Spiff up a Weber 6a40 (parts upgrades)

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by reomi, Feb 8, 2008.

  1. reomi

    reomi Member

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    Ok, so I picked up a Weber 6a40 (BFSR clone) for the cost of the kit from an acquaintance who needed the money. Its point to point wired by a good amp tech/builder here in town. It is a stock kit save a trem boost mod and loaded with AlNiCo speakers. It sounds ok, the individual notes are nice, but chords get muddy fast.

    I assume that the tubes will have to be replaced as they are whatever came with the amp. I'm pretty well set with the replacement tubes already. What else should I anticipate changing out to get the amp sounding more like a BFSR? Which resistors, caps, etc should be replaced? What about the pots, jacks, and things like the reverb cable?

    I've built plenty of Hifi equipment and messed around with my Class A little amps. However, this is my first foray into a "big boy" amp and I think the challenge will be a good one. I play mostly blues and classic rock (muddy waters, early clapton, allmans, derek trucks) with a tele, H535 and SG.

    Thanks for any input. Hope everyone had a good week!
     
  2. mageerc

    mageerc Member

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    Make the tube change first... some Winged C 6L6GCs would be good. Decide then if anything else need be done...
     
  3. conundrum

    conundrum Member

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    -Change tubes, make sure bias is correct
    -make sure all 4 speakers are in phase
    -let it run for a couple hours for capacitors to burn in

    If I recall correctly, all weber kits come with "mallory style" coupling caps, so you could try to put orange drops in their place and that may help with the muddiness, but I'd doubt it.
     
  4. reomi

    reomi Member

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    Thanks for the input. Took the advice and changed out the tubes. The tube lineup is now:
    1) No tube
    2) Reflektor-production Tung-Sol 12AX7
    3) NOS JAN PHilips 12AT7WA
    4) Reflektor-production Tung-Sol 12AX7
    5) Sovtek 12ax7
    6) NOS Mullard CV-4024/12AT7WA
    7) TAD 6l6GC
    8) TAD 6l6GC
    9) Weber Copper Cap Rectifier

    The muddiness is reduced a good bit. However, the tone is still a bit sharper than I'd like. Whie the bass is just about right, the mids could be a bit sweeter..

    I suspect some of this will be helped by the speakers breaking in. I also am going to swap the copper cap for a mullard 5ar4, just have to wire up heaters from the tranny first. I can't help but think that the resistors and caps in the signal path should be changed out though.
     
  5. bob-i

    bob-i Member

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    I have the same issue with my 6A40 and I've changed everything except the xformers and speakers.

    Yes, I agree. The resistors are 1/2 watt CC's and are not bad. I swapped for 1W Xicon's that I like a lot and there was very little change if any. The caps are kinda unknown but I swapped for a combination of caps I have around, 6PS Orange drops and Xicon MPP's. I removed all the silver mica and replaced with ceramic. The biggest difference was the SM -> ceramic. The highs are less brittle and have more grain.

    I also have a 30 year old short spring Accutronics reverb pan which seems to help the overall tone of the amp even with the reverb turned down low. I've found new tanks to be very inconsistant, some great some stink, the one that came with my kit is not great.

    Also interesting is that it seems to sound better with the chassis out of the cab.
     
  6. reomi

    reomi Member

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    bob-i, I'm glad I'm not alone on this. Thanks for the info! I was thinking of modding the reverb tank, swapping out the parts in there for better quality ones, but that is a little further down the road.

    The cc's have to come out. I think some good quality PIO caps and some Bradley's or Rikens can only help. I should probably redo some of the dull solder spots and clean up the wiring.

    Eventually the tube sockets, reverb cable, input jacks, pots and speaker cable will all have to be upgraded and maybe the trannies too. Along with hard wiring the power cable and dampening a few bits here and there. I'm loathe to band-aid this whole thing with pedals.

    If I didn't like modding so much I can't help but think I would have been better off buying the real deal. It just bugs me that my tone through that amp sounds more like Warren Haynes when I'm after more of a Ford, Allman, Trucks sweetness. Can't believe I'm still going to have to gig my kay504 and silvertone 1481 :(
     
  7. bob-i

    bob-i Member

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    That's kinda overkill dontcha think? Any decent quality 1W CC's would be fine in a Super. FWIW CC's are pretty much what all the boutique builders use today, exception might be some Dumble style amps that like metal film on plate loads.

    I actually like the tube sockets, but the rest would be first on my list, way before resistors.
    OT for sure, but the PT seems fine.

    I personally hate hard wired cables. They get yanked and damaged and take surgery to fix. I've NEVER had a plug come loose on it's own, those woh have I challenge them to prove it wasn't helped by some clutz' foot.

    Trucks could play through your car stereo and sound the same. But the truth is his Supers are heavily modded by Lord Valve, plus he uses Pile Driver cheepies only, had a stockpile of them.
     
  8. reomi

    reomi Member

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    Bob-i,

    Thanks for all your input, it is greatly appreciated. I'm most curious about the what if any difference the 5AR4 will make.


    Agreed it is a bit of overkill and should maybe be moved down the priority list a bit. I think a variety of resistors along each path could be interesting. Rather than continuously having the same short comings magnified, use a variety of appropriate good quality resistors to keep things cleaner. This is more of a Hifi amp trick and may be of no use or actually detrimental in a guitar amp.

    The sockets are good quality, but they could be better. However, better ones are awful spendy and may not happen straight away.

    I'll have to start saving up for a new MM or some other OT. Regarding the power cord, I think like most folks, I play in some places that have some pretty weird power situations. As a result I have made a glorified surge protector/line conditioner that is house in a small box in the amp. There is a IEC for a detachable cord on there, then I will hard wire a power cable from the box to the amp.

    When I spoke to Willie to get the tubes he only mentioned the bias and plate test points and bias adjust being moved to the front and a general tidying of the lead dress. Then again, I didn't exactly push for info. Do you know of something more? I know his super six amps are heavily modded. I do have some of those Pyle Drivers I pulled out of an old ampeg 400-g and will try them out.

    Thanks again.
     

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