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Main :: DT50/DT25

DT25 LVM question
by geppert on 2012-07-02 11:54:09.2670

Just bought a DT25 head/cab and Pod Hd 500. Just working though things.

So, with guitar plugged directly onto the DT (no Pod) , Top 1, Drive ~20% (9 o'clock), Bass-Mid-Treble- Pres 50%, No Rev, Channel Vol 100%, Master Volume 75% (3 o'clock), Top 1, Class A/B. Pentode, I get WAY MORE VOLUME in LVM as opposed to Regular mode. This makes no sense to me??

Can anyone confirm this on their DT25?

Re: DT25 LVM question
by greghall on 2012-07-03 01:12:57.5710

That doesn't sound right at all - certainly not how my DT25 works. Sounds like the LVM switch is working the opposite way it should.

Re: DT25 LVM question
by Crusty_Old_Rocker on 2012-07-03 02:47:07.1110

Tell me what happens when you adjust the master volume and channel volume in both Normal and Low Volume Mode.



Re: DT25 LVM question
by geppert on 2012-07-03 10:31:41.4960

Thanks Gents for responding to my post.

I am trying to determine if my DT25 is working properly or if it might be defective??? I live a bit remote and my local L6 Dealer doesn't stock these amps so I have no way to make live comparisons. Mine is the first one they've seen !~!  It is a HUGE help for me when members like you who have DT25's respond.

FYI … I also have a SIV-120 and a SV212 MKII so not a stranger to L6 amps.

There are few "issues" with this amp that make me suspicious. The LVM is probably the biggest one.

For Crusty,

Gtr straight in, no Link connected, Drive 20% (9 o'clock), Bass-Mid-Treb-Pres 50% (12 o'clock) Rev off, Class AB, Pentode, Top 1

1) CV 100%, MV 50% - LVM= loud, RVM soft, NOW if I increase the DRIVE to 50% the LVM and RVM are equal, no difference. If I increase DRIVE to 100% same thing, LVM and RVM = same volume.

Another thing, in Top 1, if the Drive is 20% (9 o'clock) CV 100%, MV 100% I virtually get NO volume in RVM. It is unusable. That seems totally wrong to me. Now as above, if I switch to LVM I get TONS of volume.

2) TOP 2, Drive 20%, CV 100%, MV 50%, LVM and RVM same.

3) TOP 2, Drive 20%, CV 100%, MV 100%, LVM = Loud and RVM = Softer

4) TOP 2, Drive 20%, CV 50% MV 100% LVM = Loud and RVM = Softer

Same thing with TOP 3 as above

Things change with Top 4 as follows

5) TOP 4, Drive 20% CV 100%, MV 50%,  LVM = Low, RVM = High

6) TOP 4, Drive 20% CV 100%, MV 100%,  LVM & RVM = Roughly equal

7) TOP 4, Drive 20% CV 50%, MV 100%,  LVM = High, RVM = Lower

As you can see this LVM thing is "all over the map" … which is very weird to me???

Also this ….

In comparing volume between the 4 Topologies (on a scale of 1-10)

1) Drive 20%, CV100%, MV 50%

Top 1=1 virtually unusable volume.

Top 2= 4

Top 3= 2 slightly louder than Top 1 bur essentially unusable.

Top 4=10 HUGE Differential, Volume is killer.

2) Drive 50%, CV100%, MV 50%

Similar results to Drive at 20%.

It seems that Top 1 and 3 require at least 50% Drive to be usable at all ???

I also have some low level hum (but noticeable) on both Triode and Class A which I've seen discussed by others on this forum. Coule be tube and/or Bias related??

I also did this test. I used the POD HD500 Pres for the 4 models on the DT25. I set Channel B's parameters exactly the same as the PreAmp is set on the P500 then compared Channel A & B by switching on/off the Amp Model in the HD500 (which switches the amp over to CHB).

Results below.

1) Top 1 - BF DBL VIB NORM <-> Channel A and & B Virtually the same.

2) Top 2 - BRIT P-75 NORM <-> Channel A and & B Virtually the same.

3) Top 3 - CLASS A-30 TB <-> Channel A and & B Virtually the same.

4) Top 4 - TREADPLATE <-> Similar but Channel B was definitely a more "full sound" from mids down to lows than the Pre Sim. Also had to back CH B CV down to 60% to equate Volume toth CH A

Update ... a suggestion was made to try "Treadplate Full" and in fact that was much closer to the DT/25 Amp Top 4  than "Treadplate Pre".

These tests were encouraging.

In summary,

My concerns are as follows ….

1) LVM mode seems to work incorrectly in many cases

2) Huge (and I mean HUGE) disparity between relative amp volumes between Top 1-2-3-4

3) At 20% Drive Top1 and Top 3 have virtually no volume in RVM but tons of volume in LVM

4) Noticeable low level hum in both Triode and Class A mode.

