# Thoughts on MXR Distortion+ Vintage vs. Reissue



## hollowbody

I've been wanting a heavier dirt pedal to replace my small-box Rat that I traded a while back and I thought I would give the Dist+ a try. 

Has anyone out there A/B'd an older version alongside the newer ones? 
Is there a difference? 
Is it as significant as the Dynacomp?

The reissues are usually pretty cheap, but I don't want to spring for a pedal that I'm going to think is crud.


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## mhammer

I have probably typed more words about the Dist+ in my lifetime than the sum total of everything you've seen posted from me on this forum. So here is the scoop on the D+

1) Its "natural" sound is a product of a number of things, one of which is the use of an inferior op-amp: the LM741. Those of us who have experimented with the unit find that it is essentially impossible to get an actual "clean" sound out of the D+, even when the clipping diodes are completely removed from the circuit and the gain is kept very modest. this would seem to be a product of the manner in which the chip is deliberately "starved" for current. If the re-issue uses a chip which is not so similarly "starved", the behaviour is likely to be a bit different. Note that because the original results in some chip-based distortion, adding gain and clipping diodes on top of that yields a form of "double clipping". Not quite to the extent that the Big Muff double clips, but double clipping nonetheless.

2) The original used germanium diodes, which will produce more clipping for the same amount of input signal, since they have a lower "breaking point" or forward voltage. But that lower ceiling also means that the output is not substantial. If one is expecting to use the pedal to push an amp hard, be forewarned that you really don't get anything terribly substantial from the pedal unless gain and volume are dimed. Anything less than max gain/clipping, and you'll be very hard-pressed to hurt the input of your amp unless the output level is up full and you have some sort of clean booster after the D+. It's just not that loud on its own. That does not make itan inferior design, but it may not suit your needs.

3) Goodness gracious this thing is shrill. If your guitar tone is turned down, and the amp's treble is tamed, you can afford to turn the pedal on, but if you expect to go from a clean crisp rhythm sound to an overdriven sound with this pedal, be forewarned that you will find yourself racing for the EQ quickly, since it doesn't have any treble taming capabilities on its own. That can be easily fixed in a nonintrusive way without impacting on resale value, and I'd be happy to walk you through how to do it. Just know that the pedal assumes you will fix its' shortcomings elsewhere.

4) The Rat has a maximum gain in the thousands, while the D+ has a maximum gain of 213. I don't know how you'd get a more distorted sound from the D+ than you would from the Rat. When it comes to clipping, the Rat kicks the D+'s arse. The difference is that the Rat includes the sort of filtering I said was missing from the D+, so it sounds smoother than it really is.

I've made myself a couple of D+ units, and a couple of Rats, both with "original chips". They both have their charms. Stock, however, I find more of usefulness in the Rat, even though the D+ can be modded up the wazoo for some pleasing tones. Note that the DOD250 Overdrive and the DOD YGM308 pedals are but a few component values away from the D+.


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## hollowbody

Mark, thanks again for one of your patented above-and-beyond responses. 

I don't have any direct experience with the D+, but have heard that several people whose tone I enjoy have used the pedal with success (which is always a bad reason to purchase a pedal, but at least I'm admitting to it!). The artists I'm thinking of specifically are Bruce Springsteen in the 70's and Greg Keelor.

Given your explanation of the circuit and it's potential drawbacks, I think I might be better served to find another small-box Rat. Maybe if I can find a D+ for a great price, I'll give it a whirl.


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## mhammer

It IS an interesting pedal to mod, but if modding is not your forté, then yeah another Rat might be an idea.

And thanks for the nod.


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## Kestral

> 1) Its "natural" sound is a product of a number of things, one of which is the use of an inferior op-amp: the LM741.


That's interesting, the LM741 also happens to be the "highly-valued" chip that makes the gray box DOD 250 overdrive pedals worth almost as much as vintage TS-808's.

btw, I should mention I'm not mentioning this as a flame, I'm mentioning this because I know very little about chips and opamps and truly find it interesting that one man's JRC4558 is another man's LM741.

As for my own 2 cents, I own an original vintage script logo Dyna Comp and the reissue is nowhere near the original. I've A/B'ed the vintage script logo Phase 90 vs. the reissue and same thing.

