MartinDorr

If you plug an anlog signal into the DT effects return you have no DT Master control. If you link to the DT via L6 Link or via the normal Guitar Input and AD conversion you end up in the DT DSP and even if you select no amp model you exit via DT Master controlled DA conversion (optionally sent to effect send). The most flexible way of doing this is to setup a dual path tone with the power amp selection in HD path A and muting path A in the mixer. HD path B is used to setup an effects only, or a possibly a different (pre)-amp model. That is interesting! Are you saying there is a MIDI command for the DT25 (same as for DT50) or do you rely on a known side effect of selecting selective preamps that boost the DT25 signal level to engage the DT power amp setting?

As innovine said above what matters are really just 2 things: 2) The tube effect comes into play as overall volume goes up., and 2) If you crank the Channel Volume, Mixer gain (and Pan), and/or Pod Master w/o regard to peak signal levels you will impact the tone delivered to the DT and not just raise volume to get more DT tube effect. I am not saying the former is bad and the latter is good. Just be aware that both exist and may need to be controlled to get the result you are looking for. How you use the individual dials is really up to you and primarily driven by self-imposed rules designed to simplify your personal tone creation. My primary approach is this: Set the DT Master to 3 o'clock. I get the most 'tube' out of it as far as I can tell. Other DTs may be different. Check for the likely optimal point by looking for minimal difference between peak and RMS output levels. While we're at the DT, I am thinking of adding a graphic EQ to my DT effects loop to better adjust to room accoustics (no HD parametric EQ when using L6 Link). Use HD Master to adjust to venue volume needs (I end up with about 10-11 o'clock at home to give you a ballpark) Use single path modeling of amps and effects on HD path B! Pan path B center in the mixer Use path A with a preamp model to select DT power amp and controls only! Mute path A in mixer. This works equally well for effect only, preamp and power amp model tones in path B and has other advantages (see attached file). Move path B models into A if you run out of DSP and don't need (or can't afford) the extra DT power amp control. Adjust guitar pickup height or volume so that it does not produce a peak HD input signal significantly above -12dBFS Adjust first effect so that it does produce an HD internal output signal at around -12dBFS peak Adjust HD effects and amp model chain so that no intermediate signal changes tone volume (check RMS levels if you measure), i.e., if your dial Drive up bring your gain or channel volume down I use my mixer at the end of the model chain with 0dB gain for my quietest DT power power amp selection (a Class I, AB amp). Set mixer to lower gain for all other power amp types to balance tone volume (see attached file for starting points) I am sure there are a few other ways to get a handle on this and that the above will fail to produce all the results you are looking for. I usually start like this because it allows me to change power amps, venue, or even model elements and only change 1 parameter to keep all tones balanced volume wise. DT25 Power Amp Parameters.pdf

I use USB to a MAC running an Izotope high resolution meters (I beleieve there is also some free SW you can get to just measure peak and RMS levels). I also use a Faber SignalScopePro App on an iPhone and iPad and a small USB AD interface from Behringer (UAD-something). You don't need the latter for speaker measurements. You also don't need to calibrate your mic/SPL levels if you are just after relative differences. Let me know if you want to repeat the measurements that show that channel volume has no tone impact as long as peak level stays at or below -12dBFS range. It takes some prepping using a simple HD tone setup, recording a small loop, and taking a series of measurements a couple of times.

Just adding programmable MIDI transfer option to L6 Link would go a long way. Being able to update FW wo MIDI or saving control changes made on the DT within Helix is not crucial for my needs. Voted for improvements too.

For what it's worth ... it looks like the Sweetwater demo unit had the following guitar and bass amps: 8 Guitar amps: WhoWatt 100, Soup Pro, Stone Age 185, Tweed Blues Nrm + Brt, US Small Tweed, US Deluxe Nrm + Vib 7 Bass amps: Tuckn' Go, SV Beast Nrm + Brt, Cali Bass, Cali 400 Ch1 + Ch2, G Cougar 800

I thought i saw a power switch right under the power cable receptacle - maybe wishful thinking

I get maximum 'tube effect' from my DT25 when the DT Master Volume is set at 3pm (not max) and thus I leave that setting constant for any venue or tone. I use HD Master Volume to adjust volume to venue. I use Channel Volume on HD to set peak amp model signal level (measured via USB) at about -12dBFS to stay away from model soft clipping/compression/distortio From measurements I concluded that Channel volume changes that results in output levels below the -12dBFS peak are tone neutral. Changes that cause output to be higher will impact tone, which you may use to your advantage if you are looking for a bit of compression or distortion. It will get nasty though (for my taste) if you get in the -3dBFS range. Martin

