i have 7 pedal
and wish to build a buffer and preamp,
but where in the chain should they be put....
my first choice: buffer-pedal-preamp
or
preamp-pedal-buffer
or
buffer-preamp-pedal
or
suggestion
is it good....?
bent
I don't think the buffer really matters but I read somewhere (probably here! :icon_confused: ) that the buffer is better as first in the chain however, I can't be certain on that.
The preamp is a different story, what do you want the pre-amp to do?
i read somewhere (me too probably here :icon_wink:) that when you got on stage, the sound technician will love if your sound is preamp....
bent
Preamps are also buffers, so keep that in mind.
Where you put a buffer depends on what you want the buffer for, and what other pedals you have.
For example many fuzz pedals need to be before all buffers.
With a passive guitar, you put a buffer with a high input impedance first in your chain if the pedal has a low impednace input. Otherwise, almost all pedals have an input buffer and a second one is overkill.
You put the preamp before the pedal if you want to boost the signal going into the pedal. You put the preamp after if you need to add gain. And it doesn't matter where you put the preamp if it is just a booster and will be used with the pedal off.
Quote from: seanm on November 19, 2006, 01:47:53 PM
Preamps are also buffers, so keep that in mind.
???
I think he maybe terming a booster as a preamp.....not sure.
What is your use of the preamp??
I consider a booster as a buffer with gain. They may colour your tone more than a true buffer pedal should but usually they can be used as a buffer when set to unity gain.
I consider a preamp as a booster with EQ. But preamps will still have an input buffer stage, or an input buffer with gain.
A buffer is used to isolate parts of a circuit. A common use for a buffer in stompboxes is to provide a high impedance input. Another use is to provide a low impedance output. My blender uses buffers to prevent unwanted feedback. I have also used buffers on a tuner out so that you can connect and disconnect the tuner while the preamp is running with no noise.
If you want, I could walk through a simple preamp and describe all the buffers in it.
Quote from: seanm on November 19, 2006, 02:40:37 PM
If you want, I could walk through a simple preamp and describe all the buffers in it.
Sure :icon_wink:
Quote from: seanm on November 19, 2006, 02:40:37 PM
If you want, I could walk through a simple preamp and describe all the buffers in it.
cool :icon_biggrin:
Hey bent,
What type of preamp are you using??
Quote from: markm on November 19, 2006, 02:56:18 PM
Hey bent,
What type of preamp are you using??
i'm going to build the preamp of http://www.till.com/articles/GuitarPreamp/
with maybe the mod of this page http://www.diyguitarist.com/Guitars/FET-CompactPreamp.htm (at the bottom page)
bent
Ok, here is a simple preamp I designed. It works, but was not "optimized" since I switched to a different design (http://seanm.ca/stomp/preamp.html (http://seanm.ca/stomp/preamp.html)) It does not follow my definition of a preamp since there is no EQ. I consider this a preamp because it is meant to be connected to a power amp. It can provide 20V p-p of clean output.
(http://seanm.ca/stomp/images/preamp-bjt.gif)
I will number the transistors Q1 through Q5 going left to right.
Stage 1 is Q1. This is an input buffer. It provides a high impedance input. I play passive basses and they want to see a high impedance load.
Stage 2 is Q2 and Q3. This is a gain stage. Q2 provides gain. Q2 wants to see a high impedance load for maximum output. But the third stage is low impedance (100K || 15K). So Q3 is a buffer that provides a high impedance to Q2. Basically it buffers or isolates Q2 from the low impedance of stage 3.
Note that Q3 could be designed out, but this is not a commercial product and one extra transistor and resistor will not break the bank. And it makes the design so much easier since I can treat each stage in isolation.
Stage 3 is Q4. This is the second gain stage.
Stage 4 is Q5. The power amp I was using had a very low 10k input impedance. The output impedance from stage 3 was on the order of 4k. This was higher than I like. I generally use the 10x rule. You want the input impedance to be at least 10x the output. So Q5 is an output buffer that reduces the output impedance to 16 ohms. Much better!
So this preamp actually has more buffers than "amps".
thank's for the info, :icon_biggrin:
for my case i'm going to try to find a "preamp for dummies" :icon_redface:, cause i was lost in the explanation, i'm far away of being a technician, so i could'nt follow.... :'( :'( :'(
bent
Yes indeed seanm, very nice.
