# NPD...NPd...Npd...npd..



## b-nads (Apr 9, 2010)

;-)

I've been Jonesing a Maxon AD999 for a long time, but they're pretty pricey and don't see, to pop up often. I scored one last night that is new in box...swapped two pedals to get it that would have brought me what the guy was asking for the Maxon if I waited a month or two, so I'll live with the lop-sidedness of the swap.

I've only gotten to run it for an hour or so at lower volumes, but so far I'm very happy. It is much bigger sounding that the digital delay I've been using. The long delays are very warm and smoky - almost haunting. The slapback setting is slightly less bright than the Aqua Puss, but every bit as good if not better - I mostly use slapback for country and blues, and tend to have my amp eq'd bright anyway, so the AP almost has too harsh a clip to it - the AD999 doesn't.


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## Voxguy76 (Aug 23, 2006)

Great great pedal, congrats. I've had a tonne of delays and the AD999 has got to be one of the warmest sounding analog delays I've ever played.


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## sulphur (Jun 2, 2011)

Congrats!

That pedal gets lots of love, from what I've read.

Do they still make them?


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## hollowbody (Jan 15, 2008)

Never had the 999, but I had a Maxon AD900 for a while (which is essentially the same thing) and I loved it! If it wasn't so darned big, I'd probably still have it!


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## b-nads (Apr 9, 2010)

They still make them AFAIK, but most orders I read about seem to be coming direct from Japan. I saw a new one at Moog last spring, and the one I have still has the store tag eon it from L&M.


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## mhammer (Nov 30, 2007)

Those pedals are a weird one. They were initiated during a period when you could still get 1024-stage delay chips, but all the 4096-stage chips from Reticon had disappeared decades earlier, and Mike Matthews had pretty much bought the world's supply of Panasonic MN3005 chips to keep the Memory Man line alive. So the only way to produce delays of any appreciable length, without going digital, was to cascade a fistful of 1024-stage chips. Maxon shoved 8 such chips (equivalent to two MN3005 chips) into the AD999. Unfortunately, each chip requires separate biasing and balancing in order to get minimum noise and maximum audio quality. If you do an image search for the AD999, you'll see gutshots, and in those shots you will see _*twenty-five *_trimpots that each have to be set. The cost of the pedal is largely related to the labour required to do that.

Eventually, Coolaudio (who are either a subsidiary of Behringer or related to Behringer in some other way) re-released their copy of the MN3205 (the 4096-stage chip in the DM-3), and it became a damn sight easier to shove 8192-stages of analog delay into a box cheaply and efficiently.

There is NO advantage to doing things the way Maxon did them for the AD999. They simply did what they had to do under the circumstances, and it worked out okay for them. It's a decent analog delay, just a whole lotta work and cost to do soemthing that got easier and cheaper just a few short years later.

These days, all those 1024-stage chips are put to much better use in chorus and flanger pedals.

But congrats. A nice delay is a real joy to play through.


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## elliottmoose (Aug 20, 2012)

mhammer said:


> ... you will see _*twenty-five *_trimpots that each have to be set..


Ridiculous! But based on the clips I've heard of it, it *does *sound pretty good! Congrats on the NPD.


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## ElectricMojo (May 19, 2011)

Congrats.
The Maxon's amazing.


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## vadsy (Dec 2, 2010)

So talking analog delays and all of these vintage chips with many trimpots; do these trimpots ever need adjusting, do these pedals need maintenance? I can't see how, unless you mess with them when you shouldn't, but I have to ask.


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## hollowbody (Jan 15, 2008)

vadsy said:


> So talking analog delays and all of these vintage chips with many trimpots; do these trimpots ever need adjusting, do these pedals need maintenance? I can't see how, unless you mess with them when you shouldn't, but I have to ask.


They're unlikely to move on their own, but you have to be careful buying used cuz sometimes an ex owner may have fussed with them, which could be benign and not make much difference, or could totally ruin the pedal's ability to create repeats properly until readjusted.


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## vadsy (Dec 2, 2010)

Thanks for that, I agree. I have a friend who had an original Memory Man that needed to be sent to Mr. Davis because the previous owner messed with things that he shouldn't have touched. Worked like a charm after that! Love that sound.

Talking Maxon; how does the AD-80 fit into the chip and delay tree?


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## mhammer (Nov 30, 2007)

As far as I know from posted schematics, the AD-80 is a few hairs different from a Boss DM-2, and pretty much every other 330msec-400msec delay from that era. It uses a 4096-stage chip, good for 300-400msec delay, depending on how much bandwidth you want. It also uses a compander chip, which helps a lot in keeping noise to a minimum.

