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Do power tubes have to be pushed to show their characteristics?

Discussion in 'Glowing Bottle Tube Amp Forum' started by 3-Chord-Genius, Sep 23, 2017.

  1. 3-Chord-Genius

    3-Chord-Genius Friend of Leo's

    Apr 3, 2015
    Winchester, VA
    I have a Vox AC10C1 that exhibits a muddiness on the low E string when the preamp is overdriven. This does not happen when using an overdrive pedal, and it happens with both the stock Chinese preamp tubes and the Tung Sol preamp tubes that I replaced them with. The only other thing I can think of is that it's the power tubes, but I don't play this amp very loud. If the power tubes suck, would it be apparent at low volumes?
     

  2. Richie-string

    Richie-string Tele-Meister

    For the price of two extra tubes it maybe worth replacing the output tubes. I was surprised how much of a sound difference upgrading all the tubes in my AC4c1 made, having said that any tube is always going to sound more lively with the tubes pushed a bit.
     

  3. Dacious

    Dacious Friend of Leo's

    Mar 16, 2003
    Godzone
    Where is your bass eq set? If you have bass and volume set high you can expect bass fartiness on any amp in some circumstances.

    Also, many people don't understand the FMV tone stack where gain is in front of eq that the treble control is a 'master eq' setting. Too much gain along with too much treble will produce too much mids and bass, even with those controls wound back because you're already distorting the signal. Running everything on 11 sounds like a cool thing in a spinal tap kinda way but many amps won't actually accept that without undesirable results unless you are going for ugly distortion.. in the Plexi world of non-MV amps with tight power and output sections i.e massively specced transformers maybe.

    IIRC the AC10 uses a Topboost channel. There's limits to how you can run it and get good tone.
     
    3-Chord-Genius likes this.

  4. alnicopu

    alnicopu Friend of Leo's

    Oct 3, 2009
    georgia
    What you are describing could be solved, or at least made better, by a speaker swap. Do some research and roll some speakers.
     
    3-Chord-Genius likes this.

  5. brokenbones

    brokenbones Tele-Meister

    209
    Mar 15, 2012
    Indy
    To answer your question, no. A pair of NOS RCA power tubes will be distinct at any volume. My Vox AC15C1 had a low end muddiness problem at volume. Like Dacious suggested, study the preamp tone stack circuit and how it responds to gain. Chox's would probably benefit the most from a preamp tube upgrade along with a new speaker. I tried lowering pickup height on the low side.

    This will help as well. https://tonesmiths.wordpress.com/2013/03/28/the-secret-to-quickly-dial-in-a-tube-amplifier/
     
    Tootle and 3-Chord-Genius like this.

  6. 3-Chord-Genius

    3-Chord-Genius Friend of Leo's

    Apr 3, 2015
    Winchester, VA
    I'd never heard of that technique for setting up an amplifier before. I'm going to try that after everybody wakes up.
     

  7. Deeve

    Deeve Tele-Afflicted Silver Supporter

    Dec 7, 2009
    Ballard
    Why wait?

    At my house, I just make toast [smoke alarm loses its mind, cats lose their minds, soon Mrs Deeve comes downstairs w/ homicide in mind - it a weekend morning and sun's not up yet. . . ]

    Peace (and quiet) - Deeve
     

  8. codamedia

    codamedia Friend of Leo's

    Apr 4, 2009
    Western Canada
    IME.... all tubes sound the same (or very similar) before they get pushed. It's when they are pushed beyond their limits (which is what guitar players like to do) they start to break down. Some tubes fall apart (tone wise) and some come to life!
     

  9. 3-Chord-Genius

    3-Chord-Genius Friend of Leo's

    Apr 3, 2015
    Winchester, VA
    Yeah, I asked because I'm trying to pinpoint an issue with flubby distortion on the low E string. Two different guitars. I don't hear it on demos of the amp, just mine. I already replaced the preamp tubes, and I don't know if the EL84s would cause any issues unless they're pushed hard, and I never run my amp like that.
     

  10. chris m.

    chris m. Friend of Leo's

    Some good advice here-- optimize your tone settings, gain, and volume, see how far you get. Speaker makes a big difference-- maybe try some other cabinets. In my experience tubes make a difference, but they are more subtle than the first two things. Finally, circuit design matters most of all. That's the biggest reason why different amps sound different-- not because they are sporting different types of power tubes, but because of everything else, actually.
     

