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REVIEW OF PENGUINAMP CAFFEINE WITH BASS BOOST, with additional COMPARISON WITH PENGUINAMP ROYAL AND J. SEABER CMOY BASS BOOST. PLUS, DETAILS ON THE COMMERCIAL VERSION OF THE CAFFEINE PRO, CALLED HEADSTAGE LYRIX, which come in three versions.
A detailed review of the J. Seaber CMoy bass boost and Penguin Royal should be viewed at http://www.head-fi.org/forums/showthread.php?t=258868 first, including updates added around the middle of September 2007 as the Royal passed the Tomahawk for bass and soundstage. Also, my review of the iBasso D1, comparing that to the Royal and Tomahawk is here http://www.head-fi.org/forums/showpo...postcount=1054
ADDITIONAL NOTES: I MADE AN INQUIRY. THE OPAMPS IN THE CAFFEINE ARE NOT SOCKETED, SO NO ROLLING. THE OPAMPS ON THE HEADSTAGE LYRIX COMMERCIAL VERSION BOUGHT ON EBAY ARE ONLY SOCKETED IF REQUESTED AT THE TIME OF ORDER FOR AN EXTRA $20, CALLED THE "TOTAL" UPGRADE.
PROCEDURE: The PenguinAmp Caffeine and J. Seaber CMoy bass boost were both run with music for approximately 150 hours prior to this review. The PenginAmp Royal has over 350 hours on it now. The Caffeine needed some burn-in for grainy or harsh sound through my ER6i, and it transformed at about 70 hours, loosing the grainy-ness and opening up/widening up. If I recall correctly, the J. Seaber CMoy bass boost with similar sound issues took 24-48 hours to transform, while the Royal sounded great right out of the box and just got better and better. The Royal transformed between 150-250 hours, and grew some balls in the bass while becoming even more transparent than before.
This review will focus mostly on the newest addition, the Caffeine. All three amps were tried with the Livewires first, and all music selections were played on all amps. Then this was repeated with the ER6i and then the HD600's. Testing was done when all three amps had been tried with all three headphones, and all music selections had been played. To get the best sound, a dock line out was used, but it was impossible to listen to the Seaber CMoy with dock-line out and a volume attenuator - the line out simply had too much signal gain and it overdrives the Seaber's input into distortion. So, all three were also listened to with headphone out. Except where headphone out is mentioned, assume the dock line out was used.
SOURCE: 30gb and 80gb iPod video, used only with 320kbps VBR and higher, including apple lossless.
CABLES: Custom made 3.5mm to 3.5mm interconnect, Send Station Dock Line Out, Shure volume attenuator (my cryodock wasn't available for this test).
HEADPHONES: Etymotic ER6i, Livewires customs, Sennheiser HD600. (I listened briefly with my Shure E500 and Ultrasone HFI700 to confirm what bass boost does with phones with good bass, but there is no need to run bass boost with these phones).
PROGRAM MATERIAL: Arne Domnerus "Jazz at the Pawnshop", The Tord Gustavsen Trio "Being There", The Rippingtons "20th Anniversary", Jesse Cook "Montreal (Live)", Diana Krall "Live in Paris", Lord of the Rings "Return of the King" soundtrack, Sir Collin Davis London Symphony "Sibelius: Kullervo", Pixies "Mass of Destruction", Good Charlotte "Good Morning Revival", Pink "I'm Not Dead Yet", Ani Di Franco "Knuckle Down", Jack Johnson "In Between Dreams".
AMP FEATURES, customer support and Price: Best bang for the buck Winner = Caffeine: Robert Gehrke at PenguinAmp is very responsive to emails, but his day/night hours are different because he is located in Germany. The "Caffeine" model has recently been revamped to two models - an economical $49 model and the bass boost with gain for $69. It now features an AD8397 opamp like the Royal, volume control plus a hi-low gain switch, bass boost on/off switch, a 9v-18v charging circuit for 9v battery, and production-line quality build but in a mint-tin case. The charging jack is located inside the amp, to minimize the chance of pocket fuzz getting insie the hole. Retail is $69. This amp was a free review unit, but I will offer to buy it after the review.
