Anyone interested in a low cost DC blocker box?

avahifi · « **on:** 14 Jan 2013, 07:41 pm »

PS Audio used to offer a device they called the Humbuster which blocked low level DC on AC power lines and magically quieted noisy toroid power transformers in audio equipment. The retail price was $400 or thereabouts as I remember.

We have come up with a device providing the same DC blocking function but with an alternate and more economical design that could be available for $195 if there is sufficient interest to justify the up front tooling cost for the actual chassis. The actual cost of the metal box, a purpose made metal enclosure, about 6 inches long x 4.5 inches wide x 2.5 inches high with an IEC AC socket and two line fuses on one end and two three conductor AC outlets on the other end, with a black powder coat finish, is the most expensive part of the equation in small quantity. The two fuses are to protect both the incoming AC hot and neutral conductors separately. The circuit will handle a big power amp and accessory equipment too.

If you have any audio equipment with annoying mechanical hum from your chassis (not from the speakers) then you could certainly benefit from this device which we are thinking of calling the AVA HumDinger!

Please let us know if you are interested. If we get enough support, we will tool and build it for you.

Regards,

Frank Van Alstine

roscoeiii · « **Reply #1 on:** 14 Jan 2013, 07:49 pm »

Great to see this being suggested. When I had DC on the line in my old apt, the Humbuster saved the day. Channel Islands also made a product to remove DC on the line that was also a bit over $300. Here's hoping this comes to light for those with this power problem.

Devil Doc · « **Reply #2 on:** 14 Jan 2013, 08:16 pm »

I do have a mechanical hum coming from my Insight+250, but it doesn't have a toroidal transformer. If it would indeed kill that hum I would buy a Humdinger in a heart beat.

Doc

JerryM · « **Reply #3 on:** 14 Jan 2013, 08:20 pm »

cheap-Jack · « **Reply #4 on:** 14 Jan 2013, 08:47 pm »

Hi,

Quote from: avahifi on 14 Jan 2013, 07:41 pm

PS Audio used to offer a device they called the Humbuster which blocked low level DC on AC power lines and magically quieted noisy toroid power transformers in audio equipment. The retail price was $400 or thereabouts as I remember.

We have come up with a device providing the same DC blocking function but with an alternate and more economical design .you could certainly benefit from this device which we are thinking of calling the AVA HumDinger!

Please let us know if you are interested. If we get enough support, we will tool and build it for you.

Regards,

Frank Van Alstine

Yes, DC blocker are useful to stop DC offset on the powerlines from entering our amps. For most EI type power irons can still handle minor decimal voltage DC offset due to their airgapped EI cores

But for toroidal power irons of no airgap design, any DC offsets from the powerline will heat up the iron & get noise - no good!

A DC blocker can easily be DIYed using 2 sand diodes connected in series, head-on, each bypassed by a
capacitors of large capacitance & low voltage, hooked up to the live line.

Many use 'lytic caps of large capacitance & low voltage (cheapie). But I don't like the idea of using DC rated 'lytic caps used in series of the (live) powerline to provide passage for AC currents to pass thru to power the audio components, DC/DVD players, preamps or power amps.

I would definitely use AC rated caps of adequate capacitance depending on the power loading of the component.

Such super simple DC blocker, comprising 2 sand diodes & 2 AC rated caps would cost me very little money depending on the cost of the AC bypassing caps. A couple of ten bucks, maybe plus the cost of a small
plastic case.

c-J

Rclark · « **Reply #5 on:** 14 Jan 2013, 09:08 pm »

Just to make you aware of it, Emotiva has one that is often on sale, in fact I never see it at "full" price. It is also very well regarded.

http://shop.emotiva.com/collections/accessories/products/cmx2

cheap-Jack · « **Reply #6 on:** 15 Jan 2013, 02:06 pm »

Hi.

Quote from: Rclark on 14 Jan 2013, 09:08 pm

Just to make you aware of it, Emotiva has one that is often on sale, in fact I never see it at "full" price. It is also very well regarded.

http://shop.emotiva.com/collections/accessories/products/cmx2

So it is a line filter + DC blocker.

Thank goodness, I can DIY both to save some nice bucks.

c-J

roscoeiii · « **Reply #7 on:** 15 Jan 2013, 03:00 pm »

But not everyone is comfortable DIYing, congrats for having the ability and confidence to do this. But Frank's proposed device could be great for the rest of us.

cheap-Jack · « **Reply #8 on:** 15 Jan 2013, 03:04 pm »

HI.