  11. Ricky D.

    Ricky D. Poster Extraordinaire

    Age:
    66
    Oct 22, 2006
    Garner, North Carolina
    Just by instinct, flubby lows could indicate the power supply starving out. My 5e3 sure behaves that way if I push the low end. Maybe someone with more knowledge of your amp could weigh in.
     
    3-Chord-Genius likes this.

  12. screamin eagle

    screamin eagle Friend of Leo's

    Oct 9, 2008
    S. CA
    I agree with this, even though I've forked out $$ for NOS tubes (but from reputable dealers who what to know how I intend to use them and in what).

    As an electric guitarist, we play amps and the amps sound comes out of the speaker. The circuit and the speaker make the most difference. Tweaking the tone stack by turning the knobs or tweaking the circuit is where the tone changes. Sure tubes have an impact to some degree, but not like the amp circuit.

    I get together with a group of buddies a few times a month and jam for a couple of hours. There's a neighborhood kid who comes by and plays with us from time to time (all swing tunes). He plays an Epi Sheraton. He always plugs into one of our amps (never brings his--ours are some variety of tweed amps) and is always boomy. I have a 335 and played through the same amp isn't boomy. Some of it is technique and listening and some of it is the pickup and/or pickup height.

    Point of this is that it may be your technique with your guitar that is exacerbating the boominess and maybe a little control would go a long way (as in not cost you money).
     
    teletimetx and 3-Chord-Genius like this.

  13. badvoodoo

    badvoodoo TDPRI Member

    35
    Jan 25, 2007
    Oshawa, ON
    I bought a used Traynor YGL-1 from Long and McQuade. When I got the amp, I found that it had a microphonic pre-amp tube and that someone had replaced all the original tubes with Sovteks. I replaced the power tubes with Mesa EL-84s and replaced the pre-amp tubes with Mesa 12AX7s (with a 12SPX7 in the V1). I really liked the sound of the amp, but the "pure" channel that bypasses the tone stack always sounded muddy. Yesterday I tried an Electro-Harmonix 12AX7EH in V1 and moved the 12SPX7 to the V2. The pure channel sings now and over all the amp has a much better tone with sparkling highs, buttery mids and crisp lows.

    So yeah... A tube change could make a major difference on the overall tone of your amp. If you had heard what my amp sounded like when I got it to what it sounds like now, you wouldn't believe it was the same piece of equipment. The only modifications I have done is swapping the tubes. I have read that because of the nature of tubes themselves, slight differences in design can respond differently to different amplifier circuits and ultimately the sound they produce. So while a Tung-Sol may sound awesome in my amp, it may not be the best choice for yours. I would experiment with a few of the highly rated brands (JJ, Electro-Harmonix, Mesa, etc.) and see if that corrects your problem.
     
    3-Chord-Genius likes this.

  14. Silverface

    Silverface Poster Extraordinaire Platinum Supporter

    Age:
    65
    Mar 2, 2003
    Lawndale CA
    It may be. but most amps suck at low volume , partially because the speakers are not reaching full frequency response. But if you are overdriving a preamp and running the power amp low the tone usually sucks period. Preamp-only overdrive does not sound like a cranked amp - it sounds like a cranked preamp , which is usually limited in range, may sound muffled or buzzy and nearly always lacks punch. Doesn't matter how good the power tubes are if you inject a bad sounding signal into them.

    It will also sound different than an overdrive pedal - although "overdrives" are not necessarily that good at providing distortion, if that's what you're doing. IMO most "overdrive" pedals sound far better doing what the name suggests - hitting the front end of a cranked amp hard enough to overdrive it (meaning the preamp and power amp) - which requires a cranked tube amp running near the limit of headroom. That's usually the best overall sound.

    But for distortion I prefer distortion pedals.
     
    3-Chord-Genius likes this.

  15. chris m.

    chris m. Friend of Leo's

    I agree with Silverface. You can't really assess the sound of your amp without turning up into its sweet zone. And many amps just won't sound very good at all when dropped below their sweet zone,although some are much better than others. If it sounds so-so in the sweet zone then by all means try some tweaks. But if it sounds great when cranked and then not so much when turned down your best bet may be a good pedal. I personally am able to get very workable tones at lower, bedroom volumes by using pedals, but on the other hand I don't have real high expectations. I'm just looking for a serviceable tone that allows me to rehearse. As long as I sound good on stage then I'm happy with my amps. There's also a big factor of the human ear. Distortion tends to sound buzzy at lower volumes and much more glorious when cranked up so there's a bit of air moving around.
     

