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Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Solid State Amplifiers => Preamps and Effects => Topic started by: newbiediy on March 02, 2012, 03:33:41 AM

Title: Please make correction on my schematic: Preamp of Red Circuit's 10W Guitar Amp
Post by: newbiediy on March 02, 2012, 03:33:41 AM
I came across with this guitar amp schematic: http://www.redcircuits.com/Page52.htm. I am interested in making a preamp based on it.
Obviously I don't know if I'm doing it wrong, so any correction would be VERY APPRECIATED.
Can I power it with a 9V battery?
Title: Re: Please make correction on my schematic: Preamp of Red Circuit's 10W Guitar Amp
Post by: J M Fahey on March 02, 2012, 07:29:02 AM
Looks somewhat right although the tone control will have almostnil effect.
Don't know whether 9V will be enough.
Depends a lot on which Fets you get.
In general lines Red Circuits isn't a reliable source.
Title: Re: Please make correction on my schematic: Preamp of Red Circuit's 10W Guitar Amp
Post by: newbiediy on March 05, 2012, 03:24:57 AM
I am wondering with C29 (47u). Usually the orientation is the other way around ie. the (-) side connects to power section. Any thoughts?

Is there any unnecessary parts?

Is Red Circuit really that unreliable? Actually I'm planning to make some of their circuits. Guess I'll have to reconsider.
Title: Re: Please make correction on my schematic: Preamp of Red Circuit's 10W Guitar Amp
Post by: J M Fahey on March 05, 2012, 07:57:33 AM
If you wish, post the schematics here first.
Title: Re: Please make correction on my schematic: Preamp of Red Circuit's 10W Guitar Amp
Post by: Loudthud on June 27, 2012, 02:32:35 PM
C9 orientation depends on what the following stage looks like. It's correct for the circuit you took it from because the following circuit has a positive voltage on it. Circuits with JFETs need to be tweeked to run properly, usually because you can't get the exact parts the designer used. This circuit would run better on 24V to 30V. The circuits at Runoffgroove make better DIY projects because they include trim pots and instructions needed to get them working without a lot of messing around. You will need a DVM to measure voltages.
Title: Re: Please make correction on my schematic: Preamp of Red Circuit's 10W Guitar Amp
Post by: newbiediy on July 23, 2012, 02:49:58 AM
Thanks for the replies. I guess I just don't have enough resources to build fet preamps. Don't have DVM and required skills.  xP
The most comfortable way for me would be op-amps then...
Title: Re: Please make correction on my schematic: Preamp of Red Circuit's 10W Guitar Amp
Post by: AlbertH on July 30, 2012, 05:43:23 PM
 :(  You're going to have to spend some money - you really do need a DMM.  It doesn't have to be an expensive one, but it is essential.  It will save you blown components and frustration!
Title: Re: Please make correction on my schematic: Preamp of Red Circuit's 10W Guitar Amp
Post by: joecool85 on July 31, 2012, 04:19:25 PM
Quote from: AlbertH on July 30, 2012, 05:43:23 PM
:(  You're going to have to spend some money - you really do need a DMM.  It doesn't have to be an expensive one, but it is essential.  It will save you blown components and frustration!

Yeah, while it isn't technically required, it certainly makes life a whole lot easier.  I went through a couple units over the past 10 years and my favorite is my current Craftsman one.  I like to have replaceable leads and a DMM that can do up to 10A or so as an ammeter (it has come in handy on more than one occasion), so this one fits the bill.
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