Audio Research Classic 150 mono-bloc

[alahemi]

Hi Guy,

Someone can tell me if i can change the 6550 in my ARC Classic 150
and replace with TUNGSOL KT 120?
I ask this question to Audio Research and they tell me (see response)

Alain Grenier
Thank you for contacting Audio Research for your audio needs.
Summary: The CL150 was only designed to handle the 6550's. If you run any higher output tubes you will run a high risk of damaging the unit. Transformers and other parts in the unit are not rated for those tubes. I cannot comment on biasing for non recommended tubes because you will have to use them at your own risk.



Thank you,
I can believe that Someone can help me?
P\S sorry for bad english
Thanks.

Alain

 

[Ketje]

You must count 0.3A extra heater current pro tube.Can your supply handle it ?
And there is a re-adusting of the bias current.Up to it ?
Mona

 

[Eli Duttman]

Someone can tell me if i can change the 6550 in my ARC Classic 150 and replace with TUNGSOL KT 120?

The short answer is no. Additional heater current draw is but 1 of several issues. The grid to ground resistance limit for KT120s is lower than that of the OEM tube. Also, the KT120 is distressingly non-linear. 😡 I've seen the curves.

If retubing is necessary, as opposed to a whim, I suggest you install "reissue" Gold Lion KT88s. Other than getting biasing right, it's plug and play. If, as is frequently the case with ARC equipment, 1 or more power tubes are used as screen grid regulators, the less costly ElectroHarmonix (EH) KT88 is fine, for those sockets.