DI'ing a Walter Woods MI225-8 amp?

Discussion in 'Amps, Mics & Pickups [DB]' started by simoneves, Mar 13, 2014.

  1. simoneves


    Mar 13, 2014
    Dear TalkBass,

    I'm a sound engineer preparing for a show, and the bass-player-to-be says he has had problems in the past having his Walter Woods MI225-8 amp DI'd, resulting in buzzes.

    The amp appears to have a 1/4" (presumably unbalanced) line-out for each channel. If these aren't actively driven, and are just a loop-through of the inputs, then I could see why perhaps a Passive DI might affect the audio, but even then I don't see what would create a buzz (presumably some kind of ground loop problem) unless the amp and/or the DI's that others have tried to use are faulty in some way.

    I have a decent dual Active DI which surely would work on the line-outs, or even between the instruments and the amp (they will be using both electric and upright bass), although obviously the latter wouldn't capture the tone of the amp.

    I am wondering if anyone here knows of any issues or tips with these amps, please. I don't have a huge variety of "tools in my toolbox" (either physical or mental!) so I'd like to know in advance what I might need to make it work.


    Simon Eves
    Novato Theater Company
    Novato, CA, USA
  2. Ed Fuqua

    Ed Fuqua

    Dec 13, 1999
    Chuck Sher publishes my book, WALKING BASSICS:The Fundamentals of Jazz Bass Playing.
    What's the group, what kind of music? If I were on the gig and was going to use the Woods, I'd just put my mic up through the bridge feet to get the bass out into the house.
    I've only used my line out twice, no problems either time. Once in a large church, the sound guy there said it was the warmest sounding line out he'd heard. The other was at the Pace University Performing Arts Center. Both were with a piano trio backing a vocalist, so not a loud band...
  3. simoneves


    Mar 13, 2014
    It's musical theatre (Next To Normal), so a mixture of music styles, some gentle acoustic, some rock.

    Mic-ing the bass itself would be fine, although I don't really have a suitable mic spare (nor one really suitable for mic-ing the cab), and remember there is an electric bass too (same player swapping), so the DI needs to work for both (ideally separately, but presumably the two channels of the WW are combined before the power amp stage, right?)

    I'm going to try the dual Active DI, but if he's had problems on multiple gigs (but only some) in the past (different venues, different sound guys) then I guess it's entirely possible that the WW has an intermittent fault. Either that, or all those sound guys were just incompetent. I'm hoping not to join that list.
  4. adbass

    adbass Supporting Member

    Sep 14, 2012
    Is Walter still operating out of Palm Desert, California? A quick google search brings up his phone number.

    You may want to check in with the builder himself, but be warned: he may not be thrilled by do-it-yourself repairs on one of his amplifiers. On the other hand, he may very well be receptive to servicing the amp himself.
  5. Run the DI in line before the input. I use to run each of the three WW amps I've owned that way live and in the studio. No buzz problems, unless the venue had dirty power. My DI is a Countryman, incidentally.
  6. B String

    B String Supporting Member

    Apr 11, 2002
    Los Angeles
    I agree with this approach. Plus, the Countryman is a great DI for piezo pickups having a 10 meg ohm input. Works very well for passive electric basses too.
    You want to get the bass before it goes through all the eq.
  7. simoneves


    Mar 13, 2014
  8. A. Munk

    A. Munk Supporting Member

    May 11, 2005
    san francisco bay area
    It's funny with the WW's.
    Some sound guys/venues have problems with them, some don't.

    My WW's was stolen a few years back so it's been a while, but I seem to recall it was a line/mic level issue?
  9. That's why I always carried everything I needed in the little pistol case the amp traveled in. All the soundman had to do was hand me a line to plug into the balanced out of the DI.

