Unity Gain Buffer and pedal performance

Unity Gain Buffer and pedal performance

Postby Boston_Patriot » Thu Feb 09, 2012 6:55 am

Hi!
I'm getting a new axe and I want to do this right. Sorry if this has already been answered, but I couldn't seem to find it...I have two questions regarding the OBEL and unity gain buffer. With a UGB and all true-bypass pedals...

1) I've been reading that the low impedence signal can hurt (or, at least, significantly change) the performance of pedals, especially OD and distortions. Is this the case? My band also plays stuff like Phish and Pink Floyd, to give you an indication of the amount of pedals that will be in the chain. I'm concerned about performance of these with a low impedance signal.

2) With no pedals active, being true bypass, I obviously see no problem- low impedence all the way to the amp. My second question is when an effect is used, what impedance is the output from that pedal? Is it still low? Does it depend on the pedal? Do I need another buffer after the chain? I'm assuming most people here have their Mutron at the end of the chain to deal with this? I have a 3Leaf Proton which is true bypass, not buffered. Again, do I need a buffer at the end of the chain?

Thanks
Boston_Patriot
tiger
tiger
 
Posts: 22
Joined: Wed Jan 25, 2012 7:22 am

Re: Unity Gain Buffer and pedal performance

Postby USBLUES » Thu Feb 09, 2012 7:37 am

Sorry not to answer the question but wanted to add to it
I'd like to jump in here and add.......i have Qtorn, some other analog effects MXR DIST+, BOSS chourus, TS, and then a DL4 is the ELoop. So some ofthese effects have buffers of their own, like the Qtron and i think the DL4, then i have WALDO's buffer in the AXE, what does buffer into buffer into buffer do to tthe signal? its gotta kill it or really mess with it right? sorry if this is a hyjack hoping just to add, this is a great topic, oh and all this is going into a digital modling amp to boot, this not how Big Jer intended it :?:
USBLUES
Pigpen
Pigpen
 
Posts: 142
Joined: Tue Oct 13, 2009 10:54 am

Re: Unity Gain Buffer and pedal performance

Postby Boston_Patriot » Thu Feb 09, 2012 8:05 am

From my research it seems that too many buffers (I've heard >3, but I don't know) can really add a lot of noise to the signal. Basically, people seem to be saying that too many buffers is not good.
Boston_Patriot
tiger
tiger
 
Posts: 22
Joined: Wed Jan 25, 2012 7:22 am

Re: Unity Gain Buffer and pedal performance

Postby Jon S. » Thu Feb 09, 2012 8:41 am

In the other currently active buffer thread, I posted a link to Analogman's FAQ which answers your questions.
"For me, I think the only danger is being too much in love with guitar playing. The music is the most important thing, and the guitar is only the instrument." Jerry Garcia
User avatar
Jon S.
Senior Member
 
Posts: 1304
Joined: Wed Apr 30, 2008 12:34 pm

Re: Unity Gain Buffer and pedal performance

Postby SarnoMusicSolutions » Thu Feb 09, 2012 9:50 am

I've found that the only pedals that suffer from having a buffered guitar signal are the true Fuzz style pedals, like a Fuzz Face or Tone Bender or similar. These discrete fuzz type circuits sound their best when they can have a direct connection right to the guitar's 250k or 500k volume pot and the pickup coil itself. The inductive interaction with the pickup and the impedance and series resistance interaction of the pot are part of that classic Fuzz experience. Regarding all the other overdrive pedals we often use, MXR Dist+, Tubescreamers and the gazillions like those, etc. Those are already self buffered in a way. Even if they are the true-bypass types, the first device in there is an opamp and they simply don't really care whether your guitar is buffered or if a buffer comes before it. So regarding our OBEL/Garcia setups with the tiger buffer on board, I'd say the only pedals that suffer in this setup are the vintage "true" fuzz types. There are some fuzz pedals that have taken this into consideration and they are more happy with seeing a buffered signal coming in.

And I agree, too many buffers is not a good thing. Basically that's because you're just stacking too much crap into the signal path. It's like looking thru one pane of glass is fine, especially if it's a good quality glass. But if you stack 7 panes of glass and look thru them, it's gonna take something away from the clarity or purity. With the buffered OBEL setup, having true bypass pedals is a good thing. With non-buffered guitars, it's good to have at least one decent quality buffer pedal in the chain, preferably close to the guitar, the first or second pedal. Boss pedals actually are decent/adequate buffers. There are better ones though. The Waldo/Tiger clone buffer is actually a VERY high quality buffer amplifier circuit with audiophile grade capacitors and resistors and a high performance opamp. It's hard to beat that buffer with regards to sonic quality. If you're looking for a pedal buffer, consider some of the boutique clean boost types and just set them for unity gain. There are some nice ones out there.

B
... and it's just like any other day that's ever been...
SarnoMusicSolutions
Senior Member
 
Posts: 1035
Joined: Tue Jan 27, 2009 6:15 pm
Location: St. Louis, MO - USA

Re: Unity Gain Buffer and pedal performance

Postby gr8fullfred » Thu Feb 09, 2012 10:56 am

The way I look at it is like this:

Guitar pickups are high impedance output. This limits the pickups ability to drive the low impedance cable to the next block in the electronic path, whether this be the gate of a tube in an amp or a device (op amp or transistor) in a pedal. What is also important to remember is that the buffer is only driving the signal into the FIRST device that is receiving the signal. The OUTPUT section of the FIRST device is driving the signal furthur down the line. The buffer in the guitar is only driving the signal to the first device, then each device is driving the signal to the next device.

