Hardware

From WiKPA
Jump to: navigation, search

For integrating the Profiling Amp with other hardware, see Other Hardware.

Currently there are 5 incarnations of the Kemper Profiling Amplifier in total:


Commonalities

All 5 versions of the KPA run the same firmware and have the same input connections. Their internal sound processing is identical, so there's no difference between the 5 versions soundwise.


Differences

Form Factor

There are 2 different form factors available. The Head and the Rack version. As of July, 2013 three different versions of the Profiler head alone exist, which differ because of slightly different measures. Specifically, the black cavity measures are different from each other, so care should be put in the purchase if planning to retrofit the unit with a personally-chosen poweramp or for any other sensible purpose. Details will be published here ASAP.

The design of the various versions has already led to some nice nicknames for the units. Everybody in the community will know what you're talking about when you write "toaster" or "lunchbox". Of course the head, having hit the market first, has got more nicks. But the Rack versions are getting their share


Unpowered / Powered

There are 3 different unpowered versions of the KPA.

  • White Kemper Profiler Head
  • Black Kemper Profiler Head
  • Black Kemper Profiler Rack

The unpowered Kemper Profiler Heads have a hole on the back side where you can install a 3rd party power amp. The unpowered Kemper Profiler Rack can't be equipped with a power amp.

And there are 2 different powered versions of the Kemper Profiler.

  • Black Kemper Profiler PowerHead
  • Black Kemper Profiler PowerRack

The powered versions have single channel (mono) 600 Watts @ 8 Ohm or 300 Watts @ 16 Ohm.

Output connections on unpowered and powered Profiler are the same, except for the added Speaker Output (1/4" TS connector) on the back panel of the powered versions. So, basically you can use the non-powered monitor or main stereo outputs on the powered versions. The only difference between the powered and non-powered versions of the KPA is the one extra powered output. All the other outputs on the back are identical.

WARNING: Be very careful when you connect a cable to this Speaker Output! Read the warning beneath the connector!


White Kemper Profiler Head

This was the first version shipped by Kemper and it has some minor differences to the newer versions.

  • On the front panel you'll find a button labelled "MASTER". This has been renamed to "OUTPUT" in newer versions of the KPA.
  • Some of the very first white KPA Heads didn't have Kensington lock holes on the back panel while the black KPA Heads have them.


Rack vs. Head

  • The Rack versions have the benefit of a USB A connector on the front panel. So it's much easier to connect or remove a pen drive on a Rack version.
  • Because of the form factor of the rack version it does not have the LED collars around the 4 dials below the LCD screen and it does not have the 2 dials for MOD Rate and MOD Intensity that you have on the Head versions.


Technical Specifications

Here's the link to a detailed list of Technical Specifications for the Kemper Profiling Amplifier.


The powered Profiler

The poweramp coming with the powered versions is mono. The actual power amp used in the Kemper Profiler PowerHead and PowerRack is the ICEpower 250ASX2. It is fed by the monitor output signal. You can use the Monitor out and the power amp out simultaneously. When you don't need the power amp for a while, you can switch it off separately. When using the poweramp, you can run a 4 Ω speaker, but this is formally out of the specifications. If you are careful, then it's no problem; but you run the risk of seriously damaging the power amp if driven too hot.

Several discussions exists in regard with "filling the void" in the back of the KPA. It is difficult to comprehend, why a simple insert by DIY or performed by the factory will not work. Here is musicman65 on the legal & technical side for DIY solution:

A company can't waive your right to sue them if they provide the method and instrument to modify their product. The fact that you promised not to sue in advance has little value in court. A third rate hack attorney would have a field day in court in that situation. The UL listing certification and whatever overseas certs would be lost and they would be open to litigation in the advent the installer got hurt. An improperly installed power amp can be potentially deadly. The ground on your guitar, which is connected to your strings, goes through the guitar chord to the amp. If the line and neutral are inverted or the line shorts to the chassis and its ungrounded, a lethal shock could (will) occur. Kemper has decided this is not a position they want to be in.

-musicman65 @ Kemper Forum, July 19th 2013
 

In the same thread the user nakedzen identifies the EU legislatiion as the "culprit":

I think it was because EU legislation sees every KPA they'd install a power amp into as a completely new device that needs to be certified and tested. A lot of hassle and red tape.

-nakedzen @ Kemper Forum, July 24 2013
 


Powered Profiler and heat dissipation

You can feel confident that the powered version of your profiler (whichever it is) will never overheat even when framed in a tight rack. The power amplifier is designed to work in operational class D, which dissipates very, very few.

