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NAD: Silver Face Bassman 70 + ?'s

Discussion in 'Amps and Cabs [BG]' started by Turkeypills, Jan 30, 2014.

  1. Turkeypills


    Nov 8, 2012
    St. Louis


    I recently acquired my first all tube head in the form of a Fender Bassman 70! I was fortunate to cop this from TBer Andychandy who happens to be a good friend IRL. I have quickly grown quite fond of this amp as it fills a tone void that I had been searching for: A relatively low wattage all tube head.

    I had a couple of questions about my current setup that I was hoping the TB community could help answer for me. Some of these have been asked before and I apologize for that, but I did not find that the responses really satisfied my inquiry.

    1.) I hope this doesn't start a flame war. What kind of cab would you all recommend for a tube amp; One-way or full range?

    I do not gig, nor do I actively play in any groups. I am simply a bass hobbyist and bedroom rockstar that gains enjoyment out of the best sound I can possibly achieve. I like to play anything from the Jackson 5 to Black Sabbath as well as hip hop and post rock. I am currently using this head on top of an Avatar B115 with the Celestion BN15-400 woofer. I also have an Eden D210XST. I am super interested in DIY projects and thus am incredibly interested in building a fEARFUL 15/6 or 1212/6. Would I be correct in assuming that the Eden cab would be *closer* to the type of response I would get from a fEARFUL? I am debating this because I was talking about these ideas with a buddy and he mentioned that a lot of those old tube amps were designed to power a one way cabinet. I am totally willing to let my ears do the decision making but I was curious if this theory held water and if there was any *vintage vibe* advantage to sticking with a one way 15inch cab. I'd like to get some auxiliary input before I sell off gear to fund a fEARFUL build.

    2.) I apologize off the bat if this should be in the Effects section but since this issue is exclusive to the bassman (in regard to my SS amps) I figured I could add it into this thread.

    I get a pretty loud and noticeable pop when I trigger the last two pedals in my signal chain (MXR BEF and Korg Pitchblack respectively). I do not experience this pop when I use my Eden WT550 so I assume that means that I can eliminate the pedals as the culprit. If I switch the MXR with any of my other pedals, they will also cause the pop. I have gathered that this is some kind of capacitance issue. I was hoping someone could elaborate on this for me. Would a recapping solve this? Is there some other potential issue that would reveal itself with a diagnostic check by a seasoned tech?

    Finally, no matter where I place my MXR BEF in the signal chain, if I give one of the strings a heavy pop it sounds like total crap. I understand tube breakup with a signal peak, but this is different. It seems to almost kill the signal with a sharp decay, a very broken up sound and, the best way I can describe the last issue is like an octaver or synth struggling to track. This only happens when I give the string a strong pop. If I play with a moderate attack there is no issue, but attack variety is part of what makes filters so much fun. Any ideas to remedy(if possible) this issue?

    Again I apologize if these last questions should be in the effect section, but since I do not experience them with any of my other amps I thought this section was fitting.

    I love this amps warmth and it is really the perfect size for me. If you guys/gals have any insight into these questions I would be super appreciative.

  2. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    The cab that you choose should be based on your sound requirements. Most of the common musical instrument tube amps aren't designed specifically for one-way or full-range. Those that were, came with matching speaker systems. Tube amps were traditionally sold with one way cabs. That's how they did it at the time. Higher fidelity options are available today. Some amps are designed to reproduce that higher fidelity and the higher frequencies. It makes sense to match those amps and cabs together. But it comes down to the tone that you are looking for.

    As for the effects issue. Try your effects chain with the Eden two ways. Connect the effects through the effects loop and see what happens in terms of the pop. Then try it with the effects plugged into the instrument input like you are doing with the Fender and see what happens.

    Some amps and effects are designed to suppress pops. One way to do this is to use anti-parallel diodes that only kick in at a level that is higher than your normal signal level. This effectively cuts off any spikes that should be there. There are other ways of doing this. Your Eden may have a suppression circuit in the effects loop circuit or somewhere else in the signal chain.

    The bottom line is the amp will amplify what it is presented with. Some amps can reduce spikes in the signal pathway. Your effects are the source of the problem. It might not be that they are flawed, this could be the way that they work. If this is the case, there may be a mod to fix them.
  3. experimental bassist

    experimental bassist

    Mar 15, 2009
    Beautiful amp, congratulations! :bassist:

    That's going to sound great with just about any decent cab.

    If it were me, I'd look at one of Fender's brand new pro neo cabinets.

    They'll have the perfect look AND great tone (no offense to anyone but original vintage Fender bass amps look great but often lacked the goods in the tone department). ;)

    No comment on the fEARful stuff, they're great but IMO they really scream for WAY more horsepower than your classic Fender.
  4. kbakerde

    kbakerde Supporting Member

    Jan 24, 2012
    I love the old Bassman amps. I had a 135 and it was fantastic, and once I have the funds I will probably to get one just for the fun of it. These are relatively lower wattage amps so you want something that is pretty efficient. My Bassman came with a huge 2x15 cabinet and it was awesome sounding. I also have a BFM Jack cabinet I was using with my old tube head. It was a 2x10 but it was louder, more clear and easier to carry.

    Congradulations cause these guys are just Awesome!!
  5. I have a 76 Bassman 100 that I play through a 68 2x12 cabinet. I have hooked it up to other cabinets I have (newer full range), but I much prefer the Fender. I think I expect it to sound that way.

    I love mine.
  6. Turkeypills


    Nov 8, 2012
    St. Louis
    Thanks for the replies! I do love the tone I get from this rig.

