Double Bass Walter Woods Showdown! MI-225 8 vs Sweeper MI-400-8

[dylanjohnson]

I've got the unique opportunity to be checking out an old MI 225-8 and a 90's sweeper era MI 400-8 at the same time.
I've come to some conclusions but have some questions for you WW pros.

1. The volume between the two amps is oddly not that different. I'm getting just a hair more volume out of the 400-8. I'm surprised. I'm finding that I really need to crank the preamp gain on the sweeper to get in the ballpark of the "hi" input of the 225-8 (with the same master vol settings). I probably need to think more linear taper on these on the master (unlike the GK and Doubler I usually use). I am using a Juzek with a Full Circle.

2. The flat tone of the 225 is beautiful. Richer lows and nice detail on top. I played an electric gig the other day on it and loved it, but on DB I found that I got lost in the mix easier than when using the sweeper with a flat eq. I was surprised by that. I think I am used to the low mid forward voicing of the GK amps I've used for years and the sweeper is more in that ballpark when run flat.

3. Do you guys play these amps flat for the most part? I'm still trying to figure out how to deal with the parametric mids and the switches on the sweeper (what do these do on the sweeper? +0++ vs. -0+ on the 200, which is obvious). I really like the bass boost switch on the 225. Wish it was on the sweeper, too.

Do you all have any favorite EQ/settings tricks on these? Do you have the same low gain issues, or am I just not turning up the master enough?

Thanks!
Dylan Johnson

 

[KUNGfuSHERIFF]

Back when I used amps I had a similar volume issue and called Walter for his advice.

He said, specific to MI-series amps, to achieve maximum volume crank the master most or all the way up and use the input gain to set overall volume.

Do not do this to an Electracoustic amp, which is a completely different design. You’ll fry it.

 

[dylanjohnson]

Back when I used amps I had a similar volume issue and called Walter for his advice.

He said, specific to MI-series amps, to achieve maximum volume crank the master most or all the way up and use the input gain to set overall volume.

Do not do this to an Electracoustic amp, which is a completely different design. You’ll fry it.

Thank you. I think the sweeper is a different beast and maybe more like the Electracoustic (He changed the preamp from the old MI series). I'm going to try that on both anyway.

Edit- @KUNGfuSHERIFF AMPLE volume on both amps with that method.

 

[KUNGfuSHERIFF]

Neat, huh? Walter’s a clever boy.

 

[brianrost]

I had an MI-225-8 and sold it when I got my Electracoustic green light.

My MI-225-8 series had different voicing on the two channels. I have no idea what the single channel models were voiced like, but on mine one channel sounded better for DB and the other better for BG. On the Electracoustic, both channels are voiced the same and it's actually not as flattering to DB as the older amp.

I noticed zero difference in volume, but then I never had the amps running flat out.

to achieve maximum volume crank the master most or all the way up and use the input gain to set overall volume. Do not do this to an Electracoustic amp, which is a completely different design. You’ll fry it.

I know that Walter advises using the master to control the overall level, but I run it all the way up. Since there is no mute switch and no volume knob on the DB, setting the master anywhere other than full on means I have to remember where I set it. A lot of other amp makers suggest the same thing, SWR for example, and I ignored that advice, too. Almost 20 years later, my WW has yet to fry.

 

[dylanjohnson]

I had an MI-225-8 and sold it when I got my Electracoustic green light.

My MI-225-8 series had different voicing on the two channels. I have no idea what the single channel models were voiced like, but on mine one channel sounded better for DB and the other better for BG. On the Electracoustic, both channels are voiced the same and it's actually not as flattering to DB as the older amp.

I noticed zero difference in volume, but then I never had the amps running flat out.



I know that Walter advises using the master to control the overall level, but I run it all the way up. Since there is no mute switch and no volume knob on the DB, setting the master anywhere other than full on means I have to remember where I set it. A lot of other amp makers suggest the same thing, SWR for example, and I ignored that advice, too. Almost 20 years later, my WW has yet to fry.

Bob Gallien at GK advises the cranked master, too. I always thought that was to get the best signal to noise ratio and low signal distortion, but in Walter's manual from the early 90's he says the opposite. Interesting!

 

[DoubleMIDI]

With the master fully open you get the most amplification of any noise that enters the power amp. If the signal is low, the signal-to-noise-ratio is low, meaning a lot of noise with a rather quiet signal.

If the input gain is set as high as no overload of the input stage happens, even with an exceptionally loud playing, the master can be set lower, so the signal is as loud as with the fully open master and the lower gain, but noise is less amplified by the master.
But if the gain is set too high, the input wave gets deformed and the sound will be changed.
The problem is to find the gain setting that is high but not as high that some kind of harmonic or even inharmonic partials are generated by overload.

As stated in a different thread, the indicators that show overload or even signal presence might influence the input signal in some cases. They are very helpful if they work correctly without influencing the signal, but if they are badly designed or the amp has a little defect there it can drive players nuts.

With a fully open master and a low gain the distortion of the input signal will be minimal, but the noise level will be the highest. Maybe with modern amplifiers this is not a big problem. Just know the trade off in that case and in the case of a gain that is set too high so that distortion (maybe only when playing louder) happens.

