spaceatl

That's a drag...found something hiding in there huh? You got buzz with nothing connected to the amp? What's your AC situation for the amp?

Sorry....SPAX7 is Mesa's best 12AX7...I use that as a buffer...I use the GTSAG as the inverter...I did compare them both as inverters and found no difference...Never put the GTSAG in as a buffer...It's not traced for that...would not hurt anything...just not measured for that usage...

If I needed more cabinet/mic models in my rig, I would probably go with this: http://www.guitarcenter.com/Two-Notes-Audio-Engineering-Torpedo-Live-Digital-Loadbox--Speaker-Simulator-110000577-i2968794.gc?country=us&currency=usd&source=4WWRWXGP&gclid=Cj0KEQiA6ounBRCq0LKBjKGgysEBEiQAZmpvA7XmQCYqGVIPJ5VdyyK7zFapil-RUW3hmuxpi8JXFi8aApZK8P8HAQ&kwid=productads-plaid^81966816764-sku^110000577@ADL4GC-adType^PLA-device^c-adid^44639487282

hard to say...I know a 12AX7 used as an inverter runs higher current thru both triodes...I suspect the trace matching is a bit different than for a 12AX7 intended for a buffer...No idea how that would translate...perhaps slightly less output potential than one intended for preamp use.... In the case of the DT50 12AX7 buffer, only one triode is used...So I have been debating on sticking one of these on my SPAX7 since the other triode has never really been used...I don't know about the "vibration reducing base"...but it would be cool to get the full life out of the buffer tube... http://www.tubemonger.com/TRIODE_FLIPPER_with_Vibration_Reduction_Base_p/triodeflipper.htm

Good thing you asked again....just checked my DT50...indeed the one nearest the AC power jack...left side looking from the back...

CORRECTION: it's the one closest to the power jack....to the left if you are facing the back...

If you skip the return to your Marshall, then you are missing the tubes in the power amp....You could certainly do that and put an IR on the tone and see what happens... Always nice to get the rig direct when you can...I think I would put something like a Weber Mass Attenuator...It can be used as a dummy load also and get the tone of the rig direct...Keeps it simple...or just put a mic on the cab... https://taweber.powweb.com/weber/mass.htm

I should have mentioned safety in general earlier in the thread...It's easy to forget when you work on these things all the time.... the provided test points are just a ballpark reading regardless of the tube type...bias probe is always a better set of measurements...

The most important thing is not to die when you are messing with a tube amp... Personally, I prefer to stay far away and isolated from the 500 or so volts of plate voltage in the DT50 that can kill you dead... I should have also mentioned that the rear bias mod offers an increased margin of safety when you put the test points and adjustment on the back of the chassis vs an open chassis. That's actually a big part of my own motivation to do the mod...

right, just moves the stock test points to the back of the amp... here is a thread I did in the old forum regarding my MK1 mods....I don't think the pics are there...I will see if I can dig those up...The hardest part is desolding the pots...But I guess it's a little easier in the DT50 as there is only 1...but this might translated into two pots as the DT's are a balance type single pot... http://line6.com/supportarchivenew/thread/24828/

Power....The DT50 does Fender spank tone better than the DT25....But that is to be expected as you need power to do a twin tone with the right dynamics...DT25 doesn't do that very well at gig volume....DT50 does....I have both amps...rehearse with the DT25, gig with the DT50....DT25 is underpowered playing alongside a real drum kit...At least it is for me...

Being able to check the bias without having to pull the chassis out of the box means I will check it more often....That is generally the first 8 or so hours on new tubes as they burn in....things can change a little bit...basically, it more of a convenience mod. The metal chassis mount bias pot is less prone to drift than the typical plastic PCB types...The Weber pots are nice and tight... Basically, tubes can go at any time and I like to be prepared for changing them out without have to take the chassis out...

I have a MK2 that is around 5 years old...Still works great. The only problem I had is one of the power tubes blew the first week I had it...new tubes and it has been fine ever since...

