Infinity: an universal guitar preamplifier!

[DSV]

Wow, thanks! 

I may make some modifications on the output filters, since treble and bass are always roughly at 75%, and I'd like them centered for a better pot range. Furthermore, in the last 20% of the rotation the bass pot shifts the frequency of the treble one, resulting in a presence loss (this is because the Baxandall is simplified). However, if the previous mod is done, there will be no big need to change the tone controls. And what's good, is that the previous mod can be done simply through a value swap !

Once it's tested, I'll post it.

New sample: Three little pigs 
I fooled around with Audacity this time, by adding some:
- reverb, in the synth-like parts;
- compression, in the bass-like part;
- equalizing, for the "delay effect": one guitar part was copied, delayed i time and then equalized for treble loss.
Compared to the original, the guitar part has too much treble and distortion, it was with my setting for "Have a cigar", nothing that the harmonics and gain pots cannot handle.

[DSV]

Little update!

Here is the block diagram for a 1U Rack project, with 3 channels (the 1st with modes "normal" and "boost").


I will start it in 2-3 weeks, and will also post some mods for:
- the output filters of the distortion section;
- the bass boost in the pre-EQ for a typical Marhsall response.

[mikkemato]

what op-amps/transistors are the U1 and U2 in the schematics?
and (stupid question but) does this work as a preamplifier before a "real" amp?
And, how much did it cost to do this in total?
Aaaand, have you tried contacting the output to speaker/headphones? Does it have enough power in the output to make some sound(without extra amplification), enough for practising etc.?

-Peace.

[mikkemato]

Id have a challenge for ya, if youre interested. Please read to the end even if you dont want to do  this.
try to re-create this sound.
More specifically, the sound thats played with the 7-string after he has played the white six-string and the other distortion first, then played through the clean  channel of the amp with the 7-string(Did i express myself a bit complicated?I mean the sound at 05:31->little while later)
And with the EQ's of your preamp, it would of course be nice to hear the sound before its distorted, and why not the other distortion sound too
Of course you dont have to do any of this, but id be happy If you did.

[DSV]

Opamps are all Tl07x series: TL072 for the dual, TL074 for the quads.

I haven't tried Infinity as a preamp with a traditional speaker cabinet: my Vox AD30 does not have an fx loop  Furthermore, the eq settings would be different for each speaker. However, it is possible to modify the output filters, and in particular the bridged T network (page 3 of the schematics) for optimal post-eq control range.
I tried it as a distortion, but it did lack harmonics imho, even with the cab sim set for the maximum cutoff frequency. I think a switch bypassing it would solve the problem.

About the cost, it was roughly 75€:
- 10 € for the PCB
- 10 € for onboard components
- 20 € for offboard components (pots, leds, jacks, switches, wires)
- 15 € for the box
- 20 € for the knobs (could have been 10 €, but I wanted those cool, small, little aluminium knobs)
(you could count also the 0-18V adapter, but that can be replaced by voltage doublers ... 5€ more)
For a multi-channel version in a rack, I would say 100-150€ depending on the features, the PSU etc.

I would like to take the challenge, but youtube says I cannot see the video in my land !?!?!? Do you have any other link, or title?

Finally, there were some requests for a parts list, now I have the time to make it. I will also post about how to mod the output filters for optimizing the control range.

[mikkemato]

thats wierd!
ill post you three links to the vid, one to youtube(the very same i linked before, it should be) and the two others to some other places. all found with video.google.com
all (should be)high-quality
http://www.youtube.com/watch?v=WrBLnB3ze5Y&hl=fi
http://www.wat.tv/video/steve-vai-jemini-distortion-121rl_u4o5_.html
http://www.veoh.com/browse/videos/category/music_rock/watch/v15936427nP2BP9SP

[DSV]

Must be some weird stuff from youtube and copyright issues Anyway, the second link works. I'll add some reverb and delay with Audacity in order to have a chorus-like effect, as there is in the video, though I will also post the raw sound. Tomorrow, though ... it's 1AM here 

[kurtlives]

Looking forward to the final revisions of the schematic/layout.

