Blackface Bassman Experts Help! (AA864 Circuit Questions)

Discussion in 'Amps and Cabs' started by dumb donnie, Jun 16, 2005.


  1. dumb donnie

    dumb donnie Member

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    I have the opportunity to buy a Blackface Bassman with an AA864 circuit. I have been told that these are the best sounding and rarest of the Bassman circuits.

    -I previously owned an AB165, what will the difference in sound be?

    -Should I be worried about the reliability of a 40 year old amp?

    -Any comments on about the originality/authenticity of the circuit?

    -Any comments on the AA864 in general, any recommended mods (it already has a 3 prong chord)?

    -How well will it take to fuzzes, anywhere as well as a Marshall?

    -Finally, about how much should I be looking to pay, what would be a good price?
     
  2. John Phillips

    John Phillips Member

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    Actually the AA165 is the rarest (made for less than one month in Jan '65), but the AA864 is rarer than the AB165 - made for only four or five months in late '64 to the start of '65.

    I've owned and directly A/B'd both these too - I found the AA864 to be more dynamic and open on the normal channel (about the same on the Bass, but you won't really be needing that ;)), and much more 'balanced' sounding when pushed really hard - the AB165 has an odd split-bias arrangement, and to me sounded both too squashed and a bit uneven and farty. The AA864 was just big, gritty and crunchy.

    No, because...

    ... that amp looks like it has been correctly and professionally overhauled - 3-wire cord, all electrolytic caps replaced, and the screen-grid resistors replaced with better modern types. You can't see the main filters, but since all the caps in the main chassis have been done, it would be surprising if they haven't as well. Everything else looks stock. That's the right way to do it :).

    No! Leave it alone! It's the best-sounding amp Fender ever made IMO :). And that one is in unusually nice condition.

    Better. Mine was extremely pedal-friendly. Just the right combination of power and clarity.

    I can't help with this one, sorry - except to say BUY IT. These amps are very undervalued by vintage-Fender standards. Did I say I regret selling mine? :( I got £450 ($800 or so) for it about five years ago, which was a good price for the UK at the time, but in hindsight I should have kept it.
     
  3. tonezoneonline

    tonezoneonline Member

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    From the parts used and the work done I beleive that is an amp that I owned and serviced.If so it is in very good shape and there is no need to worry about it failing.If I'm correct it will have new Sprague Atom electrolytics also.
    I would buy the amp either way if it's what you want and the price is fair.They are getting harder to come by these days and I have always thought the prices were low for what you get.
     
  4. sundaypunch

    sundaypunch Member

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    Here's a great link for you to explain the difference between the AB165 that you had and the AA864- AA864 vs. AB165

    First you should verify that it's actually an AA864. Many of these are actually AA165's and many with the AA165 chart are actually AB165's. Fender had a habit of using old charts until they ran out. I play a June '64 blonde 6G6-B Bassman and it actually has about half of the AA864 mod's incorporated.

    Either way the AA864 and AA165 are similar to each other and more desirable than the AB165. Don't screw with a AA864 or AA165 amp and mod it :mad: That's what AB165's are for :) I wouldn't worry a bit about reliability. Of course you should have it checked out by a tech and replace any old caps. I see your bias supply cap has been replaced so your filter caps (under the pan) likely have already been done. If your caps are good and the basics are taken care of you should be fine.

    Soundwise it's a fantastic amp. Great cleans and great crunch if you crank it up a bit. It won't quite get you to Marshall land, you can come close with Celestions in the cabinet but you won't quite have the mid's you need. I personally like it just as well. The blondes will come a bit closer. My 6G6-B is great with pedals, my favorite amp of all time. I don't know what to tell you price-wise as I pretty much stick to the blondes. Have you checked the ebay completed auctions?
     
  5. sundaypunch

    sundaypunch Member

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    Disregard my last post, I should say "yeah, what John said" :)
     
  6. dumb donnie

    dumb donnie Member

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    Thanks for all the replies, you guys have helped me out a lot! Just a couple more things for now. First, what are the tonal differences between the AA864 and the 6G6? How easy is it to bias one of these at home?
     
