Crown / Amcron DC300A - another thread about DC protection

[thomasdf]

Hi all

I am about to get a DC300A amp in overall good condition to drive my Urei 809 monitors. I know these are pretty reliable amps and I intend to fully recap it, but I'd be sad if it fried my freshly rebuilt 809s if it ever failed. So I'm looking at solution for DC protection.
- I read a lot of things about crowbars inspired by a Peavey amp, still haven't figured it out completely.
- And then I found this : Complete Speaker Protection Circuit – Electronics Projects Circuits
What do you think about this design ?

Any other info / pointers welcome ! Thanks in advance, and happy new year

thomas

 

[Khron]

I'd kinda lean towards Rod Elliott's stuff, but i'm a bit biased (no pun intended, though).

https://sound-au.com/project33.htm

 

[thomasdf]

Thanks for the link it is very interesting ! Too bad the shipping from Australia is so expensive.
I'll read some more
The last design with the MOSFET relays seem very appropriate since it won't risk arc like with a traditionnal relay

 

[JohnRoberts]

I am not a fan of the DC300. Even when working properly it is not very fast or clean, and a DC fault in a stage upstream could still cause a properly working DC300 to put DC on your speakers.

The circular pursuit about engineering in speaker protection is if you know what the fault is likely to be, just prevent that fault from happening. In the case of the DC300 the fault inherent in the design is that it is DC coupled. It should not be heavy lifting to incorporate a HPF into the amplifier input stage to prevent DC at it's input from smoking your speakers (a crude old school passive approach is to just add capacitors in between amp and speakers).

The ESP relay protection scheme is interesting. I might be tempted to suggest making a free standing relay box that you can keep and use after you discard the DC300.

JR

 

[guy_4]

Hello,
I considère mandatory to have a DC protection on any power amp. The Amcron DC300 is famous for the burning of many speakers, thanks to S/C of the power transistors sending 1/2 of the power supply in the voice coil.. I have modded several amps ( Phase Linear, old Bryston, etc…) with Kits from Ebay, they use à dedicated IC and 2 relays. Easy to do for cheap, $20.
Also Velleman has a kit that is perfect.
See my post of Oct 2019, 31.

 

[thomasdf]

yeah, the DC300a really has its fans and haters... I've worked with it in the past and liked it and would like to give it a chance in my setup, as with monitoring I am never looking for something perfect, but for something inspiring

If the Velleman kit is working great I might go for it, it's easy to get.