For a $1000 Head, these issues are somewhat unacceptable for me.

However, I have seen SO MANY positive comments my forum members about these DT amps that I question that this particular head I have may be defective?

If I can get a few members like yourselves to compare my results with your DT25' s and we can find some conclusive data to suyggest that my head may be defective, then I have good qulity ammo to go back to the dealer with for an exchange (which they will have to order in).

Thanks so much in advance for your comments.

Re: DT25 LVM question
by clewin on 2012-07-23 19:27:30.2110


I am on # 2 DT25 head.  The first was a bad volume control on the second channel.  They orderded a new one in and now this one is making static crackle and pop sounds when you touch the strings.  I took it in to the store and they hooked up a new LP and Egnater speaker and the crackle and pop happened when you touched the strings or bridge. 

I am thinking they may have some manufacturing problems that they need to deal with.


Re: DT25 LVM question
by geppert on 2012-07-23 19:43:04.0690

Hey Tom,

I opened a L6 "support ticket" with regards to my issues and they replied that "the amp needs to be serviced". I have a personal policy that says "thou shalt never knowingly buy a defective product". To that end the L6 dealer has ordered a new replacement DT25 Head. I will try Head #2 before it leaves the store to dertermine if it has "issues" now that I know what to look for.

As with your issue, anything "snap, crackle, and pop" related is usually "tube related" in my experience.

Re: DT25 LVM question
by DarthHollis on 2012-07-26 11:30:27.0380

I'm not saying you don't have an issue with your DT-25 but may I give a possible explanation?

The way we have come to understand the DT series to work (this has never been clarified by Line 6) is that in Normal Volume Mode you are using the Pre-amp version of the amp (and at least for topologies 2, 3, and 4 the matching cab simulation).  In the Low Volume Mode you are using the full amp model (also with cab simulation).

Now, when I say with cab simulation, it would also be with the extra equalization that the POD HDs use when connected to that particular type of amp.  By this I mean the HD's output mode is set to combo pwr amp or stack pwr amp.  So the DT is using those cab models with the output mode EQ.

Also, in the modelling are the extra amp editting parameters.  Changing the "Master" setting can greatly effect the volume of the patch on the POD HD. 

It is possible that if the "Master" settings which are internal in the DT-25 are set to 100% you could be getting unwanted power amp saturation which is giving you extra distortion and sustain but also causing more crazy changes in the volume.  The "Volume" knob on the DT may also change the "Master" when in LVM.  As you increase the Volume you also increase the Master.  It just kind of makes sense to me to set up the LVM this way.

Again, these are all assumptions.  I have a DT-50 and therefore I cannot test my hypothesis but I will attempt to later anyway after my girlfriend leaves for work.  I will do this by setting up similar patches in the POD HD 500 and trying to get the same results you did.

Can anyone else help confirm or deny what I'm saying?  I am sure there will be no official response from Line 6.

Re: DT25 LVM question
by geppert on 2012-07-26 12:29:11.1930

Hey Hollis,

Try these two tests if you would, and let me know what you get.


Gtr straight into the DT no POD or Link connections.

Set Channel A dials for CLASSIC AMERICAN CLEAN but with NO Reverb and CV (Channel Volume) at 40% (so you don't deafen yourself) and MV (Master Volume) at 100% (hence the reason for 40% CV). Now .... play a chord and switch between LVM and HVM (High Volume or Regular Volume Mode). In my case I get WAAAAAAY MORE AMP VOLUME out of LVM (and relatively clean too) than I do in HVM. This seems odd to me?? In my case, if I really want to get the highest usable volume out of this amp, it would be in LVM mode, MV up full and CV to taste. THAT doesn't seem right to me?


It doesn't matter what amp settings you have or if the CV & MV are up or down. It does seem slightly worse to me in TOP III, and it doesn't matter if you have a gtr plugged in. Switch to TRIODE mode. Do you get noticeable hum??? Then Switch to TRIODE + CLASS A mode. Do you get more noticeable hum ??? I do for sure. It is definitley annoying and aggrivating at home and it is irrespective any other amp settings because I think it affects the output stage directly. It is not an issue live because it is masked but at home there is no way I could have the amp in those two modes. It's like listening to a (noticeable) transformer hum. For a $1000 amp, I just don't think it should be doing this?

Note: I have BOTH DT25 heads at the moment. The origianl I bought and another new one that the store ordered in. Same issues on both amps.

Re: DT25 LVM question
by DarthHollis on 2012-07-26 17:22:49.2680

Test 1  results - Yes, LVM is louder and dirtier. Like I said, I think this is just the internal 'Master' control causing this.  You are using a solid state power amp but you are pushing it harder.

Test 2 results - I don't hear any difference in the ammount of hum.  But, I'm using humbucker pickups and my guitar electronics are very well shielded, plus I'm using a Mogami cable.