  7. sundaypunch

    sundaypunch Member

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    6G6-B is just a bit more raw sounding w/ slightly more mid's to my ear. Kind of in between the tweeds and BF amps. You won't be biasing one at home since it doesn't have a bias pot. Most people have a tech solder a small pot inside the amp which isn't a big deal.

    Don't quote me on this but I think the AA864 is the first one that went to the adjustable bias pot. You can buy a "bias rite" or similar to adjust it on your own. It's handy to be able to do it. I find that swapping power tubes in mine has a big effect on gain / headroom.
     
  8. dumb donnie

    dumb donnie Member

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    One more thing, I just recently read about swapping the 6L6's for EL34's, is this safe? Has anyone here ever attempted such a feat? The guy that swapped out the tubes said that there was increased headroom (and some other tonal changes) and that the amp jumped up by 15w or so.
     
  9. sundaypunch

    sundaypunch Member

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    It's got 6L6's, not EL34's. I don't know anyone that would put EL34's in a Bassman.
     
  10. dumb donnie

    dumb donnie Member

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    I know that it's usually 6L6's, but this guy reported some nice sounding results with the EL34's.
     
  11. Shemp

    Shemp Member

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    I had my 68 SF Bassman with an original AB165 circuit modded to 1/2 AA864, 1/2 AB165 "The Andy Ruhl Mod" Gives me the grind of the original BF circuit and the cleaner 1/65. I use an ABY box with it. Great amp. They must have built a million of them because prices haven't moved that much.
     
  12. doctorx

    doctorx Member

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    Like John said, this amp looks to have been tuned up properly, caps, etc. It should sound awesome.

    I have a 67 BF Bassman, I love it.

    You can't put EL34's into a Fender without mods to the power tube sockets. I did this to my SF Bassman tops and really liked it, although I have since gone back to 6L6's.

    This amp of yours has adjustable bias, put JJ's or Winged C power tubes in it and bias it hot (usually around 40-43 milliamps), and dime it through a 4x12. That's rock and roll.

    About the price, probably around $600-$700. People usually ask stupid money for these, though.
     
  13. dumb donnie

    dumb donnie Member

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    Ok, I came up with yet another question :eek:. Has anyone put 7581a's into a Bassman? I only recently heard about these tubes, from what I know they will increase the bass response and add a little headroom. I was just interested to see if this has been done, and if so, is it recommended for something a little different.
     
  14. Shemp

    Shemp Member

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    They'll work. I run them in a Carr Rambler. In the bassman they'll need to be biased.
     
  15. Swarty

    Swarty Member

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    The 7581 is just a real good 6L6GC. If it is the Sylvania/Philips variety, it is the same as their big bottle 6L6GC that many companys put their name on the late '70s and '80s; Fender, Peavey, Groove Tube, etc...

    FWIW, the AB165 has the dubious distinction of being the first amp to recieve CBS era "enhancements" by virtue of that bias balancing control. Other amps didn't get this fine "feature"until about 2 years later.
     
  16. Reactionjackson

    Reactionjackson Member

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    7581's are the industrial rated tube that are very similar to 6L6GC's (so they can handle a decent amount of voltage). I beleive they also have the same specs as their European couterpart -- the KT-66. I think the 'a' suffix simply connotes a higher plate handling rating
     
  17. phoenix

    phoenix Member

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    While we wait for more answers...

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  18. dumb donnie

    dumb donnie Member

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    Nice :cool:.
     
  19. dumb donnie

    dumb donnie Member

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    Ok, one more question for John Phillips or any other vintage Bassman/Fender expert. This is another AA864 Blackface Bassman head, but the caps are all big and orange.

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    Those can't be original, can they? Many thanks to everyone that has tossed in advice and information.
     
  20. dumb donnie

    dumb donnie Member

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    Oh, and one more thing that I have been wondering. Do you think you could squeeze more tone out of a stock AA864 or a 6G6-(A/B) or a modded AB165? Could you tune up the AB165 and make it better than an AA864 or Blonde head?
     

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