You are most welcome and thank you...I do not mind being called out for what I post here. I will always do my best to try can clarify my opinions as best I can in text. Sometimes it's really difficult to get the context across. I think the Line 6 Service Tech's general advice is extremely sound. Stick to the production design...A user that is really new to tube amps is probably better off sticking to the recommended valves...Odds are they are going to get something close to what RB/Line6 intended and their amp should sound like RB/Line 6 intend the production DT50 to sound. If the specially marked EH valves are traced as tightly as they are indicating, then switching them out and setting the bias to around 35-37 mv with multi-meter should work just great 99% of the time... hmmm, my DT-50....Well, I have only done a few things to my DT-50 thus far...Mounted an NL4 speakon for my cabinets, changed the tubes and changed the speaker. V30s are really a speaker that I love to hate...I think I have 4 of them sitting around. They just are not a good fit for me...I don't like Celestions for my tone...I totally enjoy listening to other players that use them...just not my cup of tea. My first amp was a Mesa SOB loaded with an EV12L....That basically must have imprinted on my DNA and I have always gravitated towards high rated PA type speakers ever since (circa 1982)... I have some prized Madison Minstrels in 212 cabs that I adore and are still in good shape...they work very nicely for extension cabs in combos which what I dig for my rig...however, for the DT50 I went a different route on its internal speaker...I found a new favorite...Jenson Jet Tornado 16 ohm...I tried a bunch of speakers with the DT50 and this speaker is just perfect I think...Not only sounds great...but it weighs 4.5 lbs and does not sound like a neo at all to my ears...There is something really cool about running this amp at 16 ohms that I prefer... ...Bias...hmmmm...It has been some years since I checked...I think it was around 497 volts on the plates and I think I ended up at 35mv...Not really any different than what it was...I do plan to do a rear bias adjust and test points mod on this amp on the next tube change...Which is really kinda overdue...But I have gotten some really good life out of these...not mushy yet...