The Royal also uses the AD8397, has dual rail-splitters for more current, adds larger nichicon capacitors like the Hornet non-M, but lacks the gain and bass boost switches (neither of which is needed as you'll see). It too has a charging circuit, but unlike the Caffeine, it also allows the un-amplified sound to pass-through when the amplifier is off (limited usefulness with dock line out). I paid $89 new on ebay, retail is $99.
John Seaber is also very responsive to emails, and has been willing to add customized features to his amps. On this forum his user name is "Blackinches". My J. Seaber CMoy bass boost v1.48 lacks a volume control, and is designed to run from the headphone out of your source. It does have a bass boost switch between the input and headphone out where the PenguinAmps place a volume control. It has an optional hi-low gain switch hidden inside, but when not made custom the switch woudl go through a hole in the side of the tin. It lacks a power on switch, but turns on when you plug in the source to the input jack. It can be powered by a 9v - 24v "regulated" power supply, which when plugged in will disconnect the battery. There is no charging circuit. I use just the plug-tip from a universal power supply to plug the power-jack, and this also serves as a power off switch so I don't have to disconnect the source to turn it off. Price was $45 with the options, and a volume knob was a $10 option but was out of stock at the time. Note, a new model with volume control as part of the new circuit board, and no gain switch will be available in about 2 weeks.
BUILD quality: Winner = Caffeine ties Royal just because I love big caps vs cool power connectors with integrated boost and gain switches. All amps have a nice professionally made circuit board. The PenguinAmp Caffeine and Royal have a cleaner look with the circuit board inverted so no components are seen (offering more protection from damage), while the Seaber circuit board has all the components visible in all their glory. The extra wires in my photo are from the optional gain switch - I begged to have it hidden inside the case to make the amp slimmer. The Caffeine has a quite unusual connection for the 9v battery, being incorporated into the circuit board instead of dangling off by a wire. The battery is held in place quite securely. The build quality of the Penguin Amps is something you'd expect to find being sold in a Hammond aluminum case for 2-3x the retail price. At least the Caffeine comes in a neat HoloGraphic Penguin mint tin, which is pretty under track lights.
MAX VOLUME, HISS AND GAIN: Winner = Caffeine ties Royal again : The amp is powerful and drives my Sennheiser HD600 fine on high gain, as does the Royal. The Seaber high gain was set up for HD280 pros, and doesn't go as loud with HD600 as the Caffeine before distortion. With the Caffeine on low gain, connected to a paused iPod via headphone jack, with iPod volume at anything above zero, the Caffeine is very quiet. Starting at "zero" on the Caffeine volume knob (which is about 6 o'clock) rotating the volume clockwise to about 12 noon it remains silent, even with the Livewires. In using this amp, I found no reason to ever go past 12 noon on the volume dial with high efficiency IEMs like the Livewires - past that it will just be too loud for comfort.
There is a slight hiss beginning between 12 noon and 1 o'clock. But the music will always be well above the level of background hiss. By 4 o'clock the Caffeine's volume knob is at max, and hiss is very noticable. Unplug the iPod, with amp on and headphones connected, and the hiss is VERY quiet. The S/N ratio seems quite good in the usable range of the volume knob (6 o'clock - 1 o'clock), and hiss is never audible above the program material, even in very quiet passages with loud volumes in dynamic passages.
On low gain, the hiss with the Seaber Bass Boost is considerable with the Livewires - since there is no volume knob, a volume attenuator is a must. With the Shure volume attenuator, just rolling the attenuator's knob by 4mm will knock out a fair amount of hiss, and most of hiss is gone by 6-8mm (and volume levels are similar to that of the Caffeine with volume knob set at 12 noon). With no attenuator and both amps set to low gain, and the Caffeine volume set at max (Seaber is already at max), the music volume levels on the Caffeine are similar to the Seaber, and they both become intolerably loud at 50% of iPod volume or more - but, the Caffeine has maybe 2-3 db less hiss between songs. (Again, there is no reason to go past 12 noon on the volume knob to get quite loud, and hiss is inaudible at that setting.)
