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Joyo AC-40 Review and Mods

Discussion in 'Amp Tech Center' started by Pontiac51, Apr 11, 2021.

  1. Pontiac51

    Pontiac51 TDPRI Member

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    I had this Amp for over a year now and it beat the Roland Cube Street and the VOX Mini 5 in my direct comparison. I am using it as my main protable amp every week, most of the time with electric guitars.

    Pros:

    Sound: The sound is clear and crsip (not as digital or boxy as the Cube and the Mini). The AC-40 works well with pedals. I have used all kind of pedals in front (mostly the TrueTone series by Harley Benton) and it never dissappointed.

    Reverb: Both inputs have geat Reverb. You can go for great hall here, the Roland and the VOX don't sound as big.

    Cons:

    Noise: Yes, it does hiss (at 30db or the volume of a whisper). Even if all knobs are at 0. But as soon as you play that's gone. It changes to a zing in the the higher regions (5-9) and is gone back to a background hiss at 10. Peaks at 7 with 42db (45db would be a quiet flat) sounding like a misstuned radio. But despite all that it is very quiet. Not silent, but quiet.

    Feedback: If you get really close, feedback can occur.

    Weight: Heavy for it's size the amp ways in at 8kg. 2kg of that is the battery, which is a 12V lead battery. At least its sealed. So, no spill hazard as written in the manual.

    Options: 1 AUX IN, 3-Band EQ for guitar, 3 FX for guitar, 1 FX for microphone. No headset plug!

    Conclusion:

    You might say there are more cons then pros. But I kept this one because of the clear and open sound and because it accepts pedals that nicely.

    [​IMG]
     
    Last edited: Apr 11, 2021
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  2. Pontiac51

    Pontiac51 TDPRI Member

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    MOD #1 Weight Reduction

    This buggered me from the beginning. The battery in this thing is not only heavy, it is stone age technology. There are much more suitable power choices for this application.

    As an RC hobbyist I kew about the alternatives: NiMH, LiPo, LiFePo and everyones favourite LiIon. NiMH is normally not able to sustain high loads. LiPo is very powerfull, but has its hazards and you cannot let it sit for a long time without damage. In addition the power levels are wrong (for 12V). LiIon has the same power levels as LiPo and it does not last as long as LiFePo does (number of recharge cycles). LiFePo has lower power levels better suited for 12V application, has high energy rates and can be recharged more often. And its more environment friendly. ;-)

    So, I bought a 4,5mAh LiFePo4 (originally it was 7Ah with the lead battery) for 45 Euros. Weight: ~400g!!! Since the LiFePo4 can use nearly all of its charge while a lead battery is under voltage at around 50% this summed up to 9Ah while saving 1,6kg. That is 80% in weight saving and a near 30% energy rise!

    https://enerprof.de/en/lifepo4-batt...6/enerpower-lifepo4-12v-12.8v-4.8ah-62wh?c=25

    [​IMG]

    OK, lets open it up. No secret here, remove all the screws around the back panel and the handle and the amp comes right out.

    [​IMG]
    [​IMG]

    Now unplug the 15V DC power cable from the board. The are glued in, but a little persevarence gets them out. Also, unplug the battery cable on both ends. BATTERY SIDE FIRST!

    [​IMG] [​IMG]
    [​IMG]
     
    Last edited: Apr 11, 2021
  3. Pontiac51

    Pontiac51 TDPRI Member

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    The DC socket on the little board is already one with a switch so we can use this as a charge port instead. This plug will then only be used for charging, you cannot use it to run the amp! But the switch protects the amp while charging. To be able to use the switched socket you need to cut the circuit path top and bottom (do not use the connector again). I sadly destroyed my socket on the way, so I had to make a new one.

    [​IMG]
    [​IMG]

    Now we have some cables to resolder. Take the short cable you have already disconnected and connect it to the board at the BATT terminal (CW6). The DC 15V (CW7) stays empty. Clip the other plug it is not need anymore. Also clip the plug on the longer battery cable. The battery crimps stay on!

    Now solder these 4 loose ends to the solder points for the plug and make sure the red cables are soldered to the center pin! The black battery wire is soldered to the unswitched terminal and the shorter black one to the switched terminal.

    [​IMG]
    [​IMG]

    You can now use the original plug to recharge the battery without having to open amp. DO NOT USE THIS TO CONNECT A POWER SUPPLY. YOU NEED A LIFEPO4 CHARGER! This amp now runs on battery power only! But the LiFePo4 should have you going for hours and hours.

    The old battery is hold in place by two clamps each one secured by 4 screws accesible from the outside (back and bottom). If you are lucky, you only have to rebend one clamp a bit and that will keep the new battery from sliding.

    [​IMG]
    [​IMG]
    [​IMG]

    DONE!

    To make sure that you do not undercharge your new LiFePo4 (alltough the good ones are protected against that) and to always know how much juice is left you can add a small powermeter especially designed for LiFePo4.

    https://enerprof.de/en/accessories-...840/charge-indicator-for-4s-lifepo4-batteries

    [​IMG]
     
    Last edited: Apr 11, 2021
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  4. Pontiac51

    Pontiac51 TDPRI Member

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    MOD #2 Pedal Power

    Since this amp now has so much battery life (I rarely charge it, despite using it weekly), I thought: Why not power my pedals with it and save 9V batteries (which are horrible energy wise)?

