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Post subject: Blues Junior iii Extension Cab Help
Posted: Sun Nov 04, 2012 4:50 pm
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Hi there

i recently purchased the Blues Jr iii Tweed chocolate sides and oxblood grill, with jenson speaker. I have changed bands from a rock band to blues, and have been using my old rig of a Mesa 50/50 stereo power amp and rocktron prophesy pre amp, run through a Randall XLT 4X12 CAB Vintage 30. Though i love the sound, i no longer wanted the hassle of moving that amout of gear.

I wanted to down size my rig, and felt the junior was best for me having tried a twin (too loud) blues deluxe (too loud).
The junior sounded good in the shop, once i got it to our rehersal space on the same day, it sounded terrible.
I took it home, and it sounded quite good in my kitchen, still a bit shrill and weedy but not as bad as rehersal space. I gues i must be unable to move much air, The rehersal space is sound proofed some what, which is probably not helping matters, but still the sound was as different as night and day!

My Question is this, i am aware of the ability to use an external speaker with this amp, but was wondering if i could run it through my 4×12, as above, to see if the vintage 30′s would make a difference. My only concern is this cab runs either stereo 8ohm or 4/16ohm mono. Is it ok to run the blues junior through this, and if so, what input on the cab do i use?

Am i fighting a losing battle with this amp, it sound like a cheap basic practice amp, my pedals (maxon Vintage od9 and boss blues driver) sound like fizzy lifeless pedals. There is no depth to this amp, no sustain, totally lifeless. I really need a resolve as i just can't use this for band practice, let alone to gig. (which i am hoping to do, small venues).

thanks for any help you can give me,
kind regards
richard
Northern Ireland


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Post subject: Re: Blues Junior iii Extension Cab Help
Posted: Sun Nov 04, 2012 6:40 pm
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My Blues Jr. is an older model, not the III and I could not find clear info. on the speaker connection jack(s).
1) If there are two, one for the internal and one for an external, you could plug one side (8 ohms) of your stereo 4X12 into the external jack (along w/ the internal spkr.), or remove the internal speaker plug and plug two speaker cables into both jacks in the amp and then to the two stereo connections of the cab. In the latter case, the amp will be acting as a head.
2) If there is only one speaker jack, as is the case with the older versions like mine, remove the internal speaker plug and plug one side (8 ohms) of your stereo 4X12 into the this jack.

You'll probably get recommendations to do other connections, but they will result in impedance mismatches. Some will advise that this will not harm the amp (and it probably won't for short durations at modest volumes) BUT Fender advises against such practices.

At any rate, this will give you the ability to try the other speakers to see if you like them driven by the BJ.

BTW, I like my BJ, but like my Blues Deluxe Reissue more, although it can be loud.

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Post subject: Re: Blues Junior iii Extension Cab Help
Posted: Sun Nov 04, 2012 6:51 pm
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Hi RICKJG7,

Great idea to use an external cab with the BJr, the difference in sound can be amazing.You will get the most power from the amp when using an 8 ohm speaker cab, but it also works well with a 4 ohm or 16 ohm cab, one way will probably sound the best to you. Sounds like your cab will utilize two speakers using one of the 8 ohm inputs, and all four using the 4 ohm or 16 ohm inputs (is that right?). Be sure that you unplug the amps internal speaker, and use the speaker jack and not the foot-switch jack. Try it out and let us know which you end up using.

Edit:
There have never been two output jacks on a factory BJr, and Fender has stated that the BJr will work fine with a 4 ohm or 16 ohm speaker (talk to a Fender tech, not customer service ;) ). Billm also agrees that the BJr can handle the impedance mismatch just fine. I sometimes use mine with a 16 ohm 2x12 cab, but find that a 1x12 8 ohm cab sounds just fine. The impedance mismatch seems to really puzzle many people, maybe even scare them. If you really know tube amps you'll understand that a 2 to 1 mismatch is not a problem.

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Post subject: Re: Blues Junior iii Extension Cab Help
Posted: Sun Nov 04, 2012 9:19 pm
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If your just wanting to see how it sounds with the Vintage 30s don't expect them to sound the same if you actually mount one in the Blues JR. The open back and small cabinet will make them sound much different. I really like mine with the Swamp Thang and I use mine at "small club giving levels" I have heard good things about the cannabis rex as well ( with this amp)
Mine isn't the III however which may sound more shrill with the "sparkle mod"
I also find the master volume takes a little of the liveliness out of the amp unless its wide open.