BASS: Winner = Caffeine, Royal a close second: The Caffeine with Bass boost switch off strikes me as clean, quick, controlled and flat - i.e it is decidedly flat/neutral, without the punch of the 350 hour burned-in Royal. With the bass boost switch on it was still a very natural sounding bass with just more bass present - this puts the Royal's bass between the Caffeine with boost off and the Caffeine with boost on. Bass boost is not muddy, seems to boost the 8-9db that is claimed, feels boosted mostly below 120-150hz (I didn't ask) and works well with a wide variety of headphones and music. It just doesn't sound like someone turned on EQ, but rather it sounds like the music was meant to have that amount of bass.
The J. Seaber bass boost is maybe an additional 3db more pronounced, and the boost seems to begin at a little higher frequency at maybe 180-220hz. It is great with some music, but not with all music, unlike the Caffeine. I say this in the sense that the Seaber bass boost can overpower some earphones and material, and sounds somehwat unlike it should at times. Case in point, The Rippingtons. The Rippingtons benefit from the Caffeine's bass boost but they sounded a little overboosted with the Seaber. Same with Tord Gustavsen Trio - with the Seaber bass boost turned on, the string bass at 50% volume overdrives the Livewires, is distorting and showing some extra harmonics. The Caffeine bass boost seems to suck less current so the max clean sound levels achievable with the Caffeine seem like they are 2-3db higher when both have bass boost turned on.
The Royal has no bass boost but it sounds like it carries more weight in the bass in loud passages, I will call it "mass". Even if the volume of bass is greater with the Caffeine and Seaber with boost, the Royal is like Bam Bam Bam! vs Thump Thump Thump. Royal has two large nichicon caps like the Hornet non-M, and twin ground rail splitters for more current capability. But at volumes normal people listen at, the Caffeine is the most versatile in the bass.
MIDS: Winner = Royal by a hair: Mids from the Caffeine are full and forward, vocals sound true and present. I notice no sucked-out mids to simulate a wider sound stage like some amps or headphones. I had no issues or complaints with any of the amps mids, and all three amps made listening to my ER6i enjoyable by removing the harsh upper mids, especially with pianos. The Royal had the best mids, almost described as lush, or "solid" would be another word - instruments and voices have substance, they're almost tactile. With the Royal and the Caffeine, the pianos saxophones and clarinets sounded closer to being there than when listening to the headphones plugged directly into the iPod.
TREBLE: Caffeine ties Royal: The caffeine's highs are sparkly and clear. The Seaber is close, but a just a smidge weaker. The edge to violins is all there in the Penguin, but at 95% in the Seaber. The sound is not overly bright, or sibilant, and is very similar to the Royal.
SOUNDSTAGE: Caffeine ties Royal: The soundstage is open, reflecting the venue where the recording was made. After 150 hours burn-in, the soundstage is more open and less compressed than music right out of the headphone jack or from the J. Seaber amp. Interestingly, The Caffeine with Livewires made the headphone out actually sound good - it took the Royal 250-300 hours to achieve that. For a while I wondered if Robert, the designer, had snuck a cross-feed circuit or some other trickery into the amp, but the Royal has a similar wide open soundstage too. The Penguins rival my RSA Tomahawk, but, moving up a whole 'nother league, it is less wide than going through my iBasso D1 via optical input (not fair
).
SUMMARY: Winner = Caffeine by a hair over the Royal, far ahead of the Seaber: Certain headphones need MORE bass to sound just right, such as the ER6i Some produce plenty of bass but benefit from a little extra, like the Livewires and HD600. Some make great bass and any extra would simply be too much (Shure E500 and Ultrasone HFI7000). The Caffeine seems to get along with all these headphones. I keep pretending that the Caffeine turns my HD600's (with black dragon cables) into a not-so-dark HD650 with better treble.
With bass boost on, the Caffeine has less distortion at high volumes than the Seaber. The moderate level of bass boost and choice of frequencies boosted helps maintain a more natural sound. It also allows use with a wider variety of headphones, being less likely to over-drive them. The sound quality is excellent, out of line with its cost, and it can drive low-sensitivity high-impedance headphones as well as it drives high-sensitivity low-impedance earphones.
