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Polytone Mini Brute (original from 80's) - ext speaker?


Magic Matt
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I have an old Polytone Mini Brute, which was my Dad's, bought int he 80's. It's not got a model number other than just "Mini Brute" - I'm assuming this means it's one of the first, before the Mini Brute II etc. came out.

I have no manual for it. If anyone has one, or a link to one, it would be much appreciated!

There are two sockets on the back - one labelled "Ext Spkr" and one not labelled at all. I would like to know what impedence speakers I can use with it, as I think adding a second speaker would make it a really usable amp to gig with in the band. Also, what does the other socket do?

Any help very much appreciated.

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I may be able to help as I've owned a couple of Polytone combos in the past and may still have a copy of a manual somewhere. From memory though the specs suggested the amp could cope with impedances as low as 2-3 ohms and the internal driver was almost certainly 4 ohms so an extension cab of 8 ohms would work at the resulting impedance of 2.66666.....

I think the second jack on the back panel would have been labelled 'Main Out' and would feed say a slave amp or go direct to a PA system.

I'll let you know if the manual can be found.

Edited by The Bass Doc
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My dad had a few of these in the 80s, amazing little amps for their time! I too recall that the internal speaker was an unusual impedance (3 ohms) and that their own extension speaker was unusual too. If you can get inside and check the internal speaker impedance it would help your quest.

However, if the above is correct, a higher impedance won't damage the, but the balance of power distribution will mean one speaker is working harder than the other, and you'll probably lose power...

Or you could try and ask them about it...
[url="http://www.polytoneamps.com"]www.polytoneamps.com[/url]
...you may have to call the US though, I think their website was made in Powerpoint and they don't do email!


Edit: found this, not sure how helpful it is:

Polytone typically used Eminence speakers. Make sure you match the
ohms since Polytone did not use a standard-at-the time speaker
commonly using either 2, 3 or 4 ohm speakers.

MINI-BRUTE AMPLIFIERS

Teeny-Brute: 60 watts RMS into 4 ohms
one 10" speaker
Mini-Brute I&II: 80 watts RMS into 4 ohms
one 12" speaker
Mini-Brute III&IV: 100 watts RMS into 3 ohms
one 15" speaker
Mini-Brute V: 110 watts RMS into 2 ohms
two 10" speakers


SIDEKICK CABINETS

Sidekick cabinets are compatible with each of the above models and do
not have to be matched with a similar model.


MONITOR CABINET

TB10: 10" speaker - 4 ohms
MB12: 12" speaker - 4 ohms
MB15: 15" speaker - 4 ohms

Edited by brensabre79
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Got the back off... it's full of fluffy spongy pink stuff! Wasn't sure what it was so I wore gloves. :)

The speaker has no brand on it that I can see - it just has the following:
12601
67.8549
Putting my cheap multimeter across it measured at 3.1 ohms.

I had a search on Google for the number and I did find mention of a Eminence 4ohm 12inch 50 watt RMS speaker #12601

I'm not sure if that's right as a small label on the amp doesn't make sense - it says it runs on 120 volts 60Hz, and has 135 watt, output 75 watt 4ohm
The reason this doesn't make sense is that I'm in the UK and we have 240V 50Hz supply... the amp has run happily in the UK since the 80's so I can only think it was modified for the UK when sold to my Dad - Mum can remember buying it from a shop in London that ordered it in for him but doesn't know if it was modified or anything.

So really I'm looking for a cabinet that also handles 50 watt and rated at 4ohm, in whatever size best suits the sound?
I'd like a little more low-end and less top ideally... so if I can find a 15 inch 4ohm, would that be the best option?

I'm not against making a cab if I need to... though I'd need some instructions!

With a second cab, is this likely to compete with my Peavey TKO115 Sheffield? I had planned to replace it with something like the TC Electronic BG250 after recommendations on this forum, but this route seems like it may be considerably cheaper and I like the idea of having the flexibility of a rehearsal amp that I can just add a cab to for gigs.

Edited by Magic Matt
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Look up Mambo amps - sort of Polytone inspired, but they do also make simple extension cabs using modern Eminence speakers. Personally, I wouldn't run an extra cab. Its already running into 3 or 4ohms, and the power amp is in a small sealed box stuffed full of glass fibre insulation. As a friend of mine often says.."what could possibly go wrong?!"

Edited by BassBod
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Personally, I would not try to run this with any extension cab other than a Polytone one designed for the job... Or a homemade copy of one with the correct driver. Even looking at forums online where people have replaced the internal speaker in their polytone with a JBL or something the results have not been great.

The reasons are that the Polytone amp has quite a character to the EQ - it's not flat - this is to get the most low end response out of a tiny cabinet. If you use a 15" cabinet with it it will sound different, and the end result will be the combination of the two cabinet sounds. not something that's altogether easy to control with the basic EQ on the amp.

Secondly, as you have now seen, the amp is packed full of fibreglass. Running it with an extension cab could lead to the amp getting hotter...

From the sounds of things, the sound you're after isn't one the Polytone does well. I've heard many say that they very much have their own sound, and you either love it or hate it.

If you're up for building your own cab though. Why not take a look at [url="http://www.billfitzmaurice.com/"]Bill Fitzmaurice's[/url] web site and invest in a reasonable secondhand head?

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Ah, I didn't realise it would be tuned like that... the output from it to the desk is fairly flat, but I guess that's before any speaker EQ etc... Polytone ext cabs are as rare as hens teeth in the UK.

[font="helvetica, arial, sans-serif"][color="#282828"]Wow - those cabs really do look unique! I like! Not sure I have the skills though....[/color][/font]

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