# Boss DM2 .vs. DM3



## tonydawe

i've got a boss dm3 and a friend has a dm2. i played one after the other one day and besides for a difference in the time i didn't notice _much_ of a difference. i read that the DM2 is supposedly warmer than the DM3. the price difference between the two is nuts. i see some DM3s on ebay selling for about $200 while the DM2 is going for upwards of $300.

whats the real difference?
why is one worth so much more than the other?

has any else been able to test out both?


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## WEEZY

From what I've read, the DM-3 was an improvement on the DM-2 back in the day. I have a DM-3 which I love, I can't imagine there's much of a difference between them, if any. "Warmer" eh? LOL.

It's probably a result of the cork-sniffers wanting the 'rarer, older' pedal for collection purposes.


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## hollowbody

WEEZY said:


> From what I've read, the DM-3 was an improvement on the DM-2 back in the day. I have a DM-3 which I love, I can't imagine there's much of a difference between them, if any. "Warmer" eh? LOL.
> 
> It's probably a result of the cork-sniffers wanting the 'rarer, older' pedal for collection purposes.


Laugh if you will, but it's true. At least in my case. I have a DM-2 and a DM-3 and I swear to you the DM-2 sounds a touch warmer. It's really a very small amount and certainly not something you'd notice in a band mix and definitely not live or anything, but it's there. My DM-2 is definitely a smidge warmer than the DM-3.


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## mhammer

I'm looking through the schematics of each, and quite frankly there is no strong design-based reason why they would sound any different. The DM-3 uses a slightly different way of adjusting delay time, but that's not part of the audio path. The DM-3 also uses a JFET as the input buffer instead of a normal bipolar transistor, like so many other Boss pedals use. That would have the effect of retaining more highs at the input, I suppose, but since all the filters in the delay path chop at the same spot they do in the DM-2, the JFET should only make a difference in the clean signal, not the delay signal.

Now, do both models use exactly the same capacitors? I have no idea. My experience is that generally when people talk about "warmth" in delays, they are talking about filtering. And it is not unreasonable to think that one kind of cap is actually closer to its stated value than another. So, while the design may be no different, and the parts listed no different, the actual measurable specs may be different.

I will also point out that the DM-2 used the venerable MN3005 for a little while before switching over the the MN3205. The 32xx series apparently clips at a somewhat lower input voltage than the MN30xx series. Perhaps more importantly, the 32xx series runs off a regulated 5vdc in many Boss pedals, while the 30xx series runs off an unregulated 9vdc. Delay chips need to be biased properly, and when the biasing is derived from an unstable source, it can drift. The 32xx series solved that issue by being able to run off a lower supply voltage, which meant that the 9v battery could be fed to a regulator to provide that stable source.

This is the long way of saying that the "warmth" could very well be due to a DM-2 being misbiased.


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## tonydawe

interesting stuff.
thanks for looking at the schematics, as well. it's interesting to know that they are basically the same pedal and i'm not out to lunch when i said i experienced a difference in the delay time. i'm sure there is some difference to how they sound, but for 95% of the people using the pedal there probably will not be much of a difference.

there wasn't for me.


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## mhammer

Far too many legends about a given model or issue are based on the comparison of ONE copy of issue X against ONE copy of issue Y. Given component tolerances, that is far too little data to go on.

I draw your attention to a quote from Mike Matthews being interviewed in a business magazine, who noted that in the 1970s you could take any 4 Big Muffs off the line of the *same issue*, and no two would sound alike.

If we want to know for certain that we are hearing true differences between models or issues, then you need to take multiple examples from each issue/model, identify what lies in common and then compare those commonalities against each other. Otherwise, it's a bit like taking me and Clara Hughes, and declaring that women are always stronger than men.


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## hollowbody

mhammer said:


> Far too many legends about a given model or issue are based on the comparison of ONE copy of issue X against ONE copy of issue Y. Given component tolerances, that is far too little data to go on.
> 
> I draw your attention to a quote from Mike Matthews being interviewed in a business magazine, who noted that in the 1970s you could take any 4 Big Muffs off the line of the *same issue*, and no two would sound alike.
> 
> If we want to know for certain that we are hearing true differences between models or issues, then you need to take multiple examples from each issue/model, identify what lies in common and then compare those commonalities against each other. Otherwise, it's a bit like taking me and Clara Hughes, and declaring that women are always stronger than men.


Well, sure Mark, but just as bad would be to take Mike's quote out of context. I've read the same article and he was talking about sourcing issues and how they couldn't always find the same resistors or capacitors, or even the same values and had to make-do with whatever was at hand, so you'd end up with Muffs with wildly different components. We're not talking about tolerance drift here, we're talking about essentially a brand-new circuit every time they put one together.

