What Tech 21 has to say and show about true bypass

[Mark Hammer]

An interesting little exposition.  http://www.tech21nyc.com/tech_notes/tech_truebypass.html

Well written and explained.  A useful link to refer people to.

[mydementia]

Good article - thanks for the pointer Mark.

I've always wondered something about rigs where you have a Boss TU2 in front...

Here's how I understand it:
Thanks to the TU2, I have a buffered input signal in bypass so I'm feeding the rest of my chain 'good' signal with appropriate impedance. 
If I add a buffer to the end of my chain I should be able to greatly reduce the effect of long cable run capacitance - right?  Or is this overkill? 

In my setup right now, I plug directly into my TU2 - run into my chain (currently goes into my whammy, then into my loop selector) - out of the loop I run into a MR EQ set at unity volume (thanks to ROG for this excellent circuit) which is providing a nice buffered output to my amp.  Would this be considered 'optimal' or just overkill? 

I like the MR EQ at the end because I can tap a button and add a ton of bass or tap another for a nice tinny intro...

Fun stuff.
Mike

[Papa_lazerous]

Interesting but to add to it another article...........http://www.petecornish.co.uk/case_against_true_bypass.html

[Mark Hammer]

I had seen and read that one before as well.  I just thought it might be nice to add another fairly reasonable voice to Cornish's.  I think there may be a tendency by some to discount his opinion because he deals with such a high-end clientele.  Tech 21 sells to "regular folks" like you and I, whose "stage" may be only as big as their rec room.  I thought, as well, that there was a bit less of a dismissive tone to their note than I recall in Cornish's one, plus the historical perspective, which I liked seeing.

But you're right, folks should read both before attempting any potentially unnecessary alteration of a pedal.  Sometimes, just sometimes, folks sell us stuff after they have thought through all the practicalities of what we might need and request.  You may not have ever corresponded with a Boss or DOD engineer, but I suspect their respective companies let them leave the premises now and then and talk to real folks.

[amz-fx]

Here are some of my comments about that first article:

(1) The true bypass footswitches being used are old "sewing machine switch and never intended for use in audio applications". Wrong. The TB switches used today were specifically designed for audio use.

(2)The TB footswitches "have a fairly high capacitance, typically around 20 pF to 100 pF." Wrong. I measured the capacitance between poles of two types of footswitches (dpdt and 3pdt) and could not measure ANY capacitance to a resolution of 0.001nF (+/- 2pF).

(3)"High capacitance combined with high resistance attenuates high frequencies, making your sound dull and mushy." This could be taken to mean that the switch has a high resistance... not true. The contacts of the typical TB footswitches used currently have a resistance of less than 50 milliohms (0.05 ohms), and may even be silvered for better performance.

(4) "If the Voltage/Amperage marking is 120V/1A or higher, then you can be pretty sure that you don't have a precision device in your hand." Ridiculous... that's just the rating of the switch and has absolutely no correlation to its precision or intended use.

(5)"With digital bypass, the signal never actually bypasses the digital processor. The analog signal from the guitar is still being converted to numbers and then back to analog, but the processor is told not to manipulate these numbers." And how is this advantageous? Even in bypass mode, the signal in the digital bypass is always subject to the limitations of the A/D to D/A conversion process including bit depth errors, distortion, Nyquist limits and conversion delays. That's certainly not better than a couple of pieces of wire going through a 50milliohm switch!

(6) "On the other side of the coin, some pedals will not benefit from a true bypass mod --sonically or mechanically: Boss® and Ibanez® type pedals." The ears of a lot of people will disagree with this statement, but it is subjective...

(7) "You can overcome the sonic shortcomings of the true bypass switch by buffering your guitar's pickups." The 'limitations' of the true bypass switching system are very small indeed. Buffered pedals can provide low impedance drive in some applications but the simple buffers in many of the cheap commercial pedals have their own set of problems.

Just my two cents...

More reading about true bypass: http://www.muzique.com/lab/truebypass.htm
And pedal impedance: http://www.muzique.com/lab/imp.htm

Best regards, Jack

[RedHouse]

Speaking of good articles, did ya see the premier issue of "Premier Guitar"?

Our local superhero (RG) has an column called "Tech Views"

Kudo's RG, let me be the first (or whatever I am) to congradulate you on your new endeavor!.

[scaesic]

http://www.aberdeen-music.com/forums/making-music/36016-true-bypass.html

I once wrote this to help local guitarists.

[soulsonic]

I'm on Mr. Orman's side for this one, that article gets kinda silly at some points. That being said, I want to start using latching relays for bypassing, and forget about all those stupid multi-pole footswitches. A nice small signal latching relay that's turned on and off by a nice heavy SPST footswitch or even one of those nice large snap actions for that "soft switch" vibe.