I guess I will say something since I got called out here...Please keep in mind that what I post on these boards is my opinion based on my own experience. I have been working on and using tube amps for little while and I have my own strong opinons and know what I like and how I like my amps to operate...I have been using Mesa tubes in my DT50 for about 4 years now...same thing in my DT-25....I do use a GTSAGAX7 for my inverter...I have had no issues, my amps have lower noisefloors than they did with the stock tubes and sound fantastic...Same with my SVMK1 and SVMK2...anyhoo...take that with a grain of salt...what works for me, may not work for you... Here is a really great article written by Randall Smith that really explains fixed bias tube amps in a way that most people can understand...Back when tube amps were common, this is how you designed them...Fixed bias means fixed bias...adjustment is needed now because we just cannot get tubes as well matched as they were 40 years ago when you could trace test your tubes at the local drug store... http://mesaboogie.com/media/User%20Manuals/Mark1%20Reissue.pdf He does have some very strong opinions, but it still a good read...Here's link to the Mark 1 Re-issue manual (The article is at the back of the manual)....copied below. Bias Adjustment - Randall Smith Here’s a question we often hear: “Why doesn’t Mesa put bias adjustments in their amplifiers?†Well, there’s a short answer and a long answer to this question. The short answer is that during my 12 years of repairing Fenders, one of the most frequent problems I saw was bias controls that were either set wrong or that had wandered out of adjustment due to vibration. As any honest tech will tell you, there’s lot’s of easy money to be made by sprinkling “holy water†on amplifiers ... uh, what I meant to say is “Your amp needed biasing.†See what I mean? What customer is going to argue with that? It only takes a moment and a volt meter: The Fender diagram shows how: “Adjust this trim pot for - 52 volts.†That’s it. Nothing more. Now don’t be fooled into thinking that tubes “draw†more or less bias, they don’t. The way a bias supply is connected to a tube is akin to a dead end road, it just trails off to nowhere without really completing a circuit. It’s a static voltage and regardless of what tube is in the socket — or even if the tubes aren’t plugged in at all, it doesn’t change the bias voltage a bit. So the end of the short answer is this: Since a bias supply needs to put out the right voltage and never vary, I wanted to build amplifiers that were individually hard wired to the correct values and NEVER needed adjustment. And for 25 years, that’s how Mesa/ Boogies have been built. Time to change tubes? Just plug our tubes into any one of our amps and you’re DONE. No tech needed. NO bills and no BS about biasing. And most important: The bias is RIGHT because it can’t change! Now, you want the long answer? Here’s more information on how our hard-wired bias avoids trouble. Please read on. But first, let’s make an important distinction. Our business is designing and building high performance amplifiers. And for this we need tubes whose variance is within a narrow range. Our warehouse is full of rejects ...oh, they work — they just don’t perform within our tolerance range. We have a very sophisticated computer - based tube testing system (nicknamed “Robotubeâ€) that matches and measures tubes over seven important parameters. It can even predict which tubes are likely to have a shortened lifetime — even though they work perfectly during the test. Because our business is building quality amps, we can afford to reject a lot of wayward tubes. The guys you hear complaining because Boogies don’t have bias adjusters are primarily in the business of selling tubes - not amps. They don’t want to throw away 30 percent of their inventory, so they promote the idea that tubes outside our parameters can be used to “customize†amplifiers and they criticize us because our amps can’t be adjusted to accommodate their out-of-Mesa tolerance tubes. Now you might be thinking, “But I thought you just said that tubes don’t “draw†bias, therefore they don’t effect the bias supply and thus it doesn’t need to be adjustable.†And that’s right. Tubes don’t effect the bias setting, but the bias setting does effect how the tubes work. But how it effects the tubes is difficult to measure. . . . . . . . .. ... .... .. ... .. .. ... .. .. ... .. .. ... .. ( ) ( ) ( ) , ( , ) ( ) Structure of a 6L6 / 5881 Beam Power Pentode. PLATE BEAMCONFINING ELECTRODE SCREEN GRID GRID CATHODEPAGE 19 BIAS ADJUSTMENT: When you set the bias (whether it’s by selecting the right resistors, as we do, or adjusting a trimmer — which is quicker) what you are doing is establishing the correct amount of idle CURRENT that flows through the power tubes. But you can’t adjust the current directly, you can only change it by adjusting the amount of bias VOLTAGE that goes onto the tubes’ control grids. Voltage and current are NOT the same. Current is the AMOUNT of electricity, the “quantity†— and is measured in amperes. Voltage is the degree of electric charge — like the “pressure†to use the old water analogy. Let me illustrate how different voltage and current are: When you scrape your feet across a carpetted floor in dry, wintery conditions, your body can become charged with 50,000 to 100,000 volts of static electricity. And when you reach for the door knob, a spark jumps and you feel it! The voltage is super high but the current (measured in micro-amps) is tiny - otherwise you would die from electrocution. Contrast this with your car battery, which puts out a mere 12 volts. You can lay your hands right across the terminals and not feel a thing. Yet the amount of current available can run to several hundred amperes .. enough to turn over a cold engine and get it started. So current and voltage are two totally separate electrical parameters — though when you multiply them together, you get POWER, which is measured in watts. When you set the bias of an amplifier, you are adjusting the static VOLTAGE at the control grid of the tube in order to produce a desired amount of idle CURRENT flowing to the tube’s plate. A small change in grid voltage, produces a large change in the amount of current flowing — and that’s basically how a tube works. Say that again because it’s super important: A