I believe the MIDI adjustments also change what the HD selects as reverb, mic model for XLR out, and power amp config when picking Type I-IV, which are just program slots in the DT. While I have not checked whether the MIDI driven configuration in the DT acts like the power amp driven selection in the HD, I suspect it does. If true, the amp model selected in the DT may have impact on amplification level and possibly tone associated with specific amps rather than just their feedback loop configuration. I am attaching a PDF that explains how to get this effect with an HD using path A and B. I think if the DT is MIDI configured the same might be working with just a single amp/path HD tone and a DT configured for specific amps in program slots I-IV. I have to say though that these subtleties may not be worth the trouble you have to go through to check and use them. Good luck and let me know if my guessing does not make sense, Martin DT25 Power Amp Parameters.pdf

The -12dBFS peak level limit is probably originating from me although I heave seen other references to a limit in that range (I did not track down where they came from). It's primarily my opinion based on preamp and EQ, boost, and compressor model measurements. In practice, the measurements indicate that there is some compression and/or soft clipping happening when your peak levels hit the -12dB to -9dB range. Every model I ever checked (but there are 3x more than what I checked) showed this behavior. The signs of this effect are that if you increase your input level by say 6dB the output does not increase by the same amount (it's less) and the RMS level goes up relative to peak level output (the signal distortion content goes up). You probably won't hear it at peaks below -9dB, I usually hear it (may be subjective now that i know i can measure it) somewhere between -9 and -6dB and it usually becomes nasty when your peaks get into the -3dB range. If you stay with your peaks below the -12 to -9dB range, amp channel volume and any other plain gain changing controls just shift the signal level up or down without changing tone. That said, there is nothing that should stop you from utilizing a little soft clipping / compression when you need that signal level (e.g., to produce louder output). Just be aware that it exists (at least from my point of view). Hope this helps you out, Martin

I measured peak and RMS signal levels coming out of my DT25 with a clean input tone and got minimum difference between peak and RMS levels when I set my DT at 3pm (not max at around 5pm what I would have expected). I believe this indicates that this is a dial position where the DT tubes add the most harmonic distortion to the clean input signal. Since I did these measurements I have my DT Master parked at 3pm and control Volume strictly with HD Master. A setting of HD Master at 10-11pm should get you reasonable bed room level volume. When you play out adjust HD Master to your needs. You maty want to consider adding a graphic EQ pedal to your DT effects loop to further adjust tone globally to your venue. The new global EQ of the HD FW update does not work if you use Line 6 Link to connect to the DT. As said above use amp channel volume to balance amp model signal output levels (I use a -12dBFS peak threshold to keep a healthy signal but do not get into soft clipping range of models). You can use USB and a DAW to check peaks). Finally, you need to deal with DT amplification changes when you switch between different amp configurations (type I-IV). I do those with the mixer gain control. I added a 2 pager I put together with some info on how to put the mixer in the right ball park and then fine tune by ear. Good luck, Martin DT25 Power Amp Parameters.pdf

I saw that a long time ago. Did not think it was a bug as I look at Drive controlling the amp tone impacting portion of the real amp's channel Volume pot (versus HD Channel Volume controlling tone neutral volume unless you exceed -12dBFS peak output levels). If you put that Volume pot at 0 the real amp it won't give you any output either ;-) ... and things change when you put any of the 2 HD Drive dials at say 1%, if I remember right

Check out the DT's MIDI implementation (download from Line 6 documentation page) to get a feel what you can do with the DT by itself (assuming you have latest DT FW). The Type I-IV switch selects an amp configuration, which is made up of a preamp model, a power amp configuration, reverb and a couple other parameters (see MIDI). Bypassing the preamp does not bypass the power amp config (or the MIC model for the XLR output). Watch out for LVM, if you turn it on you are running a power amp model through a 'neutral' power amp stage and not the normal power amp stage. Happy reading and experimenting, Martin