Impressive indeed. :)
I think this may interest you bent;
(http://aronnelson.com/gallery/albums/album76/AMZ_Jfet_Buffer_LAYOUT.gif)
There's a perf version and the PNP is in my gallery too.
Quote from: bent on November 19, 2006, 03:05:37 PM
Quote from: markm on November 19, 2006, 02:56:18 PM
Hey bent,
What type of preamp are you using??
i'm going to build the preamp of http://www.till.com/articles/GuitarPreamp/
with maybe the mod of this page http://www.diyguitarist.com/Guitars/FET-CompactPreamp.htm (at the bottom page)
bent
Talk about confusing! I use a circuit like that as a buffer. I called it a heater. At +6dB or so, it really can't be considered a preamp. But all circuits put into the guitar body are called preamps :-\
At the one practice space I am 20 feet away from the amp. But all my cables are 20 feet and that doesn't leave any slack to actually plug in. So I run a 20 foot cable from the bass to the heater and then 20 feet from the heater to the amp.
thank's markm for the schematic,
i was going to build the ggg http://www.generalguitargadgets.com/pdf/ggg_buffer_jfet_sc.pdf
what is the difference between a buffer from another? i'm lost in all this...
mark hammer give me a good explaination on my other topic: http://www.diystompboxes.com/smfforum/index.php?topic=48917.msg363174#msg363174
but with the notion of preamp....i'm feeling like going back to start..... :icon_sad:
buffer,booster,preamp, argggggggggggggggggggggg!!!!!!!!!!!!! :icon_eek: :icon_mad: :icon_evil: :-\ :icon_redface:
hope that someone, someday, will do a very clear and simple topic explanation on that...
exemple:
a buffer is : somekind of capacitor that stuck the signal and release it equal....bla bla bla bla
a booster is : somekind of bla bla bla...
a preamp is doing: bla bla bla....
very very clear and simple....
a buffer/booster/preamp for dummies....
bent
Perhaps this might help:
Buffer: Prevents treble loss due to impedance mismatch. High-impedance input, low-impedance output. No gain.
Preamp: Provides slight boost to an input signal. May also damp an input signal. May or may not handle high-impedance inputs, depending on design. May or may not invert the input signal. Intended to be first unit in a signal chain.
Booster: Gain stage somewhere in a signal chain. By convention of this forum, not the first unit in a signal chain. Generally considered to provide clean boost (which may or may not overdrive successive stages). Amount of boost determined by circuit design and available input voltage.
Bent,
Maybe you just need to take astep back. Instead of saying, "I will have a buffer and a preamp, now what do I do with them?" , start by thinking about what you need. After all, unless it is doing somthing useful, adding circuitry betwen your guitar and amp are more likely to hurt your tone and add noise than help. So, Rule #1 should be, "If I don't need it, I don't want it."
So let's try and figure out whether you need a buffer and a preamp. You say you have seven pedals, but we don't know anything about them. Are they buffered? True bypass? Mechanical non-true-bypass? Do they include any old-school fuzzes? Chorus or flanger? What about your amp? All of these things are relevant to answering your question. Here are some guidelines:
1) Buffered pedals are, well, buffered. That includes Boss and ibanez type pedals, that generally have both input and output buffers. If the first pedal in your chain is buffered, then sticking another buffer in front of it is pretty much useless (assuming you are talking about use with conventional electric guitar magnetic pickups. Piezos, which are high impedance, may indeed benefit from a higher impedance load than the 500k or so that many buffered pedals show.) It also follows from this that if you have non-true-bypass pedals and buffered pedals, the benefits of the buffer at the begining of the chain only extend as far as the first buffered pedal.
2) True bypass pedals generally don't need a buffer in front of them, since they are designed to interact with a guitar as is. However, if you find your tone with such a pedal becomes dark or muffled, adding a buffer may indeed be a solution.
3) Where buffers really help is with a string of non-true-bypass pedals, meaning old MXR pedals, Marshall pedals, or others which have either a SPDT mechanical switch or a DPDT switch where one pole just controls the LED. If you have two or more of these in a row, putting a good low input impedance, high output impedance buffer in front of them will help save your tone. Depending on what pedals you have, you may be able to accomplish this just by sandwiching single "tone-sucker" (like MXR) pedals between buffered (like Boss) pedals. Here, a JFET or jfet-input opamp desig would be best.
