TheGreatWhiteDope Posted May 15, 2007 Report Share Posted May 15, 2007 (edited) I was looking around at schematics websites had to offer, and I had found a pre and power schematic for a Marshall JCM800 2203 100 watt. I like the sound of these amps and since it is just a basic amp I figure it won't be too challenging to build. One thing I want on it is a 10 band EQ before the pre amp, I also found a schematic for this. I figure I will start by trying to make the equalizer since it is a lot less complicated, and if I get that working, go from there. Here are the schematics I found: Pre Amp: http://www.drtube.com/schematics/marshall/2203prem.gif Power Amp: http://www.drtube.com/schematics/marshall/2203pwrm.gif EQ: http://www.uashem.com/images/audio/unfasdastitled.gif From the amp schematics, would I be able to build the amp itself? Also, would these tubes work for the amp?: http://store.tubedepot.com/jj-ecc83.html (3 in the Pre Amp, 1 in the Power Amp) http://store.tubedepot.com/jj-e34l.html (4 in the Power Amp; 2 pair) I know the basics of electronics and some parts of the schematic confuse me (I've looked them up in the tutorials in the stickies, I could not find what I was looking for though.), but as for now I am just going to attempt to make the EQ. So, for the EQ, two parts confuse me: The boxes with 1 and 2 inside them, CON2 written under them, and J1/J2 above them. Are they some sort of input/output? The triangles containing a + and - and two what looks like a "half a capacitor" with VCC on top and VDD on the bottom. EDIT - One other thing, where would I get a blank circuit board? I can't seem to find any.. Thanks in advance for any help you contribute. Edited May 15, 2007 by TheGreatWhiteDope Quote Link to comment Share on other sites More sharing options...
ibanezlover Posted May 15, 2007 Report Share Posted May 15, 2007 If you want to know more about amp building go to AX84. There are some documents that explain alot of things and if you still don't get it you can ask people on the forum anything. Also, the page with circuit board building stuff at Hoffman Amps has parts and a tutorial. Quote Link to comment Share on other sites More sharing options...
curtisa Posted May 15, 2007 Report Share Posted May 15, 2007 From the amp schematics, would I be able to build the amp itself? Yes...Buuuuuut...I really hope you know what you're doing. Valve amplifiers operate at extremely lethal plate voltages, let alone the hazard in wiring up the mains AC to the power transformer - this is NOT a project for the inexperienced. Also, IME, unless you have access to some cheap source of parts it's almost not cost-effective to build some of these amps. The power transformer and output transformer in particular will be the two single most expensive parts to buy. Then you'll need to build or buy some kind of chassis, woodworking for the cabinet, all the passive components (caps, resistors, pots), jacks, knobs, tubes etc... You may be able to cut some costs by scavenging parts from old tube radios or TV's, but you're probably not going to find the exact same parts as specified in those schematics - none of the specs are provided for any of the transformers in those diagrams, other than a part number. I have built a few valve amps, and you do learn a lot from doing it, but I never even considered starting one until I had a fair degree of practical experience with electronic and electrical circuits, particularly high voltage stuff. Also, would these tubes work for the amp?: Yes, but see above. So, for the EQ, two parts confuse me: The boxes with 1 and 2 inside them, CON2 written under them, and J1/J2 above them. Are they some sort of input/output? Just an identifying name for a connector. J1 and J2 are the pin labels inside that connector The triangles containing a + and - and two what looks like a "half a capacitor" with VCC on top and VDD on the bottom. Operational amplifier. Vcc and Vdd are the supplies for that part - Vcc is the positive supply with respect to earth, Vdd is the negative with respect to earth. EDIT - One other thing, where would I get a blank circuit board? I can't seem to find any.. Any electronics supply store should stock them. Quote Link to comment Share on other sites More sharing options...
ibanezlover Posted May 15, 2007 Report Share Posted May 15, 2007 Yeah, be really careful and read all of the safety stuff. Also, if you are working with the amp turned on to measure voltages or something, work with one hand behind your back because if your hands touch the wrong parts a shock will go through your heart. Quote Link to comment Share on other sites More sharing options...
TheGreatWhiteDope Posted May 17, 2007 Author Report Share Posted May 17, 2007 After considering the cost and the danger involved, I decided to stay away from making the amp. However, I am still interested in making the EQ. On the EQ, I am still a bit confused. The operational amplifier, that would be the.. erm, the things that you move up and down on the EQ itself (Sorry for not knowing the term.. xP), correct? Also, where would I obtain these? \: I have yet to find any circuity parts at my local stores.. Quote Link to comment Share on other sites More sharing options...
BNichols Posted May 17, 2007 Report Share Posted May 17, 2007 (edited) operational amplifiers are little IC (integrated circuit) chips that are usually sold as the LM741 (the kind in your schematic). Radio shack sells parts online, but you might be better off at an electronic supply store that would have those capacitor values. also, you have a lot of op-amps, so you may want to look into getting LM324's which are quad op-amps. get three and you have 12 op-amps right there. here is a link to the datasheet, hopefully the ratings will be good enough for your application: LM324 Op-Amp ::edit:: the slider switches you mentioned are potentiometers or pots for short. google electronic supply and look around at different places. many stores sell all the parts you need: resistors, capacitors, pots, op-amps, etc. Edited May 17, 2007 by BNichols Quote Link to comment Share on other sites More sharing options...
ibanezlover Posted May 17, 2007 Report Share Posted May 17, 2007 Mouser has alot of electronics stuff. Sometimes it can be hard to find what you need, the sliders are here. Quote Link to comment Share on other sites More sharing options...
BNichols Posted May 17, 2007 Report Share Posted May 17, 2007 mouser has the op-amps too (Link Here). They are all around 50 cents ea. Capacitors and Resistors are subfolders here. Quote Link to comment Share on other sites More sharing options...
curtisa Posted May 17, 2007 Report Share Posted May 17, 2007 I wouldn't use the LM324 or LM741 in an audio related circuit. Their specs are pretty appalling. If you want to go with a cheap quad opamp with good performance I'd be using the TL074. The pinout is exactly the same as the LM324. There are many different ones to choose from though that have good performance - LM833, NE5532, TL072 (all dual types), NE5534, OP27, TL071 (singles). Datasheets are available all over the web. Quote Link to comment Share on other sites More sharing options...
psw Posted May 17, 2007 Report Share Posted May 17, 2007 I'd suggest looking into buying an equalizer kit, I'm sure there will be things about that would suit your purposes, come with a circuitboard and all components, ready to rock and roll...and probably cheaper too....put it in a nice case on top of your amp...nice... Quote Link to comment Share on other sites More sharing options...
TheGreatWhiteDope Posted May 18, 2007 Author Report Share Posted May 18, 2007 Know where to find any kits?, under $50 that is. The only kits I could find were over $100. I did find some car EQs for around $20 though, If they can be modded into a guitar EQ. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.