Krell Introduces new iBias Class A Amplifier Line Preview

[itschris]

Gaudy. Ostentatious. Proud of it. Damn straight.

I love MAC, but those logos on the mono power supplies are attrocious. I'd actually not buy them because of it. Everything else I love. Like I said... MAC the classiest, Krell the toughest, JR the sexiest. I stand by my assertion and all who disagree are foolish poeple with no taste.

 

[TLS Guy]

It is different in that the bias current is raised and lowered according to the input voltage, with circuitry with a fast slew rate. There isn't a fixed bias level, there's a range. I'm not sure if the "sliding bias" technique is elegant per se, and it certainly isn't as novel as the current dumping design. One could argue that both of these techniques are overkill these days, as it is possible to build amplifiers of very high quality without either one.

I think all of us technical types are well aware of how Walker's amplifier design works (and we're all aware of your hero worship of Walker). Current dumping is an ingenious design, and I've never heard anyone deny its value, but it is not the only design strategy capable of very low distortion, and amplifiers using current dumping are not available at high power levels (or reasonable prices per watt, for that matter).

The 909 is 250 watts per channel into four ohms. The really nice thing about the current dumpers is the very low part count. Also components do not need to be high tolerance and there is a lot of room for components to wander out of spec. without affecting performance.

So it is in the customers interest. If receivers were built with current dumpers, they would make less heat and the amp boards would have a much smaller footprint and could be produced at less cost. Reliability would also soar because of these issues.

Here is an amp board of a Quad 909. It only has a fraction of the part count of any other amp I'm aware of.

There is no reason larger amps could not be designed. If produced with economies of scale, it would probably come out lowest on cost per watt.

 

[Irvrobinson]

The 909 is 250 watts per channel into four ohms. The really nice thing about the current dumpers is the very low part count. Also components do not need to be high tolerance and there is a lot of room for components to wander out of spec. without affecting performance.

So it is in the customers interest. If receivers were built with current dumpers, they would make less heat and the amp boards would have a much smaller footprint and could be produced at less cost. Reliability would also soar because of these issues.

Here is an amp board of a Quad 909. It only has a fraction of the part count of any other amp I'm aware of.
There is no reason larger amps could not be designed. If produced with economies of scale, it would probably come out lowest on cost per watt.

Like I said, Doc, I'm not arguing (nor has anyone else) about the merits of the current dumping design, but whether you know it or not you have a habit of discounting any other strategy, and there are several valid ones. Anyway, the amps we're discussing here, a Krell for heavens sake, are ultra-high-end niche products aimed at people who want amps designed like WWII battleships. Subtle technical arguments do not sell amps in this market. Sigh and groan if you must, but to me widely varying preferences makes the world a more interesting place.

 

[RichB]

^^^

Is there a downside of current dumping amps?
Why aren't they being produced?

- Rich

 

[Irvrobinson]

^^^

Is there a downside of current dumping amps?
Why aren't they being produced?

- Rich

I can't think of a downside. The design is patented. To my knowledge only Quad produces them, and Threshold stopped producing the variant that Nelson Pass patented.

 

[ImcLoud]

I had a quad 909 and 99, a local shoppe offered me $1800 for them a while back and I sold them, I hadn't used them in a while because I was getting a buzz when no music was playing.. Nice stuff though, I always liked quad and I still have a pair of 303's that work nice, but I don't use them anymore either...

When it comes to amps, I want affordable, durable, and powerful, I have compared a lot of amps and never heard a properly working unit have an audible distortion, I think the entire "high cost" amp scene is non sense, BUT don't get me wrong, I would love to have some mc labs, heck I even like the carver 305 tube mono blocks, if aesthetics mean nothing to you, then get a crown xls put it in a closed rack so you don't see the lights or hear the fan and call it a day, but most of us like the name and the looks of the expensive stuff, I almost bought a set of the carver black beauties off of Dan from emo for $5500 but couldn't talk my self into it, since I just finished the rack for my xpa2... Although them big glowing tubes would look really nice in my living room, definitely wouldn't sound as good as my xpa2, but look wise they would make me smile every time I fired them up...

