What is it about Polytone amps?

**billy21** · 02-28-2019, 09:40 AM

Originally Posted by mr. beaumont

There's 2 types of Polytones, those that never worked and those that'll work forever.

So if you find one that works, just enjoy it. I've been enjoying mine for over a decade...

The oldest sounds better.
The weak link in the early ones is the obsolete LM391 chip. But it can be replaced with currently available components. The mod is similar to the later polytone versions of the circuit. I noticed scoping some of them, the felt covered are more thermically stable than other same period models.
I can’t consider the small reverb tank an issue on this amp.
There’s no enough space to put a long reverb tank inside as fender do.
So there’s only one type of polytone, all works and suddenly not anymore.

**Greentone** · 02-28-2019, 11:41 AM

billy21,

I like the felt ones the best, too, followed by the diamond Tolex (Boltaflex, I believe). The even earlier ones covered in heavy-duty Tolex are also great. I actually like them all, but I don't have any use for a Sonic Circuit per se. In fact, I like the Polytones with just two tone knobs better than the ones with three (i.e., a mid). Simple works!

**Nils** · 02-28-2019, 03:01 PM

Originally Posted by billy21

the reverb works?
If you ever looked inside, is it equipped with 4000mf caps?
jesus, that bomb is super compressed! i’m courious about caps value

Billy 21,
Sorry for late reply. But 1) No, I don't have any plans of selling it - sorry. 2) Yes, the reverb works as it should (though I'm not crazy about it - prefer a pedal). 3) I looked inside when I bought it, but didn't check the caps. Am fairly sure everything apart from the speaker is stock, though.

**billy21** · 02-28-2019, 04:45 PM

Originally Posted by Nils

Billy 21,
Sorry for late reply. But 1) No, I don't have any plans of selling it - sorry. 2) Yes, the reverb works as it should (though I'm not crazy about it - prefer a pedal). 3) I looked inside when I bought it, but didn't check the caps. Am fairly sure everything apart from the speaker is stock, though.

thanks

**vintagelove** · 02-28-2019, 04:47 PM

Originally Posted by billy21

thanks

Ill keep an eye out for one, I’ll pm you if I come across it.

**Greentone** · 02-28-2019, 05:23 PM

Billy21,

I have some of the Polytones where the power supply caps are the impressive 4000mfd values. They work well enough. (They are 8200mfd in the big amps. The Baby Brute power amp only produces about half the power that the big Polytone power amps produce.)

**golfus** · 02-28-2019, 06:18 PM

I also like the simplicity of the earlyer brutes. But mine is dead. Not wanting to be without that sound I´ve bought a Taurus II. It has two channels, reverb, a weird effect, distortion and master volume.It has also two 6" speakers in the sides. One 12" and 125w rms. The weird thing is that I alwais thought that one of the big reasons for the polytone sound was that the power amp was working at full trottle. But this master volume sounds quite the same.

**GNAPPI** · 02-28-2019, 06:23 PM

Originally Posted by mr. beaumont

There's 2 types of Polytones, those that never worked and those that'll work forever.

So if you find one that works, just enjoy it. I've been enjoying mine for over a decade...

I'll be darned. I never heard this but it's good to know.

**Easy2grasp** · 02-28-2019, 06:38 PM

I offered to sell my 1980's diamond tolex MBIV a little while back. But last week I got a 1999 Gibson L-5 WesMo, plugged it into the MB and thought, " Damn I'm glad I didn't sell this wonderful amp!" They went together like soup and sandwich.

**billy21** · 02-28-2019, 07:45 PM

Originally Posted by vintagelove

Ill keep an eye out for one, I’ll pm you if I come across it.

thank you!!

**billy21** · 02-28-2019, 07:52 PM

Originally Posted by Easy2grasp

I offered to sell my 1980's diamond tolex MBIV a little while back. But last week I got a 1999 Gibson L-5 WesMo, plugged it into the MB and thought, " Damn I'm glad I didn't sell this wonderful amp!" They went together like soup and sandwich.

yes man!
I got same wes and mbIV.. they match!
I also like to plug the wes on my twin reverb.
Just courious, what kind of string do you use on wes?
MbIV for my 175.

**billy21** · 02-28-2019, 08:00 PM

Originally Posted by golfus

I also like the simplicity of the earlyer brutes. But mine is dead. Not wanting to be without that sound I´ve bought a Taurus II. It has two channels, reverb, a weird effect, distortion and master volume.It has also two 6" speakers in the sides. One 12" and 125w rms. The weird thing is that I alwais thought that one of the big reasons for the polytone sound was that the power amp was working at full trottle. But this master volume sounds quite the same.

which problem had? dead?
the secret of the sound is in the preamp, wooden cabin and speaker.
What do you mean for full trottle?

**billy21** · 02-28-2019, 08:07 PM

Originally Posted by golfus

I also like the simplicity of the earlyer brutes. But mine is dead. Not wanting to be without that sound I´ve bought a Taurus II. It has two channels, reverb, a weird effect, distortion and master volume.It has also two 6" speakers in the sides. One 12" and 125w rms. The weird thing is that I alwais thought that one of the big reasons for the polytone sound was that the power amp was working at full trottle. But this master volume sounds quite the same.

power amp is not important.You can have a polytone sound using another power supply.

**billy21** · 02-28-2019, 08:11 PM

there are many people who love the poly!
have you ever had vibrations problems?

