Bass Gear Issue 7 : Page 50

TEST! bass gear The Current State of iPad/iPhone Interface Options By Tom Lees Time marches on, and so does technology. If you are still wearing your Members Only jacket and parachute pants, you may not have heard of, or care about, this thing called the iPad ® . If that is the case… move along, there is nothing here for you to see. For everyone else out there, listen up. To some of you, this technology may be a game changer. I put the AmpliTube iRig ® , the Peavey Ampkit™ and the POCKETLABWORKS iRiffPort™ through their paces in the lab, in my practice space and on stage. The verdict? This technology is awesome today, and is only going to get better. The winner? I think the better question you should all be asking is, which one or more of these interfaces is right for your needs. As a preliminary matter, this review will not focus on software. While I will comment on certain features that are %&& &#1b;&#1c; !$%# Fig 1A iRig Fig 1B Ampkit Fig 1C iRiffPort

The Current State Of Ipad/Iphone Interface Options

Tom Lees

Time marches on, and so does technology. If you are still wearing your Members Only jacket and parachute pants, you may not have heard of, or care about, this thing called the iPad®. If that is the case… move along, there is nothing here for you to see. For everyone else out there, listen up. To some of you, this technology may be a game changer. I put the AmpliTube iRig®, the Peavey Ampkit™ and the POCKETLABWORKS iRiffPort™ through their paces in the lab, in my practice space and on stage. The verdict? This technology is awesome today, and is only going to get better.The winner? I think the better question you should all be asking is, which one or more of these interfaces is right for your needs. As a preliminary matter, this review will not focus on software. While I will comment on certain features that are of interest or noteworthy, the ultimate decision as to whether you like or dislike a particular interface is a subjective matter. Moreover, software updates and upgrades occur on these products at a relatively quick rate. Still further, with certain notable exceptions, you can mix and match interfaces and software – but there will be more on that to come. With that in mind, to test these interface units, a software “loopback” app was used to fold the input back out to the output. This was done internal to the iOS device without requiring the audio to be processed by a modeling app. This tool thus allowed us to compare the electrical characteristics of the interface devices without the influence of one manufacturer’s interpretation of an amp model. It also ensured that all settings during testing were the same and repeatable. For the testing herein, the volume of the test iOS device (iPad 1) was set to maximum. So, let’s jump in and take a look at some of the defining features of these interfaces. Preliminarily, the Figures having an ‘A’ designation correspond to the iRig, a ‘B’ designation correspond to the Ampkit, and a ‘C’ designation correspond to the iRiffPort. Form Factor The AmpliTube iRig interface shown in Fig. 1A, is packaged in a generally cylindrical tube having a 1/4” instrument jack input on one end. A 4” cable extends from a second end of the adapter opposite the instrument jack and is terminated in a 1/8” male tip, ring, ring sleeve (TRRS) connector for plugging into the audio port on an iPhone®or iPad. As such, audio enters and exits the mobile device through the 1/8” audio jack. The adapter also includes a 1/8” stereo jack on the other end for plugging in a set of headphones, an amp, etc. To use the interface, you plug your bass guitar into the interface using a standard instrument cable. The bass signal flows into the interface through the guitar jack, through the cylinder and into the mobile device via the built-in 1/8” TRRS cable. Your processed bass guitar signal exits the mobile device back out the 1/8” TRRS cable, back through the interface and out the 1/8” jack to your favorite headphones, amplifier or other source. As such, you will need to provide two cables to really get this interface up and running. Notably, the iRig interface itself does not require power. This is one of the really cool features of this interface and will be discussed below. The Peavey Ampkit interface shown in Fig. 1B, is packaged in a generally rectangular package that holds two AAA batteries for powering internal electronics. The electronics within the Ampkit provide some unique opportunities, as will be described in greater detail below. One end of the Ampkit interface includes a 1/4” instrument jack and a 1/8” jack for plugging in a set of headphones, an amp, etc. The opposite end of the interface includes a 14.5” cable terminated in a 1/8” TRRS male connector for plugging