From all I've read and seen, Boss effect are much more stable in their circuitry. I guess being in Japan and it being the 80's (vs. the 70's for Mike's Muffs) made it easier for Boss to have a steady supply of components. So in a Boss pedal we're talking strictly about tolerance drift, which could certainly have an impact on tone, but shouldn't be as significant as the parts-bin mish-mash that 70's Muffs were.

Certainly, I don't have a huge collection of analog Boss delays sitting around, so my comparison would be the lone DM-2 I have to the DM-3 I have now and to the DM-3 I had in the past. The 2 DM-3s sound virtually identical to me, though I never A/B'd them. In comparison, as I mentioned, there is something in the DM-2 that lends it a warmer sound. I'm not talking a huge amount, and maybe it's my brain telling me I'm hearing it rather than my ears. I didn't pay a lot for the DM-2, so I'm not trying to justify an expense here, I was just trying to figure out which pedal would sound better for slap and which for longer delays, and my conclusion was the DM-2 sounded better for both.

On a technical note: Mark, do you think adding the dry-out changes anything? As far as I understand, signal is always fed to the dry-out. Would that simple change lead to any tonal difference in the pedal? I know in the audio community, people are encouraged to block off unused RCA in/out jacks to reduce noise, etc. but that could be more audiophile snake-oil.


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## mhammer

My use of the Matthews comment was simply to underscore that much gets made of issue-to-issue comparisons, but they are nearly always made on the basis of single copies. So, someone posts a Youtube video of a "shootout" of several different issues of a pedal, using one copy per issue or model, and then draws strong inference about their differences, and about what can *reliably* be expected from each issue. It may well be the case that the differences they note ARE reliable...or maybe not. Speaking as a scientist, the iproblem is that they don't have enough data to draw compelling inferences from.

You were right to note that Matthews was commenting to some extent on the variability in suppliers, and component values. At the same time, 5% on a resistor here, and 20% on a cap there, and pretty soon you end uop with something that has different operating parameters, even though the parts used have the values printed on them that are precisely specified in the schematic. It happens.

"_On a technical note: Mark, do you think adding the dry-out changes anything? As far as I understand, signal is always fed to the dry-out. Would that simple change lead to any tonal difference in the pedal? I know in the audio community, people are encouraged to block off unused RCA in/out jacks to reduce noise, etc. but that could be more audiophile snake-oil._"

Well, as near as I can see, from a couple of different DM-2 issues, and DM-3, the direct out in the DM-3 is sufficiently buffered that it should be absolutely fine, and also have negligible impact on the wet signal. A quirk of the DM-3 is that it not only has a JFET in the wet path for enabling/lifting the wet signal via the footswitch, but it also has a second JFET that disables the clean signal being mixed in with delay at the "main" output jack, when a plug is inserted into the direct jack. But of course, that has absolutely no bearing on the wet signal, only the dry. And if I have understood comments correctly, it is the tone of the wet signal that is at issue here.

Incidentally, while there are varying opinions about whether the MN3205 has a different sound than the MN3005, note that the DM-2 was initially made with the MN3005 and then switched to the MN3205. So those who compare DM-2 vs DM-3 should start out with some assurances that they are using either the same delay chip OR a different one, such that they can know (or at least suspect) what to attribute any possible audible differences to. Note, as wel, that there are three internal trimpots, two of which are critical to sonic quality, and one of which is critical to delay range. I am sure Boss does an admirable job setting them right, but throw 20 years of being kicked around on top of that, and there may be some drift involved that first needs to be ruled out.

As for any need to short out unused jacks, in this case that is contr-indicated since shorting out the direct jack cancels the clean sound from the other jack. besides, BBD-based pedals have so many internal sources of noise that externally-induced ones pale in comparison. It's like having a grizzly bear running loose in your house, and being worried about closing the screen windows so the flies don't come in.

I will simply add here that they are both fine pedals that owners swear by. I made myself a DM-3 clone, and it sounds pretty good for what it does, though clearly it is limited in what it does.


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## allthumbs56

I'll weigh in. I've owned both and I will say that I really preferred the DM-2 to the DM-3. My brain told me they were the same, and I wanted to believe that because of the price difference but there was a subtle but significant difference that went beyond the buffer and the "backwards" knob. I can't begin to explain tha difference but to my ears it was there.

In the end, I sold the DM-2 for a decent profit (I'd bought it at a pawn shop for $25) and the DM-3 because it didn't do anything for me that I couldn't get out of other delays (and I made a few bucks on that one too.

If either crossed my path for a reasonable price today I'd pick it up though.


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## mhammer

Ah, but which BBD chip did it use?


