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The Rogue Cronus Magnum Integrated Tube Amp has been around for a while. It has been reviewed in several publications and received a few awards... it is a highly regarded integrated tube amp.



The Cronus Magnum is part of the Rogue Titian series of tube amplifiers. Rogue set out with an engineering challenge to create a truly high end amp at what is considered entry level pricing. It offers outstanding performance and excellent build quality, assembled to the same exacting standards as their most expensive amplifiers... built entirely in the USA.

The few things I found lacking on the Cronus Magnum are XLR balanced inputs and the fact that you have to open up the chassis to change to a 4ohm speaker load.

Features
  • All precision components
  • Built in bias meter on amplifiers makes biasing a snap
  • Fully tested, burned in, and auditioned
  • Available in Anodized Black or Natural Silver
  • Power requirements: 115V/60Hz
  • 3 year limited warranty (6 months on tubes)
  • MSRP $2,195
Specifications
  • 100WPC Magnum
  • 20Hz-30Khz bandwidth
  • KT120 output tubes, 12AU7 and 12AX7 small signal tubes
  • Phono section gain 35dB (before preamp)
  • (3) line level inputs, (1) phono input
  • (1) variable output, (1) fixed output
  • Headphone amplifier
  • 4 and 8 ohm taps
  • Remote volume control included
  • Optional tube cage
  • 18” W X 17.5” D X 5.5” H
  • 50 lbs (55lbs shipping weight)

This is one of the tube amps I have considered for my two channel system.
 

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Is there a schematic available for that amp? It would be fun to see what's in the design, if it's based on classic designs with very little in the way of solid state devices used, if it has classic passive power supplies or more contemporary regulated power supplies, or if it uses transistorized current sources and sinks on the tubes, that kind of thing.

I noticed it uses KT120 tubes as the output tubes, with 12AX7 and 12AU7 "small signal tubes" (whatever that means). If the phono stage uses only 12AX7 tubes, then it's probably not world-class. That doesn't mean it can't be very pleasant sounding. There used to be a circuit board made for the RCA tube manual phono stage using a 12AX7 for each channel. It wasn't bad at all, especially if you added a cathode follower as an output buffer. The 12AX7 type won't work well for all MM cartridges, though, due to its high Miller (input) capacitance. 12AX7 is commonly available, which is a good thing when you need to re-tube. 12AU7 is not a very linear tube, but it is a cheap and plentiful type.

KT120 is a new type of output tube that's based on the KT88 type. I guess there are worse things. The tubes in the picture look a lot like EL34 type, but maybe KT-120 are tall and skinny like that too.

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There was no schematic included with the amp, and I don't see anything on their site for download, but if you contacted the manufacturer, it is possible they might furnish one to you.
 

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It it basically this (KT120) amplifier with a preamp section?

cheers,

AJ
If so, that's pretty interesting. The amp's KT120 output tubes are biased at only 35mA current from each tube, which means they are run in class AB for higher power, rather than deeper into class A (high current/low watts) territory. This demands much more of the driver circuitry and output transformers, and raises the amp's open loop output resistance, which would make the amp require more negative feedback to get low distortion and flat frequency response. It measures well enough at low to mid frequencies. 90W out at 1% THD means there's a lot of power on tap for any smallish listening room. The amp does falter into a 2 ohm load, but even the Emotiva XPA-2 I was just reading about isn't rated to be used into a 2-ohm load (they recommend a minimum 4 ohm load in two-channel operation). The big problem is high distortion at 10kHz and above, at 2% THD into a 4 ohm resistive load (1% THD at 10kHz into an 8 ohm load). The distortion products are almost completely low-order (2nd and 3rd harmonics), so that distortion will likely be pleasant sounding. Still, that's a fair amount of distortion up there.

Anyway, that's what the Stereophile measurements say.
 
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