Polytone Mini Brute I

[JPG]

The volume pot on a Polytone is a linear taper. On a Fender, etc., it is logarithmic taper. On the Polytone 1 is about ten percent power, 4 is 40 percent, etc.

I always set my amp volume at 8 on my Polytone for gigs and adjust the guitar volume to suit. The sound is strong, loud,and clean.

Main out is preamp out. It's a line level output that you can run to your PA board.

I use a Polytone extension cabinet so I don't go too low on the total impedance. Don't drop below 3 ohms.

Thanks, Greentone.
Actually that was what I did. I had my amp exactly at 8, and played with the volume on the guitar. People at the gig reported no problem hearing my guitar.. but with 7 people on stage i felt I had to fight a bit and play a bit harder than I'd like.

So, asking you the same question as I did to Hammertone, I may use a one, two or even four speaker cabinet as long as it is 4 Ohms?

Thanks again!

[Greentone]

If you use an other than 4 ohm extension cabinet, the load will get apportioned unequally between the internal speaker and the extension.

I highly recommend using a Polytone cabinet. They come up for sale regularly.

[JPG]

If you use an other than 4 ohm extension cabinet, the load will get apportioned unequally between the internal speaker and the extension.

I highly recommend using a Polytone cabinet. They come up for sale regularly.

So maybe that's why Hammertone mentioned the switch to turn of the internal speaker....
Thanks, I'll have to start looking for a Polytone cabinet, then!

[Greentone]

I think so.

[Hammertone]

The speaker in my Baby Brute is a replacement rated at 8 ohms, some kind of fairly heavyweight old Celestion. The original speaker is sitting in a box, waiting to get reconed (been waiting for @30 years at this point, I think). I have used my Baby Brute (1x8" internal speaker switched off) with a variety of 4 ohm cabs, including:
-2 x 10" cab
-2 x 12" cab
-4 x 12" cab

I've also used it with 8 ohm cabs, including:
-1 x 12" cab
-2 x 12" cab
-1 x 15" cab
with the internal speaker either connected (for a total load of 4 ohms) or disconnected (for a total load of 8 ohms).

They all sounded great to me. I find the little 8" is useful with the 1x15" setup to brighten up the sound, and turn it on or off depending on the room. I've used it for guitar as well as upright bass - works great for either.

[Eck]

Your amp is rated 3ohm. Your speaker is probably 8ohm and the speaker out is parallel to internal speaker. If you add an 8ohm extension cab you’ll end up with 4ohm load on your amp. If you add a 4ohm extension you end up with (4*8)/(4+8) = 2.6ohm, putting too much load and drawing too many amperes. (Funny less ohm means more load.) Depending on the amount of kgs or pounds you like to carry, you may have 1 8ohm speaker, 2 16ohm speakers parallel, 2 4ohm speakers in series, or 4 8ohm speakers of two pairs I series and pairs parallel. These setups all draw the same amount of power but when you compare the efficiency of the individual drivers you will usually end up with more volume for more surface. For each doubling of drivers add 3dB. Good luck!


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[JPG]

Hi guys, thank you for your replies.
I've been reading a bit about it - learning about this a bit slowly, as time permits.


So.. my amp says "3 OHM 100 W OUTPUT"
May I assume the speaker is a 100-watt?
It's a 12-inch. I opened the amp, took a couple of photos (useless as they came out blurred(!) and it's a big black speaker with just some numbers on top (I'll open it again tomorrow for a proper picture)


I found the following online. All info is slightly different ... but I think I have:
* a 1985 MINI BRUTE I model
* 3 OHM 100 WATT
* 12'' speaker (100 or 80 watts RMS speaker?)
* minimum external impedance is 4 ohms (according to manual)


- - - - -




according to this link Polytone Schematics
mine is the 1985 model - the previous ones don't have a Mid control knob


according to this manual http://www.modernguitarist.com/wp-co...mini-brute.pdf
"Minimum external speaker impedance is 4 ohms. If improper impedance is used, the amplifier will operate extremely hot, which could cause damage. Much better results can be achieved by using our Sidekick cabinet for extra power."


Polytone Sidekick Speakers | TalkBass.com
from the manual:
**************************************************
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


*************************************************

[Greentone]

Your big black speaker with numbers on top sounds to me like the original CTS 3 ohm speaker. It has a huge magnet. It will handle the rated power of the amp if you don't play on 10 with a RAT pedal .

Enjoy. Also, the amp seems to last and last.

[Hammertone]

The bottom line is that any external cabinet with any number of speakers of any size will work fine, so long as the impedance is correctly matched to the specs from Polytone as mentioned.

Almost all standalone cabs are rated at 4 ohms or 8 ohms or even 16 ohms. Many 4x12" cabs allow one to choose between running at 4 ohms or 16 ohms. You do not need a Polytone Sidekick cabinet or other powered cabinet unless that is what you want to get.

[Eck]

The speaker (driver) has written at the back how much ohm it is. Normally 3ohm 100W means it delivers 100 watts into 3 ohms. Good amp, many amps overheat or break at less than 4ohms. If there is a polyfone extension cab for it, you can probably see what ohmage it has and find any other that has same number. That will give the impedance that your amp functions best with.
For a transistor ab amp-that’s what I guess it is, 100w into 3ohms probably gets 60-65 into 8. But higher resistance speakers are usually more efficient.


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