As for the Distortion+, I have A/B'ed the script logo version (not the block logo vintage) vs. the reissue and once again, completely different realm, the vitnage imo won hands down.

For the record my current dirt pedal is an MXR Distortion II, I seem to recall opening it quite a few year back and I seem to recall seeing two of those JRC4558 chips in it.


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## hollowbody

Kestral said:


> As for my own 2 cents, I own an original vintage script logo Dyna Comp and the reissue is nowhere near the original. I've A/B'ed the vintage script logo Phase 90 vs. the reissue and same thing.
> 
> As for the Distortion+, I have A/B'ed the script logo version (not the block logo vintage) vs. the reissue and once again, completely different realm, the vitnage imo won hands down.


Yeah, I experienced the same sort of thing with two Dynacomps, but have never had any time with any Distortion+. I don't really want to drop a bunch of cash on a vintage version of a pedal I may not dig very much (especially when there _is_ something out there that I _know_ I will enjoy). I asked specifically because I wanted to maybe give the reissue a shot first to see if I liked it if it was sonically in the same camp as the original, but if it's that different, it may not be an accurate representation. Oh well, back to the drawing board.

Anyone out there have clips of the two A/B'd? I'm off to scour youtube


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## mhammer

For my part, many of the original-vs-reissue comparisons one hears about, while sincere, are poorly grounded. The thing is that a lot of these older pedals used components with wide tolerances. When people compare old vs reissue, they generally compare only one of each, naively assuming that all other vintage pedals of that type would sound exactly the same, and attributing any audible differences to "old vs reissue".

While it IS quite possible that some design changes have been implemented since early issues that might have invited some undesirable tonal changes in an attempt to improve some aspect of design efficiency (e.g., battery life), the problem is that one really needs to have multiple examples of each type on hand to be able to say with some confidence that the audible differences are due to* issue* and not simply the individual pedal and its idiosyncracies. Again, I don't deny that people hear something truly different. The problem is identifying the basis for that heard difference. Heck, even Mike Matthews himself has publically declared that you could take 4 early issue Big Muff pedals from the same batch, and they would all sound different from each other, simply because they exerted little control over theparts used and the parts had wide tolerances.

As for the LM741 vs the various 4558s (LM, NJM, JRC, XR, RA, etc), I suspect that similar behaviour could be evoked from 4558s as well, were someone to invest the time (which I haven't). I'm somewhat convinced the secret to never-clean 741s is in the low biasing current, which could also be achieved in a 4558, though with other component values since the 4558's biasing needs are different. DOD eventually chose to use a 4558, provide normal biasing and leave the heavy lifting to the clipping diodes. the LM741 itself is not that special, though. It is the operating context it finds itself in that matters.

I have a clip somewhere that I made of a homebrew Dist+ with an assortment of different op-amps being used, including a Dave Barber-inspired "parallel pair" of two stacked NE5534 chips. There are audible differences, even though nothing in the rest of the circuit or settings was changed. None of the tones is "bad", but different ones suit different tastes. The 741 had a bit more buzz to it.


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## hollowbody

Just to resurrect this thread briefly, I got my hands on a 1981 Block Logo Distortion+ that I got in a trade. I wasn't really looking for this pedal anymore, but thought I'd give it a go, since I got good value on it.

Mark, you're right about the brightness of the pedal. That initially turned me away back in March, but my rig is quite different now. 

I have a LP now and am running it through a Marshall JTM45, which is known as a bass heavy amp. Whereas before, I was planning on using the Dist+ as my heavy lifting pedal to go from clean to driven sounds, now I'm using it as my solo boost and I find that I like the trebly grit it adds. I've only had it for a few hours so far, so I'm far from a final verdict, but so far so good.

Mark, what needs to be done to the circuit to increase output a bit? Not a large amount, just a tad.


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## keto

I'm sure Mark will be along with a coherent and technical reply shortly  I just built the BYOC 250+, to Dist+ specs. I read a thread on their forums whereby changing (lowering from iirc 47k to 4.7k) a resistor value resulted in higher output - so I built it that way, and it has plenty of output.