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## hollowbody

mhammer said:


> Incidentally, while there are varying opinions about whether the MN3205 has a different sound than the MN3005, note that the DM-2 was initially made with the MN3005 and then switched to the MN3205. So those who compare DM-2 vs DM-3 should start out with some assurances that they are using either the same delay chip OR a different one, such that they can know (or at least suspect) what to attribute any possible audible differences to. Note, as wel, that there are three internal trimpots, two of which are critical to sonic quality, and one of which is critical to delay range. I am sure Boss does an admirable job setting them right, but throw 20 years of being kicked around on top of that, and there may be some drift involved that first needs to be ruled out..





mhammer said:


> Ah, but which BBD chip did it use?


My DM-2 uses the MN3005 chip, so there is basis for a slight difference.

Regarding the trimpots, I've always been concerned with how representative my pedal are of a stock, fresh-from-factory pedal. Obviously, ignoring the fact that component values can drift a bit, I am concerned that one of they previous owners may have fiddled with one or more of the trimpots. My pedals both sound good (and so did the other DM-3 I previously owned), and there are no glaring delay-time oddities, but that doesn't mean they haven't been messed with.

Mark, is there a way to check the settings? Obviously, Boss (and other mfgs) set their pedals a certain way from the factory, but can they be adjusted by ear, or visually (ie. a certain o'clock on the pot) or do you need testing equipment to measure?

Again, I think my pedals both sound great, but you know how it is with this stuff


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## mhammer

hollowbody said:


> My DM-2 uses the MN3005 chip, so there is basis for a slight difference.
> 
> Regarding the trimpots, I've always been concerned with how representative my pedal are of a stock, fresh-from-factory pedal. Obviously, ignoring the fact that component values can drift a bit, I am concerned that one of they previous owners may have fiddled with one or more of the trimpots. My pedals both sound good (and so did the other DM-3 I previously owned), and there are no glaring delay-time oddities, but that doesn't mean they haven't been messed with.
> 
> Mark, is there a way to check the settings? Obviously, Boss (and other mfgs) set their pedals a certain way from the factory, but can they be adjusted by ear, or visually (ie. a certain o'clock on the pot) or do you need testing equipment to measure?
> 
> Again, I think my pedals both sound great, but you know how it is with this stuff


One of the trimpots - VR1, found between the MN3005 and the corner of the board - sets input bias to the delay chip. When the bias is bang on, the delay sound is at maximum volume and clean. A little higher or lower, and the sound becomes more distorted, and less than max volue possible. Higher or lower still and the delay sound disappears.

It CAN be adjusted by ear but the optimal conditions are that you are listening only to the delay sound. If it was a DM-3, you could simply stick an unconnected patch cord into the "direct" jack to cancel the clean signal from the other output. With the DM-2, you can't do this, so you need to physically disable the clean signal another way.

R32 is a 47k resistor (yellow-purple-orange) that mixes the clean signal in with the delay. It can be found just a bit to the left of the 4558 chip nearest the connecting wires. Unsolder either end of that, and you should hear only delay signal. Obviously when the pedal is in bypass, you won't hear *anything*, since bypass only cancels the wet and does nothing to the dry.

The second trimpot associated with the delay chip is the clock cancel trimpot, VR2, situated to the left of the delay chip near the middle bottom of the board. All delay lines alternate between two series of miniature sample&hold units. they are actuated by complementary clock pulses - tick and tock. When the two outputs are in perfect balance, the tick and tock cancel each other out and negligible clock noise is heard. As well, since it adjusts the amplitude of each output, a final mixed delay output which combines tick and tock outputs in equal proportion will more faithfully represent the original signal.

Again, this can be adjusted by ear, though the result is perhaps less obvious than the asdjustment of VR, since nothing disappears; it only gets better or worse. Obviously, to assess this by ear, you need to have not only delay-only output, but quiet so that you can here what you are listening for.

Adjustment of the first trimpot requires you to feed in a guitar signal to detect optimal adjustment. Tweaking the second one does not require an external signal, since what you are listening for is the absence of an internal signal: the clock. That clock pulse will be most audible when it is set to the longest delay time (slowest/lowest clock frequency). I recommend adjusting it via headphones if you have an amp with a headphone output. That way you can be sure you are hearing the clock whine and not the furnace, the fluorescent fixture, or somebody's cellphone. Just adjust it until you hear the least whine possible. It should be somewhere near the midpoint of rotation.

Let me emphasize that NEITHER OF THESE ADJUSTMENTS RISKS THE PEDAL. They may well bugger up the sound quality if misadjusted, but neither of them will fry a hard-to-replace delay chip.

the third trimpot, we can leave as is, since it merely adjusts the delay range so that you got an optimal balance between maximum delay and usable bandwidth.


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