I'm thinking that my hypothesis, at least to some degree is correct. 

Re: DT25 LVM question
by greghall on 2012-07-27 01:37:54.5510


Low Volume Mode (LVM) isn't a volume control. It switches on power amp modelling to allow you to get a better drive / distortion at low volume, as low volume in normal mode won't drive the tubes hard enough to get a good distorted tone.

Test 1 does not indicate a problem with amp, because it is predicated on a wrong assumption, i.e. that LVM reduces volume.

As I understand it, LVM should be used with a low master volume.

Re: DT25 LVM question
by Crusty_Old_Rocker on 2012-07-27 04:18:24.8390

You're most likely experiencing the different characteristics of the modelled amps.  For example on amps that don't have a gain or drive control the drive knob acts as the volume control.

You need to remember that the DT amps "behave" like the amps modelled.  The originals differ dramatically in volume level across the range of controls.  The same applies across the 4 "voicings" on the DT amps.

Don't be surprised if the volume disparity exists after Line 6 service it.



Re: DT25 LVM question
by Crusty_Old_Rocker on 2012-07-27 04:27:38.6830

geppert wrote:

Switch to TRIODE mode. Do you get noticeable hum??? Then Switch to TRIODE + CLASS A mode. Do you get more noticeable hum ???

Of course the triode mode has more hum than the pentode that's the nature of a triode compared to a pentode.  Also the power amp valves in an amp operating in class A are running flat out all the time (not idling like a class A/B amp), so there'll be more hum coming from the valves when operating in Class A.

What you have described is normal for the power amp operating under those conditions. 



Re: DT25 LVM question
by Crusty_Old_Rocker on 2012-07-27 04:35:14.6890

The LVM uses full amp modelling including a "cranked" power amp, so depending on the power amp levels you're using in 'normal' mode, the LVM can be louder, display power amp distortion and more "noise" than normal mode.  That's how these amps do their magic.



Re: DT25 LVM question
by geppert on 2012-07-27 09:18:58.8980

Thanks to all who replied to this post. I believe I understand this little beastie now? It has taken a "re-adjustment" in thinking about the amp. I do like the sound of it so it's a keeper (I also have a SV212 MKII and a S IV-120).

The store ordered a new amp. They both are about the same with their characteristcs so the original might in fact not be compromised at all? It is just the way it is so to speak.

It was nice for a few days to play around with 2 DT25's. A possible thought for the future (stereo rig), but then I ain't getting any younger and don't need to lug even more gear around. At home I put the POD500 though a pair of FRFR studio monitors on my desktop so always listening in Stereo. I can see where a pair of DT25's would be nice to have on stage. I use the SV212 as a 2 x 12  cab with the DT25 to provide better stage spread. Works well.

OK ... time to move on .... thanks again to all. Great forum, great user support.

Don from Canada.

Re: DT25 LVM question
by Crusty_Old_Rocker on 2012-07-27 18:21:59.2950

Yes, you have to change your thinking with these amps.  What Line 6 has done is really very clever, they pretty much transform the amp into the modelled amp rather than get an amp to sound like the modelled amp.  This means that the feel, output levels and interactions between the preamp and power amp differ dramatically between the 4 voicings.

The LVM on the other hand takes the full amp models and then the user can amplify that sound using the power amp of the DT.  The best results for LVM come from switching to Voicing I (which has the cleanest topology) and switch the power amp to Class A (which removes power amp crossover distortion).  You do this because the crossover distortion on the Class A/B power amp models is already modelled in the cranked power amp modelling and you don't want to double up on that.  Selecting Class  A means that only the modelled crossover distortion will come through without having real crossover distortion added to it.

Having this level of realism built into the amp modelling process adds some complexity, but the tonal rewards are worth it.



Re: DT25 LVM question
by Stratman82 on 2013-04-05 16:04:46.6890

I don't think this is possible in LVM with a podHD connected to DT amp via L6 link- the class and topology on the amp change automatically when switching between patches on the podHD so you can't just keep it in class A and voicing 1.

Re: DT25 LVM question
by TheRealZap on 2013-04-05 16:37:56.4260

the class and topology are also saved with the tone... so if you save it A topo1 it will stay there.

Re: DT25 LVM question
by Stratman82 on 2013-04-05 22:27:45.4900

Right ok, I assumed that would alter the tone itself but perhaps not.

I must admit that after using the DT25 in LVM with podHD full amp patches for some time now (and being VERY skeptical at first) I'm now getting some great tones....some perhaps even rivalling the amp in normal mode allowing for volume differences. That's with automatically selected class and topology.

I should acknowledge meAmBobbos guide which helped me create these tones and adjust parameters like bias etc for full amp patches.


The information above may not be current, and you should direct questions to the current forum or review the manual.