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## hollowbody

keto said:


> I'm sure Mark will be along with a coherent and technical reply shortly  I just built the BYOC 250+, to Dist+ specs. I read a thread on their forums whereby changing (lowering from iirc 47k to 4.7k) a resistor value resulted in higher output - so I built it that way, and it has plenty of output.


Sounds pretty straightforward. The pedal I got is in pretty rough shape and someone has drilled a hole in the side to be able to pull the 9v clip through, or to feed an adapter through I guess, so I'm not too concerned about keeping it "stock". 

I think if I could tame some of the fizz at the top end and add some output, it would be a pretty sweet pedal. Right now I'm using it to boost for solos on an already driven Marshall, so the output is maxed and the distortion is set to roughly 10 o'clock.


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## mhammer

The germanium diodes in there will produce more clipping, since their threshold is fairly low (generally clipping at around 190-250mv), but a simple pair of silicon diodes will get you nice sturdy crunch at much higher level (generally clipping at 490-560mv). Since the clipping threshold is higher, you don't have to do anything to the gain, since more of the inherent gain will be "let out".

The fizz can be easily tamed by placing a 47-68pf cap across the 1M feedback resistor that connects pins 2 and 6 on the 741 chip. 47pf will produce a rolloff starting around 3.3khz. That may sound low, but the rolloff is shallow, so you'll lose some fizz but not the treble bite. You can round it off a little more by sticking a .0022uf (2200pf) in parallel with the existing .001uf cap that parallels the diodes.

Those 3 changes will get you noticeably more volume and the sort of tone that won't send you scrambling for the guitar tone control (quite as much) every time you turn the pedal on.

Finally, some issues of the Dist+ used volume pots which were far too low a value. The output pot should be at least 50k, and even 100k if you can swing it. That can also increase output levels so that you don't have to dime it to hear it.


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## Wild Bill

I don't have much experience with pedals. Certainly not as much as guys like Mark! However, I DO know a lot about IC's!

IC's are a mass produced item. It's like making nails. You have to run 10,000 pcs just to grease the machines!

Over the years manufacturing tolerances got better and better. This made op amps, especially those used in audio, more and more linear, or "hifi".

Of course, when they are deliberately asked for distortion, as with a guitar pedal, it's a whole new world! The best example was when Ibanez brought back the TS808 series of Tube Screamers. Everything was exactly the same as the original. Even some of the assemblers were the same guys! Yet the re-issues didn't sound as good as the original ones from 10 years earlier.

It took a while before they figured it out. It was the op amp! The JC4558 dual op amp used in the Tube Screamer had been improved over those years. It didn't distort as easily or exactly the same. This gave the pedal a different sound.

All those vintage pedals came out in the early to mid 1970's. So did those op amps they used inside, like the LM741 and others! It was the invention of those op amps that allowed the invention of the pedals. Especially since companies like National Semiconductor were full of guitar players! It was no coincidence that National Semiconductor invented many specialty IC's for music effects circuits, which they published in their data books.

Getting back to the Tube Screamer, Ibanez had a problem. There's no way they could get some factory to make the JC4558 the old way. It would have meant finding the old machines in the landfill sites and setting them up again. At that point, they would have had to give the factory an order for MILLIONS to make it worth their while! After all, in production volumes the IC cost maybe 15 cents. It just couldn't happen.

So they simply changed their marketing strategy. They didn't claim anymore that the new ones sounded exactly the same. They just said they sounded good!

Some unscrupulous sources engaged in a bit of counterfeiting. An IC factory wouldn't make just a few thousand IC's with the original "bad" old specs. However, for just a few pennies they would cheerfully ink the old part number on some NEW IC's!

Then you'd hear some hinky story that someone discovered some old versions of the JC4558 gathering dust on some electronic distributor's warehouse shelf. If you've ever worked in such a warehouse you'd know right away that this story is totally bogus! Inventory turns over many times a year for common items like these op amps. The chances of any being left on the shelf for 10 years is slimmer than the odds of finding an honest politician, or of getting someone to pay ME for playing guitar!

