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Demeter/Stewart/Acme questions/concerns

Discussion in 'Amps and Cabs [BG]' started by Chace90, Nov 7, 2005.

  1. Chace90

    Chace90 Supporting Member

    Feb 1, 2002
    Denver, CO
    Ok, so I posted a long while ago about about my Demeter VTBP-201S / Stewart 1.6 (bridged, driving an Acme B-4) clipping and eventually shutting off during prolonged and heavy use. I'm still experiencing the same problem. So far I've tried:

    1. turning down the midrage/tweeter controls on the back of the Acme

    2. plugging the amp directly into an outlet instead of my rackrider power conditioner, thus eliminating a potential bottleneck of current

    3. using the mic balanced DI out into the balanced input of the Stewart

    None of which have fixed the problem.

    First off, my Demeter's active and passive inputs are sending the same level. According to the demeter manual, when there are basses plugged into both preamps the inputs should balance to equal levels. However, when I have only one bass plugged into either input, the level is the same. The preamp previously sent a hotter signal from the passive input (obviously). I have no idea what's causing this and I have done nothing to alleviate this problem. My pre also has a scratchy voclume knob around 9 - 10 o'clock. This is also something I have done nothing to fix. The tubes are original.

    So, I unplugged the cabinet from the poweramp and decided to send a fairly hot signal to the poweramp. I was under the impression that because the Acme's are so inefficient, my cabinet was demanding more power that the Stewart could push, therefore causing it to clip and shut down (as part of the protection circuitry). However, without the cabinent plugged in, I can easily cause the poweramp to clip. And this is with the internal volume trimmer on the Demeter set to about 9 or 10 o'clock. In the 10 minutes I spent driving the poweramp unplugged, it clipped frequently but never shut off. Due to my "research," I'm starting to think that the problem more likely lies in the either poweramp or preamp.

    Does anyone have any ideas as to what the problem could be? I'm getting desperate. I'm very inclined to replace my cab with a Schroeder of some sort, but financial constraints hold me back from doing so. I don't want to spend the money for a new cab if my pre/poweramp combo will still clip.

    Here's a link to my original thread concerning this topic:

  2. jokerjkny


    Jan 19, 2002
    NY / NJ / PHL

    as all acme cabs, you need to jack up the mids. many cabs that we know and love all are "voiced" in the mids in some way or other, while acme cabs are of the most neutral cabs on the market.

    SO, crank the mids knob on your Demeter. mids are what help you hear your bass better in all situations. a parametric EQ helps tremendously, but you can also try cutting back a tad on the lows, to allow the mids to become more apparent, while also cutting back some of the trebles to give the impression of more bass. all of this so that way you can push more apparent volume.

    conversely, if you're cranking the bass knob on your bass' onboard preamp or the demeter preamp itself, you're gonna push the cab into clipping faster.

    also, keep the tweeter and midrange driver set to wide open, i.e. 0 dB. they help you hear yourself better in all situations.

    also, there's a possibility that you might have blown one side of the Stewart, thus not pushing enough power, thus making it clip like crazy, and thus, causing the power amp to shutdown after intense use while damaged. happened to me w/ my Stewart 1.2.

    hope this helps.
  3. Someone please correct me if I'm wrong, but does each side of the power amp see 2ohms when the amp is bridged into a 4 ohm load? And, if so, wouldn't that be a problem for the notoriously warm running stewart?

    Furthermore, we have discussed high pass filters and their application with Acme cabs to cut down on the sub-bass freqs, significantly increasing power handling of the cabs and reducing powersupply demand.

    I use 'em always.
  4. Chace90

    Chace90 Supporting Member

    Feb 1, 2002
    Denver, CO
    When running the poweramp in bridged mono, is it natural for the left side's -20dB light flashes earlier than the right side's light?
  5. Chace90

    Chace90 Supporting Member

    Feb 1, 2002
    Denver, CO
    anyone else got some ideas?
  6. tombowlus

    tombowlus If it sounds good, it is good Gold Supporting Member

    Apr 3, 2003
    Fremont, Ohio
    Editor-in-Chief, Bass Gear Magazine
    I have had problems driving two Low B-2's with a Stewart World 2.1. The cabs sounded like a speaker had blown, and were distorting like crazy (despite the fact that it was loud, but not stupidly so). Then I noticed the clip lights flashing on the Stewart (and again, normally this rig should go much louder). My suspicion is that I wasn't seeing optimal voltage through the AC line, and the rails of the switching mode power supply were exhausting themselves.