Replies to This Discussion

Permalink Reply by 3 String Blues on December 15, 2016 at 1:35pm

Did it work??? that could have been interesting!

• ▶ Reply

Permalink Reply by Paul Craig on December 12, 2016 at 10:40am

When I built my dual 386 chip bridged amp, I made it into a head which goes to a 20watt PA amp and a couple of 10" speakers. It can blow the roof off now. The speakers I have are old and need to be replaced soon, so I'm thinking of doing a American Voiced speaker and a British voiced speaker on a 3-way switch to choose either or both for a mix.

• ▶ Reply

Permalink Reply by Gordon Cooper on December 12, 2016 at 7:45pm

You need to find smaller wattage speakers, or prepare to buy or build a major 12/13.8 volt power supply to feed the need for wattage.

There are a number of class "D" amplifiers that people in the portable hi fidelity audio community swear by. The Lepai amplifers are one such amp.

http://www.ebay.com/itm/191722027203?_trksid=p2055119.m1438.l2649&a...

I have no financial interest in any eBay vendor or manufacturer, but lots of folks have gotten good results with these. You can find one that runs on 12 volts. You can get 12 volt sealed gel-cells for portable use, and could even fit the whole thing in a box with the amp and speaker, running a cable to your box with the other channel speaker in it. Despite the weight, 12 volt lead acid gel cells outlast most other battery types. They've gotten lighter, more efficient and much safer over time. They no longer vent gas or need to be topped up with water.

• ▶ Reply

Permalink Reply by darryl kernaghan on December 13, 2016 at 12:50am

I've also had good results with Lepai, but different model. http://www.ebay.com.au/itm/Lepai-LP-808-2-Channel-Mini-Power-Hi-Fi-..., i use 1 of these on my pc in the house, and another on my laptop in the shed, bang for the buck is great, about 18 months so far and no issues, i've also set up another amp in my carport, multi function, 12v dc or mains, but unfortunately no instructions or manual that i've found yet, although the menu is described quite clearly , i'm sure, when you press a button, unfortunately i don't speak Mandarin, or whatever it is, but this thing plays line in, usb sticks, flash cards, fm,and bluetooth transmissions.

http://www.ebay.com.au/itm/371698651587?ul_noapp=true

  

• ▶ Reply

Permalink Reply by Gordon Cooper on December 13, 2016 at 1:02am

Thank you very much for posting this! I intend to build a monaural speaker (4-5.5") speaker and amp around a big all-wood "Acid" cigar box, with an aux in, a guitar pedal in, and a built in am/fm Sony SRF-39/49 radio. Lots of good sound for not much money. I intend to use a 6 volt battery and a step up DC converter to 12 volts, and it all should fit. An option to power it from a portable USB bank is being consdiered as well, given how common they are these days.

• ▶ Reply

Permalink Reply by darryl kernaghan on December 13, 2016 at 6:00am

Gordon, i am extremely impressed with this unit, BUT, make sure you can get an operating manual,[and give me a copy], it has many functions and it is a big learning curve doing it by guesswork

• ▶ Reply

Permalink Reply by RTZGUITARS on December 12, 2016 at 9:13pm

Just about any speaker will work with the lm386 old pc speakers make great small amps and car speakers work great too.

I use Jensen mods 5in. 30 watt  6in. 16 watt 5's are great for acoustic the 6 for distortion amps they put ya back about $24 if I'm building for someone I want to use a new speaker and they rock when you put a pedal in front of the amp.

 The lm386 in my mind are more powerful the kit amps they come in 1/4  1/2  3/4 watt versions at least the Texas Instrument ones the other are a roll of the dice.

You can tailor the amp to the speak and the guitar by the Capacitors you use on the output to the speaker the higher the number the more bass.  

• ▶ Reply

Permalink Reply by Scott aka Farmer Ted on December 13, 2016 at 3:35am

Interesting about the speaker-driving capacitor. I typically use a 220uF/35v electrolytic. But I have seen schematics that use a switch and two capacitors of different value, say 100uF and 220uF, with the ability to choose one or the other.

• ▶ Reply

Permalink Reply by Denis U on December 13, 2016 at 9:21am

Ted,

I've seen one schematic with a switch between headphones and speakers with different caps. 47uF for phones and 220uF for speakers.

• ▶ Reply

Permalink Reply by JL on December 14, 2016 at 2:05am

A capacitor in parallel filters out high frequencies, a capacitor in series filters out low frequencies, a smaller cap in series for the headphones is to protect them from damage by too much bass below what the small headphones can handle.

• ▶ Reply

Permalink Reply by Denis U on December 14, 2016 at 7:06am

I don't pretend to understand this, but I remembered where I got the info. It was from another Brit on here - David L

"Why 220uf instead of 47uf? It has to do with cutoff frequencies. Putting a capacitor in series with a load resistor (in this case the load is our speaker) forms a high pass filter. Anything lower than the cutoff frequency is blocked. The formula for a high pass filter is f=1/(2*pi*R*C). R is in ohms, so let's say we have an 8 ohm speaker. C is in Farads, so 220uf is 0.00022. 1 / (2 * 3.14 * 8 * .00022) is 90.5. Our amp will play back any frequency that is higher than 90.5 hertz.If we swap in a 47uf capacitor and do the math, the cutoff frequency is 423.5. Yikes! Now we are losing all of our low frequencies and even some of our mids! So why would you want a 47uf cap? Well, what if you were driving headphones? That's 32 ohms, and if you do up the math for 32 ohms and 47uf, you'll get a cutoff frequency of 105 ohms."

Haven't tried it myself yet, but David sent me loads of good info on 386 based amps, so he;s one of my Gods ATM!!

• ▶ Reply

Permalink Reply by Timothy Hunter on December 14, 2016 at 10:58pm

the formula is correct . it is a first order high pass filter what you actually get is a 3db per octave  drop off at the cutoff frequency that the formula gives you . 3db is a reduction in volume of 50%. its not a brick wall in the way that you get absolutely nothing below that cutoff frequency. so you will still get the low frequencies just at a lower volume and getting quieter the lower the frequency is.

• ▶ Reply

• ‹ Previous
• 1
• 2
• 3
• 4
• Next ›
• Page