Sorry kunde inte låta bli, här kommer lite diskussioner kring ts808, boss od, bd-2, od-3 mm. tänkte det kunde intressera dig om du nu börjar nörda ner dig i pedalträsket
boss sd-1 vs tubescreamer:
The SD-1 is quite close in conception to a Tube Screamer and not so far tone-wise. It also sports the same three knobs: Drive (amount of overdrive), Level (output Volume) and Tone (Equalization). But I find it to have a bit more grit, it has a more “rock” tone whereas Tube Screamers lean more on the “blues” side (I am over simplifying here). Also, The BOSS SD-1 is a favorite among metal players to be used as a booster, not a main distortion. You won’t get a better and cheaper option to push an already overdriven Marshall amp over the edge.
This is exactly how Zakk Wylde used it for years before getting his own signature overdrive model with MXR. Even the almighty Eddie Van Halen had a BOSS SD-1 in his pedal board in the 90s, presumably used as a boost to give his Peavey amps a kick. In that respect, the level control is very useful on both the Tube Screamer or the SD-1. By cranking it while keeping the gain quite low, you can push any tube amp into natural overdrive.
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11 GaugeFebruary 15th, 2012, 12:19 PM
The point is, the TS-9 was an evolution of the TS-808. The SD-1 was an evolution of the OD-1. The Ibanez and Boss pedals competed with one another; they were not based on one another. Each evolved along it's own branch of the overdrive pedal family tree.
This is not entirely accurate.
What is so easily forgotten is what did the original designer use as the building block?
We need only go back to the Fuzz Face to see this at another point in pedal history. The basic circuit in the Fuzz Face (meaning almost all of it) was a very standard audio preamplifier circuit - Arbiter/Vox/etc./etc. simply "plugged in values" for the components, mainly in an effort to simply make the transistors bias up effectively.
Now jump forward to the OD-1/808, and we have again a very basic audio application of a standardized circuit implementation. But in this case, the op amp is now available and cheap, so it has been configured to be in a pedal.
...The guitar has a limited range of frequencies it can reproduce, and when driven into distortion, intermodulation will occur. That means you want to reduce bass at the circuit's input. Next, an op amp was designed as a linear device - when it clips (distorts), it sounds like crap - you need diodes in there to "limit and clamp". Both of these concepts are nothing new to basic audio design via op amps.
...So you will need a little more processing for the bandwidth of a guitar signal - treble above 5K (max) isn't really reproduced, and anything "overly amplified" (which is what typically happens with an op amp) must have a way to reduce and adjust the treble. This was done in both the OD-1 and 808 by rolling off treble with a fixed filter on the first op amp stage's output. But to recover signal AND treble, a second op amp stage is helpful. In the case of the OD-1, only the signal was recovered. In the case of the 808, a control to tweak the amount of treble was put in place of something hardwired in the OD-1.
Since the building blocks were already designed, neither pedal was designed in isolation. This is especially true once you consider that:
- both pedals have the same high pass filter frequency
- both pedals have the clipping diodes in the negative feedback loop (everything else like a Rat or D+ had them shunted to ground)
- both pedals have a "standard" low pass filtering on the output of the first op amp stage (passive, shunted to ground, same frequency cut)
- both pedals use the same bypass buffering method, and the bypass buffers as implemented in the circuits have the same basic components as well
...All of this said, Tamura most likely "shared design notes" with someone at Boss, or they could have even been audio design contemporaries. Tamura is obviously famous, the person(s) at Boss is/are anonymous to this day.
Both the 808 and OD-1 had to have had their R&D completed by probably early 1977 to go into production when they did. I know for certain that the first OD-1's were MIJ in November of '77. (
http://www.bossarea.com/loadpage.asp?file=boxes/od1.xml)
Here is more the standard "quote" of "Tamura's invention," for lack of a better term:
"Tamura, the designer of the Tube Screamer, used a subtle clipping circuit to create the pedal's sound. He mixed the input signal with the output signal of the clipping circuit, which "preserves the original dynamics of the input signal which otherwise would get lost at the threshold of clipping." In this fashion, it preserves the "original dynamics of the input signal...avoids muddiness and vastly improves clarity and responsiveness." As well, Tamura added a post-clipping equalization circuit with a first-order high-pass shelving filter that "is linearly dependent on its gain," an approach called "progressivity." Characteristic of its clipping is the symmetrical nature.
The Tube Screamer uses electronic FET bypass switching. The circuit uses transistor buffers at both the input and the output. The overdrive is produced using a variable gain op-amp circuit with matched diodes in the feedback circuit to produce soft, symmetrical clipping of the input waveform. The overdrive stage is followed by a simple low-pass filter and active tone control circuit and volume control."