into the audio port on an iPhone or iPad. Thus, like the iRig interface, you plug your bass guitar into the interface using a standard instrument cable. The bass signal flows into the interface through the guitar jack, through the circuitry internal to the interface housing and into the mobile device via the built-in 1/8” TRRS cable. Your processed bass guitar signal exits the mobile device back out the 1/8” TRRS cable, back through the electronics in the interface housing and out the 1/8” jack to your favorite headphones, amplifier or other source. Two cables are also required for this interface. The iRiffPort interface shown in Fig. 1C, takes a completely different approach and uses a 6’ cable. One end of the cable is terminated in a housing having a 1/4” plug that you can plug directly into your bass, so no instrument cable is needed. The rear of the housing opposite the 1/4” plug provides a 1/8” stereo jack for plugging in a set of headphones. As such, there is no need to run your headphone wire clear to the mobile device. Rather, you merely need the headphone cable to reach your instrument jack. The opposite end of the cable is terminated in an Apple dock connector. The back end of the housing for the dock connector supplies a line out on a1/8” stereo jack. As such, line out and headphone out connections are separated by the length of the cable. This allows the user to run a line out cable to an amp or other source in a convenient and tidy manner. In use, your bass signal flows through the provided cable, into the iRiffPort housing, where it is processed by electronics within the cable. The audio then flows through the dock connector and not the 1/8” audio jack on the mobile device. Frequency Response Both the iRig (Fig. 2A) and Ampkit (Fig. 2B) have substantially the same frequency response. In general, these interfaces exhibit a low-frequency attenuation and a slight ringing in the high frequencies while connected to the test analyzer. These features are likely a compromise to address the inherent limitations in passing mono audio in, and stereo audio out through the single 1/8” TRRS connection of the iPad/iPhone. The iRiffPort (Fig. 2C) demonstrates a substantially flat full-range response. The frequency response of these interfaces suggests that there are significant advantages of using the dock connector if full range, flat frequency response is required. Input headroom To get a sense of the performance of these interfaces, I took a look at a characteristic that compares the input level to the output level for various target amounts of distortion. Figs. 3- 6 illustrate 1%, 5%, 10% and 20% THD+N measurements respectively. Looking first at the 1% THD+N charts, the iRig (Fig. 3A) hit the 1% THD+N target with a 640 mVrms input, producing a 1Vrms output. Also note that the input is slightly out of phase with the output for the signal under test.Comparatively, the Ampkit (Fig. 3B) hit the 1% THD+N target with a 300 mVrms input, producing a 1.1 Vrms output. Here, the input is inverted relative to the output. The iRiffPort (Fig. 3C) hit the 1% THD+N target at 180 mVrms, producing 350 mVrms output. Again, the input is slightly out of phase with the output. Looking at the 5% THD+N charts, the iRig (Fig. 4A) hit the 5% THD+N target with a 700 mVrms input, producing a 1Vrms output. We measured some weird distortion artifacts at the peaks of the output signals. Comparatively, the Ampkit (Fig. 4B) hit the 5% THD+N target with a 340 mVrms input, producing a 1.2 Vrms output and showing signs of classic solid state clipping. The iRiffPort (Fig. 4C) hit the 5% THD+N target at 338 mVrms, producing 600 mVrms output and appeared to have entered a soft-clipping or wave-shaping mode. Looking at the 10% THD+N charts, the iRig (Fig. 5A) hit the 10% THD+N target with a 818 mVrms input, producing a 1Vrms output. Here, the distortion artifacts became more visibly pronounced. Comparatively, the Ampkit (Fig. 5B) hit the 10% THD+N target with a 389 mVrms input, producing a 1.3 Vrms output and exhibiting progressive and predictable hard clipping. The iRiffPort (Fig. 5C) hit the 10% THD+N target at 519 mVrms, producing 800 mVrms output. The clipping appears more asymmetrically pronounced with an exaggerated rounding of the bottom cycle compared to the upper cycle of the waveform. Just for fun, I cranked up the input levels to produce 20% THD+N to see how these interfaces would react in the steady state. The iRig (Fig. 6A) hit the 20% THD+N mark with a 1.2 Vrms input, producing a 1.1 Vrms output.Comparatively, the Ampkit (Fig. 6B) hit the 20% THD+N target with a 550 mVrms input, producing a 1.4 Vrms output and the iRiffPort (Fig. 6C) hit the target at 900 mVrms, producing 1 Vrms output. There is quite a bit to be groomed from this