problem with Allen ADC 7000

[don60]

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I could use some help from an Allen technician or owner who has access to anADC 7000 or similar first-generation three-manual ADC organ. I recently purchased an ADC 7000 and have noticed a very offensive warbling noise on certain stops and notes across all divisions of the organ. Allen's literaturedoes admit that "individual keys played in the highest octave with only higher pitch voices (2', etc.) may produce slight extraneous sounds which can be misunderstood as a defective condition." But my problem occurs in lower octaves as well and could not be considered "slight" by even the most optimistic assessment. </P>


I am hoping that a member of this forum has experience with this model of organ and could tell me whether another specimen has the same issue. It would be very helpful to know whether this problem is a design feature or not before I spend many more hours on troubleshooting or (heaven forbid) pay for a service call. I can be much more specific about the nature of the noise and the stops and notes that produce it if anyone is able to help.</P></FONT>

[jbird604]

Re: problem with Allen ADC 7000



I've been servicing Allen since before the ADC era, though it's rare to see one as large as the 7000. I know that's an awesome instrument. Congratulations on your purchase.</P>


Don't so quick to dismiss the need for a service call. That's how some of us make our living! Maybe you'll be lucky and solve this by yourself, but that is a very complex organ and may require the services of a trained and dedicated Allen technician to sort it all out. I'm sure that he or she will be well worth the cost!</P>


Since "offensive" is often a matter of degree and opinion, I don't know whether to say that you are hearing something that you'll simply have to learn to live with, or if you have a genuine malfunction. There are certain artifacts present in the tones of these organs due to the relatively primitive digital tone generation, but nothing that I would consideroffensive enough to keep me from enjoying one.</P>


It is possible that you have a problem inone of the USFG(frequency generator) or USEG (envelope generator) boards. These are among the plug-in boards in the horizontal cages of your ADC7000. Other boards could cause such an effect as well, but these two come to mind as more likely suspects.</P>


However, these boards tend to be assigned only to certain groups of stops, and a malfunction would not normally cause a problem throughout the organ. In fact, there are very few components that are truly common to the entire organ in a system that large.</P>


You'll first need to identify exactly which notes of which stops are doing this. You can only be sure of what you're hearingwhen only one note of one stop is sounding. So play each note of each stop from top to bottom and identify the offending notes, making a list of them.</P>


Then, use the cage charts that you should find in plastic holders inside the console to determine whichboards are in common with all the offending notes. It may be immediately obvious that a certain board is causing the whole problem. If so, swapping that board for another IDENTICAL board in the system will cause the problem to move to an entirely different set of notes. (Note: when you swap boards between slots in the cages, remove any EPROMS from eachboard and swap to the other board, so that you leave the correct EPROM in each slot. Otherwise, you will get other anomalies which will not be related to board problems.)</P>


If you are able to determine that it is a single board, you can have it repaired by Allen, but you'll need a dealer or authorized tech to mail it in for you.</P>


It is also entirely possible that your problems are not due to a malfunction so much as poor connections. An ADC model is actually past due for a complete cleanup. We generally pull each board, one at a time, pull the socketed chips, lube the chip legs and re-insert. Then we lube (vaseline) the card-edge connector and carefully re-insert each board. Boards outside the cage need the same treatment where they meet various kinds of connectors. Audio connections, whether RCA or screw-on need lubing too. Terminal strips should be un-screwed, lubed, and re-tightened.</P>


Check all the voltages throughout the system. Replace batteries wherever they are found.</P>


ONE OTHER IMPORTANT STEP: the boards in the cage contain multitudes of mini-pots that regulate the level and tone of each group of stops. These mini-pots often develop dead spots or poor conductivity after years of use. You need to use a screwdriver that fits these little pots and carefully, gently, slowly sweep each ot through its range several times. Then restore them all to approximately where they were, or else do a complete voicing procedure using the cage chart and the voicing instructions which should be included in the plastic packet.</P>


Good luck!</P>


John</P>
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[don60]

Re: problem with Allen ADC 7000

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John,</P>


Thanks so much for your detailed reply. Although I have been a member of the forum for only a short time, I have read it frequently over the past two years and have learned that you are usually the go-to guy with the thorny technical questions.</P>


