[LoganRoss]

Lots of cool questions. We'll address them shortly, one by one. Stay tuned!

Thanks. Also, one more question:

12) Were the published specs recorded in tube, tube plus, or solid state mode? Assuming only one of the above, how the the specs change in the other modes?

 

[LoganRoss]

Hi IFI Audio,
I wanted to follow up on the questions below. Note that I have consolidated posts, thus there is now a question #12.  Thanks!
 
 
Quote:

  Hi IFI Audio,
 
I am about to order a pro and I have some questions (and perhaps some of these can be added to your support FAQ):
 
1) I noticed your specs seem to reference "short duration" peak power rather than continuous power. What is the actual normal use power rating? For 200ohm headphones?  Is it adapting (such as by impedance matching), based on the headphone connected?
 
2) Many higher end headphone amps have a lower output impedance, often 3, or even less than 1. The IC pro has a much higher one. what is the reason/benefit of this design? As a result, should only headphones of a specific ohm rating be used? How about for optimal performance?
 
3) The detailed specs do not discuss use of an output transformer.  Is this a unique design? it would great to understand the innovation. Is it something similar to the Chord Mojo's gain stage (conceptually)?
 
4) What is the impact of using a non balanced source? Do you still get the benefit of balanced output, or does half the circuit (including the corresponding power) go unused as is the case with some other amps?  Currently, my favorite DAC is the Chord Mojo.
 
5) Most other amps seem to require lots of power and use a giant desktop PC style power cord, perhaps to have a heavy enough gauge and shielding in order to avoid noise and interference. What is the technology that enables the pro to avoid these issues/requirements and use a small cord and wallwart (a great thing by the way)?
 
6) I noticed you spec JFets rather than the more commonly used Mosfets. What is the difference?
 
7) the description references that 3d sound and xbass are implemented in an analog manner. When these are switched off, are the related sections of the amp circuit physically bypassed, or is there some processing taking place all of the time?
 
8) Do you have frequency response charts? The lower registers are very important to me and I am curious as to performance in that area.
 
9) Your advertising materials highlight that ifi products leverage technology from the higher end AMR line of products. In the case of the ican pro amp, what are some of the technology that has trickled down?
 
10) Many amplifiers, including headphone amps, are really heavy. Presumably because parts, like transformers and heat sinks, are necessary for great sound. However, technology (and corresponding miniaturization) marches on. What technologies are responsible for your ability to keep the size and weight so low?
 
11) Do you consider the ifi ican pro to be in the same tier as the Audeze King?  In other words, what segment of the personal audio market is the pro directed to?  Performance is relative, and it would be interesting to understand against whom you benchmark.
 
12) Were the published specs based on tube, tube plus, or solid state mode? Assuming only one of these, how do the specs change for the other modes?
 
Really impressed so far with the potential of this product.  Thank you for your time and I look forward to your answers as well as actual listening tests.

 

[LoganRoss]

Here is a bump - hoping for IFI Audio to provide the promised responses to the previous questions

 

[iFi audio]

Here is a bump - hoping for IFI Audio to provide the promised responses to the previous questions

 
Cor blimey! Loads of questions...this is gonna eat into pub time….
 
 
 
Q#1A: I noticed your specs seem to reference 'short duration' peak power rather than continuous power. 
 
Music has a relatively high so-called ‘crest factor’ or ratio between peaks and average power, usually 10:1 – meaning for music mainly looking at the ‘peak power’ is somewhat relevant. Sine-waves as used for equipment objective testing have a peak to average ratio of 1.414:1, meaning they stress equipment greatly and may create overheating.
 
Comparison of Sinewave & Music Crest Factor
 

The iCAN Pro omits any protection circuitry that is directly connected to the audio path, as this often causes sonic degradation. To avoid a risk of blowing out the output stage in case of overload (which may occur with sinewave testing) we have integrated current limiting circuitry into the power supply.

This circuitry allows short term unrestricted peaks, but will progressively limit available current to protect the device based on temperature and clipping of the amplifier, all the way to an eventual complete shut-down of the iCAN Pro if overload is sustained, to avoid damage to either iCAN Pro or headphone.
 
 
 
Q#1B: What is the actual normal use power rating? For 200ohm headphones?  Is it adapting (such as by impedance matching), based on the headphone connected?

