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Double Bass Can't Walter Woods be Cloned?

I have an WW MI 200-8 "Sweeper" (that is 3 way parametric EQ). This amp has the Bi-amp feature, meaning it has a variable crossover, consisting of a variable hpf for one cannel and variable lpf for the other. Now if I could just change one component inside and make the variable hpf start at 40hz instead of 100hz, I would have a perfect hpf build in for rumble and feedback etc purposes. Well I guess I will have to do without....

Interestingly, I've never wanted for a high pass filter with either of my Walter Woods amplifiers, I have a MI-400-8 (built before the Sweeper) and a Electroacoustic Ultra ( built after the MI-200-8). Both of those amps, by virtue of the cut/boost switches on the MI-400, or the
Vari, and Balance controls on the Ultra, allow you to easily reduce the bass content, in very small increments. Just moving those controls slightly, gives me the desired result. I tried using an The FDeck HPF Pre Amp, inserted into the effects loop, and found that I just didn't like
the way it sounded. Not a knock on the FDeck mind you, it's a wonderfully transparent device, but, for some reason, it's not a good combination with a Woods amplifier. It sounds fine into the front end.

Ric
 
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I don't care about cloning the circuit, but I would not mind seeing accurate performance measurements -- response curves and the like. If there is something magic about WW, then presumably it would not be revealed in the curves. But it would give those of us who don't believe in magic something to look at.

Francis,

I realize this is ages ago- but just for the fun of it, I redrew the schematic of an old WW MI100-8 (one channel, two separate preamp gain stages with the switchable option to use one or both) in circuitlab, and while a simulation is perhaps not as good as the real deal, it still talks volumes as to what is going on in the preamp (so far i have only done the preamp, as i suppose that is where the sound is- the power amp seems very normal to me). If you' re interested, drop me a PM (maybe too long, to detailed and too nerdy for this thread).

best
sidecar
 
Ric is right on here. I have never needed a HP filter with my WW Electracoustic amp. With my DB with a Full Circle pickup, my WW amp can get ridiculously loud -- much louder than I would ever want to play -- without any feedback problems. Walter is very proud of this design for good reason.

MrSidecar is right also. The power amp section in old WW MI 100 is right out of the RCA transistor manual with a couple of interesting twists added by Walter. The magic is indeed in the preamp, which was designed to simulate the sound of vacuum-tube (valve) amp.

It is interesting to note that the gain blocks used in the MI 100 (both -4 and -8) are similar to the topology used in the original fdeck HPF-Pre.
 
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Francis,

I realize this is ages ago- but just for the fun of it, I redrew the schematic of an old WW MI100-8 (one channel, two separate preamp gain stages with the switchable option to use one or both) in circuitlab, and while a simulation is perhaps not as good as the real deal, it still talks volumes as to what is going on in the preamp (so far i have only done the preamp, as i suppose that is where the sound is- the power amp seems very normal to me). If you' re interested, drop me a PM (maybe too long, to detailed and too nerdy for this thread).

best
sidecar

As far as I know the pre amp from the single channel MI-100-8 is unique to that amplifier, but I've compared my M-400-8 to an SVT and it's very close to the tone quality and power handling of an all tube amplifier. I'd love to see some
comparison pictures of the old RCA circuits and the Woods Pre Amp.


Ric is right on here. I have never needed a HP filter with my WW Electracoustic amp. With my DB with a Full Circle pickup, my WW amp can get ridiculously loud -- much louder than I would ever want to play -- without any feedback problems. Walter is very proud of this design for good reason.

MrSidecar is right also. The power amp section in old WW MI 100 is right out of the RCA transistor manual with a couple of interesting twists added by Walter. The magic is indeed in the preamp, which was designed to simulate the sound of vacuum-tube (valve) amp.

It is interesting to note that the gain blocks used in the MI 100 (both -4 and -8) are similar to the topology used in the original fdeck HPF-Pre.

Bob,

This is just fascinating, as once again an amp designer has gone to an RCA manual to find a design, and used it in a famous amplifier, apparently Jess Oliver, got the circuitry design for the Ampeg B-15N out of the RCA Tube manual. I guess
like minds come up with great resources. RCA manuals evidently provided the building block designs that were used in many great bass amps. Walter's amp are the whole package, with many design features that just aren't on any other amplifiers. Their so
well thought out that you just don't need any other signal processors, because the amp has all the tools you need. My only wish is that he would release schematics to bassist who were the original purchasers of his amps.