Class D poweramps run very cool. Even after two hours of running they're only slightly warm.

-guitartone
 


Class D. When it has fever temperature, you will have tinnitus :)

-ckemper
 


Using the Profiler's outputs

You can feed 2 PA's from the 2 XLR Outs as your live monitor rig, and use the other 2 main outputs to go FOH, using all 4 outputs at the same time.


Are there any differences in the way Monitor Out and Main out sound ?

Q: Over the last 7 months I have used the Profiler via monitor out only. After watching a video I decided to use instead the Main out. My reward was instant. The tone was much improved.

The Main outs produce the same sound as the Monitor output with both cab on\off.

-ckemper
 

One thing that could have given you a sudden 'better sound' when switching to main output versus the monitor is simply volume. In the master menus you can set up relationships between the main output and the monitor output and lock them so turning the knob changes both. One can be locked at a different level to the other and turning the main output knob adjusts both, different levels, by the same rate. If the monitor was set lower than the main and changed the cable from monitor to main you would hear a 'better' sound.

-randombastage @ The Gear Page, 03-26-2013
 

Other than that there are separate EQ settings for monitor and main which could account for a difference... Or if you had Monitor Cab Off checked for the Monitor output but had Cab on for Main output when you compared them. I think if you make sure the EQ's are both the same for the two outputs and the volumes are also the same you shouldn't hear any difference. Assuming you are using the same cable into the same amp set the same way.

Using a Real Cab

Apart from the Main out allowing for a stereo signal to be sent to an amp, a couple of monitors or to a PA, and the Monitor out being mono, the Monitor out also allows you to exclue the cab portion of the signal in case you intend to use a guitar cab, while still keeping the cab emulation on the Main out. If you want to exclude the cab from all of the outs you can just press the Cab button on the front panel.


Disassembling the Profiler

Are you curious about what your Profiler looks like inside? Here’s a video showing it!

WARNING: This is not a suggestion to open the unit or to fix any degree of troubles by yourself! I just posted this because I assume you’re an adult and responsible individual, but at the same time I strongly discourage you from trying. By trying and open the unit by yourself you expose yourself to several risks: risk of damaging the unit, risk of hurting yourself if you do not know exactly what you’re doing, and risk to voiding the guaranty.

In case you experience any issue that might be related to hardware, and still feel like opening the unit, I’d strongly advise you to contact Kemper for take agreements and ask about guaranty voiding.


Ins & Outs, levels and impedance

How to be sure that our Profiler matches properly with the rest of our rig, impedance-wise?

The Direct Output is a low impedance output. But that is no problem, since high Z inputs like amp inputs are capable of taking even low impedances without colouring the sound. Active guitars e.g. have a low output impedance. A mismatch would only occur, if the impedances come close, but in our case the ratio is made even higher. More generally speaking, there are two output and two input situations:

  1. Low impedance output (line output, active guitar/bass, Profiler Direct output), less than 600 Ω;
  2. High impedance output (passive guitar, reamping device), more than 5000 Ω;
  3. Low impedance input (line input, some guitar effects such as Fuzz Face), less than 20 kΩ;
  4. High impedance input (tube amp, Hi Z input, regular guitar effects, Profiler Instrument input), more than 200 kΩ.

The rule of thumb is: if the output impedance is much lower than the input impedance, everything will work fine. The input will not draw significant current, and the sound will not be coloured.

All the above-mentioned combinations are OK, except the 2. and 3., that is high impedance output into low impedance input. This combination especially includes: passive guitar into Fuzz Face, and reamping device into Fuzz face or other low impedance pedals. In these cases, the guitar pickup is heavily loaded by the low impedance, thus colouring the sound. Different pickups undergo a different colouring, caused by the high dependency between both the pickup and input impedance. This is what we are used to, this is how we experience the sound of these pedals in combination with our guitar. Manufacturers of reamp boxes advertise to match the impedance of a guitar. But how could they? Every pickup is different. Different switched combinations of pickups will have different effects. The passive volume and tone control of the guitar has another dramatically effect to the impedance and thus the sound. This cannot be matched by any other device than the original guitar, unfortunately. No interconnected device can perfectly match the sound of a guitar directly connected to a low impedance pedal like the Fuzz Face. The Profiler cannot match it, a reamping box can't either. Even if you insert any kind of regular stomp effect between your guitar and a Fuzz Face, the sound will change dramatically. The story is different with the tube amp input. It has a very high impedance and will not colour the connected device. You can connect everything to it, the impedance does not matter, only the level has to be adjusted. The Profiler provides the right level on the Direct Output. The way from the Instrument Input to the Direct Output is simply a buffer amp. An impedance match is not necessary, a reamping box is not required, as it wouldn't add a benefit to the setup. Unfortunately, the full story about impedances in the guitar and studio world is not told, by whatever reason. But things are not logical, or hidden in the dark. I have some hints:

  1. On the Web you find numerous recommendations for buffer amps, that will be connected between the guitar and the amp. Same as active guitars. Buffer amps actually create a line signal. No word that a buffer amp will "destroy" the original impedance of the guitar; that same impedance that is "reconstructed" by a reamping box. That is a clear contradiction. Some hints can be found, that a buffer amp in front of a Fuzz Face will create a nasty sound, still.
  2. There is no specific list available on the Web about those few stomp effects, that have a high impedance input and will cause trouble in many situations, such as interconnecting with other pedals or wireless systems.
  3. No manufacturer of reamping devices had the idea to use the "impedance reconstruction" to reliably drive a Fuzz Face while providing a high impedance input.
  4. No manufacturer has provided a double buffer amp (second with impedance reconstruction) to use long cables on stage, but connecting with a "pickup impedance" to the amp.
  5. Manufacturer of wireless system make no big deal about their output impedances, that go straight to the amp or the pedals. They should actually, because technically a wireless system is like reamping.

Quick conclusion: Impedances are no problem in most of the cases. Much more cases than people think! But in those rare cases where impedances become a problem, there is no perfect solution available.

-ckemper @ Kemper User Forum
 


Monitor out

Since FW 1.1.0, the Monitor Out is optimized for use with power amp and cab (with cab off on the Profiler). A complete new Eq section has been added to the Monitor out (press and hold Master to access the Output menu and scroll to the Monitor Out page). Monitor out is meant to be used for monitoring purposes, not as main signal into your DAW.


Latency

The Profiler adapts to the lowest latency possible. That is individual per rig. This will create latencies around 3 ms. When two (or more) profiles are fed by the identical audio source, the variable latency can yield to different phase relations. I can only think of two situations where this happens:

  1. Reamping and mixing the Profiler more than once by using the same guitar track for reamping. That is the situation showed by some of you.
  2. Playing two or more Profilers at the same time by splitting the guitar signal and feeding both/all Profilers with it.

The classic doubling of tracks is not an issue, because you play the guitar individually per track.

We have a hidden solution in the new public beta 1.60. Go to Output/Master menu, last page. Press soft button 4. It will light up. No message on the display. Now the profiler is on constant latency. Stays there until you press that button again. When you light up that button, you will get a higher but constant latency of about 4.9 ms.

-ckemper
 

I believe this option is no longer "hidden" but correctly labeled. I believe it is in the System menu as well. I'm on FW 2.2.1.

S/PDIF

In order to connect the Profiler to an audio interface via S/PDIF you need a S/PDIF cable. One digital S/PDIF cable can transmit a stereo signal. So you need one cable from Profiler’s S/PDIF Out to your audio interface’s S/PDIF In. If you want to do reamping you need another S/PDIF cable from your audio interface’s S/PDIF Out to Profiler’s S/PDIF In. In most cases, a simple cinch cable from your Hi-Fi will do. The Profiler runs at 44.1 kHz sampling rate and 24 bit. The audio interface must be synced to the S/PDIF Input because the Kemper Profiler has to be S/PDIF Master.

We have no plans to provide sampling frequencies other than 44.1 kHz and sync master. There are technical reasons that prevent us from implementing this.

-ckemper @ Kemper Forum, July 23rd 2013
 


Q: Is there a good reason TO be using the S/PDIF over the analog outs to the computer audio interface?

A: tylerhb - Each A/D and D/A conversion will add 1-2 ms of latency. Since the S/PDIF signals won’t need any conversion, those signals will be a little more direct (though i doubt you will feel the difference). Concerning signal quality, the S/PDIF is highly recommended if you do reamping. Normally you will lose a good amount of signal quality here. The SPDIF makes reamping very comfortable.


Signal clipping

See Sound Issues - Clipping.

Shutting the unit off

Q: I'd love to connect my Profiler to my power distributor so with one flick of the switch all my units (audio interface, MIDI floor controller, speakers etc) fire up and ready to rock. Except I'm worried about hard-stopping the Profiler but killing the power. It seems when manually powering off unit using the 'chicken head' switch it does a graceful shutdown, and I don't want to inadvertently break anything. Anyone else doing something similar?

