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Blonde Fender Bassman - Mismatched Impedance

Discussion in 'Glowing Bottle Tube Amp Forum' started by DannyStereo, Apr 10, 2018.

  1. DannyStereo

    DannyStereo Poster Extraordinaire

    Aug 13, 2014
    Kelso, Washington
    1523380987399.jpg

    Hey Fellas! Been a while since I've posted. In that while, I've done quite a bit of trading (Imagine THAT) and have developed quite a nice little collection. I'll maybe post a rig shot in another thread...

    Part of that collection is a 1963 Bassman Head (6G6b) that I got with the head cab as well as a combo cab. The previous owner was running it as a combo, but I think it looks much more badass in its original head format.

    I have two Dr. Z cabs, a 2x10 with Z labeled speakers and a 2x12 with an Alnico Blue and a V30, both rated at 8ohms (two 16ohm speakers in parallel). The Bassman sounds GLORIOUS through the 2x12, and pretty dang good through the 2x10.

    My question is this: can I safely run the Bassman through an 8ohm load? Or, should I stick with the 4ohm speaker the previous owner provided with the 1x12 combo cab? It's an OEM Eminence 12" rated at 70 watts, but it doesn't have the same "sparkle" as the Z cabs.

    I do NOT want to put the head in there permanently, as I haul two amps to church every weekend (hence the Stereo in Danny Stereo). That's the entire reason I went to to cabs and heads (Dr. Z Maz 8 and Carmen Ghia are my other two heads).

    The Bassman is pretty much a dream amp for me, so I don't wanna ruin it or hurt it in any way.

    Thoughts?
     

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  2. waparker4

    waparker4 Doctor of Teleocity Ad Free Member

    Nov 9, 2011
    Philadelphia, PA
    Last edited: Apr 10, 2018
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  3. DannyStereo

    DannyStereo Poster Extraordinaire

    Aug 13, 2014
    Kelso, Washington
    It seems like there's some disagreement. Some say a step "up" to 8ohm is safe, some don't...

    Btw, nice to hear from you man!
     
  4. 2 Headed Goat

    2 Headed Goat Tele-Holic

    921
    Jul 28, 2012
    Here & Now
    You're better off keeping to the 4 ohm cab IMO esp with a vintage amp like that. Tube amps want to see a load and going 'up' to 8 ohms is supplying less of a load so the output transformer is being subjected to more current than it would be with the proper load. It could be safe playing at low volume were the output section isn't being pushed hard but I personally wouldn't play it live that way for an extended period of time.
    My .02.
     
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  5. Tomm Williams

    Tomm Williams Tele-Holic

    781
    Jun 11, 2016
    USA
    I have a 64 blonde also with two cabs, one is 8 the other is 4. I run them together with a Weber Z Matcher. No more worries for any of my multiple amps and cabs.
     
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  6. DannyStereo

    DannyStereo Poster Extraordinaire

    Aug 13, 2014
    Kelso, Washington
    Interesting. Thanks fellas. I think I may just run it with the 4ohm 1x12 then. At least until I source a proper 2x12. I could find a 16ohm 2x12 and re-wire it in Parallell to 4ohm, yeah?
     
  7. Dacious

    Dacious Poster Extraordinaire

    Mar 16, 2003
    Godzone
    It won't hurt it running into 8 ohms. Fenders are designed to tolerate a 100% mismatch and higher impedsimp is better than lower. The 4 ohm Emi probably isn't a stellar speaker and may be a bass unit. I'd be inclined to swap that can for a 2 X 8ohm 210 or 212 box to get the best from that amp.
     
  8. Mouth

    Mouth Tele-Holic

    Age:
    47
    634
    Feb 13, 2018
    U.S.
    2 16 ohm speakers would get you to 8 ohms, but not 4 ohms.
     
  9. DannyStereo

    DannyStereo Poster Extraordinaire

    Aug 13, 2014
    Kelso, Washington
    Yes that's what I meant. Two 8ohm speakers in parallel. Lol. Been a long day here
     
  10. DannyStereo

    DannyStereo Poster Extraordinaire

    Aug 13, 2014
    Kelso, Washington
    Here's what Eminence had to say when I sent in the info on the label -

    "Yes, it is a lead guitar driver. 150 Watt. 4 ohm, rare for a guitar driver. These were made in 2005."

    It's a pretty flat speaker. Not a lot of character.
     
  11. Mouth

    Mouth Tele-Holic

    Age:
    47
    634
    Feb 13, 2018
    U.S.
    Then yes. You can also wire it with 2 jacks and switching that will get you 4 or 16 or 2 8's in stereo.
     
  12. Dacious

    Dacious Poster Extraordinaire

    Mar 16, 2003
    Godzone
    4ohm speakers tend to be very spiky due to short voicecoil. Celestion's preferred has always been 16 ohm partly for that reason.

