Allen ADC 1000 question

[Dogstar]

Recently I have noticed a fluctuating sound especially in the higher notes in the swell. Almost like the tremulant is on but less pronounced and faster than the normal tremulant. It is not a practise stopper but it gets a bit irritating after a while. I'm wondering if this is maybe just a matter of cleaning edge connectors in the cage.

Any thoughts or advice would be welcome. Thanks in advance.

[myorgan]

Recently I have noticed a fluctuating sound especially in the higher notes in the swell. Almost like the tremulant is on but less pronounced and faster than the normal tremulant. It is not a practise stopper but it gets a bit irritating after a while. I'm wondering if this is maybe just a matter of cleaning edge connectors in the cage.

Dogstar,

Is it like the treble is dropping out and back in again--kinda like being underwater? I've had that happen with a couple of different situations.

One immediate thought is that the Treble pot on a card is having issues, and can be remedied by just slowly exercising the pot a little. See if you can track it down to a particular stop or group of stops. The next question is, are the speaker wires in the same jacketed wire (i.e. 4/14 or 6/14)? If they are in the same jacket, it could be they are causing distortion through the amplifier. I've got to track that down on one of my own organs. The last thought is that if your keyboard has leaf contacts vs. reed switches, the extremes of the keyboard can oxidize and create intermittent contact issues when playing high or low notes on the keyboard.

Maybe I'm all wet, but if you can narrow the sound down to a particular stop or group of stops, manual, or keys, that may help diagnose further.

Michael

[Dogstar]

Thanks Michael.
Your thoughts regarding the pot are certainly worth checking. Certainly quite noticeable on the 8 Gedackt. Seems to be there in the background on all the stops though. also noticeable on the presets too. This did happen a year or so ago but corrected itself thus the pot or connectors might seem the most likely culprits. Doubt if it's keyboard contacts as it seems to be right across the keyboard but more noticeable above middle C. Wouldn't expect it to be speaker wires as they are all original and have not been moved. We have had a lot of lightning storms recently but I have always uplugged the organ.

[Dogstar]

Well, today I removed each board from the cage and cleaned all of the edge connectors. Some looked like they really needed it too. Cycled all the pots after carefully noting where they were set. I think there is somewhat of an improvement. Sometimes one becomes so focused on it that you almost seem to notice it when it is isn't there. Each stop seems fine by itself but sometimes a bit of a shimmering between two stops eg. 8ft and 4ft. Maybe this was always there. Anyway I plan to live with it the way it is right now. Still threatening to midify and install Hauptwerk. Right now I'm torn between spending more money on the ADC 1000 or trying to trade it for a later model with midi already installed. otherwise starting from scratch and getting some new keyboards midifying a pedalboard and putting it all together as a separate Hauptwerk project. Decisions decisions.

BTW your description of sounding underwater was right on. Forgot to mention that last night.

[jbird604]

DS,

There will always some slow-motion movement or pitch-shifting in evidence when 8' and 4' stops are drawn, as the ADC models are designed to do that. The intent is to give the individual stops some separateness by using different pitch references. What you should hear is a subtle and fairly slow "phasing" effect when, for example, the Principal 8 and the Octave 4 are drawn together. Since pipe organs are nearly always a bit out of tune, this phenomenon is intended to make the sound a bit more like what you'd hear on a pipe organ.

Also, keep in mind that Allen digitals have always employed what they call "random motion" as part of the tonal mix. This is, in effect, a rapid "jitter" or white noise that seems to modulate everything all the time. Again, this is to suggest what you'd hear out of pipes. Listening to pipes, up close especially, you notice that there is a subtle "sputter" and perhaps some unsteadiness to the pitch. Random Motion attempts to mimic that effect.

A third thing going on is "speech articulation", another Allen specialty. This is a sometimes quite noticeable "dip" in the pitch of higher pitched tones whenever lower pitched notes are keyed. The idea is to emulate what might happen in a pipe chest when the big pipes, having large toe holes, rob some of the air at the moment of being keyed, thus slightly affecting the pitch of smaller pipes. If you want to hear this effect clearly, draw a 4' stop such as the Octave 4. Hold down the fifth C key. While holding down that key, play a staccato series of notes in the bottom octave. As each of the staccato notes is struck, you will hear the pitch of the high C do a "yip" as it falls quickly and then recovers.