Power = Voltage X Current.
 
Voltage directly proportional to the input signal is what almost all amplifiers deliver (exceptions exist), current flowing is determined by the load.

Even if the amplifier is unconventional (e.g. current output types), the actual power is always dependent on the load (Headphone/Speaker) impedance. This applies to any amplifier of the ‘voltage output’ and ‘current output’ type.
 
In theory it would be possible to design an amplifier that delivers constant output power regardless of load impedance, but there is at this point in time no known headphone that would actually show any benefit from such a design.
 
Too low or too high load impedance both result in max output power allowed with that particular load lower than the absolute max capable by that amplifier.
 

 
For the iCAN Pro the power supply voltages to output stages limit the output voltage to 11.5V for single ended headphones and 23V for balanced headphones. The long term current limit for the iCAN Pro is around 1A peak per channel, which means with sinewave testing around 700mA is available, which in case of the balanced connection is shared between the signal phases.
 
Short term current can be much higher, the absolute maximum is certainly more than 7000mA for several milliseconds; it is not the easiest number to measure.

All this means the maximum long term sustained power with sinewaves with balanced connections will be 8,000mW into a 64 Ohm load and for single-ended connections it will be the same 8,000mW with a 16 ohm load for maximum power.

For short term peaks the main limitation is the length of the peak, we test with music that has relatively long, high level peaks at clipping to determine the equivalent sine-wave power.

For lower load impedances than those stated above the power will be limited by available current, for higher impedances it will be limited by available voltage. It should be noted that this behaviour is not unique to the iCAN Pro but applies actually to each and any amplifier under the sun.

Finally, if using 200 ohm headphones the power is limited by available voltage only (again, this happens with all amplifiers) so you would get around 660mW with a single-ended connection and around 2,640mW for balanced connection.

As most headphones tend to deliver > 100dB/mW SPL these power levels are insanely high, basically like driving a high-sensitivity horn speaker like AvantGarde with amplifiers having a kilowatt or more power!
 
If the 200 ohm headphone was 100dB/mW the single-ended connection would produce 128dB at full power and the balanced connection would produce 134dB at full power. These are extremely high SPLs and permanent hearing damage is a real danger at SPL levels this high.

Very few headphones will ever require even a small fraction of the power available from the iCAN Pro, having such large extra reserves allows it however to for example drive very inefficient headphones such as HiFiman HE-6 or AKG K-1000 with authority.
 
Carpe diem with these hungry headphones
 

 

[LoganRoss]

Dear IFI Audio,
 
All I can say is wow.  That is a wonderfully thoughtful response.  I now understand the dynamic between my headphones and my amp.  You have also provided information in a way that lets me cut through the marketing speak when trying to make an intelligent decision between two pieces of equipment.
 
As an aside, I am bummed I didn't get get picked to review the IFI Audio pro, but I did buy my own  As you continue answering the questions, I will incorporate what I learn into my assessment and provide you with feedback.  Actually having the Pro brings a new perspective on my questions, so I may edit them along the way.
 
So you are aware, I am experimenting with the Pro as a standalone headphone amplifier and as a pre-amp to my all tube amplifier.  Why would I do that?  Because even if I am using an alternative amp, I want to leverage the excellent lower xbass and 3D sound features, both of which I really appreciate already.
 
There's more to come from my end, so I thank you for making this an interactive thread!!!
 
LR

 

[GHoldridge]

So does the x-bass effect line outputs to say some speakers? I know the 3d does and they say for headphones/speakers, but seeing how the headphone amp part is different from the line out. I just wanted to make sure since I just grabbed a demo unit from music direct which I'm still waiting for.

 

[LoganRoss]

This is correct. See the IFI website for details.

 

[LoganRoss]

Dear IFI,
We are hoping you can provide answers to the other questions. Thanks in advance!

 

[iFi audio]

Q#2: Many higher end headphone amps have a lower output impedance, often 3, or even less than 1. The IC pro has a much higher one. what is the reason/benefit of this design? As a result, should only headphones of a specific ohm rating be used? How about for optimal performance?

The iCAN Pro has relatively low output impedance. So we're not sure where you get the impression the output impedance is high?
 
