4ohms on a bridged walter woods MI 200-8?

[eulenspiegel]

Hi, I´m new in this and want to try my luck with the following question:
I´ve just got a walter woods MI 200-8 with stereo pre and poweramp. A general advertisment sheet that came with if sais it has 700Wrms to 8ohms. Then two copied sheets that give instruktions there it sais to bridge the amp with the special cabel includet (I have the cable) to a minimum of 4ohms. This is not a thing I just wanna try, so maybe there is someone out there who can give me some advice.
Thank you!

[KJung]

The safest thing to do is just give Walter a call. PM me if you need his number.

Since Walter makes a big point about his amps requiring a minimum of 4ohms, I would think that bridging into 4ohms would be a big no-no, since you would, in effect, be running each side at 2ohms.

So, the safe answer is do not bridge into less than an 8ohm load. I'm virtually sure of this, but I would call Walter to make sure.

[eulenspiegel]

thanks, I kind of thought so. You have a number I can call to make shure?

[KJung]

Originally Posted by eulenspiegel

thanks, I kind of thought so. You have a number I can call to make shure?

PM on the way.

Ken

[Ric Vice]

Originally Posted by eulenspiegel

Hi, I´m new in this and want to try my luck with the following question:
I´ve just got a walter woods MI 200-8 with stereo pre and poweramp. A general advertisment sheet that came with if sais it has 700Wrms to 8ohms. Then two copied sheets that give instruktions there it sais to bridge the amp with the special cabel includet (I have the cable) to a minimum of 4ohms. This is not a thing I just wanna try, so maybe there is someone out there who can give me some advice.
Thank you!

In Walter Woods nomenclature MI-200-8 would indicate a
200 watt amplifier. Evidently, it means something else
with his stereo amp's?

Ric

[interp]

I also have a WW MI 200-8, made in 1991 (see pic), that I acquired a few months ago. I do not have a bridging cable and am very curious whether yours is designed as a Y-cable connecting the two speaker outputs on the back, with the end of the cable going to a single 8-ohm (or 4-ohm) load.

My unit specifically states the rated power as 225 watts per channel into 8 ohms, with no indication of the wattage per channel into 4 ohms, although I imagine it would be around 350. However, on the bottom near the speaker outputs there is a sign that says:

CHAN. 1/TOP, CHAN.2/BOT.
8 OHM MIN. BRIDGED
4 OHM MIN./CH

This seems to imply that one should not run the amp bridged into a 4 ohm load. If so, the only option for me to use my two 8-ohm CXL 112's is one each per channel, in stereo. I would like to be able to run them together as a 4-ohm load off the bridge cable, but am not about to experiment without more information.
As far as I know the MI 225-8 model can be bridged into either a 8- or 4-ohm load, although I may be mistaken.

I have called Walter about the cable issue and about how to properly bridge this amp, but just get his answering machine. I live in Germany, so he's not likely to return my call. I guess I will write him with my questions.

In the meantime, can you give me any information about how the bridge cable is built or where one can be acquired, whether your amp has a B/S (bridged/stereo?) toggle switch, or anything else you may have learned from the instruction sheet (I don't have one)?

Thanks in advance for any assistance and good luck with this wonderful amp!

Kevin

[Reefer]

The MI-200 was not built to handle a 4 ohm load in bridge mode. There was a $400 option that was available so the amp could go to 4 ohms bridged, but there are not too many of those out there. The bottom panel would indicate if the amp could go to 4 ohms. Don't rely on the instruction copies.

The bridging cord is easy to fabricate. All you need is one speaker cord with a 1/4" male connector on one end and an additional 1/4" male connector. Remove the ground or negative wire from the connector and solder the negative wire to the positive pin on the additional connector. So what you will end with is a speaker cord that has a connector on one end to go the cab and on the other end will be 2 1/4" jacks with the positive lead soldered to the positive pin on one and the negative lead soldered to the positive pin on the other. There is nothing soldered to the ground on either jack. I hope this makes sense.

To use the bridging cord plug the end with the 2 jacks into each of the speaker outs on the back of the amp. Put the bridge/stereo switch in the bridge position and put the pan controls in the 12 o'clock postion. That's it!

[robgrow]

Originally Posted by Reefer

The MI-200 was not built to handle a 4 ohm load in bridge mode. There was a $400 option that was available so the amp could go to 4 ohms bridged, but there are not too many of those out there. The bottom panel would indicate if the amp could go to 4 ohms. Don't rely on the instruction copies.

The bridging cord is easy to fabricate. All you need is one speaker cord with a 1/4" male connector on one end and an additional 1/4" male connector. Remove the ground or negative wire from the connector and solder the negative wire to the positive pin on the additional connector. So what you will end with is a speaker cord that has a connector on one end to go the cab and on the other end will be 2 1/4" jacks with the positive lead soldered to the positive pin on one and the negative lead soldered to the positive pin on the other. There is nothing soldered to the ground on either jack. I hope this makes sense.

To use the bridging cord plug the end with the 2 jacks into each of the speaker outs on the back of the amp. Put the bridge/stereo switch in the bridge position and put the pan controls in the 12 o'clock postion. That's it!

Some very good advice. When bridging any 2-channel (stereo) amp, it's important that the minimum load impedance be twice what it would be for normal (un-bridged) operation unless the manufacturer specifically states otherwise. Also it's important to remember that, when running in bridged mode, the sleeve connection will be above ground on the 1/4-inch phone plug on the speaker cabinet end, and the phone plug's shell must not be allowed to touch anything grounded to prevent shorting the output of one of the channels. This would be a good place to use a Speakon connector if your speaker cabinet is compatible, since the Speakon has no exposed contacts.

[Reefer]

Originally Posted by robgrow

Some very good advice. When bridging any 2-channel (stereo) amp, it's important that the minimum load impedance be twice what it would be for normal (un-bridged) operation unless the manufacturer specifically states otherwise. Also it's important to remember that, when running in bridged mode, the sleeve connection will be above ground on the 1/4-inch phone plug on the speaker cabinet end, and the phone plug's shell must not be allowed to touch anything grounded to prevent shorting the output of one of the channels. This would be a good place to use a Speakon connector if your speaker cabinet is compatible, since the Speakon has no exposed contacts.

Thanks, I forgot to mention to use connectors with plastic caps or wrap them with electrical tape or shrink wrap to avoid problems.

[eulenspiegel]

hi, I wasn´t online for a while and I´m still not shure how all of this works. it looks like I have the same amp as shown. I think we can switch to German since I live close to Köln. Können wir telephonieren? Ich bin eigentlich so klug wie zuvor. Meine Nummer: 02173-250316 Till Brandt

[landru64]

i talked to walter last week and again today (to refresh my memory) about the difference between my 'electroacoustic' stereo green light amp and my friend's MI200-8 stereo amp, which looks just like the one pictured. he said the only difference load-handling wise is you have to have 8ohms while bridged on the older one. but you can do 4ohms per side unbridged. so you can run two 4 ohm cabs stereo and get the 350ish watts per side. the 'current' electroacoustic amp can be bridged into 4 ohms.

[Reefer]

Originally Posted by landru64

i talked to walter last week and again today (to refresh my memory) about the difference between my 'electroacoustic' stereo green light amp and my friend's MI200-8 stereo amp, which looks just like the one pictured. he said the only difference load-handling wise is you have to have 8ohms while bridged on the older one. but you can do 4ohms per side unbridged. so you can run two 4 ohm cabs stereo and get the 350ish watts per side. the 'current' electroacoustic amp can be bridged into 4 ohms.

Walter forgot to mention that there were some of the MI-200's that would go to 4 ohms bridged if it was ordered that way. I know because I ordered 2 of them from Walter in the early 90's. Still have the receipt!

[LarryR]

Gentlemen,
What an excellent discussion. 7 months later and I'm the beneficiary of your collective experience. Thank you all in advance.

I just bought a WW MI-200-8 from Ebay. FWIW I paid $ 1532.00. Yes, I'm willing to take all the slings & arrows for my "misdeed".
I expect to get the amp this Friday, April 13th. My question: is anyone willing to make me a couple bridge cables? Or, do you know a cabling company that would? I think I'd want both 1/4" and Speakon to accommodate a few cabs, one which only has 1/4".

[ctxbass]

http://www.bayoucables.com/

Top quality and great service from a fellow bassist.
You can look on the BG side for more info.

[LarryR]

Originally Posted by ctxbass

http://www.bayoucables.com/

Top quality and great service from a fellow bassist.
You can look on the BG side for more info.

Thanks for the info!