With all this stuff going on, it's a wonder anyone can hear any malfunction in an Allen! However, I know that I sometimes hear a pitch instability in an ADC model that's not supposed to be there. Sometimes cleaning all the boards AND the legs of the EPROM chips will help, as will exercising all the pots. But sometimes the USFG boards in the cage are developing some weak chips that don't deliver a pure enough pitch. And sometimes that gets worse, much worse, requiring replacement of the boards. But if yours just sort of comes and goes, it's probably not about to fail.

So maybe it's just a combination of all the normal stuff, and on some days you hear it better due to different conditions. I wouldn't worry about it unless it becomes unbearable.

[myorgan]

DS,

I have to follow up on John's post. I noticed something similar to what John describes when I attempted to check the tuning of my practice organ. I noticed when I coupled manuals (Swell to Choir) that the tuning was quite off. It was only then I discovered each manual was tuned a few cents sharp or flat, and within each manual they used stretched tuning. That would account for what John is describing.

John can correct me if I'm wrong, but isn't the ADC-1000 an MADC organ? If so, would it have the separate articulation card like my ADC-4300, or would it have "built in" articulation like my ADC-5400 and the ADC-6000? If it is a separate articulation card, maybe the articulation needs to be adjusted?

John, I'm now going out to the garage to try out your 4' Octave trick to see if I can replicate it on my practice organ. Thanks for the information.

Michael

[jbird604]

Michael,

The ADC-1000 is part of the original ADC product line, before the MADC models (1100, 2100, 3100) came out to replace the 1000/2000/3000 series of ADCs.

So in design his 1000 is more like your 6000, though obviously greatly simplified, with fewer boards in the cage, etc. There was no TG-10 articulation board back in that time period, so the only enhancements to the tones are those I described above, along with the "chiff" that was associated with some of the voices, an effect not much different from MOS chiff. Chiff on those early models is actually just another "stop" that exists on one of the regular boards and is drawn automatically with certain stops.

Different ADC models have different degrees of pitch offset between the stops and between the divisions. That is one effect that I failed to mention in my little dissertation above. So, coupling the swell to the great on the ADC-1000 (or any other of the non-MADC models) will add yet another factor -- the intentional pitch offset between the two manuals. This is another possible source for some pitch instability and audible artifacts.

It might be noted that the offset between great and swell manuals is done differently on all MADC organs, including the low-end 220, 221, 222, 420, 430, 520, 530, 720, and the upscale 1100, 1110, 1130, 1140, 2100, 2110, 2130, 2140, 2160, 3100, 3160 and others I may have left out. On those organs, the offset in pitch is disabled when the swell is played from the great via the coupler. This is true simply because of certain shortcuts in the design of the tone generation system.

I hope you're having fun listening for that "speech articulation" effect! It is a neat little phenomenon that many folks have never noticed. Once you notice it though, you can't stop hearing it. Like an ear-worm!

[Dogstar]

You have summed it up very well, John. I think you are correct in your observations. I have also noticed that the sound a few feet away from the organ is quite different and better sounding than right at the console with its internal speakers. Observed this when recording a video of some of my playing to be able to evaluate things you don't notice while playing. I also have hearing aids. I am not as deaf as a post ;-) but I do have some loss at the higher frequencies which makes speech in crowded areas harder to differentiate at times. I wear them when playing. Maybe I should just turn 'em off.

Not sure if the ADC 1000 is an MADC, Michael. I don't think so, but I stand to be corrected. Thanks for you thoughts also.

BTW Didn't pull the only EPROM chip I saw. I was scared of damaging it and just making things worse. I was brought up in the age of tubes. I'm always scared of damaging stuff around PCBs

[myorgan]

DS,

Welcome to the club!!!