    I don't know enough about electronics to be versed in level issues, but Walter told me he only built balanced line outs into a handful of his amps precisely because of noise issues.
  10. Ric Vice

    Ric Vice Supporting Member

    Jul 2, 2005
    Olivette, Missouri
    If you're running the DI in front of the amp, the input impedance for the box needs to be at least 1 Meg Ohm. I can't find that listed in the spec sheet, so you'll just have to experiment. I always use the Countryman 85S, but there are other boxes that have a 1 Meg or even variable input impedance. I always run the DI from the line out on the Woods so that isn't an issue' because the Woods has a 1 Meg input impedance.

  11. shwashwa


    Aug 30, 2003
    ive used my 1/4 di out on my woods many times. no problems. there's a separate volume control for it. you might want to check it out. also, we took the 1/4 inch out and then put it into an actual DI box before sending it to the board, no problems
  12. Ed Fuqua

    Ed Fuqua

    Dec 13, 1999
    Chuck Sher publishes my book, WALKING BASSICS:The Fundamentals of Jazz Bass Playing.
    Having a live mic in the pit is probably not the best idea...
  13. simoneves


    Mar 13, 2014
    The Audiopile one is also 1 MOhm. The specs are listed at the bottom of that web-page on the left. Hopefully it'll be fine. I've used it with electric guitars and basses before, but only into more modern amps.

    Agreed. Unfortunately, I don't have any choice with the violin or drums.
  14. Ric Vice

    Ric Vice Supporting Member

    Jul 2, 2005
    Olivette, Missouri
    Great! I just missed that when I read over the specs. You can try the DI, either ahead of the amp, or tapping the line out. Be advised (sorry, I couldn't resist) that your bassist may prefer having the DI attached to the line out. Running the DI ahead of the amp changes the timbre of the instrument for some reason, at least that's what I've experienced.

  15. Yes, usually the sound will be changed because you have a parallel impedance load of the DI box and the amp. Since most amps have 1 MegOhms input impedance putting a second 1 MegOhms DI box impedance in parallel results in a total impedance load of 500 KOhms for the piezo.

    A 10 MegOhms DI box impedance doesn't change the 1 MegOhms load as much, so this would hardly be noticable. (It might when used in front of a 10 MegOhms Fishman or HPFpre preamp with a BP100 pickup since this is basically the same situation as before on the 10 MegOhms level.)

    If you use a preamp/impedance buffer, then put the DI box behind the preamp and you won't have any impedance problems.

    A line out works too, but then you might fight with the soundman when you change your amp sound.

    If it buzzes use the ground lift switch on the DI box. And check with the soundman if he wants/needs line level or mic level XLR signals and what you can deliver.
  16. simoneves


    Mar 13, 2014
    That's an interesting point. Is it even possible to make a DI box which wouldn't affect the sound when placed in parallel with such a high-impedance pre-amp input? :)

    Maybe it's time for me to get an 85S after all...
  17. brianrost

    brianrost Gold Supporting Member

    Apr 26, 2000
    Boston, Taxachusetts
    Never had an issue with DIing either one of my WWs. I've even used an inline 1/4" to XLR transformer with good results.

    Walter himself recommends only using passive DIs on the line outs...not sure why. He's not an overly talkative guy, eh?
  18. Maybe because the line outs deliver enough current to drive a passive DI box without any kind of distortion and any active electronics adds some noise (even if it is only a very little bit in some cases).
  19. simoneves


    Mar 13, 2014
    Interesting. Well, I may have to throw a few more DIs in the car anyway (as I just found out the drummer is going to be using a synth pad for some extra percussion).
  20. Ric Vice

    Ric Vice Supporting Member

    Jul 2, 2005
    Olivette, Missouri
    On the occasions that I've had to DI the either of my Walter Woods heads, I observed that the Countryman 85s sounds the best running from the line out's on the Woods.


    I always surmised that it was because it used a FET in the circuit and had a 10 Meg Ohm input impedance. I hadn't considered that an active DI would boost the noise along with the signal, but it really makes sense.