**golfus** · 02-28-2019, 08:13 PM

I´ve been thinking about using one of those ice-power 180W amps. But if I find a tech who does it for me, he could as well fix the existing one.The problem is finding the tech.And the fact that I have other amps and have been busy.

**golfus** · 02-28-2019, 08:28 PM

Originally Posted by billy21

which problem had? dead?
the secret of the sound is in the preamp, wooden cabin and speaker.
What do you mean for full trottle?

Sorry Billy. Didn´t see this post.

The power amp emmited white smoke. Cement resistors burned and who knows what else. In hollydays I´l be serious about fixing it. But now that I have the Taurus II I´m not in a hurry. But I love the MB lll. There is something hypnotic about the 15", and the simplicity...For me it´s a "logical" sounding amp.

As for full trottle I was trying to say that as far as I know, minibrutes deliver their full power all the time and the volume acts as a gain. I know that my english could be better...

Vibrations: I think my neighbours can feel them.

**sgosnell** · 02-28-2019, 08:31 PM

If the magic smoke escapes, the amplifier is dead. Everyone knows that.

**golfus** · 02-28-2019, 08:41 PM

The preamp still works with the same OT. I connect it to the AMP IN of a 80´s Peavey and it´s in the polytone ballpark.But it´s a mess.

**billy21** · 02-28-2019, 08:46 PM

Originally Posted by golfus

Sorry Billy. Didn´t see this post.

The power amp emmited white smoke. Cement resistors burned and who knows what else. In hollydays I´l be serious about fixing it. But now that I have the Taurus II I´m not in a hurry. But I love the MB lll. There is something hypnotic about the 15", and the simplicity...For me it´s a "logical" sounding amp.

As for full trottle I was trying to say that as far as I know, minibrutes deliver their full power all the time and the volume acts as a gain. I know that my english could be better...

Vibrations: I think my neighbours can feel them.

hello,
you probably burn the 391 chip and then the resistors all around it.
It’s not difficult to fix, just try to find a technician with time to spend.
The power amp is prone to overheat , and as you described I suspect your bias was setting too warm and burn everything.
about vibrations: you can solve it easily:
1) there’s some foam between preamp and chassis, it could be disintegrated and give you buzz. replace it.
2)Speaker screws are loosing.
3)buzz from microphonic brite normal dark switch (spray it). you can check it pressing down the button you can heard a weird buzz.
4) losing pots, spray it or put a bit of greese inside.
5) reverb tank problem
6) the worst: bad speaker coil

**billy21** · 02-28-2019, 08:55 PM

Originally Posted by Greentone

billy21,

I like the felt ones the best, too, followed by the diamond Tolex (Boltaflex, I believe). The even earlier ones covered in heavy-duty Tolex are also great. I actually like them all, but I don't have any use for a Sonic Circuit per se. In fact, I like the Polytones with just two tone knobs better than the ones with three (i.e., a mid). Simple works!

The olds are great, and easy to use.
The two tone are better, but sometimes I play some venues that have MBrutes with sonic.
Obviously I set the sonic off, but sound good too! especially the V (another
model that i like) and IV
George Benson is still using the latest V (15 speaker), johnathan kreisberg is using IV, Kurt rosenwinkel the II.
Lots of them combine a tube amp like fender twin or deluxe rev with polytone and blend the stereo sound.
Do you ever had the V?

**Durban** · 03-02-2019, 07:43 PM

[QUOTE=Greentone;937051 The Baby Brute power amp only produces about half the power that the big Polytone power amps produce.)[/QUOTE]

Hi GT, is the 8" speaker 4 ohm & what power do the Baby Brute have approx?

i have a couple of Mega B non-sonic orig Eminence 8" 4ohm .................they bark

**Greentone** · 03-02-2019, 09:32 PM

The Baby Brute first had CTS 4ohm 8" drivers installed in the diamond tolex series. In the black, regular tolex with black cloth grille, the driver was an Eminence 8" 4ohm model. Both amps were 75 watts output at 4ohms.

**lawson-stone** · 03-02-2019, 10:35 PM

Originally Posted by Greentone

The Baby Brute first had CTS 4ohm 8" drivers installed in the diamond tolex series. In the black, regular tolex with black cloth grille, the driver was an Eminence 8" 4ohm model. Both amps were 75 watts output at 4ohms.

I'd add, having had extensive experience with 3 different Baby Brutes, that it is a LOUD, BIG 75 watts. Those little amps almost have to be bolted down to keep from blowing over. They belt it out.

**billy21** · 03-03-2019, 08:51 AM

Originally Posted by lawson-stone

I'd add, having had extensive experience with 3 different Baby Brutes, that it is a LOUD, BIG 75 watts. Those little amps almost have to be bolted down to keep from blowing over. They belt it out.

I don’t think it goes up to 40W output.
75watts is peak power.

**Nils** · 03-03-2019, 09:33 AM

Originally Posted by Greentone

The Baby Brute first had CTS 4ohm 8" drivers installed in the diamond tolex series. In the black, regular tolex with black cloth grille, the driver was an Eminence 8" 4ohm model. Both amps were 75 watts output at 4ohms.

GT:
Just out of curiosity, is the diamond tolex series the first series of BBs, or did they make these even before? Do you happen to know which year the earliest ones were made? (Never seen any felt ones...)