Need An Amplifier That Can Make Any Speaker It's Bitch?

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Andre Marc

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Got your attention?

I received an email last month from Marc Phillips at Coleen Cardas Imports, the folks who import and distribute Opera speakers, Unison Research electronics, saying he had an integrated amplifier that could drive ANY speaker, and even had power ratings specified at 2 Ohms. I was all ears since I had two Magnepan speakers in house.

He was taking about the new Redgum Black series amps, out of Australia.

The 65wpc RGi 35 ENR ($2500), the 125wpc RGi 60 ENR ($3500) and the 175wpc RGi 120 ENR ($4500)

Marc shipped me the RGi 35 ENR, which puts out a published 90 wpc into 2 Ohms, for a formal review!

Well, I hear a lot of importer sales pitches, but Marc was not kidding. This amp is amazing. It has a passive input stage,
5 inputs, independent R/L volume controls, and it is indeed black!

IMG_1905.JPG

http://www.redgumaudio.com/product-category/black-series-amplifiers/
CCI, is now the importer of record, and should be receiving stock soon.
 

Tech Guy

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Nov 18, 2015
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Heat sinks on the BOTTOM of the amplifier!!!???

Insane. EVERYTHING inside the chassis will reach the same temperature as the output devices. Life-span of every electrolytic caps will be compromised. Bad idea.
 

Andre Marc

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Heat sinks on the BOTTOM of the amplifier!!!???

Insane. EVERYTHING inside the chassis will reach the same temperature as the output devices. Life-span of every electrolytic caps will be compromised. Bad idea.

Really? I have had it on 24/7 for ten days and it is cool as a cucumber. Armchair engineer? Interesting first post.
 

amirm

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Heat sinks on the BOTTOM of the amplifier!!!???

Insane. EVERYTHING inside the chassis will reach the same temperature as the output devices. Life-span of every electrolytic caps will be compromised. Bad idea.
It certainly a strange design. It is like a new car that has its steering pointed to the back. You can still drive it but not easily :).

I did a bit of reading and they say their amps used to be fan cooled. They then eliminated the fan and put the heatsink on the bottom.

When using a fan, the air would blow across all the components so all was well. Not so when you go to passive cooling with the heatsink. Here is the guts of it:



We can easily see the MOSFET transistors bolted to the chassis on the mid-left of the unit (3 out of four on this side visible). Here is a side shot that illustrates the problem you are mentioning:



We now see the other four MOSFET transistors but also the bulk power supply capacitors on the right with colorful wires going to the top of them. The caps are sitting right on top of the bottom plate/heatsink so directly pick up heat generated by those transistors.

Worse yet, the tops are covered so they cannot outgas easily. I expect them to fail if they do, rather catastrophically. I don't understand why they have that power supply board upside down.

We can see lack of heat management in the unit in this other shot showing the AC mains input protection and filtering:



Look on the right and find the label "IC2." That is a voltage regulator and as with all of them, can generate some heat. It is unfortunately sitting right next to that blue electrolytic capacitor with 85 degree voltage rating rather than 105.

Is this end of the world? No. They funded these amps through Indigogo to buy the heatsink casting. In there they say they are about 15 pounds each. Given the modest power output, it is not going to cook that much so will probably last a while.


Welcome to the forum by the way :).
 

Andre Marc

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It certainly a strange design. It is like a new car that has its steering pointed to the back. You can still drive it but not easily :).

I did a bit of reading and they say their amps used to be fan cooled. They then eliminated the fan and put the heatsink on the bottom.

When using a fan, the air would blow across all the components so all was well. Not so when you go to passive cooling with the heatsink. Here is the guts of it:



We can easily see the MOSFET transistors bolted to the chassis on the mid-left of the unit (3 out of four on this side visible). Here is a side shot that illustrates the problem you are mentioning:



We now see the other four MOSFET transistors but also the bulk power supply capacitors on the right with colorful wires going to the top of them. The caps are sitting right on top of the bottom plate/heatsink so directly pick up heat generated by those transistors.

Worse yet, the tops are covered so they cannot outgas easily. I expect them to fail if they do, rather catastrophically. I don't understand why they have that power supply board upside down.

We can see lack of heat management in the unit in this other shot showing the AC mains input protection and filtering:



Look on the right and find the label "IC2." That is a voltage regulator and as with all of them, can generate some heat. It is unfortunately sitting right next to that blue electrolytic capacitor with 85 degree voltage rating rather than 105.

Is this end of the world? No. They funded these amps through Indigogo to buy the heatsink casting. In there they say they are about 15 pounds each. Given the modest power output, it is not going to cook that much so will probably last a while.


Welcome to the forum by the way :).

Wrong product Amir.
 

amirm

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One more thing. Let's look at that picture again:



On the left back is the mains input and switch. Follow the blue and gray wires that bring in the AC. Note that it goes right over the speaker terminals and within shouting distance of the white RCA (!) input jack for the amp. I hope whoever uses these doesn't live in a high-surge/lightning prone area as if that surge jumps over, it will go right into your loudspeakers and pre-amp!

