Posts by easstudios

I actually recorded the Kemper via spdif - it seemed a fairer test to keep the ad/da consistent (and less conversions) and as everything would be used in normal circumstances. I’ve realised the way I worded the chains wasn’t the clearest, but my kemper is always hooked up by spdif (I also used it as a reamp device to keep gainstaging consistent).

I’m curious to try some more tests and work out what’s going on - I didn’t have any FX in use, but maybe I need to disengage the entire block? I could also record the analogue and digital outs simultaneously.

and I can do a test at 44.1kHz - it would be very strange if working at higher sample rates caused the kemper to work at lower ones....

and FWIW, I think all the methods included in the zip do a reasonable job at capturing what they’re supposed to. Very important to understand the gear and know what they’re strongest and weakest links are (and how to get the best useage out of them).

OK, so it looks like both the direct and studio profiles show that mirroring happening here (which isn't happening on the direct DI from the amp). These are all signals with no cabinet or IR's - I can upload screenshots of the cabinet processed files too - they are bit harder for me to gauge anything from though

Ooh that is interesting - I'd definitely like to know what's going on there as something clearly doesn't check out (I pm'd the person who made that post on GS and told him about this thread).

I just did a really quick comparison of running a DI through various chains:

Marshall JMP->Mesa V30->57->Chandler TG2->UA Apollo
Marshall JMP->React IR (on through so the cab load is consistent for all)-> UA Apollo

Kemper Direct Profile as captured from the React IR (but with the Mesa cab as the load for the amplifier)
Kemper Studio Profile of the first chain
Kemper Studio Profile of the first chain but with the cab disabled

I also made an impulse response of the mic position by deconvolving the amp DI against the mic'd signal, and included prints of any direct amp sound through the same impulse.

I've included the Kemper profiles used, as well as the impulse response of the Mesa cab, and the DI too.

They can be downloaded here: https://www.dropbox.com/s/rt0m…rq/Kemper%20Test.zip?dl=0

Photo of Amp+Cab Setup
Photo of Rack Gear Used

I've never done any spectral analysis before but I do have the standard version of RX7 so Ill see what I can do.

Quote from paults

I read it, but, I don’t think looking at a waveform is a direct indication of how the software that created it functions.

Just looking of course tells you very little, but if you do the test for yourself - you can hear the difference in the top end being different, with the direct being more accurate to a real amp. The analysis of the spectrogram just helps to explain why the sound is different (and somewhat unnatural compared to the real thing).

It does quite clearly show that the signal above 11kHz is being mirrored back rather than capturing the information in that region, which points to the sample rate being halved.

I can of course live with it (I bought a Kemper based on how it sounds which Ive always been very happy with), but knowing this information is helpful for me in that I'll be making direct profiles more often now to get the most out of my unit.

I'm assuming I'm not the only one who cares about this kind of stuff, but I also appreciate that for many its nothing to worry about. Its interesting enough to share the information and discuss IMO.

did you guys even look at the post I linked from gearslutz?

The spectrogram plot shows a clear difference between the different capture methods. One behaves like a guitar amp does above 11k, and the other does some strange frequency mirroring that can only happen in the digital realm and is not representative of what we hear in the real world.

stratdude - do you actually think that a guitar speaker can’t produce signals above 11kHz?

A guitar speaker does roll off gradually at frequencies in that range (actually rolls from about 6kHz), but there is still harmonic content up there - that’s why we can hear a difference if we add a LPF to a guitar cab once it’s recorded. It’s not like a cab doesn’t produce frequencies in that range, it’s just that they are quieter than the lower range.

FWIW, I've had some success making direct profiles of the Krank and then adding an impulse afterwards. For some reason this has yielded less error messages when profiling this particular amp.

Quote from Wheresthedug

not sure of I fully understand. Are you saying you would like to be able to profile the hard ware EQ as an active FX that could be tweaked in the Kemper? That isn’t going to be possible due to hardware and the way the profiling process works.

More along the lines of the first option - the second one is a fundamental part of how profiling or making impulses work. It would be great to have the ability to have an EQ curve impulse as an FX slot that can be bypassed or active, much like using the internal EQ but with the benefit of copying the curves from HW being used while profiling.

So recently I stumbled on this forum post from another forum. Its from an amp sim developer showing some interesting things about how the Kemper is working. It appears that it's profiling at 22.05kHz unless you are capturing a direct profile, in which case its doing it at 44.1kHz.

its quite clearly no issue and produces a satisfactory result, hence the success of the profiler. It is interesting though, that its capturing a more accurate profile (in that its capturing above 11kHz) when done direct.

It would be great to hear why this was chosen, and whether its something we'll see upgraded in the future - even if a lot of content that high is filtered out, it would be reassuring to know that it's being profiled and sampled accurately.

Recently been playing with running my hardware Neve and ISA EQ's with the Kemper and an idea popped into my head - it would be great if it was possible to capture an IR curve of the hardware EQ being used to store into the rig. Of course there's nothing wrong with the Kemper EQ's but hardware EQ's have their own quirks and behaviours and can be more immediate to use.

