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benno
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Hey all,

Now i know this topic is suited more for one of those DIY stompbox forums or something but i am subscribed to this one and i know there are some very knowlagable people here that can help me.

A while ago i got some parts and decided to make a headphone amp to put INSIDE my project guitar i am making. i thought though id build it normally 1st just to get it working and stuff. I got to there and im stuck.

I am using just a drilled circuit board where i have to run all the wires to the parts myself. I cannot get this thing working. I have power because my LED comes on. I dont even get any static or anything. I spent hours on it today checking all my soldering joints to make sure everything was right.

I have a question. If i have a resistor that is slightly different to what GGG to me to use should i still get some sort of sound right? even if it isnt as good as if i was using the exact one. I assume this because sometimes even when i check resistors they can be out by abit. I ask this because i have (according to multimetre) 3.3K resistor where i should have a 3.9 .

Another question. If a resistor is soldered up onto my circuit board and i go to test it will the reading on the multi metre be affected by the components it is soldered to?

If i cant get it worked out i am just going to order the ready to solder circuit board off GGG and start again.

For interest sake peoples the project i am making is at GGG and link is: http://www.generalguitargadgets.com/v2/ind...p=page&SubMenu=

I am obviously very new at all this but i want to end up with something working.

Oh and thanks alot Lovecraft for those few diodes you sent me. Though i havnt used them yet because this thing wont work.. Haha,

Alrighty any answers or tips would be great!

Gee, i use this forum for help but never really give much back.. dont really have the chance to when i am probly the most uneducated on the topic of builidng guitars here, sorry guys and girls...

Thanks again! Bye for now,

Ben

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Hey, Ben, glad to hear that you finally got the diodes - that renews my faith in the postal system a bit. Sorry to hear you're having problems with the MXR circuit - you might want to take a look at that amp circuit that Matt's been talking up (Little Gem) or its cousin, the Ruby. Or you can get this kit from Dick Smith, and add a JFET preamp (or Dick's preamp) to it if you need to. Sometimes it's easier to pursue alternatives (I never liked that MXR headphone amp, but that's me personally :D )

I have a question. If i have a resistor that is slightly different to what GGG to me to use should i still get some sort of sound right? even if it isnt as good as if i was using the exact one. I assume this because sometimes even when i check resistors they can be out by abit. I ask this because i have (according to multimetre) 3.3K resistor where i should have a 3.9 .
Well, it will unbalance the power output stage a bit, so it might cause some distortion, but it shouldn't be enough to keep the whole circuit from working. I'd be inclined to suspect instead that you've got the pins reversed on either the IC or one of the transistors, but that's just a guess. This might also be of interest if you've been working on this for a while: (from General Guitar Gadgets, 06 May, 2004) Corrected a wiring error in the MXR Headphone amp wiring diagram, the far right two wires were reversed onto the board pads. You might want to check your layout.

Another question. If a resistor is soldered up onto my circuit board and i go to test it will the reading on the multi metre be affected by the components it is soldered to?
Yes, trying to measure a resistor in circuit will include measuring the effect of every resistive component in parallel or series with it, making the result fairly meaningless. Pull 'em out for an accurate reading.

If i cant get it worked out i am just going to order the ready to solder circuit board off GGG and start again.
That's the spirit! Never surrender!
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Thanks LoveCraft.

Wow that Little Gem is a little Gem, look how small and simple it is. I wish i new that existed before i started my MXR. WHy is it that the MXR needs to alot more complex than the little Gem if they both do the same thing? IN fact no you dont have to answer that, its probly some elctrics thing i dont understand.lol.

I might just build one of those little gems, Ill have to take out another tiny order for parts tho too. hahah. ahh well wat can you do.

About the wiring error i had a look on my print out and the date was 8th of may so mine should be right.

Thanks for your help!

Ben

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OK, i was lookin at this Little Gem.

ANd Lovecraft or someone else, i was wondering if you could write out a Bill of materials in a way i could just email to an electrical shop and the can get all the componants out to me. YOu see i dont know if the capacitors are tantalim or electrlytic (SP??) or what to use etc. Also I looked for a 25ohm rheostat.. what the is one of those?, do those things exist apart from at radioshack? Also In resisitors '5K B Gain' im guessing thats a pot, but am not sure what to look for when ordering this thing.