    That is sort of before Emi started selling branded speakers and was probably built to price rather than sonics, likely low efficiency too.

    I would bet that came out of some solid-state amp.

    Fender supplied 112s and 115s with some amps, but they were 8ohm or the amp had an alternate 4 ohm tap.
     
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  13. DannyStereo

    DannyStereo Poster Extraordinaire

    Aug 13, 2014
    Kelso, Washington
    Actually THIS would probAbly be best case scenario. I could use botg my Z heads with one cab in stereo or the Bassman mono
     
  14. Wally

    Wally Telefied Ad Free Member

    Mar 17, 2003
    Lubbock, TX
    That Bassman OT was designed for a 4 ohm load or for a 2 ohm load using the extension spkr jack to run a secondary 4 ohm load. If one has two 8 ohm load speakers/cabs, then those in parallel would yield an ideal 4 ohm load.
    There is a lot of debate about mismatching. Fender provided for the 50% mismatch to the low side, so I accept that as safe. I do not mismatch to the high side due to the possibility of fly back voltage doing damage to the OT secondary windings....especially if the amp is pushed. This type of damage does not necessarily make itself catastrophically apparent as an OT can continue to function with such damage, albeit with reduced output and sonics that are not what they once were.....to varying degrees depending on the amount of damage.
    Tube amps prefer matched loads, and that is I prefer in any situation. The output, sonics, and safety are optimized.

    Many people get solid state confused with tube amps when dealing with loads. In solid state, going higher than the stated minimum impedance is always safe....but the power output is definitely reduced. In solid state amplification, using less than the design minimum load impedance will burn the output transistors up in short time.
     
  15. DannyStereo

    DannyStereo Poster Extraordinaire

    Aug 13, 2014
    Kelso, Washington
    Interesting. I don't have the capability not the need to run both cabs - that's a WHOLE lotta amp! So I'm continuing the quest for a proper match.
     
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  16. schmee

    schmee Friend of Leo's

    Jun 2, 2003
    northwest
    I run my later Bassman with 8 ohm load all the time. Now days it's for outside gigs with a big EV15. I had one years ago that I did also for clubs. It's one of the few amps I like that way. Having said that, I'm not sure if the blonde's have the same trannies etc, and I'd be prone to getting the right load for it if you are going to use it a lot.
     
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  17. telemnemonics

    telemnemonics Doctor of Teleocity

    Age:
    59
    Mar 2, 2010
    Maine
    Well all technical info aside, Bassman heads have regularly been put in 1x12 combo cabs and run for years with 8 ohm loads.

    Here I'd guess that two amps in church are going to be run at low volume, which AFAIK is less stressful on the OT.
    I'd do it, though that is no guarantee it's safe.
    If you have or are a tech, it might be worth checking the OT to make sure it's not shorting already.

    I have an old Weber 4 ohm Jensen copy I bought used for exactly this, but it is the high power version and notoriously hard to break in. Have not used it and don't know how it will sound once broken in.
     
  18. Wally

    Wally Telefied Ad Free Member

    Mar 17, 2003
    Lubbock, TX
    Understood.. one wonders how these piggyback amps get separated from their cabinets and vice-a-versa. I have the short-lived ‘intermediate’ size BF Bassman cab....it’s longest measurement is vertical but it is not as large as the cab that came out with the SF cosmetics in April, 1967. These intermediate-sized cabs were built for the first few months of April, 1967. I bought it for the Jensen C12N’s that were in it....but then decided to resurrect the cab. Now...why did I do that??? LOL....probably a waste of time. The BF Bandmaster Head I have won’t fit on it...the Bassman cab is narrower than the Bandmaster’s. I don’t have a BF Bassman Head that will fit there. No one wants to buy a cab that large even if it has matching dates with OEM C12N’s in excellent condition with original cones.
    I have the same problem with a 4x12 Ampeg cab that sat under a V2 Head, which I have never seen. Hey, if a person traveled with say 3-4 small amps, such a cab would make a cool road case for those amps, the effects, the cables....... eeeehaw.....
     
  19. DannyStereo

    DannyStereo Poster Extraordinaire

    Aug 13, 2014
    Kelso, Washington
    Yikes. Sounds like a heifer! Lol

    I think a matching vintage correct cab would be killer, be it a 1x15 or 2x12, but that's a little outside my budget. Alright, a LOT outside my budget right now. Lol

    In the meantime I'll keep on the lookout for a 16ohm cab I can rewire to 4ohm.
     
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  20. DannyStereo

    DannyStereo Poster Extraordinaire

    Aug 13, 2014
    Kelso, Washington
    Yeah I definitely wouldn't run it above 3 or 4, though we do have the amps isolated. I do use some combination of low to high gain drives (JHS Ruby Red, Walrus Voyager, Messner, Iron Horse, or Jupiter), so there's that to keep in mind.
     
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