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Posts posted by Martijndrift

  1. You probably want to set it up using the 4 cable method.

    Connect your guitar to the input of the pod

    Connect the fx send of the pod to the input of your amp

    connect the fx send of your amp to the fx return on your pod

    connect the line out of your pod to the fx return on your amp


    Then you should make a patch which has the block fx loop in there, all effects you set before that block will hit the front end of your amp, and all that you put after will be used in the effectsloop, all while bypassing the amp models. You can also make other patches and deactivate the effectsloop, this will bypass your amps preamp and allow you to use the preamp sims from the pod (so you can actually switch between preamps).


    you can find some more info here: http://line6.com/supportarchivenew/thread/55328/


    bare in mind that the signal routing through the pod from the guitar input to the fx send generates alot of hiss, at least it does for me, It might be ok for you.



  2. Hello Everyone,


    I´ve been successfully using my pod hd500 for the past few years, mostly in combination with my dt25 and using studio monitors. It wasn´t until recently that wanted to use it with the 4cm. I built myself a naylor sd60 clone and I was hoping to use it in conjunction with my pod.

    The amplifier itself is nearly quiet with a guitar plugged straight into it, even at the highest gain settings. Using the pod in the effects loop for reverb and delay and plugging the guitar straight into the amp also poses no problems (allthough it does introduce a little bit more hiss). However plugging the effects send of the pod into the amp's inputs generates an unusable amount of hiss (audible while playing). The same hiss occurs when there is only one cable from the pods fx send plugged into the input of the amp, while nothing else is plugged in. I tried messing with different settings on the pod, but with little result. 

    Bare in mind that this is white noise, no 50 or 100 hz hum (europe).


    Is the fx send supposed to be this noisy and are other people experiencing the same problem, or could it be that my unit is defective? (would not be the first time  <_< )

  3. When you put the new tubes in, check the bias.  Turn it all off and swap the tubes and recheck the bias.  If the hi/low volatage doesn't move with the tubes then the issue is probably in the amp.  Do they bias out evenly with adjustments?  If so that shouldn't be an issue either.  Recheck the bias after a few hours playing just to see if anything is changing.  Did you change the 12AX7 as well?  It has a role in the power section even though its not a preamp tube.  Are you certain you got the right fuse for the amp?


    I am sure you did all these things, just brainstorming a few things to be certain...  If it keeps blowing tubes it needs a repair ticket...

    Thank you for generating some ideas!


    Unfortunately there is only 1 bias adjust pot, this means that when I set one tube at 25 mV, the other is way off. So I try to set it in a way where both tubes are equally far off from the implied 25 mV. I had the same thought about the phase inverter, say if one side of it is damaged, than one tube in the poweramp might not be getting the same current. When I talked to a friend of mine about this he seemed quite convinced that the phase inverter would not cause a difference in bias voltage. But I wanted to try it anyway.

    I have used fuses with a slightly lower rating (3.15 ma as opposed to 3.75) I could see this being the cause for blowing a fuse, but then again it only blows after a tube breaks, so I doubt this is the reason for my problem. I also only started using these after the original fuse blew. Just to be certain I'll order the right value.


    Yesterday during rehearsal I put in some old sovtek el84 and the phase inverter that came stock in there. It did live for 3 hours, so I'll have to see in the next couple of weeks if it stays alive. The bias difference is still there though.

  4. you seem to know what you are doing but I didn't hear you mention actually adjusting the bias to match them up... I hope you did...  If not see the link below...



    Yes I did, thats why I tried to balance the difference in bias voltage as close as I could to the 25 mv that line 6 implies.

    Independently of the set bias value, the tubes should give the same value. The only reasons I could think of that affect the measured bias voltage (from a mechanical engineers point of view, I might forget something?) are:


    Difference in the 1 ohm resistors, I measured these and they were withing the 1% deviation that is associated with these resistors.

    Difference in tubes, ruled this out by using different sets of tubes.

    Temperature of the tubes (different resistance with temperature), I let the amp warm up for about 20 mins before setting the bias, so I doubt this is the cause.

    A defect screen resistor maybe?


    @Brazzy, it's odd that there is a similar problem with your dt50, but then again I would be happy if I got 120 hours on the powertubes :P


    Dispite of the difference in bias, which with my previous set of tubes was within the +-3 mv range that line 6 gives, it should not damage the tubes up to the point where they will blow in a couple of hours right?

  5. Hello everyone,


    I have been a proud owner of a dt25 combo for almost 3 years.

    Since a few months ago I started having problems:


    The first time, the tube protection fuse blew, I noticed the tubes were damaged, so I put a new set of matched JJ EL84 and a new fuse in.

    When I wanted to bias the amp I noticed a difference in the bias rating of the tubes, where 1 tube would be at 21 mv the other was at 29 mv.

    I immediately returned the tubes, the shop owner measured the tubes at different plate voltages, and everytime they were matched perfectly (I have the test reports). The tubes did not seem to be the issue


    I used these tubes for about 3 months, with no sound issues whatsoever (4 hours a week at rehearsal volume) after which they blew again (along with the fuse).


    I decided to order a set of matched sovtek el84 (like the standard ones), put them in and noticed where one tube would be at 22 the other would be at 28 mv. Still a difference, from that moment on I was pretty sure that it was a problem with the amp.


    These tubes lasted for about 2 months after which one tube failed (one side of the tube was covered in a mirror like metal finish on the inside).


    I took the amp apart, measured some components for the bias setting circuit, this seemed to be in order. Did not see any components that were visually damaged. 


    I just assumed that I must be having alot of bad luck, I put in new tubes: sovtek el84m, again a matched, again a difference in bias voltage. These tubes lasted only about 10-12 playing hours.


    At first there was a drop in volume as if one tube failed, 40 mins later the fuse blew and I noticed one tube being damaged as well.


    I don't know if blowing the fuses/tubes and the difference in bias voltage are related, but I do suspect they are. I have quite a decent understanding how the power section of this amp works so I would like to fix it myself.

    Also the amp was always in class ab pentode mode during failure (this is the only mode I use it in)


    Has anyone had similar problems in their amps (or other amps with a class a/b push pull power amp for that matter). Or does someone know what the problem could be or which components I should start checking?


    Thank you in advance!

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