Where the multiple buffers in the chain might negativity effect things is if you do not have true bypass on each of your effects. If the signal is going through 5 pedals that are not true bypassed, and all are in the "off" mode, then your signal is going through 5 input sections and 5 output sections of those effects. This can lead to some degrading of the guitars natural sound, compared to just plugging in the guitar to the amp (regardless if there is or is not a buffer in the guitar). So my advise here, and I strongly recommend this, is to have your effects true hard wire bypassed.

When using my favorite guitar, it sounds so much better when 100% clean going directly into the amp (hard wire bypassing the effects). So much so that I built a very simple hard wire effects loop box that true bypasses my pedal board. This is a simple device that you could build for pretty cheap, and I think is well worth it if you ever play your guitar straight into the amp with no effects on.

I will post details on the true bypass stomp box later, show you some pictures.
User avatar
gr8fullfred
Jerry
Jerry
 
Posts: 463
Joined: Mon Dec 21, 2009 7:29 pm

Re: Unity Gain Buffer and pedal performance

Postby SarnoMusicSolutions » Thu Feb 09, 2012 11:04 am

I agree with this true-bypass benefit, just as long as the guitar is buffered or there is at least one buffer pedal early in the path. Without the buffer, the pickup itself is handling the job of driving the signal thru all of that cable capacitance, box capacitance, switch and jack contacts, etc. The low-Z of a buffered signal just doesn't care about all that stuff. It pretty much ignores the cable and capacitance and many switch and jack contact points and passes thru un-hurt.

A high-Z pickup output is VERY vulnerable to all these things. High Z is going to see your cable as a tone-sucking capacitor. Low-Z doesn't react to cable capacitance in the lengths we use. I may have restated what you just said, but anyway, I agree.

This is what's cool about Garcia's rig. The on-board buffer creates the low-Z signal right out of the gate. Then the signal path goes thru a true-bypass pedal router, so when an effect is off, it's true-bypass. When the OBEL is bypassed, then the guitar signal goes right to the amp/preamp. It's ideal. Also a key factor in the equation is how the low-Z buffered signal allows the guitar to use a 25k volume pot. This low value pot means that the tone remains consistent at any volume setting. You can't use a 25k pot without buffering the pickups.
... and it's just like any other day that's ever been...
SarnoMusicSolutions
Senior Member
 
Posts: 1035
Joined: Tue Jan 27, 2009 6:15 pm
Location: St. Louis, MO - USA

Re: Unity Gain Buffer and pedal performance

Postby TI4-1009 » Thu Feb 09, 2012 11:20 am

gr8fullfred wrote:So much so that I built a very simple hard wire effects loop box that true bypasses my pedal board. This is a simple device that you could build for pretty cheap, and I think is well worth it if you ever play your guitar straight into the amp with no effects on.


...sorta the same as the third mini-switch on Jerry's guitars: bypass the whole ob effects loop and go straight to amp.
"Do not write so that you can be understood, write so that you cannot be misunderstood." -Epictetus

First show: 8/16/69 (Woodstock)
Last show: 3/19/95 (Unbroken Chain breakout)
Member of the Four-Decade Club
Charter Member, President & CEO of OAD (Order of the Ancient Deadheads)
User avatar
TI4-1009
Senior Member
 
Posts: 1349
Joined: Fri Aug 20, 2010 6:27 am
Location: Upstate NY- Toodaloo

Re: Unity Gain Buffer and pedal performance

Postby gr8fullfred » Thu Feb 09, 2012 11:57 am

Yes Jerry's OBEL does the same thing. I think that Jerry's (and let us remember here that the OBEL is Jerry's invention) OBEL is the single most technically significant thing that Jerry contributed to the guitar, hardware wise. This is a novel and significant invention, thanks Jerry! Jerry's OBEL is just that, it is an On Board Effects Loop. Might also be thought of as OGEL On Guitar Effects Loop.

My box is not On Board, but its a quick and easy way to bypass your effects. An additional benefit of the true bypass effects loop is that you can have more than one effect on and in the chain when you kick it in. For example you can go from 100% clean straight guitar to having the Envelope Filter AND the delay on with the push of just one button on the effects loop box. That is a kinda nice feature. You can go from 100% straight clean guitar to your whole effects chain in there with one "click". Try that with a regular pedal board.
User avatar
gr8fullfred
Jerry
Jerry
 
Posts: 463
Joined: Mon Dec 21, 2009 7:29 pm

Re: Unity Gain Buffer and pedal performance

Postby Boston_Patriot » Thu Feb 09, 2012 4:13 pm

Thanks Guys!

Gr8fulfred: I am (re)building my rig after almost 10 years of essentially not playing (played a TON for about 15 years before that, including a degree from Berklee). My point is...I am buying ALL new effects, all of which will be boutique- Analogman, HBE, 3Leaf, Wampler, EHX, etc. Are these pedals, which appear to be "high end", have TRUE hardwire bypass, or will I benefit from hardwire loops?? Please, let the cost of this stop going up!! :shock: Oh, and I'll just switch off the OBEL if I'm not using ANY effects.

B: It appears I will definitely need a buffer at the end of the chain to return to the OBEL and go through the 25k vol pot, right?? Thoughts on the Wampler Clean Buffer, or should I just go with the master: Waldo!

So psyched to start playing Dead tunes again! And Allmans, and Steely Dan, and Phish, and Floyd, and Widespread, and...and...
Boston_Patriot
tiger
tiger
 
Posts: 22
Joined: Wed Jan 25, 2012 7:22 am


Return to Jerry Tone

Who is online

Users browsing this forum: No registered users and 3 guests