 

[Irvrobinson]

I do like this picture... look at those ancient T0-3 power transistors. That's what transistors are supposed to look like; new designs look boring, even though they're technically much superior. In the old Threshold Stasis amps (which also used a current dumping strategy) Nelson Pass used to line up the T0-3 cases down the side-panel heat sinks like opposing armies, sometimes 64 of them per channel. I've considered buying those amps (now used) once or twice, just to gaze at the circuitry. How good is the new stuff? The ATI AT3002 has more power (and seems to measure better) than the Threshold SA12e I was just talking about. And the 7 channel AT3007 version weighs less than a single SA12e monoblock, but it doesn't look anywhere near as sexy.

 

[jinjuku]

I do like this picture... look at those ancient T0-3 power transistors. That's what transistors are supposed to look like; new designs look boring, even though they're technically much superior. In the old Threshold Stasis amps (which also used a current dumping strategy) Nelson Pass used to line up the T0-3 cases down the side-panel heat sinks like opposing armies, sometimes 64 of them per channel. I've considered buying those amps (now used) once or twice, just to gaze at the circuitry. How good is the new stuff? The ATI AT3002 has more power (and seems to measure better) than the Threshold SA12e I was just talking about. And the 7 channel AT3007 version weighs less than a single SA12e monoblock, but it doesn't look anywhere near as sexy.

Next we are going to talking about how to get Windows 8 installed on a HP PDP 11

 

[Irvrobinson]

Next we are going to talking about how to get Windows 8 installed on a HP PDP 11

Converting Win8 to 16bit addressing might be a challenge...

 

[TLS Guy]

I do like this picture... look at those ancient T0-3 power transistors. That's what transistors are supposed to look like; new designs look boring, even though they're technically much superior. In the old Threshold Stasis amps (which also used a current dumping strategy) Nelson Pass used to line up the T0-3 cases down the side-panel heat sinks like opposing armies, sometimes 64 of them per channel. I've considered buying those amps (now used) once or twice, just to gaze at the circuitry. How good is the new stuff? The ATI AT3002 has more power (and seems to measure better) than the Threshold SA12e I was just talking about. And the 7 channel AT3007 version weighs less than a single SA12e monoblock, but it doesn't look anywhere near as sexy.

3 KW of current dumping power for the studio. Love it!

Here is a picture of the replacement of the 909, the QSP, sporting tiny modern devices. The amp costs 25% more and is less powerful. It seems to have driven the price of used 909s through the roof.

 

[Irvrobinson]

3 KW of current dumping power for the studio. Love it!

Here is a picture of the replacement of the 909, the QSP, sporting tiny modern devices. The amp costs 25% more and is less powerful. It seems to have driven the price of used 909s through the roof.

Your set-up is very cool. The clips Quad is using in the newer amp to hold the power transistors to the heat sink is not cool, no pun intended. They look like the same clips used to hold some automotive mud flaps in place. Ugh.

 

[TLS Guy]

Your set-up is very cool. The clips Quad is using in the newer amp to hold the power transistors to the heat sink is not cool, no pun intended. They look like the same clips used to hold some automotive mud flaps in place. Ugh.

I know it looks really tatty. Peter has been dead for a number of years now. The 909 had his definite stamp on it. I have been careful to buy older used models made in Huntingdon. The Chinese factory have apparently caused a buzz by not building the ground plane correctly.

So on it goes, the Chinese continue to reduce my quality of life on all fronts.

 

[Adam]

So on it goes, the Chinese continue to reduce my quality of life on all fronts.

I take it that you aren't a fan of Mongolian Chicken? Oh, baby. That's the stuff.

I'm guessing that they have improved my quality of life overall, at least in the near term. While the build quality of some gear has reduced, the price of a lot of stuff has dropped - making it affordable for me to buy some things that I wanted. I'm not about to argue if the long-term impact of moving production to China is good or bad, as I simply don't know.

But back to that Mongolian Chicken. Mmmm, spicey.