 

[Povl Carstensen]

I have a WW MI 225-8 Sweeper, and recently I run the master at max. I hear no noise, and the sound seems "bigger" or more dynamic than if I run the input and the master straight up. This is comming from an ART tube preamp that gives quite a bit of gain.
I use channel 2 (the lower channel), which I understand is designed for acoustic bass. It gives a more clear, hi-fi'y sound than channel 1.

 

[dylanjohnson]

@DoubleMIDI Thank you, that makes perfect sense! @Povl Carstensen I've read some of your posts here, as you seem to be one of the few members with a sweeper era WW. Do you also find that the preamp gain is a little weak? I'm assuming if you are using an ART tube pre in front of it, you aren't too happy with the preamp section on it? I can't notice a difference in the channels in this MI-400, but definitely notice a difference in the MI 225 channels. Maybe yours was made before he switched to the same eq points on both channels as with his later amps.

 

[Low Class]

I've owned just about every WW model(including his not well known 2200 watt model). Not sure about the 90's MI-400, but the MI-200-8 was the only amp platform used according to Walter's brochure that I still have from that early 90's era. It is 200 watts at 8 ohms per side, 350 at 4 ohms per side, 700 watts @ 8 ohms bridged, and there was the 4 ohm bridged option that was 1000 watt @ 4 ohms. He may have(and probably did) build other amps not on his brochure. When I ordered my MI-200-8 with the 4 ohm bridged option(the first of 2 I bought from Walter) I asked Walter about the Sweeper and he recommended the Stereo 2 channel model because he said it sounded better. After later in life playing through a Sweeper I agree. I thought it sounded weaker than his standard preamp. Something to consider in your comparison. All my WW amps pre Electracoustic were used with the Master wide open.

 

[Ric Vice]

As I recall, Walter didn't built the "Sweeper" for very long. It's hard to say because only Walter knows. I've owned three Woods amplifiers, a MI-100-8, the MI-400-8, and still own a Electroacoustic Ultra. He was still building

MI's 1991 when I got my MI-400-8, and started the Electroacoustic series by 1997. He had difficuilty sourcing the components to built higher powered amps for a few years.

 

[dylanjohnson]

Thanks for getting back, guys. This one has the usual hand written "4"s for the 400 designation, so it's basically a 200 with an amber light. After doing some A/B tests with different cabs, I think the MI 225 is the one I prefer by a longshot. Unfortunately, it's being sold for way more than I can afford (1900), and I am aware that Walter will not repair this amp if the power section goes down. I guess it might be worth contacting the place in Berlin and asking about the repair cost for that if they actually can repair these. Maybe the seller will take a reasonable offer on it.

I've owned just about every WW model(including his not well known 2200 watt model). Not sure about the 90's MI-400, but the MI-200-8 was the only amp platform used according to Walter's brochure that I still have from that early 90's era. It is 200 watts at 8 ohms per side, 350 at 4 ohms per side, 700 watts @ 8 ohms bridged, and there was the 4 ohm bridged option that was 1000 watt @ 4 ohms. He may have(and probably did) build other amps not on his brochure. When I ordered my MI-200-8 with the 4 ohm bridged option(the first of 2 I bought from Walter) I asked Walter about the Sweeper and he recommended the Stereo 2 channel model because he said it sounded better. After later in life playing through a Sweeper I agree. I thought it sounded weaker than his standard preamp. Something to consider in your comparison. All my WW amps pre Electracoustic were used with the Master wide open.

 

[Ric Vice]

Thanks for getting back, guys. This one has the usual hand written "4"s for the 400 designation, so it's basically a 200 with an amber light. After doing some A/B tests with different cabs, I think the MI 225 is the one I prefer by a longshot. Unfortunately, it's being sold for way more than I can afford (1900), and I am aware that Walter will not repair this amp if the power section goes down. I guess it might be worth contacting the place in Berlin and asking about the repair cost for that if they actually can repair these. Maybe the seller will take a reasonable offer on it.

Thanks for

Dylan,
My guess is that Walter had lots of bottom chassis plates left over with the MI-100-8's that he had made up ahead of time. Having the amp repaired in Berlin could be quite expensive by time you ship the amp to Germany, through customs and pay their service charge

and ship it back. It's hard to know. Walter's issue with repairs, is that he can no longer source the components to repair his older amps with, so unless Audio Berlin has some magic stash of parts, they may not be able to repair them either.

 

[Povl Carstensen]

@DoubleMIDI Thank you, that makes perfect sense! @Povl Carstensen I've read some of your posts here, as you seem to be one of the few members with a sweeper era WW. Do you also find that the preamp gain is a little weak? I'm assuming if you are using an ART tube pre in front of it, you aren't too happy with the preamp section on it? I can't notice a difference in the channels in this MI-400, but definitely notice a difference in the MI 225 channels. Maybe yours was made before he switched to the same eq points on both channels as with his later amps.