I wanted to provide you with some more information about my problem. I described the anomolous sounds as warbling, but the characteristic varies somewhat depending on the pitch and stop involved. Some notes sound as if they are modulated by a poor-quality tremelo while other notes sound as if a second, low-frequency tone is sounding along with the proper one. Regardless of the specific noise that occurs, I believe that the fundamental problem is the same. On a digital oscilloscope, all of the bad notes show a significant frequency modulation (as evidenced by a non-constant zero-crossing rate in the waveform) while notes that sound good to me show much more stability in the frequency.</P>


I have gone through all of the stops on all three manual divisions (the pedalboard is not installed at the moment) and logged the bad notes and stops as you suggested. At least a few notes are affected on every stop at or above 2' on each division. Specifically, the noise is noticeable to me on the following stops:</P>


Choir--Piccolo 2', Fifteenth 2', Tierce 1 3/5', Larigot 1 1/3', Fife 1'</P>


Great--Quinte 2 2/3', Superoctave 2', Doublette 2', Waldflote 2'</P>


Swell--Nazard 2 2/3', Flute a Bec 2', Tierce 1 3/5', Sifflet 1'</P>


Interestingly, most of the problem notes are E naturals or B naturals, starting in octave 3 (just above middle C) and extending to the top of the keyboard. Additional notes are affected in the top one or two octaves. I believe that the mutation stops on this organ are tuned as true overtones of the related fundamentals, so, for example, E3 sounded on 2 2/3', 2', 1 3/5', 1 1/3', and 1' stops would produce harmonically-related tones. Thus I am not surprised that a problem key will produce the noise regardless of which stop is drawn.</P>


I recorded some mp3s of the worst three stops (on the Choir) to illustrate the problematic noise; there does not seem to be a capability to attach them to this post, but if you can tell me of a way to get the files to you, I would be eager to hear your opinion regarding the objectionable nature of the sounds.</P>


Although the infamous plastic pounch that you mentioned was long gone when I bought the organ, I have acquired the Allen ADC service manual including model-specific data such as the card cage diagrams and stop rail layouts. I have done extensive board-swapping (keeping the EPROMS in the proper slots) and have never seen any indication that the problem moves with a board. I have tried pulling all of the boards except those for a specific division to eliminate the possibility of interaction among the divisions, again with no change. I have even unplugged the data connector from Cage B with no effect on the problem notes in Cage A. As you mentioned, very few boards in the organ are associated with more than one group of stops or more than one division. And it seems to me that swapping boards between divisions and cages has further narrowed the possibilities to the power supplies and the stop/keying multiplexer board.</P>


I have scoped the power supply busses in the cages and on the ancillary boards such as the multiplexer. While the voltages are not pristine, they do not look terrible; most noise is in the tens of millivolts range.</P>


So at this point, I would suspect one of three possibilities: a limitation of the system design (i.e., no actual malfunction); a defect in the multiplexer board that is producing a flaw in the keying data stream; an extensive multiple-board failure inside or outside of the card cages due to a severe electromagnetic event such as a line voltage spike or even a nearby lightning strike that coupled into the circuitry.</P>


As I alluded in my first post, I would find it invaluable to locate another functioning ADC 7000 or closely related model such as the 6800. If it produces the same kinds of artifacts, then the problem is just a design limitation to be worked with. I hope that one might still turn up through this forum.</P>


To eliminate the multiplexer board would require, obviously, access to a service board kit (i.e., a service call) or access to another similar organ. I am definitely not ruling out the service call, but am trying to gain more confidence in the source of the problem before I take that step.</P>


I have not discounted the possibility of a multi-board failure; in fact, I am starting to suspect that the organ may have been subjected to some kind of electrical stress. Immediately after I bought it, and while it was still stored in the garage awaiting its move into the house, I tested every note on every stop of every division, and all seemed to be well. (To be honest, the environment was so noisy that I may have overlooked the "warbling" noises.) Then one day, after the organ had remained unplugged from the AC line, I discovered that one alterable stop on the Swell and a group of four stops on the Choir were defective. The problem turned out to be one of the analog ICs on each of the associated TG boards (more on this incident later). And just last night an EG board in Cage A apparently failed, disabling the entire cage until I pulled the board this morning.</P>