Unmatched impedances provide the best amplifier and speaker performance.
 

 
The precise value depends on the connection (balanced connection has double the impedance of single-ended and the 3.5mm connections include a network to match high sensitivity IEM's, but the maximum output impedance for any connection is around 4 ohms balanced or 2 ohms unbalanced.
 
 
 
Q#3B: The detailed specs do not discuss use of an output transformer. 
 
Output transformers are mainly used with tube amplifiers. They require great care in design and manufacturing to avoid adding distortion and frequency response limitations. Where they are essential, they must be used and designing good ones is no small task.
 
Impedance matching transformer matches 5000 Ω amplifier to 8 Ω speaker for maximum efficiency.
 

 
The Retro Stereo 50 Amplifier uses a full classic EL-84 tube amplifier and hence an output transformer is required. No off-the shelf item offered adequate performance, regardless of price, so we developed our own. In the end, we went through 20 prototypes before we had an output transformer that delivered the combination of objective measured performance we required and the quality of subjective performance listening to music we desired.

 

 

[LoganRoss]

Hello.  Thank you for your response.  A couple of follow-ups:
 
Q2:  I have read (I am no expert), that there is something called a damping factor for impedance matching of amplifier to transducer, and that typically you want the impedance of your transducer to be at least 8x the impedance of the amplifier.  For the Ican Pro, the only spec previously available to me shows an impedance of 16ohm for both single ended and balanced.  Is this an error on the iFI product page, as this may be where my confusion was.  If the output impedance was 16 ohms and you want at least an 8x damping factor, then a match with headphones having a much lower impedance than my 200ohm LCD-4s would not have been an ideal match.  Again, I am asking because I am new to this, and you have corrected my assumption regarding output impedance, so thank you.  

 
 
Q3: Thank you.  This is very helpful.  In fact, my other amp is a Woo Audio.  The biggest issue I have with the Woo is the frequency response dip below 50hz or so.  I do have a question: I notice other solid state amplifier manufacturers bragging about having big over-sized transformers.  Based on your comments above, it sounds like perhaps the transformers they speak of are not "output" transformers?
 
Retro:  The Retro looks really cool.  I will research it.
 
 
LR

 

[LoganRoss]

iFI iCan Pro evaluation update.
 
Hi.  This is not intended to be a review, but just some random thoughts after 6 days with the Pro.  It is an impressive piece of equipment.  The reason I say this is because of the functions it performs: 1) headphone amp; 2) pre-amp; and 3) bass and spatial enhancer.
 
I am going to work backwards:
 
XBASS AND 3D SPATIAL ENHANCER:  Simply put, a lot of music is made more fatiguing by the single ear (left or right only) effect.  I find that the 3D technology does an exceptional job of alleviating this fatigue and does so without making itself obvious.  The Bass enhancement, especially at the 10hz setting, can do a really good job of bumping up bass to make the music feel a little more speaker like.  Of course, this is only for some genres, as for others, it is not necessary.  I do wish xbass  settings were slightly more granular. Rather than a 9+ db bump, increments of 5 might have been more desirable.  
 
PRE-AMP (Edited on 10/22/16 - 8:45am PT):  This is tied to "Bass and Spatial Enhancer".  I have an all tube HP amplifier.  At times, I find that those two features (in pre-amp mode), coupled with the separate tube amplifier, give me another option for creating the sound I want. I did just realize that the HP and line outs use slightly different 3D circuits. Thus, using a separate amp for headphones may not be ideal if you are also going to use the 3D spatial enhancer.
 
HP AMPLIFIER (Edited on 10/22/16 - 8:45am PT):  I am finding my experience to be quite interesting.  Its more of a question of me adapting to a slightly different sound signature. I generally find SS HP amplifiers to be to harsh and fatiguing when using headphones.  For some genres like old school hip hop, I can get by due to their match with certain qualities SS excels at.  But generally speaking, I prefer to lop off any top-end harshness. You are probably saying, "no problem since the Pro has both tube and tube+ mode".  I agree, but I am still experimenting with those modes, and the amp still needs "break in" time.  For one thing, I am still getting used to the Pro, and that causes me to always want to compare it against my other amp, a Woo Audio.  For example, I really like the dimensionality of the Woo.  Specifically, if you consider the re-creation of a recording in three dimensions (up-down; left-right; and front-back), I find that the Woo amp excels in all three.  The Pro excels in left-right and up-down, but less so in front-back.  In addition, when comparing tube modes of the two amplifiers, as of now, there is heft and texture on the Woo that isn't always as present on the Pro. It adds some realism (i.e., it seeming less like a recording, and more like a live performance).  That said, the more time I spend with the Pro, the more its sound signature grows on me.
 
