My new 12 volt DC Amplifier for my Computer Sound

[wooferhound]

My mom accidently told me that she is getting me another 45 watt Solar Panel Kit from Harbor Freight, so I have been thinking more about how I can use the 12 volt power from my RE system. I had been thinking about upgrading my computer speaker system, from just Millawatts into a couple of 2 inch speakers. A friend of mine gave me some Radio Shack Optimus speakers, They are 2-way with a 4 inch woofer and a Linaeum tweeter, They really sound good for thier size with lots of bass and clear high frequencies.

So I wanted a really good amplifier to power them with, and it need to run on 10 to 15 volts from my Solar Power. I ordered a stereo kit that puts out 6-10 watts a channel depending on a power supply that can be anything between 8 and 18 volts. Here is a link to the kit that I built.
http://www.electronickits.com/kit/complete/ampl/k143.htm

After I was finished soldering up the PC board I mounted it in a chassis that used to be a stomp box guitar effect. Here is a picture of it working on my computer desk.



It only has 3 controls, a volume control and 2 switches. One switch chooses between 2 stereo Phono jack inputs. The other switch sends the output to speakers or a headphone jack. I have always hated to need to plug or unplug the headphones when I wanted to to choose between the speakers and headphones and I do really like having this speaker output switch.

I have been using my new computer speaker system for about 2 weeks now and I am very happy with the results. It gets hugely loud with great clear sound quality. It pulls 70ma on idle and I have seen it pull as much as 2 amps on peak loud music. The negative side of my 12volt system is grounded and this caused a loud ground loop hum when I first hooked it up, but I had a couple of audio isolation transformers that I put between the computer and my new amp and it stopped the hum totally.

Well I'm off to the Pub to hear some more of the great music that JW and others have posted. I'm going to crank it up this time and see if the cops will come and shut me down...

[Bruce S]

Hey woof;
 ya know this means building another dump controller  .
With that amount of panels you're going to be getting into some serious wattage now. That's up above the 100 watt stage.
What's your battery bank amperage looking like?

Nice kit too. I like the idea of not needing to unplug headphones too.

Cheers
Bruce S

[wooferhound]

Yes, I will have 9 Harbor Freight solar panels now, about 9 amps. Fortunately in my last few upgrades I planned to add more RE inputs so I think I am pretty much good to go. My Diode Combiner has 3 more inputs on it so I'm ready there, and my 2 stage Ghurd dump controller is good for up to about 20 amps so that's good too. My biggest thing I need to do is make another adjustable mount on top of my shed to put the panels on.

My battery "bank" is a single 225ah 8D truck battery so I'm good there too. I got this battery from Basil and he said it had been sitting out in the weather for some years. It has seen some hard times and is not up to it's prime capacity but it has been working good for about 2 years on my system.

[tanner0441]

Hi

I am always surprised at how loud little amps with efficient speakers can be, then I think back at when I first became involved with a couple of the groups in the Midlands and we were going out with a couple of Selma 10 watt amps and filling dance halls.  When I packed it in in the late 70s the base and lead were using 800watts apeace and 1600 watts on PA and drums. I helped out a few times later and they were using 2000 watt Tannoy fan cooled active speakers.

One thing that I find annoying though they now rate amps at peak music power not RMS.  I still have a couple of 12 volt vehicle PA amps and with a re-entrant horn make a lot of noise but no base or fidelity.

I wonder what type of music you pump through your 12V unit.

Brian.

