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Walter Woods Amps History and Development

#301
Hi Guys,

Great thread!

I have a few WW questions that were sparked by this discussion.

On the bottom of my WW, in addition to the serial number being stamped into the metal, there is a 12 stamped in the far corner.

An idea what this refers to? Build number? wattage?

Does anyone use their WW rack mounted and if so, are they using original WW rack ears or something else.

Also, if rack mounted, are you using rack fans over the WW to keep it cool in the rack?

Should the power chord be completely unwound during operation to get it away from the fins?

What power conditioners, if any, is everyone using with their WW?

Anyone using a preamp for phase switching, feedback roll off, or anything else? (mostly a DB question)

What direct boxes are being used?

anyone using effects in the effects loop?

Can the effects loop be used as an output to a tuner?

Thanks!
 
#303
Munjibunga said:
Whoa! This is less than 3 miles from the San Andreas Fault ... the section voted most likely to move next by seismologists in the know. I'd pick up one of his amps pronto if I were you guys.
Click to expand...

The Japanese have known for centuries that lightweight design and construction is the best defense against earthquakes. :D
 
#304
macteacher said:
Hi Guys,

Great thread!

I have a few WW questions that were sparked by this discussion.

On the bottom of my WW, in addition to the serial number being stamped into the metal, there is a 12 stamped in the far corner.

An idea what this refers to? Build number? wattage?

Does anyone use their WW rack mounted and if so, are they using original WW rack ears or something else.

Also, if rack mounted, are you using rack fans over the WW to keep it cool in the rack?

Should the power chord be completely unwound during operation to get it away from the fins?

What power conditioners, if any, is everyone using with their WW?

Anyone using a preamp for phase switching, feedback roll off, or anything else? (mostly a DB question)

What direct boxes are being used?

anyone using effects in the effects loop?

Can the effects loop be used as an output to a tuner?

Thanks!
Click to expand...
Racking and cooling: All amplifiers need ventilation to prevent overheating. Walter Woods amps can cool themselves adequately in open air, but if you restrict airflow in a rack, you may need to consider forced air cooling using a fan.

I've used the power cord fully and partially unwound. Doesn't make a difference.

Power conditioners shouldn't be necessary.

I have used the Invalid Link Removed by TB's fdeck. It works very well for phase switching and low frequency roll off.

Any good quality direct box should work just fine. I really like the Countryman Type 85, which has a high impedance buffered input, and has been a professional standard for many years.

The "send" or the "direct out" (on Electracoustic models) can be connected to a tuner.
 
#305
macteacher said:
Hi Guys,

Great thread!

I have a few WW questions that were sparked by this discussion.

On the bottom of my WW, in addition to the serial number being stamped into the metal, there is a 12 stamped in the far corner.

An idea what this refers to? Build number? wattage?

Does anyone use their WW rack mounted and if so, are they using original WW rack ears or something else.

Also, if rack mounted, are you using rack fans over the WW to keep it cool in the rack?

Should the power chord be completely unwound during operation to get it away from the fins?

What power conditioners, if any, is everyone using with their WW?

Anyone using a preamp for phase switching, feedback roll off, or anything else? (mostly a DB question)

What direct boxes are being used?

anyone using effects in the effects loop?

Can the effects loop be used as an output to a tuner?

Thanks!
Click to expand...
I use original WW rack ears with my Electracoustic Super in a 4 space SKB case that also has a Korg DTR-1 tuner above the amp and a SL Waber rackmount power strip above that. No fan required from years of experience with this setup in all kinds of gigs indoors and out. I have checked the fins for heat and they are at most barely warm, even in outdoor gigs with no cover for the stage.

The FX out can be used for a tuner if desired. I run from the DTR-1 into one channel of my Super so I can use the mute function of the tuner. I suppose I could do the same in the FX loop but that would mean extra cabling.

I keep the power cord wrapped up next to the amp, not on the heatsink, but only because of how I have the power cords dressed in the rack going to the power strip.

I run the line out to a Radial Pro2 DI with excellent results.
 
#306
Thanks for the responses guys.

And does anyone else have a 2nd number stamped in the bottom of the amp in the corner besides the serial number?

Any idea what this might represent?

Two more questions about the rack mounting.

Do you remove the handle to rack mount the WW?

Also, is there anything special about the WW rack ears or are they just sheet metal as I'm not sure Walter builds them anymore and might like to build my own.

Thanks.
 
#307
I noticed that all of the old messages withs pics of Walter's first amp are missing the pictures. Here's mine. It quit on me about four years ago, and Walter wouldn't let me ship it back to him for repairs. I'm now using an Acoustic Image Focus. The AI is close to the old Woods in sound. The newer Woods are brighter. Someone once measured the original Woods, and it had about 5% harmonic distortion. Since it was mostly the 1st octave harmonic, it actually made the sound of the early piezo pickups warmer. I believe that was what attracted upright players to these amps.

George
 
#308
61pollmann said:
.............. Someone once measured the original Woods, and it had about 5% harmonic distortion. Since it was mostly the 1st octave harmonic, it actually made the sound of the early piezo pickups warmer. I believe that was what attracted upright players to these amps.

George
Click to expand...

George,
Some where in this thread, way at the beginning there is a picture of the amp. This thread has gotten pretty long. If you go to Hubert's Tube Amps web page you will find confirmation of the distortion figures. There was also another test that stated that distortion occurred at around 100 Hertz, which is also apparently close to the frequency of the switching power supply. IMHO Walter found someway to use this "distortion" to sweeten the sound of the amp, but since I'm not a techie I herby disqualify myself and defer to those who have more knowledge of such things.


Ric
 
#309
I do not have to remove the handle or the feet to rackmount my amp. The WW rack ears are nicely made and finished heavy gauge aluminum, but you could make them yourself easily enough if you have the metal working ability and a brake to cleanly bend the metal as half of the ears are actually replacement side panels for the amp itself.
 
#310
Since Walter will not let me send it to him, even for diagnosis, I'm wondering if anyone might have a suggestion for getting it diagnosed. I believe that all the parts are standard, except for the switching power supply. Even when he started using hired help to solder and assemble his amps, he still made the power supplies himself. Probably to protect his proprietary design. On his early amps, he even removed the markings from the standard components, so that the circuit could not be easily copied. That, of course, made repair by anyone other than himself rather difficult. If anyone has any suggestion for trying to get this classic amp working again, I would greatly appreciate it.

By the way, his secrecy, as well as age, caused me not to buy a new Woods amp. The $$$ is also getting steep. I've been very happy with my Acoustic Image amp.

George
 
#311
61pollmann said:
Since Walter will not let me send it to him, even for diagnosis, I'm wondering if anyone might have a suggestion for getting it diagnosed. I believe that all the parts are standard, except for the switching power supply. Even when he started using hired help to solder and assemble his amps, he still made the power supplies himself. Probably to protect his proprietary design. On his early amps, he even removed the markings from the standard components, so that the circuit could not be easily copied. That, of course, made repair by anyone other than himself rather difficult. If anyone has any suggestion for trying to get this classic amp working again, I would greatly appreciate it.

By the way, his secrecy, as well as age, caused me not to buy a new Woods amp. The $$$ is also getting steep. I've been very happy with my Acoustic Image amp.

George
Click to expand...

If it were sitting on my bench...

I would break it down into the preamp, power amp, and power supply. A voltmeter will tell you if the supply is functioning.

There's a good chance that the signature sound is a function of the preamp, and that one can make an educated guess as to the choice of components or at least suitable replacements. I'd get that part up and running on an external power supply or even a pair of batteries. If it works, one could always use the preamp with a contemporary amp head.

It may even be safe to bet that the preamp is not what is broken.
 
#312
61pollmann said:
Since Walter will not let me send it to him, even for diagnosis, I'm wondering if anyone might have a suggestion for getting it diagnosed. I believe that all the parts are standard, except for the switching power supply. Even when he started using hired help to solder and assemble his amps, he still made the power supplies himself. Probably to protect his proprietary design. On his early amps, he even removed the markings from the standard components, so that the circuit could not be easily copied. That, of course, made repair by anyone other than himself rather difficult. If anyone has any suggestion for trying to get this classic amp working again, I would greatly appreciate it.

By the way, his secrecy, as well as age, caused me not to buy a new Woods amp. The $$$ is also getting steep. I've been very happy with my Acoustic Image amp.

George
Click to expand...
George,

With all due respect, your Walter Woods amplifier is at least 35 years old. I can't think of one manufacturer that supports amps that are even close to that old. Perhaps there are a few, but they are very rare if they do.

Schematic diagrams for your amp (model MI 100-4) are readily available. PM me, and I'll be glad to send them to you.

As fdeck mentioned, you can check the power supply DC voltages. Your amp should have +/- 35 to 40 volts DC on the main rails. If so, your problem is probably in the audio circuitry, which is relatively straightforward: all discrete transistor Class A preamp with an all discrete transistor Class AB power amp. Any good technician that really knows their stuff should be able to troubleshoot these things.

In reality though, parts do become obsolete and sometimes are no longer available. You really can't blame the amplifier maker for parts such as semiconductors going out of production, since they have no control over this. If anything component parts become obsolete in less time now than they did 35 years ago, as the rate of change in technology constantly increases.
 
#314
robgrow said:
If so, your problem is probably in the audio circuitry, which is relatively straightforward: all discrete transistor Class A preamp with an all discrete transistor Class AB power amp. Any good technician that really knows their stuff should be able to troubleshoot these things.
Click to expand...

Did WW switch to op amps subsequently? I've seen the MI-100-8 schematic, and the preamp is fairly straightforward op amp based.
 
#315
fdeck said:
Did WW switch to op amps subsequently? I've seen the MI-100-8 schematic, and the preamp is fairly straightforward op amp based.
Click to expand...
The first two generations of Walter Woods amps (including the MI 100-8) used discrete transistor class A preamps. The gain blocks are comprised of an FET and a bipolar transistor, similar to the high pass filter circuit in your HPF-Pre. The last two generations of WW amps use monolithic IC opamp based preamps.

In the schematic here: http://www.talkbass.com/forum/attachment.php?attachmentid=126434&d=1240585934, you can see the discrete transistor gain block (the A in the triangle thing :D) located above the power supply, and to the left of the power amp.
 
#316
robgrow said:
George,

With all due respect, your Walter Woods amplifier is at least 35 years old. I can't think of one manufacturer that supports amps that are even close to that old. Perhaps there are a few, but they are very rare if they do.
Click to expand...

We did. Loud stopped that nonsense very quickly.

IIRC the old WW uses a type and case style of output transistor which is obsolete, hard to find, and very expensive now. It's been a long time since I worked on (or saw) one of those.
 
#317
robgrow said:
With all due respect, your Walter Woods amplifier is at least 35 years old. I can't think of one manufacturer that supports amps that are even close to that old. Perhaps there are a few, but they are very rare if they do.
Click to expand...

Mesa/Boogie? They hit the 40-year mark this year.
 

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