Re-housing my Katana 100 - AKA how to void your warranty

Discussion in 'Amp Central Station' started by tfarny, Sep 5, 2018.

  1. tfarny

    tfarny Friend of Leo's

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    So last year I got a Boss Katana 100 in the 212 combo cab with the big GAFC foot controller on Craigslist for a great price. It's been a good amp and I've used it for a few shows. I would have preferred the 112 version for portability reasons though. My house has narrow steep stairs and my main music room is in the attic, so lugging that thing around my house is just kind of a pain. Anyhow I was thinking about trying my hand at cab making and thought this would be fun. Total cost of $0, since I had a piece of vfbb 13 mil ply in the garage. Construction is all glue (titebond 1, properly clamped and set overnight). The Katana head attaches a little differently than your basic tube amp head so I had to do that a little differently.

    Anyhow I'm planning a 1/4" floating baffle (since that's what I have in the shed) reinforced a little bit, and a removable rear panel to maybe recover some of the bass response I'm going to lose by ditching one speaker. I'll rout a rounded edge all over and finish it with some basic stain / poly stuff I got laying around. For a speaker I've got the Katana speakers - they are 16 ohm each, amp is 8 ohms out, should be fine with 1, and I've got a Cannabis Rex 8 ohm I want to try. I'm tempted to use this opportunity to try another speaker but that would ruin the cheapskate appeal of the project. I will have to buy a handle though....
     

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    nojazzhere, DugT and FenderLover like this.
  2. DrBGood

    DrBGood Tele-Meister

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    Nice project.

    I'm looking the other way, to add a speaker output to connect my 2X12 cab.

    2X12.jpg
     
  3. tfarny

    tfarny Friend of Leo's

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    Ok, I'm done with it for now! It all works great and I've been playing it for a couple of hours.
    Grades:
    Cost $0 - I borrowed the handle from something else and I already owned the feet. Grade: A
    Portability - I probably dropped 15 lbs between losing the speaker and the much-lighter cabinet Grade: A
    Sturdiness: I new that a properly glued butt joint with reinforcement was plenty strong enough, if you clamp it and let it cure overnight, and it is. Cab is as sturdy feeling as any I've used. Grade A
    Sound - it's obviously quieter with less bass, but it's not thin. In fact I think I prefer it like this - maybe the floating baffle helps it feel more "live" I don't know. Grade: A+ (I thought it would sound worse). And I still want to experiment with making a closed back option.
    Looks: See for yourself. Grade: F- but that's pretty generous. Next step: Teach myself to Tolex, and buy some grill cloth.

    I learned a LOT from this fun and easy little project. I'm gonna use it at a gig on Sunday, wonder what kind of looks I'll get.
     

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  4. Wally

    Wally Telefied Ad Free Member

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    That 16 ohm load will cause the amp to yield 1/2 of the power compared to what happens with the 8 ohm load.....solid state works that way. Also, this amp wants to see no less than an 8 ohm load. The output can be fried with a load that is lower than the design calls for.
    https://static.roland.com/assets/media/pdf/KATANA_e02_W.pdf
     
  5. Edsel Presley

    Edsel Presley Tele-Holic

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    Looks good. I want to tweed my 50 out.
     
  6. tfarny

    tfarny Friend of Leo's

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    Yes, and I notice it is quieter, but in practice that just means it's easier to find the right volume - it's still more than loud enough for all my situations. I was pretty sure that I understood the ohm thing, but maybe I don't. I thought 8 ohms into a 16 ohm speaker was generally considered perfectly fine and safe. I thought that going the other direction - 8 ohms out into a 4 ohm speaker setup - was problematic. No?
     
  7. tfarny

    tfarny Friend of Leo's

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    Yeah man, do it! I really do think it sounds better than before - more "lively" - I can feel the baffle vibrate - the whole cabinet kind of sings, really - that I never noticed with the big MDF stock cab. No weird rattles or sympathetic vibration weirdness either, which I was slightly concerned about.

    I am definitely going to add speaker cloth and tolex - maybe racing green, maybe cream. And I'm going to stick my Cannabis Rex in there and see how it sounds but I expect it will be too dark for my tastes, given that I'm always looking to cut through.
     
  8. Billnchristy

    Billnchristy Tele-Afflicted

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    Speaker determines the load, not the amp.

    You are using double the resistance, therefore half the power.
     
  9. schmee

    schmee Poster Extraordinaire

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    For those inclined to build a box. I was searching for wood storage crates on line this am. I found fairly good sized pine ones with dovetail joints for $33 each! One could do some cutting and make a cab out of one of those! I didn't save the link as I bought something else for storage but... it's out there...
     
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  10. schmee

    schmee Poster Extraordinaire

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    I thought about rehousing my little Fishman mini loudbox recently with a bigger speaker, maybe open back. But when I took it apart, they have a ton of multi strand wires and connections going to the speaker & tweeter...
     
  11. tfarny

    tfarny Friend of Leo's

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    What you're saying is that by going to one speaker at 16 ohms vs. two in parallel at 8 ohms is that I've turned it into a 50 watt amp. If I ran two 8 ohm speakers in parallel for a 4 ohm load I'd have created a terribly stressed out 200 watt amp that could fry itself right up. Right?
     
  12. Wally

    Wally Telefied Ad Free Member

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    "If I ran two 8 ohm speakers in parallel for a 4 ohm load I'd have created a terribly stressed out 200 watt amp that could fry itself right up. Right?"

    A solid state amps works as you are describing with the one caveat...the amp's design sets the lowest usable load impedance that the amp can use safely. As the manual notes, for this Katana 100, that low limit is 8 ohms....anything lower puts the amp's output section at risk.

    As for tube amps....that mismatch question has other aspects to consider. At 50% to the low side, the power tubes are worked harder. AT 100% to the high side, the OT is put at some risk. A match is preferable, imho, because the amp is more efficient and the components of the output...tubes,OT and speaker.... are 'cooperating' as designed. OMmv as to the advisability of mismatches. I like a match or a mismatch to the low side by no more than 50%?
     
  13. deadbeat son

    deadbeat son Tele-Afflicted

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    Maybe. The power supply would have to be beefy enough to handle the additional current necessary to put out 200w at 4 ohms. It’s not likely the Katana would do that since it wasn’t designed to operate at 4 ohms.
     
  14. Billnchristy

    Billnchristy Tele-Afflicted

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    In general terms, yeah. Some amps can't double but it's a decent rule of thumb.

    I was running a car amp at 1 ohm mono, it was rated to .25 ohm stereo. That beefy sob was playing to nearly a dead short when one of my subs voicecoils failed. It was thermalling every couple minutes but when it cooled it would come back on and play for a bit.
     
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