Jump to content

leperclown

Members
  • Posts

    18
  • Joined

  • Last visited

Posts posted by leperclown

  1. Hi all,

     

    A year ago, I had my DT50 1x12 repaired, fully retubed and biased by a Line 6 authorised tech here in Melbourne Australia.

     

    I hadn't used the unit much over the last year, but got it out to try the amp and also see how it would perform using my Boss GT1000 direct into the return/power amp in socket.

     

    Before doing this, I decided to re-bias the amp. (I have been doing this for the past 20 years with a wide variety of tube amps. I have the necessary gear and the confidence to perform this procedure). However, usual warnings about the potential FATAL consequences of servicing tube amps - Don't open up and work on a tube amp unless you are ABSOLUTELY sure of what you are doing.

     

    While re-biasing the DT50, I noticed there was a significant difference between:

    • The bias reading from the internal test points (3 prongs); and
    • The bias reading directly from the power tubes (using 'plug-in, in-line probes)

     

    For example, for my final settings (recommended: 35mv per tube) I got:

    • Internal test points - V1: 42      V2: 44 
    • In-line-probes -         V1: 34      V2: 36

     

    Based on past experience, I have high confidence in the accuracy of the in-line probe readings.

     

    It would appear that, if you rely on the internal test point readings, the DT50 might be biased too 'cold' (by 8mv). This could result in the power amp sounding lifeless, with reduced dynamics. The implication is that, using the internal bias points, if you want to actually bias to 35mv a tube, each tube would need to be set to 43 mv a tube, which is a little scary.

     

    My Questions:

    • Is there a basic flaw with my analysis?
    • Has anyone else noticed this variation?
    • Is there an explanation for the significant variation between the test point and in-line tube bias readings?
    • Which reading would you trust - internal test points or in-line bias probe?

     

    BTW, the DT50 sounds amazing on its own (particularly stock voicings I & IV) and it is an excellent power amp for the GT1000 (or other modellers I would imagine). It's a pity it is so big (same width but taller than my Marshall JVM 410 100w 2x12 combo) and so bloody heavy!

     

    Cheers!

     

    Paul

     

  2. Many thanks, Psarkissian. Yes it is a third party app with no affiliation to L6.

     

    I was just curious if someone (independently) had put together a guide for it.

     

    A couple of days down the track, I think I understand the functionality now.

     

    Cheers & thanks

     

    Paul

  3. Hi all,

    I picked up my DT50 1x12 from the repair shop three days ago. Took exactly 1 year and three days from drop off to pick up!!. 

     

    Parts required: 5 caps and a digital potentiometer. I also had new EHX pre & power tubes fitted.

     

    So far so good. The amp sounds excellent, especially the Blackface (I) and Mesa (IV) topologies. The Marshall model is a little underwhelming (Maybe my JVM410 has spoiled me for Marshall sounds).

     

    Using DT Edit, I have set up channel A to have 'No Model' and have put my Boss GT1000 direct through the Hi input, with cabs on the GT1000 turned off. (If anyone could point me in the direction of DT edit instructions, it would be much appreciated).

     

    Extremely happy with the results.

     

    It is one heavy 1x12 though!, and as wide as my 2x12 cabs - probably to account for the amp unit width.

     

    Cheers!

    Paul

  4. Hey Psarkassian,

    many thanks for the response. I absolutely get the points you make (and have previously made) about the link between the tube characteristics, biasing and the modelling. My point (poorly expressed) was that for this relationship to be optimised (or indeed not cause damage to the amp) then the characteristics/specs of the nominated tubes would have to hold absolutely constant across manufacturing batches over many years. It's the tube manufacturing quality and standards (Chinese 12AX7's & EHX 6L6's) that I am skeptical of.

     

    I believe that the most optimal combination is a modelling preamp mated to a tube power amp + guitar cabs. I have previously had a SpiderValve 100 (MKii) and that got awfully close. I am hoping that the DT amp closes that gap even further.

     

    Cheers & thanks!

    Paul

  5. Hi there,

    long time tube amp user, modeller user (currently Kemper , Atomic Amplifire, Boss GT 1000). Recently purchased a DT50 112 (currently in the shop getting repaired - refer "Whisper Quiet" thread).

