The BF Bassman Mods Thread

Discussion in 'Amps and Cabs' started by dspblues, Feb 6, 2008.


  1. dspblues

    dspblues Silver Supporting Member

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    What are some of the mods that are done to the black face bassman? I know there's one that makes it sound more Marshally, one that Dumble did.. what else is there? Details on what the mod is, how it's done, clips??
     
  2. blackba

    blackba Supporting Member

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    I did this mod: http://acruhl.freeshell.org/mga/main/AA864_vs_AB165.html

    It was easy except for dealing with the putting a 100ohm resistor in series with a hidden wire. For the bass instrument channel I changed the 1500ohm resistor and cap in parallel to a 820ohm and .1uF cap. (These are located at the edge of the board, farthest away from the power tubes.

    I have been tracking down a hum issue, but overall I like the mods, particularly on the bass instrument channel.

    Mine is a '67 silverface AB165 circuit stock...
     
  3. dspblues

    dspblues Silver Supporting Member

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    Come on guys, 1 reply?? :)
     
  4. blackba

    blackba Supporting Member

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  5. Texsunburst59

    Texsunburst59 Member

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    Hey Warren, the one mod I like and have done to several of my Bassman amps is the Allen/master volume mod.All that is done to the bassman is detailed below, and then my amp guys adds a master volume to the Bass side to have gain control over the Tweed and Plexi tones.Here's a clip of the amp in action using the Plexi tone. There are many more examples of the modded Bassman on my soundclick page,but just have to go through and check them out.

    http://www.soundclick.com/bands/page_songInfo.cfm?bandID=633883&songID=5736046

    Here's what was done to the Bassman:

    BassmanĀ® Head conversion - there are lots of 65-70 BassmanĀ® heads with the odd AB165 circuit which was quite a departure from traditional Fender circuits. The BASS channel is not really voiced well for guitar and is often not used. This conversion rebuilds the entire circuit board so the NORMAL channel is the more desirable AA864 circuit (about like the NORMAL channel of a Super Reverb) and the BASS channel becomes a really cool lead channel with a tweed/Plexi flavor to it. The DEEP switch goes between the huge cathode bypass capacitor associated with the 5F6A Bassman to the much smaller capacitor used with the Marshalls. This channel has an extra gain stage, is more aggressive and has more harmonics for a great lead channel. You can use an A-B switch to switch between the two channels with each having its own volume and tone controls. It makes a much more usable amp for guitar. Many end up preferring the BASS channel to the classic tone of the NORMAL channel. The conversion is $199 plus anything else that might be needed as part of normal service such as new filter capacitors, tubes, grounded power cord etc. I have done several of these and they are very popular. The modifications are reversible and there are no holes drilled or controls not properly labeled.


    [​IMG]
     
  6. dspblues

    dspblues Silver Supporting Member

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    That's a great sounding Bassman!

    I had been planning on getting one, but I have to hold off on it for a little while since my GAS for something else got in the way.

    Anyway, good thread topic and I thought I'd keep it going. Keep them coming!
     
  7. Texsunburst59

    Texsunburst59 Member

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    Thanks Warren, I think you'd really like the Allen/master volume Bassman head if you're into blues. T>here are a lot of blues tones in this amp between the Tweed and plexi tones. Let me guess on what amp your getting.Here are my guesses.

    Carol-Ann?
    Glaswerks?
    Bludotone?
    Two Rock?
    Brown Note?

    By the way I had gas really bad for the first time in a long time, and I order a Brown Note D'Lite 44 ODE head. I should get it in about 2 weeks. Can't wait. :D
     
  8. dspblues

    dspblues Silver Supporting Member

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  9. Texsunburst59

    Texsunburst59 Member

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  10. dspblues

    dspblues Silver Supporting Member

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  11. Texsunburst59

    Texsunburst59 Member

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  12. hasserl

    hasserl Member

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    Convert the Bass channel to Marshall w/ cathode driver tone stack. Have the best of both worlds. BF Fender on one channel, Marshall on the other. Add a post PI Master Volume to make the amp much more versatile.
     
  13. geezar12

    geezar12 Member

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    i currently have a blackface bassman ... that has been "blackfaced" on the normal side.. I did not know this when i got it until my amp tech pointed this out to me... all i can say is it sounds sweet as butter.. am playing it through alnico blues.. not your classic fender speaker choice., but works well for me.. I sent my amp down to wakarusa amplification to get the marshal mod done on the bass side.. can't wait to get it back
     
  14. blackba

    blackba Supporting Member

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    Any links for how to have a post PI master and what value/taper pot to use?
     
  15. Texsunburst59

    Texsunburst59 Member

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    Tell me where I can get a Bassman style amp PTP wiring and does all that my Allen/master volume modded amp does for $ 500 and I'll buy. I'd be glad to get one. I bet you can't point me to one. Anyway I've had this mod done to many BF Bassman heads and it's never cost me more than $500. I know a local amp guy that does it for me for almost nothing. That's why I do this, and the fact that there's still hundreds of BF Bassman heads still out there.
     
  16. blackba

    blackba Supporting Member

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    +1 I don't see the problem of modding a BF bassman with a AB165 circuit, those are very common and the circuit is a strange one for a BF amp. I do have an issues with modding an AA864 circuit since those bassman's are more rare....
     
  17. Red Planet

    Red Planet Member

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    Well I posted but the server ate it as usuall. :BITCH
     
  18. Red Planet

    Red Planet Member

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    OK here are some things I think can be done easy enuff.


    #1 PPIMV

    #2 Pentode / Triode Switch

    #3 Add extra gain stage to one Channel and put Level after it.

    #4 Change Bass Channel to a Nomral Channel.

    #5 Do other things to Channels.

    My question is what is the best way to get the goods out of one (dirty) and still be able to get the great cleans?

    I have a 67 in a Combo Cab that has two Normal Channels, the Bass Channel has a Mid Boost, the power section has been AA164'ed, and Im using 5814's in V1 and V3.

    Its a great Amp but I'm still trying to figure out how to get it to be more versatile.
     
  19. blackba

    blackba Supporting Member

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    I have been looking into that, seems to be alot of varying opinions if adding a master volume is a good thing.
     
  20. Red Planet

    Red Planet Member

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    Well its hard to say not knowing. :D

    I am on the fence as to what to do. Like I said before mine sounds great but I'd like to be able to get more breakup at lower volumes and it seems to like being loud and clean.

    I'd love to be able to get a Mesa Overdirve out of it and still be able to get the Clean sound it has.

    I was talking to Jeff Andrews and he said he could do an add half a Gain Stage to one Channel and put a Volume Control right after the extra gain stage which would be kind of an early Master but not Master the other Channel. I might could do that and get a PPIMV which would give me a couple ways to go with it. Then use an AB Box and a Pedal for more dirt.

    It might be cool to do that as well as adding a relay to switch Channels and a Pentode / Triode Switch for those times when you really need to get low.

    Of coarse after I did all that I'd need to put a Boogie Name Plate on it then. :D


    Donno.
     

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