True Bypass Questions

[jeremylangford]

I have 6 pedals and 4 of them are true bypass. I was thinking about upgrading the last two to true bypass. (Replace my Boss TU-2 tuner with a Korg PitchBlack tuner and replacing my Boss tremelo with an Electro Harmonix tremelo.) I have been thinking about this for a while but after reading a lot of things on the internet about true bypass I am wondering if this is the best thing for me to do. I keep seeing things about how true bypass causes a signal loss and other bad things and that if you have all of your pedals true bypassed and chained together that you will need to buy a buffer pedal. I have always thought that true bypass was the best thing you could do and that this was what all professionals do. But now I'm reading bad things about it.

What do professional guitarists do? If have all true bypass pedals, then how do they deal with signal loss? Should I upgrade my two buffered-bypass pedals?

[andy]

Most pros use Boss Pedals!!!

I think that the true bypass thing is a bit of a marketting buzz word at the moment. It means that the tone is not affected by a buffer (as in loss of dynamics, usually), but it does nothing for the fact that extra cable length reduces high end response and overall volume, resulting in much the same effect.

To compensate for having lots of true bypass pedals adding lots of extra 'cable' to the sound, you will need a pedal which does some thing very similar to your Boss pedals anyway. Boss's have a very particular buffer tone, to my ears, but if not that one, then another, so you probably have a pretty good balance with 4 true bypass to 2 buffered. If you were to replace one of the two, then keeping the other buffered pedal should keep the tone in best condition without forking out tonnes for an extra buffer pedal.

[jeremylangford]

How exactly does having a buffered bypass pedal or a buffer pedal at the beginning of my pedal line help my tone? Does it take the input from the guitar and make sure it is the same as the signal return after the signal runs throught the rest of the pedals and amp?

Sorry for my ignorance.

[andy]

Ummm, yes I think so, but I'm fairly ignorant of how it really works myself! I notice the effect on the sound as a very subtle compression, not neccessarily in a negative way, but it is there. However, a buffer changes the signal so that it will not degrade so much down a longer run of cable, I'm thinking like a local pumping station for domestic water supply, bumping up the pressue to get down all the pipes to peoples houses! It basically means that you can use a longer cable (or longer run of effects) without losing quality of tone to all that wire.

There is a good article from one of the worlds pedal gurus sticking up for buffers here...

www.petecornish.co.uk/case_against_true_bypass.html

In case you were wondering, I have a buffer at the front of my chain, three TBP pedals in the middle, and one buffer at the end. It only worked out that way by chance, but seems to work out OK! I may have gone for just the one buffer if price had been less of an issue, but some guys use 10 buffered pedals in a row, and get by fine.

The thing to remember is that if you don't have a problem, there is nothing to fix and if your tone is fine, don't let idealistic (and usually profit enhancing) notions get you buying stuff you may not need!

[jeremylangford]

I understand that true bypass pedals can be bad because when they are off, they just act as a really long guitar chord which can make the signal weaker by the time it hits the amp.

But can someone explain to me how having one buffered bypass pedal or a buffer pedal along with the true bypass chain can fix the problem?

[ashcatlt]

Well I can try...

The term "signal loss" is a bit general. Specifically what you might experience with a number of true bypass pedals and (more importantly) the cables before, between, and after them, is a loss of treble.

There is a certain amount of capacitance between the two conductors in our cables. Longer cables have more of this capacitance. In fact, some cables will actually tell you how much capacitance you can expect per foot of cable. This capacitance is in parallel with the pickups and amp input. That is, it's between the "hot" line and the "ground". That's the same configuration you see on your tone pot, no? This creates a low-pass filter. A higher capacitance makes for a lower cutoff frequency for this filter. That is, with a longer cable, it starts to roll off "sooner", and more of your highest frequencies are shunted to ground before they can be amplified.

The buffer essentially terminates the cable. For these purposes, it can be taken to be the end of the circuit. This keeps the overall capacitance lower by shortening the run of cable between pickup and amplifier.

"So," you might wonder, "what about the cable on the other side of the buffer?" Well, another thing that will change the cutoff frequency of the filter is the overall impedance of the circuit. On the "pickup side" of the buffer this is quite high - somewhere in the thousands to tens-of-thousands of ohms. On the other side, though, it's comparatively tiny. For some opamps, this could approach zero, but in most cases its a hundred or two ohms. This has the effect of increasing the frequency where the filter starts to roll off to something high enough not to bother us.

