Audio Research Announces SE Upgrades for Ref 75/150/250 Amps

microstrip said:
Mark,

We have different views on this matter. I am happy they did not do it. ARC have tens of years of experience in amplifiers using about 420V power supplies (a lower than average value) and managed to create some very reliable amplifiers, something I praise a lot in the brand - I have many thousands of hours in my REF150 without any problem.
As far as I know the upgrades need changing the output transformers to adapt the amplifier to the KT150's, as well as few capacitors and wiring.

From the Audiobeat site:
"Although we could change some of the operating voltages and get higher rated power output," says Dave Gordon of Audio Research, "we are going the conservative route, which we think will provide greater reliability and tube life. We expect owners to get 3000 hours out of these tubes, about 50% longer than KT120-equipped amps."
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So you think they are changing out the output transformers?
 
Francisco-One more thing; ARC has been building 75 watt tube amps for many, many years that used a single pair of 6550 tubes that were very reliable. Now they are using tubes that are capable of dissipating much more plate power safely (60 watts for KT-120, 70 watts for KT-150 tubes vice 42 watts for the 6550) and yet these amps are still rated for 75 watts. Given your logic of reliability, ARC should have run their 6550 tubes more conservatively.
 
mep said:
So you think they are changing out the output transformers?
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I think so. They were very clear about the output transformer of the GS150 - it was a new design to better match the KT150's, they were not just using the REF150 output transformer. But as far as I know no one confirmed or denied it.
 
microstrip said:
I think so. They were very clear about the output transformer of the GS150 - it was a new design to better match the KT150's, they were not just using the REF150 output transformer. But as far as I know no one confirmed or denied it.
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I specifically asked you because I would think ARC would make it quite clear if they were indeed changing the output transformers.
 
mep said:
Francisco-One more thing; ARC has been building 75 watt tube amps for many, many years that used a single pair of 6550 tubes that were very reliable. Now they are using tubes that are capable of dissipating much more plate power safely (60 watts for KT-120, 70 watts for KT-150 tubes vice 42 watts for the 6550) and yet these amps are still rated for 75 watts. Given your logic of reliability, ARC should have run their 6550 tubes more conservatively.
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There are some other tube parameters, related to voltage, that are more critical than plate power for amplifier reliability. In order to increase power the HT voltage and driving voltage would need to be augmented, needing significant changes in the circuit design of the previous non SE amplifiers. We should remember that most of the time tubes break at transient moments - either when turning off or turning on the amplifier. In fact I remember that some Vmax grid specifications of the KT120 were not as high as the old 6550 and some amplifiers needed a few modifications to be used with the KT120.
 
mep said:
I specifically asked you because I would think ARC would make it quite clear if they were indeed changing the output transformers.
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I hope we will soon know about it - ARC only refer to new "active and passive parts" and a transformer is a passive part!
 
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