renfrow said:
Thanks. I should have known better.
troystg said:
It certainly put a damper on the proceedings.
Oh well, I've spent the evening cleaning the other boards and I've mostly completed the final one - the right channel highpass.
I also rebuilt the power supply to fit inside the amp case (look way back in this thread and it's in a separate case). I'm using just one 25-0-25 transformer with 8000uF per rail smoothing and the opamp supply is from a 12-0-12 with no regs. I just want to finally use it for now.
I will be building a new case for this, maybe latter this winter. I am tired of the aluminum finish - time for something new. I have a vision....
BTW, I'm now using a water-based, no metal added flux. Works good.
Good on you! I've finished one whole speaker now and have started on the next. It was a lot of work to get one finished and seems disheartening to have to do it all over again - one speaker ain't gonna do it though! I have half built the other speaker and finished the crossover - just the amps, power supply..........I'll get there. Will post photos in a month or so. Sounds great though - a worthwhile project.
Cheers and Merry Xmas.
Cheers and Merry Xmas.
Tex Houston said:
Hi Tex,
I know what you mean. I build both speakers at the same time for that very reason, that way I don't use up all of my enthusiasm.
Listening will have to wait till tomorrow, I'm afraid. I underestimated how long it would take to get everything connected, and now it's too late. Big drawback with this amp is the mess of wires that need to be hooked up.
It would be better if I had the hindsight that I now have with this project. I would have had it on two boards: one with the pots, the VU meters and the filters. The other with the output buffers and amps. Eliminate some of the tangle of wires.
The unit is completely assembled now though. Not my best work, kinda stuffed everything in there just to get it done. I can use it while I plan the new chassis.
All I need to do is to rig up some speaker cables (using cat5 for this).
A shot of "it" following installation of the right channel amps. Too many wires.
Attachments
troystg said:
Yes, signal is paralleled to each board. Separate shielded lead for each board from the RCA jack.
Here's a list of the wires coming from each board:
1. +15 volt
2. -15 volt.
3. +35 volt
4. -35 volt
5. ground
6. speaker out
7. level pot ground
8. level pot wiper
9. level pot signal
10. signal in
11. signal ground
Like I said, too many wires! Most troublesome when one breaks at the board. I will do a better job of organizing them when I build the permanent case.
In the meantime, I'm using it! NOW!
Listening to a variety of pieces I'm intimately familiar with and it's remarkable how details I'd not noticed before jump out at me. Hands down beats the a ss off the passive crossover / Yamaha receiver combo.
Amazing there is no noise (hum,hiss) from the speakers. The wires are shoe-horned in the case all over the place. Like a snakes nest.
I have shut it down for the night. I must say the results are well worth the effort. If I had it to do again, I'd do some things differently, but it's all a learning process.
Hard to believe I let a little thing like the flux problem and my fear of failure keep me from finishing this.
Of the 12 boards I ordered from Futurelec (sorry for the mislaid blame, I'd definitely use them again), I have 3 left. I ruined 3 trying to solve the noise issue.
I think I will use these final three boards to build an active centre speaker. This time the amps will be in the speaker cabinet, with the power supply separate.
I'm saying a bit more about this amps performance with the speaker it was built for here .
Hard to believe I let a little thing like the flux problem and my fear of failure keep me from finishing this.
Of the 12 boards I ordered from Futurelec (sorry for the mislaid blame, I'd definitely use them again), I have 3 left. I ruined 3 trying to solve the noise issue.
I think I will use these final three boards to build an active centre speaker. This time the amps will be in the speaker cabinet, with the power supply separate.
I'm saying a bit more about this amps performance with the speaker it was built for here .
It has been nearly a year since I posted to this thread. An update is in order.
Having "finished" the active amp, I used it for about 4 months. During this time I tried different things to improve the sound of the speakers , but found the biggest obstacle to be the fixed nature of the filters. I decided to go with an adjustable crossover, in this case I wound up getting a DCX2496.
The new plan (for those speakers) is to build discrete amps and drive them with the DCX.
Now, that leaves me with this active amp and no use for it. I thought I'd find a purpose for it sooner or later, maybe a set of rear surrounds.
On a junk expedition to Goodwill, I found four 15" woofers in like new shape - $100.00 for all. I grabbed them, thinking they may be bad but hey, they are 15"! Work with it.
Long and short, after measuring the woofers and seeing high Q, I thought I could use these for OB subs or ripole subs with a little EQ.
I then had another idea. What about these in a less than ideal box size - acoustic suspension, build them for shop speakers and use the active amp for them.
Worked it out with Unibox and came up with a workable design. A little peak in the response at 60HZ (3db) but that's ok for the purpose.
Looking at the snakes nest of wires in the chassis, I decided to start again and take each "side" (bass, midrange, treble) and build two plate amps that will be mounted in the speaker boxes.
New power supply boards with 3-4700uF caps/rail and regulated +/-15V dropped from the main supply. I have two 25-0-25 transformers from junk receivers that I'll use.
Here's how it looks. I'm using the same heatsinks as before, but I've mounted them on a piece of aluminum plate.