In each of these incidents, I had done nothing to couple energy into the circuitry such as probing with a scope or multimeter. In fact, when the first incident occured, the card cage covers were still on. So I suspect that the organ suffered some kind of electrical damage either before I bought it or immediately after I took possession, and I am seeing delayed failures in vulnerable, overstressed components.</P>


When the TG boards failed, I did ask an Allen dealer to send them in for diagnosis. Not surprisingly, both needed repair at a cost of about $500 each. That amount strikes me as quite reasonable for a factory overhaul with warranty, and would be a necessary expense for a church that needs the organ to work reliably every weekend. But over $1000 was more than I wanted to spend, particularly when the organ was intended to be nothing more than a hobby. So I took a chance, ordered $30 worth of parts from Digi-Key, and replaced all of the analog ICs on the two defective boards; both boards came back to life and continue to work correctly. I realize that I may not be as lucky every time a failure occurs, but since the vast majority of the parts are not proprietary chips I believe that it is worthwhile for me to do as much of my own troubleshooting and soldering as possible before calling in the pros. I was educated as an electrical engineer with particular interests in communication theory, analog electronics, and digital systems (exactly the areas that deal with digital music!). So I meant no disrespect to you or the other Allen technicians when I said that I would rather not spring for the service call yet; it's just a matter of economics and professional pride for me to try to solve this problem on my own if I can.</P>


As you are well aware, Allen is unwilling to share component-level information about the card cage boards--the heart of the ADC organs. The service manual has been very useful in covering the external boards and in giving a system-level overview of the organ topology, but naturally I want more! I have resorted to probing key lines and busses in the tone generation system to learn about the waveforms (a work still in progress) and to reading the original Allen patents (going back to the MOS 1/Rockwell days); both have been exceedingly helpful in discovering some of the details of the system. But I could envision months or years of work to learn enough to troubleshoot or upgrade at the component level. </P>


Even if Allen were willing to talk, I am not sure that any of their engineers are familiar with the details of this system anymore since it was designed so long ago. Clearly, they have enough information on hand to reprogram EPROMS and fix boards, but that information may not be enough to explain the whys and hows of the system design. I am rather frustrated with the situation and periodically contemplate Hauptwerk as a solution to my woes!</P>


Well, John, I hope you might have a few more thoughts on my problem. Please let me know whether I can get the audio files to you so you can hear the problem firsthand.</P>


Regards,</P>


Don</P></FONT>

[jbird604]

Re: problem with Allen ADC 7000



Don, </P>


I'll send you a private message through the forum when I close this window. I'llgive youmy email address and you can try attaching your mp3 files to an email. If that doesn't work, if they are too big, try using one of the free file-sending services. I've done it a couple of times but have forgotten just how it works. Anyway, give that a try if you need to.</P>


Sounds like you've done your homework on this one! I think it's rather admirable that you want to do this kind of restoration, and do it yourself as a project. Yes, it could get very costly to have Allen renovatea bunch of those boards. I'm glad you were able to repair some of them at a reasonable cost.</P>


Actually, I've seen very few of these organs with catastrophic problems. Even when "lightning-struck" they often have only minor damage. That's why we always do a complete tear-down and lube job before we start replacing things. Also, do work on those mini-pots because trouble in those pots can cause a lot of noise and quirky operation. The tremulant and speech articulation pots on the USMA and USFG boards (I think that's where they are -- check your service manual) can also cause weird malfunctions if they are not clean.</P>


As you may have discovered, a USEG board can cause problems all over the place, even with stops that don't appear to be associated with it. So, the old troubleshooting trick of pulling them loose one at a time might be worthwhile here. Block down a key so that one of the offending notes is sounding, then pull (smartly and quickly) each USEG board out one at a time and see if the problem clears up. If so, you may have found theproblem. This is a longshot, but it could be your source.</P>


