Biamped System with LM4780s - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps

Chip Amps Amplifiers based on integrated circuits

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 27th June 2006, 08:17 AM   #1
kent is offline kent  Canada
diyAudio Member
 
Join Date: Jun 2006
Default Biamped System with LM4780s

Hello,

I'm just making my foray into the world of diy audio, and would welcome any tips and comments on my power amp idea. I'm familiar with basic electronics, mainly from a fair amount of work with microcontrollers, but not so much with audio per se.

I have a large pair of 3-way speakers for which the sound is rather lacking. I suspect the system is somewhat under-powered and could be vastly improved with a decent power amp rather than a stock Yamaha receiver. Although, the drivers are certainly nothing fancy, so I don't want to get too carried away.

For the drivers, each speaker has a 12" sub, a 5" mid, and a tweeter. I can only find specs on the mid - its 8ohm, 1" voice coil, 40W RMS, 80W Peak, 300hz - 8khz. The crossovers are...well, pretty much not existent. They consist of (gasp!) a capacitor to the mid and a different capacitor to the tweeter. That's it.

Now, here's what I'm thinking. Bi-amp each speaker with a LM4780, feeding an active cross-over into each amp in the LM4780 package. I'll keep about the same XO as for the cap currently used to the mid, with one amp powering the sub and the other powering the mid and the tweeter. I'll also put a passive XO between the mid and tweeter. I'll put the active XO and chipamp together on protoboard, install one PSU per speaker, and mount everything to the bottom of the cabinet. This way I'll avoid having to worry too much about cases, and will end up with all-encompassing active speakers.

I'm planning on basing my amp design on Brian Bell's LM4780 schematic, with maybe his snubberized power supply design as well.

I'm hoping the amping will do these drivers a lot of good - if not, I'll have to move on and get some new drivers to go along with the amps .

General comments and tips are more them welcome, but I also have a few specific questions...

- Should I differ any components in particular considering one is driving bass and the other mid/high?

- Considering this isn't an uber-hifi system, is it going to make much difference if I use metal film resistors and polycarbonite caps vs carbon-film and ceramic?

- At my local electronics store, for transformers, it looks like I can get a 1 AMP 15 VAC, 2 AMP 18 vAC, or 1 through 5 AMP 24 VAC. Any recommendations?

- I think I should be alright with the passive crossover, but can anyone point me to good material on active crossover design?

Thanks in advance.
Kent.
  Reply With Quote
Old 27th June 2006, 11:43 AM   #2
sangram is offline sangram  India
diyAudio Member
 
Join Date: Sep 2002
Location: India
Your plan sounds good, except you have to figure out the active crossover correctly.

Rod Elliot has a good calculator for crossover frequencies sound.westhost.com for 24 and 12 dB/octave.

Transformers: I would pick at least a 5 amp, 24VAC but if budget is tight, then a 3A 24VAC.

Components: Use metal films and poly caps. The difference is not subtle, and can be heard on very low resolution systems too.

You should have some kind of a trimmer on the high section so you can adjust the relative level of the two sections.

At the bottom of the cabinet you'll have a lot of vibration. You might want to think about that as well.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
WTB LM4780s DonoMan Swap Meet 1 19th May 2007 11:51 PM
Tube amp for biamped speaker navin Tubes / Valves 39 25th November 2005 11:36 AM
Grounding in a biamped buffered system Raka Chip Amps 20 19th November 2003 12:49 PM
Wattage required for biamped ESL phishead8 Planars & Exotics 6 3rd July 2002 12:42 PM


New To Site? Need Help?

All times are GMT. The time now is 04:34 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2