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Author Topic: Peavey Bandit as speaker cab  (Read 599 times)

weinstev

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Peavey Bandit as speaker cab
« on: November 17, 2021, 02:24:52 AM »
I recently bought a used Peavey Bandit in hopes that I can convert it into a multipurpose tool.  My other two amps are 8" combos, a Vox Pathfinder and a Randall RD1C.  Both have line and speaker outs, and the Randall has an effects loop as well.

I'm looking to do a couple of different things with the Bandit, but I'll focus on the first of those for now.

I'd like to use the Bandit as an speaker cabinet.  With the Bandit turned off, I'd like to simply connect the speaker outs of either of the other two amps to the 12" speaker in the Bandit.  What I'm envisioning is connecting the two wires coming out of the power amp and currently going to the speaker of the Bandit to some sort of switching jack into which I could connect the speaker out from either of the other two amps and then route back to the Bandit speaker.  The attached image shows the two wires to which I am referring.  I'd like to mount/attach this switching jack to the underside of the Bandit amplifier's chassis, preferably without having to drill into it.

So, how best to accomplish the goal of being able to connect a speaker cable from another amp to the speaker of the Bandit?

Being able to use the speaker in a combo as a speaker cabinet seems like a fairly common thing to want to do, but I'm just not sure what is the best way to go about doing this.

Thanks for your help,
Victor

 
« Last Edit: November 17, 2021, 02:36:36 AM by weinstev »

phatt

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Re: Peavey Bandit as speaker cab
« Reply #1 on: November 17, 2021, 07:16:41 AM »
Just a word of warning,
When switching 2 Amp outputs to the same speaker there is always a risk of damage to one or both Amps if the 2 amplifier outputs ever join, even momentary. You would have to make sure the switch is a break before make design for that to work.

My option would be to cut the speaker wires in the Bandit and insert 6.5 sockets.
So the Bandit output goes to one socket while the Bandit speaker goes to the other socket.
Both sockets can be mounted on a bracket and screwed to the insidewall of Bandit Cab. Mark one socket as Bandit output and the other as speaker input.

Now make up a short speaker lead to join the sockets and jumper the sockets to use the Bandit's internal speaker,, then just remove the jumper and plug the other amp output into the speaker input of the bandit.
This way the 2 Amps can never accidentally come in contact with each other.
I've done this idea to a few rigs and works fine.
I'm sure others here my have other options
Phil.

weinstev

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Re: Peavey Bandit as speaker cab
« Reply #2 on: November 17, 2021, 07:47:27 PM »
Hi phatt,

thanks for your input.  I think that what you mean by "6.5 sockets" (6.5mm?) are 1/4" mono jacks.  I'm pretty sure that it's safe for an SS amp to not be connected to the right speaker load; if the jacks aren't connected then the power amp sees infinite impedance.  I'm curious as to what kind of "enclosure" I would use. You mention using a bracket, is there something pre-made that you would recommend?  While it may be a little hokey, I'm picturing a small plastic box with a hole for the input wires currently going to the speaker lugs that would be connected internally to the jacks and then a hole going back from the "return" jack to the speaker lugs. I assume these would just be isolated (as in no electrical connection betwixt the two) mono jacks.  I could then attach either two sided tape or similar to the enclosure and stick it on the bottom of the amp's chassis.  I'm suggesting using an enclosure to protect the jacks from accidental shorts.

I found a thread in the tdpri forum that suggested a few other different options.  The first is very simple.  Just wire the two wires currently going to the speaker to a male mono plug, and add the female counterpart that connects to the two speaker lugs.  This way, I could just disconnect the plug from the Peavey power amp from the female jack leading directly to the speaker and insert the speaker cable leading from another amp.  There's an alternative suggestion to use a cliff jack which in theory would disconnect the Peavey power amp once the external speaker cable is inserted.

