ARC Ref150 upgraded to KT150 bias?

[Pacha]

I've just upgraded my ARC Ref150 amplifier to KT150 tubes from the stock KT120s. The manual states adjust bias to 65mVDC for the KT120 tubes. My question is what should I set the bias to for the new KT150s? Any suggestions greatly appreciated.

 

[Argonaut]

I would recommend staying with 65mVDC

 

[Pacha]

I would recommend staying with 65mVDC

That was my first guess also. Thank you for the reply.

 

[Pacha]

Just heard from ARC, and their answer is the same. Stay with 65mVDC.

 

[bimmerlover]

I've just upgraded my ARC Ref150 amplifier to KT150 tubes from the stock KT120s. The manual states adjust bias to 65mVDC for the KT120 tubes. My question is what should I set the bias to for the new KT150s? Any suggestions greatly appreciated.

Greetings! How did the switch to KT150s go and what difference did it make? Did you also make other mods (like other differences between the 150 and the 150SE model)?

 

[Pacha]

Greetings! How did the switch to KT150s go and what difference did it make? Did you also make other mods (like other differences between the 150 and the 150SE model)?

I made no other changes. Performance difference has been a bit hard to determine as the KT120s that I removed were well broken in and the KT150s were brand new. I did seem to notice a bit tighter bass but, to be really sure I'd have to put the KT120s back in, bias, and then see what I heard since the KT150s are now broken in.

 

[unboxed]

I made no other changes. Performance difference has been a bit hard to determine as the KT120s that I removed were well broken in and the KT150s were brand new. I did seem to notice a bit tighter bass but, to be really sure I'd have to put the KT120s back in, bias, and then see what I heard since the KT150s are now broken in.

I upgraded an ARC REF 75 from KT120s to KT150s and the difference was stunning. Better in all parameters especially the bass and midrange. There is a very good reason why ARC upgraded and tuned their newer models to KT150 tubes. I think you will be very pleased after the tubes are broken in.

 

[bimmerlover]

@unboxed did ARC ever come out officially with a Ref 75 with KT150s (akin to an SE version) so you had reason to believe it would work, or did you just try it anyway and it worked out? At some level I assume it’s not given that popping in bigger tubes will just work, given the circuitry/design around them.

 

[Pacha]

I don't know about the Ref75, but I asked ARC about upgrading my Ref150 from KT120 to KT150 and they encouraged me to do it and even sold me the tubes to do so.

 

[unboxed]

@unboxed did ARC ever come out officially with a Ref 75 with KT150s (akin to an SE version) so you had reason to believe it would work, or did you just try it anyway and it worked out? At some level I assume it’s not given that popping in bigger tubes will just work, given the circuitry/design around them.

I asked ARC before I bought and tried the KT150s. Dave Gordon said it would not be a problem. This was before ARC introduced the REF 75 SE. KT150s were the new kid on the block. Early days. I am fairly certain I let ARC know how much better the 150s were. They were probably already exploring the new tubes.

 

[bimmerlover]

My Ref 150 is still in its shipping box. Perhaps I should plug it in and use it with its KT120s for a while before even thinking about the 150s… LOL

 

[Pacha]

My Ref 150 is still in its shipping box. Perhaps I should plug it in and use it with its KT120s for a while before even thinking about the 150s… LOL
View attachment 138042

You should really get that beauty out of the box and making tunes. Even with the KT120s it is an amazing sounding amp.

 

[bimmerlover]

You should really get that beauty out of the box and making tunes. Even with the KT120s it is an amazing sounding amp.

Yes, I agree. It’s been sitting boxed up on my floor for about a month now. We’re doing some renovations and building new cabinets for the listening lounge and it just hasn’t been enough time, nor the right timing, to break it out. Soon!