Ryan H Posted November 26, 2014 Share Posted November 26, 2014 Building myself a mini-Marshall... ...in a pedal. The very talented IvIark (Mark) over at TagboardEffects took a schematic of a pedalized JCM800 preamp circuit (tubes replaced with JFETs and such) and made a vero (stripboard) layout from it...but I wasn't quite happy with one or two things. Here's the original layout he made for reference: Now you'll notice there's only 1 input...and if you know anything about the JCM800 2203 and 2204, you'll know they have two inputs; a High sensitivity and Low sensitivity input. In this case, the input is replicating the High sensitivity input. Here's my HighLow mod for the layout Mark made, which allows for the High or Low input to be selected via either a second footswitch or mini-toggle switch. Another problem...the circuit emulates the preamp of the JCM800, but it's not an amp in itself; it can't drive a speaker. This is fine if you want to run it into a clean amp or something and get that 800 flavor, but I already have an 800. I want a compact, low volume facsimile of my amp. So i'm adding a dual-LM386 power amp circuit to the output of this pedal, which will give me about 1 watt into an 8 Ohm load. The power amp will run off a standard 9V supply (the LM386 can only handle up to 12V), while I'll be using an internal voltage doubler to run the preamp circuit at 18V. Don't have a vero layout of the power amp done yet, but it's really simple so it won't take up much space... All of this inside a 1590BB enclosure... Wish me luck, -Ryan Link to comment Share on other sites More sharing options...
Marshall Paul Posted November 26, 2014 Share Posted November 26, 2014 meanwhile... Aunt Polly, having taken a stroll in the woods outside of the village, now, unknown to everyone, lies injured in a ditch, while the wolves from the forest slowly move in in the fading light... Link to comment Share on other sites More sharing options...
Ryan H Posted November 26, 2014 Author Share Posted November 26, 2014 In the meantime... Aunt Polly, having taken a stroll in the woods outside of the village, now lies injured in a ditch, while the wolves from the forest slowly move in in the fading light... ...it's far too late at night for me to try to understand this...I'll try again when it isn't 2:00am... -Ryan Link to comment Share on other sites More sharing options...
Marshall Paul Posted November 26, 2014 Share Posted November 26, 2014 OK class,I hope you were all paying attention, there is a written test this afternoon you know! Link to comment Share on other sites More sharing options...
kidblast Posted November 26, 2014 Share Posted November 26, 2014 meanwhile... Aunt Polly, having taken a stroll in the woods outside of the village, now, unknown to everyone, lies injured in a ditch, while the wolves from the forest slowly move in in the fading light... Woa.. I so didn't see that comin, Hilarious... Ryan, sounds interesting,, keep us posted lad! Link to comment Share on other sites More sharing options...
Marshall Paul Posted November 26, 2014 Share Posted November 26, 2014 Goddamn! looks like an Al Qaeda high school science class! (Mustafa! Mustafa!! pay attention, or I'll throw the blackboard duster at you again!). Link to comment Share on other sites More sharing options...
Ryan H Posted November 29, 2014 Author Share Posted November 29, 2014 Update... Everything for the build has been ordered. Most components coming from Tayda Electronics, a few odds & ends from Smallbear Electronics, and the power amp chip from a seller in China (since they're hard to find over here). Should have it all in around 2 weeks...then the fun begins. Loving this DIY Layout Maker software...was able to plan out the entire circuit from input jack to output jack, and everything in between. And Google Sketchup for modelling the enclosure and everything in it to-scale...everything fits nicely. Can't wait to hear this thing... -Ryan Link to comment Share on other sites More sharing options...
Ryan H Posted November 29, 2014 Author Share Posted November 29, 2014 Also, I scrapped the LM386 power amp and instead went with a TDA7052A power amp. 1-1.5 watts out of a single chip and much more headroom than the 386. The 386 just doesn't do clean. The 7052 can also take up to 18V... -Ryan Link to comment Share on other sites More sharing options...
4Hayden Posted November 29, 2014 Share Posted November 29, 2014 Building myself a mini-Marshall... ...in a pedal. The very talented IvIark (Mark) over at TagboardEffects took a schematic of a pedalized JCM800 preamp circuit (tubes replaced with JFETs and such) and made a vero (stripboard) layout from it...but I wasn't quite happy with one or two things. Here's the original layout he made for reference: Now you'll notice there's only 1 input...and if you know anything about the JCM800 2203 and 2204, you'll know they have two inputs; a High sensitivity and Low sensitivity input. In this case, the input is replicating the High sensitivity input. Here's my HighLow mod for the layout Mark made, which allows for the High or Low input to be selected via either a second footswitch or mini-toggle switch. Another problem...the circuit emulates the preamp of the JCM800, but it's not an amp in itself; it can't drive a speaker. This is fine if you want to run it into a clean amp or something and get that 800 flavor, but I already have an 800. I want a compact, low volume facsimile of my amp. So i'm adding a dual-LM386 power amp circuit to the output of this pedal, which will give me about 1 watt into an 8 Ohm load. The power amp will run off a standard 9V supply (the LM386 can only handle up to 12V), while I'll be using an internal voltage doubler to run the preamp circuit at 18V. Don't have a vero layout of the power amp done yet, but it's really simple so it won't take up much space... All of this inside a 1590BB enclosure... Wish me luck, -Ryan Looks like a winner Link to comment Share on other sites More sharing options...
Marshall Paul Posted November 29, 2014 Share Posted November 29, 2014 Looks like a schematic for a Westinghouse washing machine. Link to comment Share on other sites More sharing options...
