I built an mxr clone, used a 741 (from rat shack), sounds fantastic! I'm a picky mo-fo when it comes to distortion. Why does the 741 have such a bad reputation???
Is it just one of those cases of contempt prior to investigation in the FX world???
matt
The is noting 'wrong' with a LM741. It's just that it's specifications (noise, offset voltage, distortion, frequency response) is exceeded by many more modern chips.
In most circuits, the modern chip will give a result that is no worse, and may be 'better' in some way. Or not. Occasionally of course, the 'improved' chip will oscillate & wail like a banshee :icon_mad: :icon_redface:
Aother point: a LM741 made today by national semiconductor is made from better materials, in a cleaner room, and probably to a slightly 'improved' layout, compared tot he first one that rolled off the line a couple of decades ago.
I am a BIG fan of the 741 especially in the OD250, it sounds fantastic!
Yes I agree the 741 in the 250 does sound great. It's the pick of choice for most of my recorded material.
I am a big fan of the 741 OD250 too.
I've used the 741 in a couple of things, most recently a few line buffers. Works great.
hmmm...I guess sometimes you just have to use the most complicated testing device on earth to judge something....your ears!!!
thanks guys,
matt
Yep, Peter makes a good point. I came to that same conclusion as well. A 20 year old opamp won't have the same quality and be manufactured to the same tolerances as a new one, and that's why I have no problem using a new manufacture 741 in a build. I only worry about it if limiting noise is a big concern.
This is a bit like saying "Everyone keeps going on about how great knives and forks are, and how lousy and dull spoons are. Well, I tried eating my cereal this morning with a knife and fork, and let me tell you the spoon kicked their asses around the block and back! Spoons rock!"
The OD250 and Dist+ are essentially designed around the 741. No small wonder it sounds fine in there. Not a whole lot of other applications where it will sound better than other contenders, though. Build a phaser with one and I can pretty much guarantee you'll diss it. Build a compressor with one, and you'll be screaming "Who do I have to sleep with to get this thing out of here!".
I wasn't aware that the 250 was designed around the 741. Shows U how much I know. Question, lets say a project you're building requires a TL072 duel opamp or similar and instead I tried using two 741's it wouldn't be a very good idea?
Quote from: oldrocker on June 23, 2006, 02:00:33 PM
I wasn't aware that the 250 was designed around the 741. Shows U how much I know. Question, lets say a project you're building requires a TL072 duel opamp or similar and instead I tried using two 741's it wouldn't be a very good idea? Just wondering about that.
Quote from: oldrocker on June 23, 2006, 02:03:15 PM
I wasn't aware that the 250 was designed around the 741. Shows U how much I know. Question, lets say a project you're building requires a TL072 duel opamp or similar and instead I tried using two 741's it wouldn't be a very good idea? Just wondering about that.
Yes and no. Individual tastes can vary. In the case of the OD250 and Dist+, users who though they might be able to score a two-fer-one by installing a diode-lift switch were surprised to find that the thing distorted even without diodes. So, even though it doesn't look like a double clipper
on paper, in reality it sort of was - what you feed to the diodes is already clipped.
Since the pedal is going to shave off both the bass
and the treble eventually, then there is no real need to have a high input impedance to try and savour every last herz of bandwidth. Since the thing is not ever going to be used clean, then there is no need to have something that handles large input signal or signal swings easily. But both WILL work with other op-amps (mine uses a piggybacked pair of 5534 chips but sometimes a 741). They just won't sound exactly the same.
If a project specifically asks for a bifet op-amp, though, unless the designer has made some sort of error or is just going on the basis of what they heard about op-amps, if it says it needs a bifet then you should probably use some sort of high input impedance chip. You could use a TL062 or 82 for a TL072, or you could use a CA3240 (assuming you can find them), or an op-275 (if you can afford them), or an LF353, or any of a bunch of FET-input alternatives. Some things may vary (e.g., an 062 is a little noisier than an 072), but you will at least have nailed some particular design parameter that the designer felt was important in proper functioning.
Keep in mind that since stompboxes and op-amps were introduced, there have been historical changes in the quality and introduction of certain op-amp types. What that means is that there are plenty of circuits where one op-amp is listed but since the circuit was designed other op-amps have since come to outperform it on spec, or perhaps the price difference between what was used then and what is available now has come way way down. For instance, when Craig Anderton published Electronic Projects for Musicians, the XR/LM4739 dual op amp had pretty good specs in comparison, was not dramatically costlier than other chips, was not harder to find than other chips, and was cheaper than any FET-based op-amps. So Craig used it. Has it been outstripped by other chips that cost a fraction of what the 4739 did then (and especially now)? You betcha. A person would be a fool to perseverate over getting a 4739 to make one of those projects instead of simply springing for a 5532 or TL072.