[bwanasonic]

The bottom line is bypass switching is specific to your setup.  You can make the argument for which scheme works best for the most common setups, but no pedal exists in a vacuum. If it's simply a matter of Guitar>Pedal X > Amp, then there are a variety of bypass schemes that produce satisfactory results. Anyone who has tried to incorporate a vintage Ge Fuzz Face, or Rangemaster , into a larger pedalboard scheme with other effects, has learned that the old and the new don't always play well together. I think the mistake is to assign preferred status to a given switching scheme based on buzz words, rather than your specific setup.

Kerry M

[nooneknows]

I think the mistake is to assign preferred status to a given switching scheme based on buzz words, rather than your specific setup.

I agree, still nothing can persuade me than a buffer is better than a simple short wire and a switch to transfer a signal.
Marcello

[analogmike]

Jack is 100% right as usual.

I would add, that I will sell all my guitars before I allow my dry signal to be digitized and undigitized like those tech21 pedals.

[Papa_lazerous]

I added the Pete Cornish thing just as another side of things........  If I build a bedal I build it true bypass (generally) I know people who think everything should be true bypass, I know one guy who got his crybaby modded for TB and regretted it.  a buffer is a good thing in most cases. I have my wah which is not TB my RC-20 looper not TB and my SD-1 not TB and there is not toen sucking problems from them 

[frankclarke]

Horses for courses. If you have a wah in front of your fuzz face you may or may not want true bypass on your wah, perhaps depending on what kind of buffering your wah has.
If you switch the effect on and off a lot during your songs, you might want a FET bypass to reduce clicks. With some of the germanium fuzzes, they may need to see your pickups, or a rough simulation of your pickups.
It all depends, if you are selling to the public you have to dumb it down to knucklescraping idiot level. These CEO guys are just telling the lowest common denominator that the way they do it is OK, which it may well be. Especially with digital bypass, 'scuse me for not running out to buy that kind of thing.

[petemoore]

  ...show up at the music store with your wheatstone bridge...
 Don't tell 'em I sent 'ya, see if they'll let you sort out their cables !! Bwhoo ha ha !
 You could do the same type of A/B for bench switches.
 Yupp...without a doubt this is no lab test of Sw's and cables, but with the lot of them I have and no buffer, definite drops noticable.
 As far as between buffer and the lot 'o sw's and cableage' Vs. short great cable, it's hard to say except my Echo Park puts a 'Envelope dwiddle' [faint but...an 'above/below triggered' sound, puts a slight warble which makes it mostly just a little irritating to tune the guitar] on the bypass, I don't remember the last one I had doing that...so much for 'digital precision'...or is there an easy fix for this?..@@rate mechanical switching wouldn't care about what power supply or circuit wierdnesses..it's actually bypassing.
 

[Papa_lazerous]

Horses for courses. If you have a wah in front of your fuzz face you may or may not want true bypass on your wah,

I see yer problem.............  FUZZ then WAH    wah then fuzz is pants 

[d95err]

I would add, that I will sell all my guitars before I allow my dry signal to be digitized and undigitized like those tech21 pedals.

AFAIK, Tech 21 products are all analog. The tube amp emulations are just overdriven opamps (and sounds lite it too, IMHO).

They do state that "The sound quality of this bypass largely depends on the quality of the digital converters used and any band-limiting or anti-aliasing filters on the inputs and outputs of a given design". Well, they got that right, but I guess they could have added that it will always mean signal degradation. It would be interesting to compare 10 true bypassed effects in series with 10 digital bypass effects in series...

(EDIT: Although I'd prefer one buffer followed by 10 true bypassed pedals.)

[Mark Hammer]

I didn't want to present the article cited as gospel, and Jack makes some nice and astute retorts to some of their claims (though personally, I find Tec h 21's  claims about the properties of the switches themselves, and the pros and cons of using mechanical switches, two entirely separate issues).  I thought they (Tech 21) did a nice concise job of laying out some of the counter-arguments to the often blind near-religious frenzy people have about true-bypass, and was pleased they raised the issue of what TB was a historical response to.  Like Pete Cornish, though, I suppose they have some vested interest in selling their approach to doing things.  You always have to ask yourself "Who is telling me this and why?".