Why is the quote relevant? Look at the choice of descriptors, and the lingo used. They are all E.E. terms/audio design terms. Nowhere is Tamura saying, "dood - it sounds like toobz in a box, and it's killer!" If Boss allowed someone from the OD-1's design team to release a similar quote, IMO it would say a similar thing. The electronics/audio concepts would actually read verbatim, because they are verbatim in both pedals.
I highlighted the symmetrical clipping thing in red because the OD-1 has asymmetrical clipping, which is actually touted as sounding more natural and tube-like, but Boss definitely came up with that one first, and it is actually considered part of the "good evolution" of diode clipping in many other pedals (something like the Zendrive immediately springs to mind).
The symmetric clipping diodes in Tamura's design are also relevant as far as "standard design" goes, because that is what was in every other pedal that preceded it, TTBOMK. To this day, it is funny that "808 snobs" will typically turn their nose up at asymmetrical clipping, with many referring to it as "grainy/greasy/unrefined/not silky/not smooth/kind of gritty/etc." because they really believe (not saying that it's wrong) that the original 808 formula is the embodiment of overdrive perfection. I only chose the word snob because it gets the point across quickly - no malice intended.
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soulgeezerFebruary 15th, 2012, 02:34 PM
I repeat my question - why are there so many SD-1 mods out there to make it sound like a tube screamer?
Ah, now *that* question I think I *can* answer: Because they are similar, as 11 Gauge pointed out above. The SD-1 is significantly cheaper than a Tube Screamer, the Boss has "a much better switch" (according to the AnalogMan Web site), and it lends itself to such modifications. Therefore, folks can make a buck off doing these mods.
Personally, I don't get the whole "mod" thing. If you want an 808, then just buy an 808. I've got three of them: One original and two reissues. Even though the reissues are apparently (again, according to AnalogMan) built on the TS-9 PCB, I don't hear any significant difference between the new ones and the old one. So, I keep a new one on my board and the old one for studio use (mostly because I don't want to have to take the new one off the board every time I record. I don't use the board in the studio; I only set up the pedals that are actually being used). The other new one is a back-up.
Some people spend a whole lot of money chasing some kind of holy grail tone which, even if they achieve it, will likely disappear in a band mix. So, I just use pretty much everything bone stock and adjust for a sound that works *in the band*. If I don't like a pedal, I get rid of it and find something that I do like. I do not spend time, effort, and money trying to change a cat into a dog.
(Full disclosure: My flanger was modified to true bypass, because at the time I was buying into the whole "true bypass or you're killing your tone!" hype. I have since learned better. So, although I do use a true bypass loop box - because I have a germanium treble booster that needs to see an unbuffered signal - I have not altered any of my other buffered pedals.)
All of this is just my opinion, of course. Feel free to ignore it, as it probably deserves!
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Personally, I don't get the whole "mod" thing. If you want an 808, then just buy an 808.
IF the "whole" mod thing is simply turning a 9 or SD-1 into a 808, I agree.
Thank goodness it isn't! Because of the low SD-1 price tag, the good construction, and the "serviceability aspect," you can turn it into a Zendrive, Timmy, OCD, Fulldrive 2, etc...and since it doesn't cost what a TS does, modding it makes more sense. You can hide a Zendrive's "4th control" inside the battery compartment, and leave your real Zendrive at home. No one would steal your SD-1 most likely, even if it did sound like a ZD. And if they did - you could replace it with another one for less than $60!
And the 808 conversion thing's heyday has come and gone, IMO. If someone wants an SD to Frankenstein, there's that option. If you want a 9-series, there's that option. Then there are a zillion 808's - either reissues, kits, boutique clones, etc.
I do think the "brown mod" is a nice little project for youngsters (or po' folk) who can't afford any type of 808 A used SD-1 and two resistors from Rat Shack can make for a glorious low-buck alternative (and sound). Or a used TS-5/7, beat up 9, etc. All can be found cheap, and the mod is caveman simple, with a capital S.
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Hard clipping distortions
(negative feedback)...and shunting ?[/I] with respect to "TS" vs. Rat?
When you put clipping diodes in a negative feedback loop, you get what is known as "soft clipping." The clipped signal is literally mixed with a non-clipped signal, with the non-clipped being at unity gain.
When you have diodes that are "shunted to ground," they literally take a lot of the amplified signal and dump it straight to ground, where nothing is passed on at unity gain like in a loop - part of your signal not only gets altered/compressed/etc. but it also is "made smaller." This is called hard clipping. It is much more obvious, more aggressive, etc. And unless there is a "recovery stage" after it, the signal can drop quite a bit. Such is the case with the D+/OD 250. The Rat has a unity gain transistor buffer, but it still doesn't "recover" like an OD does, IMO. Same thing with a DS-1, or most hard clipper designs.