A brief digression about BBDs....

Below is the schematic for the AD-80. Just to the right of the little box that says CP-8, you will see a "bias" trimpot. Just about every analog delay pedal will have this. That trimpot takes the power supply voltage, whether battery or external, and divides it down a bit. The delay chip will need to park the audio signal on top of a DC voltage in order to work. The DC bias comes in through R112, and joins up with the audio signal to come into the delay chip at pin 7. As one rotates that trimpot, you'll pass through a zone where there is no delay sound at all, some audible delay but very distorted, then nice clean delay, distorted delay again, and finally no delay. So, the trimpot allows one to hit the sweep spot.

Since the DC bias voltage that trimpot provides is a fraction of the power supply, if you're using a 9v battery, then as the battery gets weaker, that fraction gets lower. IN a sense, the sweet spot is moving out of range. The 3rd generation of analog delay chips (those starting with MN32xxx) were redesigned to work with lower supply voltages. The 2nd generation MN3005 can work with as much as +15v. Certainly being able to run off +15v can make a bit of difference in the cleanliness of the audio signal entering the BBD, but the jury is out on whether that extra voltage improves the delay chip's sound quality in particular. People say they hear a difference, but it's not clear where the quality difference is coming from. Heck, it may even be due to the compander behaving better. 

But back to our journey. Why redesign for lower voltage? Well, in the days before people had massive pedalboards, and multi-tap power supplies, they would run stuff off batteries. And if you want that bias voltage to be reliable and valid, then the power has to be stable. By redesigning the chips to run off 5v, they could include a small 5V regulator that would drop the 9v from the battery down to +5V, and would hold it rock steady until the bettery dropped down to about 7V. And my experience is that by the time a 9v battery has dropped that far, it wouldn't have enough juice to power anything in the circuit, let alone the delay chip.

If you derive your bias voltage from that highly stable 5V, that means once you set the bias, it stays where it needs to be for a long time, unlike the MN3005 running off a 9V battery and drifting.

The schematic below shows you how some companies addressed that challenge with the earlier generation chips. In this case, the AD-80 runs off a pair of 9V batteries, giving +18V. The pedal doesn't actually _run _off 18v. In the lower left hand corner, you will see a little rectangle labelled IC105. That is one of the little regulators I mentioned earlier, except that this one keeps things at a stable +12V, until the pair of batteries drop down to around 14V. (If you connected the dots, you will have correctly come to the conclusion that these things always need at least 2V more on their input than they deliver on their output.) Since that 14V combined means the batteries have dropped down to around 7v each, we're in essentially the same position as I described earlier, except that it only requires ONE battery to power the delay with the lower-voltage chips.

In both instances, however, a regulator is used to drop a higher voltage than is actually needed, down to a usable voltage that remains stable for a longer time than if it ran directly off the battery.

Of course nowadays, with musicians generally using an external power supply, the challenge of keeping a stable bias voltage is no big deal. BUt at least you know now why these things were designed the way they were.

As for the AD-999, eight of those trimpots are for setting the individual bias of each of the 8 delay chips in there. If you're adjusting for only one, you can generally do it by ear. BUt if you have to do 8 of them, you need to use a signal generator and an oscilloscope to do each chip individually.


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## elliottmoose (Aug 20, 2012)

vadsy said:


> do these trimpots ever need adjusting, do these pedals need maintenance?


I had this exact thought after replying! good to know it won't 'drift' on its own... I have never been concerned with a sagging bias voltage, until mhammer pointed it out! Though I never use batteries, so kind of negates that whole problem.


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## mhammer (Nov 30, 2007)

Yeah, drifting bias has become much less of a concern in the last 15 years or so, as more and more players find that something like a daisy-chained wallwart or power brick is more cost effective and less exasperating than buying all those batteries, or redoing all the patch cabling to turn the batteries off.

That said, when people buy a 2nd hand delay pedal and it doesn't work, I often find that their darkest fears that maybe somehow the irreplaceable BBD has fried can be wiped away with the knowledge that bias trimpots CAN get budged from their sweet spot over the years. And very often, I find that they are able to bring such pedals back to life with a little trimpot twiddle. Not _always_, but often enough for it to be a default first strategy when troubleshooting. And since it requires no parts or even tools apart from your ears, and can't damage the circuit, it's a great default strategy to be able to turn to!


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