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lucked into a piece of bass amp history

Discussion in 'Amps and Cabs [BG]' started by bassment zombie, Jun 3, 2005.

  1. ...for $299.00, and it sounds amazing. This puppy is far from history, as she's in pristine condition, and works perfectly (except for the standby switch). I guess it averages out to roughly $1.50 per watt.

    Just got her home and shot some photos on the cruddy back deck.

  2. Here are a few more shots:

  3. i must say that i have never heard of them. but it looks sweet!
  4. What has she got for tubes?
  5. I spoke with the Dave West himself, and described everything about the amp to him. He said it was definitely one of the amps made specifically for Grand Funk, and from everything I told him, this amp had been babied through the years, and even upgraded in a few respects.

    He told me that the pre is based on the Fender pre, and that it wasn't really a high gain type of amp. He said if/when the tubes need to be replaced, that GE 6550A tubes could be used...etc.

    He was aghast when I told him that I bought this amp for $299.00. He told me that it would fetch upwards of $1000.00 these days to folks who know them. He said he would offer me $600 for it immediately on the spot even if it wasn't functional - wow, I had no idea.

    Here's a link to West Labs webpage: http://westlabs.com/Frames.HTML
  6. bigbeefdog

    bigbeefdog Who let the dogs in?

    Jul 7, 2003
    Mandeville, LA
    Nice find. Congrats. :)

    It's a bit hard to tell in the pics (plus my eyesight isn't what it used to be), but it *looks* like that's 2-conductor lamp cord going to an obviously non-original 3-prong plug. If that's the case, that ground might not be connected/functional.

    If you keep it for your use, I'd have that checked, and add a true ground if necessary for safety's sake.
  7. Please excuse my ignorance here...

    The 4 power tubes appear to be Ruby 6550s. The other 5 tubes (pre-amp tubes, I assume), are enclosed/encased, and I can't tell what they are. If you can describe an easy way for me to determine, please let me know, and I'll try.
  8. Thank you very much! :)

    Sounds like your eyes are doing quite well :D
    There is some print/script on the cord itself. If I typed that information, do you think you might be able to determine if the ground may be connected or not? I'm very ignorant of these things :oops:
  9. bigbeefdog

    bigbeefdog Who let the dogs in?

    Jul 7, 2003
    Mandeville, LA
    No, any stamping on the cord itself probably only gives info on cable type, size, temp. ratings, etc....

    If it's obviously 2-conductor lamp cord, with no third conductor for grounding, that tells the tale. You might find that you can open that plug up with a screwdriver and look inside, to see if anything is connected to that ground lug.

    If not, adding a *good* conenction to ground makes it a much safer amp for you, so have a tech check it out if need be. It's awfully common for amps of that vintage to *not* have adequate grounds.
  10. Those are Chinese 6550's, not very relaible. They have a BAD reputation for shorting, whihch would do damage to your amp. Normally, I don't recommend people just swap tubes out of a functional amp, but if that were MY amp, I'd change those output tubes ASAP.

    Those SHOULD just be metal shields that have a twist-on base. All you should have to do is turn the metal shield and they should lift right off.

    The best way to know if the amp is grounded is to unscrew the yellow replacemment plug and see if there's a green wire attached to the big bottom(the ground) pin. There's NO danger to doing that whatsoever, but if you're uncomfortable opening up the plug, get someone with wiring/electrical experience do show you how.
  11. 00soul


    Jan 4, 2005
    seal beach, ca
  12. Thanks, Bass Guy. What are my options? How do they compare, and what would you recommend?

    Thanks. The 2 small ones in the front did exactly as you mentioned. Perhaps I need an eye exam, but they appear to be a Sylvania 12ax7a and a Westinghouse 12at7 :confused: The 3 other 'towers' in there don't have the same metal shield mechanism that lifts off. I gently tried pulling on them, and they didn't come off.

