Thanks for the replies I think that I finally understand now. I just came back from the workshop and of course it was ECC83 the tube was named. And the other tube was actually named E82CC which is the same as 12AU7.

Quote from: mensur on May 21, 2010, 05:12:23 PM
You must be wrong, cause there is no tube with that name, there are ECC83(same as 12AX7, but just Europian name for it), ECL83 which is triode/pentode (almost the same as 12AX7 in triode section, and weaker EL84 on the pentode section). Maybe one of the letters fell off?

Maybe your right, I'll double check tomorrow if I get the time. The tubes is at my grandpas workshop, there I found then. This means that they could be old, really old. So if there ever been a EC83 tube, it could be there. But I doubt it though, the pins looked the same as the 12AX7 (9 pins, noval sockel).

Hi, I've tried to find out using google, but I didn't got any convincing answers there. The thing is that I've just found some old vacuum tubes, EC83 and EC82 (didn't remember the fabricate but it doesn't matter anyway). And if I'm right the EC83 is the same tube as the 12ax7 and the EC82 is the same as 12au7. Or not?

Don't know much about how tubes are named and so but I can't understand the point with having two part names for the same tube. So is there anything thing else that differs, or is EC83 just the same tube as 12ax7?

Well the voltage readings on the transistors looks really fucked up, so start looking for shortcuts there. Also if the base voltage of the transistor is less than about 0,7 V (the forward voltage drop) no current can pass through it. So maybe you should figure out why you read 0V on the base pins of Q4 and Q5. It could be a shortcut, but also something else. Start to try to get the schematic anyway.

At least put a resistor between the speaker lead and the TDA2003 Amp. And read this thread; http://www.ssguitar.com/index.php?topic=1122.0

Why not the LM386-N3? It can produce 1 W and the gain can be set to anything between 20 and 200 I think, check the datasheet for sure. If you want 2 W, you can bridge two of them.

Why heatsink DIP:s? these chip are designed to work without a heatsink anyway.

Marshall MS-2 was wildly discussed at diyAudio.com forum a while ago I remember. The only time I've seen that schematic on the internet, so I saved it then. Don't know if I'm allowed to post it here, so try to stop me.

...btw because the chip KIA6123, used in MS-2, turned out to be hard to find and also got bad feedback. Some guy at diyAudio.com came up with a MS-2 adapted for LM386. I don't remember if it ever got verified, but I post it here anyway.

Sorry, meant TDA2030. Which is chip with the lowest output power, but still can be run at +/-16 V I've found. TDA2003 can't be be used with an dual power supply as far as I know.

Yeah, this schematic looks really weird if you ask me. I don't understand what the switch is so-posed to do, but it's probably wrong as Fahey said. Another thing though, why is pin 1 & 8 at IC1 connected to ground via a pot (which is wired wrong, it should be wired as a variable resistor) and a cap?

Take a look at the datasheet, and you'll see. If pin 1 & 8 is left unconnected, the gain will be 20 (no distortion then). If they are connected with an capacitor at 10uF and a variable resistor at 1.2k in series, the gain can be adjust by changing the value of the resistor from 50 (R=0) to 200 (R=1.2k). This is how the Little Gem Amp an similar works.

EDIT
Btw, just read the datasheet and now I wonder why 10uF for C2 and C5. The datasheet suggests 100nF. And C5 might not be necessary, cause IC2 is only used with Gain=20.

Ok, good to know, thanksa for the feedback. Well, I'm quite satisfied with the layout so far, maybe I'm just paranoid. The first amp I build, also using perfboard, got the unwanted feature to produce a really loud sawtooth wave then the volume knob was turned to min. Quite annoying to almost blow the speaker, and your ears then the volume knob was turn down a bit to much. I still haven't figure out why this happened, except that it probably was because of the layout rather than the circuit and/or the components used. Maybe the grounding was wrong or something. However I don't wanna make that mistake again. The grounding in this layout won't be a problem what I can see.

I was actually thinking of building it with a TDA2003 chip. If a use the TDA2003 as power amp, I don't need the zenerdiodes cause I'll run all at +/-16 V too. Got an extra transformer, 2x12 V 1,5 A, which should to the trick.

