Posts posted by gatacca
I've been searching high and low for a proper step by step,instructional kinda video/manual, for biasing the tube power section for the Line 6 DT50, but to no avail.
I think it's high time, the forum have something like this in place so we can do the maintenance ourselves. Last i check, it cost nearly the price of a single tube to send it to the amp tech for biasing...
Hope any guru out there can help? =)
I don't own a HD500, but i ran my effect pedals direct infront into my DT50 212. I've been listening closely to the sound of how the volume and master react to each other.
I really don't know the exact answer in regards to power tube being driven harder, but i find that with higher volume on the channel, gives better sounding and fuller result. I kept the master low all the time because i play in the bedroom setting most of the time, but occasionally did crank up the master as well to verify the tone. Still volume channel high, gives the best result to my ear.
If you look at the preset sheet that comes with the amp, they do set the volume channel high all the time. I assume this is to make sure the tubes are driven all the time.
And i do find the preset sheet tones comes best to my ear. I've tried nearly all the combination but still find myself going back to the preset sheet that comes with the amp.
Just my 2cents. Would be great to share your findings too =)
Anyway, just an update. I got my problem solved, together with some interesting findings where i think most can benefit from it.
The problem i described above, only seems to happen in my room where the power socket/outlet to be suspected to be not grounded properly.
Problem: Besides the noisy treble eq knob issue that i encounter, i am getting all the general issue with the DT50 amp like all other user and owner out there where issues like occasional pop, hum, hiss and really loud noise, all i believe is due to the grounding issue of the power outlet.
Findings: So what i did was i brought the amp out of my room into the living room, where i believe the power outlet to be of better built and ground. Before that, i also swap and interchange the position of the 2 unit of 12AX7, making sure it is seated proper. Next up, i power up the amp, plugging my guitar direct without any pedals running in the front. And voila! True enough the DT50 was quite like a mouse. It was soooOoo quiet to the extend where i can even safely say that i can do proper recording through it, without even needing to 'gate' it like some Line 6 tech suggest. Mind you also i did not change the two EH 12ax7 to other brand.
Next, i boost the volume and master real loud and start turning the treble eq knob, and voila! No more rotary like dialing sound.
Next, i brought the amp back into my room and every single problem just came back. Thank God i have another power outlet in my room where i can use, so i plug it into it. And behold, there were a noticable hum (definate noisier than when in the living room compared) but it is still ok. No treble eq knob rotary like sound issue as well.
Next, i plug my guitar pedals and run it infront of the amp. And the problem came back. The noise (much quieter this time since the amp is at the new power outlet), and also rotary eq knob sound is back!
At this point i start to suspect it's the grounding issue on my pedals as well. I have a KFK 10 band eq pedal on my pedalboard that runs on 18v. I ran a OneSpot adapter for the rest of the 9v but at one of the daisy chain 9v plug, i placed a diago 9v to 18v adapter to power my mxr kfk 10band eq. I suspect this contributed to the noise and general grounding issue that can lead to the amp to behave weird as well, hence i unplugged the 18v KFK from my chain and VOILA! No more noise (small hum is still there, i suspect due to the power outlet again, but at least much better than the other outlet in the room), and also no more eq knob issue!
Solution: MAKE SURE YOUR POWER OUTLET GROUNDING IS GOOD! And don't plug multiple electrical appliances into the outlet and share it with the tube amp and also pedal board power. Also, avoid using cheap extension electrical cable. Make sure it is the 3pin version with proper grounding and the cables are thick and of high quality built.
I guess tubes are more senstive since it's microphonic. And since the DT50 preamp section is still running digital (boosted level by the 12ax7), i suspect any grounding issue can really magnify the issue, since digital can be sensitive as well at times. The power supply can really make or break your amp sound! =)
Hope this helps the rest.
Would need your help to verify if you guys also experience the same issue.
I seems to have a weird old rotary phone like noise coming out of my amp when i turn the EQ knob especially on the treble knob, and especially obvious on topology II,III or IV, when you turn up the channel volume up to at least close to 12 oclock or beyond and considerable amount of master volume.
Can anyone of you guys verify if you have the same issue?
I try bypassing my pedals where my guitar goes direct into/ infront of the amp and still the same issue.
It is more prevalent when you turn the volume and master real loud.
Without playing any note, guitar volume knob still up, muted the strings, while turning the treble eq knob, gave the dialing sound.
A low-midrange kinda "dub dub dub dub dub dub" like noise.
I call up the tech shop , authorize dealer for Line 6 where i bought the amp from, and they said it might be the motherboard or IC issue.
I just bought this amp 3 days ago and now this issue? I really hope the guy is wrong.
Hope any of u guys can assist here. Thanks
Biasing The Dt50 212 Combo
in DT50 / DT25
Thanks for the tip guys. Appreciate it much. I did come across that thread mention, but i am thinking of something somewhere along the line of a video tutorial, or something with pictures, indicating step by step, what to do, what to touch, and what NOT to touch. As mention by spaceatl, it can really kill you....life is precious...and i don't wanna loose mine just yet...lol =P
That thread also did mention of using a Dual Bias Tester. Is there anyway to bias the amp without needed to purchase the tester?
Just wondering if anyone has done it with just a screwdriver to adjust the pot and also plus with just a multimeter... ?