    Beans, I went ahead and did some further testing and you are correct, it appears to be an issue with the pedals. When I ran the pedals through the Eden effects loops I was still getting a pop from the problem pedals but it was SIGNIFICANTLY reduced. When I run the chain direct into the Fender the pops are quite loud, but it remains constant that the pop only occurs with the last 2 pedals(w/e they may be) in the chain, with the exception of my Sansamp. Is there an amp mod that I could do/have done that would insert the suppression circuitry at the front of the bassman signal pathway?

    Also any idea if Bassmans just do not like envelope filters? Or could the quick decay crap sound that comes from an aggressive attack be solved with the same suppression circuit?

    I appreciate the help with this. If need be I can create a new thread in the effects section.

    Thanks again!

  7. BassmanPaul

    BassmanPaul Gold Supporting Member

    Aug 25, 2007
    Toronto Ontario Canada
    If you are contemplating building a cabinet for this amp you should bear in mind the 4Ω impedance that the amp requires. running it into 8Ω could cause damage to the amp.
  8. Turkeypills


    Nov 8, 2012
    St. Louis
    The back of the amp says 4ohm MINIMUM. Unless I am misunderstanding how impedance functions or tube amps are somehow different, how would an 8 ohm cabinet harm an amp that can take a minimum load of 4 ohms? I know I couldn't run 2 ohms or 2.66667 ohms but why not 8 ohms?

    I thought that 8 ohms would merely use 1/2 of the coils in the output transformer?
  9. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    Some pedal are designed to switch quietly, some aren't. One way around this is to use a looper or pedal switcher. The looper uses relays to switch in or out the pedal. Some units allow you can program the order of the pedals. This ensures quiet switching because the pedal is always on, so no spikes, it is just switched in and out. Here is an example of what I am talking about. There are many such products available. Unfortunately, they can get expensive.

    I don't see a reason why a Bassman wouldn't get along with an envelope filter. I have seen filter pedals that are placed in the signal chain. Something to look into. It might be best to contact the pedal manufacturer and ask if there are any mods or a solution. Maybe PM johnk_10 to see if he has a suggestion for the pedal.

    I've never tried this but....If you want to try an experiment buy two 1N3070 diodes (http://www.mouser.com) and connect them antiparallel across the input from tip to ground. Ampeg uses this diode for this function in the SVT at the preamp out/power amp in. With that diode, anything above 1V will be cut off. Using a different diode will change the cutoff voltage. You might try some signal diodes from radio shack since they are easier to obtain. Too low a cutoff and it will act like a distortion pedal. People often use 1N914 diodes for distortion.

    This is what you can try to build with the diodes and a couple of ¼" jacks. It could be mounted in a small plastic box.

  10. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    Concerning amplifier output impedances and speaker cabs, the rule of thumb is: for a tube amp, lower impedance cabs are better than higher; for a transistor amp, never go below the minimum impedance, a higher impedance is fine but it will be at the expense of output power.
  11. Turkeypills


    Nov 8, 2012
    St. Louis
    Beans, Thanks for all the input I am going to try and build a "magic box" as soon as I get some expendable income. Could I essentially build it and run it like a passive pedal in between my pedal chain and the amp input? Or does it need to go in between the preamp and power section? I do not see a way to easily perform the latter. I think the only thing I don't like about this head is the lack of effects loop. Even though I never use the effects loop on my eden because I almost exclusively use ODs, EFs and octavers. I feel like I would be super handy with this amp.

    As far as cabs go both of my cabs are 8 ohm and they sound like poo together, so until I can afford to build a 1212/6 (I think the dual woofer fearfuls are 4 ohms although I may be mistaken) 8 ohm is all I have.

    Thanks again for all the help. I really love the tubey warmth, the relative light weight and the perfect power level for my needs that this head provides.
  12. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    If it helps, the box could go between the pedals and the amp input. For testing, it could be built with two ¼" plugs with a bit of wire in between, like a short patch cable.

    There are effects loop kits available from places Weber. Unfortunately, adding an effects loop would require some holes in the Fender chassis. Not too good to hack up such a nice little amp.

    Hope that you make some progress on this at some point. Clicks from effect pedals is quite common and drives people nuts.
  13. Turkeypills


    Nov 8, 2012
    St. Louis
    Yeah I am actually perusing a few pedal based effect loops that might help this situation. Honestly I am more bothered by the ****storm that comes out of the speaker when playing with the EF. The MXR BEF is easily my favorite stompbox and I have never had this issue. I do have a very heavy attack though. I will PM Johnk_10. I might PM you some sound samples so you can hear what it is I am talking about exactly.

    For the magic box: you said a couple 1/4" jacks (I assume mono would work for this) and some wire to connect the diodes. Could I use a small piece of breadboard or just wire for a little point to point?
  14. Stumbo

    Stumbo Wherever you go, there you are.

    Does the amp have two speaker output jacks? If so, plug both your 8 ohm cabs in to get 4 ohms,
  15. Turkeypills


    Nov 8, 2012
    St. Louis
    Yeah it does. I can also daisy chain for a 4 ohm load. But when combining the single driver 15 with 2 10 inch drivers I get a slight phase issue and the 15 is TOTALLY dominated by the 210. Not to mention these two cabs have entirely different tonal characteristics. Unfortunately it sounds like poo.
  16. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    Anything that can be patched together that doesn't short will work for the test. RS sells mini breadboards. Jacks are easier because you can wire the diodes directly to the jack terminals. Harder to do with plugs.