When it comes to distortion, though, pretty much all bets and advisories are off. Why? Because making distortion is often about the weaknesses of a semiconductor, not its strengths, and because distortion is very much a matter of ears and taste. For instance, you will not see the LM308 used very much in audio products or most pedals. But you will find one in a Rat. Why? Because of the limitations of the 308 under the conditions it is being used with.
Quote from: Mark Hammer on June 23, 2006, 01:31:41 PM
This is a bit like saying "Everyone keeps going on about how great knives and forks are, and how lousy and dull spoons are. Well, I tried eating my cereal this morning with a knife and fork, and let me tell you the spoon kicked their asses around the block and back! Spoons rock!"
Thanks for a good chuckle at a point in my day where is was sorely required. :icon_biggrin:
I once fixed an old + for a friend that is a bass player. Stock it sounded great with his Jbass. Same thing with a TS stock they can sound good with a bass. don't change the input or output caps. Give it a try. Now you must think about how it will sound in a mix not as it sounds alone.
The next set in building stuff is learning how stuff sits in a mix be it on stage on a CD. Effect petals and microphones and preamps and compressors.................
That's what I used for my Tube Reamer version 1, and it sounds perfect. It's an old 1974 model...
(http://www.gtechblues.com/images/TubeReamer1.jpg)
Gilles
It's interesting that people are saying the 741 sounds better in an overdrive.
Three reasons why this might be so:
1. the 741 runs out of high frequency gain when it is in a high-gain circuit like this (so, you are getting a free hidden high frequency roll-off).
2. might be acting as a slew-rate limiter, again smoothng things out
3. (less likely but possible) when it is momentarily saturated (from running out of gain) the protection diodes on the inputs to the 741 might do some waveshaping.
It all goes to show, that pedals (like most things in life) are more complicated than one might think.
Two little tidbits of info here:
One, gus I agree with you, living room vs. stage or studio are two totally different worlds. I've gotten to where I don't even bother getting to jazzed about an effect until I've had a couple full volume rehearsals with it. That's always what separates the "man" pedals from the "boy" pedals so to speak. Also, if you're a fender amp guy (in my case a '63 tremolux) all bet's are off. fender amps are very picky about what they like and don't like. Marshals, vox's, and many others are much more forgiving (of course this is just MHO).
two, don't be afraid to try the "stock" version of a pedal before you go into mod-land. at least that way you know what your modding, and you may just find you don't need to mod at all...
Three (i know, i said 2), the layout for the MXR on dragonfly has an error. I'm not complaining, i appreciate the time it takes to do the layout, put it on the site etc. But just be aware of it (I noted it in the gallery) if you attempt it.
thanks,
matt
741 in DIST+ ;D
At line level I'm sure that an average pair of ears, which have been subjected to loud Marshall amps for a few years, could not tell the difference in a unit using 741s and another using OPA2604s (or whatever) - mind you they would not agree over at Prodegy Pro!!!!!
Hi
I agree with the sentiment of:
Quote2. might be acting as a slew-rate limiter, again smoothng things out
RG has said that better chips might have "gracefulness" in response and recovery, which I think is a similar thought to the one above.
I've built a few ideal diode circuits, where op-amp gain is varying wildly during the course of a single waveform (or half a waveform, to be exact). In this case, where grace under pressure is also desirable, a 741 seems to produce a BETTER waveform than chips such as the TL071.
The main disadvantage that I see in 741s is that for audio signals at high gain, the noise of a 741 (or 4558) becomes a real nuisance.
cheers
Quote from: csmatt45 on June 24, 2006, 12:46:47 AM
don't be afraid to try the "stock" version of a pedal before you go into mod-land. at least that way you know what your modding, and you may just find you don't need to mod at all...
Amen to that.
I've built more than a few circuits that sounded fantastic in the stock form only to sound like crap modded.
Mods aren't always "good".
There's and old saying that goes;
"One man's garbage is another man's Gold"
Of course, the other old saying that comes to mind is;
"You can't make chicken salad out of chicken sh*t!"
I'm done now.......thank you!
Quote from: Mark Hammer on June 23, 2006, 02:46:44 PM
In the case of the OD250 and Dist+, users who though they might be able to score a two-fer-one by installing a diode-lift switch were surprised to find that the thing distorted even without diodes. So, even though it doesn't look like a double clipper on paper, in reality it sort of was - what you feed to the diodes is already clipped.