Here's a link to the discussion that perhaps more clearly describes what I tried to capture in the previous paragraph:
https://www.tdpri.com/threads/converting-a-combo-amp-into-a-cabinet.352192/#post-5487168

In particular, look at posts 5 and 6 on that thread.  For the cliff jack option, it would probably be best to have both amps powered off when making that connection.

I welcome your feedback.  Thanks so much.  Also, feel free to point me to a good resource where I might purchase suitable mono jacks and some sort of enclosure.  I imagine you were thinking of using some sort of metal scrap material and bending it into the shape of a bracket.

The attached image shows a cable that is almost what I need for the simple option I mentioned above, instead of a 1/4" plug I'm looking for a 1/4" jack or possibly could use a female/female adapter.

« Last Edit: November 17, 2021, 08:06:42 PM by weinstev »

Enzo

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Re: Peavey Bandit as speaker cab
« Reply #3 on: November 18, 2021, 12:26:16 AM »
Just my opinions here...

I don't like the output of the bandit on a male plug.  If it is not plugged into a jack, then it is just flopping around, and that tip could touch something grounded while the amp was unintentionally powered up.

The simplest thing is to put a cutout jack on the rear as others have suggested.  Use the Bandit as its own enclosure.

ALWAYS turn power off when connecting or disconnecting speakers.

Mounting bracket?  A piece of aluminum bent 90 degrees.  One flat surface gets a couple screw holes and is screwed to the wall of the cabinet.  The other flat surface gets a hole to fit the jack.

I recommend CLiff jacks.  They are all plastic so there is never an issue with the jack grounding itself.  Be aware that the cold side terminal of the speaker is NOT at ground in many SS amps, Bandits included.

Jack wiring?  On the Cliff jack, wires from amp chassis to the tip and sleeve cutout contacts, and the wires to the speaker from the tip and sleeve contacts.  That leaves normal operation.  PLug a remote amp into the jack and the amp chassis is disconnected and the outside amp connects to the speaker.

phatt

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Re: Peavey Bandit as speaker cab
« Reply #4 on: November 18, 2021, 07:39:30 AM »
Hi Enzo thanks for the input but my concern with that setup is when the external Amp plug is inserted into the socket in the bandit cab, the Hot tip of external Amp output will momentarily be in contact with the neg terminal of the bandit output (until it is fully inserted)
With both Amps powered off that would work but there is always the chance one forgets to turn off amps.
As you noted the speaker neg of the Peavey output is not at ground. :-\

If I get time tomorrow I'll try to pull the back off one of my Amps to show how my setup works.
I agree the idea of a hot tip floating around is not ideal.

I believe most bandits have the speaker wires hard wired and drop through the bottom of chassis which makes it harder to find a good safe work around.
My amp has a chassis mounted speaker socket which allows one to disconnect the cable from the amp therefore no floating plug.

The  speaker in my combo Amp is wired to one 6.5mm socket mounted on a short alloy angle. so I just remove the speaker cable from the internal Amp and then plug in the external amp with a longer speaker cable.
So it's darn near impossible for both Amp outputs to ever come in contact with each other.

A Double Pole switch would work but would have to be quality Break before Make.
The quality of some switches I've used is not great as I've had a couple fall apart inside.
Phil.

Tassieviking

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Re: Peavey Bandit as speaker cab
« Reply #5 on: November 18, 2021, 07:40:47 AM »
I agree that you need to run the speaker wires into a Jack Socket mounted in the cab of the Bandit.
I'm not sure what you have now, but you could get a small box, like a pedal box 1590B, and mount it in the cab, and then mount your jack socket in there.
You will need a small patch lead with 2 x 1/4" male plugs on it to connect the Peavey speaker to the Peavey Amp.
I don't know where you live so I can't recommend a shop.
I Like Tayda for most of my parts online, but there are so many other great shops to get gear from.
Tayda is very cheap, and the postage is very good too in my opinion, but I just fiddle with stuff for me and family, home use.

