let's talk buffers!

[vendettav]

I know I know, this has been touched thousands of times before but still I dont want a necrobump or whatever. 

I finished my true bypass box yesterday and it worked fine. I plugged it in today to try it out with full volume (it was 2am yesterday) and heard that the signal is pretty quite... hmmm no more breakup no more chugs... DUH. well seems like I need a buffer or my pedalboard (even though it's not THAT long but I have some long cables). I see no other way how a true bypass box could weaken the signal, and yes without it it's back to the normal signal. Oh and I have a morley wah that's not true bypass. So suggest me a good buffer circuit (and simple please) and let me know where to put it.

also current setup. 6m cable (I know I kbnow but I need long a long cable)) > trubypass God Box Tesla (fuzz) > Morley PWA > truebypass box with a behringer octaver in the loop > RP355 > PA
I want to also add my Fuzz Factory clone, an EQ after RP355 and probably my God Box Inferno overdrive for now (I have all the boxes really, just the signal is already weak so I better yet deal with my little setup atm)

[Gus]

I have posted an number of circuit/sims/schematics some not that long ago.

Buffers are easy.  You need to define what you want.
Desired input resistance?
Flat or EQed?
Part you want to use BJT, JFET, opamp, tube, mosfet, IGBT etc?
What cable pf a foot and length?

[vendettav]

Ok well I can't really answer some of your questions

I know I want it flat, the part I'd love to use are BJT, OpAmp, JFET (in most desired to least desired order)

can you elaborate on/explain these, please?
Desired input resistance?
What cable pf a foot and length?

[anchovie]

I have a morley wah that's not true bypass.

There's already a pretty good buffer in the PWA. Your bypass box is causing the problem.

[vendettav]

well, tell me more on that? what exactly could cause the problem?

[sault]

http://www.muzique.com/lab/truebypass.htm

Excellent link on the topic.

The short story is that if your boxes are truly truly true bypass then all your signal is affected by are the cables themselves. This can be good if your cables don't suck, or if you don't mind some cable capacitance. High-capacitance cables will suck treble off your tone, though. Of course, cheaper cables often have more capacitance/foot than more expensive ones...

Anyways, a true bypass that isn't actually true means that the pedal's circuitry will load down the signal even with the pedal off. I had a Big Muff that did that - the pedal affected the tone whether it was on or off.

I prefer buffers. Buffers of any kind will present a lower output impedance than pickups do, and lower output impedance means less effect that cable capacitance has on your signal.

In other words... buffers mean you can buy cheap cables and not worry about your tone. My guitars either have active pickups or an onboard buffer... I'm too cheap to buy expensive cables, and I'd rather just keep my tone where its at, thank you very much!

... on the other hand, bad buffers present their own problems...

I like op-amp buffers, especially when the op-amp is a TLxxx series. The Jfet inputs give an extremely high input resistance (>10MΩ usually) and a very low output resistance (in the hundreds of ohms or less). 9v of headroom is plenty if you're talking coming straight off of the guitar.

The sooner you get to that buffer, the less your cables affect your tone. Thus, why I like having a buffer in the guitar itself...

[Gurner]

The sooner you get to that buffer, the less your cables affect your tone. Thus, why I like having a buffer in the guitar itself...

The problem with buffers is that - by and large - guitarists have got used to - indeed got to like the sound of a little bit of cable capacitance - their ear embraces it over time.

Slap in a buffer which 'restores' the lost highs...and the pickup then apprently takes on a whole new aural signature - not neccesarily for the good in the guitarist's ears!

What you really need is a buffer with a cable emulator on the output!

[azrael]

the bypass box could be causing the problem if it's simply not built well.

[FlyingZ]

It sounds like a bad connection in the box. Avoid buffers if you can, they may boost signal but once you own a really great sounding amp the signal degradation will annoy you. Anywhere after the amp they work fine.

[vendettav]

thanx guys for the input. Yeah, I already found that ground was touching the hot wire and I had about 2k resistance between the two thus the volume loss. 

[anchovie]

well, tell me more on that? what exactly could cause the problem?

Glad to see you found the problem yourself. I was only pointing you in the right direction to investigate - I wouldn't have known what the actual build of your bypass box was like! 

[sault]

The problem with buffers is that - by and large - guitarists have got used to - indeed got to like the sound of a little bit of cable capacitance - their ear embraces it over time.

And who says that the old ways are always the best ones? I do acknowledge that I have to be more careful with how I treat my highs... but I do have a tone knob, and I can always tame my high end in how I position my pickups or deal with it in the signal chain. I like an overall brighter sound, too, so I guess its one of those "to each his own" things. A brighter tone, even at the cost of the low low end seems to cut through the mix better when I play live... hey, YMMV.

[vendettav]

^ you know I've always wondered what YMMV means

[DavenPaget]

^ you know I've always wondered what YMMV means

Your mileage may vary ... It is kind of a universal sentence really .

There's also ( but hardly used ) YMPGMC ( your miles per gallon might change )

[Gurner]

And who says that the old ways are always the best ones?

Not me...I never said that or implied that (just passing comment on how adding a buffer will change the end tone), but since you ask about who says the old ways are always the best ........erhm wrt guiitarists,  apparently the masses - witness everyone yearning for PAFs, 62 reissues blah blah.

[amptramp]

Take a typical TL071 booster like this:



If you want to roll off the high frequencies to make it sound like a cable, just add a capacitor across R2.  100 pF puts the -3db rolloff at 7238 Hz.  This can be varied, but with a buffer, it will not matter what cables you use at the output - the rolloff will remain almost in the same place since the output impedance would be no higher than about 3000 ohms.  BTW, I would modify the above circuit to add a resistor of 300 to 500 ohms at the output between pin 6 and the junction of R2 and the 10 µF cap going to the pot.  Put the added capacitor of 100 pF or whatever from pin 6 to pin 2.  This will add stability when driving long cables.

The rolloff calculator is here:

http://www.muzique.com/schem/filter.htm

[Gus]

amptramp

The cable interacts in a different way with pickups and the input of an amp than in that simple calculator


The inductance of the pickup and resistance and capacitance AND the cable cap AND the input resistance and miller interact and can cause a rise in the highs before a roll off.
note the series resistance from the volume control

50K series resistance(from the volume control) takes out the high end bump

[crash415]

Gus, how would that frequency response look like if you were to build that buffer in the guitar.  You could get rid of R8, R11, C4 and R9.  Could you use R5/R13 as the volume?  How would that circuit affect the frequency response?

[brett]

Hi
Buffers and buffer/boosters can be really handy. But will they save tone?
Jimi's long curly cables probably had a thousand pFs of capacitance (or more). How did he sound? Clapton played through some bad cables (but great amps). Again, definately not bad. Quite a few early stompboxes have a 1000pF cap across their input (ie in *addition* to a few hundred pFs of early cables).
cheers

[Gus]

link to a thread
http://www.diystompboxes.com/smfforum/index.php?topic=93834.0