The tone stack on a mesa boogie for example is between stage 2 and 3 in the preamp section with two amplification stages after. I gather this was based on the Fender circuit (the Boogie was originally a hotrodded Fender Princeton and was played live and in the studio by Carlos Santana in 1975). The tone stack is passive and can cut amplitude of the signal by 20 dB so you need another gain stage to boost the signal back up to a suitable level to drive the power amp.
Posts by Antipodes
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According to the changelog OS 9.0.0 requires Rig Manager iOS 1.3.8. That version should appear in Apple's app store soon.
In any case we don't expect any freeze, if you do try with an older revision. It just doesn't connect.
Is the Android (beta I assume) version due anytime soon? I would be happy to try it.
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In all this discussion, it is important to remember that the Kemper "gain" knob (as things currently operate) pushes the amp further up its gain curve but maintains volume overall - it therefore does not behave like the volume control on the amp - which both boosts level and gain behaviour at the same time (so quiet clean sound and earsplitting distortion sound) - but as a special version of that control with automatic level compensation. This is a great feature of the KPA design which does not get discussed a lot.
I expect that the new gain control in Liquid Mode will remain level compensated, it will just follow more closely the gain settings on the volume knob on the actual amp.
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Tube amp preamps typically have a cascade design where a succession of 12AX7 or similar tubes boost the signal and pass it on to the next stage which boosts it further. The "volume" or "gain" control is just a potentiometer which wastes some proportion of the signal to ground before the wipe of the pot passes the signal on to the next stage.
A "pot" is just like your guitar volume control, a variable resistor with the incoming signal connected to the top of the resistor, the bottom connected to ground and the output taken from the wipe, the position of which can be adjusted with the knob to take an adjustable output level anywhere from full amplitude to zero amplitude. If the "volume" or "gain" pot is up full, then the wipe is connected directly to the input and the pot is more or less out of the circuit in terms of level control - the coupling cap feeding the signal to the gain pot and the resistance of the pot still comprise an RC filter which functions as a one pole high pass filter. That "up full" setting is what you get in the absence of a gain pot at that location - so if there is no additional gain pot the thing is wired to run the amplification through the cascade flat out.
Amps with multiple gain, volume, master volume pots like mesa boogie designs just have more of these pots between the gain stages so that the amount of distortion can be fine tuned at multiple points in the sequence.
Amps with just one gain control typically have it early in the sequence of gain stages (eg directly after the first gain stage which is straight after the input) and, after that gain/volume control, the signal from each half-tube gain stage goes either directly into the next gain stage or on to the tone stack (which typically cuts the signal amplitude quite a bit and therefore another gain stage is needed to boost it back up again).
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Just on tonestacks: it is a mistake to think that all the pots at 12 o'clock or "5" on a standard BMTP set of tone controls corresponds to a "flat" response like a graphic Eq with all the sliders midway up. There is a lot of variation in circuit values - and the result is that some are naturally scooped and need the M control at 10 to approximate a flat response and some are quite treble tilted and will never get the bass level anywhere near the same level as the mids and treble. The design of the bass and treble filters is highly variable between different variations on the basic designs and there are often multiple toneshaping filters in the signal path - examining the various Marshall circuits and you will see why the whole response typically tilts to the treble end.
I recently read a discussion article on tonestacks that was linked to either here or at TGP which pointed out that the Fender Shimmer relates to the phase relationships induced by the filters in the tone stack and that these do not show up in the typical tonestack analysis software.
I would expect that CK and his fellow developers are aware of the intricacies of tone stacks and will have applied them as part of emulating amps in software.
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Taking Cliff's statements about his patent at face value is unwise. I guess if Apple can "patent" a rectangle with rounded corners you can patent anything in the US. Actually enforcing that patent can be problematic as it is easy to demonstrate prior art.
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I think it would go both ways, like a full audio interface.
In any case, you would have the option of direct monitoring your guitar before it goes into the computer. But I assume you are asking about audio coming out of the computer, like the other tracks playing in your DAW.
In the video, we saw four channels going from the Kemper into the computer. That would be an improvement in itself, as S/PDIF only provides two input channels so you can't combine a stereo signal with an additional DI signal. With four channels of USB audio, you wouldn't have to choose anymore.
But Christoph Kemper also said in the video he uses the Kemper for recreational listening now, taking advantage of its excellent analog outputs. That would suggest the USB connection is able to receive and convert digital audio from a computer. So, both ways!
All speculation of course, going from the video! 😀
I would expect the same - this two way traffic on the USB interface is necessary for ReAmping via USB of course.
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Being an upside for all the Toaster and Rack Owners. Might be more fiddly for the stage owners to get access to this new feature.