Don't worry about the noise. We do a short cut when powering down, but it still might bleed through just a bit. But this will not harm your speakers.

-ckemper
 

Turning the unit off with the chickenhead is better, since there are indeed some procedures during shutdown. It won't break your unit when you pull the power, but to keep performance up (boot time etc.), you should, at least once a while, shut it down properly with the chickenhead to give the system a chance to shutdown properly. The general recommendation is: use the chickenhead to turn the Profiler off.

-timo
 

The Profiler does have a protection switch protecting the unit from overcurrent. This switch could get activated, if you don't properly use the chickenhead to switch off and the protection will not release before the power supply will be completely empty. You might not notice this if you shut down for more than five minutes.

-burkhard
 


Lights

The difference in brightness you can experiment on the Profiler's front in various situations is not a bug, it represents different states. For instance, the rig buttons dim, once you hit the "end" of the list of rigs you can scroll through. The stomp buttons get dim when you switch all stomps off (press Stomps to do so). Same is true for the Stack and Effects section.

Q: My Exit button is very low glowing, and Page buttons are extremely low glowing, almost not noticeable. Is it normal?

The half lit on buttons are often meant to show you an option. E.g. the Exit button lights up if you can leave a menu with it; the Page button lights up if there are more menus to the left or right.

-ckemper
 

Anyway, the basic brightness of various light elements can be adjusted on page 2/8 of the System menu.

-burkhard
 


LEDs

I found that the LED collar is very bright in default settings. I use this settings:

  • Color LEDs: 5.0;
  • Button: 6.0;
  • LED Collar: 2.0;
  • Tap: 6.8.

If you are concerned about prolonging the LEDs' life, turn down the intensity of all LEDs in the settings. This will extend their life tremendously. LEDs have a rated half-life which is generally 50,000+ hours until they degrade to half intensity at their rated voltage. Reducing the voltage (dimming) extends the half-life even more since the LEDs run cooler.

-musicman65
 

Mute

The Tuner mode can be configured to mute the signal. Tuner mode is also accessible by foot switch and MIDI Control Change

Tuner select and mute is MIDI Control Change # 31.

-burkhard
 


Tone Controls in the Profiler

Output EQ

  • Bass Shelf: 150 Hz (steep)
  • Mid Peak: 600 Hz
  • Treble Shelf: 2400 Hz
  • Presence Shelf: 10000 Hz

Amp Tonestack

The Tonestack (EQ in the Stack) controls work differently than the Output EQ and their action is softer. There is interaction between the controls, so there are no defined frequencies to specify. For more info, see EQ Slot.

Ground switch

Cutting ground loops by the switches can prevent hum and hiss. One output should always have the ground not lifted tho, to give the Profiler a solid ground. A so called "ground lift switch" is actually not made for "lifting the ground", but for cutting a ground loop. A ground loop exists when two or more devices are grounded to the wall outlet and have their grounds connected as well by the audio cables. This creates a large ring of metal and acts like an electric coil. It can catch hum like the pickup coils of your guitar do. But it can also catch noise from computer devices, too. Often it is enough to lift one output to cut into this loop. The Profiler itself is not grounded by the power cable, so it requires one (but not more) ground connections by an output or input.

Practically, you can keep all the ground buttons off, except one. This one must necessarily be related to a device (in input or output) which is properly grounded by its power cable.

-ckemper
 


True Bypass

Q: If I connect my piezo pickup directly to the Eventide and then out from Eventide to my EV SX100 active speakers I get a fantastic acoustic sound. If I first connect the guitar to theKPA, and out from Profiler to Eventide I lose the brilliant sound even if I disable Stomps, Stack and Effects. I thought that should be the same as total bypass but it seems not.

A: If you use the Direct out to connect the Profiler to the Eventide you will get back your sound and have no need to bypass anything on the Profiler.

Wet\Dry\Wet

From FW 1.5.0, the Profiler allows wet\dry\wet. This means that you can output three distinct signals: a couple carrying a stereo, effected information, and a mono dry signal. This function, largely used on stage and in studio, allows for example to record a stereo effected signal and an unprocessed mono signal for a later reamping or further processing. Or, to reinforce a stereo, heavily distorted and compressed signal with the clean guitar voice for more clarity and attach. Just press Master; on the first page change Monitor Out (or Direct Out) to Stack: that will be your dry signal. One thing I have dabbled with is to setup the S/PDIF to carry the DI signal and the rig signal up to stack (setting Git /stack). The main out is set to carry just the wet delay and reverb (setting surprisingly Delay / reverb wet). This way I can record the dry rig and the DI (in case I would like to reamp) via S/PDIF and still have the stereo delay and reverb monitored via the analog inputs of my audio interface while recording. You could of course record the delay and/or reverb on a separate stereo track so later on you could set the level of those in relation to the dry sound while mixing - this is pretty cool. I mainly use delays and reverbs on my DAW but this is fun as the delays and reverbs of Profiler sound really good.