I do not find it weak as such. The reason I use the ART Tube MP Project Series is that I use a Countryman condenser mic that requires phantom power. But then again, I can not compare with other WW amps.
The Sweeper eq section is a bit enigmatic. Even with the levels in neutral, changing the center frequencies changes the sound somewhat. I have ended using the bass control at the lowest frequency setting and the treble at the highest. I hardly touch the treble, the bass is a bit like a variable "rumble filter", and then I can use the mid to either add a bit of low mids, or take out some scratchy high mids, depending on the room etc.
While we're at it: My amp has two power amps, which can be used for two speakers (also with stereo effects), or even with a build in variable crossover, to power a "top" and "bottom" cabinet. I have no use for these possibilities. So actually the more powerfull mono output version I saw on the list from the German site would have been perfect for me. Which brings me to the possbility of bridging. I have not gone into it, because it seems a bit of a hazzle and perhaps slightly hazardous. Lately I came to think about whether the right guy could make a single speaker cable with two jacks for the amp, that took care of the whole bridging part. Anyone with experiences in that?

 

[dylanjohnson]

I do not find it weak as such. The reason I use the ART Tube MP Project Series is that I use a Countryman condenser mic that requires phantom power. But then again, I can not compare with other WW amps.
The Sweeper eq section is a bit enigmatic. Even with the levels in neutral, changing the center frequencies changes the sound somewhat. I have ended using the bass control at the lowest frequency setting and the treble at the highest. I hardly touch the treble, the bass is a bit like a variable "rumble filter", and then I can use the mid to either add a bit of low mids, or take out some scratchy high mids, depending on the room etc.
While we're at it: My amp has two power amps, which can be used for two speakers (also with stereo effects), or even with a build in variable crossover, to power a "top" and "bottom" cabinet. I have no use for these possibilities. So actually the more powerfull mono output version I saw on the list from the German site would have been perfect for me. Which brings me to the possbility of bridging. I have not gone into it, because it seems a bit of a hazzle and perhaps slightly hazardous. Lately I came to think about whether the right guy could make a single speaker cable with two jacks for the amp, that took care of the whole bridging part. Anyone with experiences in that?

I don't have experience with that, but I will let you know that if you like the sweeper model, the mono amp I bought from Bass Exchange/Amp Shop will be available again soon as I decided it didn't work for me. I have never seen one with an amber light (400 @ 8 ohms) around in the research I've done, and the price is quite right. I think it is still on reverb.com and I assume they will re-list it on Ebay. I'm not sure if that one can be bridged, though.

 

[Povl Carstensen]

I don't have experience with that, but I will let you know that if you like the sweeper model, the mono amp I bought from Bass Exchange/Amp Shop will be available again soon as I decided it didn't work for me. I have never seen one with an amber light (400 @ 8 ohms) around in the research I've done, and the price is quite right. I think it is still on reverb.com and I assume they will re-list it on Ebay. I'm not sure if that one can be bridged, though.

Yes, well I am happy with my amp, and for the time being it actually gives me enough power. It is amazing that it is 20-something years old, and you can not actually see it. Great build quality. But thanks!

 

[Ric Vice]

I don't have experience with that, but I will let you know that if you like the sweeper model, the mono amp I bought from Bass Exchange/Amp Shop will be available again soon as I decided it didn't work for me. I have never seen one with an amber light (400 @ 8 ohms) around in the research I've done, and the price is quite right. I think it is still on reverb.com and I assume they will re-list it on Ebay. I'm not sure if that one can be bridged, though.

Over the years, just when I thought I'd seen every different Walter Woods Amp, a new one will surface. Walter designed and built all of them and a few appear to be one off's . I think you made a wise decision. I sold one of mine because

I wanted to have something that wasn't dependent on Walter's avalibility and pricing to repair. I still have my Electroacoustic Ultra, so one is more than adequate.

By most accounts, Walter's amplifiers are incredibly reliable, and if taken care of
provide a high quality Double Bass amp that havs great longevity. Just my take.

 

[barneybass]

I believe this is a 225? It had an early version of Walters class d. I bought it via eBay ten yrs ago with a scratchy output. It arrived missing output transistors.......
I’ve owned and sold a ultra blue light but always preferred the sound of the older preamp. I have a friend who’s an electronics engineer and bass player . He worked out that the timing circuit in the class d was locking up but as Walter scratches the identifiers off the top of components it was deemed not worth the hassle. I thought I was buying an older class AB power amp woods.

So I gutted the woods power amp. And installed a hypex ucd 400 and a cold power psu. It was underpowered and the psu injected hum into one of the preamp channels.

So it sat on a shelf for a while.....
I use hypex amps in my mastering studio, 700ucd mono blocks.
Then i saw a new module

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1000w bridged and it was the perfect size for the woods. My friend built me a small breakout pcb with an opamp to interface with the hypex.

Early days yet but it’s been working well

I’ll post some pics in the amps forum when I’ve had more time with it.

 

[Ric Vice]

I always hoped that some very savvy technical whiz would find a way to use a Hypex with one of Walter’s preamps, congratulations. By all accounts Hypex power amps are some of the best units on the market. Jule Monique uses them in his M series power amplifiers and NAD uses them in their new 3020D.

 

[barneybass]

When I get a chance I’ll post an inside pic