Does that help?

[jeremylangford]

Thank you. That helpsa lot, but as normal, most of the stuff you are talking about is over my head. I need to go to the library and read up on the basics of AC current or something.

Should I just think of a dedicated buffer pedal as something that sits in front of your pedal line and boosts the signal so that it can make it through all the true bypass pedals and then to the amp without loosing anything on the way?

Also, does a pedal with buffered bypass (such as a boss tuner) do the same thing as a dedicated buffer pedal (such as an Axess BS-2)?

And lastly, why do most people put their dedicated buffer pedals before their wah pedal?

Thanks

[ashcatlt]

Dec 17, 2008 21:54:07 GMT -5 jeremylangford said:

Thank you. That helpsa lot, but as normal, most of the stuff you are talking about is over my head. I need to go to the library and read up on the basics of AC current or something.

Should I just think of a dedicated buffer pedal as something that sits in front of your pedal line and boosts the signal so that it can make it through all the true bypass pedals and then to the amp without loosing anything on the way?

I'd rather you didn't. The buffer buffers. Better to think of it as ending the circuit before it and starting the circuit after it.

Also, does a pedal with buffered bypass (such as a boss tuner) do the same thing as a dedicated buffer pedal (such as an Axess BS-2)?

Yeah, pretty much. That Axess thing has more outputs, one of which is transformer isolated. That transformer is only really necessary if you intend to split the signal at this point and end up with a ground loop which could cause excess noise/hum. There may or may not be a noticeable difference in the quality of the buffer.

And lastly, why do most people put their dedicated buffer pedals before their wah pedal?

Thanks

That's a tricky one, and begs the question "Who's most people?"

Most modern wahs are buffered to begin with. Some of the older ones weren't, and actually depended to some extent on the interaction with the pickup/controls/cable for their sound. If nothing else, putting a buffer between would make the wah itself more consistent when switching between different guitars, or even flipping switches and turning knobs on one guitar. It also might alter the voicing of the wah. Whether or not this is a good thing depends on your tastes.

[jeremylangford]

Dec 17, 2008 22:53:43 GMT -5 ashcatlt said:

I'd rather you didn't. The buffer buffers. Better to think of it as ending the circuit before it and starting the circuit after it.

Oh ok. Thats simple enough. So what about the rest of the chain after the buffer. How does the buffer control that?

[ashcatlt]

Presents a very low source impedance.

[jeremylangford]

In some places I read that you should have one before the pedals and one after the pedals. Is this usually not necessary?

[ChrisK]

A buffer is an amplifier. It usually does not (significantly) increase the signal voltage level, but it does increase the signal drive current level. This occurs due the buffer having a much lower output impedance, and a much higher current drive capability than the unamplified passive guitar pickup signal.

Think of it as power steering or power brakes. The steering wheel or brake pedal doesn't move any further than the unbuffered mechanical systems of yester-year (I don't oft have opportunity to use "yester-year" in a sentence, let alone "yester-millennia", so bear with me please), but they are much easier to operate and do easily overcome the mechanical resistance (impedance) of the steering and brake linkages.

In essence, the buffer is a bull(y), less than concerned or effected by the sundry ceramics (capacitance) encountered on its way thru the China shop.

[newey]

OK, this raises (in my mind at least) a question:

You have a selection of different sorts of pedals, with power to all.

You also have a multimeter, and a length of guitar cable with a plug at one end and alligator clips on the wires at the other end.

You do not have access to any technical info on the pedals.

You have no other tools with which to dismember the pedals, nor do you wish to do so.

You also have a guitar and an amp, and various cables to connect same.

Can you determine whether one or more of the pedals has a buffer?

[ChrisK]

Yes.



Since they all use power, they all have an output buffer in one form or another. They may have significant output impedance in the form of a weak buffer, asymmetrical drive capability (an active pull-down and a resistive pull up), or a pot on the output. If they have significant output impedance, they will be affected by what they are connected to down-chain.

A. If the question in play is "does the pedal act as a buffer when in bypass", then there may be simple ways to ascertain this.