4) Most amp inputs are high impedance, and do not really require a buffer ahead of them (after the pedals). But, if you are running a long cable from your pedalboard to your amp, or you are splitting your sigal from the pedalboard to two or more amp inputs, or you are feeding a low impdance input like a mixing board or a Acoustic 360 amp, or the end of your pedalboard is high impedance, like a passive volume pedal, then adding a buffer at the end of the board is a good idea. Here, the emphasis is on low output impedance, so a BJT or paraleled oopamp would be great (like the AMZ Superbuffer).
5) As mentioned above, certain things should not have buffers ahead of them, mainly old-school fuzzes like the Fuzz Face and its many variants.
6) Although buffers and preamps/boosters are similar, the big difference is that preamps/boosters are mainly intended to increase signal level, wheras buffers are intended to match impedances. Preamps and boosters usually also have a buffering effect, but they may not do it as well as something designed for buffering. Here again, the question is what you need.
7) In general, maintaining a higher signal level through your signal chain translates to a higher signal to noise ratio. For this you would want a colorless, flat response preamp--probably an opamp design. So, an always-on preamp at the beginning of your pedalboard would be good, right? Well...
8 ) Most pedals have very little headroom--naturally, since they generally run on 9v unipolar power. So boosting the signal coming into them more than a very little bit is likely to overdrive them, maybe in unpleasant ways. If all you have on your board are overdrives and fuzzboxes this is not a problem, but for choruses, phasers, etc., it may be. So it follows that preamping at the beginning of the signal chain may not be such a good idea after all. Depends on your pedals, your guitar, your needs.
9) You may want a preamp at the end of your pedal chain if from there your signal goes to some kind of studio rack gear that is expecting to see a much hotter signal than pedals (or a guitar) would supply. Here, too, your preamp should not color your sound, just make more of it, so go with an opamp design. It should also have a lot of headroom, so an 18v or higher power supply would be a god idea.
10) Another way to use a preamp is as a boost--to increase your volume for solos, or to overload your amp's front end for distortion and volume boost. For most, I think such a boost would go best at the end of your signal chain, especially if you have a tube amp, but this is an area for experimentation. Some people like boosting the input of a fuzz or overdrive to get a really saturated tone. For this purpose, some like a flat boost, but others look for boosters that emphasize certain parts of the audio spectrum, or add some of their own distortion. Season to taste.
HTH,
Ben
Buffer - a unity-gain amplifer. Same gain output as input. Used to buffer the signal before a significant load, like a long cable
Preamp - an amplifier capable of adding gain.
Did you read the text on the GGG buffer page and go to the Peter Cornish link? They're good info.
http://www.generalguitargadgets.com/index.php?option=content&task=view&id=69&Itemid=100
Why is it that certain fuzzes don't get along with buffers?
Great discussion on buffers, guys. Ben hit the nail on the head about the difference between buffers & preamps...I'd add that a preamp, in addition to amplifying your signal by a small amount, is also where a lot of tone shaping generally occurs. Usually you'll have a tone stack in there, and the preamp provides recovery for it at the same time it is amplifying your signal. This is to optimize the signal level hitting the power amp so that it performs its window-shattering amplification role the right way ;) Often they're used to overdrive a signal and create an input rich in harmonics (overdrive). A buffer isn't designed to do this (very well).
If you go guitar >fuzz face > amp, you'll get a really nice fuzz sound like you remember from the '60's. If you go guitar>buffer>fuzz>amp or sometimes guitar>wah>fuzz>amp, you're likely to get a very weak, dark-sounding fuzz. This is because the fuzz face (and a few other ckts) has a very low input impedance. Its nature is to "pull" your signal out of your pickups (tone sucking)...placing a buffer before it prevents this (by the definition of a buffer - high input/low output impedance!), so it can't "do its job" the way it was designed. If a wah does this, sometimes a 1 to 10K resistor in series with the wah output or fuzz input minimizes the effect enough to be acceptable. It's just part of the character of a fuzz face; read up on input impedance to find out about the voltage division effect of this, which is why the phenomenon occurs! Mark Hammer has gone thru the math on that one very well in the forum...