information.First, let’s compare the iRig and Ampkit (because they both use the 1/8” jack on mobile device for connectivity).Because the non-powered iRig has relatively less gain than the Ampkit, the iRig handled larger signals more gracefully before causing clipping at the output, as would be expected. On the other hand, the Ampkit, due to its internal active circuitry, produced more overall level and gain compared to the iRig. However, in an iOS device such as the iPad, there is a fixed ceiling in the output level. Accordingly, this apparent limitation in input level is not so much a shortcoming of the Ampkit, but rather, a reasonable tradeoff that Peavey made in view of the iOS ceiling, the gain that Peavey intended from their device to balance noise and feedback and to suit the characteristics of their amp models, which can lean towards large amounts of distortion. One clearly evident feature of the Ampkit is its analog behavior when hitting the ceiling. As seen in Figs. 3B, 4B, 5Band 6B, as the level increases, the output enters hard clipping of the peaks. The iRiffPort actually hits the 1% THD+N mark with the lowest input of the test group (180 mVrms). However, the iRiffPort apparently implements soft asymmetric limiting circuitry that allows the output to gracefully distort relative to large input level swings as seen in Figs. 3C, 4C, 5C and 6C. This allows a relatively wide dynamic gain of the input signal, despite the unavoidably low iOS ceiling. For instance, the iRig allowed an input signal increase of 560 mVrms between 1% and 20% distortion, with a 60 mVrms increase from 1% to 5% distortion. The Ampkit allowed and input signal increase of 220 mVrms between 1% and 20% distortion, with a 40 mVrms increase from 1% to 5% distortion. The iRiffPort allowed an increase of 720 mVrms between 1% and 20% distortion, with a 158 mVrms increase from 1% to 5% distortion. Figs. 7A, 7Band 7Cillustrate the iRig, Ampkit and iRiffPort interfaces in response to a 1Vrms input signal for purposes of comparing overload and phase at a common input level.Correspondingly, Figs. 8A, 8B and 8C illustrate the input compared to the output at the point of clipping of the output signal. Figs. 9A, 9B and 9C illustrate the harmonic spectrum of each interface in response to a 1Vrms, 1 kHz input signal. In the spectral traces herein, the iRig shows relatively stronger odd-order harmonics compared to adjacent even-order harmonics. The plot also shows an extended harmonic spectrum where the odd-order harmonics dominate the even-order harmonics into the higher order. This seems to correspond with the scope plots showing the effects of clipping due to hitting the iOS output ceiling. The Ampkit shows slightly stronger odd-order harmonics compared to adjacent even-order harmonics, but not as exaggerated as the plot for the iRig. The higher order harmonic levels follow a clear, downward step in this spectral plot that tracks well with what we would expect given the typical hard limiting response of the signal to hitting the iOS ceiling. The iRiffPort shows a dramatic rolloff of higher order harmonics. Moreover, the harmonics drop off in a nicely defined slope. These effects track with the earlier observation of asymmetric soft-limiting of the signal. Figs. 10A, 10B and 10C illustrate gain compared to input level. The iRig shows a gain of just under 3.75dB with a slight variance between left and right channels. The input gain drops off after crossing a hard knee just past 600 mVrms input. Again, this tracks with our earlier findings for this interface. The Ampkit shows a gain just over 11dB again, with a slight variance between left and right channels.The gain begins to drop off just past a knee just over 300 mVrms. This is consistent with earlier findings for this interface. The iRiffPort shows a gain just over 6dB, also with a slight variance between left and right channels.Again, this is consistent with earlier findings for this interface. In comparing the gain characteristics of these three interfaces in Figs. 10A, 10B and 10C, the softclipping/ limiter of the iRiffPort is clearly evident with the curved roll-off of gain, compared to the hard knee of the iRig and Ampkit. Figs. 11A, 11B and 11C illustrate distortion as a function of input level. As each chart illustrates, the distortion characteristics track well with other features described more fully herein. Software The iRig software, Fig. 12A, is designed predominantly for guitarists. However, a bass amp model is provided.Moverover, the iRig software allows the user select up to four effects pedals, as well as select a speaker cabinet configuration. The software also includes a tuner, metronome, recorder and an ability to load songs from an iTunes® account, set loop points and adjust the playback speed of