[DSV]

Here are the samples:

The distortion (by re-listening it, i find there is too much mid content, nothing that the eq cannot scoop though)
http://www.4shared.com/file/96848110/e9dbfb50/inf_gemini1.html
And a bit of noobish guitar playing with distortion 2, something like distortion 1 and clean:
http://www.4shared.com/file/96848265/d4b62741/inf_gemini2.html

[solderman]

Hi
A very impressive an good sounding project. And you seam to be a cruel axe slinger too.


But even more impressive is that card board box with stuff you have on the pic site. Have you ordered all that stuff at one shot?
I haven't managed to use up that much in two years.

//Solderman

[mikkemato]

Wow!
Quite close!
I think there is something lacking from the tone, maybe a real chorus would make it sound a bit closer to the original, and Im not sure what else the tone might lack but stil... wow.
maybe its just that you just cant play like steve vai-nobody other than him can. everyone have their own playing sound, and that might just be the biggest difference im hearing...

was it just the  guitar-preamp-PC?
And i think i asked this before, but i dont recall getting a clear answer(might be my imperfect english skills),
so; do you think that if you put a guitar jack to be the output, could the preamp work connected to another amp, like you know as an additional preamp, before the one in the amplifier, or could it be possible to replace an amplifiers preamp with this?

[DSV]

It can be used as a preamp, before a traditional power amp, I wanted it to give an output at line level. I don't know what are the input levels for tube amps, but a gain stage at the end, or reconfiguring the buffer before the tone controls as a booster would imho resolve the issue. I was talking about the speakers in the previous post, since guitar ones do not have a linear response.

About the recording, it is guitar-preamp-PC. I think what is lacking is harmonics: Vai's distortion has a pretty loose bottom end, but is tight in the mids and highs. I had to find a compromise between boosting the lows on the pre-eq and loosing presence/clarity on the other frequencies, since the pick-ups on my Epi V are pretty muddy (they have more of a bluesy soudn than a harmonic-rich content).

And for sure I cannot play like Vai 

EDIT:

Hi
A very impressive an good sounding project. And you seam to be a cruel axe slinger too.

Hi!
Indeed, I torture my guitar when playing ...  Hopefully not the neighbors ears, since I paly direct on the pc, with earphones.   Seriously, I'm flattered, thanks!

But even more impressive is that card board box with stuff you have on the pic site. Have you ordered all that stuff at one shot?
I haven't managed to use up that much in two years.

//Solderman

Cardboard box? Pic site?  Have you got a link?

[kurtlives]

So are you happy with the project now, or will revisions be made?

[DSV]

I still have got to modify the bridged T in the output filters. I'll do some tests next week.

[solderman]

Cardboard box? Pic site?  Have you got a link?

I think I missunderstood the Image Shack site logic. I missed the "Image like this one" text ant thought this was yours



//solderman

[.Mike]

I think I missunderstood the Image Shack site logic. I missed the "Image like this one" text ant thought this was yours

//solderman

Heh... uhh, that would be mine. It's part of my long-term plan to build a multi effects unit, and is completely unrelated to this topic here. PM me and I'll tell you all about it, or maybe I'll start a topic once I start making real progress.

[petemoore]

  I can't believe none of you guys think you can play like Vai.
  It's not that hard, all you need to do is practice, and that box will teach you everything !
  Via is always a real treat to watch, overcomplicating everything every time.
  He understands well how to polish comedy routines, I enjoy the reserve he seems to have the capacity to keep at all times.
  If I was into dude-noodling like that, I'd want to be the one...he does some super charged A-1 noodling, thats' for sure, tells a guitar-story every time, all the drama and action you could possibly desire, it's fun to be entertained by the vids he's in.
  Steve really works that mug too, very expressive.

[DSV]

  Here is the parts list of version 1.1: http://www.4shared.com/file/98295463/c206ba91/infinity_BOM.html

I have decided not to change the output filters, as after some testing, I like how they are ... but I will post some info on how to modify them to your taste.

[rotylee]

thank you

[ConanB]

Definitely keep us posted on the 1U version. I have an old 1U computer network hub that I was going to butcher for it's enclosure, and this does seem like the project to use it for...