What causes a loss of clean headroom

Discussion in 'Amp Central Station' started by 57fenderstrat, Oct 16, 2019.

  1. 57fenderstrat

    57fenderstrat Tele-Meister

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    hey folks,

    I’m still pretty new to tube amps. What are normal causes of your clean headroom lowering?

    My tweed deluxe headroom seems to be different latly, before I could almost never get any kind of breakup in my apartment. I had to have the volume at at least three and my guitar volume all the way up before it would get close. I’m noticing now it’s getting some light breakup whenever my guitar volume is full, even if the amp is on 2 or lower It sounds really good though but I’m just wondering what could have happened for me to seemingly lose some of my headroom. The tubes are still newish, I changed them maybe a month or so ago.

    I was running it cranked for a good while the other day so maybe a punished the power tubes too hard ? Maybe the speaker ?

    I’m not nessarily trying to get my old clean headroom back because right now it sounds good but I’m just wondering what happened.

    Could I have pushed the speaker too hard the other day or do you think it’s more tube related?

    Right now it has RCA 5y3 , RCA blackplate 6V6 , new gold lion 12ax7, and some old GE 12ay7.

    I know this could be a number of things but I was wondering if there were any common causes of this just so I could understand more about it.

    I have a few different sets of new tubes from tubedepot and KCA on hand but I don’t really want to start pulling and trying things if I don’t have to.
     
  2. twangjeff

    twangjeff Tele-Afflicted

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    Have you changed the volume on the channel that you aren't using?
     
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  3. Dacious

    Dacious Poster Extraordinaire

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    The volume controls are interactive - even with nothing plugged in the the other channel. Playing with the two controls changes the preamp gain, and breakup point.

    Plus - Tweeds like Matshalls tend to have a little 'hair' whatever the volume. You're probably just noticing it.
     
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  4. 57fenderstrat

    57fenderstrat Tele-Meister

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    Nope it’s not a volume knob thing cause it still seems different than it was before with the other volume off.

    Maybe these tubes have alittle more hair than the last set or something, maybe I am just noticing it better than before hahah maybe I’m just imagining it but it definitely seems different
     
  5. 57fenderstrat

    57fenderstrat Tele-Meister

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    It had new groove tubes in it before so maybe I’m just noticing the difference in headroom now, maybe those tubes stayed cleaner longer or something
     
  6. Bellacaster

    Bellacaster Tele-Holic

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    I had a bad output tube in a PRRI that ultimately died that caused lower headroom over time. It sounded great until the tube went and it started motor boating.
     
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  7. corliss1

    corliss1 Friend of Leo's

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    Whenever there is a change, either good or bad, something happened.

    If you changed tubes, power or preamp, that could absolutely do it. It could also be an issue with a power tube not conducting properly, so one tube is doing the heavy lifting, resulting in much earlier onset distortion. I can hear the blown resistors now in a Pro/Blues Junior as the early distortion almost certainly means a screen resistor is gone.

    Could be the bias has changed somehow. Play the amp for a few minutes, then get the room dark and check for redplating on one or both power tubes. (google image that if you're not sure what to look for)

    If in doubt, get it to a tech.
     
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  8. 57fenderstrat

    57fenderstrat Tele-Meister

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    Interesting I will look for red plating later tonight. I think it could be something with the power tubes but as of now it still sounds good, almost like a happy accident. It could get unpleasant over time though. I could try to put some new tung sols in and see if it is back to normal
     
  9. Wally

    Wally Telefied Ad Free Member

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    You should be able to touch those power tubes for a part of a second to judge whether or not a tube is conducting. If you feel a cold tube, that tube is not conducting...and you will get trash sound. If the power tubes are not redplating and are both about the same temperature, your problem might be elsewhere. If you have a 12AX7 that you pulled out for that Gold Lion tube, try it in V1. If there is very little change, then sub it in V2. If there is no change there, then it is tech time.
     
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  10. peteb

    peteb Friend of Leo's

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    this is a good case to make a voltage chart when your amp is sounding good.

    If the sound changes, check the most recent voltages to the voltage chart.




    What other data is good to have in your back pocket?

    bias info

    resistance(s) of the OT primary


    what else?





