Infinity: an universal guitar preamplifier!

[Jered]

  Hands down the most entertaining Vai video to date.  You've got to see and hear this!
   http://www.youtube.com/watch?v=nMXlaMiRxDs

[Jered]

.....and three times as good on the triple neck
    http://www.youtube.com/watch?v=aiXR9ggRdFI

[mikkemato]

The problem with those vids...(in my opinion/IMO) Theyre funny for about half a minute.... then they get boring.

[Paul Marossy]

No, this video is a real loser: http://www.youtube.com/watch?v=9IrWyZ0KZuk
And this one even worse: http://www.youtube.com/watch?v=6CfEaSmdtGU&feature=channel

Seriously, I think some of Vai's tunes make great orchestral pieces.

[Ben N]

OT, but sorry, I am not convinced. Vai's self-important mugging looks to me like a lobotomized mockery of his infinitely more creative ex-boss. FZ is probably rolling over in his grave, saying, "I should have never taught that shmuck the difference between an oboe and a timpani!" Sure, I'll never be 1/100th the player he is, but ability never justifies out-and-out wankery, which is what I think Vai is all about. That masturbatory bit with the whammy makes me think about the contrast with, say, Adrian Belew--another unfavorable comparison IMHO.

[Paul Marossy]

OT, but sorry, I am not convinced. Vai's self-important mugging looks to me like a lobotomized mockery of his infinitely more creative ex-boss. FZ is probably rolling over in his grave, saying, "I should have never taught that shmuck the difference between an oboe and a timpani!" Sure, I'll never be 1/100th the player he is, but ability never justifies out-and-out wankery, which is what I think Vai is all about. That masturbatory bit with the whammy makes me think about the contrast with, say, Adrian Belew--another unfavorable comparison IMHO.

I agree that Vai sometimes gets a little crazy with the whammy bar, but I think he is a very expressive player, and that appears to some people to be "wanking" and "unmelodic". I suppose I could be accused of the same things as well from anyone who has heard all of my tunes.

Whether you want to acknowledge it or not, he is a virtuoso. Even Frank Zappa said this of Vai. I feel that Frank Zappa wasted his talent on writing tasteless songs, he could have been SO much more. I did enjoy his 3-album set "Shut Up And Play Yer Guitar", though. In those moments he shined for a fleetng instant. And he always had the greatest gnarly guitar tones.

[Ben N]

Whether you want to acknowledge it or not, he is a virtuoso.

Agreed, absolutely. I don't think this contradicts anything I said, although we obviously disagree (respectfully) about the artistic merits of Vai's music-making, as opposed to the technical quality of his playing. BTW, Paul, from what I have heard of your playing, I would not apply any of the above criticism to you. FWIW.
I should also note that while I generally hold shredders suspect, there certainly are many who I think are quite worthy.

[Paul Marossy]

Whether you want to acknowledge it or not, he is a virtuoso.

Agreed, absolutely. I don't think this contradicts anything I said, although we obviously disagree (respectfully) about the artistic merits of Vai's music-making, as opposed to the technical quality of his playing. BTW, Paul, from what I have heard of your playing, I would not apply any of the above criticism to you. FWIW.
I should also note that while I generally hold shredders suspect, there certainly are many who I think are quite worthy.

Woo hoo! I'm off the hook. Whew. 

That's cool. I don't feel that everyone has to agree with my viewpoint, and vice versa. That being said, I have to be in a certain mood to listen to Vai's music. And the same for Yngwie Malmsteen. While I can get into his music, and can appreciate what he does, I can only take it for so long before it wears me out! 

[off1]

Hey Daniele...

  This Infinity preamp looks great!      Now I have a couple of questions for you.



I am planning on building my own combo box using Infinity as a preamp and adding a TDA power amp (I'm still trying to decide between a 35W TDA2052 and a 70W TDA7294).

So my typical application would be:

          Guitar  -->  Infinity  -->  Power amp


I know I should have no problems with that. The thing is, sometimes I will also want to stick my 'ZOOM Digital FX processor' between the guitar and the preamp. Like this:

          Guitar  -->  Zoom Processor -->  Infinity  -->  Power amp



So my questions are:

1. I know the Zoom Processor already sends a line level output signal, which is going to be connected directly to the Infinity preamp. Will I burn or overload the preamp or is it Ok to do that?

2. If the above is ok, I will still want to use the Eq features of Infinity, but bypassing the distortion in order to leave all the distortion process to my digital box. Is there a way to add a bypass switch for the distortion section and leave a clean preamp? (remember, I still want to keep the Eq)



THANX!

[DSV]

Hi off1,

Is your processor one of the Zoom G1 -> G9.2tt family? If so, you can set the output level appropriately. A too great level will not fry the circuit, but will cause distortion in the gain stages.

If the Zoom will be used for distortion, this is the signal path I'd suggest:
Guitar -> Zoom -> Infinity post-eq (basically from the buffer opamp in the Baxandall tone control).

The pre-distortion equalization part would be redundant, unless you would use it to shape the distortion grain as in the Infinity module:
In this case I'd do
Guitar -> Infinity pre-distortion eq -> Zoom -> Infinity post-eq (basically from the buffer opamp in the Baxandall tone control).