Sincethese problems are all over the organ, even in stops that come from different cages, it's alsopossible that some 60 Hz ripple is getting into the system somewhere. It's notable that you mention E's and B's being affected. You know that 60 Hz is near the frequency of B below the 8' C, and of course the third harmonic of E would also be a harmonic of the 60 Hz line frequency. So you may be having some AC line noise induced into the system somewhere. I'd check that out. Do you have a good surge and noise protector on it?</P>


These organs are pretty well shielded, but some kind of industrial equipment in your area could be causing interference. I've known electric fences and certain kinds of medical devices to do this even over some distance.</P>


I haven't known of a console multiplexer causing this kind of trouble. Anything is possible, of course, but I'll be surprised if it is the culprit. Power supplies may be common to both cages, not sure. But if you've scoped them they should be OK. I do remember having excess ripple in a power supply once that was causing odd problems. More than a few millivolts of ripple on any leg would be an indication of trouble.</P>


Anyway, I'll be looking for an email with your mp3s attached. After hearing it I might be able to tell you if it's just a quirk you'll have to live with.</P>


John</P>
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[jbird604]

Re: problem with Allen ADC 7000



Don,</P>


After church today my wife and I both listened to the top octaves of the 2' stops and higher, then came home and listened again to the mp3's you sent of the 7000. We both felt that what we heardfrom the 4000was not too different from the sounds you are hearing on the 7000. At times it does sound like other (lower) pitches are sounding along with a note, but I'm quite sure these are "heterodynes" produced by interactions between the note frequencies and some internal processing frequencies.</P>


My judgment -- those squealing noises are unfortunately typical and probably not fixable. Though I've never noticed any such artifacts before on any ADC, they were quite clearly audible in the top couple of octaves on stops pitched at 2' and higher.</P>


I think I told you about an old Allen MDC model (built around 1980 or so) that I serviced last week. Its higher-pitched stops had far worse squealing and squawking in the upper octaves than either your 7000 or my 4000. But even those are easy to overlook under normal playing conditions.</P>


So, for me at least, this is not a problem. And probably not for you either, or most organists playing on ADC models. After all, as I said earlier, who is going to play a 1' stop by itself in the top octave? Or any other high-pitched stop by itself, for that matter?</P>


I'm guessing, based on the information you gave me about all the time you've spent playing pipe organs and analogs, you are perhaps more sensitve to these artifacts than you will be afteryou become accustomed toplaying on this ADC. I think your ears and brain will soon begin to ignore these noises or consider them part of the "charm" of the technology!</P>


Of course, I may be wrong and there may in fact be something wrong with your organ. Since you're working on this as a personal project, I wouldn't discourage you from swapping boards around, replacing various components, upgrading the power supplies when feasible, etc. Who knows, you may discover ways to optimize these instruments that are not presently known even to the engineers at Allen.</P>


Best of luck. Keep us posted on what you discover.</P>


John</P>
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[Dave S.]

Re: problem with Allen ADC 7000

Hi Don, barring any unknown malfunctions it's quite possible that what you're hearing are normal anomalies, like John said. I was employed on an ADC-8000 for a few years, and I vividly remember a shrill undulation in some of the upperwork like you're describing. I had to be careful not to use too much upperwork with the manuals coupled together, it could get really ugly! This was in a vibrant 800+ seat acoustic, fwiw.

[jbird604]

Re: problem with Allen ADC 7000



Yesterday we serviced an ADC6000 in a very nice, lively 1000-seat sanctuary. The sameartifacts were clearly audible on high pitches when playing individual notes on single stops, particularly in the top octave. But certainly did not detract from the beautiful tone under normal playing conditions.</P>


Next time I service a Renaissance or Quantum I'm going to listen and see if these noises are still present. I suspect they have been greatly minimized if not completely eliminated in these newer models, with processing speeds 10 or 100 times higher than what was used in early digitals.</P>


Partner and Iagreed yesterday that this ADC6000 was a really fine organ. Personally I think it sounds better than any Renaissance or Quantum around here, but the acoustics just happen to be wonderful in there, and that is in fact the most important factor in a successful organ installation of any kind. (IMHO)</P>


