Class D amp at full volume?

[Al Kraft]

my best option would be to contact my amp manufacturer with the specific question.

IMO this is always the best way to go and any time you can substitute "designer" for "manufacturer" I think you're even better off.

it's the general principle of running a Class D head hard that I was trying to get to.

Once again IMO, I don't think a class D amplifier, that is well designed, should have any difficulty delivering its full rated power all night long. IIRC Mesa for their D-800 and Aguilar for their TH500 have said that their products could do that.

Given that there are a great many ways to protect an amplifier (staying only with that component) ranging from complete shut down to graceful degradation to robustness in design preventing shutdowns, I'm not sure one could easily generalize about "class D" or any other class of amplifier as a category. As for robustness in design there are of course multiple ways to achieve that. The simplest might be by providing over-spec components and operating them in a de-rated fashion (e.g. you design a 750 Watt amplifier and "govern it" to 500 Watts output max). The other end of the spectrum uses innovative design techniques to preclude ever running with any degradation. And then of course you have a mix of the two approaches.

The problem here is that we as consumers often have little insight into the design decisions other than what some of the more progressive and transparent manufacturers (and we all know who those folks are) can reasonably share. For many companies we just know that "their class D" amplifier products shut down or go into limp home mode when pushed too hard. I guess that's a valid, albeit not useful for me as a gigging musician, protection approach.

The biggest problem is when someone has a bad experience with a certain type of product (e.g. class D bass head) due to what I would characterize as poor design for the use case, they will often blame the technology for the failure and not the designer. Not all designers are equally talented and not all companies are willing to trade time-to-market or lower list price off against more elegant/sophisticated design approaches when simply shutting down in a self protect mode will prevent complete failure of the equipment.

 

[ThisBass]

My rule of thumb has always been-- have extra power in reserve, and push it up to 70% if necessary. This is where the "using good judgement" factor comes in.

That's +1.5dB power in reserve.
IME the deviation of both the dynamics (respectively transients) and average even for players with darned good playing technique should be considered as > +3dB.
Without compressor and/or distortion pedal Its not possible to (really) exactly gain not more than 70% of amp reserve.

 

[Sunset Shalom]

Seems like most amps cranked to the max would be noisy as hell, and probably making a lot of feedback depending on your set up.

 

[Old Garage-Bander]

You generally can't with modern amplifiers.

You can fry them by feeding them a way too hot input signal.

Been there. Done that.

 

[Old Garage-Bander]

I have a sixty's era, fender that fries resistors in the power tube section. It loves to cook the 470 ohm 1w resistors.

Maybe someone else has suggested this, but that's not normal.
Have you considered that the amp may have a problem?

 

[agedhorse]

None of these points are exclusive to class D by the way.

 

[Drgonzonm]

Maybe someone else has suggested this, but that's not normal.
Have you considered that the amp may have a problem?

Undersized OT, and bass being played on a lapsteel amp. and sensitive to switch flippers, trying to get more sound out of an 8/16 OT using a 4 ohm 410 cabinet. Resistors are cheaper than OTs.

Its sitting on a shelf waiting to be recapped, bright switches repaired. And hopefully no new OT.

 

[ThisBass]

So you can decide if you want your signal to be squeezed by a cheap limiter or if you prefer a decent compressor to do the job...

Both limiters and compressors belong to the family of VCA signal processing tools.
I don't think that limiters are cheapy in general while compressors can be of high quality.

 

[Old Garage-Bander]

Undersized OT, and bass being played on a lapsteel amp. and sensitive to switch flippers, trying to get more sound out of an 8/16 OT using a 4 ohm 410 cabinet. Resistors are cheaper than OTs.

Its sitting on a shelf waiting to be recapped, bright switches repaired. And hopefully no new OT.

Maybe you could run that resistor out to a fuse holder for quick change.?
Remove the end caps from blown fuses and install a resistor inside the fuse cartridge?
Or put in a switch that switches to a back up resistor should it fry mid gig.