Well that explains a lot, heh. I was fiddling with a 741 awhile back and I couldn't get it to clean up. I checked bias, this that, and the other thing, but it distorted no matter what.
I guess it's kinda like the 386 in that you can't expect a ton of cleanliness out of it.
I guess the other thing to note about the 741, is that the design is freaking
ancient. Isn't it like the 2nd opamp ever made?
Quote from: markm on June 24, 2006, 08:12:47 AM
"One man's garbage is another man's Gold"
Of course, the other old saying that comes to mind is;
"You can't make chicken salad out of chicken sh*t!"
As my Grandfather used to say,
"You can polish a turd all day long - and IF you're really, really, really lucky - you just might end up with shiney sh*t"
And I agree, spoons DO rock!
Quote from: Mark Hammer on June 23, 2006, 01:31:41 PM
Build a phaser with one [741] and I can pretty much guarantee you'll diss it.
I've built several phasers with 741s (4741s in fact) and they sound delightful IMHO.
After trying diode to ground clippers using non741 opamps, like TL082/072 etc.
I figure that the sound compression/distortion of clipping diodes is 'one thing' and tends to sound a bit 'sterile' probably because it's just a ceiling being put on a waveform.
With the 741 in there the sound becomes more complex, probably because...and I say probably cause I'm just type/ramblin here...the 741 has a tough time replicating exactly the higher amplitude transients of input signal, shaping the EQ with every attack, adding 'anomolies' that for HiFi would be a bane, but for distortion adds 'character' or 'dynamic' or some other '1/2way descriptive' terms.
Quote from: Mark Hammer on June 23, 2006, 01:31:41 PM
This is a bit like saying "Everyone keeps going on about how great knives and forks are, and how lousy and dull spoons are. Well, I tried eating my cereal this morning with a knife and fork, and let me tell you the spoon kicked their asses around the block and back! Spoons rock!"
The OD250 and Dist+ are essentially designed around the 741. No small wonder it sounds fine in there. Not a whole lot of other applications where it will sound better than other contenders, though. Build a phaser with one and I can pretty much guarantee you'll diss it. Build a compressor with one, and you'll be screaming "Who do I have to sleep with to get this thing out of here!".
And then you have chopsticks................................
Quote from: stumper1 on June 25, 2006, 12:07:31 AM
And I agree, spoons DO rock!
Witness Artis the Spoonman: (http://www.photos.musicfestivalahead.com/jim+artis%202.JPG) (same guy the Soundgarden song is about)
One heck of a nice guy and he absolutely rocks!
Does he have any N.O.S. teak in those spoons, or is it all JRC4558D?
it's all about slew rates and so on right? Like the 741 has a really low slew rate giving it its characteristics etc
I think so.
I'd bet it's like the LM308 and it's slew rate is the reason the Rat sounds like it does.
At least, in theory.
I have no first hand experience to share about the Rat.
Quote from: Dave Eason on June 25, 2006, 04:32:33 PM
it's all about slew rates and so on right? Like the 741 has a really low slew rate giving it its characteristics etc
Not exactly. Slew rate is a measure of how quickly the voltage can swing. Think of it like the 100 metre event for chips: how fast can you sprint? But it is also a measure of usable bandwidth as well. Most chips, if the gain demands imposed on them are modest, have way more than enough usable bandwidth for any audio purpose you'd care to mention. As the gain of the circuit goes up, however, the amount of usable bandwidth goes down. As if the chip is saying "Well, buddy, I can run THAT fast for about THAT distance, but after that, I'm likely to be too pooped to continue." So, the more gain you aim for, which is tantamount to saying the bigger a voltage swing you ask the chip to engage in, the smaller a portion of the measurable spectrum it will be able to do that for.
In most instances, 0.5 to 1v/usec provides as much slew rate as we here would need from an op-amp for our guitar-related needs. Anything more than 2v/usec is just gilding the lily (an English expression for taking something already perfect and trying to make it seem better). The Rat represents a special case, however, where the gain is so excessive (several thousand at max gain setting), that the slew rate limitations of the chip, both naturally and altered by the 30pf compensation cap, make it do some strange things. To the best of my knowledge, there are no 741-based circuits that aim for the same sort of weirdness.
Quote from: Mark Hammer on June 26, 2006, 09:38:18 AM
, where the gain is so excessive (several thousand at max gain setting), that the slew rate limitations of the chip, both naturally and altered by the 30pf compensation cap, make it do some strange things.
Here's a good bit of news.. you can easily get adjustable caps fro 30pf! Go for it guys!