In both these cases the distortion section will not be used, which means you can work with higher level signals without having to worry about distortion. The power supply will just have to have enough headroom, and I think anything more than a +/-9V will be OK.

---

BTW, since I bought a bass guitar and am building a pre for it, the 1U project is gthering dust and lacking funds. What I decided is to start the study of a version 2, which will have less controls, more similar to those of a guitar amp, but as effective as the old ones. I'll keep you informed as soon as the specs will be a tad more defined.

[off1]

Daniele,

  Thank you very much for your quick reply. I will use your preamp from the post-eq when I connect the ZOOM box.

I have a slightly older ZOOM box, the 606, but I guess I can use the PATCH LEVEL control to adjust it's output volume.


Really, Thanks a lot!

This is, at first sight, the best project I have found online (and believe me, I've been looking around a lot).

[adrs]

Hi,
I'm just completing items for this project, bacause it just seems to be the solution i was looking for for ages, sounds great!.
I presume this preamp has some kind of cabinet simulation in its circuit, videos are recorded drect from its output?
I'm curious about one thing. I would like to make additional outputs for using it in this cases:
- Preamp in front of poweramp (so that i could just connect the output somewhere in the middle to bypass the cabinet simulation)
- overdrive (possibly bypass some filters  and use only the distortion to feed the preamp (use it like BSIAB ))

In fact i would make it like that:
1. standard output
2. overdrive pedal output
3. FX out (before cabinet)
4. FX return (to cabinet simulation) - maybe useless but i want to check this out

Maybe the cabinet simulation this is somewhere in the middle, so i would make just a switch bypassing it. I'm just not understanding the circuit in 100%, because i'm rather novice.
Is it somehow possible to do it like i presented? Or just make some switches for this?

[adrs]

So I created it. You are the one to encourage me to do my first electronical device!
I'm still waiting for j201 and 2n5457 to arrive and searching to substitue ceramic caps.
BTW You need 14-pin socket not 16 - a small mistake in Bill of Materials.

[DSV]

Hi adrs!

Nice looking PCB, I hope the project turns out well  Was it you who left a comment about sourcing the JFETs on the youtube video? I wanted to answer, but somehow youtube does not post the response  Anyway, two excellent internet shops in Europe are www.banzaieffects.com and www.musikding.de , they both have most of the parts used in DIY projects.

As for the mods you are proposing:

In fact i would make it like that:
1. standard output
2. overdrive pedal output
3. FX out (before cabinet)
4. FX return (to cabinet simulation) - maybe useless but i want to check this out

you can either:
- use a switch for bypassing the cabinet simulation, as you suggested (use a DPDT, take the signal from the point labeled Harmonics 1-2A on the layout)
- use a signal splitter (taking the signal from the aforementioned point, followed by a simple opamp used as buffer; from the opamp output, you can send one wire to the "FX out", the second to the cabinet simulator).
The option 4 you mention is useless IMHO, since you are alread post-distortion.

BTW, thanks for pointing out the mistake on the BOM 

[adrs]

Thanks.
I'm real newbie to this stuff, so don't worry if i will not be able to run this device i will just start to make something easier and not bother you for eternity
I have  50 j201 and 30 2n5457. Do I have to check the Idss now and match them with values on BOM? Or something more?
I'm still not sure about grounding. Do I think right: Ground is conected to the board from input jack socket, which is connected to the metal case, which is connected to the ouput socket.

About the trimmer... I presume that it is some kind of bias thing, but the question is: should i set it in some kind of predetermined position before connecting power or just only play with it afterwards?
Could you tell me if there is something more to do before powering it. Thanks in advance.

[DSV]

I gave the JFET characteristics just because I wanted to remember them for future reference (most of the sheets of paper I write important stuff onto get either lost or carelessly thrown away - by me  ). There is no need to select them, the distortion may sound different, but not better or worse. I'd say that you test combinations: in some BSIAB builds J201 are replaced by 2N5457 and vice versa.

Biasing the 5th FET does not require setting the pot to a specific resistance before powering up, just make sure it works 

If I understood correctly your question about wiring, you are right: the input jack has 2 connections (signal and ground to bord), whereas the output has only one (signal) and the ground connection is provided by the metal case (you can see it from this photo http://img27.imageshack.us/i/wiringjack.jpg/ ). Of course the jacks must not be plastic ones 

[adrs]

Great, i got it working...
Is the polarity right in the psu schematics? Bacause i had problems with it - highly possible it is just my fault.
I have noticed that i have a small fuzzy clipping while i hit strings harder...
Is it due to the trimmer which i haven't set yet? Could you tell me how to use it ? Do i need osciloscope?
thanks!

[dschwartz]

set the trimmer first

[rotylee]

is there a pcb for the pots?

[DSV]

Hi rotylee, sorry for answering late ... between exams, no internet and moving I didn't have much time for DIY.

There is no PCB for the pots, I used some veroboard, very good for having a stable wiring base without haing to etch anything.