I've been in the habit for some years of keeping an eye out when I visit thrift shops and yard sales for old electronics from the early 70's, especially telephone answering machines. If the price is only a dollar or two I pick them up. Maybe one time in every four or five I find an original JC4558 inside! I carefully unsolder it and put it away. If someone brings me a new Tube Screamer I can substitute the old chip for him, giving him the original sound. As a bonus, I use an IC socket, so that he can easily experiment with other dual op amps that have the same pinout, to hear the different sounds.

While I've never done this for the LM741 with the MXR + I would expect that the same factors probably apply when trying to capture the vintage sound with a new DIY pedal. Perhaps this story will help someone nail the original tone.

:food-smiley-004:


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## mhammer

Indeed, there are all manner of things you can find at the curb on garbage day which likely contain some older-issue chips, and one is recommended to salvage them and hunt for goodies. A few caveats, though:

1) It can take more heat to unsolder a chip than to solder it in, so there is a risk of heat-related damage unless one is skilled at removing them. There is also the risk of breaking pins, etc.

2) Older chips are not necessarily "better" chips and will not automatically improve the tone of whatever you stick them in. In the case of Tube Screamers, the value of the older chip would appear to be in the way that it interacts with diodes in its feedback loop. In contrast, there are a ton of pedals in which no such interaction takes place, and a "vintage" JRC4558 holds no advantage over a shiny new TL072 or BA5218 or LM4560 or any of a thousand other numbers. I'm not dissing older chips, merely noting that "it depends".

The DOD250 has had several issues but none of them appear to depend on the 741 as much as the Distortion+ did/does. I still maintain that it is that quirky biasing arrangement in the D+ that takes advantage of the 741's properties to get a sound that never ever cleans up, even with gain low and no clipping diodes in place.


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## paraedolia

I'd get one of these








before a regular Dunlop RI.


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## mhammer

I've seen the ads, and quite frankly, I have VERY strong doubts as to whether there is anything distinctive about them. It is possible for anyone to perfectly replicate all issues of the Dist+. It may be a well-built pedal, and the blue LED against a black background is nicely visible across the stage, for those who need such an advantage, but when it comes to distortions, anyone claiming some sort of proprietary knowledge about this one is a bit like someone claiming they know how to make toast in a way that nobody else can.


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## mrfiftyfour

Thanks for the informative thread.
I've been using the Dist+ for a while now and I agree about the pedal's weaknesses.
However, there are characteristics about the tone that I love and am determined to mod the pedal to bring out what I believe to be it's full potential.
I've checked out some sites on the matter:
http://www.ultimateguitartone.com/effect-mods/mxr-distortion-mods-tone-and-distortion-2.html
http://www.diystompboxes.com/pedals/mods.html
http://www.premierguitar.com/Magazine/Issue/2008/Dec/MXR_Distortion_Plus_Mods.aspx
When I went to the electronic supply shop to pick up parts to try out the mods outlined in the links provided above, I had problems picking out parts off the shelf that matched the numbers I got off the sites. Even the dude working there wasn't to much help when I showed him my shopping list.
Anyhoo...
in the C4 I swapped out for this:







[/IMG]
Original component on the left.







[/IMG]
I loved the result.
Next, I tried to swap out the D1 and D2 diodes with these:







[/IMG]
I didn't like this, and put the originals back in.
I bought this as well:







[/IMG]
But I can't remember what I was supposed to do with it!
I'm trying to make the pedal warmer and fuller sounding but I don't want to tame the fuzz, just the fizz.
Any pointers
Thanks for reading


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## mhammer

Okay, glad one of the suggested mods was to your satisfaction. 

Seems to me your attempt at the diode mod was misinformed somehow. The replacements should have been other diodes; specifically 1N914 (available at any Source store). What the picture shows is 2k7 resistors. This will not result in any clipping, but will actually reduce your overall output from the pedal too. Use diodes, and you'll like the outcome.

As near as I can tell, the 223 (cap may have been to place i parallel with the diodes, possibly in place of the white cap on the right side of the picture of the board (whose value I can't make out clearly, but is definitely less than the ceramic cap). Find the pads where the white cap is connected on the solder side, and temporarily tack on the ceramic unit, and see if you like it. The sound should be warmer, as if you had a tone control and had turned it down a bit.


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## mhammer

mistaken duplicate message


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