Again, it is not the end of the world as most of us don't face such surges. But still, it is poor design. The power supply board should have bee to the far left allowing a direct feed of that AC power to the transformer/controller board. Running AC wire over amplifier inputs and outputs is just not wise when another layout can do it better and safer.
 

amirm

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Wrong product Amir.
Same design issues Andre. The black versions are built in china sans the nice wood front panel. The heatsink is the same and I bet nothing is changed in the layout. If in doubt, pop open yours and post a picture and I will eat my words if wrong :).
 

amirm

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OK, I found the picture of the black series, this one is the lowest power unit, RGi35ENR :



Same design remains. Power transistors mounted to the bottom of the chassis and the caps upside down attached to the same chassis.
 

Tech Guy

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Nov 18, 2015
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Is this end of the world? No. They funded these amps through Indigogo to buy the heatsink casting. In there they say they are about 15 pounds each. Given the modest power output, it is not going to cook that much so will probably last a while.


Welcome to the forum by the way :).

Thanks for the welcome. And yes, the mass of the heat sink appears to be substantial, given the modest ratings of the amp. Nonetheless, there is very little in the way of convection cooling and any heat convected will be up through the chassis and keeping those electros snuggly warm. Very few engineers would design a product this way. I can assume that if the amp is subjected to the standard IHF pre-conditioning, that substantial heat sink temperatures can be expected.
 

microstrip

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May 30, 2010
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Heat sinks on the BOTTOM of the amplifier!!!???

Insane. EVERYTHING inside the chassis will reach the same temperature as the output devices. (...) .

Not the same, but perhaps rather warm. Most probably this is what the designer is aiming at. The well known Ayre MXR amplifier uses a similar strategy - the output devices are bolted to the thick massive aluminum box, that works as a large heatsink, with some grooves in the upper part. Every think inside the box is at the same temperature.
 

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GaryProtein

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I have to say, Ayre's milling procedures are just beautiful.
 

FrantzM

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Apr 20, 2010
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Hi

I also must say the design is weird. It seems to me this is the wrong way/place to put a heat sink... circuit layout as per amirm pictures doesn't seem to take account of the heat issues .....then again by the time they fail , the original owner would have moved to something newer and , of course, better sounding... ;). This is aimed at audiophiles after all :)
 

Darby

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Jun 23, 2015
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I heard the RG 65ENR Black in several systems on a wide variety of speakers. It looks and sounds like a home made kit amplifier, which may be good or bad depending on your POV, but $2.5K is really stretching credibility. Production cost from China would be minimal. There are plenty of amplifiers coming out of China that sound pretty good and many of them are half the cost of the Redgum,which doesn't even look like a Redgum, which was always its main selling point, along with the Oz made story. Now we don't have the Oz made story and the wood has morphed into generic Chinese black metal.
This eludes my buying psychology,but maybe it's just me
 

Andre Marc

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I'm calling out B U L L S H I T. Here

We get a bunch of armchair engineers who have never brought an audiophile product to market taking pot shots at a product they have NEVER HEARD. It has to stop.
it is offensive, presumptiious and down right rude, among other things.

I see TWO F U C K I N G posters (with BLANK profiles) here who MAGICALLY appear here and their FIRST G O D D AM post is to attack Redgum. I smell competitor shills or sour grapes...perhaps the ex importer?

SOMETHING IS ROTTEN.
 

Keith_W

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Mar 31, 2012
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Thanks for your contribution, Amir. Fascinating to read, and sharp eyes you have there.

BTW, Redgum amps have always been built in Australia, but I believe that the black series come out of China.
 

Andre Marc

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Thanks for your contribution, Amir. Fascinating to read, and sharp eyes you have there.

BTW, Redgum amps have always been built in Australia, but I believe that the black series come out of China.

that is not a contribution. that is unsolicited opinion on a product he ha never heard or used. and that has to stop.
 

GaryProtein

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. . . .I see TWO F U C K I N G posters (with BLANK profiles) here who MAGICALLY appear here and their FIRST G O D D AM post is to attack Redgum. I smell competitor shills or sour grapes...perhaps the ex importer? . . . .

I have attacked a number of ersatz products myself, but I have to admit, it's pretty strange for new, first time posters to both be attacking the same product within two hours of each other.
 

Darby

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Jun 23, 2015
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The use of profanity and shouting is not a particularly good method of debate. It tends to indicate bias and emotion which is un necessary and in this case hypocritical. Calling peo[ple who have opposing views to one's own shiils or armchair engineers achieves nothing.
This seems like a free and intelligent forum and one would think all views would be able to be posted so long as they are not defamatory or malicious, neither of which, have been evident in this thread so far.
Name calling needs to stop
I'm calling out B U L L S H I T. Here

We get a bunch of armchair engineers who have never brought an audiophile product to market taking pot shots at a product they have NEVER HEARD. It has to stop.
it is offensive, presumptiious and down right rude, among other things.

I see TWO F U C K I N G posters (with BLANK profiles) here who MAGICALLY appear here and their FIRST G O D D AM post is to attack Redgum. I smell competitor shills or sour grapes...perhaps the ex importer?

SOMETHING IS ROTTEN.
 
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