Hoffman Amplifiers Tube Amplifier Forum
Other Stuff => Cabinets-Speakers => Topic started by: tedsorvino1 on November 03, 2017, 08:26:57 am
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I would like to know if there is a safe way to switch between 2 guitar cabinets?
I'm using a 60W tube (fender style amp) and I would like to build an A/B (or even A+B) (foot)switcher box to chose between 2 cabinets (Both 8 ohm).
I know the Radial box but it's way too expensive for me.
I've heard of a switcher that uses relays, but I haven't got any clear information.
I've also read about a passive box with resistors and a switch but it's not exactly what I was thinking since it's working only with the amp bypassed.
Any ideas, info or layouts (or schematic) on how to build such a box would be much appreciated.
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All you need is a heavy duty SPDT switch. I used an automobile floorboard dimmer switch back in the '60s to switch one amp between two cabs.
https://www.ebay.com/itm/Floor-Mounted-Headlight-Dimmer-Switch-3-Terminal-for-Chevy-Jeep-Pickup-Truck-GM/131145907311?epid=568969232&hash=item1e88e7bc6f:g:pOwAAOSwmT1ZedTi&vxp=mtr
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Sounds interesting Sluckey, but how could I connect it to 2 speaker cabs and the amp out? And how does it work? Can i put it in a box? Footswitch?
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Since his indication that the switch is the only thing needing robustness, you'd just need 3 jacks, a box and the right gauge of cable. The switch just has to handle the higher current of output, (like a speaker cable does). Then use the same gauge cable to connect the input to the switch and the two outputs of the switch to the output jacks. That simple. The bigger problem is that most switches can't handle higher current so you'd need to look them up based on the amp output you're expecting as a max and then maybe double it to be safe. In other words ANY a/b switching box schematic will work, you just need to use parts that handle the current of the output.
~Phil
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Excellent Phil. Thanks for the info.
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Heavy duty A/B footswitch...
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Fantastic Sluckey. Thank you so much.
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Hey guys I 've made some more research and I discovered that Radial is using relays in their Cab Bone system.
This is a schematic I found for an A/B with relays:
http://photobucket.com/gallery/user/seedlings/media/cGF0aDovbWFrZWJlZm9yZWJyZWFrX3pwc3ZsbGdzdm9rLmpwZw==/?ref=
How could I make it work as an A+B as well?
Is there any advantage to the Sluckeys' schematic that is using the MBB switch?
Can the MBB switch be connected in a way to give us the A+B option?
Here is what I found from the Radial Cab Bone site.
Of course there are many usefull and fancy bells and whistles but the basic principal seems the same. They 're too using relays.
http://www.tonebone.com/tb-cabbone-development.htm
http://www.tonebone.com/tb-cabbone-using.htm
What do you think?
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The photobucket circuit does exactly the same thing as my simple one switch circuit does. Nothing more. Nothing less. But now you must also have a 9v power supply, two relays, two caps. Why complicate things. I believe in the KISS principle.
I never mentioned MBB switch. Where did you get that idea? My simple circuit does not require a MBB switch. It's possible that the floorboard mounted headlight switch is MBB but I don't know that. I do seem to recall that while pressing the switch that hi-beam and low-beam lights were both on, which would imply MBB, but I'm not sure. It's been over 40 years since I stomped on a floor mounter headlight switch. Regardless, it's not important for this speaker switch. The important thing is current capacity and ***RELIABILITY***.
If you want to add A+B functionality you need to add another switch that will short between the two cab jacks. I suggest adding another headlight switch.
That Radial Bone Cab switch is way more versatile and has many more bells and whistles as compared to my simple switch. But since it is way too expensive for you I suggest you forget about it.
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Thanks Sluckey. Ι totally aggree with KISS. Simplicity rules.
But I thought it needs to be ΜΒΒ because at least in theory (never tried it) the output transformer always needs a load. And the power tubes may face an arcing problem.
1)Am I right?
2)How do we overcome those problems with the headlight switch circuit and the momentary non load issue?
3)What the current capacity for the switch must be?
4)Could you please show me how your schematic would be with A+B functionality and an extra switch?
Thank you for your time and help.
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But I thought it needs to be ΜΒΒ because at least in theory (never tried it) the output transformer always needs a load. And the power tubes may face an arcing problem.
1)Am I right?
You're partially right. But your amp can sit for days with no speaker connected as long as you are not putting a signal into the amp. Surely you don't intend to switch cabs while you are playing!!! Stop playing. Count to one. Stomp the switch. Start playing again.
2)How do we overcome those problems with the headlight switch circuit and the momentary non load issue?
It's not an issue if you use it wisely. I would not have suggested this if it were a problem.
3)What the current capacity for the switch must be?
Many amps. That's why I suggested the automobile switch.
4)Could you please show me how your schematic would be with A+B functionality and an extra switch?
I already told you exactly what to do. It's not complicated.
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Thanks again Sluckey.
The thing is that I d like to know the approximate current for the switch, since the one you suggested is way too expensive to be sent out in Greece (more than $30). And I'm goning to need two of those.
Another question. Are you using shorting jacks on your circuit (like switchcraft 12A)? Or just simple mono jacks?
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Could something like this work?
https://www.meritmalta.com/switches-dimmer.asp
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I think I found one made in China. What do you think?
https://www.ebay.com/itm/Floor-Mounted-Headlight-Dimmer-Switch-For-GMC-Chevrolet-Jeep-Buick-Cadillac-DS72/371979407712?hash=item569bb35160:g:ALUAAOSwPWRZPj53&vxp=mtr
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I can send you a schematic of a circuit that is a speaker switch, that has no relays or switches in it, that will allow you to switch between two cabs even on the fly if the drivers would handle it. Tell me what type of sch file you can open. They are currently in Altium.
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automobile floorboard dimmer switch
makes a good poor man anti theft switch also, run the starter solenoid wire through it (NOT the big RED one, the small one :)
on "new" '90s cars everybody, including thief's forgot there ever was that switch so NOBODY though to check for one :icon_biggrin:
a variant to that, I found a momentary one to "sub" as ignition switch, depress, start, remove foot
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I can send you a schematic of a circuit that is a speaker switch, that has no relays or switches in it, that will allow you to switch between two cabs even on the fly if the drivers would handle it. Tell me what type of sch file you can open. They are currently in Altium.
I'd love to see that. Most everyone can view pdf. Surely Altium can print to pdf.