    I just took a photo of the 3 that I am talking about. Any idea how I can get a look at them without damaging anything?


    I'll give it a shot in a few minutes - thanks so much, Bass Guy - waiting for your suggestions :cool:

    PS - also, looking at the 4 jacks on the backside of the amp - the 4 in a row on the ride-side back panel...can you tell just by looking at them what they are? I'd hate to use a 'trial and error'...when I played the amp before in another location, it was already hooked up, and I didn't pay attention. I don't know much, but it seems odd to me that all 4 would be speaker outs... :confused:
  13. bigbeefdog

    bigbeefdog Who let the dogs in?

    Jul 7, 2003
    Mandeville, LA
    BTW, looking at the schematics on the link you posted, it seems it has 4x6550 for power tubes, 12AT7/12AX7 for pre, and an original *two*-conductor (non-grounded) AC cable.... originally, that is.....
  14. The pre-amp tubes should be good then.

    I kind of figured the power amp tubes might be shady based on their shape.

    I've always gone by the logic of having a tech look over any vintage amp, tube or ss after aquiring it.

    Old amps are like a box of chocolate. Some idiot could put his nuts in there.
  15. Excellent, thanks for looking that up for me. The pre-amp tubes appear to be fine, then. Looks like I'll just need to get new 6550 power tubes, and get it re-biased, re-'corded' and completely run-through by a tech.

    Any suggestion for 6550 power tubes? :help:

    Good call, my friend. :cool:
  16. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    Hmmmm, that amp looks familiar :D

    I'm glad that it made the trip from Ann Arbor to your place safely. You're very lucky that I had just promised my wife that I wouldn't buy any more gear and that I had flown to Detroit on business rather than driving. Otherwise....

    Wow, Dave said that it was one of Grand Funk's amps...very cool...no wonder it sounded good when I did my best Mel imitation through it..it already knew the song and corrected my shortcomings!!!!

    Did you tell Dave that it came from the Ann Arbor Music Go Round store?...that would have really gotten his goat as he is not too far from there.... In fact, when I first saw it and figured that there was no way I could carry it on the plane (although I did carry it around the store for a few minutes to see if I had a fighting chance) I thought about letting Dave know it was there....but you got to me first ;)

  17. *whew*! :oops: :D

    *laugh* awesome, my friend...

    I sure did...he gasped a time or two, and we both ended up laughing for a few minutes about it.

    Thanks to you, that is! And also a big thanks to my buddy Mike in Ann Arbor who secured it for me, babied and brought her by to me here in Boston on the way to visiting his wife's family in NH.

    If you're ever in Boston, Billy, drinks on me :cool:
  18. Passinwind

    Passinwind I am Passinwind and some of you are not. Supporting Member Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    Those are power supply filter capacitors; they don't pull apart easily (and will be broken once you do so) and you don't want to mess with them unless they are original and in that case likely need replacement. :cool: The only looking at you can do is reading the ratings on the cans.
  19. My first choice is the Sovtek KT88, but EH 6550/KT88's (they're the same tube) are nice, as are Ruby's CURRENT 6550, which is a near perfect copy of GE's 6550A (ought to be-it's made on the same machines that made the GE's!) I do NOT reccomend Svetlana/Flying C 6550's! They have bad problems with internal bracing and age VERY poorly. Actually just about ANY currently made 6550 or KT88 will work beautifully EXCEPT the Svet/Flying C and the OLD Chinese 6550's, which are what's in it now.

    Those are capacitors. They don't open (or at least they BETTER not!!)

    It will be worth it have a tech open the amp up and label the outputs for you. If you try to run the amp with the speaker cable in the wrong jack, you could SERIOUSLY damage the amp! You can get it retubed, grounded, and labelled and you'll have a kick-ass amp that'll last for many years to come.
  20. ryco


    Apr 24, 2005
    WOW!! You dawg! Whata find!! ....and Mel Schacher ROX!!

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