joecool85

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Re: Peavey Bandit as speaker cab
« Reply #6 on: November 18, 2021, 11:25:59 AM »
I've seen it done before where the speaker goes to a female 1/4" jack, the amp has a female 1/4" output jack, and then when using it as a combo you use a short 6" speaker cable to tie them together.  Want to power a different speaker?  Just unplug the speaker and plug a longer cable from the amp output into another cab.  Want to use the Bandit speaker (like you do) as a cab for another amp?  Just unplug both ends of the 6" speaker cable and plug a longer cable into the Bandit from the amp serving as a head.  Clean and simple.
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g1

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Re: Peavey Bandit as speaker cab
« Reply #7 on: November 18, 2021, 02:03:26 PM »
Another option is using a closed in-line cable mount jack (like a Switchcraft 121) rather than an open jack & enclosure.  It would not need an enclosure and can be strapped to the inside of the cab.

https://www.newark.com/switchcraft-conxall/121/connector-phone-audio-jack-2-position/dp/39F247

Enzo

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Re: Peavey Bandit as speaker cab
« Reply #8 on: November 18, 2021, 05:04:29 PM »
Or mount a switch and a jack on a small panel.  Wire the speaker wires to the center posts of a DPDT switch.  Wire one end of the switch to the amp chassis, and the other end of the switch to the jack .   Now the switch selects th speaker to connect to either the amp or the jack.  NO possible way for the jack to connect to the amp.

phatt

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Re: Peavey Bandit as speaker cab
« Reply #9 on: November 19, 2021, 01:13:33 AM »
Here is one way to do the connection.
A DPDT switch is likely the best way , just make sure it is a quality switch.
Phil.

weinstev

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Re: Peavey Bandit as speaker cab
« Reply #10 on: November 20, 2021, 09:02:19 PM »
I think we have a winner with regard to the design.  While the Cliff jack approach would work, I like the switch idea.  I have a few followup questions on that, though.

1) Is speaker wire 18 gauge?  I'll need to get some wire to connect the jack to the switch and the switch to the speaker.

2) Does it matter how I wire the speaker to the switch, the jack to the switch, and the Peavey power amp to the switch?  Since the wires going to the speaker carry AC voltage it seems like positive and negative aren't really meaningful in this context.

3) Some quick rough math says that if the amplifier puts 80W through an 8ohm speaker that it needs to be rated for a little more than 3A.

    P = I^2 * R
   80W = I^2 * 8ohm
    10 A^2 = I^2, => I = sqrt(10) ~= 3.1A

I think that I've seen DPDT switches online rated for 5A.

4) I measured the tabs on the speaker and the female connectors that go on the tabs, and they appear to be > 3/16" and less than 1/4".  A brief online search suggests that there is in fact a .205" size that is commonly used, which falls between the two.  I would think I could just go with 1/4" female connectors and squish them a bit to get them to fit.

Thanks everybody for your input above!

Enzo

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Re: Peavey Bandit as speaker cab
« Reply #11 on: November 21, 2021, 01:16:22 AM »
The speaker wires are less than a foot long, so size doesn't much mater.  18ga, 20ga, sure either is fine.

Positive and negative do not apply to AC, no, but the speaker wires are a hot and a return.  You do want to maintain that.  Usually in PV amps th yellow is hot and the blue is return.  WHen you switch, you want the yellow connected onto the + terminal of the speaker, and likewise the yellow connects to the tip of the jack in the other setting.

I;d use a big old toggle, not so much for current but for sturdiness.   ^a switches are common, so are 15A or 20A.  All those are 125v ratings (or higher).  Your speaker won't come anywhere near that.  PLus those ratings are what it can SWITCH, not what it can carry.  I sure hop you do not plan to flip that switch while cranking the amp.

Yes, I forget the size, but I had a drawer full of the speaker terminal size crimp on connectors.   You can also just solder the wires to the speaker.