Ric
 
As far as I know the pre amp from the single channel MI-100-8 is unique to that amplifier

Ric,

it probably is in that respect that it has these two switchable gain stages. Other than that, although I might be wrong, I mean to remember from what I've read around that the controls and their design/freqs are the same.

My only wish is that he would release schematics to bassist who were the original purchasers of his amps.

I always thought that is just what he did with all his MI-100 amps, the two-channel version as well, and that he only ceased doing that in later designs with class-D power amps and op-amp preamps. Am I wrong?

Best
Sidecar
 
Ric,

it probably is in that respect that it has these two switchable gain stages. Other than that, although I might be wrong, I mean to remember from what I've read around that the controls and their design/freqs are the same.



I always thought that is just what he did with all his MI-100 amps, the two-channel version as well, and that he only ceased doing that in later designs with class-D power amps and op-amp preamps. Am I wrong?

Best
Sidecar

Mr. Sidecar,
That may very well be the case, so I'll have to defer to you on technical matters. The difference would be that there isn't a boost switch, on the two channel version of the MI-100-8. The two EQ sections are identical, but you can't chain Channel 1 and Channel 2 together on the dual channel version MI-100-8. Immediately below
is the front panel of the MI-100-8 Single channel, followed underneath by the front panel of the MI-100-8 Dual Channel.

Walter Woods MI 100-8 Single Channel.jpg
walterwoods_mi400_00031.jpg
 
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I have repaired several WW amps, from MI 100-4's from the 70's to recent vintage Electracoustics (please don't ask, I'm not in that business). The preamps on the early WW amps are similar, with only differences in details. The preamp circuits from the earliest models to the latest are fairly easy to troubleshoot for a competent audio tech. Likewise the early linear power amp sections. It can get tricky however in the switch-mode power supplies on any of the amps, and the later proprietary class-D power amp sections. While it would be nice if the schematics were available, unfortunately there aren't many people these days who understand what Walter was doing. He was way ahead of his time, and there were no off-the-shelf modules for class-D power and SMPS like there are now. Many of today's techs are really just parts changers. Trying to find someone who does component-level service is like trying to find a mechanic who can repair a carburetor on an older car. They are few and far between and getting more so everyday. Also the correct parts like Walter used are becoming hard to find. Anyway that's my rant. :D
 
.............While it would be nice if the schematics were available, unfortunately there aren't many people these days who understand what Walter was doing. He was way ahead of his time, and there were no off-the-shelf modules for class-D power and SMPS like there are now. Many of today's techs are really just parts changers. Trying to find someone who does component-level service is like trying to find a mechanic who can repair a carburetor on an older car. They are few and far between and getting more so everyday. Also the correct parts like Walter used are becoming hard to find. Anyway that's my rant. :D

Bob,
I certainly don't consider useful information a rant, it's a worthwhile piece of the Walter Woods repair puzzle.
I guess, it doesn't surprise me that Walter's probably the only qualified individual, who can repair his products, what
bugs me is the relatively low value, the semiconductor industry, puts on manufacturing replacement parts. I've mentioned on other threads, that's it's easier to repair and fully rebuild my Ampeg B-15N(C) then it is to repair my
Mi-400-8 or my Electroacoustic Ultra, and that's real shame. Granted it's a much simpler amplifier, the but tubes, resistors, capacitors, rectifiers, and transformers are readily available for the B-15N. Just my take. sorry for the rant.

Ric
 
Ric,

While there were many vintage Ampeg, Fender and similar tube guitar amps made, there were relatively few Walter Woods amps made. At one time the supply of vacuum tubes, high-voltage filter capacitors and other such components was rapidly drying up, but the demand for these things created a whole new market. The demand for some of the components that Walter used is very small and getting smaller. No one is going to manufacture or stock parts that there is little demand for.

Also as I previously mentioned, things have gone to the off-the-shelf module. Several of today's amps are based on these modules. If one of these breaks, you just replace it with another. Walter's amps are meticulously hand made from many individual components. This is rapidly getting more rare.

Someone should make a copy of a WW MI 100 preamp (any patents have expired) with something like an ICEpower module. The best of both worlds.
 
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My cabinet is an early Acoustic Image which could explain why I feel I could need a hpf. I am still experimenting on whether I like to use the bass control as a hpf (all turned down, and varying the frequency), or more moderately at a higher frequency, turned more moderately down.

I'm not certain what effect the HPF will have, in conjunction with the single down firing 10, that's part of those original AI combos. It gets its low bass response by "reflecting" sound from the floor, so I don't know what will happen when you combine it with the HPF, but it can't hurt.