 

[Drgonzonm]

You know you have blown a resistor, when the volume drops to less than half. Then I take it out of service for a couple of months, it only takes about 10 minutes to open it up and replace the resistors.
Back up is a Kustom 300 SS amp, weighing in about 60lbs, bought for very low $$. [Yes, black tuck and roll] (I would rather have the Kustom in use, over the somewhat delicate Fender).

 

[Al Kraft]

Or put in a switch that switches to a back up resistor should it fry mid gig.

In my world we really like being able to flip a switch and engage a back-up when something goes wrong. If there's no way to design out this frequent failure with a simple modification, the switch idea is a brilliant one in my mind.

 

[Old Garage-Bander]

You know you have blown a resistor, when the volume drops to less than half. Then I take it out of service for a couple of months, it only takes about 10 minutes to open it up and replace the resistors.
Back up is a Kustom 300 SS amp, weighing in about 60lbs, bought for very low $$. [Yes, black tuck and roll] (I would rather have the Kustom in use, over the somewhat delicate Fender).

It seems you are running the amp outside of designed parameters. Not really fair to judge a whole brand of amp it as "delicate" when you do that.

 

[Old Garage-Bander]

In my world we really like being able to flip a switch and engage a back-up when something goes wrong. If there's no way to design out this frequent failure with a simple modification, the switch idea is a brilliant one in my mind.

Well if it were me, I think I'd modify the load to be within the parameters of the output impedance.

 

[Old Garage-Bander]

None of these points are exclusive to class D by the way.

Time for a new class of amplifier.
Then the naysayers and misunderstanders might quit picking on the Ds.

 

[Drgonzonm]

Well if it were me, I think I'd modify the load to be within the parameters of the output impedance.

Olivia Newon-John said it so well, about button pushing cowboys in the song "Don't play B-17" We all know knob twisters, and switch flippers.
Some amps just shouldn't be used for punk, or grunge much less some types of metal. That's my story and I am sticking to it.

 

[Old Garage-Bander]

Olivia Newon-John said it so well, about button pushing cowboys in the song "Don't play B-17" We all know knob twisters, and switch flippers.
Some amps just shouldn't be used for punk, or grunge much less some types of metal. That's my story and I am sticking to it.

I always thought that song was about pretending to be an airplane.
Now I get it. It's a song about pissing off Olivia Newtron Bomb.
That's even better than being a conventional bomber.

Let your 4 ohm cab buddies know that they'd get more out of the tube amp by matching the output impedance.
Sticking a lower ohm cab on a tube amp doesn't work like it does with SS. It just pisses them off.
"Please Mr., please, don't play 4 Ohms again..."

But hey! Cool that you have an old tuck and roll Kustom still going! I'd be rocking that as the main rig any day of the week.

 

[Drgonzonm]

For those interested in building their own low wattage class D amp, here is a link. Simple Class D Amplifier From Common ICs

 

[Deleted member 165050]

Time for a new class of amplifier.
Then the naysayers and misunderstanders might quit picking on the Ds.

I'm not picking on them, the amp I'm using just happens to be Class D and I wanted to find out if there was anything to know in the scenario I was describing... definitely not a naysayer as I much prefer the smaller more efficient gear.

 

[Drgonzonm]

.....

But hey! Cool that you have an old tuck and roll Kustom still going! I'd be rocking that as the main rig any day of the week.

I bought it real cheap at a garage sale. 20 years ago. A friend who did electronic repairs had it in his shop for about 18 months. The original owner forgot about the amp, or didn't want to pay the repair charges. The friend was closing down the shop. and This blind squirrel found an acorn. I believe I paid $10 for it.

 

[Old Garage-Bander]

I'm not picking on them, the amp I'm using just happens to be Class D and I wanted to find out if there was anything to know in the scenario I was describing... definitely not a naysayer as I much prefer the smaller more efficient gear.

Didn't say YOU were or did. Wasn't aimed at you.