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  1. #1

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    Hello folks. I've recently become the owner of an old Mini Brute IV, the version with the 15" speaker, reverb, distortion circuits, bright switch etc.

    I'd read a lot about the reverbs in Polytone amps being notorious for not functioning properly, and this one didn't let me down. I had to open it up and remove a broken spring inside the tank, and now it's (sort of) working.

    But now comes my new problem. The reverb needs to be cranked all the way up to get it to where I like it for certain sounds. But with this comes a ton of hiss and noise, sounds almost like I've kicked on a distortion pedal at high gain. Even medium settings introduce a fair bit of hiss and take away the pristine-ness of the clean amp sound.

    Just wondering if this is normal at all. Could it be due to the broken spring making the reverb less wet and needing to be turned up too high? I thought I'd be able to push the reverb fully wet without much additional noise. Any tips or advice would be appreciated. Cheers!
    Last edited by Hood; 07-06-2021 at 08:37 PM. Reason: Line breaks

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  3. #2

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    I don't own a polytone anymore but w all the problems w their reverb I'd probably just buy a reverb pedal and be done w it.

  4. #3

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    Polytone amps have reverb tanks in a compromise space...side of the cabinets. This results in lots of vibrations and deterioration of the delicate spring/coil/magnet assembly in the tanks. And, they aren't the best sounding reverb to begin with. A pedal isn't a bad idea.

  5. #4

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    Congrats for a great amp! I have a MBIV too and I think it is one of the best Polytones!

    I think Your tank is broken. I get the decent amount of reverb just turning it on 1 or 2. If I turn more the sound gets metallic and hum increases too much.

    The reverb tanks are cheap to change. There is a 7 mark code, You must buy one with similar code. Buy Accutronics if You can, not the substitutes. The Accutronics are softer, more musical.

    I have once decreased the exessive background hum of a Polytone reverb by turning the tank 180 degrees. And once just grounding the tank to the chassis of the preamp did the trick.

    So a pedal is not the only answer if You don’t mind some tinkering.

    I personally try to avoid pedals in my jazz rig so I need a combo with a working reverb.

    Good luck with Your nice amp!

  6. #5

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  7. #6

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    Quote Originally Posted by Hood
    Hello folks. I've recently become the owner of an old Mini Brute IV, the version with the 15" speaker, reverb, distortion circuits, bright switch etc.

    I'd read a lot about the reverbs in Polytone amps being notorious for not functioning properly, and this one didn't let me down. I had to open it up and remove a broken spring inside the tank, and now it's (sort of) working.

    But now comes my new problem. The reverb needs to be cranked all the way up to get it to where I like it for certain sounds. But with this comes a ton of hiss and noise, sounds almost like I've kicked on a distortion pedal at high gain. Even medium settings introduce a fair bit of hiss and take away the pristine-ness of the clean amp sound.

    Just wondering if this is normal at all. Could it be due to the broken spring making the reverb less wet and needing to be turned up too high? I thought I'd be able to push the reverb fully wet without much additional noise. Any tips or advice would be appreciated. Cheers!

  8. #7
    Thanks folks for the replies. I'm going to try a new tank soon and see how that goes. For the pedal suggestions, I've got a couple of options there already but I just hate the idea of the amp not being fully functional if it's possible to fix. Plus it's nice to just plug in the guitar and start playing without other stuff lying around getting in the way. Cheers again!

  9. #8

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    I have the same Polytone, with the silver P logo on the bottom left,

    where da hell did you find the reverb? i once opened it up because the hum was annoying and when i saw the inside i was like hell nah lol and called it a day

  10. #9

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    The reverb tank is behind pink fiberglass batting on the right side of the cabinet as you peer into it from the back side (with the back cover removed). It plugs in with two RCA jacks and comes out of the cabinet with, IIRC, two screws at opposite corners of the tank--maybe four.
    Is noisy reverb normal? (Polytone Mini Brute)-mb-reverb-tank-jpg

  11. #10

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    I think that it may be at least partially due to magnetic interference from the output transformer since the reverb tank is so close to it. I noticed that the further I moved the tank away on mine the less hum I got. That said, I was moving it away on a trial basis without it being attached to the cabinet any more. Putting it all back together there isn't much space to move the tank. You can try wrapping the tank in something like mu metal and see if that helps. I haven't done that to mine yet. I also doubt a new tank will make any difference, FWIW.

  12. #11

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    Quote Originally Posted by maxiim
    I have the same Polytone, with the silver P logo on the bottom left,

    where da hell did you find the reverb? i once opened it up because the hum was annoying and when i saw the inside i was like hell nah lol and called it a day

  13. #12

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    thanks man!

  14. #13

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  15. #14

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    hm i opened it up and i didnt found a reverb anywhere at all, start thinking that it might be digital, its not on the sides (yellow fiberglass) its not in the preamp above, and i doubt thats it at the bottom where the transformers are, there couldnt be enough space for a tank

    odd

  16. #15

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    Quote Originally Posted by maxiim
    hm i opened it up and i didnt found a reverb anywhere at all, start thinking that it might be digital, its not on the sides (yellow fiberglass) its not in the preamp above, and i doubt thats it at the bottom where the transformers are, there couldnt be enough space for a tank
    odd
    Odd indeed… is there a Reverb pot and reverb sounds?

    Did You dig behind the fibre glass, from the right side (looking from behind)?

    Use the gloves before grabbing that devil’s material or You’ll have an itch for a week!

    Is there two cables with RCA connectors?

  17. #16

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    Quote Originally Posted by Herbie
    Odd indeed… is there a Reverb pot and reverb sounds?

    Did You dig behind the fibre glass, from the right side (looking from behind)?

    Use the gloves before grabbing that devil’s material or You’ll have an itch for a week!

    Is there two cables with RCA connectors?

    here are some pics

    Is noisy reverb normal? (Polytone Mini Brute)-viber-bild_2021-08-08_17-43-24-922-jpgIs noisy reverb normal? (Polytone Mini Brute)-viber-bild_2021-08-08_17-43-24-189-jpgIs noisy reverb normal? (Polytone Mini Brute)-viber-bild_2021-08-08_17-43-23-892-jpgIs noisy reverb normal? (Polytone Mini Brute)-viber-bild_2021-08-08_17-43-22-312-jpgIs noisy reverb normal? (Polytone Mini Brute)-viber-bild_2021-08-08_17-55-41-605-jpg


    super odd yooooooo

    its like nowhere i cant imagine where it could be there literally no space left, its not behind the isolation too

    did polytone build digital reverbs in those models?

    am i missing something here?lol



    when i turn up the reverb it gets more noisy too

    though the reverb doesnt soud very good

  18. #17

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    Thanks for the pics. It is a bit newer model than my ’red knob’ amp but I believe they are mostly similar.

    Someone else might know if it is a digital reverb but look in the second pic: where does the two grey cables go? Could they lead us to the tank?

    The reverb sound of MiniBrutes is so cold that I too thought it digital at first. They had to use short tanks with cheap (?) springs so the the sound is usable only in small portions.

  19. #18

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    good call herbie ill see if i its beneath the upper fiberglass

    when i sent those pics i was looking at that one pic above the speaker thinking;could it be?

    ill update when i know further

    though i saw that they use folded line reverb tanks? i wonder why they are so shitty in the polytone, i know that the Rolands JC series has them and they sound awesome ;.:.; who knows