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Question:

I played a gig Fri night and when I started the 4th set my amp seemed to sound "not quite right", like it had lost some volume and punch. Considering that I’d had a few (or so) beers and it was time to play I didn’t really stop to think about it, thinking that maybe the beer and loud stage volume had affected my hearing and the amp was OK.  It was a 2 nighter, so tonight when I showed up to play I was tuning and before the gig and when I turned on the amp I noticed a low buzz coming from the amp.  Also, it still didn’t sound quite right.  Being sober tonight I decided to look at the tubes and I saw that 2 of the power tubes were glowing bright, cherry red when I took the amp off standby.  On standby everything looks normal, but switch off the standby switch and immediately 2 power tubes glow red hot.  The amp is a Dr Z Maz 38 Senior 2×10 combo (38 watts with 4 EL84’s).  The 2 tubes that are glowing are the 2 on the right when looking at the amp from the rear.  Being that the 2 tubes are side by side I assumed that one side of the push-pull amp has a problem.  My amateur assessment is that maybe one of those glowing tubes took a dump and it’s throwing the other out of bias.  When I wake up tomorrow afternoon I’ll swap the tubes and see if the problem follows.  Any other suggestions?  LV, if this is tubes then what should I replace these 4 EL84’s with?  I’m gonna need ‘em fast because I don’t like lugging the Tonemaster to gigs if I don’t have to.  Thanks.

Response:

Yup..yer 2 tubes are shot. Replace those two and you should be good to go ( rebias maybe..you’ll be fine for a while if you don’t ). Peace, Polfus Check out my website: http://www.geocities.com/PolfusPage

Response:

Don’t be cheap with your amp. Especially something like a Doctor Z, which is a cut above the "run of the mill" (or so I have been led to believe, I’ve only serviced one myself, so I can’t say I know them inside & out). You should replace the ENTIRE set, NOT just the "red plate" victims. It’s kind of like only replacing half a set of strings when they wear out. And, really now, EL84’s are some of the most reasonably priced tubes around (unless you’re one of those brain washed suckers who buys Groove Tubes). Not only will a whole new set alleviate your problem, your amp will sound better (tighter low end, and more definition all around). Give your amp an "oil change", it deserves it.

Response:

Hello,     I’ll concur with a recommendation of a quad of Tesla EL84’s, and I suggest you consider replacing or at least trying a new 12AX7 in the first position pre-amp socket.  That tube can take a pounding and you may be pleasantly surprised to hear the difference.  You can pick up several different brands and see which you prefer for tone and sound.  Fairly cheap for the tone upgrade and sound.     Walk in Beauty, Peace.  Scott – Hide quoted text — Show quoted text – >Don’t be cheap with your amp. Especially something like a Doctor Z, >which is a cut above the "run of the mill" (or so I have been led to >believe, I’ve only serviced one myself, so I can’t say I know them >inside & out). You should replace the ENTIRE set, NOT just the "red >plate" victims. It’s kind of like only replacing half a set of strings >when they wear out. And, really now, EL84’s are some of the most >reasonably priced tubes around (unless you’re one of those brain >washed suckers who buys Groove Tubes). Not only will a whole new set >alleviate your problem, your amp will sound better (tighter low end, >and more definition all around). Give your amp an "oil change", it >deserves it.

Response:

> Don’t be cheap with your amp. Especially something like a Doctor Z, > which is a cut above the "run of the mill" (or so I have been led to > believe, I’ve only serviced one myself, so I can’t say I know them > inside & out). You should replace the ENTIRE set, NOT just the "red > plate" victims. It’s kind of like only replacing half a set of strings > when they wear out. And, really now, EL84’s are some of the most > reasonably priced tubes around (unless you’re one of those brain > washed suckers who buys Groove Tubes). Not only will a whole new set > alleviate your problem, your amp will sound better (tighter low end, > and more definition all around). Give your amp an "oil change", it > deserves it.

Definitely.  I just look for excuses to spend money on gear so I was going to buy at least one quad of EL84’s and possibly a couple of quads to try.