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Post subject: Re: Blues Junior iii Extension Cab Help
Posted: Mon Nov 05, 2012 5:05 am
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Thanks guys for the help i really appreciate it.

The connections on the back of my 4 x12 cab are as follows:

Single jack input for 4 ohm Mono;
Single jack input for 16 ohm Mono;
A selector switch to choose between Mono and Stereo;
and then writing underneath the switch saying "use both jacks for Stereo"

The blues junior has 2 jacks to the rear underneath; 1 for the fat boost footswitch, and 1 for the speaker.

So to be clear, if i take a lead from the speaker out in the blues junior, and plug it into the 4 x12 cab at any of the above ratings (4/16 or 8 stereo) it will be ok??

If i plug it into 8 ohm stereo, do i need to connect another lead into the other jack input on the cab that is not it use?

What i hope to achieve from this excersise is to see if the sound and quality improve with better speakers in a closed back cab. There in i would purchase a dedicated 2 x 12 cab so i can use this with confidence at small gigs, instead at the minute, i just couldnt see myself using this in practice let alone a gig.

I purchased this last week, and it may be a case of washing my hands of it and get store credit. :evil: :(

Sorry if these questions are a bit basic, but i just dont want to blow the amp incase i have to take it back

thanks again

rick


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Post subject: Re: Blues Junior iii Extension Cab Help
Posted: Mon Nov 05, 2012 5:36 am
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Update:

just got this email from fender themselves, so i guess 16ohm is the way to go with my cab set up:

"From your description of the cab I would guess that it has 2 inputs on the back. When in 16ohm mono you probably have to use the left side and when you switch to stereo you need to use both (left and right) as it will “split” the cab. This means that if you run the cab in stereo with the Blues Junior you will only be using one side of the cab. You should therefore use the cab in mono 16ohm so you’ll be using all 4 speakers. The Blues Junior is rated for 8 ohms but it will be ok pushing a 16ohm load although it will reduce the output wattage because there’s more resistance. "

Will let you guys know how i get on

regards

rick


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Post subject: Re: Blues Junior iii Extension Cab Help
Posted: Mon Nov 05, 2012 6:29 am
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The BJ was designed for an 8 ohm load, and given that you are thinking of getting a 2X12 ext. cab, move the switch to stereo and use just one cable to run 2 of the 4 speakers. If you have any doubts, plug the speaker cable into one side and use a simple multi meter to check the DC resistance between the barrel and tip on the other end of the cable. DC resistance is one component of impedance and should read 5-7 ohms for an 8 ohm impedance, 2-3 ohms for a 4 ohm impedance, and 11-13 ohms for 16 ohm impedance.

Using the 16 ohm connection as suggested by Fender may give a different sound.

Any way you connect it should not harm it for a short duration @ modest volume.

Hope you like the sound!

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Post subject: Re: Blues Junior iii Extension Cab Help
Posted: Mon Nov 05, 2012 7:45 pm
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It seems that everyone agrees at least this point, that using either one of the two inputs on the cab with switch to "stereo" will utilize 2 of the four speakers and give you 8 ohms. My preference would be to use all four speakers, in either the 16 ohm input or the 4 ohm input, obviously with the cab switch to "mono". Try all and see which sounds best to you. I have no doubt that any of the cab configurations will be an improvement in sound over the BJr internal speaker.

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Post subject: Re: Blues Junior iii Extension Cab Help
Posted: Sun Nov 11, 2012 1:16 pm
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Here's an interesting option for you.
Convert your BJ to a "Head" unit.

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Post subject: Re: Blues Junior iii Extension Cab Help
Posted: Sun Nov 11, 2012 5:57 pm
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Cool cabinet. I would like to try this, allowing a smaller cab and upright tubes.

http://home.comcast.net/~machrone/bjr/bjrhead/bjrhead.htm

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---> "The amp should be SWITCHED OFF AND UNPLUGGED before you do this!" <---

Por favor, disculpe mi español, no se llega a la práctica con mucha frecuencia.


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Post subject: Re: Blues Junior iii Extension Cab Help
Posted: Sun Nov 11, 2012 11:02 pm
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shimmilou wrote:
Cool cabinet. I would like to try this, allowing a smaller cab and upright tubes.

Me too!

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