Class D power supply (and other) questions

[bill mountain]

I am designing a DIY bass guitar amp. I have tested several preamp designs that I like but, I have not settled on a power section yet. I have been looking at class AB stuff mostly because my favorite amps have all been AB. I had a discussion with an engineer friend of mine about how old school solid state amps were so much more robust than similarly rated amps today. I attributed this to the transistors but he suggested that it could have been the power supply. Some of those solid state power transformers still weighed as much as tube ones (20+ lbs)!


This got me thinking. If I used a similarly overbuilt power supply with a class D module would I get similar results? And by results I mean a 300 watt amp that sounds full and still has headroom at 300 watts


I’m looking for depth and headroom not just volume (if that makes any sense?).


My wattage needs are around 300 watts at 4 ohms.


I would love to be able to do 2 ohm (just like some of my favorite amps) but most module companies I have spoken to (with class D or mosfet/bipolar AB modules) do not recommend it. I spoke with someone at cold amp who suggested ways to hook it up for 2 ohm operation but I didn’t get the feeling that it would be very stable.


You just can’t argue with the low cost, low weight, high efficiency, and ease of use with class d modules.


My basic idea was to use a higher wattage module with a lower VA linear power supply. I am not extremely technical but I believe that this will keep me from stressing the module and just leave me with clean volume (up to the power of my transformer).


Am I crazy? Should I find another hobby?

[Eva]

The point of class D and SMPS is getting rid of 20lbs of 50/60Hz transformers and 20lbs of heatsinks in high power amplifiers. Anything not used in a fixed setup benefits from that.

This does not necessarily involve a reduction in performance. Too much capitalism, global crisis and excessively optimistic designers are the ones to blame for that. For example the class D stuff that I do is capable of 1/3 power into 2 ohms with no time limit, like the best old school amplifiers, and still very competitive in terms of size and weight, but it will take a few years to be available for DIY.

Since finding good 2 ohm class D is as difficult as finding 2 ohm speakers, consider one or two SMPS and two 4 ohm class D modules driving 2-4 speakers...

Conventional 50/60Hz transformers are pointless, they ruin the weight reduction due to class D.

[bill mountain]

Originally Posted by Eva

The point of class D and SMPS is getting rid of 20lbs of 50/60Hz transformers and 20lbs of heatsinks in high power amplifiers. Anything not used in a fixed setup benefits from that.

This does not necessarily involve a reduction in performance. Too much capitalism, global crisis and excessively optimistic designers are the ones to blame for that. For example the class D stuff that I do is capable of 1/3 power into 2 ohms with no time limit, like the best old school amplifiers, and still very competitive in terms of size and weight.

What class d stuff are you using?

I don't need 2 ohm capability for myself. I am thinking about friends of mine with 2 ohm rigs (multiple 4 ohm cabs) and I want them to be able to try my amp.

I'm not worried about weight. I like that class D runs cooler and seems pretty easy to build with.

I'm just doing what everyone else on here does and try to dissect their favorite amps to see what parts makes them so good.

This week I'm stuck on power supplies and amp modules. Next week I may be looking at preamps again.

I wish my journey were more linear!

[bill mountain]

I just found this module:

Class D Audio TI-600 Amplifier - Class D Audio Amplifiers - PRODUCTS

This appears to run 2ohm loads so I may be set.

[nigelwright7557]

Originally Posted by bill mountain

I'm not worried about weight. I like that class D runs cooler and seems pretty easy to build with.

Class d is easy to build with using tried and tested modules.
I went the "design my own" route and came across a few problems with class d like inductor selection, pcb layout and decoupling issues.

Class d makes use of fewer components and a lesser heatsink to get the same power as class AB.

[bill mountain]

Originally Posted by nigelwright7557

.

Class d makes use of fewer components and a lesser heatsink to get the same power as class AB.

This is what attracts me to class d!

[alleycat]

Couldn't get simpler than this:
Connexelectronic
Just hook up mains power and away you go!

[bill mountain]

Ive been checking that site out. I am not interested in stereo or a switching supply at this moment but that would be a super simple setup.

[gpontchar]

Have a look at: 41Hz Audio:Sounds Good to Me!
(Tripath technology DIY)

[ZFRaudio]

Originally Posted by bill mountain

I just found this module:

Class D Audio TI-600 Amplifier - Class D Audio Amplifiers - PRODUCTS

This appears to run 2ohm loads so I may be set.

why on earth would you want to run at 2 ohms?

you may as well short circuit your amplifiers.....

as for that amplifier, it can run into overcurrent protect into a "2 ohm load", as these loads can dip as low as 1ohm depending on the crossover networks and woofers involved

i would stay well away from running anything in 2 ohms

with my PA setup i have large format class AB amplifiers that are 2ohm capable, but the amount of stress they they place on componentry just shortens the lifespan too much. as the amplifier I own has been proven to draw 29A off a 240v supply on the bench, then this sheer amount of current anywhere on circuitboard is asking for trouble! (Even if it is capable)

the problem is even worse when you are runnning off low voltage rails as the current is increased (dependant on output power of course)