Response:

> Yup..yer 2 tubes are shot.

Prolly so.  This is the only amp I own that I don’t own several full sets of spare tubes for.  And of course I paid for it last night because the tubes crapped out right as we were going to start for the night.  Luckily, being a 2 guitar band, the other guitarist was able to cover for the first set while I retrieved another amp from the house (an hour round trip).  I stopped carrying a backup amp about a year ago (because I usually carry a full tool kit and a ton of spare tubes, fuses, etc…) and I guess I was asking for it.  Time to update the spare tubes with some EL84’s.

Response:

>Time to update the spare tubes with some EL84’s.

Oh, hell yes. Gotta bring spares to the gig *alwys*, Big Odin. Don’t have any spares from even another amp or anything that you can put in there for now? Peace, Polfus Check out my website: http://www.geocities.com/PolfusPage

Response:

- Hide quoted text — Show quoted text – > I played a gig Fri night and when I started the 4th set my amp seemed > to sound "not quite right", like it had lost some volume and punch. > Considering that I’d had a few (or so) beers and it was time to play I > didn’t really stop to think about it, thinking that maybe the beer and > loud stage volume had affected my hearing and the amp was OK.  It was > a 2 nighter, so tonight when I showed up to play I was tuning and > before the gig and when I turned on the amp I noticed a low buzz > coming from the amp.  Also, it still didn’t sound quite right.  Being > sober tonight I decided to look at the tubes and I saw that 2 of the > power tubes were glowing bright, cherry red when I took the amp off > standby.  On standby everything looks normal, but switch off the > standby switch and immediately 2 power tubes glow red hot.  The amp is > a Dr Z Maz 38 Senior 2×10 combo (38 watts with 4 EL84’s).  The 2 tubes > that are glowing are the 2 on the right when looking at the amp from > the rear.  Being that the 2 tubes are side by side I assumed that one > side of the push-pull amp has a problem.  My amateur assessment is > that maybe one of those glowing tubes took a dump and it’s throwing > the other out of bias.  When I wake up tomorrow afternoon I’ll swap > the tubes and see if the problem follows.  Any other suggestions?  LV, > if this is tubes then what should I replace these 4 EL84’s with?  I’m > gonna need ‘em fast because I don’t like lugging the Tonemaster to > gigs if I don’t have to.  Thanks.

Probably one of the tubes on that side developed a bias short and pulled the other one down.  Amp manufacturers run the utter *crap* out of EL84s, so you really have to treat them like strings.  Luckily, they’re cheap – I get $18/pair for JJ, $16 for Ei, and $12 for the cheaper Sovteks.  JJs sound fine in that amp; Eis do, too, but most of ‘em are current-hogs and run hot.  I’m doing a burn right now on 250 of those, so I’ll have some low-current quads available in a week or two.  I have Sovteks and Teslas right now.  To make sure you don’t have a problem in the amp itself, swap the pairs to opposite sides. If the glow stays with the tubes, you need tubes. If it stays with the same sockets, you need repairs. Lord Valve Tone Chaperone      VISIT MY WEBSITE:  http://www.nebsnow.com/LordValve       I specialize in top quality HAND SELECTED NOS and         current-production vacuum tubes for guitar and            bass amps.  Good  prices, fast service.      QSC amps, RNC compressors, lots of other good stuff!    NBS Electronics, 230 South Broadway, Denver, CO  80209-1510 Phone orders/tech support after 1:30 PM Denver time at 303-778-1156                   VISA – MASTERCARD – PAYPAL                  "Posterity will ne’er overcome                   A nobler grave than this;                   Here lie the bones of Blumb the Dumb;                   Stop, traveler, and piss."                          - Lord Valve –           (Paraphrase of Lord Byron, on Lord Castlereagh)

Response:

Do a side to side swap and see if the problem moves with the tubes. If it does, replace tubes, like all 4. If not, suspect coupling cap or grid resistor. No telling how badly those tubes got cooked, but this wouldn’t be a bad time to replace them anyway. I don’t know if the amp is cathode bias or not. Even if it is cathode bias, check to see that they aren’t running too hot and that there isn’t another problem. Ron – Hide quoted text — Show quoted text – >I played a gig Fri night and when I started the 4th set my amp seemed >to sound "not quite right", like it had lost some volume and punch. >Considering that I’d had a few (or so) beers and it was time to play I >didn’t really stop to think about it, thinking that maybe the beer and >loud stage volume had affected my hearing and the amp was OK.  It was >a 2 nighter, so tonight when I showed up to play I was tuning and >before the gig and when I turned on the amp I noticed a low buzz >coming from the amp.  Also, it still didn’t sound quite right.  Being >sober tonight I decided to look at the tubes and I saw that 2 of the >power tubes were glowing bright, cherry red when I took the amp off >standby.  On standby everything looks normal, but switch off the >standby switch and immediately 2 power tubes glow red hot.  The amp is >a Dr Z Maz 38 Senior 2×10 combo (38 watts with 4 EL84’s).  The 2 tubes >that are glowing are the 2 on the right when looking at the amp from >the rear.  Being that the 2 tubes are side by side I assumed that one >side of the push-pull amp has a problem.  My amateur assessment is >that maybe one of those glowing tubes took a dump and it’s throwing >the other out of bias.  When I wake up tomorrow afternoon I’ll swap >the tubes and see if the problem follows.  Any other suggestions?  LV, >if this is tubes then what should I replace these 4 EL84’s with?  I’m >gonna need ‘em fast because I don’t like lugging the Tonemaster to >gigs if I don’t have to.  Thanks.

Response:

Hello Odin,     Each of us has a mental, or perhaps physical, list of what we need to take to a gig.  I always take a back-up amp when I’m not already using a multi-amp rig; also at least two guitars so I’m covered there as well.  The "list" we all maintain in some fashion may be as a result of an oversight on our parts at some time.  My story follows…     Years ago (early 70’s) I was using a full Marshall stack and I had a gig 100 miles from my home.  Packed up the vehicles and our band got there and set up.  Got the sound system arranged and did our vocal checks, and then I went to my car to retrieve my Telecaster.  Empty car.  I stood there and looked and it dawned upon me that it was at home on the living room floor, right where I’d left it as I packed my car that day.     I was able to "borrow" a guitar from someone in the audience (yes – really….) and finish the gig.  As a result of this personal experience, I have a list of what I need to take to a gig, and to some people it looks like way too much stuff.  But my philosophy is that if I have a vehicle big enough, and a two wheel, I will take amps and guitars so that I’m covered in the eventuality of something breaking, or not working correctly.     For those who scoff at this approach, all it takes is your first time of experiencing a broken or faulty component in your rig, and you’ll know what Odin and I are saying.  Boy Scout Motto:  Be Prepared.     Odin, sounds like a great amp – how might you compare or contrast that particular amp with something like a Vox AC30?  Any sense of how they may compare?     Walk in Beauty, Peace.  Scott

– Hide quoted text — Show quoted text -> Yup..yer 2 tubes are shot. > Prolly so.  This is the only amp I own that I don’t own several full > sets of spare tubes for.  And of course I paid for it last night > because the tubes crapped out right as we were going to start for the > night.  Luckily, being a 2 guitar band, the other guitarist was able > to cover for the first set while I retrieved another amp from the > house (an hour round trip).  I stopped carrying a backup amp about a > year ago (because I usually carry a full tool kit and a ton of spare > tubes, fuses, etc…) and I guess I was asking for it.  Time to update > the spare tubes with some EL84’s.

Response:

> >Time to update the spare tubes with some EL84’s. > Oh, hell yes. > Gotta bring spares to the gig *alwys*, Big Odin. > Don’t have any spares from even another amp or anything that you can put in > there for now?

Just from the Pro Jr. but that only has 2 EL84’s.  All of my gigging amps are 6L6 or EL34.  Only one of the power tubes is bad but I’ll buy a new quad and have 3 spares.