As has been said, if you don't need it, you probably don't want it...by all means, make a simple buffer and play with it to see what happens. Most are low parts count and easy to assemble. I don't like the almost "compressed" way they operate - I lose dynamics with them - but then, I don't use more than 2 or 3 true bypassed pedals so I don't need them! If you DO need one, you'll probably know it - your signal will become dark, lifeless and weak with all the unbuffered effects you're going thru.
Quote from: Antero on November 21, 2006, 06:59:15 AM
Why is it that certain fuzzes don't get along with buffers?
Some older fuzzes rely on loading down the guitar pickup with a low impedance to get their sound. If you put a buffer in front of them, you isolate the pickup from that loading.
wow....thank's to all the reply-explanation.....very helpfull.... :icon_biggrin: :icon_biggrin: :icon_biggrin:
Ben N,
here's what i have, and the order in the chain is not fix, it can be change to my taste:
all made by me....ALL TRUE-BY-PASS...
BSIAB2, shematic from GGG
BLUE MAGIC, schematic from GGG
BIG MUFF, schematic from GGG with some mod and fuzz
EQ 10 band, schematic from GGG (6 band modified)
ROSS/DYNACOMP compressor, shcematic from GGG
SHECHO, schematic from GGG
and to be finish:
ELECTRIC MISTRESS 18V(NON-DELUX), schematic from free-info-society
CORRRRAL CHORUS (boss ce2), schematic from tonepad
and i'm thinking of building a volume pedal, but i'm not certain, since they tcheap to buy....
has you see, i'm a fan of pink floyd... :icon_wink:
my guitar is a Godin sdxt, my amp is Marshall valstate avt2000 ( BTW i don't really recommend this amp)
but i didn't finish my board, and my friend maybe want one....so i want to make it versatile, so if a change guitar or amp, i don't have to change everything...
and it have to be usefull on stage and studio, cause me and my friends might be doing some show and make some record in studio...
so Ben N, what is your opinion , should i put a buffer at the main-input and a preamp/opamp at the end, i'm thinking on putting the preamp/opamp on somekind of switch to by-pass the preamp if not needed....
what do you think?
bent
It looks like being verbose has gotten me tagged as some kind of expert. ;D That is not even close to being true; I was just trying to share some general guidelines that might help you.
I can only suggest that, since all your pedals are TBP, and as far as I can see all of them are pretty well-behaved designs, you may not want or need anything in front of them. In fact, buffering the input of something like a Big Muff may change its tone (not sure). You might want to read that Cornish article for a different opinion.
However, there is a matter of the added capacitance that your cables, as well as all those jacks and possibly interior wiring and pcb traces in all those pedals, may add, which may also be robbing you of highs. Mark Hammer has often suggested this test for cable/pedal capacitance: Play your guitar through the shortest cord ssible straight into the amp, the, without changing anything on the guitar or amp, run it through your pedalboard (everything bypassed) and normal length cables. Chances are there is a difference. A preamp at the beginning of the pedalboard to boost your signal may help reduce the effect of cable capacitance; just make sure it is low noise (because all your gain devices, especially the compressor, will boost noise), and carefully calibrate the level so that you don't end up ovrdriving your chorus and EM.
As for a preamp at the end, it depends on how you play. You certainly have enough boost built into your other pedals (fuzz, overdrive, eq, compressor are all specialized preamps, after all) for soloing, but you may want JUST a flat boost in addition. As a Gilmour fan, you may want some kind of a tone-shaping boost, similar to his Rangemaster, Orange Treble&Bass boost or on-board EMG mid-boost (different periods, I know), but you can probably approximate those with the equalizer. Some boosters are especially good at slamming the input of a tube amp (like DG's Alembic preamp), but I don't know if that is something you want with your Valvestate.
But you know what? These things are so simple that you ought to just try them out, and TYE (trust your ears).
Ben
Quote from: Ben N on November 21, 2006, 12:55:41 PM
But you know what? These things are so simple that you ought to just try them out, and TYE (trust your ears).
Ben
i think i will do that, i'll build both and try it at different place.....i'll post the result when done...
thank's
bent