This with wether a buffer is needed and where it should go if needed and what the effects of buffers would be and what kind of buffer would be needed is a subject that pops up now and then and it is a subject with many levels, and below are some answers I have given on occations
Let's start with pick ups.
Most guitar pick ups are of the passive kind, made from a coil of wire, and a magnetsystem and some mechanical parts to hold the contraption together
Due to the coil the pick up then gets an impedance that rises with frequency. It's an impedance as it contains several 'ghost' parts as in the wire resistans that is measured in Ohm's or more often KiloOhms
which makes the unit more managable and this is also what one easily can measure with a DVM or VOM, but then it becomes tricky as there is also an inductance, interwire capacitans, an possibly metalparts that add to the inductance and so a complex filter is formed: a lowpassfilter with resonans.
Now just keeping the last part in mind the peak of the resonans is affected by the loading it sees.
Loading here means anything that is connected across the poles of the pick up so that means potentiometers
tone capacitors, capacitans in the cable that connects the guitar to first amplification stage( really this can be a fuzz or a buffer or amplifier input or.......)
In a pedalboard system all capacitans in the cables add up as the appear in parallell with eachother, like this first cable 50pF, second cable 50 pF and if we stop here total capacitans is 100pF.
If all pedals in the system are truebypass, all cable capacitans adds on.
This then appears in parallell with the controls inside the guitar and the input network on the amplifier.
Often it is desired to tune the resonans of a pick up. There are examples of guitars with preamps to the pick ups in an effort to make as pure tone as possible, i.e Les Paul Recording, but musicians tend to want a voice from there instrument. There's another example of the Levin Horseshoe pick up that could reproduce signals up to 40KHz- well it was the time of treble guitar maybe this example was for the dogs, as normal human hearing only extends to about 20KHz if ears are in good condition.
I don't know about you, but I'd tend to define treble into useful treble that is just a bit lower than I actually can hear. There's just this point where intelligence is affected. Here's an experiment if you compare just the delay signal of a BOSS DD2 ( most any digital delay would do fine), with the straight tone, do you find that you have lost any treble? Let's for the sake of the discussion exclude the influence of the buffers and just toggle effect on and off.
If you'd do the same thing with an analog delay of standard type what do you find?
This effect should perhaps be more evident if you'd throw a tapeecho in there too.
All will affect high treble to some extent, but there may also be a level of nothing really important lost.
I can say difference between buffered and unbuffered systems can be quite significant, and I have also used a 'silent' pedal in my own system for years. It's an old Ibanez that has the 'vandal' switch.
Sometimes it flickers or seem hard to turn on but then I use it always on anyway
It has the OP amp buffers and does cut a bit tone, but not harder than that I can set things fine with the tonecontrols on amp- actually there's a slight loss of high treble, while no loss in signal strength or voltage. This one pedal I've had in the loop of amp for years when uisng ampdistortion and on a string on the floor when using pedals in front of amp.
When on a string this would be the only buffered pedal I have and that at the end of the string and so what guitar I use would be loaded in bypass by the cable from guitar and interconnecting cables between pedals while the total length of those is about 1m. The resulting capacitive load on the guitar is then 760pF- yes I could use a cap in each guitar or to each pick up on each guitar to tune that and use 6meters of George L with the same result, but the cable I have and use has better dynamics
as in how it folds on the floor and it's red so I can easily spot itAs long as the resulting sound is fine.
Oh yes, I have had 6 BOSS pedals and someother similar effects in terms of switching on a string several years ago and the merits of the switches were that they were extremely durable and utterly silent while the merits of the buffers where that only the first cable from guitar to first pedal entered as load and so system was very easily controlled in terms of loading also interconnecting cables were dampened by being driven from a low impedance theoretically but hard to define by this quality alone.
Drawbacks were that signalvolage was dropped a bit by each pedal-notiacble when entering a highimpedance like a tube amp but the BOSS pedals could drive low impedance loads as in older effects or studioquality gear that otherwise would muffle the guitar by loading- here the buffers isolated the load so that the guitar only saw the buffered input and not the a lot lower impedance of EH and Oberheim et.c effects.
While the switching was silent and mechanically sound, the headroom and frequency response of the total system was lowered in bypass maybe most by the CE-2 and the Graphic EQ, both using noisereduction systems.
One thing that was devestatingly obvious was that only one gainpedal at a time could be on or sound would get separated- Yes I had and OD-1 and a DS-1 and wet dreams of what these could do together............but not.........didn't work
At the time of arrival of BOSS pedals they were indeed a giant step ahead in durability.
Even so the Arion and EH pedals et.c had more of an organic sound, while the BOSS pedals and also Ibanez to some extent more of just streamline-'it'll work' type of sound and they still do.
It would be hard to say one could not be satisfied with a couple of BOSSes or Ibanezes, though I'd lean towards BOSS since they make better mechanic sense and besides one of my early guitarhereos had a BOSS OD-1- great sound.......
Now it is sometime quoted that there's a plastic quality with the silent switching pedals,
and part of that may be that these are ready and processed sounds.One thing to remember though is that most of these silent switching pedals are tuned to work with Marshall JCM 800 and JCM 900........
Would this have anything to do with switching method?
Well as seen above there can be drawbacks in terms of headroom and frequency response, and signal losses.Internally there can be leakage through the pseudoground et.c. and the dynamic range of a J-FET as used as a switch is limited.