And any hiss with the low-impedance earphones at low volumes (aka Livewires) can be minimized by keeping the volume knob turned down to below maximum. Using the Dock-line out or headphone out, you will never have the volume turned up high enough (not past 1 o'clock) to make hiss an issue. The hiss is an issue with the Livewires not the amp, and my iBasso D1 behaves the same way as the Caffeine. The lack of volume control is an issue with the Seaber amp, but fortunately a volume attenuator can help the hiss, but this degrades the sound quality with some phones if too much attenuation (more veiled, less airy).
I've always been biased towards big caps, even when they aren't needed. It may be a placebo to me sometimes, but I really like the heft of the Royal with the big caps, and I wonder if it isn't just my imagination about the Royal's bass having more "mass" even though the bass volume is less than the caffeine. I'm gonna need hypnotherapy to get over this one.
I have nice amps, like the RSA Tomahawk and iBasso D1, why do I need to mess with Mint Tin amps? Because it's fun, and sometimes you find a beautiful pearl in that oyster that competes head to head with the big boys. The D1 beats everything I have for sound quality but it's big and I only use it through the DAC, so I wont compare it here with analog only input amps (which with opamp rolling makes its analog sound world class as well). While the Tomahawk beats everything with its size, it doesn't have bass boost which is a real bummer sometimes but not enough to get rid of it yet. If I was told I could only have one of these three Mint Tin amps to wake up my day, then I gotta get me some Caffeine!
A FINAL NOTE: I think that it helps people to know how burn-in affects the sound, so some people don't take ONE listen to it and then put it away because it didn't have the sound they were hoping for, before it gets burned-in and sounds like it should. I had that issue with the Caffeine and J Seaber cmoy bass boost, sounding compressed and grainy at first - but I found that it sounded much better after running for a day, and with 3-7 days of running (75-150 hours) there is still more improvement with all of them. The Royal sounded great right out of the box, but I noted in my first assessment that it didn't have the level of bass or sound stage of the tomahawk. BOTH of those issues got much better with more run time on the Royal - with 150 hours on it I noted the bass had filled in nicely, and I noted that the sound stage was matching my Tomahawk by 250-300 hours.
A detailed review of the J. Seaber CMoy bass boost and Penguin Royal should be viewed at http://www.head-fi.org/forums/showthread.php?t=258868 first, including updates added around the middle of September 2007 as the Royal passed the Tomahawk for bass and soundstage. Also, my review of the iBasso D1, comparing that to the Royal and Tomahawk is here http://www.head-fi.org/forums/showpo...postcount=1054
ADDITIONAL NOTES: I MADE AN INQUIRY. THE OPAMPS IN THE CAFFEINE ARE NOT SOCKETED, SO NO ROLLING. THE OPAMPS ON THE HEADSTAGE LYRIX COMMERCIAL VERSION BOUGHT ON EBAY ARE ONLY SOCKETED IF REQUESTED AT THE TIME OF ORDER FOR AN EXTRA $20, CALLED THE "TOTAL" UPGRADE.
PROCEDURE: The PenguinAmp Caffeine and J. Seaber CMoy bass boost were both run with music for approximately 150 hours prior to this review. The PenginAmp Royal has over 350 hours on it now. The Caffeine needed some burn-in for grainy or harsh sound through my ER6i, and it transformed at about 70 hours, loosing the grainy-ness and opening up/widening up. If I recall correctly, the J. Seaber CMoy bass boost with similar sound issues took 24-48 hours to transform, while the Royal sounded great right out of the box and just got better and better. The Royal transformed between 150-250 hours, and grew some balls in the bass while becoming even more transparent than before.
This review will focus mostly on the newest addition, the Caffeine. All three amps were tried with the Livewires first, and all music selections were played on all amps. Then this was repeated with the ER6i and then the HD600's. Testing was done when all three amps had been tried with all three headphones, and all music selections had been played. To get the best sound, a dock line out was used, but it was impossible to listen to the Seaber CMoy with dock-line out and a volume attenuator - the line out simply had too much signal gain and it overdrives the Seaber's input into distortion. So, all three were also listened to with headphone out. Except where headphone out is mentioned, assume the dock line out was used.