Start with an empty dual amp tone structure (or turn all models off) and only enable the very first effect with neutral tone/gain settings. Set both mixer paths to center, 0 gain. Play your guitar and raise your first effect's gain to get maximum output level w/o ANY distortion/compression/soft clipping. Ideal would be measuring the USB or SPDIF output level and making sure your peak level does not exceed -12dBFS. You can raise this limit a little for clean target tones and maybe 3-4dB for higher gain tones if you feel you do not get enough output volume. If you do not have any effect before the amps, add a Mid focus EQ with tone neutral setting and adjust its gain untill you hit the limit. In some cases your guitar level may be just right or you may need to lower your guitar volume pot (or even consider lowering your PUs) to stay below the peak limit! Once you have that baseline you have a very healthy input signal to work with in subsequent modelling stages and a target volume to adjust model gain or amp channel volume such that the perceived output level never changes as you add, change or remove models and adjust settings. (Never is too strong a word here; a couple dB up is fine, especially when you target higher gain tones, but who wants to measure all the time or keep track of that by ear). As previous posters indicated, I also think it's essential to keep things as simple as possible and explore your options at least initially with just the amp models (all parameters, cabs, and mics. Next step would be add drive and/or distortion effects to get closer (always w/o changing perceived volume). And if that does not do enough, try removing or emphasizing frequencies with EQs (again w/o changing volume). Good luck, enjoy the ride ;-), and sample a couple more opinions ... Martin

When you use an HD, connect via L6 Link, and have an amp model in path A, the DT bypasses its preamp models and just runs the power amp model you selected (default or changed via MIDI). I think to rember that the DT comes up in the last used mode you selected when it was turned off. Don't know whether it just picks the associated preamp (w/o changing any power amp config changes to default) when you switch from Line6 Link to guitar direct. Just try it out. Maybe it helps to understand that the Channel A/B and Type I/II/II/IV switches are really just schwitches to select 2 groups of 4 amplification programs. By default (or after a DT reset) the 4 programs for both channels A and B are associated with 4 pre-defined Amps (a preamp selection, a power amp feedback loop type, a power amp class A/B selection and tube pentode/triode selection). With the latest DT FW you can change this default setup including a couple other things like reverb type or the MIC model for the DT direct out. In orther words, if go direct into the DT, the Type switch selects one of 4 amps (both preamp and power amp feed back loop) and you can use the other switches to divert from the defaults (and the tone controls to adjust the preamp model tone stack and reverb level). On the other hand if go via Line6 Link, all the above applies, but the preamp model is bypassed (but not the reverb) if you have an Amp in path A of the HD. If you have no Amp in path A, the HD switches the DT to Channel B and the DT uses whatever amp configuration you have selected using the type switch on the DT (last time yo setup channel B). There are some more hidden DT features you can tap into if its worthwhile to you, e.g., you can select a preamp in HD path A and then mute its output in the mixer. Then you can route your guitar signal (with or w/o effects or amp models to the DT via path B and hear the pure power amp tone (assuming no HD models) associated with the preamp selected in path A. I attached a 2-pager explaining this and 2 surprising discoveries in more detail. Hope this helps, Martin DT25 Power Amp Parameters.pdf

I have seen a 3dB drop when playing back a recorded loop compared to the normal play through level, but that's not half the volume (that would require a 9dB drop for most people). I could never get to the bottom of when it happens, but it probably has something to do with summing or not summing path A and B. It really only mattered when i was doing some measurements with a loop and the loop not reflecting the normal guitar level. Whenever I use the loop in practice to solo on top I end up turning the loop volume down a bit anyway. Sounds though as a you have a different problem if its really half and the loop playback levels are all max. I have an HD500 and that may be acting a bit different than the Bean . Maybe somebody else has seen this before.

You can use the preamp models to go into an existing power amp effects return and replacethe existing power amps preamp. You can obviously also do this with the full amp models. It just needs to work for you. No hard rules ...

My gut feel is that L6 is working on an HD line or HD500X successor. While really nice to get our hands on, I think the model packs are just a bridge stilling our hunger for 'more'. I expect FireHawk-like user IF with HD modelling and increased DSP power coming up next.

Load an app that measures SPL peak and RMS onto your phone, pad, or computer. Should show any differences as they creep in w/o the subjective 'us' listening and believeing to hear something. Does not need to be a fancy app or be calibrated. You are only looking for change.