Having "finished" the active amp, I used it for about 4 months. During this time I tried different things to improve the sound of the speakers , but found the biggest obstacle to be the fixed nature of the filters. I decided to go with an adjustable crossover, in this case I wound up getting a DCX2496.
The new plan (for those speakers) is to build discrete amps and drive them with the DCX.
Now, that leaves me with this active amp and no use for it. I thought I'd find a purpose for it sooner or later, maybe a set of rear surrounds.
On a junk expedition to Goodwill, I found four 15" woofers in like new shape - $100.00 for all. I grabbed them, thinking they may be bad but hey, they are 15"! Work with it.
Long and short, after measuring the woofers and seeing high Q, I thought I could use these for OB subs or ripole subs with a little EQ.
I then had another idea. What about these in a less than ideal box size - acoustic suspension, build them for shop speakers and use the active amp for them.
Worked it out with Unibox and came up with a workable design. A little peak in the response at 60HZ (3db) but that's ok for the purpose.
Looking at the snakes nest of wires in the chassis, I decided to start again and take each "side" (bass, midrange, treble) and build two plate amps that will be mounted in the speaker boxes.
New power supply boards with 3-4700uF caps/rail and regulated +/-15V dropped from the main supply. I have two 25-0-25 transformers from junk receivers that I'll use.
Here's how it looks. I'm using the same heatsinks as before, but I've mounted them on a piece of aluminum plate.
Attachments
The original has slide pots on the front panel of the chassis. These were to adjust the output level for each band. To get rid of these I had to solder a trimpot on the bottom of each each amp board. I can make level changes by removing the amp from the speaker.
I finished the first one and got it working trouble free. A little longer to mount it into the rear panel of the speaker box (working on those at the same time).
Hooked it up to my HTR front left pre-out and had a listen. Wow, much better than I thought this speaker would sound. Solid bass and very clear.
Encouraged, I started on the second amp set. I had everything finished and did a test. No output from the midrange amp. Nothing. Try this, try that nothing works. Stumped, I figure I'll not waste anymore time on that, but just build a new one (I still have 3 or 4 boards left). New components, including the LM3886.
All done, install it in the "plate" amp chassis. Plug in the transformer. After about 3 seconds, sizzling sound, smoke (a lot!) and a loud POP! Unplug the power, clear the smoke and see the top burst open on a decoupling cap. It's then I notice (after careful inspection before testing) that the polarity is backwards.
Photographic evidence of my carelessness:
I finished the first one and got it working trouble free. A little longer to mount it into the rear panel of the speaker box (working on those at the same time).
Hooked it up to my HTR front left pre-out and had a listen. Wow, much better than I thought this speaker would sound. Solid bass and very clear.
Encouraged, I started on the second amp set. I had everything finished and did a test. No output from the midrange amp. Nothing. Try this, try that nothing works. Stumped, I figure I'll not waste anymore time on that, but just build a new one (I still have 3 or 4 boards left). New components, including the LM3886.
All done, install it in the "plate" amp chassis. Plug in the transformer. After about 3 seconds, sizzling sound, smoke (a lot!) and a loud POP! Unplug the power, clear the smoke and see the top burst open on a decoupling cap. It's then I notice (after careful inspection before testing) that the polarity is backwards.
Photographic evidence of my carelessness:
Attachments
troystg said:It's very hard to put the magic smoke back in..
Luckily there are more of the same for me to ruin.
I got that fixed. Try it out and everything works.
Next is to mount it to the back panel of the speaker, connect to the drivers and try again.
All systems are go!
Successful recycle of fledgling DIY project. My skills have improved since I designed and built these active amps. There are things I'd do differently, but fundamentally there was nothing wrong with their performance. That's what counts.
Anyhow, they have found a new home and I think they will be there for quite some time.
Here's the amp mounted on the back panel of the speaker. You can see some of the speaker in the photo.
Attachments
John (MJL21193), would it be possible to post (again) the schematics and PCB layout/silkscreen that you used? I am interested to build these guys... There has been quite a bit of update along that way that I found it difficult to follow which is the final version. Of course, I prefer a single sided board. Thanks.....
Something new.
What I have here is a spin off of the original idea. I have gone back to the drawing board and substituted an LM4780 for the LM3886 giving 2 channels on the one board. High pass filter for one and low pass for the other so this would be ideally suited to a compact 2-way (like my centre speaker and surrounds). Compact solution on one board for a complete active 2-way.
Yes, I'm a sucker for punishment.
In it's early stages yet - a bit more time to optimize the layout before I prototype it to test.
Here's the rough layout:
What I have here is a spin off of the original idea. I have gone back to the drawing board and substituted an LM4780 for the LM3886 giving 2 channels on the one board. High pass filter for one and low pass for the other so this would be ideally suited to a compact 2-way (like my centre speaker and surrounds). Compact solution on one board for a complete active 2-way.
Yes, I'm a sucker for punishment.
In it's early stages yet - a bit more time to optimize the layout before I prototype it to test.
Here's the rough layout:
Attachments
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