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DIY Stompboxes => Building your own stompbox => Topic started by: yano on April 26, 2004, 06:06:34 PM

Title: how to build a pre-amp?
Post by: yano on April 26, 2004, 06:06:34 PM
I want to make a pre-amp for my bass (and/or other instruments) so that I can connect it to my home or car stereo.

I'm considering simply designing my own. Would it be a better bet to use something like a LM386-3 (I have one lying around) or should i just use an op-amp (the only ones I have are NE5532s).

Also, how closely could I base this off of a headphone amp?

Thanks in advance!
Title: how to build a pre-amp?
Post by: Hal on April 26, 2004, 06:58:51 PM
an lm386 is a power amp chip.... i wouldn't use it in a preamp.  An opamp would work, and so would a simple NPN boost or MOSFET boost...pretty much any "boost" is a preamp.....
Title: how to build a pre-amp?
Post by: brett on April 26, 2004, 09:16:10 PM
Hi.
Here's a good pre-amp project.
http://www.tonepad.com/project.asp?id=6
Your NE5532 would work great in this.

cheers
Title: how to build a pre-amp?
Post by: brett on April 26, 2004, 09:22:02 PM
PS You'll need to boost the bass a bit and the treble a lot to get a "normal" tone out of a hi-fi or other stereo.
Title: how to build a pre-amp?
Post by: Kleber AG on April 26, 2004, 10:05:09 PM
Hello
I must say (IMHO) that THIS:
http://www.geofex.com/circuits/Adjusticator.gif
This is the best one I've tried for this kind of aplications (preamps).

It is better with the 5532 opamps, and man the big surprise is it drives my 4x12 cab really loud for bedroom volumes and really nice sounding...

I've added a baxandall hi/lo active tone stack just before the adjusticator and it works like charm... :D  8)

Thanks a lot RG for such a great tool circuit, I believe this circuit block (adjusticator) could be used for many other things with some additions, changes etc, really powerfull thing.

I use it to drive a POWER amp with my pedals

Thanks
Kleber AG
Title: how to build a pre-amp?
Post by: Gilles C on April 26, 2004, 10:25:54 PM
I like this one.

http://www.albertkreuzer.com/preamp.htm

More parts, but quite versatile
Title: how to build a pre-amp?
Post by: RDV on April 26, 2004, 10:32:33 PM
Here's a couple of super simple preamps. One is a Blackfire stage. One is one I've drawn up out of my pea brain.

(http://img54.photobucket.com/albums/v165/rickydon/hifi_preamp.bmp)

(http://img54.photobucket.com/albums/v165/rickydon/Super_Simple_Pre-Amp.gif)

Regards

RDV
Title: how to build a pre-amp?
Post by: brett on April 26, 2004, 10:43:08 PM
Hi.
Ricky's pre-amp is a nice design, but has low input impedance.  Easily improved by swapping that 100k resistor (connecting to Vr) with a 1M resistor.
cheers
Title: how to build a pre-amp?
Post by: RDV on April 26, 2004, 10:48:28 PM
I fixed. Computer smoking. Eyes crossed. I go bed now.

Night night.

RDV
Title: how to build a pre-amp?
Post by: Kleber AG on April 27, 2004, 12:14:50 AM
Hello Gilles!

That one you posted got my curiosity...
:lol:
Have you built that?
Tried with guitar or bass?
How does it sounds?
Totally clean?

Please!
Kleber AG
Title: how to build a pre-amp?
Post by: Gilles C on April 27, 2004, 07:38:11 AM
<<<Have you built that?
Tried with guitar or bass?
How does it sounds?
Totally clean? >>>

I didn't tried it, but he had good reports a while ago from some people who built it.

I tried only the preamp part with  my guitar.

I always prefered to use JFETs in the first part of a preamp, to get more signal, then use an opamp for the second part of the circuit. And that's what he does. So...
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