SOURCE: 30gb and 80gb iPod video, used only with 320kbps VBR and higher, including apple lossless.
CABLES: Custom made 3.5mm to 3.5mm interconnect, Send Station Dock Line Out, Shure volume attenuator (my cryodock wasn't available for this test).
HEADPHONES: Etymotic ER6i, Livewires customs, Sennheiser HD600. (I listened briefly with my Shure E500 and Ultrasone HFI700 to confirm what bass boost does with phones with good bass, but there is no need to run bass boost with these phones).
PROGRAM MATERIAL: Arne Domnerus "Jazz at the Pawnshop", The Tord Gustavsen Trio "Being There", The Rippingtons "20th Anniversary", Jesse Cook "Montreal (Live)", Diana Krall "Live in Paris", Lord of the Rings "Return of the King" soundtrack, Sir Collin Davis London Symphony "Sibelius: Kullervo", Pixies "Mass of Destruction", Good Charlotte "Good Morning Revival", Pink "I'm Not Dead Yet", Ani Di Franco "Knuckle Down", Jack Johnson "In Between Dreams".
AMP FEATURES, customer support and Price: Best bang for the buck Winner = Caffeine: Robert Gehrke at PenguinAmp is very responsive to emails, but his day/night hours are different because he is located in Germany. The "Caffeine" model has recently been revamped to two models - an economical $49 model and the bass boost with gain for $69. It now features an AD8397 opamp like the Royal, volume control plus a hi-low gain switch, bass boost on/off switch, a 9v-18v charging circuit for 9v battery, and production-line quality build but in a mint-tin case. The charging jack is located inside the amp, to minimize the chance of pocket fuzz getting insie the hole. Retail is $69. This amp was a free review unit, but I will offer to buy it after the review.
The Royal also uses the AD8397, has dual rail-splitters for more current, adds larger nichicon capacitors like the Hornet non-M, but lacks the gain and bass boost switches (neither of which is needed as you'll see). It too has a charging circuit, but unlike the Caffeine, it also allows the un-amplified sound to pass-through when the amplifier is off (limited usefulness with dock line out). I paid $89 new on ebay, retail is $99.
John Seaber is also very responsive to emails, and has been willing to add customized features to his amps. On this forum his user name is "Blackinches". My J. Seaber CMoy bass boost v1.48 lacks a volume control, and is designed to run from the headphone out of your source. It does have a bass boost switch between the input and headphone out where the PenguinAmps place a volume control. It has an optional hi-low gain switch hidden inside, but when not made custom the switch woudl go through a hole in the side of the tin. It lacks a power on switch, but turns on when you plug in the source to the input jack. It can be powered by a 9v - 24v "regulated" power supply, which when plugged in will disconnect the battery. There is no charging circuit. I use just the plug-tip from a universal power supply to plug the power-jack, and this also serves as a power off switch so I don't have to disconnect the source to turn it off. Price was $45 with the options, and a volume knob was a $10 option but was out of stock at the time. Note, a new model with volume control as part of the new circuit board, and no gain switch will be available in about 2 weeks.
BUILD quality: Winner = Caffeine ties Royal just because I love big caps vs cool power connectors with integrated boost and gain switches. All amps have a nice professionally made circuit board. The PenguinAmp Caffeine and Royal have a cleaner look with the circuit board inverted so no components are seen (offering more protection from damage), while the Seaber circuit board has all the components visible in all their glory. The extra wires in my photo are from the optional gain switch - I begged to have it hidden inside the case to make the amp slimmer. The Caffeine has a quite unusual connection for the 9v battery, being incorporated into the circuit board instead of dangling off by a wire. The battery is held in place quite securely. The build quality of the Penguin Amps is something you'd expect to find being sold in a Hammond aluminum case for 2-3x the retail price. At least the Caffeine comes in a neat HoloGraphic Penguin mint tin, which is pretty under track lights.
