I am new to here and new in making guitar amps. I wanna make a guitar amp that can be used outside, where you can't possibly find a plug to plug in. As a result, I don't know how to start off.
Feel free to comment. Thanks.
Hi trialabc
This place is all about that.
Start by searching here "Ruby", "LM386", "Scarface" and you'll find enough to keep you busy.
That amp is less than 1 watt, but with a good speaker it rocks.
Good Luck.
Thank you J M Fahey, I will try to study those! Thanks a lot! :)
Quote from: trialabc on January 10, 2010, 09:32:12 PM
Thank you J M Fahey, I will try to study those! Thanks a lot! :)
This page has the schematics and layouts for the Ruby and Little Gem.
http://runoffgroove.com/articles.html
I love my Little Gem and have built 3 others for friends and family.
I just built a Little Gem Mk II for my son. It is housed in an old school intercom speaker cab along with the 8 inch speaker that came with my Valveking Royal 8. It uses a 9 volt battery right now, but I'll replace that with 8 C or D batteries. There is no volume knob, tone control, or power switch. Just plug in the cable to turn it on. When I have the volume cranked(via knob on the guitar) and I pick hard, the amp sounds like it is cutting out. Perhaps the two lm386's are wanting more current than a nine volt battery will supply. Even if that isn't the problem, it probably makes sense to use larger batteries. ROG rocks!!! :)
I have "read through" the schematic of Little Gem and Ruby, it seems that they all use a 9V battery. I am wondering if I can use other voltages like 6V or 12V since this may affects the performance of the amplifier.
Quote from: trialabc on January 13, 2010, 10:44:17 AM
I have "read through" the schematic of Little Gem and Ruby, it seems that they all use a 9V battery. I am wondering if I can use other voltages like 6V or 12V since this may affects the performance of the amplifier.
They can indeed use other voltages. The LM386 is comfortable in many voltage ranges. I have used it down to 4.5v (my pocket amp runs on 3xAA) and up to 12v. Some say that there is more headroom for clean playing with higher voltage, I didn't notice a big difference. So I normally use 3xAA for 4.5v or a 9v battery, more dependent on the case I'm putting it in than anything else.
12v is the safe max V for the 386 chip.
I have however had good results running them at 18v with a heatsink on the chip.
I also have run two of them BTL mode at 18v and its quite impressive at that point.
I would use the highest output 386 the 386LM-4 or the 386-D and run them at 12V with at least AA batteries. C size being optimal if you have the room.
Two 386LM-4 chips in BTL mode at 12V will give you close to 3 watts ouput more than enough for a practice amp.
Use a breadboard and experiment for yourself,have fun.
Quote from: Brymus on January 13, 2010, 06:42:40 PM
12v is the safe max V for the 386 chip.
I have however had good results running them at 18v with a heatsink on the chip.
I also have run two of them BTL mode at 18v and its quite impressive at that point.
I would use the highest output 386 the 386LM-4 or the 386-D and run them at 12V with at least AA batteries. C size being optimal if you have the room.
Two 386LM-4 chips in BTL mode at 12V will give you close to 3 watts ouput more than enough for a practice amp.
Use a breadboard and experiment for yourself,have fun.
BTL mode = bridged?
If so, do you mean like this:
(http://runoffgroove.com/littlegemMK2.png)
Yes thats exactly what I mean.
You should note that the ROG work/specs were using the 386 that only puts out a 1/2 watt at 9v ,hence 1 watt BTL,for the Little GemMKII .
The 386LM-4/386BD is 1 watt at 9v (I believe it's been awhile)
Download the data sheets and folllow the graphs ,You can get a good idea where 18V
will put you output wise.
I would stop at 12V though just to save having heat issues and chip failure.
16V seemed pretty stable (again if my memeory serves)I shoulda took notes...
But if your really adventurous you can use some heat sinks and run them at 18V.
Since I built my Little Gem MkII with sockets, I might give the 386LM-4/386BD a shot.
Oops! I think i have somehow mislead you guys. I should have stated more clearer.
Yes, I do want to make an amp that is supplied by battery. However I have two more constraints, which I think is the most troublesome part :
1. It is suppose used in an open area. e.g. not inside a house.
2. It should be able to play for at least 4 hours.
Since I have no idea in this area, I would still try to make RUBY or LittleGem first.
Quote from: trialabc on January 15, 2010, 11:11:42 AM
Oops! I think i have somehow mislead you guys. I should have stated more clearer.
Yes, I do want to make an amp that is supplied by battery. However I have two more constraints, which I think is the most troublesome part :
1. It is suppose used in an open area. e.g. not inside a house.
2. It should be able to play for at least 4 hours.
Since I have no idea in this area, I would still try to make RUBY or LittleGem first.
Well, a little gem will still play outside, just won't be that loud. I have a 250w car amp I'd let go for $20 plus shipping. It would run on a 12v car battery for a couple hours, or if you only used one channel you should get 3-4 hours.
You might consider a TDA2040 based amp. I've run a TDA2040 at 12v and it was much louder than a ruby(if I remember right). It no doubt used more current, but with a car battery, no prob. (btw, I've got a project that's been on hold forever to use a TDA2040 for a car PA system, so my wife can yell at bad drivers.) You can do something like this: http://www.generalguitargadgets.com/index.php?option=com_content&task=view&id=59&Itemid=200 . You'll need a preamp circuit, but that shouldn't be a big deal.