I made a perfboard layout for the Marshall Lead 12 preamp last night, so I thought I'll post it here if anyone might found it useful. In the original schematic the supply voltage was +/-16, but I added two zener diodes and resistors
to make it possible to run the preamp at +/-35 V (yes the it will only be 15 V after the zener but it should work). I also decided to use the original wiring for the input jacks, which I found hard to draw in DIYLC, so look at the original schematic to figure it out.

I find it really hard to draw a satisfying layout by hand, so please tell me what you think about my layout so I can do better next time.

I'm been thinking of building the preamp for the MG15 for a while now, but making a proper PCB layout by hand (don't got any fancy CAD software or so) takes a lot of time. If anyone got some pictures of the PCB or so it could help.

Quote from: E on February 15, 2010, 10:18:41 AM

Quote from: tonyharker on January 30, 2010, 02:12:36 PM
Why not try a noisy cricket?  There should be enough info here < http://www.beavisaudio.com/projects/NoisyCricket/#Intro >  to tell you what to do.

Would that be a better option than the Ruby? Would it be possible to do with an inbuilt speaker? And how are those ultra simple smokey tone amps they have at the bottom?

Is there a guide to all the terms i should know somewhere? I reckon i could read the circuit diagrams - it's not too long since i did it in school.

Oh, and if it's not too much to ask could somebody have a look on Maplins to see if they have everything required? Only i can get a discount there... what sort of tools do i need? Obviously a soldering iron which i've been meaning to buy for ages but other than that i'm not entirely sure.

Thanks for all your help, i appreciate it

The Noisy Cricket is basically the Ruby amp with some modifications. It got a tone control and an grid switch which the Ruby doesn't, but except that they are about the same, and in my opinion they also about sound the same. Which one that is best it's up to you. With the noisy cricket you could probably get more different sound out of it, but require more components. And yes it could done with an inbuilt speaker as well.

The smokey amp looks a lot like the Little Gem amp, and would probably sound about the same. Check out this thread; http://www.ssguitar.com/index.php?topic=1456.0 or www.runoffgroove.com for some soundclips of the Ruby except you haven't heard it before.

Some people doesn't like the smokey/little gem amp because the input impedance of the lm386 chip is too low for guitar. And therefor the the noisy crikcet or ruby amp which got an FET buffer in front of the lm386 may sound better, more "spark" in the sound and so on, but personally i think the Ruby/Smokey amp sounds satisfying

Quote from: docz on February 15, 2010, 03:05:20 AM
Well there are a couple of stores that sell these things online. But they are rather expensive. A toroid 30VA 2x12V costs about $50USD, I can find a 6VA for $12USD but I don't believe that is going to cope with the TDA2030. The datasheet for the TDA2030 says it needs a 40VA supply, and 60-80VA for two bridged chips, those toroids cost over $100. Why are transformers so expensive anyway? Isn't it just a chunk of iron wrapped in copper? Haven't we used those for several decades? One would think that the prices of these devices that are practically inside of everything would drop due to the demand.... oh well...I thought solid state would be cheaper than valve amps because the components are cheaper, but it seems it is the same with any amplifier, the transformers and speakers make up 80% of the cost

Yes, transformers are expensive (copper is expensive and it's also expensive to produce a transformer) but NOT that expensive as you say. That online stores would rip you off that bad? I could get a 2x12 VAC 50 VA toroid for about 250 SEK at www.electrokit.se. Don't know if they ship to Norway but you could ask, anyway keep looking 50 USD for a 30 VA toroid sounds even more than it would cost to get one from www.elfa.se (which I think do ship to Norway but are very expensive anyway). So keep looking, 50 USD for a 30 VA toroid is way to much if you ask me.

I'm seriously considering to build the MG15 pre-amp, using the schematic attached schematic. There is some things I need to know before a start however. Two questions that might be obvious, but I want to for sure.

- The reverb circuit and jackets after the pre-amp made me a bit confused. However I'm only going to build the pre-amp, and then use it to drive a lm3886 chip. So I'm not really sure exactly what part of the schematic that includes this one. I've marked part what I think could work as a pre-amp if built at the attached schematic, but maybe I've missed something (except the PSU).

- Some pots wasn't marked at the schematic. This wasn't very hard to figure out, but if someone else could look at too it would be nice.