Walter Woods Amps History and Development

[Uncletoad]

If the thread was "killed" during the modern incarnation of the TB software, a mod might be able to recover it. The original thread starter could be kept secret, and the posts by other members who contributed could be split from the thread and added to this one, or as a seperate thread that could be linked here. If anybody remembers the name of the original thread starter who deleted the thread, I'd be happy to take a look.

It was last year late or earlier this year I can't remember exactly. If you can recover anything, stuff it in here somewhere. The thread starter? If anyone remembers PM Chris.

 

[Ric Vice]

If the thread was "killed" during the modern incarnation of the TB software, a mod might be able to recover it. The original thread starter could be kept secret, and the posts by other members who contributed could be split from the thread and added to this one, or as a seperate thread that could be linked here. If anybody remembers the name of the original thread starter who deleted the thread, I'd be happy to take a look.

Chris, GRETA SCOTT FITZGERALD!
Do do that voodo that you do so well.

 

[Uncletoad]

Here is a pic stolen from ebay of a '94. MI somethingorother, just before he redesigned the line to what he's selling today. The current look of the Blue Light Electroacoustic line. This one from 2003 I think.

He says he's done with redesign as this one is selling like crazy and he can't keep up with making them.

Anybody have more pics? More info?

 

[Chris Fitzgerald]

Chris, GRETA SCOTT FITZGERALD!
Do do that voodo that you do so well.

Well, first you guys gotta tell me who started the original thread with all the info in it - there are like 6 WW threads that have been deleted by the original poster. Then, I'd need to check with the BG mods to see if it's okay, or if they want to do it themselves since it's not my forum. You guys zero in on who started the original thread, and we can go from there.

 

[pierce]

It was last year late or earlier this year I can't remember exactly. If you can recover anything, stuff it in here somewhere. The thread starter? If anyone remembers PM Chris.

if you can remember any unique details or id's of the original thread, google it. it might be cached in thier system.

 

[jotabass]

Hey, glad to have found you guys. I just bought from a friend an MI 800 which has been upped by walter to 400 watts, sounds amazing, just A/B tested it on stage at Pier 63 with a much more powerful GK head through a 10x4 box, just incredible the difference in sound.

Now back in Switzerland, would like to know what the specifics are about voltage and what to watch out for. would be typical and really too bad if i burned this thing up at today's gig...

will ask the stage people as well, but thanks for any feedback on this!

jonas

 

[Ric Vice]

Hey, glad to have found you guys. I just bought from a friend an MI 800 which has been upped by walter to 400 watts, sounds amazing, just A/B tested it on stage at Pier 63 with a much more powerful GK head through a 10x4 box, just incredible the difference in sound.

Now back in Switzerland, would like to know what the specifics are about voltage and what to watch out for. would be typical and really too bad if i burned this thing up at today's gig...

will ask the stage people as well, but thanks for any feedback on this!

jonas

Jonas,
According to my "manual" for the MI-100-8 the Power Requirements are "120/240 VAC switchable, 50-60 Hz ( stepdown transformer not required for european operation). Hopefully some of our techies will enter the thread and explain this feature. There is also a switch between the cooling fins on the rear of the amplifier that provides for 200- 240 50-60 hz operation volt operation. However I'd be really careful about using it.

Ric

 

[j-raj]

^that is a very sought-after feature to have on an amp (we use to, but not any more)... especially for the touring, sorry World Touring musician.

As for tech-info regarding a step-down transformer... Not sure how it does it, but I know what it does.

 

[brianrost]

Here's one I missed buying by a matter of minutes, a FOUR channel 600 watter from the 80s/90s.

 

[brianrost]

Here's a wild French WW clone called a Liegois, 100 watts

 

[brianrost]

An 80s/90s two channel 600 watter (amber light), notice the +/- EQ switches, channel selector, stereo preamp and phase switch! I own an MI-225 (green light, 350 watts) like this one. These older ones used to turn up for $1000 or so which made them good buys.

 

[brianrost]

A current High Power stereo model with the tell-tale red top

 

[Ric Vice]

Here's one I missed buying by a matter of minutes, a FOUR channel 600 watter from the 80s/90s.

Brian,
This is the one I mentioned earlier in this thread,
Some of these were originally built for guys who played those Four Channel Syndrums. Glad you found a pic of one their pretty rare.

Ric

 

[Ric Vice]

An 80s/90s two channel 600 watter (amber light), notice the +/- EQ switches, channel selector, stereo preamp and phase switch! I own an MI-225 (green light, 350 watts) like this one. These older ones used to turn up for $1000 or so which made them good buys.

Brian,
I have this exact amplifier. New they were $1,500.00 when I bought mine
in 1989. It's 600 watts into 4ohms, 400 into 8ohms. It also weighs @10lbs. Walter also built a 600 watt into 8 ohms with a blue light. I guess that would make it his first "Ultra High Power"

Ric

 

[interp]

I just recently acquired this MI 200-8 and would appreciate any input anyone can provide regarding its specific functions and history:
1. The "vari" knobs on the top channel/amp.
2. The crossover.
3. How to bridge it, of possible.
4. Anything else of interest.

Thanks to all in advance.

Kevin Kelly

P.S. This is just the front panel, I'd be glad to provide larger pics upon request.

 

[reedo35]

I just recently acquired this MI 200-8 and would appreciate any input anyone can provide regarding its specific functions and history:

Hey, I know that Amp! I got mine in 1991, it's nicknamed the "Sweeper"
1. The Vari knobs are like pre-EQ's for the bass, mid and treble allowing you to "fine tune" the level of cut and boost on each control.
2. Crossover is crossover,the diference is more audible with two cabs.Some of the more tech mined could probably help you more here.
3. Yes, you can bridge it, but I never saw a need to.
4. I said this before, I'll gladly say it again, I've used that Amp in over 17 different countries, in all types of power situations and conditions, and it is the ONLY piece of electronic equipment that's never let me down, ever. And for me, that's saying something.

 

[robgrow]

Technically speaking, the one feature that all of Walter's designs have had in common from the original "Mini Amp" (AKA The Ice Cream Sandwich) to the current Electracoustic models is the use of a lightweight switch mode power supply instead of linear power supplies with heavy iron-core or toroidal power transformer that are used in many other amps. That was pretty revolutionary stuff in musical instrument amps in 1970.

The earliest WW amps used conventional linear audio circuitry with all discrete transistor Class A preamps and Class AB power amps. The preamps are particularly interesting in that they were based on a Class A FET and bipolar transistor gain block, which helped give the early amps a nice warm tube-like sound. These preamps had relatively high distortion just like most vacuum tube based guitar amps have. Fortunately the distortion products are of the "good kind" that lend themselves to a warm, musical sound. Later models dropped the discrete transistor Class A preamp and instead use preamps designed around IC opamps (chips). (All the amps with "VARI" controls are IC opamp based I believe.) While IC opamps are used as a cost savings in many commercial products, Walter switched to them in order to design more sophisticated preamps with lower distortion.

Early WW amps with conventional linear Class AB power amp circuitry had relatively modest power capabilities even for the time. Walter has made several changes over the years in order to achieve higher audio output power. The current Electracoustic models use his proprietary Class D design.

 

[robgrow]

I believe the Vari Control simply tunes the center frequency of the individual EQ filters for the desired effect. This is sometimes called semi-parametric EQ or swept EQ, hence the sweeper nickname no doubt. The current Electracoustic models have Vari Controls for the midrange EQ on each channel (AKA "swept mids").

 

[Ric Vice]

I believe the Vari Control simply tunes the center frequency of the individual EQ filters for the desired effect. This is sometimes called semi-parametric EQ or swept EQ, hence the sweeper nickname no doubt. The current Electracoustic models have Vari Controls for the midrange EQ on each channel (AKA "swept mids").

Thanks to Uncletoad I can now post pictures of the two different versions of the Preamp that Walter used for the MI-100-8's

Walter's Original MI Preamp had several controls that he removed on later models. The picture below is of an early MI-100-8/ This amp had two "3 position expander switches for the bass and treble controls that cut or boosted their respective controls. There was also a Phase Switch, Channel Selector Switch, and "Stereo Switch" that would allow you to separate the preamp and use Channel 2 to drive a slave power amplifier.

If you follow this link
Invalid Link Removed
There is a picture of the second version of the MI series preamp.
This particular MI is a stereo version, with two DI's. When Walter redesigned the preamp he added boost and bright switches along with
a Vari control that was carried over to the Electroacoustic Series.

This amplifier was available in single channel and double channel versions
with a mono or stereo power amp.

Ric

 

[KUNGfuSHERIFF]

There was also a Phase Switch, Channel Selector Switch, and "Stereo Switch" that would allow you to separate the preamp and use Channel 2 to drive a slave power amplifier.

Really, now! I have an '86 MI-100-8 identical to the amp in your post, with the exception of the more common slot-type vents, and had no idea I could patch it that way. Thanks for the tip!
Here's another tidbit from Walter to us MI-amp owners: to get maximum volume from that model amp, set the master volume to 75% to 100% and use the input gain control to regulate overall volume (and clipping, obviously). High-gain active basses may need to be turned down a bit, and do NOT follow these directions with the Electracoustic amps or you'll kill them.
When I started running my amp as advised, it went from a loud, great-sounding amp prone to clipping to a friggin' cannon. It's so loud I can do controlled feedback six feet from the speakers (15" E-V and Ampeg 18", each at 8 ohms) but the downside is I tend to vibrate screws out of the chassis.