For me, the bottom line is this: the inherent imperfections of all bypass sytem employed always means you are trading off multiple factors.  They could be noise, cost, impedance, failure protection, simplicity, and several other factors.  It is always in the best interests of the builder or erstwhile modder to ask themselves "What do I gain by using bypass method X, and what do I forfeit?".  Many of us use a simple mechanical switch simply because it is simple, cheap, and easy to understand.  The self-persuasion that it is always the sonically purer route often seems to be a post-hoc rationalization of what we did because doing it another way was a nuisance. 

I'm not trying to paint TB users as dupes.  Just noting that, whether in electronics, love, politics, or any other sphere of human affairs, people have a propensity for convincing themselves they're doing something for one set of reasons when really they're doing it for other reasons they aren't terribly aware of.  It is important to be using TB (or buffers) for the right reasons in that context, so just make sure you think it through and consider the pros and cons of all possible strategies.

Finally, it would seem that the use of TB by boutique builders, and the association of boutique pedals with "quality" in consumers' minds, has made some serious inroads, if a company with the clout and market penetration of Tech 21 has to go to the lengths of presenting technical arguments for why they use the switching system they do.  I guess that speaks highly of us in an indirect way.

[greigoroth]

Okay, help time. Since I began lurking here I have read up a lot on the TB/buffering debate, thanks to Jack, Mark and all the others who contribute easily digestible info on this... it feels like I have a pretty good grasp on things. But can anyone help explain what is happening in my current signal chain?

I have a Bad Horsie wah, which includes a "pure-tone buffer", a Tech 21 Tri-OD which I believe has a buffer, a Guyatone MD-3 - no idea if it has a buffer or not but it is not TB in any case, and similarly a Boss BF-2 (buffered bypass??). I have certainly 1, probably 2 and maybe even more pedals that are buffered there. What is this doing to my signal? What would happen if I had a chain of 6 or 8 or 20 pedals all with buffered outputs? Do the buffers interact? Are there "bad" buffers in there doing nasty things to my sound? Is this enough to drive a 20ft cable between the pedals and the amp or should one build a buffer for the output of the pedalchain as well?

The other night to try and understand a bit more about the bypass of my pedals I did a whole lot of recording to the computer. I recorded my guitar directly out to the amp simp, then with a variety of different cables (both long and short), then with different combinations of my pedals and I couldn't hear any difference on the computer. As I mentioned on the thread about cap testing I think variations in playing had a lot to do with this, even though I tried to minimise this. (. On the other hand it always seems more sparkly when I play directly to the amp. But logic says that with 50 buffers in my signal path it should be all good, and the computer recordings say that there is no discernable difference. Could it be that there was something flawed in the computer recording: I would at least have expected to hear a difference between guitar>6 in patch>amp>computer and guitar>el cheapo 10 ft cable>Hotcake (TB - threw it in so I could see the effect of more cableage)>el cheapo 10 ft cable>amp>computer but I couldn't hear any difference.

Thoughts?

Feel free to ignore large parts of this admittedly long question (or ignore it totally if I have hijacked the thread).

[Mark Hammer]

Though I cast some doubt on the always-and-forever benefits of TB, I would be near the head of the line when it comes to questioning the wisdom of having 6 or more buffers in series.  They will all have input and output caps for DC-blocking purposes (since the vast majority of pedals are designed around the premise that the manufacturer has no idea how you will use them and designs around the worst-case scenario, even if that detracts from performance), and when all those buffers are cascaded, I find it inconceivable that phase coherence (the time alignment of all fundamentals and all their harmonics) will be preserved across the entire spectrum.  Indeed, this may well be why BBE processing sounds as good to so many as it does; multiple cascaded buffers start to cumulatively monkey with the alignment of fundamentals and harmonics.  Note that alignment and phase coherence is entirely separable from noise and bandwidth.  That is, you could be ruler flat from 2hz out to 30khz, and have a virtually immeasurable S/N ratio, yet still sound poor because the harmonics of a mic'd acoustic do not line up like little soldiers with each other or with the fundamentals they are multiples of.

Of course, given the typical playing and listening volume of most live and recorded music these days, and the expected hearing loss, there are a great many people who would probably not notice issues of phase coherence.  Ironically, what destroys their hearing also eliminates sources of audio annoyance (I guess you can't be irritated by what you can't hear).

All that aside, this is one of the reasons why I think buffered true-bypass loop selectors are a terrific thing to build/buy.  They give you the choice of  using the buffers in the pedals themselves, or completely bypassing them.

[Fp-www.Tonepad.com]

A piece of wire, that's bypass. A transistor, at least two resistors, two caps, and a battery that's not bypass. Just do the math for those 10 or 20 pedals you got there.

And if you need a buffer, make a pedal with a dedicated buffer and there you go. Oh, don't forget to make that pedal true bypass.