Why did my amp start on fire?

[soundNERD]

Thanks.

But can't these take up to 10A? or is that only momentary?

Oh, and also I don't think my power supply puts out 14A to allow 7A draw from each amp.

one more addition - Should I just, for my next amp, parallel two chips per bridge circuit? That way it will be able to deliver enough current not to blow up.

Plus I think I'll just invert one amp. The DRV134 had a really disorted buzzing sound in the output which was heard if I had the speaker connected between output and ground. If it was bridged, it canceled out.

[carlosfm]

soundNERD, you say you have a cheap Rockford Fosgate car sub drive unit.
Cheap or not, it's not common to see 8 ohm drive units for car audio.
Are you sure it's 8 ohms?

Anyway, why bridge?
I think that the two chips in parallel would be enough.
Current is much more important, but people always think about power, watts.

I made a sub with two paralleled OPA549s, and regulated PSU (LM338) at +/- 29V.
This thing drives a big 10" car audio sub drive unit in a sealed enclosure I made for it.
The drive unit has dual 4 ohm coils, that I connected in series (for 8 ohms).
The OPA549 has 8A continuous, 10A peak output current.
My sub gives me a tight punch in my chest when the music allows it.
Do I need more power?
No.
Do you?

PS: do yourself a favour, buy the last CD from Ben Harper.
It's a body massage.

[soundNERD]

I can GUARANTEE that this speaker is an 8ohm (plus we've been over this before I think )

Anyway, I think I'll try some LM338s powering 2 paralleled 549s.

Now, I know you said that watts don't matter, but would I benefit at all by making it a bridge/parallel amp? I only worry about this since it's going to be in a large room (but also may be in a small room, not sure yet), so would adding two more chips really make much of a difference?

Now, just to make sure, the chips did not blow from me mis connecting them right, just overdriving them, right? Because if it wasn't my dad will never trust the thing enough to use it.

Thanks!

[kilowattski]

If you look at the spec sheet they are only good for 5 amps output in the safe operating area of the opamp.

[soundNERD]

Carlos,

with your amp, does that amp put out a decent level of sound to fill a large room? With many chipamps I've built, I've noticed they perform well at high volumes, yet with certain frequencies, the amp starts losing control of the driver (running out of power, I guess) and the speaker moves a lot, but there isn't much sound. Do you ever get that with your amp?

And, about regulating it. I was looking into how to make those 338 regulator boards make a + and - voltage. It shows using two center tapped outputs. Can I use a standard split power supply to make them regulate to the correct voltage? And do you think I should make the voltage adjustable to get the best voltage for my amp/speaker combination? Finally, is 5A of power enough? Or should I parallel two regulators per rail? And if I run four chips (a bridge/parallel connection) should I definately have two regulators per rail?

Thanks for your help.

[carlosfm]

Originally posted by soundNERD
Carlos,
with your amp, does that amp put out a decent level of sound to fill a large room?

Yes, it does.

Originally posted by soundNERD
With many chipamps I've built, I've noticed they perform well at high volumes, yet with certain frequencies, the amp starts losing control of the driver (running out of power, I guess) and the speaker moves a lot, but there isn't much sound.

That's the unregulated PSU's fault.
It sounds better, it's easier, takes less space, and it's even cheaper to regulate than to use huge capacitance on an unreg. PSU.

Originally posted by soundNERD
Do you ever get that with your amp?

No.
I couldn't sleep well.

Originally posted by soundNERD
And, about regulating it.

Now we're getting there.

Originally posted by soundNERD
I was looking into how to make those 338 regulator boards make a + and - voltage. It shows using two center tapped outputs. Can I use a standard split power supply to make them regulate to the correct voltage? And do you think I should make the voltage adjustable to get the best voltage for my amp/speaker combination? Finally, is 5A of power enough? Or should I parallel two regulators per rail? And if I run four chips (a bridge/parallel connection) should I definately have two regulators per rail?

Where have you been, man?
You need independent secondaries.
A CT trafo can easily be modded to independent secondaries.
Don't fiddle with the voltage, don't try to take the voltage to the max.
Use 0.5w resistors on the regs and set the voltage to 31~32V if you use the OPA541s.
Yes, 5A continuous and 12A max that the LM338 provides is enough.
I use two paralleled OPA549s and a single pair of LM338 regs.
Works very well.
More than that (like bridge/parallel), you need more regs, and also strong rectification, like 35A metal-cased bridges.
Here's the regulated PSU schematic.

[soundNERD]

Thank you!

About the transformer, my transformer is a torrid, so I can't nor want to modify it. There is no way to get a negative voltage with what I have now and regulators?

and. do you reccomend I use 549s or 541s?

[carlosfm]

Originally posted by soundNERD
About the transformer, my transformer is a torrid, so I can't nor want to modify it.

Originally posted by soundNERD
There is no way to get a negative voltage with what I have now and regulators?

Not with LM338s.
There are no negative regulators with this current output.
It's so easy to mod a toroid... a 5 minute job.

Originally posted by soundNERD
do you reccomend I use 549s or 541s?

OPA549s regulated at +/- 29v works very very well.
They have very good current output, what a sub needs.

[soundNERD]

Well, does modding the transformer mean rewinding it?

or do I just take two rectifiers, and connect one between 26.2-0 and the other between 0-26.2?

I have about 15 Central Semiconductor 35A bridge rectifiers, like you said I should have.

about the 549, +/-29 isn't too much for it? I know the max is +/-30, so wouldn't it sound better not being pushed as close to its limits??

[carlosfm]

Originally posted by soundNERD
Well, does modding the transformer mean rewinding it?

No.
Just remove a little of the outside plastic isolation near the wires and separate the CT.
There are two wires joined, separate them.
Every trafo has independent secondaries, a CT just has two wires joined to a single wire.

Originally posted by soundNERD
about the 549, +/-29 isn't too much for it? I know the max is +/-30, so wouldn't it sound better not being pushed as close to its limits??

Good question.
Curiously, I use them at +/- 29V and they don't even get got.
It seams a conservative spec, those +/- 30V.
With these ones, and at 8 ohms, no problems with +/- 29V.