PRELIMINARY OBSERVATIONS (Newly added on 10/22/16 - 8:45am PT): What I am finding, including after a long listening session last night, is that you can't spend all your time doing A/B comparisons because each amplifier brings its own strengths to the table.   There is no question that the pro is an extreme quality amplifier.  Even after only one week of listening, its obvious that it excels in terms of potency, clarity, and detail.  I am also beginning to understand the power of being able to tune the sound, not just to a singular taste, but more importantly, based on the recording. No two recordings are alike.  No two genres are identical.  In either case, there are a ton of variables. The key of the Pro, is the ability to adapt to them. I make no final conclusions here, just some preliminary observations, which of course, are particular to my specific preferences 

 

 

[iFi audio]

 
Q2:  I have read (I am no expert), that there is something called a damping factor for impedance matching of amplifier to transducer, and that typically you want the impedance of your transducer to be at least 8x the impedance of the amplifier.  For the Ican Pro, the only spec previously available to me shows an impedance of 16ohm for both single ended and balanced.  Is this an error on the iFI product page, as this may be where my confusion was.  If the output impedance was 16 ohms and you want at least an 8x damping factor, then a match with headphones having a much lower impedance than my 200ohm LCD-4s would not have been an ideal match.  Again, I am asking because I am new to this, and you have corrected my assumption regarding output impedance, so thank you.  

 
 

This specification is NOT the output impedance but the lowest recommended headphone Impedance. We do not specifically list any impedance as between single-ended and balanced outputs both iEMatched on 3.5mm jacks and direct on 6.3mm & balanced jacks there are many actual numbers.
 

   I do have a question: I notice other solid state amplifier manufacturers bragging about having big over-sized transformers.  Based on your comments above, it sounds like perhaps the transformers they speak of are not "output" transformers?

No, they usually talk of their mains/power transformers. Output transformers are extremely rare in solid state gear.
 
Incidentally, the power-supplies in iFi gear operate using high frequencies, for the pro line it is 1.2MHz, or 10,000 times faster than 120Hz mains. This also means that capacitors, transformers and filter chokes can be 1/10,000 the size/value one would need for 120Hz mains powered systems. 
 
Given that our parts are not 1/10,000 the size/value but closer to 1:100, one might say that our power supply components are generally oversized by a factor of around 100 over common "best practice"

 

[LoganRoss]

Thanks for the clarifications. Regarding the impedance question, I now understand. It might be helpful to clarify this on your website spec sheet. Regarding output transformers, I also now understand and thank you for your patience in explaining this.  
 
Regarding power, I think you are saying that using more sophisticated power components, such as higher frequency, enables you to reduce physical size? I forget whether my original set of 12 questions included one on power, but any thoughts you have on the benefits of the pro line power configuration would be welcome.
 
As an FYI, I have amended my preliminary observations after a long and studious listening session last evening.

 

[iFi audio]

  Thanks for the clarifications. Regarding the impedance question, I now understand. It might be helpful to clarify this on your website spec sheet. Regarding output transformers, I also now understand and thank you for your patience in explaining this.  
 
Regarding power, I think you are saying that using more sophisticated power components, such as higher frequency, enables you to reduce physical size? I forget whether my original set of 12 questions included one on power, but any thoughts you have on the benefits of the pro line power configuration would be welcome.
 
As an FYI, I have amended my preliminary observations after a long and studious listening session last evening.

Not a problem. For now, let's stick to your original questions (in order to avoid mess) and once we're done with these, please do get back with any other that will afloat along the road. Perhaps we'll be able to address those as well, who knows

 

 

[LoganRoss]

Dear iFi,
Can you clarify the frequency of answers you will provide to the original 12 questions? We are hoping it will not be 1 per week ☺ But also, thank you for the amazing effort put into the answers.