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Hi all. I’m new around here and new to guitar in general - only 2 years in. I’m looking at this polytone amp and the owner doesn’t have too much info about it - he plays country music. He purchased it in 1985 and says it came with a 10 inch speaker. Does anyone know more about this model? Would this be a good choice for straight ahead jazz?
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02-23-2022 03:34 PM
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That's a minibrute II I think. 12" speaker. With an adjustable mid knob stacked on the treble. Distortion stacked on volume. Looks like maybe mid 80s. I had one just like it. A really nice amp. The mid control is very useful. Distortion, IMO, not at all useful.
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If a 10", it will be a ( rare) teeny brute; if a 12", a minibrute 2 as mentioned above. Basically the same power amp; the 12 and the 10 may have slightly different speaker impedances, which would affect power output; either 75 or 100w . Looks like mid 80s. Will almost certainly need recapping, unless already done. Great jazz sound.
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Thanks for the information. He insists it’s a 10inch but it looks like it says mini brute II in the front plate.
Originally Posted by Franz 1997
From what I’m reading, caps would be the culprit if the fuses start to go?
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Some like it, but I'm not fond of the mid control.
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Then just set it in the middle and pretend it ain't there.
As others have said, I had one of these although with a silver rather than black control plate, at least if I'm remembering it correctly. It was a great little amp. I sold it to a pedal steel player, who sounded great through it, and have kind of regretted it ever since.
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Pretty rare to still have the foam grill as they deteriorate over time
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Looks like a MBII to me, but you would have to check the speaker size to be sure. Either way, they are both great amps for jazz.
Keith
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If the caps are original, they are likely to leak and draw too much current ( in the worst cases they can explode) and this can blow a fuse, or take out the mains transformer if it gets too hot. Note that there are two types of fuses in a Polytone; main fuse (s), and a ( usually) 7 amp fast fuse on top of the power amp chassis which is designed to protect against an output short circuit. One quirk of MB 2's from this era is that using the headphone jack can sometimes blow the output fuse. Originally Posted by Joao Gilberto
But a recapped and serviced Polytone is a great jazz amp, and worth the effort to maintain. The reverb pans tend to go quite often- they are just screwed to the wood of the cabinet and get banged around- but that won't stop the amp operating. One way of greatly increasing amp reliability is to get a tech to replace the power amp with a modern 200W class D amp module, which will operate into the 4 ohms of an original speaker, but still give 100W with a replacement modern 8 ohm speaker. An Eminence 250W Beta 10 or Beta 12 is the usual replacement.
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Thanks for the write up. I pulled the trigger and bought it. It seems that I should start looking for a tech who can take out a look at it and do some preventative maintenance once it arrives. I’m in NYC so I’m sure there’s somebody who knows these amps. I appreciate the tips. Originally Posted by Franz 1997
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I have a couple of Polytones from about the same era. I have never had a tech look at either of them and they work just fine. I ususally take a backup with me when I use one of the old Polytones on a gig, but I haven’t had any issues with them yet. Originally Posted by Joao Gilberto
Keith
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The trouble is that leaking power caps don't show any obvious external symptoms to the non-tech person until they blow. Internally, they are leaking electrolyte, and getting hotter and hotter as they pass too much current. I speak from costly experience, with an 80s diamond-era Poly. The main caps blew, and most of the power amp chips and transistors had to be replaced, after the toxic mess was cleaned out. The obsolete components were available then, but might not be now. Changed caps seems like cheap insurance to me. Originally Posted by floatingpickup
But that said, I have a pro friend who gigs often with another diamond-era MB2, and that's still going after 40 years. He's just lucky..
Clint comes to mind..
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Well, in a tragic turn of events (not really), the seller has discovered that the reverb doesn’t work. He refunded me a bit of the selling price and has sent the amp over to me.
Could repairing the reverb be a Sunday DIY project? Is it even worth fixing it?
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I don't know your taste in reverb Joao, but I never once used the reverb in my mid 80s MB II. It worked, but didn't sound nearly as good as either of the reverb pedals I always use. (In fact, I never turn on any in-amp reverb anymore.)
If you really need it, different story. But if you don't ... the discount could make the amp worth it to you even w/o a fix. It could be an easy fix too.
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Originally Posted by Joao Gilberto
There is a solid chance that it is just the reverb tank. A new one is like 30 bucks and sound much improved to the stock tank. Next step is a blown IC. Also an easy fix.
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Congratulations on your 1985 MiniBrute II.
Try a new reverb pan and see how you like the built-in reverb. Easy afternoon fix.
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Thanks for the advice. Maybe it’s time to have a tech take a look at my old Poly’s to make sure I don’t have a similar experience. I always assumed they didn’t need as much attention as vintage tube amps, but I guess they do need to be checked out after 40 years. Originally Posted by Franz 1997
The trouble is that leaking power caps don't show any obvious external symptoms to the non-tech person until they blow. Internally, they are leaking electrolyte, and getting hotter and hotter as they pass too much current. I speak from costly experience, with an 80s diamond-era Poly. The main caps blew, and most of the power amp chips and transistors had to be replaced, after the toxic mess was cleaned out. The obsolete components were available then, but might not be now. Changed caps seems like cheap insurance to me.
But that said, I have a pro friend who gigs often with another diamond-era MB2, and that's still going after 40 years. He's just lucky..
Clint comes to mind..
Keith
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Congrats! You found a classic!
In one MB that I had one of the reverb springs was totally detached. I found if lying on the bottom mid the glass fiber. Bought a new tank and it worked again.
The reverb is ok if You need just a bit of it. For Dick Dale sounds it is too metallic.
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So I think when it arrives Monday, I’ll pull the tank and get the part number. Not really for the sound (I just got finished listening to some demos, its not to my taste), but just for the sake of completeness. Thanks for the replies everyone - it’s been helpful and I’ll update here when it arrives.
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Just to be clear, there is nothing bad/wrong about the polytone reverb circuit. It is solely the tank that people don't care for the sound of. Get a new medium tank (I think I used mod) and you'll be very happy. Even if you replace it and it still doesn't work, when you swap out the ic or fix whatever the issue is in the Reverb circuit, you'll still want that new tank in there. You can lose in purchasing a new one. Originally Posted by Joao Gilberto
Enjoy!!!
PS, you should also buy yourself a cheap EQ pedal. You can really get a vast amount of tones with one of those into a poly. You can also get quite the volume boost while remaining clean.
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Originally Posted by Joao Gilberto
before you spend,
check rca connectors are ok and plugged in.
the wires soldered to the c board, flimsy and often come off,
check tank springs
some of the tanks are interchangeable. depending on exact model length
if a 10" speaker maybe same as Baby Brute - 2 spring shorter/ish length tank. hard to obtain.... trust me.
determine what Poly it is. Mega Brutes have reverb units as well i will update with regards to springs and length
Sometime the output driver on ic board is gone,
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