So, if anybody has an ADC 6000, 7000, or 8000 that they want to give away, please let me know and I'll be right over.</P>


John</P>
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[myorgan]

Re: problem with Allen ADC 7000



John, et al.</P>


Could it be that the highs may be turned too high on the voicing boards? I've noticed--especially with the ADC--that if you turn that pot up too much in an effort to offset the bass in a dry environment, there tends to be more distortion or extraneous sound coming from the speakers. I've noticed this especially at close proximity to the speakers.</P>


Just a thought.</P>


Michael</P>

[Philip the organist]

Re: problem with Allen ADC 7000

[quote user="jbird604"]....

So, if anybody has an ADC 6000, 7000, or 8000 that they want to give away, please let me know and I'll be right over.</p>
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[/quote]</p>

Ditto![:)]
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[jbird604]

Re: problem with Allen ADC 7000



Iyield to Philip on this.... so the first free one goes to him, then I want the next one.</P>


Michael -- certainly the extraneous noises are exaggerated when the treble is turned up, but the artifacts we're talking about are more about pitch distortions. You have 3 Allens there to listen to. See if you can hear it in the top octaves. </P>


Try the 2' flute or1-3/5Tierce in the swell and see if some ofthe top octave notes seem to have extra lowerpitches mixed in with the correct ones. Onyour MOS2 organ these may be masked rather well by the doubling effect of the dual computers. However, it may be quite noticeable on the 6000, as it was on the one Matt and I serviced Monday. Your 4300 is later technology and may not have this issue at all.</P>


(Now you'll be hearing this all the time! -- Sorry to have made you aware of it.)</P>


I remember hearing this for the first time on old MOS-1 organs when I first started servicing Allen in the early 80's. But I am not bothered by this in the least. No more a problem than the various mechanical noises and air leaks in a typical pipe organ.</P>


John</P>
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[Guest]

Re: problem with Allen ADC 7000



I tried out all the 2' stops on my ADC7000 today. (It's in NY and no, I'm not about to give it away. It's in an all-wood 800 seat sanctuary and particularly when there are no people in the chairs the sound is awesome). I couldn't hear any "warbles" in the pitch, or extra lower tones - they all sounded clean. The only anomaly is a kind of hiss like a leaky windchest that shows up in the top 5 notes of the Doublette only. I have the treble turned down on the big wound resisters in the speaker crossovers, but the 2' stops are still plenty loud compared with the others. I've cleaned all the card edge connectors and EPROM pins with contact cleaner when I got the organ two years ago - I'm the second owner. The 32' Contrabombarde was making a really weird noise a few weeks ago and all it took was cleaning and re-seating the EPROM chips to fix it.</p>

So maybe you do have a problem that wasn't designed in. Or else you have a very discerning ear. I couldn't hear anything I'd call obnoxious in the high ranges- no more than the normal 8-bit aliasing that shows up especially in the mixtures, which always seem a little "jangly".
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[Philip the organist]

Re: problem with Allen ADC 7000

[quote user="jbird604"]

Iyield to Philip on this.... so the first free one goes to him, then I want the next one.</p>

[/quote]</p>

Aw, gee whiz, thanks so much John. [:)] You just know that when one comes along and gets installed at church, I won't be bugging you any more about every MOS that turns up on CL. [;)]. </p>

Sometimes my ADC does have these highpitched noises but nothing too obnoxious. But there is a lot of HF noise from the tone generators themselves, like on a solo flute. Maybe this is the fault? On full organ it's masked entirely.
</p>

[jbird604]

Re: problem with Allen ADC 7000



Philip,</P>


I'm not sure to what extent this problem affects the ADC420. Next time I service one I will try to make a mental comparison.</P>


As I've said all along, this is not a major problem with ADC organs, not even a minor problem in my estimation. It's just a characteristic of the technology employed. One would normally not even notice these noises except under "test" conditions -- playing individual notes of individual stops in the very top octave -- how often does that happen in the course of playing the standard organ literature?</P>