I think the profiles can still be saved when the error message comes up, I have a feeling that's what happened with Dan's but I can't remember 100%. I seem to recall some people running a tubescreamer before the amp and for some reason that would help too..... I'd love to know why that amp causes an issue and if its something that can be sorted properly (given how continues the Kemper's development is)....

Quote from BRYANMELTSYOFACE

I have never tried profiling a KRANK but have received that same error message with another high gain amp.

Same thing with summing 2 mics, One mic is a rich true representation, 2 Mics its much lower volume wise and not accurate. Matched phase in DAW ect

Thank You for starting this thread, Any tips for better profiling would be greatly appreciated!!!

Also has anyone tried using UAD unison mic pres for profiling? ROCKON!!!

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Yeah, the midrange of the summed mics is way off. Its almost like the usually differences between Kemper tone the mic'd one is exaggerated with 2 mics. Made a lot of profiles with UAD Unison Pre's and they work fine (using mostly external preamps now though).

So I'd already heard that Krank's can cause some issues with the profiling process - once the profiling is complete an error message appears warning against using a noise gate in the amp. Krank's don't have a noise gate anywhere in the circuit. They're essentially modded Sovtek Mig 100H's (itself a kind of modded Marshall) with better components. They have quite a distinctive attack, which I think may be a part of the problem?

Just wondering if anyone has found a way around it? I love that they're such distinctive sounding amps, would be great to be able to capture them accurately.

Also having issues when summing 2 mics. When using one mic I can get the captured profile to be almost indistinguishable from the mic. When summing 2, the differences are quite noticeable and refining doesn't really change the differences. Is there any tricks to getting this working optimally?

a plugin for hardware recall would be so handy. I’m working on different projects regularly and it would be so much more convenient to have all the relevant profiles saved within the session.

The editor will be so helpful too, it’s hard to position the kemper in a visible space in my studio and certain menu’s can be cumbersome to scroll through.

Thanks guys, appreciate the suggestions. Demo's sound promising. Keep them coming!

They don't have to be mega distorted (I'll run a sansamp/guitar amp in parallel), but something with a bit of brightness, grind and the kind of low end a loud cab makes.

Quote from DonPetersen

have you tried our Bass Rig Packs?
(see my sig)

I have! Not really found what I'm looking for in this case, although there is some cool stuff in there

Looking for some grindy bass tones, ideally big ampeg 8x10 tones. not a great amount on the rig exchange and its hard to tell from the commercial ones I've found. something akin to the bass tone on later alice in chains albums, celebrity skin (pretty sure this is a blend with a marshall guitar amp) etc.

Appreciate the response - I'll certainly inquire about the SPDIF clocking as I was surprised to notice a difference. Presumably your response above means it's not possible to make the Kemper the clock slave in the future?

Of course, it's not easy to scientifically compare different DI's to what's in the kemper - specs contribute nothing to what sounds better (ultimately opinion anyway), but it is still interesting to compare what information is available and what benefits they can possibly bring. There are many talented developers out there who I'm sure made their design choices with as much reasoning as the kemper

For my tastes, I much prefer the feel of a higher impedance input - I've always found it impossible to dial that high end brilliance/clarity back in to a sound, whearas it's very easy to scale it back afterwards once captured.

I commend you if you feel the kemper's DI outperforms all of the competition, and I truly believe you're entitled to that opinion. As long as I'm noticing a sonic improvement I'm , happy to mix and match, and pair up the right DI to guitar/bass depending on the job. It'd be great if the kemper had a way of mimicking the kind of behaviour of an MW1 where the impedance is continuously variable and cab be tuned to the specific instrument and desired tone.....

It's certainly an interesting topic.

Quote

I don't use the digital I/O at all, but it doesn't surprise me that when you use the Kemper as a master, your other convertors don't quite sound as good as they may when you use higher-end and dedicated clock masters. This is, after all, is why the Big Bens of the world exist; there's been a market for these things for eons simply because proprietary (in-built) clocks of our various outboard devices aren't specified to perform the task at the cutting-edge of technological possibility. They're generally there for their utility - to be used in a pinch, but certainly not as permanent solutions in pro setups.

This wouldn't be an issue at all if it were possible to set the Kemper's clock to an external source. Sure, Big Ben's/etc exist but if the Kemper's clock is causing noticeable issues to my system, then it'd be nice to have the option to sync it somewhere else. FWIW, I'm not using any kind of dedicated outboard clock, and this is the only time I've noticed a perceivable drop in quality when using digital devices (compared against "cheapish" units such as MOTU 896HD/Mackie Onyx/Focusrite Forte). It's not so much of an issue when only using the Kemper by itself - more of an issue when recording multiple instruments at once, or working at different sample rates. With the most recent generations of converters, the benefits of external clocking has reduced fairly considerably (the Big Ben for instance has been discontinued). If the Kemper isn't equipped with a clock that compares favourably, even to standard interface clocks, then it would make a lot of sense to be able to run the Kemper as a slave to whatever the best sounding option is.