(in fact there are ones from pocket transistor radios that go like 5 to 250 pf or so, quite small).
I've never tried an "adjustable" cap .... seems like a fine idea and would userp any socketed "cap swopping"
too :D
Can you get say 1n to 15n adjustable ?
MM.
741s are also a teensy bit current-hungry (for a single op-amp device.)
Quote from: Paul Perry (Frostwave) on June 27, 2006, 04:28:57 AM
Here's a good bit of news.. you can easily get adjustable caps fro 30pf! Go for it guys!
(in fact there are ones from pocket transistor radios that go like 5 to 250 pf or so, quite small).
Outstanding call Paul.
The RAT I keep meaning to build just got an extra knob.
Adjustable compensation cap, nice.
I was messing around with my RAT and took out the clipping diodes and noticed: that the sound is allready a bit distorted without them
is this the opamp (I think that I measured the bias voltage at the input of the opamp as 1/4 of the battery instead of 1/2 too, on both of the Rats I have made) breaking up or was it just my amps clean channel breaking up under all the gain?
ICs are not good or bad, the challenge is to find the right IC for a given circuit or design. The OD-250 and some other FX are designed around the 741 and the values are taken from the sample circuits in the datasheet. The 741 or 4558D are very nice sounding ICs for OD or distortion FX, but I would not use them in HiFi stuff.
You can put any 308 subtitute in a RAT, there will only a minor difference in the sound, same in the Moongoose.
Landgraff uses a 100p as compensation cap in his RAT clone, but I can't hear a big difference between 30p or 100p.
IBZ's Fat Cat has the same sound as the RAT and has a 5534 w much higher slew rate in it with a slightly altered input circuit.
JHS
I think the Dist +/Rat type circuits should be conceptualized as 2 stage distortions. As the signal/gain increases the clipping diodes distort first, and then the op amp gets into the act at higher settings. At lower distortion levels, there may not be as much difference (when the op amp isn't driven beyond it's design capabilities) between op amps, since the diodes are doing most of the distorting (the diode configuration should provide most of the distortion character). As the distortion increases, the op amp contibutes a larger percertage of the distortion. :icon_twisted:
When tweaking my old PV Special which has a similar distortion set up, the 4558 sounded good, but the OP275 had more clarity and detail and didn't get as garbled under heavy distortion, so ... :icon_cool:
I think the Dist +/Rat type circuits should be conceptualized as 2 stage distortiongs.
The 741 seems clearly to do a great job compared to 'higher performance' chips for getting 'first and second' stage distortions in the Dist+. A very noticable, different flavor, more complex.
Quote from: Mark Hammer on June 26, 2006, 09:38:18 AM
Not exactly. Slew rate is a measure of how quickly the voltage can swing. Think of it like the 100 metre event for chips: how fast can you sprint? But it is also a measure of usable bandwidth as well.
Thanks for that analogy. I am now enlightened. ;)
QuoteThe Rat represents a special case, however, where the gain is so excessive (several thousand at max gain setting), that the slew rate limitations of the chip, both naturally and altered by the 30pf compensation cap, make it do some strange things. To the best of my knowledge, there are no 741-based circuits that aim for the same sort of weirdness.
Do you think someone intimately knew the 741 and its characteristics, and dreamed up in their head "hey, i'm going to do this and this to really torture that thing and it'll pull out these bizarre slew rate artifacts", or do you think they stumbled upon it by accident and decided it was a keeper? ;)
Good stuff from previous threads covering slew rates and the LM308 vs tl070 debate in a RAT...
http://www.diystompboxes.com/smfforum/index.php?topic=33493.0 (http://www.diystompboxes.com/smfforum/index.php?topic=33493.0)
http://www.diystompboxes.com/smfforum/index.php?topic=4290.0 (http://www.diystompboxes.com/smfforum/index.php?topic=4290.0)
Quote from: JHS on June 27, 2006, 09:17:14 AM
ICs are not good or bad, the challenge is to find the right IC for a given circuit or design.
AMEN! Say it again! . . .
Quote from: MartyMart on June 27, 2006, 04:32:11 AM
I've never tried an "adjustable" cap .... seems like a fine idea and would userp any socketed "cap swopping"
too :D
Can you get say 1n to 15n adjustable ?
MM.
Sorry Marty - variable capacitors go to about 1nF tops, and they're three times the size of the average stompbox!
Skreddy saves the day:
http://www.diystompboxes.com/smfforum/index.php?topic=43037.0
Scroll down for a variable capacitor work-alike.
This is why we love the (http://www.diystompboxes.com/smfforum/Themes/safbluerc1/images/english/search.gif) function. :D