Another one of those articles inspired by a seemingly never-ending debate on the guitar forums. This time it involves Boss pedals, and more specifically their buffers. Some claim that Boss pedals make for crap buffers – they generally suck tone, make the tone thin and tinny etc. Others say they’re just fine. So which is it? Read on…
Wait – what’s a buffer?
If you’ve already read a couple of articles on this site, you will no doubt be familiar with the setup – I usually start with establishing the basic facts, before tackling the more specific topic at hand. So in this case, when we say “buffer”, we need to define which parts we are actually talking about. This will become important later on, so bear with me…
A buffer is – simply put – a 1:1 gain (same level at the input and output) amplifier stage. Its job is to serve as an intermediary between the source (the guitar, for instance) and the load (the amplifier or another pedal). You can read more about it here – that article refers to the use of standalone buffers on a pedalboard, but the principle is the same.
Now, the basic circuit layout of a Boss pedal is as the image describes. There’s an input buffer at the start, which deals with the incoming guitar signal (shielding/buffering it from whatever follows). From there, the signal splits to two paths: one leading to the effects circuit itself, and the other carrying the dry bypass signal. Each path has a mute transistor, which is operated by the flip-flop switching circuit, and then there’s a second buffer stage at the end.
So when we discuss the Boss (or anyone’s) buffer, keep in mind that it’s just those two we’re talking about. And most often, it’s actually only the input buffer that is being discussed. So is the Boss buffer any good, then?
There’s not one single Boss buffer
Yep, that’s right. While Boss hasn’t strayed very far from the basic formula they devised back in 1978, there are slight differences between the buffer stages in different pedals. Most of them – again, just looking at the input buffer – look like the schematic cutout to the right.
This is from a DS-1, and R2 sets the input impedance (in this case 470Kohm) while Q1 is a fairly standard silicon small signal NPN bipolar junction transistor (a 2SC2240GR, to be precise). This layout is fairly similar across the range of Boss compact pedals, but there are a few that are different.
The TR-2, for instance, uses a 2SK184GR JFET transistor with 1Mohm input impedance instead, as does the TU-2 and DD-3 (version 2 and 3). People keep talking about the TU-3 sounding different (worse) than the TU-2, and it might be down to a change in the buffer stages. But I haven’t seen a schematic for the TU-3 yet, so I couldn’t say. It could just be the “older = better” thing, of course. Anyway, if you have a TU-3 schematic, feel free to e-mail it to me (address in the footer) 🙂
And some of the older designs (for instance the SP-1, DC-2 and the very first edition OD-1) as well as some newer ones (DD-5, CS-3, and the first edition CH-1, from which we borrow the schematic snippet) use an op-amp as the input buffer. In some – but not all – of those cases, the output buffer is also op-amp rather than discrete transistor-based. And the CH-1 was changed for the second edition – not only was the chorus made digital, but they also switched to a JFET input buffer. Well, I think you get the drift… there’s not one single “Boss buffer” which can be said to sound bad or good.
So while we might be tempted to say that Boss buffers sound good or bad, we need to understand that it isn’t possible to issue such blanket statements. First off because some of them are a bit different than others, and then of course each rig is different – basically, even if we compare the same specific Boss pedal, what works in one rig may not work in another. But even so, some of the Boss pedals seem to change the tone and feel more than others. Why could that be?
There’s more to it than that
So far, we’ve only looked at the input buffer, and while some of them are different, that’s not in itself a big enough difference to cause any major change in the tone. At least not to the point where one would say that “this pedal really sucks the life out of my tone”. And yet, some of them do change the dry signal in less then pleasant ways, even to my ears. So there must be something more going on here. And there is… in some pedals, the bypass signal actually passes through more circuitry than just the input and output buffers.
Enter the pre-emphasis and de-emphasis stages… “Pre-what?” you might say. Well, let’s investigate. In some pedals where there’s a delay circuit which is expected to be noisy – analog delay, earlier digital delays (DD-2/3), chorus/flanger – the signal is passed through a treble boost circuit before the delay chips, and an equal amount treble cut after. The idea is to reduce any hiss that is added by the delay circuit, in much the same way as the Dolby system on your tape deck (if you’re old enough to have experienced those).
For some unexplained reason, Boss decided to combine the de-emphasis section with the output mixer, meaning the dry signal had to pass through those circuits as well. And since these pedals keep the dry signal constant (only adding the delay/chorus/flanger on top of it, when the pedal is turned on), there’s no dry bypass path beside from the one that has passed through these extra circuits, so the tone change is present even when the pedal is turned off. It is a subtle change, but clearly noticeable. There’s something about the attack of the notes that change, once the signal goes through one of these pedals. But it isn’t the buffer’s fault – it’s these extra circuits. If you have a DD-2 or DD-3, you can test this yourself by switching to the direct output. The signal to that output is taken from before the pre-emphasis stage, and to me it sounds – and feels – different.
(No) strength in numbers
Another factor when some claim the Boss buffers sound bad is the sheer number of them. If you have five Boss pedals (this goes for Ibanez etc too, btw) in the chain, even when all five are off you have ten buffer stages in series. Remember earlier, when I said that a buffer stage is merely a 1:1 gain amplifier? Well, that’s what it is meant to be, at least. And while op-amp buffers can reach 1:1 gain, transistor-based ones fall ever so slightly short. Basically, you lose a little signal strength as you go through it. Then why do we keep using them, you might ask? Well, they are simpler to construct, and tend to sound pleasing with guitars (some say that an op-amp buffer can sound “cold” and “stiff” compared to a good transistor one).
Anyway, this tiny loss of signal strength usually isn’t a problem, and is easily made up later in the chain (usually by turning the amp up a smidge). But when you string ten of those stages together, the loss starts to become noticeable. How much? Jack Orman actually measured it, using four Boss pedals (with transistor buffer stages) strung together, and it is a fascinating read. Again, this is another reason someone might say that “Boss’ buffer sucks tone”. But once again, it’s not one single buffer’s fault.
So, was this all a very long-winded way of saying “don’t make blanket statements”? Yes, I suppose so 🙂 But I also hope you picked up a few nuggets of information on the way. And there are a few other conclusions to make, besides the one above.
- Some Boss pedals are very transparent in bypass mode, others less so. Especially the slightly older time-based (delay, chorus, flanger) pedals can have a quite noticeable impact on the bypass tone.
- Don’t chain together too many of them – you will lose a little signal strength through each one, so try not to let that build up. If it starts becoming a problem for you, look into a true bypass loop strip. Leave one outside the strip – to take advantage of its buffers – and get the others out of the way when they’re not being used.
- Oh, and feel free to ignore me completely – if you run 10 Boss pedals in line, and don’t feel there’s a problem, don’t make it into one just because I said something about it. The only opinion that matters is yours!