Ah, there's nothing particurlarly wrong with the typical buffer used in such pedals except possibly that they'd have a voltagegain less than one, typically 96 to 98% of the inputvoltage will remain at the output of just one buffer- now you will get current gain, but that's another story...........
With just one pedal and thus two buffers and considering there may be a load at output things may just be a tad better with the circuit in line......guitars don't like to drive lineinputs et.c.
and so there can be losses due to loading that the buffers will isolate from
Anyway if you'd run a system of 6 typical such pedals containing two buffers each at a total of 12 buffers each having a voltage gain less than 1 times you would as an example entering 1V
get at the output of the last stage- now assuming a medium gain of 98% this
1Vx0,98x0,98x0,98x0,98x0,98x0,98x0,98x0,98x0,98x0,98x0,98x0,98........roughly 785mV
If what you drive is a tubeamp input it will react to voltage........oops;)
What if you want to drive your amp's input just so it steers out?
Oh well, you can always add a booster...........
Oh and it could be a bit worse too, if voltage gain of the buffers were to be say 96%.........and then perhaps more than 6 units are connected...........
However with 6 silentswitchers in a row losses would be constant and settings on the amp could easily compensate- everybody happy , everybody wins..............
Back to loading in pedalboard systems, the most noticable effect of loading is just loss of treble.
Now if there is a level of tolerable or even wanted losses, the use of buffers in such a system may totally depend on user preference.
Let's assume system with a couple of pedals, that are all truebypass, medium lenght of cables and desired pick ups in guitar.
Worst case of losses would result when all pedals are bypassed.If there are no detected losses or let's say nothing troublesome, then a buffer may be redundant.
Now if sound changes when going through the whole system like described, then a buffer may be needed.
There can be this scenario that introducing a buffer in a system nulls losses to such an extent that sound has more treble- sometimes this would be desirable.
Buffers are problem solvers, but if you don't have a loading problem a buffer is just a piece of electronics.
As I see it strings to speakercloth and what's in between is the instrument and you may tune all buildingblocks to your ear and vision, not by an exact rule.
It is actually a good question wether a buffer needs to be a dedicated unit. Any pedal run always on becomes a buffer, though it also may do other things. For instance if you run a compressor always on, perhaps set mildly, then everything downstream from the compressor will be driven by the compressor, while your guitar sees the input of the compressor, so in that case a dedicated buffer would be redundant.( that's if the compressor does not need a buffer to work it's best, which would be highly unlikely).
Most compressors have high enough input impedance to make negliable load on pick ups, this would be all pedal compressors I can think of, though there are rack mount compressors that actually may require a buffer to be used with guitar.
In most cases though a buffer will not be needed ahead of a compressor and if a buffer is used in such a position it needs to have really low noise as the compressor cannot distinguish noise from useful signals.
Placement of buffer depends on where the undesirable loading takes place.
An example:
You'd like to use a Maestro Phaser. This is an older unit with rather low input impedance and it will degrade your sound if left hanging as well as when on.
Placing a buffer just a head of the Maestro reduces the loading and makes it negliable. Hm, so then the rest of the system has short cable runs and no other losses are present. The buffer may then make sound a little brighter if left in chain......one solution can then be to place a buffer inside the Maestro or place the Maestro driven by an external buffer in a truebypass loop.
Again if a compressor or other pedal like an eq is on at all times there should be little chance of loading as either would also act as buffer when on.
Hm, you might want to be cautious with using a buffer at the beginning of a system if at least one of your effects capatilizes on loading the pick ups for best effect...........again if you hear no losses you can't stand then all would be fine.
Hm, well you can't clean up all 'sins' at the end of chain. Losses happen along the way and sometimes you really want them too: if you'd play Hendrix system with George L's you'd have one shrill tone
The loading your guitar sees would be the first cable and if all effects are bypassed also the cables between the pedals and then if a buffer is last pedal that will be the final piece of loading to the guitar and if there's no buffer at the end then with all pedals bypassed also the cable to the amplifier and finally the input of the amplifier becomes a part of the load.
Now most likely the longest cable in your system is the one that leads from board to amplifier and any loading that gives would be isolated if there's a buffer in the chain driving that cable or the cable becomes a part of total load .
I think you would know if you need a buffer and most notably by missing treble as in a dull sound- then your guitar may need less loading.
You can select your cables so there is minimum loss and in fact 'hifi' is rarely wanted in guitar systems
Note that some drives and fuzzes et.c that have a lot of gain also have a low inputimpedance to minimize stray noise and maybe also as a filter effect and such pedals may be quite bright if driven from a buffered output.
Yes the input impedance will have great affect on the pick ups
A few examples a Fuzz Face style pedal will have an input impedance in the range of a couple of Kilo Ohms and this loads an e.g, strat pick up so that a lowpassfilter is formed, something that makes this type of pedal much denser in the bass then in the treble.
The lowinput impedance will also load the taper of the volume control making a rapid control range.......
Anything lower as a load than 500K Ohm's will affect the resonance of the pickups notably in conjunction with the guitar electronics.
If load is as low as 10K Ohm's about all of the resonant peak of a standard guitar pick up is flattend-- could be an asset on the bridge pick up of a strat.....
Have fun
BJ
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