BTW Didn't pull the only EPROM chip I saw. I was scared of damaging it and just making things worse. I was brought up in the age of tubes. I'm always scared of damaging stuff around PCBs

John is right, it is not an MADC. In fact, I learned the difference as a result of this thread. Thanks Dogstar!

Michael

[jbird604]

You do need to be careful with EPROM chips, because the legs can be easily bent when re-inserting. I pull them very gently by prying loose from both ends alternately using a very thin screwdriver wedged between the chip and the socket. Then I clean the legs with the edge of a sharp knife, lube the legs with Vaseline applied with a Q-tip or piece of soft paper towel, wiping away all but a trace of it. Then I carefully re-insert, watching each leg go into the designated spring-loaded pocket. I have to use a flashlight most of the time, and sometimes a little mirror to be sure I'm not letting one of the legs get curled up underneath the chip. Also, sometimes the legs are "sprung" outwards, intentionally I suppose, to help them stay in the socket. But I find this annoying, and may use needle-nose pliers to straighten them so that all point straight down, making insertion easier.

Before going to all that trouble, just place the board on a resilient flat surface such as a magazine (so the protruding solder joints won't dig into your table top) and firmly press down on the EPROMs to make sure they are completely seated. You'll be surprised how many of them will have worked loose.

[Dogstar]

Well here's an interesting outcome for you. I can hardly believe it so won't blame you if you don't. :->

The organ has been o-k since I cleaned things up. Practised for an hour this morning and still just fine. Did a little more practise this afternoon and the wavering pitch was back. Aaaargh! I asked myself what is different and the only thing I could think of was that the ceiling fan was on. My music room has a cathedral ceiling about 15 feet high with a fan in the peak and a bit to one side of the organ. I like the feel of the airflow over my legs while playing on warm afternoons. Anyway, I got up and switched the fan off. After a few seconds the organ sounded just fine again with a steady pitch on all notes. I couldn't believe it, so switched the fan back on, almost immediately the wavering was back. Tried several more times to confirm and that was it.

I do not think it is an electrical issue as it didn't stop or start immediately I threw the switch. Took time for the fan to come up to speed or stop turning when switched off. I think it must be the flow of air across the speakers in the console. So I guess I now have an extra tremulant tab. You just turn it on with a wall switch. ;-)

I know that sounds weird, but that is definitely the issue. I was glad to find it as the problem was bothering me. Hopefully it might help someone else who is having obscure audio issues.

[jbird604]

I didn't think to ask if you had a ceiling fan. We run into that quite frequently, especially in small churches. Something about the big fan blades, and their position between floor and ceiling. They really do introduce a tremulant into the sound, and it's not a pleasant one either.

I'm glad it was so simple. File this for future reference and maybe you can advise the next person who complains of wavering pitch!

[myorgan]

Well here's an interesting outcome for you. I can hardly believe it so won't blame you if you don't. :->

What an odd coincidence! My wife played her violin for my relatives in the South (much further South than you), and it sounded like she was under water. We finally figured out it was the ceiling fan blades. What happens is that the blades compress the air when the blade is reflecting the sound, and then the air between the blades returns to normal. As a result, it's something like the Doppler effect and a passing train or car horn.

Think of the Vox Humana with older Reed Organs and the effect it produces with a revolving fan blade. Also, I think higher frequencies are more subject to this effect because the physical wavelength is not as large, therefore it cannot escape the effect of the fan blades. However, the bass frequencies, being physically longer, would not be as affected by a ceiling fan. In reading online, one person observed when he whistled, the (pedestal) fan had more effect on the sound than when playing a note from an instrument.

Certainly an interesting subject for discussion. Good powers of analysis to solve your own problem! Thanks for sharing.

Michael

[toodles]

Austin pipe organs sometimes used a "fan tremulant" arrangement. Their universal air chest (an air chest you can walk into through a full size door" makes such a steady reservoir that you just can't shake the air!

Have you tried the ceiling fan at different speeds to see which one you like the best?

[Hamman]

Sounds like an open Leslie?? LOL