Ryan H Posted December 29, 2014 Author Share Posted December 29, 2014 Update! Parts arrived a few weeks ago but Christmas festivites have made progress slow. Got back to work on it today and was able to finish the main board! This is what a JCM800 preamp and phase inverter looks like shrunk down to pedal size, with JFET's replacing 12AX7's. More to come. -Ryan Link to comment Share on other sites More sharing options...
Marshall Paul Posted December 29, 2014 Share Posted December 29, 2014 Hey Ryan, do you do any circut bending? Link to comment Share on other sites More sharing options...
Ryan H Posted December 29, 2014 Author Share Posted December 29, 2014 Hey Ryan, do you do any circut bending? If you mean "The creative, chance-based customization of the circuits within electronic devices such as low voltage, battery-powered guitar effects, children's toys and digital synthesizers to create new musical or visual instruments and sound generators" Then no, not really. I don't just change stuff randomly and hope for the best. There's a method to the madness. -Ryan Link to comment Share on other sites More sharing options...
Marshall Paul Posted December 29, 2014 Share Posted December 29, 2014 Gotcha. My younger brother does that circut bending of pedals as a hobbie. He's now selling quite a few in shops here because they asked for them. I've got one of his pedals, a modded phaser and this thing is just great, weird effect sounds but good. Link to comment Share on other sites More sharing options...
Ryan H Posted December 30, 2014 Author Share Posted December 30, 2014 Today I sloppily connected all the pots, jacks and switches to test the main board before boxing. Also made the voltage doubler board. Plugged it in and it worked the first time...and it sounds fantastic. Played around with biasing the JFETs and swapping out some resistors and caps that I had socketed in advance for a couple hours, and I've finally got it where I like it. Going to add a low pass filter on a switch at the output to shave off some high end. It's a preamp so it can get a little piercing going into the front of an amp. Might also increase the output cap; bass is a little lacking in some places. Might have a sound sample for you guys tomorrow. -Ryan Link to comment Share on other sites More sharing options...
Marshall Paul Posted December 30, 2014 Share Posted December 30, 2014 "...my creature......it.....is......ALIVE!!" Sorry mate, just kidding...sorry. lol by all means, give us a sneak peak when it's done, want to hear this one. The Pocket Marshall!, you could market this one (?). Link to comment Share on other sites More sharing options...
4Hayden Posted December 30, 2014 Share Posted December 30, 2014 Today I sloppily connected all the pots, jacks and switches to test the main board before boxing. Also made the voltage doubler board. Plugged it in and it worked the first time...and it sounds fantastic. Played around with biasing the JFETs and swapping out some resistors and caps that I had socketed in advance for a couple hours, and I've finally got it where I like it. Going to add a low pass filter on a switch at the output to shave off some high end. It's a preamp so it can get a little piercing going into the front of an amp. Might also increase the output cap; bass is a little lacking in some places. Might have a sound sample for you guys tomorrow. -Ryan How much are you going to ask for these Link to comment Share on other sites More sharing options...
Ryan H Posted December 30, 2014 Author Share Posted December 30, 2014 How much are you going to ask for these Not 100% sure yet...at the least I think it'll have to be $200, just to cover parts and labor. Then again, I haven't finished it yet, so I've still got some hours to put in... -Ryan Link to comment Share on other sites More sharing options...
Ryan H Posted December 31, 2014 Author Share Posted December 31, 2014 No sound demo yet...was out and about buying supplies for pursuing pedal building further... The prototype has sold. Brought it in to the local guitar shop and the guys there loved it...one gave me a deposit on the spot. He doesn't want the power amp (which I haven't even assembled yet), and he wanted it in a smaller box (doesn't need the second footswitch; putting it on a toggle instead). I decided I had better get serious about how these pedals look. Time to enter the world of painting my own pedals, and decals. I present, the concept art for NugeFX's (long story) first official pedal, the 800. You might be wondering...what's the RRC for? It's the initials of this particular pedal's new owner. If I make one for myself, it'll be the RJH800. The reasoning is that Jim Marshall named the original JCM800 after his license plate (JCM800 = James Charles Marshall 800). So I figured, why not add a little personal touch to each pedal. Will try to plug it in tomorrow and give you guys an idea of what it sounds like. Plugged it into the front and the Effects Loop Return (the power amp) of a Two Rock Studio 22 yesterday and it sounded IMMENSE. As good as any JCM800 I've ever heard; and the guys agreed. Super excited, everything's starting to come together... -Ryan Link to comment Share on other sites More sharing options...
Marshall Paul Posted December 31, 2014 Share Posted December 31, 2014 Love it! well on your way mate. Link to comment Share on other sites More sharing options...
4Hayden Posted January 1, 2015 Share Posted January 1, 2015 Not 100% sure yet...at the least I think it'll have to be $200, just to cover parts and labor. Then again, I haven't finished it yet, so I've still got some hours to put in... -Ryan Send me a PM when you figure out what the $$ is Link to comment Share on other sites More sharing options...
Ryan H Posted January 1, 2015 Author Share Posted January 1, 2015 Send me a PM when you figure out what the $$ is Will do! -Ryan Link to comment Share on other sites More sharing options...
Rabs Posted January 1, 2015 Share Posted January 1, 2015 Cool stuff man... Keep it up Link to comment Share on other sites More sharing options...
surfpup Posted January 1, 2015 Share Posted January 1, 2015 So are you abandoning the power amp bit altogether? A little pocket sized 1.5 watt Marshall would be pretty bada$$! Link to comment Share on other sites More sharing options...
Ryan H Posted January 1, 2015 Author Share Posted January 1, 2015 Love it! well on your way mate. Cool stuff man... Keep it up Thanks guys...it's still sinking in that I might be able to make a business out of this. The guys at the shop have "liked" my pedals before...but they were floored this time. They were playing with it nonstop for 2 hours straight... Great way to start off the new year. -Ryan Link to comment Share on other sites More sharing options...
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