    If the DC voltages check out, then the change is probably due to a bad tube or something is messing with the AC signal.





    next thing after that is get familiar with what the signal voltage should be at different locations in the amp.
     
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  11. Axis29

    Axis29 Poster Extraordinaire Ad Free Member

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    '... with the other volume off.' How about with it sitting about 9 O'clock?



    Required viewing for owners of 5e3's.
     
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  12. 57fenderstrat

    57fenderstrat Tele-Meister

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    Yeah that is a cool vid ! , it’s not the volume knob , I no it kind of cleans up and can thin out the mids with different settings on the unused channel but this is different. Before I couldn’t get any kind of hair on the volume up until like 3-4 , now I can get it at any volume level and I have a very small amount of clean tone available.
     
  13. muchxs

    muchxs Doctor of Teleocity

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    I'm more concerned about red plating tubes than I am about electrocution. For example I biased a Marshall the other day. It had been eating tubes. It was biased over 100ma...

    I've seen 'em redplate so bad they melt the glass.

    Still, a 12 watt cathode biased amp shouldn't be so far off, not unless it has a pair of badly drifted Tung-Sol reissues.

    Hey! That might be it. If one 6V6 it takin' a break or is substantially weaker than the other the amp will nuthin' but distort.

    Pull one 6V6 some time to hear what I'm talkin' about.

    Oh, yes.

    Brown it out, it's a Poor Man's Maven Peel.
     
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  14. Axis29

    Axis29 Poster Extraordinaire Ad Free Member

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    If the other channel's volume is on 9, and you have zero, or very little, headroom, than it is time to look at other things. If it recently got new tubes, they may be gainier.

    But remember, your amp's max volume is usually somewhere between 2 and 5 on the volume knob. After that, it's just more saturation (and honestly, maybe a little more volume...). 5e3's go from thin and quiet, to too loud, in a small turn of the knob. But, after the 'too loud' number, is where the goods really start kicking in! LOL
     
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  15. 57fenderstrat

    57fenderstrat Tele-Meister

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    Okay so it didn’t look like anything was redplating.

    I put in a brand new set of tung sol reissues, powered it up and it rumbled steady like a car motor. I pulled those out immediately and put the RCAs back in and the motor sound stopped. I just lightly chop sticked the tubes and it sounded like the V1 12ay7 was definatly coming through the speaker. Once it cools off I’m gunna try to put a brand new 12ay7 in and see if that helps. Who knows maybe the microphonic tube is an unrelated thing. I would be bummed if it was a cap or something because the amp is only six months old.

    I won’t poke around with anything else except for the tubes.
     
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  16. 57fenderstrat

    57fenderstrat Tele-Meister

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    I guess that’s all it was cause it sounds normal again, so much more clean headroom like it had before. Seems louder too. The old GE tube did sound kind of cool so I will hang on to that one too. It seems weird though I have only had the amp for six months or so and this is the third 12ay7 I have had to put in there. Hopefully this one lasts. Anyways for now I would say everything is normal again
     
  17. corliss1

    corliss1 Friend of Leo's

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    Could be a bad string of tubes, could be something is up with the voltage at that socket. I'd say it if happens again to get it checked out.

    What type of 5E3? If it's only 6 months old I'd expect there to be some type of warranty.
     
  18. 57fenderstrat

    57fenderstrat Tele-Meister

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    It’s a fender custom 57 deluxe, yeah i should look into the warranty I probably had to send something in sooner than now but I will see if I still have the info laying around.

    I would like to learn more and know enough about amps to do something like that voltage chart. I’m still pretty new though but I find I’m learning alittle more each day. Yeah maybe something is going on with that socket because when I got the amp the tube in it went microphonic a few weeks later and apparently so did this one I put in a month or so ago. For now I won’t worry about it but if it happens again I should have someone take a peak at it
     
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  19. G.Rotten

    G.Rotten Tele-Holic

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    I'm no amp tech but from my experience this exact thing has been caused by dying power tubes. Not to say it couldn't any dying tube, but power tubes don't last as long as pre-amp tubes.

    My DeVille always sounds best right before I need new tubes.

    If you've been swapping your own tubes it's important to know how to bias tubes (which I don't) so they operate their best & last the longest.
     
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