MAX VOLUME, HISS AND GAIN: Winner = Caffeine ties Royal again : The amp is powerful and drives my Sennheiser HD600 fine on high gain, as does the Royal. The Seaber high gain was set up for HD280 pros, and doesn't go as loud with HD600 as the Caffeine before distortion. With the Caffeine on low gain, connected to a paused iPod via headphone jack, with iPod volume at anything above zero, the Caffeine is very quiet. Starting at "zero" on the Caffeine volume knob (which is about 6 o'clock) rotating the volume clockwise to about 12 noon it remains silent, even with the Livewires. In using this amp, I found no reason to ever go past 12 noon on the volume dial with high efficiency IEMs like the Livewires - past that it will just be too loud for comfort.
There is a slight hiss beginning between 12 noon and 1 o'clock. But the music will always be well above the level of background hiss. By 4 o'clock the Caffeine's volume knob is at max, and hiss is very noticable. Unplug the iPod, with amp on and headphones connected, and the hiss is VERY quiet. The S/N ratio seems quite good in the usable range of the volume knob (6 o'clock - 1 o'clock), and hiss is never audible above the program material, even in very quiet passages with loud volumes in dynamic passages.
On low gain, the hiss with the Seaber Bass Boost is considerable with the Livewires - since there is no volume knob, a volume attenuator is a must. With the Shure volume attenuator, just rolling the attenuator's knob by 4mm will knock out a fair amount of hiss, and most of hiss is gone by 6-8mm (and volume levels are similar to that of the Caffeine with volume knob set at 12 noon). With no attenuator and both amps set to low gain, and the Caffeine volume set at max (Seaber is already at max), the music volume levels on the Caffeine are similar to the Seaber, and they both become intolerably loud at 50% of iPod volume or more - but, the Caffeine has maybe 2-3 db less hiss between songs. (Again, there is no reason to go past 12 noon on the volume knob to get quite loud, and hiss is inaudible at that setting.)
BASS: Winner = Caffeine, Royal a close second: The Caffeine with Bass boost switch off strikes me as clean, quick, controlled and flat - i.e it is decidedly flat/neutral, without the punch of the 350 hour burned-in Royal. With the bass boost switch on it was still a very natural sounding bass with just more bass present - this puts the Royal's bass between the Caffeine with boost off and the Caffeine with boost on. Bass boost is not muddy, seems to boost the 8-9db that is claimed, feels boosted mostly below 120-150hz (I didn't ask) and works well with a wide variety of headphones and music. It just doesn't sound like someone turned on EQ, but rather it sounds like the music was meant to have that amount of bass.
The J. Seaber bass boost is maybe an additional 3db more pronounced, and the boost seems to begin at a little higher frequency at maybe 180-220hz. It is great with some music, but not with all music, unlike the Caffeine. I say this in the sense that the Seaber bass boost can overpower some earphones and material, and sounds somehwat unlike it should at times. Case in point, The Rippingtons. The Rippingtons benefit from the Caffeine's bass boost but they sounded a little overboosted with the Seaber. Same with Tord Gustavsen Trio - with the Seaber bass boost turned on, the string bass at 50% volume overdrives the Livewires, is distorting and showing some extra harmonics. The Caffeine bass boost seems to suck less current so the max clean sound levels achievable with the Caffeine seem like they are 2-3db higher when both have bass boost turned on.
The Royal has no bass boost but it sounds like it carries more weight in the bass in loud passages, I will call it "mass". Even if the volume of bass is greater with the Caffeine and Seaber with boost, the Royal is like Bam Bam Bam! vs Thump Thump Thump. Royal has two large nichicon caps like the Hornet non-M, and twin ground rail splitters for more current capability. But at volumes normal people listen at, the Caffeine is the most versatile in the bass.
MIDS: Winner = Royal by a hair: Mids from the Caffeine are full and forward, vocals sound true and present. I notice no sucked-out mids to simulate a wider sound stage like some amps or headphones. I had no issues or complaints with any of the amps mids, and all three amps made listening to my ER6i enjoyable by removing the harsh upper mids, especially with pianos. The Royal had the best mids, almost described as lush, or "solid" would be another word - instruments and voices have substance, they're almost tactile. With the Royal and the Caffeine, the pianos saxophones and clarinets sounded closer to being there than when listening to the headphones plugged directly into the iPod.
