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Messages - syndromet

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Preamps and Effects / Re: How to bias a JFET preamp?
« on: November 29, 2006, 06:09:32 AM »
To bias a JFET, you simply turn the trimpot connected to the power supply of the JFET. In most cases you would want to adjust it to the half of the supply voltage. If your preamp runs on 18v, you would, in most cases, adjust the trimot so that the supply voltage to the Jfet is 9V. I like to adjust the trimpots by ear. Simply plug in the guitar, get a string to vibrate, and adjust the trimpot untill you have the correct sound. There is usualy just a tiny part of the rotation that give you a nice sound without gating.

Amplifier Discussion / RobertT.....
« on: November 28, 2006, 06:15:21 AM »
Seems like Harrison Ford from diystompboxes has found this forum too. I say one of you admins ban RobertT emediatly.

Amplifier Discussion / Pictures
« on: November 19, 2006, 09:52:46 AM »
We need a picture-thread for the amps, too! Post your DIY-amps here!!
My little gem:

My stereo ruby:

Preamps and Effects / Re: Pictures
« on: November 19, 2006, 09:50:20 AM »
My little gem. The enclosure was meant for the Nelson 6w stereo amp, hence the name.

Amplifier Discussion / Re: LM1875 chipamps, any feedback?
« on: November 08, 2006, 09:34:24 AM »
I'm sorry I haven't had the chance to give feedback or contribute ( if I ever have :o) to this wonderfull comunity lately. I'm in the midle of a move, started a new job, and spend the rest of the time with my girlfriend and my baby daughter. There haven't been a lot of soldering lately, in other words.

I thought, however, that I should behave decent enough to let you know how my LE 1875 is coming along. The boards are soldered, and they look great. I also found a great enclousure, but it turned out that the inside of this bow is to small for most of the common transformers. I had one transformer that fitted perfectly, but it turned out to be broken.

That means that my amp is still in parts, and i haven't had the chance to try it yet. Right now I'm waiting for a new, bigger enclosure to be made, and I'll order a new transformer when I get my first payment. I'll let you know how it turns out when its finnished.

Ofcource I couldn't stay away from the soldering-iron, so i have built myself a little gem since the last time I posted here. It sounds great, and I highly recomend it if you want a battery powered mini amp. It sounds way better than the Fetzer-Ruby I built some time ago. I'll post pictures of the little gem in a few days.

Amplifier Discussion / The nelson 6W miracle (?)
« on: October 03, 2006, 03:32:16 PM »
I decided to do a little soldering again, and had a shot at this one:

I etched the pcb, wired it up, and no  sound at all. Only thing that happens is that the chip gets hot. Realy hot!! So I checked the pcb for shorts, checked the orientation of caps and chip and checked the PS. Same problem, so I checked it all again. I guess I have checked everything a thousand times now, and I still get nothing.

I was therefor wondering if anyone have built this, and if it worked. I've checked it against the datasheet, and it seems to be ok. Any idea what I can have done wrong?

Amplifier Discussion / Re: I found myself an enclosure.
« on: August 29, 2006, 06:13:07 PM »
Damn!!! I'm just finnished drilling my enclosure, and was about to test my transformer when it turnes out it doesent work!!! Lots of smoke and bad smell, so no I have to go hunting for a new transformer to fit in this enclosure, wich will be hard.

Amplifier Discussion / Re: Offboard wiring of stereo LM1875 amp.
« on: August 24, 2006, 10:48:47 AM »
I appriciate the help, guys!

ok, so if I got this corectly, on the original layout the only connections to Chassis ground should be from the power supply and the mains connection? But i should run all grundpoints to chassis ground to have it opperate as quiet as possible?

How important is insulated jacks? And how do I wire up a center tapped transformer?

Guess thats enough questions for now.

Amplifier Discussion / Re: Offboard wiring of stereo LM1875 amp.
« on: August 24, 2006, 01:03:20 AM »
I started a thread about grounding methods few days ago, lot's of useful info there. What are those two round things in the picture?

I read your grounding thread, great stuff. This is just a way for me to confirm that I got things right, so I don't blow the amp up, when I get to put it together. The round things are supposed to be speakers.  :o

Amplifier Discussion / Offboard wiring of stereo LM1875 amp.
« on: August 23, 2006, 04:41:52 PM »
I don't think I'we gotten the part about grounding or the way to wire up a center taped transformer right. Since English is not my main language, I have a little trouble understanding how to propperly ground the Pcbs and transformer. I therefor drew up a quick schem of how I think the offboard wiring should be done, and would love if anyone would care to comment any mistakes. I was also wondering if it is important to have insulated jacks? I forgot to add a fuse on the drawing, by the way.

In the Manual for the Lm1875 amp, it says thet Chassis-ground(CHG) should be connected to a point on the chassis.  I can't, however, find a hole named chg on my pcb's. Any help is appriciated.

Quick drawing of how I think it should be done:
My guess on the offboard wiring

Preamps and Effects / Re: Pictures
« on: August 21, 2006, 11:59:05 AM »
The Sonic Destroyer is two Tim Escobedo circuits in one box, and made to create the most awfull noises ever. It's the Thing Modulator and the Psychtar. It has a very wide range of sounds, and can produce anything from octave up, fuzz, tremolo-like effects, sitar-sounds and ring mod. It's an extreme pedal, and usefull for making extreme sounds. I love it!!

Here are a few soundclips:
Octave effect
Sitar effect
Ring modulator
Sonic destroyer in feedback loop
Playing with the settings

Preamps and Effects / Re: Pictures
« on: August 21, 2006, 10:30:41 AM »
Well, they earliest ones don't look as pro as they could have. It took a while before I learned to laquer them so that the laquer isn't grainy. But the last ones look pretty good.

Preamps and Effects / Re: Pictures
« on: August 21, 2006, 03:48:33 AM »

And a little stereo Ruby

Amplifier Discussion / Volume controls!
« on: August 20, 2006, 05:27:13 PM »
I have seen other places that people use atenuators as volumecontrols on the Gainclones. Is it possible to use a standard pot before the amp, like used on gain-controls on stompboxes? If so, what value should the pot be?

Preamps and Effects / Re: Hiwatt-based preamp
« on: August 18, 2006, 03:50:16 PM »
Two different inputs is probably a good idea, since the Brilliant input has a boost cap that I left out. I think if you follow the original Hiwatt schem with Jfets instead of tubes, you will probably have a really good preamp.

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