It appears that ADC7000 organs are getting traded in and passed around lately. Don't know how you and I both missed them! I do hope one of them turns up for your church. Or at least a nice MOS2 organ like Michael found.</P>


John</P>
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[don60]

Re: problem with Allen ADC 7000



Thanks to everyone who took the time to write about my little problem. John, I especially appreciate your help and your willingness to share your knowledge and experience with us.</P>


Dave, I like your term "shrill undulation" to describe the sound. It is more appropriate and graphic than my description of a "warbling"noise. Despite this shortcoming, your old ADC 8000 was probably in most respects a wonderful instrument with some very impressive tonal resources. I drooled over onea couple of years ago until I realized thatthe console alone weighed in at over 700 lbs and that it would have taken up my entire living room. (The problem of its being too wide to fit through thefront door was easily solved with a reciprocating saw--for the doorway, not the organ, I hasten to add.)</P>


JoL, I am especially pleased to make your acquaintance as yours is the only other ADC 7000of which I have first-hand knowledge.I actually wondered for a whilewhether Ihave the only one that Allen evermade, a suspicion that was reinforced when I noticed that the bigglossy color picture on the front of the ADC 7000 fact sheet is actually a photo of a 6000! It's good to know that there is at least one more of these instrumentsout there. I do hear the hiss that you describedin the top octave ofthe highest-pitched stops, along with the noise that I described. If you have a chance, try listening for the "shrill undulation" on the 1 3/5' and 1 1/3' stops on the Choir--these stops seem especially obnoxious to me, although the problem spans all manual divisions. Concentrate in particular on E natural and B natural in Octave 3 (the one that starts with middle C) and Octave 4. It's possible that in a large room with speakers at some distance from the listenerthe noise would not be noticeable until you listen for it very deliberately.</P>


The strong consensus here is that this warbling noise is not a specimen defect in my organ but a feature of the ADC system in general. So my original questionhas been answered, and for that I again thank everyone who shared his experiences. </P>


I was interested to read the differing views on whether this noise is a problem artistically, though. Clearly, Allenwould have been aware of it at the time of development; they must have judged it to be inoffensive to most users under most conditions or they would not have released the design to production. As John said, one does not draw individual high-pitch stops and listen to individual notes on them in the ordinary course of playing music. On the other hand, I can set up a more typical registration such as flutes 8', 2', 1 1/3' and still hear some traces of this problem on the worst notes, particularly if they are held for a moment as theymight be in an adagio passage.</P>


My assessment (trying to be diplomatic here) is that the problem is not a defect per se, because the system is working as the engineers designed it, but rather a failure of the instrument to meet the expectations of at least some users. Those who came up on analog electronics and pipes, as I did, probably will find it disappointing in an otherwise nice-sounding organ. Others such as John, who have spent many years listening to this technology, will probably view it as nothing more than a quirk. We can point to many instances in our lives in which the same sound (lawnmower running, spouse snoring, etc.) can be viewed alternately as a profound annoyance or as a comfort, depending on the listener's relationship to the source of the noise.</P>


Although personally I am somewhat disappointed athearing this noise,I am not going to be holding a "free to a good home" event anytime soon!</P>


As far as the technical explanation for the problem, I believe we can discount "possession by demons" as the cause. Certainly, the problem must be rooted in some fundamental feature of the tone generation system, or the engineers would simply have used a few more chips to overcome it. I have a couple of ideas and plan to take more measurements and crunch some numbers to see whether a plausible hypothesis emerges. I will report back on my findings here if I come up with some worthwhile information.</P>


Best wishes,</P>


Don</P>

[myorgan]

Re: problem with Allen ADC 7000



Now that I've read this thread through and through, I remember that when I got the ADC-6000 that the Choir seemed to be slightly out-of-tune with the rest of the organ. When I used it for the symphony, I didn't notice it in the recording, but when I practiced privately, it was quite noticeable. I wonder if that could be related to re-seating the e-proms?</P>


I loved the voicing of the Choir when it came to me, so I absolutely didn't want to lose that ensemble. On the other hand, the Great was voiced like a bulldozer going through a china shop! I got it tamed, though.</P>


Michael</P>