TREBLE: Caffeine ties Royal: The caffeine's highs are sparkly and clear. The Seaber is close, but a just a smidge weaker. The edge to violins is all there in the Penguin, but at 95% in the Seaber. The sound is not overly bright, or sibilant, and is very similar to the Royal.
SOUNDSTAGE: Caffeine ties Royal: The soundstage is open, reflecting the venue where the recording was made. After 150 hours burn-in, the soundstage is more open and less compressed than music right out of the headphone jack or from the J. Seaber amp. Interestingly, The Caffeine with Livewires made the headphone out actually sound good - it took the Royal 250-300 hours to achieve that. For a while I wondered if Robert, the designer, had snuck a cross-feed circuit or some other trickery into the amp, but the Royal has a similar wide open soundstage too. The Penguins rival my RSA Tomahawk, but, moving up a whole 'nother league, it is less wide than going through my iBasso D1 via optical input (not fair
SUMMARY: Winner = Caffeine by a hair over the Royal, far ahead of the Seaber: Certain headphones need MORE bass to sound just right, such as the ER6i Some produce plenty of bass but benefit from a little extra, like the Livewires and HD600. Some make great bass and any extra would simply be too much (Shure E500 and Ultrasone HFI7000). The Caffeine seems to get along with all these headphones. I keep pretending that the Caffeine turns my HD600's (with black dragon cables) into a not-so-dark HD650 with better treble.
With bass boost on, the Caffeine has less distortion at high volumes than the Seaber. The moderate level of bass boost and choice of frequencies boosted helps maintain a more natural sound. It also allows use with a wider variety of headphones, being less likely to over-drive them. The sound quality is excellent, out of line with its cost, and it can drive low-sensitivity high-impedance headphones as well as it drives high-sensitivity low-impedance earphones.
And any hiss with the low-impedance earphones at low volumes (aka Livewires) can be minimized by keeping the volume knob turned down to below maximum. Using the Dock-line out or headphone out, you will never have the volume turned up high enough (not past 1 o'clock) to make hiss an issue. The hiss is an issue with the Livewires not the amp, and my iBasso D1 behaves the same way as the Caffeine. The lack of volume control is an issue with the Seaber amp, but fortunately a volume attenuator can help the hiss, but this degrades the sound quality with some phones if too much attenuation (more veiled, less airy).
I've always been biased towards big caps, even when they aren't needed. It may be a placebo to me sometimes, but I really like the heft of the Royal with the big caps, and I wonder if it isn't just my imagination about the Royal's bass having more "mass" even though the bass volume is less than the caffeine. I'm gonna need hypnotherapy to get over this one.
I have nice amps, like the RSA Tomahawk and iBasso D1, why do I need to mess with Mint Tin amps? Because it's fun, and sometimes you find a beautiful pearl in that oyster that competes head to head with the big boys. The D1 beats everything I have for sound quality but it's big and I only use it through the DAC, so I wont compare it here with analog only input amps (which with opamp rolling makes its analog sound world class as well). While the Tomahawk beats everything with its size, it doesn't have bass boost which is a real bummer sometimes but not enough to get rid of it yet. If I was told I could only have one of these three Mint Tin amps to wake up my day, then I gotta get me some Caffeine!
A FINAL NOTE: I think that it helps people to know how burn-in affects the sound, so some people don't take ONE listen to it and then put it away because it didn't have the sound they were hoping for, before it gets burned-in and sounds like it should. I had that issue with the Caffeine and J Seaber cmoy bass boost, sounding compressed and grainy at first - but I found that it sounded much better after running for a day, and with 3-7 days of running (75-150 hours) there is still more improvement with all of them. The Royal sounded great right out of the box, but I noted in my first assessment that it didn't have the level of bass or sound stage of the tomahawk. BOTH of those issues got much better with more run time on the Royal - with 150 hours on it I noted the bass had filled in nicely, and I noted that the sound stage was matching my Tomahawk by 250-300 hours.