Quote from: roscoeiii on 15 Jan 2013, 03:00 pm

But not everyone is comfortable DIYing, congrats for having the ability and confidence to do this. But Frank's proposed device could be great for the rest of us.

Thanks for yr complements. This is what I call "total involvement" - design+build+auditioning!

So keep on financing the vendors if one can't DIY. This will keep the economy running.

c-J

werd · « **Reply #9 on:** 15 Jan 2013, 03:36 pm »

Quote from: cheap-Jack on 15 Jan 2013, 03:04 pm

HI.
Thanks for yr complements. This is what I call "total involvement" - design+build+auditioning!

So keep on financing the vendors if one can't DIY. This will keep the economy running.

c-J

Ok but you could be stuck with something that sounds like crap. And its hard to go out and buy something thereafter once you started down that road. You could be just nerfing your own enjoyment out of ego. "Got to listen to mine i built it."

That was the reason why i did the Eset course at Siast. in Saskatoon , was to DIY. I wanted to build amps. I finished the Eset and was asked to come back and do the ESAT course which is a 2 year course that many many EEs can't do. They cant get past the 2nd year.

The ESET course was frickn hard with a full fam and holding down a job. It was a very hard schedule for a full time student never mind a job and a fam,and it was just too much. Esat course was worse, basically a 4 year EE diploma crammed into 2 years. lol.

But what the cruncher was the amount of time it took to build amps. That was it, you start tinkering with stuff, got a couple of power supplies built and was starting to read about stages and then i realized. Holy shit i wasting my time here. I am doing this to enjoy music and guess what. I am not enjoying music any more i am wasting my time building stuff....lol. With me i am pretty finnicky with what i like, i just wont except anything. I could spend years literally screwing with this. OF course you get the incite and knowledge but really what a sucker punch to the hobby. It really is.

underdawg · « **Reply #10 on:** 15 Jan 2013, 03:37 pm »

I would be interested Frank, can you make a kit version available?

Speedskater · « **Reply #11 on:** 15 Jan 2013, 03:49 pm »

Fuses on Neutrals are not permitted. A dual linked breaker is OK, but not a Neutral fuse. If that fuse blows the whole enclosure can be hot.

rollo · « **Reply #12 on:** 15 Jan 2013, 06:48 pm »

Frank, excellent idea. Why an IEC though ? A short hardwired AC cord would be simple. If one is using this device and a conditioner having a hard wired cord just makes sense.

charles

resonance · « **Reply #13 on:** 15 Jan 2013, 09:44 pm »

I too have a mechanical hum on my new Synergy 240/3 and Fet Valve 400R. Both get louder when switching the Chassis Ground toggle to On. HumDinger of a humbuster might work??? Greatly interested.

David

avahifi · « **Reply #14 on:** 15 Jan 2013, 09:58 pm »

Actually we ordered the $75 Emotiva unit today to evaluate and dissect. If it works as well as what were were thinking about, then there would be no point in us building one as we could not compete with their Oriental price.

Resonance, you might try the Emotiva unit for $75 including free shipping. If it works, great.

We will see.

Frank

dB Cooper · « **Reply #15 on:** 15 Jan 2013, 10:02 pm »

I once had an AVA power amp that had this mechanical hum. AVA replaced the power transformer even though the unit was recently out of warranty and they were unable to replicate the issue. Sounds like this might be why. (They were under absolutely no obligation to do that, one of many reasons they are the best company out there to do business with.)

rlee8394 · « **Reply #16 on:** 15 Jan 2013, 10:10 pm »

Of course, some may want more than two outlets.

Ron

rlee8394 · « **Reply #17 on:** 16 Jan 2013, 01:19 am »

Wow Frank,

They must know you. Price is now $99.00.

Ron

P.S. They have a six outlet unit, CMX-6, but it doesn't look like it has the Precision DC offset eliminator.

vortrex · « **Reply #18 on:** 16 Jan 2013, 01:27 am »

Quote from: rlee8394 on 16 Jan 2013, 01:19 am

Wow Frank,

They must know you. Price is now $99.00.

Ron

P.S. They have a six outlet unit, CMX-6, but it doesn't look like it has the Precision DC offset eliminator.

their site is messed up. it's supposed to be $75, but when you add it to the cart it is $99. you can get it through them via amazon for $75 with free shipping.

rlee8394 · « **Reply #19 on:** 16 Jan 2013, 01:45 am »

Looks like they updated the Amazon site as well.$99.00