the backing track. The iRig software will work with both the iRig and Ampkit interfaces (both using the 1/8” audio jack of the iOS device), but the iRig software (as of the time of this review) will not work with the iRiffPort interface. This is apparently, an issue with the iRig software, not the iRiffPort interface. The Ampkit software, Fig. 12B, is also designed predominantly for guitarists, and really excels in distortion tones. However, bass players will find a bass model labeled American Bass King. Moreover, Ampkit allows the user to set up a chain of effects pedals, as well as select a speaker cabinet. The software also includes a tuner, metronome and the ability to load songs from an iTunes account. The Ampkit software worked with every interface tested.The iRiffPort, Fig. 12C, includes a separate app for a Gallien-Krueger bass amp. The iRiffPort also includes a separate app for guitar. The Gallien-Krueger app includes a page for setting the contour, boost level, horn level and master output level. A separate page provides access to treble, hi-mid, low mid, bass and gate controls. The user can also select between a 4x10 and a 1x15 cab. The app allows the user the ability to save presets and includes access to your iTunes library to play along with your own music, adjust the playback pitch and speed of songs and set loop points. Conclusion I especially like the fact that the iRig interface is small and does not need power from a battery. At the low price point (under $40.00) this device carries, you should buy this device, regardless if you also decide to buy one or more of the other interfaces. The Ampkit uses a battery, which allows better control over higher gain amp model settings, compared to the iRig. In fact, this interface provides the largest gain of the interfaces tested in this review. This interface also carries a low street price of $29.99 direct from Peavey. The iRiffPort, with its dock connector interface, turned in the best “on-bench” measurements. Another really cool feature of this device is that the interface has a separate jack for line out (at the dock port connector) and headphones (at the instrument jack connector), providing a lot of convenience in how this device is utilized. Further, the internal circuitry is powered by the dock connector eliminating the need to mess around with batteries or worrying about power. However, this unit is substantially more expensive than the iRig and the Ampkit, running about $99.99 at most retail outlets in the US. IRiffPort also offers a “trade-up program” where you can receive a discount if you already own a competitive iOS guitar interface. I gig-tested, jammed on, practiced with and otherwise worked out all three interfaces and software apps on an iPad (playing guitar, not bass, mind you). The verdict? In my duo act, this concept rocks. No lugging amps or heavy gear, just an instrument, iPad, interface and cable to the PA. The tone is not going to replace a nice amp, but for convenience, portability or even as a backup, this is a hard option to ignore. I not only survived gigs, but I flat-out enjoyed them because of the convenience of the interface. Also, having an iPad on stage, conspicuously turned towards the crowd almost ensured that I would have no problem finding someone in the audience that was curious enough about the technology to talk with through the set break. I do have one comment. For practicing, where you can set the iPad on a desk, each of the interfaces work great. But live, while their tone is giggable, the mechanical connections do not inspire confidence. There are many products that allow an iPad to be mounted on a mic stand.However, these interfaces, especially the iRig, with its 4” cable, do not lend themselves to easy, professional attachment to an iPad clip for live use. Moreover, the thin 1/8” stereo mini jack for audio out is not a cable that I would commonly carry. For the duo act, where I was predominantly stationary, the mechanics of connecting the iPad to a mic clip for live use was not bad. But if I were performing in a band setting, I would go out of my way to ensure that a rock star jump would not result in pulling the iPad off the mic stand, etc. At the end of the day, the iPad interface may not be for everyone. But as a practice tool, all three options are top notch compared to alternative technology. The ability to interface with your iTunes library, play along with tracks and even speed up, slow down and set loop points as in some of the tested software, make these tools infinitely cool.As a live tool, it is usable now and will only get better. So which one? I have uses for them all, because in the right circumstance, each has its merits, strengths and advantages.

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