[wooferhound]

I have been doing Sound and Lighting systems my whole life, over 40 years experience.
Sound systems confuse a lot of new sound guys, the confusing part is that if you double the watts you do not double the volume. It is logarithmic or exponential (can't remember) but to double the volume you need to multiply the watts by Ten. In sound terms you need to add 10 more decibels to double the volume. Knowing this you will see that you get most of your volume in the first one watt that you send to the speaker. Lets start with one watt and multiply it by ten a few times...
 Twice the volume of 1 watt is 10 watts = 2 times the volume
 Twice the volume of 10 watts is 100 watts = 4 times the volume
 Twice the volume of 100 watts is 1000 watts = 8 times the volume
 Twice the volume of 1000 watts is 10000 watts = 16 times the volume compared to one watt
So you can see that it is very hard to get the volume up over 8 times the volume of 1 watt. You are correct in saying that it's good to have efficient speakers. Many uninformed stereo listeners will want more volume than their 30 watt system can provide. They will get a 100 watt system and be disappointed in the results as they will only get 3 or 4 DB more.

I hate the way that manufacturers  manipulate their measurement of watts from the amplifiers too. Fortunately they are fairly truthful when rating professional gear since experienced people are purchasing the stuff for very specific reasons. Consumer gear is usually hard to determine what measurement they are using.

As a guy that rents out sound systems I have grown to like almost all music, I don't like Rapp or Twangy Country music. I'm looking for driving bass notes and creative playing or lyrics. I'm not much interested an most of the stuff recorded in the last 10 years but that's probably my age showing.

My username is the name of my sound company and here is a link to my systems . . .
http://wooferhound.home.mindspring.com/index.htm

[TomW]

It is logorythmic  sp?


Woofer is dead on the money sound scale for "loudness" is non linear. Not that he needs my support he knows noise. 

Tom

[birdhouse]

woofer-
thanks a ton for posting this!  i went to the site and found the:  Hybrid Stereo Amplifier Kit 2 x 25 Watt (RMS).  it is listed as working with a 24 volt set-up.  i haven't looked a ton, but this is the first stereo i've ever seen that will work with 24-32 VDC.  seeings how you are very knowlegable in
the sound department, do you think this would be a good match for a little pair of klipsh SB-1 book shelfs?  5.25" woofer. 

i'm glad you can rock your socks off now!   congrats on the soon to be panel upgrade!  new panels are so exciting!

thanks again!

adam

[12AX7]

ummmmm......

not enough vacuum tubes!

If one wants to build a amplifier check out  http://www.audiosector.com/
Sad to say no tubes,  but they do sound really nice.

ax7
Mark

[Opera House]

I remember when Saul Marantz told me how thrilling it was when he first made a car radio is first home sound system.  We all start somewhere.

[tanner0441]

Hi Woof

Are they old pics or are you still using little cabs for foldback not ear pieces? Impressed with the mixer looks like a graphic on every chanel. How far back do you have to be before the horns have full effect?

The system we had was WEM with a pair of festival stacks and two four chanel mixers held side by side with duct tape. The only problem we ever had with it was when someone put a dry ice smoke machine on top of a bank of stacked 100 watt valve amps to make it more impressive then over filled it with water. Shut the base player up, he was not happy, when I got the power back on we had only lost two amps so we managed.

I used to have a lot of trouble getting people to believe four slaved 50 watt amps were better than one 200 watt amps, once the mics come into the equation, for amps just below feedback point is louder than one big amp squealing its knickers off.

Have you got any lasers, I have just ordered a couple off EBay to see what they are like, my ears whistle enough without spending three hour sessions on a mixing desk but I am looking to hire lasers out (possibly) I want programable ones so I can look at advertising with logos. I have also just bought an Akai Miniak synth and vocoder. Good synth but there is no midi software for it and no third party stuff out yet.


Brian

[Madscientist267]

need to add 10 more decibels to double the volume

One must remember that there are 'power dB' and 'SPL dB'... they are not equal.

In terms of power, the doubling happens every ~3 dB, not 10...  

ie, from wikipedia:

To find the power ratio corresponding to a 3 dB change in level, use the formula:

For SPL, you'll notice that the numbers are different:

http://en.wikipedia.org/wiki/Sound_pressure#Examples_of_sound_pressure_and_sound_pressure_levels



and perceived volume here:

http://en.wikipedia.org/wiki/Sone



Its all very complicated... and as you pointed out, can be very confusing to someone new to the subject.