Response:

>     Each of us has a mental, or perhaps physical, list of what we need to > take to a gig.  I always take a back-up amp when I’m not already using a > multi-amp rig; also at least two guitars so I’m covered there as well.  The > "list" we all maintain in some fashion may be as a result of an oversight on > our parts at some time.

My "list" is fairly long but I stopped taking a backup amp about a year ago because I had never needed it in many years of gigs.  I used to throw the little Pro Jr in the truck just in case and figured I could limp through a gig with that amp mic’ed up.  I finally got tired of loading it and left it at home.  This wouldn’t have been a problem because I have an "emergency kit" that contains full sets of tube for a Super Reverb (or any other 6L6 Fender amp) including preamp tubes, power tubes, fuses, etc…but I never added EL84’s to that kit when I bought the Dr Z.  My own fault. >     Odin, sounds like a great amp – how might you compare or contrast that > particular amp with something like a Vox AC30?  Any sense of how they may > compare?

Well, it’s *not* an AC30 clone but it has some Voxesque qualities.  I like an AC30 very much but they don’t stay clean and tight at gig volumes and are best suited to cranked leads or medium to low volume clean stuff IMO.  The Maz 38 will stay tighter at higher volumes.  And it’s not quite as midrangey as a Vox, although you can dial in a very convincing AC30 tone if that’s your thing.  Much lighter than an AC30 but still plenty heavy.  I’ve owned a bunch of Fenders and the Maz is far from a Fender.  Same thing with Marshall, it’s not at all Marshall-like.  I’d have to say that the Dr Z amps that I’ve owned have been pretty unique sounding but this one has a more Vox flavor than Fender or Marshall but with a little more versatility and tightness.  Everything from really clean to pretty overdriven is easy to dial in, but nothing heavy like a Mesa, etc.

Response:

> Probably one of the tubes on that side developed a > bias short and pulled the other one down.  Amp > manufacturers run the utter *crap* out of EL84s, > so you really have to treat them like strings.  Luckily, > they’re cheap – I get $18/pair for JJ, $16 for Ei, and > $12 for the cheaper Sovteks.  JJs sound fine in that > amp; Eis do, too, but most of ‘em are current-hogs > and run hot.  I’m doing a burn right now on 250 of > those, so I’ll have some low-current quads available > in a week or two.  I have Sovteks and Teslas right > now.  To make sure you don’t have a problem in > the amp itself, swap the pairs to opposite sides. > If the glow stays with the tubes, you need tubes. > If it stays with the same sockets, you need repairs.

When I woke up and recovered this afternoon I swapped the tubes – problem stays with the tubes.  One of the tubes has the logo burnt dark brown so I guess that’s the culprit.  The stock tubes are GT EL84S with a numerical rating of "5".  I guess I’d like to buy a quad of your best EL84’s for this amp, whatever that might be.  Got any good NOS stuff for this amp or would the JJ’s be about right?  I’ll call you with the order tomorrow and I’ll still have the tubes before the weekend.  Guess I’ll keep the remaining GT’s for spares.

Response:

- Hide quoted text — Show quoted text -> Probably one of the tubes on that side developed a > bias short and pulled the other one down.  Amp > manufacturers run the utter *crap* out of EL84s, > so you really have to treat them like strings.  Luckily, > they’re cheap – I get $18/pair for JJ, $16 for Ei, and > $12 for the cheaper Sovteks.  JJs sound fine in that > amp; Eis do, too, but most of ‘em are current-hogs > and run hot.  I’m doing a burn right now on 250 of > those, so I’ll have some low-current quads available > in a week or two.  I have Sovteks and Teslas right > now.  To make sure you don’t have a problem in > the amp itself, swap the pairs to opposite sides. > If the glow stays with the tubes, you need tubes. > If it stays with the same sockets, you need repairs. > When I woke up and recovered this afternoon I swapped the tubes – > problem stays with the tubes.  One of the tubes has the logo burnt > dark brown so I guess that’s the culprit.  The stock tubes are GT > EL84S with a numerical rating of "5".  I guess I’d like to buy a quad > of your best EL84’s for this amp, whatever that might be.  Got any > good NOS stuff for this amp or would the JJ’s be about right?  I’ll > call you with the order tomorrow and I’ll still have the tubes before > the weekend.  Guess I’ll keep the remaining GT’s for spares.