small change in voltage at the grid causes a large change in current flowing to the plate. See, that’s the essence of amplification: A small change causing a large change. And here it’s a small voltage change causing a large current change. The bias conditions are what determines how much current flows through the big power tubes when you’re not playing. And what drives your speakers is flucuations in that current flow when are ARE playing. If the amount of current increases and decreases 440 times per second, then you’ll hear an A note. If the fluctions in current flow are large and still at 440 per second, you’ll hear an A that is LOUD! But for purposes of biasing, it’s the amount of “plate current†flowing with no signal applied that’s important. Unfortunately current is hard to measure because the circuit must be interuppted — as in “cut the wire†— and the meter spliced “in series†with the broken circuit. But measuring VOLTAGE is easy. It is not necessary to interrupt the circuit because a voltage reading can be taken in PARALLEL with the circuit intact. Thus, as a matter of convenience, most bias settings are given in volts at the grid ... even though current through the plate is the important factor. In fact plate current is so inconvenient (and dangerous) to measure that Fender doesn’t even state what the correct value should be. They only give the grid voltage that will produce that current. (That’s the minus 52.) But that only happens if the tubes being used are “in spec.†As long as the tubes ARE “in specâ€, the right bias voltage will always give the correct plate “CURRENT†— but then there’s no need for the bias voltage to be adjustable! If the tubes are NOT in spec, then the only proper way to re-set the bias is to cut the circuit and measure the current while adjusting the bias ... but no manufacturer I know even STATES the desired current value! Be that as it may, when the original bias voltage is altered far enough, it will compensate for the tube’s abnormal performance and the correct amount of idle current flow may then be restored. Clearly this is something most repair techs should not attempt. Some newer amps have LED indicators connected to the circuit which will turn on when the right threshold of current flow has been reached. This is an improvement, and almost worthy if you’re willing to except resistors and lights added into your amplifier’s audio path — which we aren’t. The other “advantage†of this system is that it allows some amp manufacturers to avoid matching their power tubes. The thinking is that adjusting the bias to each tube separately eradicates the inherent differences between the tubes by insuring that the same current flows through each one.PAGE 20 BIAS ADJUSTMENT: (Continued) Again, this has some merit .. but it’s still not as good as using tubes that are matched in the first place because compensating for the mis-match causes the push-pull circuit itself to become unbalanced. Two wrongs don’t really make a right. Some of the other recommended biasing, “methods†— such as -â€.. tubes running red hot, increase the bias .. sounds harsh and runs too cool, turn it down ...†are guesswork at best. Luckily, one of the great things about tube amps is that they can usually stand some abuse without causing any real harm ... at least not immediately. But don’t these alterations imply that you are second-guessing the amp designer and that there’s a better set of operating conditions that the designer missed but the tube sellers have discovered? Now some players may like the sound of their amp altered by tubes with extreme characteristics and with the bias set to help compensate. But often it is the mere novelty of change that they’re really responding to and when the amp goes back to the proper original way, we’ve seen them be far happier still! Because every part in every one of our designs has been meticulously evaluated, compared and stressed over — no matter how seemingly insignificant it might be. And with every design we look for a “sweet spot†where all the parameters — including the bias — come together to give the best sonic performance, consistently and reliably. Every part and voltage is important — yet no one complains that these other parameters aren’t available for tinkering. Consider our patented Simul-Class circuitry where there are two different bias voltages used for separate pairs of power tubes ... and changing one voltage also changes the other. Great care goes into getting this just right and we think we’d be asking for trouble to have it adjustable for the world to play with ... unless you like paying to have your amp messed up. Sorry, I meant to say, “Uh, ... your amp needed biasing.†If that doesn’t appeal to you, then merely plug a matched set of Mesa tubes into one of our amps and you’re ready for tone. Guaranteed. You’d be amazed at the number of service calls we field every day that lead to a diagnosis of out-of-tolerance, non-spec tube problems. To think these would be prevented by including a bias adjustment is something of an insult to you and us. If you put the wrong size tires on your car, do you think changing the pressure will make them right? Please, don’t think this is a blanket indictment of the other guys selling tubes — it isn’t. And their tubes aren’t all bad either. It just doesn’t make sense to pay more of your hard earned cash for tubes that were probably made in the same Russian or Chinese factory and which have the possibility of being outside the performance window we select for your amp. And it pains us to hear the hype and mystique built up around biasing when twenty-five years of evidence affirms our decision to make bias circuits that “never need adjustmentâ€. How much money and trouble that has saved Mesa/Boogie players you couldn’t estimate. Our rigorously tested and hand selected tubes are available at your nearest Mesa/Boogie Pro Center or from us directly. Nobody offers better price, quality or warranty than we do ... so why swerve? Next time we’ll talk about our part in developing the great Sylvania STR 415 type 6L6 and how we’re on the verge of seeing something fairly close reappear on the market. Remember, we still have some of these super rugged mondo-bottles available for older amps — Boogies only please! Until then, Relax, Breathe and Nourish your soul! Cheers! Mesa/Boogie Ltd. Randall Smith Designer and President