Is USB recording unilateral or am I able to use the high end headphone out of the KPA whilst recording? Problem is I do not own monitors so my focusrite would still be needed anyway and therefore I still could carry on using spidf…The KPA routes audio out from multiple outputs simultaneously - from the main XLRs, from the TS outputs, from SPDIF, from the headphone out and from the send(s) and you can set what volume each of these outputs gets and which mix in the Output section. I would expect that the USB output will just be additional digital outputs like SPDIF and you will be able to set what signals are sent and what levels.
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Big players like RCA and Edison claimed that inventors had stolen "their" work. So the actual inventors had a hell of a time fighting the deep pockets on major industry players and plenty of them died broke, miserable and unrewarded for their work. If you know how the IT industry has worked, big players like MS stole all kinds of stuff from other developers (eg Disk Compression and activatable licences for trial versions of applications).
These developers approached large established companies and said, here we have this invention - guys at the head of the companies approached often said stuff like - ha ha, we don't believe that is even possible - and eventually released the feature as part of a new version with no payment or acknowledgement. The inventors had to spend years in the courts to get paid if ever. In the film industry, screenwriters approach big studios with scripts, the studio passes, then some time later releases a film with all the ideas from the script (eg T2). Most instances like this it is who has the biggest budget for fight the court cases and the subsequent appeals.
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The history of patents in the US is kind of a horror show. It includes the Wright Brothers patenting powered flight which completely stalled the development of aviation in the US for years and years (you had to pay a licence fee to them if you built any aircraft) until some way into WW1 when the military woke up to the fact that other nations were way ahead on this essential technology and the govt decided all patents on flying machines were now void. Then there were the patents on all the basic things we take for granted - electric light, radio, TV etc which like the Wright bros thing were often just used for patent trolling: - ie we, the patent owners, don't actually make anything at all that anyone could buy, we just want to operate like parasites on anyone that does make anything and anyone who wants to buy that thing.
It was good to see Ed Sheeran on TV tonight, after his victory in the copyright lawsuit against him, rubbishing the idea that basic song elements could be used in copyright infringement suits - like claiming copyright on the the alphabet or the colour blue - and I might add, especially by people other than the composer allegedly being plagiarised ( check out the Men At Work copyright suit if you want to see an example of how that plays out).
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Yea, that thread is something special.
You ain't kidding. Buahaha. Drew from FX is going to town about how much the KPA sucks in his own inimitable style. Others are on the old "I'd rather push my Fat Bob than ride a Rice Burner" trip. The term fair weather communist was invoked. A joy to behold.
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Here is the patent that was so violently infringed - presumably without buying it dinner first:
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the output sources for USB are the same as for the other outputs.
I saw 4 output channels (2 stereo pairs) - is that the limit of the available channels? Does the Kemper also support using the MIDI input and output as MIDI input and output for the computer on the end of the USB connection - eg could you connect a MIDI device like a keyboard? That would make the KPA both an audio and MIDI interface.
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This will give the alternative capture platforms something to chew on. The ability to tweak a capture/profile is undeniably useful in the hands of a guitarist. The tonestack modelling thing has often been discussed as desirable/the next step but seemed like a big ask technically - almost far fetched. Kemper have done it apparently - and patented it too! Quite possibly other approaches that are more AI based will get around that patent but the whole game is moving on to a new level if this is the new standard.
This whole suite of announcements - profiling from Rig Manager, USB audio, Android support for the Editor - very impressive indeed and the whole show works on the current hardware.
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Yes indeedy- mad science is the shizzle. Being able to combine any amp and any cab in the KPA offers all kinds of possibilities that aren't practical otherwise.
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Tube manufacturers supplied sample circuits which told amplifier manufacturers how to employ them - same way IC developers do today. Applications for audio preamp and power tubes were largely related to PA systems - amplifying the voices of announcers and vocalists and miced musical performances. Direct amplification of electric instruments started out by borrowing the speaker drivers and amplifier circuits from these PA systems and housing them in portable enclosures.
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That said, Kemper is not obsolete or even close. The Kemper has it's own thing that neural networks can't do, that's internal amp edits.
This is quite an important point. While the arrival of neural network techniques is going to enable lots of interesting stuff in the music sphere, I think the fact that Kemper uses a "tuned model" approach means that you can get in there and make all kinds of useful adjustments to the behaviour a profile to suit your application.
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I keep looking for release 9...
Yeah - gotta wonder what is cooking in the Kemper Kitchen.
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Startup time is also affected by how many profiles/performances/presets you have loaded.
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I gathered some time back that the amp section works with 16x oversampling to get the desired sound quality. This might explain why, despite all the FX it can run simultaneously, duplicating amps is too much for the current system. In terms of the interface you could possibly just use another soft key to alternate between the controls for AMP A and AMP B.
I would imagine some of the other processing (eg drives, filters) would also benefit from oversampling but quite possibly much of the signal path operates without needing this much more demanding processing load.
The fact that it is possible to load 8 reverbs into all the stomp and post amp FX slots without the Kemper stumbling due to excessive DSP load indicates that the signal processing and multitasking is very efficient indeed.