 

[Irvrobinson]

I'm guessing that they have improved my quality of life overall, at least in the near term. While the build quality of some gear has reduced, the price of a lot of stuff has dropped - making it affordable for me to buy some things that I wanted. I'm not about to argue if the long-term impact of moving production to China is good or bad, as I simply don't know.

There are very few shades of gray in TLSGuy's world. Mostly black and white. The problem is Quad themselves, not the Chinese subcontractor. They'll build anything the customer wants, including fully CNC-machined heat sinks with custom slots for the bipolars. Whether or not it's a great idea for the world to take advantage of cheap labor and non-existent zoning and environmental laws is a different question, but IMO the Chinese can build very high quality electronics. For example, the iPhone 5S, which is built like a Hublot watch, is made in China.

 

[Adam]

There are very few shades of gray in TLSGuy's world.

You don't say.

 

[TLS Guy]

There are very few shades of gray in TLSGuy's world. Mostly black and white. The problem is Quad themselves, not the Chinese subcontractor. They'll build anything the customer wants, including fully CNC-machined heat sinks with custom slots for the bipolars. Whether or not it's a great idea for the world to take advantage of cheap labor and non-existent zoning and environmental laws is a different question, but IMO the Chinese can build very high quality electronics. For example, the iPhone 5S, which is built like a Hublot watch, is made in China.

Quad has been owned for some time by the Chinese manufacturer International Audio Group, owned by two Taiwanese brothers, Michael and Bernard Chang, so there you have it. The golden age of British Audio is now a fond memory long fading in the rear view mirror.

My Droid X is made in America and beats an iPhone 5S hands down. Even my son who owns a 5S admits that.

Having said that, their electronics manufacture is probably the best of what they do, it is all down hill after that. My rap sheet against them is really extensive. People twist my arm to repair a lot of their junk and I get to see their malfeasance up close.

 

[TLS Guy]

I take it that you aren't a fan of Mongolian Chicken? Oh, baby. That's the stuff.

I'm guessing that they have improved my quality of life overall, at least in the near term. While the build quality of some gear has reduced, the price of a lot of stuff has dropped - making it affordable for me to buy some things that I wanted. I'm not about to argue if the long-term impact of moving production to China is good or bad, as I simply don't know.

But back to that Mongolian Chicken. Mmmm, spicey.

You seem to have vented your spleen recently on some Chinese built amps.

When it comes to spiced dishes in my view Indian can not be beaten. Oh for the Raj.

 

[Adam]

You seem to have vented your spleen recently on some Chinese built amps.

When it comes to spiced dishes in my view Indian can not be beaten. Oh for the Raj.

Oh, I didn't say that everything they make is perfect , but my main problem was with the Americans who sold them to me. As I've said, though, the fit and finish on those amps was very good.

Indian, eh? I sense that your spice tolerance is far higher than mine. I throw down some Americanized "spicey" Chinese food, and my nose is watering.

 

[slipperybidness]

I had a quad 909 and 99, a local shoppe offered me $1800 for them a while back and I sold them, I hadn't used them in a while because I was getting a buzz when no music was playing.. Nice stuff though, I always liked quad and I still have a pair of 303's that work nice, but I don't use them anymore either...

When it comes to amps, I want affordable, durable, and powerful, I have compared a lot of amps and never heard a properly working unit have an audible distortion, I think the entire "high cost" amp scene is non sense, BUT don't get me wrong, I would love to have some mc labs, heck I even like the carver 305 tube mono blocks, if aesthetics mean nothing to you, then get a crown xls put it in a closed rack so you don't see the lights or hear the fan and call it a day, but most of us like the name and the looks of the expensive stuff, I almost bought a set of the carver black beauties off of Dan from emo for $5500 but couldn't talk my self into it, since I just finished the rack for my xpa2... Although them big glowing tubes would look really nice in my living room, definitely wouldn't sound as good as my xpa2, but look wise they would make me smile every time I fired them up...

What brand of tubes to you prefer? Where do you buy them?

 

[ImcLoud]

Last tubes I bought were electro harmonix el34's and ecc83's, they cost me $120 from ebay... I try to buy the cheapest tubes i can find....