Then there's the hearing frequency curves... not even going to go there... LOL

Steve

[Bruce S]

Then there's the hearing frequency curves... not even going to go there... LOL

Steve

Hey Steve , This part is easy  it's the inverse of: your starting age x the amount of hours at a concert x the inches from the speakers divided by your age.
Endinnnnnnng with the new statement, "what was that you just said?" 

Divided by 2 if you've been to a Pink Floyd concert and had tickets 17 chairs from the stage 

THOSE were the days!!
 

[Madscientist267]

Oh man that's just wrong...

THAT is a live show I ALWAYS wanted to see, but just wasn't born early enough... They dissolved just shortly before I would have been able to see them... 

Oh well, at least I have the collection, and half and idea of what it must have been like, but video I'm SURE does it absolutely no justice...

And anyway, I didn't think 'what was that you just said?' ever came out at a Pink Floyd concert from what I am to understand... I hear it sounded more like "you gonna pass that?" instead... 

LOL

Steve

[klsmurf]

Was that Pink Floyd concert in Chicago by chance? Center stage, Soldiers Field, right at dusk, pink clouds started to roll in. Severe flashback! "Rush" was the band to put out some loud music back in my day.

[TomW]

I hear it sounded more like "you gonna pass that?" instead... 

LOL

Steve

I distinctly heard:

"Don't Bogart the..."

 

Tom

[Bruce S]

Oh man that's just wrong...

THAT is a live show I ALWAYS wanted to see, but just wasn't born early enough... They dissolved just shortly before I would have been able to see them... 

Oh well, at least I have the collection, and half and idea of what it must have been like, but video I'm SURE does it absolutely no justice...

And anyway, I didn't think 'what was that you just said?' ever came out at a Pink Floyd concert from what I am to understand... I hear it sounded more like "you gonna pass that?" instead... 

LOL

Steve

Video!!??? Crap they got video? They ain't me man !!! I swear officer!!
The date 1987 :: the place St. Louis Arena, WOW was it a show. And strangely enough I still remember most of it. Something this "guy" said about retina burn..still ringing in my ears.

All the vids I've seen of the show they "taped" really are NO where near the experience, went to the Aussie's version of PF here, close really good but not the same...
Might have been the missing haze , dunno. OR the missing light show Or the missing flying PIG ...maybe...
As much as I liked seeing Moody Blues in Germany this show blew that one away by a mile...

NO passing necessary  just inhale  and remember Quality is everything... and dirt is truly dirt

----------------------WOOF--------------------------
Heavy Apologies for the story drift !!

[Bruce S]

Back in the day of ARMY and living in Germany, it had its advantages.
In Meintenz-Kastel area , the was an on post store than had the best stereo stuff anywhere. Sansui dual pre/power amps that though not very high in power ratings by today's specs had Harmonic distortion that was great. Now pair that with a set of 6 foot Klipsch on the front and some real original Bose 501a set ( these are the first ones NOT what they have today) These had a special tweeter that they found produced ozone and lit up, these buggers weighed in at about 50lbs each)  for the back and you've got a system that would really light up the floors.

It only took 1 watt to fire up the Klipsch pairs and then the sounds was unbelievably crisp, then there's the AR series where even the affordable AR15s could make a room shudder if you were using a tube based Amp and Listening to Kansas or ELP :_)   

Quality built stuff like what Woof does makes these memories come alive!!
NOW all I need to do is get down there and see some of his shows

ROAD trip anyone? After the holidays of course

Cheers
Bruce S

[12AX7]

I recall loud

Deep Purple in Milwaukee,  I think it was in 74.    Just as they came on stage everyone lit their lighters at the same time. 
talk about a "purple haze".

After awhile the air was so thick,  you couldn't see if there really was smoke on the water.

huh,   come to think of it..  does sound travel faster in a smoke filled environment?