Tuner

The range of the Profiler tuner is OK with a 9-string (F# - A) guitar, I have no problem tuning it.

You can set it to mute (tuner settings). The little three LED tuner (just above chicken head knob...) is also usable.

Q: I'm always afraid to switch the knob accidentally one step too further and shut down the whole unit, eeeks! I hope the upcoming Profiler ground controller will come out soon and fix that problem. A: You can switch it via MIDI via any pedalboard, so you don't need to touch the chickenhead on stage :)

We have introduced the countdown animation in order to prevent accidentally switching off when trying to switch into Tuner mode. During the countdown you just need to switch the chickenhead into Tuner mode in order to avoid shutdown.

-burkhard
 

The LEDs on the tuner knob are actually a real time tuner, you don't need to go into the tuner menu.


How much memory ?

Unlike most devices in this category, that have a fixed number of banks and patches, the Profiler has a total shared memory design. This means that, as features increase, the memory footprint grows and the remaining amount of rig storage decreases. Still, the Profiler can handle by far more rigs than the other devices: it originally held over 2000 by some users testimonies, and with FW 1.6 some users still have 1300. A certain amount of free memory is needed for firmware upgrade operations. This means that, if you have currently loaded tons of rigs, the RAM could not be sufficient for upgrading; so backup, remove some rigs, upgrade, restore. Read the instructions coming with each FW release to check whether you’re over the advised limit. OTOH, after upgrading you can generally restore your rig set, unless the requested amount of memory exceeds what’s available.

Planned future features might increase the size of rig files. With less than 1000 rigs in Browse pool you are on the safe side and already prepared for the future. Be aware, that the boot time is also depending on the number of rigs in Browse Pool.

Since firmware 2.0 Performance Mode is available and offers additional space for up to 625 rigs (125 Performances 5 Slots each):

1000 rigs in Browse pool + 625 in Performance Mode = 1625 rigs overall.


Using Alternative Input (FW 1.6) for a Guitar

The new Alternative input is low-impedance and balanced. But it’s possible to connect a second guitar in it.

My electric guitar is also equipped with a piezo pickup. Each signal, magnetic an piezo, has its own cable. So it's like having two guitars at the same time. I run the magnetic signal straight in the front input. The piezo signal goes through a buffer (I use a Lehle Sunday Driver XLR for that) to lower the impedance first, then into the return input of the Profiler. When you activate the mono loop in the Stomps section, you can add your second guitar to the signal of the first guitar - from 0 to 100 percent. Sounds really great.

-guitarrenteufel
 

Q: I want to use my wireless system and want to know is it possible to use the rear input jack as a guitar input?

A': ckemper - The rear input has a bit higher noise level, this is why we don't provide this option.


Aux In

Apart from mixing external stereo sources (such as backtracks, drum machines and the like), the Aux In function can be used as a permanent Stereo Fx loop. Even with an effect in the both the X and Mod slots (and active), the external device is in play. it's kind of cool, since I have an active stereo loop and can still use both the X and Mod slots with whatever I choose.

-zappledan
 

Check the new Aux input volume feature. If it’s not set to 0 then it will mix whatever is in the loop return. When the stereo loop is enabled, it overrides the aux loop and inserts the loop return in whatever slot you have it setup. When stereo loop is off, aux input takes over if its volume is not 0.

-musicman65
 

So here's what I found. If you set the Aux In volume above zero, then anything plugged into that slot will come through your mix. It's just the one input, so won't be stereo. If you're using a stereo loop, then you really need to set the aux in volume to zero, or when you attempt to turn off the stereo loop you'll still get half of it. This could still be used to advantage, however. If you have a stomp effect you want to put after the stack, set it up as though it's a mono loop, using the aux in. Set the aux in volume appropriately, then control the effect from the stomp itself. This will leave you both the X and MOD selections within the Profiler.

-zappledan
 


USB Audio

USB audio is not planned, as this would require the Profiler to be the sole audio interface for your DAW.

Remember: you can only use one audio interface on your DAW without hassle. And we assume that you all own a more appropriate audio interface. That is why we recommend to use S/PDIF in combination with an audio interface.

-ckemper