1st post is now updated with the .pdf version of the layout. 

I completely forgot to update this thread 

Hi rogeryu. Name's Daniele! 

Hi spraguetr! The old schems have got 2 little errors: a capacitor in the output filters, and the source resistor of the 5th jfet. I'll update the 1st post with all the new info!

Thanks for the replies, and sorry for answering a bit late ...

anyway, the opamps are 2 TL074 and a TL072. You can use other ones, such as the TL06x or the TL08x.

I recorded a few other samples, sorry for the uninspired / bad playing:
- Here for a Voxxy style.
- Here for the 2ns solo of Comfortably Numb (delay was added through Audacity).

I also did a new version of the schematics, since there were 2 mistakes in the component values:Here

Now I'm working on a tutorial, and I hope to receive my PCBs soon. I have also decided to make a full opamp version, in order to avoid the biasing and selecting of the JFETs, and enable more PSU flexibility, mostly for switching in multi-channel configurations.

Thanks!

I've finished the layout, and my PCBs will be probably made in 1-2 weeks.

About the number of pots, I would have liked to reduce it to 7 (without the bass control in the pre-equalizer), however fuzz tones and fine-tuning in the sound (especially for the samples of Scorpions and Dire Straits songs) would not be available anymore.

400 views and no comment 

Anyway, here are 2 pics of the new prototype:



A layout will be ready soon ...

:tu:

I'm not sure wether on the schematic it says 50nF or 50uF (I guess it's 50u, since it's for bass and the requency response must go very low). In any case it'll give a gain of roughly 60-65 for guitar frequencies.

About the voltage divider in the Real McTube, it really depends on what kind of amplification you use after the pre. If it's a tube power amp, large signals are going to be OK. On the other hand, if the power amp is solid state, or you use the circuit as a pedal (like the Real McTube), you have got to limit the voltage swing to prevent clipping.

If I remember correctly (I calculated it some months ago), voltage gain for tubes without the bypass caps are around 20, and you may still need the voltage divider network (maybe with another ratio). Sound was also a bit different. I'll check if I can still find the calculations, computer simulations and samples.

It's almost the same as a Fender preamp. The only mods would be replacing the 1st and 2nd cathode caps by 2.2 uF. Basically it's what Jack1962 said (2u2 caps will give a larger frequency response, mostly in the bass section - I'm not sure wether it'll make such a great difference for guitar though).

Hi all!

Enter Infinity, a guitar preamp offering great sound versatility, from clean to heavy distortion. It can be used for DI applications (in conjuction with the PA and a monitor), and for recording. A short presentation can be downloaded here.



Samples
A Youtube video of first prototype, and containing some samples (direct recording to the PC soundcard): Here!
Other samples:
- Here! for a Vox style.
- Here! for Pink Floyd's Comfortably Numb (delay was added through Audacity).
- Here! for "Two minutes to 2h in the morning" (since I recorded it at 2AM), Iron Maiden style.
- Here! for a Plexi style.
- Here! for "Thunderstruck", AC/DC style
- Here! for "Sharp Dressed Man", ZZ Top style.

Files
The latest schematics of Infinity (V1.1) are here!
And the parts layout:
The .pdf format is here!

Building pictorial

Here is a .zip file with all the photos ( size 4,73Mo).

The prototypes:


The final version:


Enjoy! 

I tried powering the preamp with batteries today, and the with 2 MAX1044 in parallel. There was no great change in the sound (it seemed to distort a bit less). I think the sag effect is not that important with only 1 voltage doubler, when using the preamp alone, though it adds something to the tone which I like. It did change when I used my distortion pedals in front of it, because I usually use them in order to push the preamp. With 1 1044 chip the sound became too blurry, but it was definetly better with 2, or the batteries.

It's a tough decision: 1 or 2 voltage doublers ?

I tried doing the mods on the site, i liked the mid boost one; the bite switch didn't have a great effect with the pre alone, it became more significant on the attack with distortion. I like the silicium diodes more than the LEDs (I guess i didn't get the right ones ...).

Then the whole thing quit working ... I think a component may have fried (they are quite old), or the connections in the board are starting to get defective.

I think a battery wouldn't last long.
Datasheets state that for each opamp, a supply current of about 1.5 mA (2.5 mA max) should be used, which would be 1.5*14 = 21 mA (30 mA max). And this is just for the Fender part (the Marshall sim has something like 14 other opamps)

This makes me wonder how the MAX1044 can supply the whole Fender preamp. On the datasheet it says that it can supply 10mA max (with a 0.5V voltage drop). I think there is some massive SAG going on when it  is working (it distorts pretty much!). I hope to get a new multimeter soon ...

Meanwhile I'll try adding another voltage doubler circuit in // with the 1st one, to see if it has an impact on sound.

Hi all!

I am new to this forum (and a tad more experienced in DIY, but not that much).
My current project is to build an LXH2 preamp (both with Fender and Marshall sims).
Schematics are here: http://home3.netcarrier.com/~lxh2/

I tested the 1st one on, well ..., my testing board.

Messy, but it sounds tasteful, and has surprisingly almost no noise (sometimes it oscillates a bit, which I think is due to a badly linked ground somewhere).

My question is about powering the circuit. I am using a 200mA 9V DC regulated PS, and I get a +/-9V voltage using the circuit on Geofex ( http://www.geofex.com/ - in the circuit sweepings section). This is just for test purposes, and I don't know whether it'll be able to power both the Fender and Marshall sims ... my multimeter is dead, so I can't check current consumption! But it is surely a simple circuit, and safe too.
Would it be better to replace it with a more 'consistent' power supply?
Is it possible to build a PS with a transformer and rectifier diodes / filtering on veroboard or perfboard, or would the current in the tracks be too 'strong', making them and components too hot? (I can't make any PCBs at home, and there are no shops in the city who do it).

Thanks !

(BTW, sorry about my English, I'm still learning ...)