have you tried to isolate the issue? Does the POD reset when the link is disconnected from the DT25? Is the PSU for the POD well seated in the outlet socket and to the pod itself? If it is still reseting and power seems good, it would be worth checking the output voltage of the POD PSU with a meter...Should be right around 9VDC You could also check the house power with the meter...Is you house voltage normal? My hope if you indeed do have an issue that it's just the PSU going bad and not the POD....If you can't isolate it to a power issue, then I think a Service Center might be a good next step

I have the DT25 head/cab....It really open up some options for running other cabinets....I have several decent 212 cabs that I use with it sometimes. I use 16 ohm speakers so I can do a pyramid with the stock cab...3x16 in parallel is around 5.3 ohms which is a nice mismatch in the 4 ohm tap...Makes for a slightly brighter tone than a 4 ohm load (or slightly lower sometimes)...The amp gets dark to my ears on the 4 ohm tap...That was one of my favorite changes I made to both my DT50 112 combo and DT25 cab....These amps sound their best running a 16 ohm load IMHO....I tried everything but a kitchen sink in these things and that is where I landed...enjoy!

going from A to AB can pop...Class A has a very specific technical meaning in how the power amp behaves...Technically, the class A amplifier itself does NOT have a master volume...The notion does not exist because a class A amplifier is running at full capacity at all times... That changes with Class AB...The operation output actually does change...The more your turn it up, the more Class A it becomes... The pop can get a bit loud when running at very low volume...however, when running the amp at a healthy performance volume, it should be substantially less...more like a "tick"... That is just some info for you....It could be that your amp has some issues switching topography...sticky relays perhaps... I did notice that you are a little behind on your HD500 firmware....perhaps you could try updating?

I really don't like EH 12AX7s....I think they are very noisy...Not only in the DT50, but also in my old ADA MP-1....They suck...But they are a decent tube for production...functionally reliable...seems like 8 out of 10 of them are noisy...Biggest noisefloor improvement comes from the changing both 12AX7s for something else... I use a Mesa SPAX7 for the buffer and a GT-SAG AX7 balanced for the inverter....I had an SPAX7 in the inverter slot and I cannot tell the difference between the Mesa and the GT SAG....I tried JJs...not impressed...Not bad...middle of the road for me... The EH power tubes (EL34s) are a completely different thing...I quite like those...I think they work quite nicely in the DT50... Although the DT50 just screams, "Put Mullards In Me!"....I am not a JJ fan...take em' or leave em'...good tube...over hyped IMHO...

That is weird...I use the HD Desktop almost exclusively regardless of the situation....running direct, amp, amp direct....etc....Right now I am running thru my old Flex3xl and using the XLRs off the Flexy...my tuner never pops... I suppose something I could try and ask....I NEVER access the tuner on the HD iteslf as I am always using a shortboard....Also, my HD Desktop USB is NEVER connected... When you access the tuner, how are you access it? via the HD or a shortboard? Do you ever have your USB hooked up the Edit? (That is not a good idea in a live situation...The application is not stable enough for that IMHO)

The Park is probably my favorite model out of the bunch for driving hard with a clean screamer/clean level/etc... Even with the drive dimed, this model is pretty clean, but it has some hidden good stuff the harder you drive it...

I use my old Flexy (3xl) with my HD bean all the time...Works pretty decent... Don't forget that you need a dummy plug in the GTR input of the Flexy to turn on the power amp when you run and POD into the Flextone III Fx Returns... By default, the flextone III XL will power up with the FX Loop enabled...However, if you recall a patch where the FX Loop is off, then the FX Loop will be turned off...just turn the amp off and back on again to enable the FX loop, plug in a short board or hook up Edit... and yes, the FX in HD are better than the Flextone...

I have the HD Bean...I love it. It is the same as a 500 without the Variax input...Also there is no FX loop...Has all the same amps as the 500...The announcement of the model packs reads that the HD Desktop update will come later...I have had no issues with my HD bean...

Yea, that is a real pain to get out...Mine too was stuck pretty good...I used a wide blade chisel to pry with...used a little wood block to keep the tolex from getting too messed up...But I messed mine up a wee bit...

I had the same issue when a power tube blew in my SVMK2....Even though both rear fuses were fine, there are two more fuses inside on the power amp PCB...One is for the plate and the other is for the heaters...On mine the plate fuse blew when the tube did and neither rear fuse blew...It's additional protection...I have the combo, so with the head I think you might have two of each fuse type (plates and heaters)...They are pretty easy to find once you get the amp out of the box...just make sure you match the values...