     

    For over twenty years, I have changed my own tubes and re-biased amps. I am a bit of a tube 'cork sniffer' and have my own tube testing gear and a fair supply of tubes of multiple brands.

     

    I am not a tech and would always bow to Psarkassian's greater knowledge on this topic. However .....

     

    My experience over time is that all tube brands (except maybe Mesa & Groove tubes) can vary significantly within classes, particularly the cheapies. 

     

    I find it hard to believe that a fairly generic 'Chinese preamp' tube or Chinese manufactured EHX 6L6 could be the difference between an amp failing or working properly. (If this is the case, isn't this an amp design issue?).

     

    Have these Chinese preamp tubes and EHX 6L6's been unwavering in their specifications and performance over the past 10 years - Based on my personal experience, this is not the case.

     

    I could understand it if tube specifications or tolerances were published or if Line 6 tested, branded and sold 'recommended' tubes, but blind faith in fairly low budget tubes seems a long stretch.

     

    Call me cynical, but it sounds like marketing hokum.

     

    Cheers!

    Paul

  6. I received the following response from Line 6 (re Service Bulletin 059):

     

    "Your amp was built Post-Affected units, so no Service Bulletin-mandated mods are required"

     

    This is very good news. I will post how the volume IC repair work progresses.

     

    Well done, Line 6! Very rapid response.

     

    Cheers

    Paul

  7. Hi all,

    Today I purchased a used DT50 112 for an excellent price ($200 Australian). The vendor said that the amp was very quiet (as in "whisper quiet"), but didn't know why. 

     

    I thought I would take a chance on the amp because of the low price.

     

    When I got the amp home:

    • Wiped down the Tolex (came up very well)
    • Fitted 2 new El 34's and 2 new 12AX7's
    • Did a factory reset power up
    • Unfortunately, the amp was still very, very quiet  (I did toggle the master volume, but it made no difference)
    • I toggled the topology, pentode & class switches, but again, it made no difference
    • Tried a separate speaker box (maybe the onboard speaker was blown), but again, it made no difference

     

    I will have to take it to a Line 6 repair shop to get it looked at, but any thoughts or suggestions would be most welcome.

     

    Many thanks

     

    Paul

  8. I played an outdoor gig a couple of days ago in bright sunshine (warm to hot weather). I used my Spider V240 + FBV3 for ease of set up.

    Unfortunately the display and pedal lights on the FBV3 were totally useless and could not be seen. The pedal lights were slightly discernible, but the display could not be read at all. The display on the amp was clear and the pedal board functionality was fine, apart from visibility.

    1.        I tried a different Cat 5 cable, but the problem persisted

    2.        I covered the display with a thick towel to see if it was just the direct sunshine on the board making for poor visibility. Under heavy shade, the display was very dim and just readable from close up

    As a short-term fix, I narrowed my patches down into 2 banks (1 & 2) and wrote scribble strips for each footswitch for the two banks. Worked ok, but very annoying.

    When I got home and turned on the unit, visibility was fine again.

    Also, during a song, I must have accidentally tripped the looper and recorded the main riff and I couldn't turn it off. I had to power down the amp mid song to reset - stern glares from band members ... I would love to be able to disable the looper button for gigs, but I am unsure how to.

    Re the issue of FBV3 visibility, I recall reading about the same issue with the FV MKII and its poor functionality in warm/direct sunshine.

    I suspect that, as the unit heats up in the sun, the display malfunctions. I think the footswitch lights (LEDs?) function ok, but there is just poor visibility in direct sunshine.

    Has anyone else had this experience?

    Cheers
    Paul

  9. Hi AD Brown, thank you for responding.

     

    I was talking about calibrating the built-in expression pedal on the FBV3 (which I am using with a Spider V240). Someone from Line 6 responded to this question on another forum (TGP). The answer is that the pedal is 'self-calibrating' - which is very slick.

     

    However, I am now wondering if an external expression pedal (plugged into the FBV3) would require calibration and if so, how?

     

    Cheers & thanks!

     

    Paul

×
×
  • Create New...