    Finding a suitable DC converter online was easy, there are plenty to choose from. Either fixed ones or variable ones. I opted for a variable one, since they were easier to buy for me. Make sure it has a heatsink and can truly convert 12V to 9V, not vice versa. Mine is rated for 5A, but I would never try to use that. Currently, 200mA is enough for me.

    https://www.amazon.de/gp/product/B08TVM6LYX/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

    The trick was to find a place for the board, as it is rather large with its display and buttons. The display can be turned off. Despite this I soldered in a switch before the board, so it does not draw power if unused (should be 10mA or less, but anyway).

    [​IMG]
    [​IMG]

    New cables have to run from to the battery terminal (either the power plug or from the battery direct) to the switch and then to the IN terminal of the DC Converter. The cables from the OUT terminal of the DC converter go to the plug. Make sure its center NEGATIVE to be able to use your normal pedal power cables!
     
    Last edited: Apr 11, 2021
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  5. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    The Joyo AC40 seems to be great for buskers. That mod makes it even more so.

    Does it hum when battery powered?
     
  6. Pontiac51

    Pontiac51 TDPRI Member

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    Unfortunatly, yes. I am not sure why. Could be some crappy components or the board layout itself.

    I usually hear the hiss (around 10dB) when i turn it on, but as soon as I start playing I do not notice it anymore. Mind you, I am playing at low levels (usually do not go higher than 2). Now having it on on my workbench, the fans of my laptop seem to be louder. So, not bad?

    I have added a full description to the top. I tried recording it but the microphone on my mobile has more background noise than the amp.

    Funnily enough, the MIC channel does not have this.

    I would really like to debug this, but my knowledge is limited. Maybe any of you guys has an idea?
     
    Last edited: Apr 11, 2021
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  7. Pontiac51

    Pontiac51 TDPRI Member

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  8. Ess Eff

    Ess Eff Tele-Afflicted

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    Thx for all the info.

    I was looking at one of those recently and was considering the battery mod too.

    I thought it would end up being quite expensive so I lost interest.
    .
     
  9. hdvades

    hdvades Tele-Holic Silver Supporter

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    Glad you like this amp. I'm a big fanboy of the Vox Mini 5 Rhythm. imho it's not in the same league as this Joyo AC40 when comparing specs. The AC 40 should be superior.
     
  10. Pontiac51

    Pontiac51 TDPRI Member

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    It definitely does. I had one myself a long time, but in the end it was not enough in a band mix. The Joyo has much more power and double the speakers.

    Additionally I can create my own sounds with it. At the time I found the sounds of the VOX a bit dull. But never the less, the VOX Mini 5 is a great little amp.
     
  11. Pontiac51

    Pontiac51 TDPRI Member

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    Actually I thought that too, but the prices of LiFePo have gone done quite some in the last years. I think it is a great alternative now. Of course you need a charger, but I already hat that. And a new one is quite cheap if you don’t go super fancy.
     
    Last edited: Apr 11, 2021
  12. Pontiac51

    Pontiac51 TDPRI Member

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    Can you guys see the pics? It’s always troublesome with Google.
     
  13. Mouth

    Mouth Tele-Afflicted

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    Yes, pics are showing.

    Thanks for posting this.

    You can't use it when it's charging?

    How long does it take to charge?
     
  14. Ess Eff

    Ess Eff Tele-Afflicted

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    In my money, the amp is abt $300, the battery $79, and the charger $99.
    So almost $500.

    Not bad I guess. Dedicated rechargeable busking amps seem to go for a lot more than that.
    .
     
  15. Pontiac51

    Pontiac51 TDPRI Member

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    Correct, but you can play a really long time. I have not been charging it for months now and I use it weekly for an hour.

    If you would deplete it fully (which you normally do not) and charge is fast (which you also would avoid) it takes about 2h to fully charge. I usually charge it when it’s down to 20 percent with 1A, that takes 3 to 4 hours. This is to take care of the battery.
     
  16. Pontiac51

    Pontiac51 TDPRI Member

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    A simple charger should not be that expensive. The shop I bought it from offers them with 1.5A or 2A at 10 to 15 Euros. Of course if you go fancy you will reach the point where you are at. I have such chargers already (from RC flying), so that wasn’t a factor for me.
     
  17. Pontiac51

    Pontiac51 TDPRI Member

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    IMPORTANT NOTICE!

    I said that the amp does zing/beep on the VOLUME control from 5 upwards.

    THIS IS NOT CORRECT!

    The zing/beep is introduced by the TREBLE between 5 and 6.5. All other knobs just alter/amplify it.

    According to some helpful members of DIY Audio Forum, the amp oscillates.

    So, since I am using a preamp anyway, I fixed this rather brilliantly. ;)

    IMG_20210413_180415.jpg
     
    Last edited: Apr 14, 2021
  18. ce24

    ce24 Poster Extraordinaire

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    No EQ on mic channel is a deal breaker for me. Im only interested in a busking amp and my cube street is the best allround ive found.....always interested in looking at whats new tho.
     
  19. Pontiac51

    Pontiac51 TDPRI Member

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    Yes, the features on this amp are few and I fully understand your notion. As a very amateur singer I can live with that.

    The Roland Street is a very nice amp indeed (had one for testing), but I think it cannot compete with the sound the Joyo has. But of course this is a personal opinion.
     
  20. Pontiac51

    Pontiac51 TDPRI Member

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    Here is a schematic for what i did on the mods.

    mod-joyoac40.JPG
     
    Last edited: Apr 15, 2021
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