I was planning to build a RUBY for my first trial. However, I could not find MPS102, nor could I find 2N5457 in stores. Does anyone know what other components I may use instead?
Basically any N-channel Fet. You might find the J111/112/113 easier to find.
Whatever you use, download and check the datasheet because pinouts often differ.
Good luck.
Would it be possible if i use transistor instead? Since I lived in HK, tt is quite hard to find these electronic components as most probably no one will DIY a guitar amp here.
Well, JFET's are transistors. If you mean bipolar transistor, then yes, but it will have to be biased differently. Your best bet is to try to order what you need online from mouser.com or jameco.com or any other electronics part vendor. Of course shipping might be a little pricey for you if you order from jameco or mouser or any other American supplier, but I bet you can find an online parts supplier reasonably close. If you do use a bi-polar transistor, be sure to research how to bias them. http://en.wikipedia.org/wiki/Bipolar_transistor_biasing . Any low current BJT in an emitter follower configuration should be fine. However, you will not have the high impedance that you would have with the jfet input. In fact, you might not get much better results then you would have by leaving out the buffer stage all together, like with the Little Gem. You could also use an op-amp buffer instead of a source follower or emitter follower. It would be best to find a jfet with the same pinout as the mpf102. Then, you will be able to use the PCB layout provided by ROG. Good luck on the parts search.
Here's a couple of listings for mpf102's from Hong Kong suppliers:
http://www3.hkinventory.com/public/OfferInventResult.asp?search=offerinvent&MainCate=&SubCate=&Order=&keywords=&words=3&SearchType=offer&pnums=mpf102&btnSubmit=Search
http://hk.farnell.com/jsp/search/browse.jsp?N=500002+1002727&Ntk=gensearch_001&Ntt=mpf102&Ntx=mode+matchallpartial
It also looks like mouser isn't a bad bet either. http://hk.mouser.com/Search/Refine.aspx?Keyword=mpf102
Thanks for the links guys. It should come handy whenever I needed "rare" components. :tu:
Since all I lack is the buffered input, may I used op-amp to make a voltage follower at the input of LM386?
It seems to be a bad choice to me since this way just consume more current. However, if i just simply use a capacitor to separate the input and LM386, would that be possible? or will the performance become very poor?
Thanks in advance!
Hitrialabc.
I find it *incredible* that, of all places in the world, you find it difficult to find electronic components ... in Hong Kong !!! :o :o :o
Yet, maybe the minimum order is one million pieces each value ;), so .....
You may build this bipolar transistor buffer, which uses *any* NPN, TO92 general purpose transistor, *any*.
JFETs aren't rare. I would imagine they are as easy to find as an LM386.
I finally have time to built it and test it.
Since I am lazy, I first try it without using any buffer to the input of LM386.
In other words, I just use a 0.01uF cap connect to the guitar input, then a 10k ohm variable resistor. Then the rest remain the same as the RUBY schematic.
Everything seems okay, except it continues giving out a small static noise.
I wonder if this is the design problem? (meaning without the buffer)
Or because of the bad soldering, routing problem? --> this is because I am too excited to start and forget to plan first before soldering the components
Thanks in advance!
Congratulations for finally building it.
Some small static is normal, very probably captured by the guitar itself.
Does it dissapear when you set guitar volume and tone to "0"?
Yes.
The problem is when I turn on the maximum volume control, the static noise also increases.
Maybe later I should add back a buffer to see if the input noise can be reduced.
Do you have everything housed in a grounded metal housing? The buffer is for frequency response, and I do not think it will reduce the noise.
Nope. Currently it does not have any housing.
There is one things seems not good.
When I play chords harder, the sound could become so loud that become distorted to the output. (just like having a overdrive)
I wonder if that's why buffer is added.
Another question is a larger size speaker gives larger SPL?
Well, it *is* a low power amplifier, and thus easy to overload. That's life.
Later on, if you want mor power, to play on a busy commercial street, a subway station, places like that, start investigating louder amps that can be powered by a 12V7A alarm type gel battery, the best weight/power/pportability/price/availability compromise there is.
I'm an old timer and only used TDA2005 (20 loud/*real* watts into 4 ohms), but there is a TDA-something that's the same and uses only 4 or so external components.
Maybe somebody can point to it.I think it was the TDA1519.
Check on my "Callejero" (Street Man) amps
http://www.ssguitar.com/index.php?topic=1212.msg7641
you have links to Photobucket pictutes.
I have gone through the specification of TDA2030 which seems great for my further testing. Moreover I can buy it easily through stores.
Since TDA2030 requires higher voltage, maybe I can try TDA2003 or TDA2004 first which I can also easily buy from stores. (Seems also cheaper then Farnell. ;))
Though Fahey have mentioned about TDA2005, I don't find it from those stores that I visit. :'(
Probably I would move on to use 12V 7VA battery for my "battery driven guitar amp" project. Maybe later need to make DIY charger for that slightly heavy battery.
In the mean time I am really unhappy about static noise that my prototype RUBY amp, is there a way to eliminate the static noise? Like adding a passive filter? or should I simply buy a better "guitar wire"(the wire connecting the guitar and the amp)?
Thanks in advance!