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.
(http://img50.imageshack.us/img50/7730/lxh2fender01lr4.th.jpg) (http://img50.imageshack.us/my.php?image=lxh2fender01lr4.jpg)
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 ...)
Looks great. Any reason not to use a 9v battery to power it though?
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.
Since an alkaline 9v battery is normally 600mah or more, and your circuit should fall in the 50-60ma range (lets call it 60), that would mean 10 hours or so of operation and no sag. I'd give it a go, if not for anything else, for testing purposes.
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.