class D amps cutting out

[seanm]

In a perfect world, an amp would tell you why it was shutting down. For instance:

"Shutting down due to thermal overload on hot day. Tell the guitarist to turn down."

Not sure I want my amp correcting all my mistakes!

"Sean, you where supposed to go to the chorus there.... didn't I tell you that 100 times in practice :scowl:".

 

[wave rider]

punchclock, what cabinet(s) were you using when the amp shut down? Did I miss that part?

Jimmy had a puzzler with his Ampeg little stack, it worked fine with one of the 210s but distorted with two of them. Impedance dipping was speculated...

=wr=

 

[agedhorse]

I could think of all kinds of funny (and rude) error messages that could be displayed. Some would no doubt target guitar players and drummers. Maybe one targeting the guitarist's freeloading girlfriend would be appreciated by that bass crowd too

 

[punchclock]

the shutdown has happened several times with my usual set up: one TL-606 (8ohm load, amp set to 8 ohm).
it happened with 2 TL-606s (4ohm load, amp set to 4ohm).
it happened with one TL & one ashdown 210. (4ohm load, set to 4ohm...)

punchclock, what cabinet(s) were you using when the amp shut down? Did I miss that part?

Jimmy had a puzzler with his Ampeg little stack, it worked fine with one of the 210s but distorted with two of them. Impedance dipping was speculated...

=wr=

 

[agedhorse]

the shutdown has happened several times with my usual set up: one TL-606 (8ohm load, amp set to 8 ohm).
it happened with 2 TL-606s (4ohm load, amp set to 4ohm).
it happened with one TL & one ashdown 210. (4ohm load, set to 4ohm...)

Do you have a good multimeter? Measure the DC resistance to see if that shows something interesting.

Try your amp set at 4 ohms with the single 8 ohm cabinet and see it the amp functions normally.

 

[pgbassman]

This happened to me with a crown XLS power amp and an Ampeg Pro 7...you can almost tell when it's going to happen. I was playing a loud passage but I never felt like the amp was being overdriven nor was the clip lite acting like a strobe. I'm a very percussive player and that may have been to much for these amps to handle. I've moved onto a markbass tube 800 and haven't had any problems playing at any volume.

 

[jeff7bass]

One area where class D amps closely coupled to switchmode power supplies really shine is in anticipating a potentially dangerous fault to the amp.

Low line voltage that jepordizes maintaining valid PWM freqiuencies and duty cycle ratios.

High line voltage, or excessive RFI/distortion harmonics on the power line

I've read this before here at TB and was wondering if a voltage regulator would help.

 

[dave_bass5]

I can get my MB-500 to shut down if I push the output level to hard on my BDDI.

Once I figured that out I haven't had any problems.

Ive done this twice with my SA450 when the output was up too high on my BDDI, and thats not even a class D.

 

[Jerrold Tiers]

Amps shouldn't shut down with any sort of reasonable abuse.....

That said, it is better for the amp to shut down than to damage itself..... and better still if the designer can anticipate and design around the abuse that threatens to damage it. But there are limits.

Fire pumps should keep running no matter what.... on board ships they often don't even have fuses in the power line.......

Amps are a tad less important, and can be forgiven if they shut down if played hard in Brownsville Tx in July on a sunny day with no cover and the amp on top of the stack...... if the amp were capable of withstanding everything, it would cost too much for anyone to buy it except the military.

And class-D is notorious for a history of optimists who believed everything about "no heating" of the output devices....

Ideally, the amp should work, and if you do something beyond its capabilities, it should not try, but just not work until you fix the dumb thing you did. If it can tell the reasons for not working, so much the better.

I don't think class-D has any lock on issues, lots of normal analog amps have issues with various types of abuse. But with any newer technology, early units will have more problems, and some folks will be better at making good units than others.

As for the "should be capable of working at full output continuously", there are a number of analog amps that can't do that, and they are in many cases highly rated units that lots of you use and like......

It all depends on what "full rated output" really is. Some amps can put out more than the mains can supply. You can't expect continuous full power from them, even if you could use it.

And in any case, you can't expect full power to be needed continuously when playing bass. We proved that many years ago when we were questioned about it, about the best that anyone did was 50%, and that was not really musical..... more like serious thrash. The use of limiters and compressors can raise average power, but at the cost of dynamic range and again, musicality.

 

[countrybass007]

I find this all very interesting, I've ran my Orange TT at high volumes at outside gigs without any problem at all. I run an Orange 212 and a 15 using the 4ohm setting, and it kicks serious butt.

 

[agedhorse]

I've read this before here at TB and was wondering if a voltage regulator would help.

Most voltage regulating devices do not do well with dynamic loads... ie. rapidly changing and high currents (causing rapid voltage swings). Some can damage power amps by hunting and oscillating, some by outright failure.

 

[philtoler]

I find this all very interesting, I've ran my Orange TT at high volumes at outside gigs without any problem at all. I run an Orange 212 and a 15 using the 4ohm setting, and it kicks serious butt.

Me too. I make a point of only using Orange cabs with my Orange TB500, having been advised, as agedhorse pointed out, that poor matching of speakers to amp could present a serious risk.