Great, really appreciate this work. One question: Have you ever measured whether the D/A conversion for the HD's analog outputs have any significant impact to the signals when compared to SPDIF? In regard to the need to use a really low input signal to keep the HD amps and models in a linear operation mode I found that if I reduce Channel Volume so that peak signal levels stay below -12dBFS, all HD models I ever measured (all preamps and somme EQs and compresser/boost models) stay in the linear operation range. If peak signals get into the -9dBFS and higher range the models start to compress, soft clip, and finally distort. For peak model output signal levels starting significantly above -12dBFS the increasing of gain on Channel volume (or Master Volume, mixer, and/or volume pedal) will change tone rather than just signal level. Not sure you can confirm or have observed this effect (I believe I saw reduced level increases in your EQ curves in the higher signal level ranges). Assuming this observation is correct I think it can be used to raise the input signal to a level that more closely reflects what a guitar would provide (and changing to channel volume so that the amp stays in linear operation range where HD signal level adjustment dials do not change tone). Martin

I would not be surprised if it is driven by the Workbench SW update and making the JTV FW match some feature they wanted to better support both the the Variax Standard and the JTVs. But that being said, i would not want to touch it either until we know what it's for.

Very nice and extensive work. It's appreciated, and, as you said, there are some interresting observations in these base lines already. You did not mention that Cab models where off, but I assume you did to keep the Cab out of the amp measurements. Also, If i understood your description right, you dialed in Drive to get to 1% THD. Did you do this independently for pre and full amp measurements or not, and did you by chance record the Drive value you needed? I think it would be interesting to get those numbers of each amp model as well. Thanks again for all the work you're putting into this. Martin

Yep, that's my basic plan of attack. In practice I have never seen digital clipping that actually cuts off waveforms when a signal comes out of the HD. It is really a gradual effect similar to the soft clipping feature in some analog preamps. If you intentionally make it happen you will hardly hear anything from -12dB up to -9dB or bit higher. The only thing you might detect is a smaller difference between peak and RMS signal levels, i.e., a sign of harmonic distorition getting added. If you push the level higher you will hear clear compression followed by mild and then severe distortion, all below 0dBFS. Try the Studio EQ for example. It does not color the tone, but it sure changes if you get up into the -6dB range output leel and higher. That said, some downloadable tones may actually use this compression/distorion of an effect or the amp model somewhere in the signal chain and the originator came up with a result he liked. Its no good to try and 'fix' the tone because some compression/distortion will be lost and need to replaced with an explicit effect in the path ... usually not worth the trouble unless someone is rebuilding a tone from scratch and just borrows ideas from the original. Good luck playing with this. If you come in at a healthy level amp Drive and and similar effect parameters work amazingly well even though you use lower model output gains (channel volume on amps) to stay at the healthy level and keep peaks from hitting above -12dBFS. If your tones are on the high gain side you will find that peaks will come down if you keep the subjective volume constant as you add effects to the chain. So if you are after high output volumes and play only heavily distrted sounds you could put your initial peak signal level say 3 dB higher (getting a little compressed) and still stay below the -12dB peak at the very end of you chain when you may want clean delays or reverbs.

All HD volume or output gain controls (except MASTER) should be primarily used to keep you HD internal signals at a healthy level. My take on 'healthy' is that I avoid -12dBFS peaks between models (measured via USB). I did quite of bit of measuring before coming to that conclusion and it is driven by noticing that all models I ever checked seem to start soft compression/clipping somewhere between -12 and -9dBFS. Now, I am not saying that you can't use this effect to your advantage. I am just saying that if you use channel volume or output gain dials to adjust signal levels between models the effect of those dials will change tone (and not just level) if your peaks exceed -12dBFS by more than a few dB. As said earlier, MASTER is most useful to adjust your volume to your room. 'amsdenj' mentioned above that 'Master Volume' controls the power amp model. This is the 'MASTER' dial in the AMP PARAMETERS section of the HD edit SW or the soft dial 1 controlling MASTER of the 2/5 AMP:EDIT menu on the HD itself. Don't confuse it with the physical 'MASTER' volume dial to the left of the HD pedal. The dedicated MASTER knob just changes signal levels as far as I can tell. While not as sure about the mixer, I think the mixer seems to do the same on a per path basis. Be careful though with the mixer because in many tone setups there are effects after the mixer and if you hit the mixer with a healthy level of -12dBFS and set gain to anything much above +3dB you will cause soft compression / clipping in the effects after the mixer. A good practice to get a solid starting point is to measure the level of your guitar input w/o any effect and amp models with mixer a 0dB gain. Add an initial effect like studio EQ to rais the level so that peaks stay below -12dBFS. Add effects and amps step by step while maintaining output level.

I heard Yamaha DXR10s are another good voice, but I had no chance to compare yet and could not find a review comparing the l6's with the DXRs.

Great thread. Curious to see what's coming. Too novice to contribute ;-(.