading to FLACs. Or even if I want to, I can take my time.
 

 

[EagleWings]

 
I've pre ordered from Moon Audio.  I purchased the Mojo from them, and then the AK T8 ie.   
 
The Mojo's value to me exceeds the cost and is well worth protecting with a well made leather case, as I take it with me always.  I think shipping is set for early June!  

 
+1 on the bolded part. I am really hoping, it would ship sooner.

 

[brent75]

Little buddy showed up just now. Man, this thing has got some heft to it. Commence the 10-hour initial charge!