Subwoofer Amp - Page 1
Forum section: electronics / beginners

author: BeginnerMatt
author_rank: Contributor
timestamp: March 02, 2015, 09:57:01 pm
content: I have a 80W 4 ohm subwoofer with a blown pre amp. I was thinking of wiring my own pre amp to power the sub. The signal would be coming from my Kenwood 200W reciever. Does anyone have a schematic I could follow or any suggestions on how to go about this?

author: eejake52
author_rank: Contributor
timestamp: March 02, 2015, 10:46:06 pm
content: Here is one on diyaudio.com:http://www.diyaudio.com/forums/gallery/showphoto.php/photo/7122

author: BeginnerMatt
author_rank: Contributor
timestamp: March 05, 2015, 01:56:53 am
content: Quote from: BeginnerMatt on March 02, 2015, 09:57:01 pmThanks Jake, as I'm a beginner with electronics I have a few questions. What is the "R-DC" 5k resistor going to? What's the .1uf cap with the not filled in arrow going to? and finally what is the non filled in arrow on the output buffer / volume control section that is kind of pointing to the 10k resistor. Thanks in advance!

author: PeterFW
author_rank: Frequent Contributor
timestamp: March 05, 2015, 02:09:33 am
content: Quote from: BeginnerMatt on March 05, 2015, 01:56:53 amThose arrows are represend a connection to the signal ground.That should help to understand what they do

author: BeginnerMatt
author_rank: Contributor
timestamp: March 05, 2015, 02:22:31 am
content: Thanks! one last question, pins 7 & 4 are for voltage in and ground on the OP07. nothing is labeled in the schematic, does this assume you know to connect it to power or are these amps passive?

author: PeterFW
author_rank: Frequent Contributor
timestamp: March 05, 2015, 02:32:18 am
content: Quote from: BeginnerMatt on March 05, 2015, 02:22:31 amThe former, it asumes that you connect the supply pins yourself.But to be honest i do not like the schematic for several reasons, here is a nicer one with a ton of additonal information:http://sound.westhost.com/project48.htmBut first you should check what power supply you have available in the subwoofer, that would to some extend determine what sort of preamp (low pass, buffer, amp) you need.

author: N8AUM
author_rank: Regular Contributor
timestamp: March 05, 2015, 06:26:08 am
content: Why not try to fix the blown one ?

author: macboy
author_rank: Super Contributor
timestamp: March 05, 2015, 01:45:40 pm
content: Are you certain that you need a "pre amp" and not a "power amp"?

author: BeginnerMatt
author_rank: Contributor
timestamp: March 06, 2015, 03:30:12 am
content: I have no idea what I actually need. What I have is a sub woofer driver but no amp or anything because it's blown. I pulled the sub out of the enclosure and foolishly threw the amp away. So does this mean i need a preamp and power amp?

author: BeginnerMatt
author_rank: Contributor
timestamp: March 06, 2015, 03:32:03 am
content: Making myself a bit more clear. The amp is blown and already gone. The driver is in good condition though

author: Vgkid
author_rank: Super Contributor
timestamp: March 06, 2015, 03:55:00 am
content: You will need a power amp(amplifier) for the sub. The pre-amp only amplifies sound going into the amplifier.Thinking about it, yuo won't need a preamp, unless you are using a unamplified tape/record player.

author: Richard Crowley
author_rank: Super Contributor
timestamp: March 06, 2015, 03:59:02 am
content: If you threw out the previous amplifier, then you need a whole power amplifier, and likely the low-pass filter/crossover, also.A "preamp" is the least of your problems.A great source of subwoofer amps (including the low-pass filter/crossover) is:http://www.apexjr.com/amps.html

author: BeginnerMatt
author_rank: Contributor
timestamp: March 06, 2015, 05:11:50 am
content: It seems like I definitely need a power amp. If I followed this schematichttp://www.circuitstoday.com/100-watt-sub-woofer-amplifierhow would I power it? It needs +/- 35V @ 5amps. Would I need to make a transformer or something?

author: Richard Crowley
author_rank: Super Contributor
timestamp: March 06, 2015, 05:29:47 am
content: Yes, you would need to make a relatively substantial power supply. You would need to find something around a 48V, center tapped transformer good for at least 5A or 100+ watts. And a power bridge rectifier and some big filter capacitors.No offense, but the questions you are asking would lead us to believe that you may not be ready for such an advanced circuit construction from scratch. You may be better advised to get a ready-made amplifier module like the ones available from Apex Jr.

author: BeginnerMatt
author_rank: Contributor
timestamp: March 09, 2015, 06:46:48 am
content: yeah I'll take you're advice and buy a pre-made amp. I'm going to need far more experience to do this project. Thanks for all the input