B. If the question in play is "does the pedal have a true bypass", this can be ascertained with the meter measuring the resistance from input tip to output tip when in true bypass. If true, the resistance from tip to tip will be well under 5 Ohms. If the resistance from either tip to the ground is not infinite (or really, really large), the pedal may not have a true bypass in that it still loads the input signal even if it directly connects tip to tip.

If the resistance tip to tip is not indicative of a direct connection, then the pedal likely has a (hopefully) clean buffer function when in bypass.

[ashcatlt]

Dec 18, 2008 14:40:40 GMT -5 jeremylangford said:

In some places I read that you should have one before the pedals and one after the pedals. Is this usually not necessary?

Normally? No.

The folks that need a buffer at the end of their true-bypass chain are the same people who might benefit from true-bypass pedals to begin with. That is, people with LOTS of pedals, where too many buffers will add up to noticeable noise or signal degredation. This also means a lot of cable, if you coun't up the connections between each pedal. At that point, it's not a bad idea to end the circuit and start a new one with a final buffer.

[jmpacheco]

Hi. I realize I caught this post a bit "late" but I am in need of some advice with regards to cable length, true bypass and other topics that relate to the post.

I am currently looking to change my rig from a pedal board (it consists of about 18 different stomp boxes, mostly boss, electro harmonix, digitech and so fourth) to a rack rig using a GCX from Voodoo Lab.

www.voodoolab.com/gcx.htm

The thing is, some of my effects (some crybaby wahs, digitech whammy, ect.) need to be "on the floor" to operate. This means that I will have to run a cable 10ft at least from my gcx to my pedal board and another back for each of the pedals. Obviously because the Gcx is true bypass, whenever an effect is not in use, all the cable that runs to and from that effect will be bypassed. Still, I am worried about signal loss from all that amount of cable.

I have considered using a planet waves modular snake to run all the cable (to avoid constant connecting and disconnecting.)

store.daddario.com/category/146512?language_id=1¤cy_id=1

What can I experience in terms of signal loss? Are there any flaws to this rig design that I haven't taken into account?

(PS. One of the stomp boxes I want to keep in my floorboard is a Dunlop Talk Box, so I will be using the planet waves snake from my amp head to my speaker cabinet on one of its cords. Should I worry about this?)

[JohnH]

Hi jmpacheco, and welcome to GN2

That sounds like a mighty rig you are assembling, and the switcher unit looks like a nice piece of kit. While there may be other issues that are not obvious to me, the one thing I think you definately need to use is a buffer , straight after the guitar cable. I see that the gcx unit has such a thing built in. Once the signal has gone through that, it will be low impedance and virtually unaffected by any sensible multiple lengths of cable in the loops following it.

The key point is that the passive guitar pickups interact with the capacitance of the cable in a way that affects their tone, and too long a total length of cable directly connected to the guitar will dull the reble in the same way as a tone capacitor. After that one buffer, then all other connections can be true bypass if you think that may help.
cheers
John

[ashcatlt]

Couple things.

1) Some pedals (fuzz-face type distortions and some wahs) are designed with what we would consider unacceptably low inpedance at the input. They rely on the loss of treble from the cable run as a sort of pre-filter to help shape their response. These pedals will not sound right if they come after a buffer or other active stage.

2) The snakes to which you've linked look pretty cool, but I'm not seeing a 1/4" TS breakout. I see TRS. These won't generally work on pedals which use the input jack to switch the power. You know, like all the pedals you have where they turn off if you unplug the input cable? They're wired with a TRS jack. The battery (and usually wall-wart) power is interrupted until you plug a TS in there, then the R and S from the jack both contact the S of the plug, completing the circuit. I also see TT (tiny-telephone) which will not work because they're too small.

Now if you happen to have some old computer cables and a bunch of spare TS plugs -oh, and a bunch of time and patience - laying around you could probably make your own. I can't remember where I left my time and patience, probably at the bottom of that pile of unopened bills...

3) You can get away with running a speaker signal through a shielded cable sometimes, but it's not best practice. Remember that cable capacitance we were talking about? Well, that means that some portion of the signal is actually shorting out inside the cable. This isn't a big deal when we're talking the tiny amounts of power coming from a guitar, or even a line level signal. When we start to get to real speaker levels, though, this can start to translate to noticeable heat dissapation. See my post in the "Handy Tips" thread for low cost speaker cable alternatives.

Otherwise, I agree with John.