Like I said, treat ‘em like strings.  NOS EL-84s don’t last significantly longer or sound significantly better than the currently-maunfactured ones.  JJs are fine for that amp. The price/performance ratio for NOS EL84s is terrible. Lord Valve Asshole

Response:

> NOS EL-84s don’t last significantly longer or sound significantly better than

the currently-maunfactured ones.> I disagree, sir. Peace, Polfus Check out my website: http://www.geocities.com/PolfusPage

Response:

That’s one sorry ass web site.

– Hide quoted text — Show quoted text -> NOS EL-84s don’t last significantly longer or sound significantly better than > the currently-maunfactured ones.> > I disagree, sir. > Peace, > Polfus > Check out my website: > http://www.geocities.com/PolfusPage

Response:

To be more specific, pix of people using Lp’s (woop de fucking do), annoying popup ads,  kind of just a general jerk-off session. Just my two plow puss cents.

– Hide quoted text — Show quoted text -> That’s one sorry ass web site. > > NOS EL-84s don’t last significantly longer or sound significantly better > than > the currently-maunfactured ones.> > I disagree, sir. > Peace, > Polfus > Check out my website: > http://www.geocities.com/PolfusPage

Response:

Hello Odin,     Thanks for the follow-up.  I’ve heard nothing but good comments about Dr. Z amps and I’m happy that you got one.  Have fun playing guitar.  Take care.     Walk in Beauty, Peace.  Scott – Hide quoted text — Show quoted text ->     Each of us has a mental, or perhaps physical, list of what we >need to > take to a gig.  I always take a back-up amp when I’m not already >using a > multi-amp rig; also at least two guitars so I’m covered there as >well.  The > "list" we all maintain in some fashion may be as a result of an >oversight on > our parts at some time. >My "list" is fairly long but I stopped taking a backup amp about a >year ago because I had never needed it in many years of gigs.  I used >to throw the little Pro Jr in the truck just in case and figured I >could limp through a gig with that amp mic’ed up.  I finally got tired >of loading it and left it at home.  This wouldn’t have been a problem >because I have an "emergency kit" that contains full sets of tube for >a Super Reverb (or any other 6L6 Fender amp) including preamp tubes, >power tubes, fuses, etc…but I never added EL84’s to that kit when I >bought the Dr Z.  My own fault. >     Odin, sounds like a great amp – how might you compare or >contrast that > particular amp with something like a Vox AC30?  Any sense of how >they may > compare? >Well, it’s *not* an AC30 clone but it has some Voxesque qualities.  I >like an AC30 very much but they don’t stay clean and tight at gig >volumes and are best suited to cranked leads or medium to low volume >clean stuff IMO.  The Maz 38 will stay tighter at higher volumes.  And >it’s not quite as midrangey as a Vox, although you can dial in a very >convincing AC30 tone if that’s your thing.  Much lighter than an AC30 >but still plenty heavy.  I’ve owned a bunch of Fenders and the Maz is >far from a Fender.  Same thing with Marshall, it’s not at all >Marshall-like.  I’d have to say that the Dr Z amps that I’ve owned >have been pretty unique sounding but this one has a more Vox flavor >than Fender or Marshall but with a little more versatility and >tightness.  Everything from really clean to pretty overdriven is easy >to dial in, but nothing heavy like a Mesa, etc.

Response:

>To be more specific, pix of people using Lp’s (woop de fucking do), annoying

popup ads,  kind of just a general jerk-off session.> >Just my two plow puss cents.

And that’s what it is worth.

Response:

Still infinitely more than zero.

– Hide quoted text — Show quoted text ->To be more specific, pix of people using Lp’s (woop de fucking do), annoying > popup ads,  kind of just a general jerk-off session.> >Just my two plow puss cents. > And that’s what it is worth.

Response: