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How to bridge channels?

Discussion in 'Amps, Mics & Pickups [DB]' started by Tbeers, Aug 29, 2005.


  1. Tbeers

    Tbeers

    Mar 27, 2005
    Chicago, IL
    I've heard talk of bridging the 2 channels on a Walter Woods to increase the power. I'm about to receive a MI 100. Is there some easy way to do this "bridging"?
     
  2. Freddels

    Freddels Musical Anarchist

    Apr 7, 2005
    Sutton, MA
    Not sure if you can do this with the WW but others will chime in I'm sure. Is the MI-100 that you're getting a two channel model?
     
  3. flatback

    flatback

    May 6, 2004
    Bolinas Ca
    10 years ago Walter told me to bridge the 2 channels of my M100 with a standard Y cable. I have been using this set up lately and it does give you a lot more gain. You have to deal with 2 preamps though. I would like to know if you really get 2x the watts or what. Or if there is a better way of doing it.Also if you reverse the phase you get nothing( complete phase cancelation)...or at least I do.
     
  4. Tbeers

    Tbeers

    Mar 27, 2005
    Chicago, IL
    A Y cable... nice, that sounds simple enough. Yes, the one I'm getting has 2 channels. And XLR-out, which makes me happy.
     
  5. robgrow

    robgrow Supporting Member

    May 1, 2004
    Cincinnati, Ohio
    I wonder if I'm missing something here? I don't think you can "bridge" a WW MI100 in the same sense that you can bridge a stereo power amp for mono operation at higher power. Using both preamp channels on the WW amp may give you more gain and possibly more tonal possibilities, but it doesn't give you any more power.
     
  6. Tbeers

    Tbeers

    Mar 27, 2005
    Chicago, IL
    Hmm, maybe I have been misinformed....
     
  7. flatback

    flatback

    May 6, 2004
    Bolinas Ca
    hmmm...dunno...My M100 has a stereo switch...does that add to my confusion or make it clearer? It sounds louder but does it have any more juice?
     
  8. Sam Sherry

    Sam Sherry Inadvertent Microtonalist Supporting Member

    Sep 26, 2001
    Portland, ME
    Euphonic Audio "Player"
    As Rob notes above: Your MI-100 has a stereo preamp and a mono power amp. It is possible to use both preamps in parallel, not in series. There's a built-in channel switch which lets you use either or both preamp channels from a single input.

    Possible uses of multiple channels include setting one channel for bowing and another for pizz or setting one channel at a "solo" volume. Of course, you can use the two channels for different sound sources -- say, piezo and mic mixed together, or EB and DB (not mixed together).

    On the MI-100 using these switches in performance tends to be inelegant because they're hand-operated. You have to stop playing, turn around and flip the switch (and not hit anything else). I suppose you could set the two channels to emphasize different EQ settings and bridge to use both. I don't because I have always set my EQ dead flat.

    Mono power amp means that there's nothing to "bridge" to. If you have a newer model with a stereo power amp, I bet there's a switch to bridge the channels for additional power.

    Play on. Get practicing, you!
     
  9. Walter, at one time, made a variety of mono and stereo amps, both single preamp channel and two channel. I believe he is down to one stereo amp (i.e., two power amps) model now, and all his amps now have identical two channel preamps.

    There are very clear directions on bridging his 'stereo' amps in the manual. When bridging, remember that each side of the amp sees 1/2 the ohmage of the total bridged load.... so, in most cases, for example, if each side has 4ohms as its lowest safe operating ohmage, then the minimum safe bridged ohmage is 8ohms.... running bridged into a lower ohmage load can lead to serious trouble!
     
  10. Ric Vice

    Ric Vice Supporting Member

    Jul 2, 2005
    Olivette, Missouri
    First off, I'm not a technician or an electronics expert, that said
    I have some questions about using the amp this way. When Walter
    originally built the MI 100's he could only supply either a 100 or 225 watt model of the power amp. At that time, he also offered a
    slave power amp, that when attached to the pre output of Channel 2 (I think, correct me if I'm wrong) allowed you to actually run the amp in "true stereo" that was at least his orignal intent.
    Walter then informs Flatback that you can run an input into both channels simultaneiously and get an incremental increase in out put by doing this. Is this correct?
    My concern here is the amp power supply may be working twice as hard in this mode as it does in it's "normal" single channel operation. Can one of you shed some light on this?

    Ric

    PS Hopefully I'm wrong about this.
     
  11. flatback

    flatback

    May 6, 2004
    Bolinas Ca
    BOy I thought I didn't have a handle on it before. And so I dial Walters # to get the real scoop and I get the age old "I'm not answering my phone until after labor day so call back then" I'd really like to know difinitively (thanks Sam I do believe you) Just because I DO remember Walter telling me to bridge to get more juice and I seem to remember him saying that the channels had seperate power sources...but with all the other holes in my memory...(good thing all those standards are still in there...)
     
  12. Ric Vice

    Ric Vice Supporting Member

    Jul 2, 2005
    Olivette, Missouri
    Believe it or not, I found a pictures of the Walter Woods Electro Acoustic Hi Power in both the Mono and Stereo versions, and just as Sam surmised there is an extra switch right next to the pilot light.

    Ric
     
  13. flatback

    flatback

    May 6, 2004
    Bolinas Ca
    so what is the stereo switch on my m100 for?Are you saying that it was meant to be used with a slave only?I thought this amp could drive two cabs in stereo (i never tried it though) never got a manual, but Walter hooked me up with the amp used(10 years ago) and kind of gave me the manual over the phone
     
  14. Tbeers

    Tbeers

    Mar 27, 2005
    Chicago, IL
    I guess I'll try and figure out what the deal is when my amp arrives. Even without bridging I suspect I'll be fine in terms of power.
     
  15. Ric Vice

    Ric Vice Supporting Member

    Jul 2, 2005
    Olivette, Missouri
    Well, only Walter knows for sure. but according to the little instruction paper (mini manual) that comes with my MI 100 8 that's precisley what it does. The preamp can be switched into the stereo mode. but since the power amp is mono you would need a slave to run stereo to two cabinets. That's one of the uses for the
    line in/ line out jacks on the front pannel.

    Ric

    PS: unless your amp is a stereo unit and I know he made some
    He actually built a some MI series quad preamps amps for electronic drums. I don't know what the power amp was on those models.
     
  16. flatback

    flatback

    May 6, 2004
    Bolinas Ca
    Thanks you'se guys. It's all so clear now (although underpowered)
    I have to say though, on a small jazz gig the M100 still sounds great.
     
  17. Ric Vice

    Ric Vice Supporting Member

    Jul 2, 2005
    Olivette, Missouri
    Hey, when I bought mine in the late 70's I pased on the MI 225
    because it was more expensive than the MI 100. I agree with you,
    the MI 100 is a great little amp. If I was buying my first amp today I'd probably go with the new Clarus. I don't think that Walter even builds the 100 watt versions of the new Electro Acoustic's anymore.

    Ric
     
  18. Tbeers

    Tbeers

    Mar 27, 2005
    Chicago, IL
    Well my amp arrived in basically mint condition with the original instructions and everything. It's wonderful....

    I think I'm fine for power. My cabinet is 4ohm anyway.