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The OD-1 to SD-1 evolution wasn't really linear.
The OD-1 made its debut in November of '77. It went through a lot of revisions with different op amps and such. But by February of '81 the SD-1 was released as an improvement to the "final evolution" of the OD-1. Boss felt that a tone circuit was needed, so one was added.
...By extension of that, the SD-1 is primarily a final rev. OD-1 with the tone circuit. Boss had gone to the same 4558 chip as the TS with the final OD-1D's and all of the OD-1E's. Well, TS freaks will argue that it's different because Boss used the TL4558P, uP4558C, and C4558C along with the "real" JRC4558D.
IMO, most differences that people hear between the OD-1 and SD-1 are with the OD-1A to OD-1B series, which had the most circuit differences, and used the RC3404ADB and uPC4741C op amps. Boss had NO issues sourcing their parts from the lowest bid source, which meant NEC, TI, or whomever was cheaper than JRC! This is witnessed with the DS-1 to this day, as well as the numerous Boss pedals that use the "dreaded" L series op amps (8 pins in line).
The SD-1 has remained just about the same as it was in '81. The op amp now has two D's, but that just means dual layer, or quieter operation, slightly more gain as a result (negligible IMO, really). Even when Boss opened their factory in Taiwan, the SD-1 stayed the same.
The OD-3 has nothing in common with the OD-1. It is the offspring of the OD-2. The OD-2 was a radical departure in stompbox design, at least for Boss. It has NO op amps at all. It uses a configuration of transistors to simulate a crude op amp - the result is more favorable for use in stompboxes since it can't stay linear like a true op amp can - you get more inherent asymmetrical clipping! The downside is that it requires funky biasing and the circuit is complex in comparison to an 8 pin chip. In the case of the OD-2, the "turbo" mode cut the voltage down to UNDER 6VDC, which is why it distorts so readily. The array of transistors requires a pair of jFET's with a PNP bipolar transistor on the output.
...The normal mode with the OD-2 is basically a single gain stage with those three transistors, and the same clipping diode arrangement as the SD-1 in the negative feedback loop of the array. It runs at around 8VDC IIRC. The turbo mode uses a PAIR of those gain stages at lower supply voltage with NO clipping diodes. Both "meet" at the same tone circuit, which is identical to the BD-2.
The BD-2 is the ancestor to the OD-2. It basically takes the turbo mode and does the following things:
- voltage goes up to 8VDC
- first gain stage is set up like a SD-1, cutting all the bass out
- "fixed tone stack" that simulates BF/SF amp comes after first gain stage
- 4 clipping diodes to ground follow the fixed tone circuit
- second gain stage is like first, but doesn't cut bass like the SD-1
- a dual ganged 250K pot controls BOTH gain stages (one was fixed in the OD-2's turbo mode)
- there is a mild filter to remove some bass AND treble after the 2nd gain stage
- same tone stack as OD-2 is next in circuit
- an op amp boost stage comes AFTER the level control, and has a fixed ACTIVE bass boost
The OD-3 is the final offspring (thus far) and differs from the BD-2 in the following ways:
- true 9VDC operation
- first gain stage is unity gain with a fixed "notch" filter (cut before boost)
- second gain stage is like the ones in OD-2/BD-2, but it has clipping diodes before and after it
- third gain stage is a "discrete class A" stage with clipping diodes
- fourth and fifth stages are op amp ACTIVE EQ shaping - they are like a hardwired Baxandall tone circuit (bass and treble)
- tone circuit like in OD-2/BD-2 comes next, but has modified component values (for better bass/treble balance)
- level control is last, with no post boost op amp like BD-2
...The OD-3 gives asymmetric clipping with the most headroom, and the best staging of EQ filtering. There is no funky tone circuitry, all gain stages that clip have diodes to clamp them nicely, and the op amp portion is "encapsulated" within the circuit.
Back to the SD-1: the debate will probably always exist of it versus the TS. I think that both Maxon and Boss understood that the dual op amp was a great way to make a mild distortion pedal, but had different ideas on how to tonally voice it. I'm certain that Boss "borrowed" the TS tone circuit for the SD-1, but it made sense for a pedal design like that at the time. What is MORE interesting is all of the CHANGES that the TS has gone through over the years, with the different op amps, and the change to the two different output resistor values in the 9 series, to make them work better with solid state amps in the 80's, which were very popular at the time.
...The SD-1 has "stayed the course" for all of these years, even though the TS has not!
I TRULY believe that if the pawn shop that SRV went to had a SD-1 instead of a TS, that would be the "grail overdrive" today. That said, if he had to pick a NEWER design that came along had he lived, I firmly believe that he would have gone to the Marshall Bluesbreaker, without a doubt.