D-Fend

[Radian]

How often do Valve amplifiers produce enough power to blow their drivers?

[Gregory East]

100W will blow most comers at low enough frequency, just saying...

With these D fend things in the cab it seems to take away the need for your normal "one high pass fits all" filter.

If you're say powering a 15 with a 300W Traynor and no high pass then a open B string would be making a lot of high powered filtered 30Hz from the (tube)amp and that's possibly a bad ideatm if it's diverting it off into a high load

[r23d]

I imagine there will be "default" settings for each Eminence driver that could then be adjusted if needed. I can't imagine all the tech details will appeal to guys who just want a no-brainer solution to protecting drivers. Pretty ideal for us speaker tweakers though...

I've been quizzing josh.martin@eminence.com and he is happy for me to share this info :

"D-fend will be available in 3 forms for end-users. It will be available as the "raw" board that you see in the pictures with a small heat sink on the back with mounting holes. It will also come in a stand-alone unit, much like the size and configuration of a standard direct box. This units will have mounting holes or brackets as well. And thirdly, it will come in 4 and 8 channel rack mount units.

We have been targeting OEMs with this technology but are in the process of getting these other units available as well. Right now, we are designing the chassis for the rack mount and stand alone unit. Our goal is to have these on the market by the end of the year. The "raw" board could be available a little sooner as it will not need the chassis. I have a list of folks that I am going to contact when each of these units become available. I will go ahead and put you on that list so that we can keep you up to date with our progress.

Thanks again for the interest. We'll be keeping you informed as time gets closer. If you have any more questions, feel free to contact us. Thanks! Take care!"

And this (maybe outdated info) :

"With regards to your questions........At this point, we are unsure of the final price point. We are finishing up the final revisions to the board itself. As it stands right now, the board is programmed using a Texas Instruments developmental tool. It's not really user friendly so we are in the process of placing a USB connection on the board to make programming easier and less expensive. I wish I could give you a figure but anything would just be a guess. Our goal is to keep this cost effective and a viable option for consumers.

D-fend allows you to program attack and release times across multiple bands in order to "milk" your driver for all it's worth without damaging it.

The D-fend unit has 3 LED lights on it as well to indicate when each of the programmed settings have been reached and the unit is protecting. We will have some demonstration videos up on the web very soon. I will be sure to email you when those are up as well.

Basically, D-fend digitally changes the impedance load that the amplifier sees. Once the unit is programmed, it sits in the signal chain and does not affect anything that passes through it. When it sees the need to protect, it turns on and digitally raises the impedance of the load so it simply doesn't ask the amplifier for the power. This in turn means that there is no excessive power to get rid of resulting in virtually no heat. It also means that the amplifier is not working as hard or having to pull as much current itself. It's a win-win situation."

I think Leeland will be first on the list when they're available...

cheers,
Rich.

[r23d]

I also asked Josh if the unit was capable of operating as a HP/BP/LP filter, but sadly no. Wishful thinking?

[Dan30]

Bump. I see on the eminence website that it's in a rectangular form factor instead of the round one? Any news on the status of it?

[BoostFab]

that's great.... thanks for sharing.

[LelandCrooks]

My appointment with eminence is tomorrow. I will have all the skinny on this thing. I'm excited for it, and it's the primary reason I'm at NAMM this year.

[Dan30]

Thanks Leland I look forward to the news. Have fun at NAMM too. If you don't want to pay for parking then park in the neighborhood behind the Taco Bell. It's a somewhat short walk from there.

[SirNickity]

Huh. So how do you think it works? Power transistor(s) with the gate driven by a microprocessor monitoring signal voltage? Perhaps switched resistance ala a stepped passive attenuator, but with digital switching? First one to buy it should post naked pictures.

[la80vette]

A prototype in my T39 would be great.
Stephen

[LelandCrooks]

It steps impedance. The amplifier never delivers the voltage over the setting. It just never produces it, that's how they get away with very small heat sinks.

I asked about tube amps, which are current rather than voltage, and they're working on it. The designer is pretty sure he can trick the unit with a small addition to the circuit, and may be able to do it just from software. The new form factor is very small. As is true with everything else at NAMM, not available til Mid May. I told everybody in sight I wanted to be right at the front of the line for these. I took pics, and they're horrible. I'll take some more today.

And, also in Mid May, the 3010lf is coming to market.

[Gregory East]

I thought by ramping up impedance the current from over voltage was reduced? Voltage being unaffected.

[SirNickity]

There would be a voltage drop across the resistance of the Dfend, thus reducing current through the circuit.

[loudsubz]

anyone know when this will be available?

[LelandCrooks]

Stand alone rack units will be here quick. In cab models I don't know.