Thanks, Ben

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this is a parts list for the litle gem

1 220uf capacitor electro

1 100uf capacitor electro

1 .01uf capacitor film

1 .047 capacitor film

1 lm386

1 5k linear pot

1 25 ohm rehaostat (ie a wire wound potfor the vol control to handle more wattage than a standard pot)

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Here's Ansil's BOM with Dick Smith part #s and prices, and a couple of items that you'll need in addition (everything but the wire and solder) - I listed both jacks, so use the one that fits your headphones. Looks like you can buy it all from DSE for under $30.00AU - you can probably save some cash by buying elsewhere, but at least you know you can get everything.


  • R6905 24mm Wirewound Pot 3W 25R $7.87
  • R6805 5 kOhm 24mm Linear Rotary Pots $1.98
  • Z6086 AF Amp LM386N 1.6W High Gain $2.25
  • R3021 Cap MKT 0.047 uF 100 VDC $0.24
  • R3012 Cap MKT 0.01 uF 100 VDC $0.24
  • R4360 Cap Electro RB 100 uF 16 WV $0.30
  • R4380 Cap Electro RB 220 uF 16 WV $0.35
  • H5607 PCB Dual Prototype Board $3.98
  • S6100 Battery Holder 5 Pack $2.28
  • P1245 Skt 3.5mm STEREO PCB/Chas SPST $2.18
  • ********OR********
  • P1296 Skt 6.5mm STEREO Enc DPST Isol $2.18

Now all you gotta do is get it built! :D Take pictures of your build so you can do a tutorial if it works out really well!

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If that amounts to anything in money, I'm sure Ansil could throw you one together, if he doesn't already have one on sitting around on his bench. Give him a shout, and remember, he's having computer access problems, so he may take a while to get back to you.

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is this a headphone like on a cd player that has a battery and plugs into a guitar. If it is i will pay a **** load of one

Id happily by twice as many parts as i need and build the thing for you if u sent me down soem cash but as it is i dont trust myself at all with a soldering iron yet.

better off gettin one of the experts to do it :D

Ben

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Make tutorial so i can see how to build ill buy my own parts, but do you need to buy like those 50 dollor headphones to make it.

No you dont need expensive headphones. But i find those ones tht go inside your ears get fairly pain ful after a while. And also usually (well most of the time) the better ones are more expensive. So depending on what you find comfortable, the sound quality you want and your price range or the headphones that can with your last portable cd player they'll all work, just some are better than others.

Ben

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ok its just like our usual Guitar > Amp > Speaker setup.

except in this case its Guitar > Tiny Amp > Headphones.

everything just plugs in, not building anything into headphones.

I know i am pretty crap at explaining things. :S

Ben

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Try to keep up with the group, Monkey :D

It's just a circuit - it can be packaged any way you like. I think Ben was planning on building his into his axe, but you could build it to fit in any reasonably-sized case (like an old pager shell, or a dead Walkman®). Or you could put it in an aluminum stompbox case, or a piece of conduit with jacks on the endcaps, or wrap it in foil and duct-tape it to your forehead.

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Hey, i finally got my parts today, well thought i did, i opened the box up with excitement to find about half of them and the rest on back order :D looks like ill have to wait longer!!! B) Didnt even have dates of when they would be in.

Not Happy Jan................

(common sayin from an aussie yellow pages ad for anyone who thinks im weird :D )

Ben

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quick fix for the ruby amp.. jst crack open any basic cassette walkman type thing and cut off where the player head is at. and wire in a jack use the vol knob for output vol and use the trimmer for gain.. its already wired up andmost have three eight six equivelent with jfet or tranyy buffers i them. total parts cost. under five bucks.

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www.dse.com.au is the aussie dick smith, not sure if the part numbers are the same in other countries, they should be.

Theres a couple other things you probably want to get.

- some sort of enclosure to put it all in.

- OP amp socket i think they are called, havnt got time to look it up for you.

thats all i can think of now.

Ben

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