Quote

As for the DI thing, which was your main focus, I suspect that the plain-jane feedthru (guitar-level) is for all intents and purposes uncoloured

I'm curious to where the "uncoloured" assumption comes from? Connecting a guitar to any kind of "load" is going to affect how the pickups react - if the impedance is too low, the high end will disappear (good luck getting that information back). Likewise, all DI's have a frequency response, noise/THD behaviours, dynamic range etc. These values are not provided by Kemper so "uncoloured" is baseless without some kind of reference point. It certainly fares better to me than my Little Labs Redeye did (lower impedance than the Kemper, caused loading to the pickups and a lack of high frequency information). I've also used DI's that cause the high end to become distorted and lack clarity resulting in noise from around 3k upwards - again the Kemper
doesn't seem to suffer from this. Furthermore, the specs given from Kemper (although by no means bad) compare less favourably to other gear; if you deem the Kemper to be uncoloured, then by definition choosing equipment with superior specifications will provide even less colouring.

What I have experienced, is compared to DI's with a higher impedance than the Kemper (2.2MOhm upwards, such as http://rupertneve.com/products/rndi/#tech-specs , http://www.creationaudiolabs.com/#!mw1studiotool/cp99 , http://www.uaudio.com/interfaces/apollo.html , etc), the Kemper has less information in the high end (a warmer tone). This may not be an issue with lower output pickups or if the intended tone is on the warmer side. When capturing my DI's, I'm looking to capture as much of the sound as possible rather than losing anything.

Now as far as splitting your signal goes, a good DI box is critical here as its impossible not to affect the impedance - hopefully you have the opportunity to try a few different ones (and even compare to the Kemper's) so you can experience what I'm talking about. The MW1, for example offers a variable impedance on input and output which seems like it would be great for tuning the impedance to the desired guitar sound. The Rupert Neve DI has the ability to also be used a speaker load which obviously has its benefits for making direct profiles. I'm currently going directly into the Apollo DI and then in and out of the Kemper which has the benefits of only one A/D stage, and also keeps my analogue inputs free for other things.

Now, I'm sure we can agree that its best to not blindly assume that the Kemper (or any piece of gear) is the absolute benchmark in DI's, A/D conversion, clocking, etc. I'm not saying it categorically isn't, but based on the specs they've provided, it certainly doesn't stack up as well as other equipment. That's not to say that if all I had to work with was the Kemper, I wouldn't just get on with it, but given the other equipment available to me its worth exploring various options and working with the best sounding AND most convenient workflow. I started this thread as I was curious if there was people out there (say with one of the DI's I mentioned, or equivalent) who had experienced something similar to me, and I'm still interested in how others may be incorporating such equipment in their set up.

Quote from Monkey_Man

This has nothing to do with the D/A convertors used for the line outs 'though, does it?

I thought this would relate to the digital I/O only. Am I wrong?

Well the "clocking" aspect of the Kemper will be the same regardless of which outputs you are actually using as the processing inside the kemper is all digital (and the Kemper has to be the master clock at all times). Changing my interface's clock from master to slave means my D/A sounds worse while the Kemper is set as the master (fine temporarily for tracking, as long as I'm not recording anything else at the same time). I have no idea what the quality of the built in converters are (these have improved a lot/become much cheaper over the last few years). Without any tested figures and no way of knowing for sure, I'm happier doing to A/D and D/A conversions elsewhere....

I don't doubt that the built in DI input on the kemper is good enough for most people, in most situations. That said, I'm also not naive enough to believe that the Kemper is the first ever unit to create a PERFECT DI box, an entirely linear gain stage, and amazing A/D conversion as well as its groundbreaking technology at a price far cheaper than anything else out there. The loss in fidelity when changing it to the master clock immediately makes me weary of its conversion quality.

I'm sure it has been designed to be as neutral and uncoloured as possible, as is the case with a lot (but not all) DI boxes/preamps/converters. Without some clinical way of testing each section of the Kemper's input, its entirely inaccurate to claim the Kemper "has no signature sound" or is "more authentic" then every other piece of equipment out there - not least as there is no defined reference point for a perfect behaviour. Furthermore, with the given specs, I don't possibly believe the Kemper's DI is outperforming gear with superior specs.

Just to use the Apollo's DI as a comparison:

The Kemper has an input impedance of 1MΩ vs Apollo 2.2MΩ
The Kemper has a dynamic range of ">108dB" vs Apollo 117dB

There is no values given for the Kemper's THD+Noise so its not possible to compare these.

Something like this (http://rupertneve.com/products/rndi/#tech-specs) has far better specs than what I'm using, and there are also far better A/D converters out there. Could they only offer an improvement in sound by somehow "colouring" the sound? I'd be interested to know how these values above constitute the Kemper behaving more accurately than other equipment. If the Kemper sounds good enough as-is to you, that's absolutely fine. If you have compared it against other equipment (cleaner/more character/whatever), and ALWAYS prefer the sound of the Kemper, thats fine too. But its wrong to blindly assume the Kemper's input is somehow more authentic or has no signature sound.

All I'd suggest, is if people have the means, to try alternative DI's/conversion, as based on my experience, there is a notable difference (and in my opinion improvement) by combining it with other gear.