I guess my concern would be that the FDeck HPF/Buffer Pre Amp, if not used very judiciously, might remove to much of the characteristic sound that's part of Acoustic Image's tone. You'll just have to try it and see. It's to bad that those early contra's didn't have a low pass filter, like

all the newer amps, from Series II, Series III, and Series IV(+) do.

Ric
 
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But the thing is, my Acoustic Image is just a cabinet/loudspeaker, that I use with my WW. If the variable cross over of the WW started lower it could be a build in hpf. Btw, put in the signal chain after the regular eq, which could be quite cool, I think. But you are right, I regulary experience the problem of taking away to much bass and ending with no "meat" and too much potatoes (treble, scratch). Ah, the challenge of having a deep, but firm sound.
 
I think anyone else would have trouble sourcing the baby-kisses and unicorn-tears used in making Walter's amps.

I think the Woods amps are amazing but personally, I find the AI amps to be more neutral sounding which I believe is the holy grail for DB amplification. I use the advanced features like, HPF and phase control daily in all but the most agreeable rooms. Also, I don't have to have a 2nd mortgage to buy an AI. I think it says a lot that every other post in this thread has made a comparison to the WW.

I don't dig the AI as much for electric bass only because I prefer your standard old-school Fender tones that require a lot of coloration to the tone. YMMV.
 
I think anyone else would have trouble sourcing the baby-kisses and unicorn-tears used in making Walter's amps.

I think the Woods amps are amazing but personally, I find the AI amps to be more neutral sounding which I believe is the holy grail for DB amplification. I use the advanced features like, HPF and phase control daily in all but the most agreeable rooms. Also, I don't have to have a 2nd mortgage to buy an AI. I think it says a lot that every other post in this thread has made a comparison to the WW.

I don't dig the AI as much for electric bass only because I prefer your standard old-school Fender tones that require a lot of coloration to the tone. YMMV.

Well, in the greater scheme of things Acoustic Image builds an excellent amp, and there easy to get serviced, because Rick Jones has made that a priority. I've used both Acoustic Image amps and Walter Woods, and frankly there are substantial differences between a AI, and a Woods, so I'll have to say that I personally greatly prefer the Woods, but they didn't cost $3,000.00, when I bought mine, and Walter was much easier to get in contact with for service. Walter's essential problem, is that since he used many different height quality components in his amps, it's becoming very challenging to source integral parts for amps he built 30+ years ago. So I don't think Rick Jones has anything to worry about. Acoustic Image amps just keep getting more refined, and better sounding. Walter's amps don't use the industry standard B&O Ice power module. As components for his power supplies and power amps get harder and harder to find, his amps will eventually be difficult, if not impossible to repair.

Ric
 
I have used Acoustic Image amps extensively, and they are great, no question about it. I just happen to love Walter's amps. I have even heard the same great DB players use both AI and WW amps, and for me, there was no comparison. I much preferred the Woods.

From a practical standpoint however, there is no comparison. AI amps have a great feature set, are reasonably priced, well made, very reliable and have excellent service available. OTOH it is a real adventure just getting in touch with Walter and you could buy another amp for what he charges for service now.

As far as which of these amps sound the best, I think this is like discussing which flavor of ice cream is best.

Even with all their drawbacks, I still love the Walter Woods amps. But that's just me.
 
I've been bitten by the G.A.S. bug and begun to think about another amp, although there's really nothing wrong with the ones I have. My only reason for considering another amp is that I think the older AI Clarus amps may lack clarity and power. They sound warm and natural but a bit closed in rather than open. The EQ isn't very effective. The Ampeg PB 250 has a great EQ but isn't the most natural sounding amp. As much as I'd like to have a WW I just can't justify it, because it doesn't seem like a good long term value. It seems a bit like buying an old classic car that's difficult and expensive to service. I've considered a Doubler and Clarus + series 4 but really can't pull the trigger. After experiences with series III AI heads, I prefer the earliest ones but would expect the Flex EQ to be an improvement. 2 ohm capability is important.
 
