Guardian-86 and Guardian-686: High-End Speaker Protection Circuits

[tomchr]

Mains is ±235V with 2× 25 VAC 150 VA power transformers with ±27.5 of secondary output what gives me ±36.5V out of V Power-686.
I had 2×24 VAC Hammond before, which I had on a shelf from other project, but it was so bloody noisy and I replaced it with Toroidy ones.

Toroidy makes good stuff.

I'm still puzzled that you had issues with speaker pops on the MOD286. I've built several and they've all powered up and down quietly. Are you using an unbalanced source and pseudo-differential connection by any chance?

Tom

 

[Stony]

Are you using an unbalanced source and pseudo-differential connection by any chance?

Tom

No, I m not
Stef

 

[tomchr]

Hmmm... Does the source stay on when the power amp is turned off or are they turned off at the same time?

Tom

 

[Stony]

Switching it off before the amp doesn't help.
I have got some suspicion let me check it. I let you know
Stef

 

[tomchr]

Now this... The Guardian-86 Rev. 2.0 just launched.

Major improvements over Rev. 1.0:

• Works without modifications on any amp power by ±15 to ±90 V (or single-ended amps powered by +15 to +90 V).
• Works with all amplifier types: Single-ended and bridged/BTL.
• Smaller footprint (40 x 45 x 27 mm; W x D x H).
• Automatic sensing of the power supply and automatic disabling of the output once the power supply voltage drops to 2/3 of its nominal value. This eliminates clicks and pops on power-down.

The Guardian-86 is $99/each and is only available as a fully assembled module. This allows me to provide a better product at a lower cost to a broader market. The Guardian-86 is a mono board. Two are needed for stereo.

The Guardian-686 will be discontinued once the current stock has sold. I have six fully assembled Guardian-686 in stock and on sale at $169/each (reg. $199/each). I also have a good handful of the bare boards in stock. Shop the sale here: https://neurochrome.com/products/guardian-686

You can read more about the Guardian-86 here: https://neurochrome.com/products/guardian-86

Tom

 

[tomchr]

Here's how you connect the Guardian-86:

Tom

 

[wcwc]

Looks like I should get on with ordering two of those Guardian-686 bare boards since I already have most of the parts for it short of the mosfets.

The new guardian-86 boards look good. For the old ones, does it do the autosensing and autodisabling of the power? What is the older ones voltage range?

 

[tomchr]

The Guardian-86 Rev. 1.0 and Guardian-686 do not have the auto-sensing of the supply voltage. You set the trip point with a zener diode, but it's not super precise. Basically the Guardian browns out and turns off. In the Guardian-86 Rev. 2.0 there's a comparator that compares the supply voltage with 2/3 of the sensed nominal voltage. Once the power supply crosses that 2/3 threshold, the MOSFETs are turned off and the speaker is disconnected.

The Guardian-86 Rev. 1.0 and Guardian-686 will work without modifications up to 45 V. If you want to go higher than that you need to swap a zener diode.

Tom

 

[wcwc]

So for my amp that I am trying a bunch of amp pcbs with varying rail voltages, it looks like the new guardian-86 would be the most plug and play. The older ones would require swapping diodes to get to work properly. Good to know.

 

[tomchr]

Yep. The new Guardian-86 (Rev. 2.0) would be plug-and-play. Guardian-86 Rev. 2.0 also works with both single-ended amps and with amps that have floating outputs (bridged/BTL and Circlotron circuits).

Tom