  16. 3-Chord-Genius

    3-Chord-Genius Friend of Leo's

    Apr 3, 2015
    Winchester, VA
    What I'm getting at is that I suspect a characteristic I'm hearing at low volume is power tube related because I already replaced the preamp tubes, but I don't know if power tubes would act up at lower volume levels.
     

  17. Silverface

    Silverface Poster Extraordinaire Platinum Supporter

    Age:
    65
    Mar 2, 2003
    Lawndale CA
    "Act up" - generally, no. If they are going to demonstrate issues it's normally at higher volume/vibration levels.
     
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  18. Frodebro

    Frodebro Doctor of Teleocity Ad Free Member

    Age:
    47
    Aug 17, 2012
    Seattle
    My Mark V can run either 6L6s or EL34s. There is a quite noticeable difference between the two, even at lower volume levels.
     

  19. Dacious

    Dacious Friend of Leo's

    Mar 16, 2003
    Godzone
    That's because of the nature of the tubes - a pentode like the EL34 or EL84 acts with a secondary emissions grid to control power for a fairly even response; whereas the 6V6 or 6L6 'beam' plates produce a marked lower-mid hump, used to advantage in many Fenders but particularly BF 'scooped' design.

    For the OP - your issue with farting is, the notes that take the highest power to push out clean are bass notes. A bass open bottom E, the sine wave coming off the speaker is 39 feet long......

    Hence bass amps and PA subs run hundrrds of watts and you run them on 5 or 6.

    Many of our guitar amps, to get breakup we want to saturate the output section and or speaker. And guitar amps are designed to be adjustable, bearing in mind early pickups like a Charlie Christian bathtub might be lowish output. Or a horseshoe Ric lapsteel.

    Leo and Dick Jennings and even Jim Marshall didn't design their amps originally to break up - Fender allegedly hated Rock'n'Roll.

    You were meant to turn your amp up 'so far' like Les Paul or Chet Atkins for nice clean to get over the band. And you got eqs to adjust your treble, bass mids to get a nice sweet tone at different volumes. As the volume control also cuts frequency response you could put back treble, mids, bass. But you were never intended to run them all dimed.

    Leaving aside problems with hardware, if your volume goes up, usually mids and bass at least must go down the louder you get - or as someone noted above, the tubes are trying faithfully to amplify millivolts into volts and they run out of steam. Then they clip. A little clip, most people agree is nice. To much clip sounds like buzzsaw.

    You can mitigate this with better tubes and efficient speakers to some degree. Turn the amp up more because the tubes/speaker use the power better.

    When Leo Fender created his Deluxe amp originally it was a straight lift from something like a Western Electric or RCA manual for a general amplifier for radio, PA, record player. You bought the tubes, the manual showed you how to build the amp. Hence he included fat bypass caps that partly give that amp it"s flubby distortion. But get it in the sweet spot where it's just clipping and it sounds great and gnarly.

    The more you push volume, the braapier and ruder it gets. Same with the Tweed Champ.

    So - there may be nothing wrong with your amp, you're just asking of it what it can't do.

    When I gigged or band-practiced with my SF Princeton Reverb, I typically had volume on 6-7, treble on 6-7, the preset mid resistor set mids to about 5-6, bass on 3-4. At that level with guitar on 8-9, it was just on the edge of nice singing breakup and a cutting tone. With that P/t, power section, o/t and speaker combo it was just right for unmicced school hall gigs for old rock'n'roll with bass and drums. Any more bass, the low end became unpleasant and farty on the E and A strings.
     
    Last edited: Oct 4, 2017

  20. jannodude

    jannodude Tele-Meister

    Age:
    27
    408
    Aug 10, 2016
    SF Bay Area/California
    I have an AC10 myself with a 16 ohm Red Fang speaker. I have to really work the settings on the amp to find a good tone. Until then, it is challenging to use - pedal to "drive" the amp. I notice it's sweet spot for our amps is very loud (at least for bedroom levels).
    I cut back about 20% my volume/tone settings on my guitar which helps with achieving a desirable tone that I can work with.

    Edit: I did had some flubbiness on the G string before I swapped the tubes for JJs.
     
    Last edited: Oct 4, 2017

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