Mike Arnopol has been talking about a new amp he is working on with the cats from Sonic Farm. He says their 2di4 DI box sounds as good as it gets with upright and that this new amp is gunna be stellar... While we're waiting, and then waiting for someone else to buy it and rave about it, I still haven't found any preamp that sounds better for upright then the Headway. I think the Headway into a nice power amp (maybe the Minnie 800) or something similar ( I run mine into the power section of an AI Focus ) is damn good, and can make so many pickups sound good (not many other preamps have a variable impedance nor one so high). That said I tried my Shertler Stat B into a Demeter tube pre (an older rack space one) and into a power amp and that sounded stellar too. I know Demeter is making his Tube pre with a Minnie underneath it and I'd sure love to have one of those, but I wonder if I'd ever end up putting the Headway in front of THAT just because I needed some of what its got...then it would be too much....so until something tops the Headway in terms of function and tone, (or headway puts out an amp with the EDB2 as a front end) I think you can heardly beat it for
 
I've been bitten by the G.A.S. bug and begun to think about another amp, although there's really nothing wrong with the ones I have. My only reason for considering another amp is that I think the older AI Clarus amps may lack clarity and power. They sound warm and natural but a bit closed in rather than open. The EQ isn't very effective. The Ampeg PB 250 has a great EQ but isn't the most natural sounding amp. As much as I'd like to have a WW I just can't justify it, because it doesn't seem like a good long term value. It seems a bit like buying an old classic car that's difficult and expensive to service. I've considered a Doubler and Clarus + series 4 but really can't pull the trigger. After experiences with series III AI heads, I prefer the earliest ones but would expect the Flex EQ to be an improvement. 2 ohm capability is important.

I think that with the new Claris 4+, Rick and the folks a Acoustic Image, have gotten a nice defined, neutral, sound, with some improvements over the three band Claris 4's. Although, 2 ohm stable amps are interesting, I never bring
a pair of cabs to any gigs, so it's not important for an amp to have that capability. If the gig requires a larger cabinet, I either bring my TC 112 or run FOH into the house. In fact, these days, more often that not, I'm just running FOH through the Headway EDB-2. Owning a Woods, is exactly like
owning a classic car. Actually, it's kind of like owning a Tucker Torpedo or a Dusenburg, but you can machine parts for those cars, while you can't make you're own vintage discontinued semiconductors. I bought mine long ago, when they both cost about as much as a AI Clarus +. For me
it's not an issue, and the sound is spectacular, but then again, so is a Headway EDB-2 and it cost's a whole lot less.


Mike Arnopol has been talking about a new amp he is working on with the cats from Sonic Farm. He says their 2di4 DI box sounds as good as it gets with upright and that this new amp is gunna be stellar... While we're waiting, and then waiting for someone else to buy it and rave about it, I still haven't found any preamp that sounds better for upright then the Headway. I think the Headway into a nice power amp (maybe the Minnie 800) or something similar ( I run mine into the power section of an AI Focus ) is damn good, and can make so many pickups sound good (not many other preamps have a variable impedance nor one so high). That said I tried my Shertler Stat B into a Demeter tube pre (an older rack space one) and into a power amp and that sounded stellar too. I know Demeter is making his Tube pre with a Minnie underneath it and I'd sure love to have one of those, but I wonder if I'd ever end up putting the Headway in front of THAT just because I needed some of what its got...then it would be too much....so until something tops the Headway in terms of function and tone, (or headway puts out an amp with the EDB2 as a front end) I think you can heardly beat it for

I'm hoping that Mike will come up with something wonderful, he certainly has with the MAS4x5's. Like you, the EDB-2 is just the best little box out there, and it fits into one of the pockets in my DB Case. Headway built a guitar amp, with their pre amp as it's front end, but unfortunately, there wasn't a market for it, so the amp was discontinued. I'd doubt that they'll head back down that path. To much competition, to small of a market, but you never can tell. I'm looking at a Demeter Minnie, but if Mike gets his amp to market, then by the time I get around to buying one, Mike could have "built a better bass box.

Ric
 
I loved using the EDB-1 with the Amplite and could see possibly returning to something like that but what attracts me to the little Clarus is its simplicity. Plug it in and play. I'd like to find a small, integrated head with that Headway tone. Actually, the Ampeg sounds great and although not completely neutral, gets a tone that I like. It's 14 lbs and I prefer not to use it for that reason.
 
Even going back to the earliest versions I've always enjoyed playing through those Clarus heads and every version seems to move towards being ever more practical. I've been trying to sort out my sound with this new bass and this afternoon I looked at the stack of 2 heads, 4 preamps and Amplite and Stewart power amps that I've been trying in different combinations and I just kinda threw up my hands and said "shag it I'm getting a Clarus". I've only ever gotten to use a Walter Woods with the slab and I'd love the chance to see what kind of friends I could make with one with the double bass but that's kind of a fantasy right now. I don't think the Clarus is much of a WW "clone" but like the Woods it does seem voiced so that getting a good sound fast is not a struggle. I'm really ready to be done obsessing over this amp thing and just go play.