Sunday, January 23, 2011

Altec Lansing ACS33 (2.1 for PC)

Although not really hifi, having a set of decent sounding speakers for the PC does help when you are listening to MP3, watching movies, accessing Youtube, etc - especially when you are used to a decent sound system!

I choose the Altec Lansing ACS33 (2.1) many years ago as I could not convince myself to invest on a pair of nice Klipsch speakers for the PC ($700+ vs about S$135 for the ACS33)!

ACS33 2.1 PC speakers
In stock form, sounds leans toward bass and can sound boomy. Details and highs were acceptable.

Hence I decided to investigate possibilities on improving the ACS33.
With bottom half of the sub uncovered
I removed 6 screws  from the bottom of the sub to reveal the above pix.

Closeup of PCB (after substitution)
Perform the following on the PCB:
  • replace the 1uF EC with a poly (yellow)
  • replace non-essential 1uF with poly (orange)
  • replaced 4x0.22uF (green) poly with 0.15uF Vishay BC (grey) - makes largest audioble difference
  • replaced the 2 caps for filtering power supply with Rubycon 2,200uF
  • add a heatsink to the voltage regulator as it gets hot
  • changed a few caps on the right side of the pix (though not really necessary)
The results?

Bass was firm and quite respectable. High and mids sound pretty decent (to myself)! Don't think I will be shopping for a replacement anytime soon...


  1. 7 screws actually
    nice modification, will give it a try also.

  2. Hey I have a similar ACS33 and it went dead last week, can you point me towards a few things:
    I suspect the output power is the culprit as I am getting the 110V a.c. coming in but not leaving the transformer. I would want to bybass the a.c. step-down however so where could I tap the circuit and attach an adapter? If that is not possible, how can I troubleshoot to determine if it is only the transformer or more components that are damaged?

  3. Past incidents normally include a blown fuse, when the transformer goes e.g my Marantz CDA-94 and a Carmer M-02 (many years ago).

    Otherwise could be something else along the way.

  4. Ok thanks, the fuse looks good. I got a pin out for the cable so I surmize that I can tap the circuit there and supply the d.c. voltage to power the speakers and see what happens.

  5. How do these speakers compare to newer models from Altec Lansing? Like the VS2621's?

  6. Apologies as I have not been in the market for new PC speakers for a number of years. Hence have not heard the newer models.

  7. tengo un problema con el potenciometro , se daño ando buscando donde lo vendan

    1. Apologies as you would need to source from local electronic shops in your part of the world. Alternatively maybe try international companies eg element14, rscomponents, mouser, amazon, dhgate, etc

  8. Recently developed a short in the main cord that plugs into the sub. Assuming the solder is starting to let go from wear and tear I thought of replacing the whole set until I stumbled across your Mod post. I still appreciate the power of the ACS33 and have been searching for something comparable for the same money to no avail. It's true what they" they don't make them like they used too". On any account I was wondering if you might mind sharing your mod in more detail with me. This is something I would like to do but need more specific instructions.

    1. Hi Phil,

      The changes performed are all as per listed in point form towards the bottom of the post - no other changes done.

      If I remember correctly, once you open up the unit (via the bottom panel), only work on the PCB. High-lighted item(s) are the caps to be upgraded for audible improvement. You could use Wima, etc as well.

      DO NOT loosen the screw attaching the speaker to subwoofer - can be frustrating putting it back!!!

  9. my acs33 stopped working after making a buzzing noise. I opened it up thinking just a fuse but found that one of the parts on the heat sink BA5417 with 15 pins has burnt up. Can i desolder and resolder that part and fix my speakers? I would like to know how to find part and where to order if anyone could help. I would like to show a pic but dont see a place to ad photos here

    1. Just checked element14 and it is available eg

      You can select your country of residence (or closest) via CONTACT US near top left corner of the webpage.

  10. I found your page while trying to repair my own system. I'm pretty new to this sort of thing, so I'm hoping I can find the components with the descriptions you've provided (not really knowing much about them personally...)
    Doing some more searching for images I found what appears to be a Chinese hacker's blog post with their own personal change. If the translation (plus my guessing) is correct, then this person is adding a variable resistor to change the tone(?) or perhaps volume of the bass output.

    1. Volume of subwoofer output as Pin-11 is input pin#1

  11. Dang it!!! Wrote you a long letter WCK, and it poofed into cyberspace. Bottom line is 1st, thank you for being around to ask questions to since Sunday, January 23, 2011.
    I have an acs33 system. Works fine. But a neighbor complained it was shaking her walls lmao. So I disconnected it. Now she is gone and I want to hook them up again, but there is a change in my entertainment system. I bought a RCA 50" flatscreen. I have my laptop hooked to it with a HDMI cable. All is good, 'cept I am not sure how to configure the Altec acs33 speaker system. Any clues?

    1. Just connect the mini-jack from the ACS into the green output on the laptop. Connection between the various components of the ACS are unique and would only fit into a specific slot.

    2. Am doing the same as yourself but connecting the laptop audio out to the integrated amp. Works great!

  12. Thanks for keeping this thread alive! I want to convert my ACS33 to run on 12 VDC power. I assume the D1, D2, D3 & D4 components rectify the transformer output. Any insights about the wisdom of simply pigtailing the 12 V leads into the circuit after the rectifying elements?

    1. I would not do so unless the transformer malfunctions, and, I happen to have a 12V DC power unit to play around with.

    2. In general I do not see the ROI justification for further improving the ACS33. It was never designed to be a high end active 2.1 speaker unit.

      The Klipse were such animals during the era of the ACS33.

  13. How to hack or modify Altec Lancing ACS33 2.1 speaker system to operate on 12 volt DC supply :

    Do Not perform any of the following unless you are trained in safety precautions for handling electrical circuits!
    Disconnect AC power cord from wall outlet. Wait 20 minutes for electric charges to drain from unit.
    NOTE: Dangerous voltages can still remain stored in components (especially capacitors) for several days / weeks.

    1).Remove bottom cover from Subwoofer (7 screws)
    Remove the 1 amp AC fuse from its holder on the small AC connection pcb
    (BHJ-2611 CC).

    2). Place a label on the AC Power cord stating not to plug in this cord because it is now disconnected inside and can only be operated on a 12 supply at this time.
    (or unsolder the AC power cord from that pcb and remove the AC cord completely).

    3). On the audio amplifier pcb BJH-2611 AA, solder a +12 volt fused supply wire to
    the cathode end (striped end) of diode 'D1' or 'D2'.
    Solder a negative supply return wire to the anode end (non-striped end) of diode 'D3' or 'D4'.

    Route the 12 volt supply wires through an appropriate hole you can make in the enclosure. Create a strain relief on the inside to protect the wires and connections from any kids pulling on the wires :-)

    We run our ACS33 on 12 volts in our motorhome to upgrade the TV audio.

    Sounds Great !

    Do the Best you can with what you have, and then Smile !


  14. I published a question about a 60HZ hum on my ASC33 system. It is not a hum but instead is a staccato. It stopped after 30 seconds but the bass does not work.

    1. My guess is a transistor needs to be replace. Best sent to a repair shop