McIntosh 2301 Tube Amps

[Drglenn]

Hi Audio Kharma and McIntosh Forum,

I am new to Audio Kharma. I am hoping someone on the Forum actually owns a pair of the McIntosh 2301 Tube Amps.

I had the privilege of hearing them recently at the Las Vegas CES 2014 and was extremely impressed, to say the least. I was curious and even concerned about how one biases the 8 Output Tubes for each Mono-Block. I contacted the Technical Department at McIntosh to find out how one does that as even the Downloadable Owner's Manual has no information on how to bias the tubes. Even the Tech Guy I spoke with was somewhat vague. If sounded like there is no Auto-Bias and one has to flip these 120# heavy duty amps upside down, keep them on, put a Voltmeter and somehow bias the tubes.

I am hoping there is someone out on the forum that owns the McIntosh 2301 Tube Amps who has actually gone through the process and give a brief and clear instructions on how this is to be done. I am interested in a potential future purchase, but I want to know what I am getting into. ;-)

Thank You in Advance for any advice the forum can provide!!

Dr. Glenn

 

[kevzep]

Welcome to AK and the McIntosh forum....:thmbsp:

Why are you "concerned" about setting the bias on these amps?
I assume you'll buy them new?

In all the talk I have read, with owners talking about them and changing tubes etc etc, I have never heard anyone talking about having to set the bias...

I assume they are either fixed bias, or auto bias, something like that.....

If fiddling with the bias was so important to the day to day use of these amps then it would be in the manual....and easily accessible to the user.
I read the manual cover to cover and it never mentions anything about it....

Purchase and enjoy.....
If there is a problem then you'll take them into your local McIntosh service center.... I don't see the problem...
The MC2301 have a pretty extensive protection system with them, if tube fails then the amp will shut down so you don't fry plate resistors and the likes....

I am a tech and I know about tube amps, I collect and repair/restore tube Marshall guitar amps, so I am used to working with tubes...

Apparently they are extremely nice sounding amps, good luck with your quest...

 

[joeinid]

Kev is right. I think the MC2301's are fixed bias and the bias pots on the bottom of the amp are only for technicians in case there is something in the circuit that needs correcting. I have friends who've owned the 2301's and they are easy to run and essentially plug and play. There is protection built in for tube failures. Just keep some spare tubes around and preferably buy them matched. There are no user adjustable bias settings.

 

[W9TR]

Dr. Glenn,
I have owned a pair of MC2301's since 2009. They are the most carefree tube amps you can own. You do not need to reset bias when replacing tubes. They are auto-bias. I've got the service manual and I can give you the technical details if you'd like.

They also have McIntosh's "Sentry Monitor" circuitry, which shuts the amp down if a tube fails. It works perfectly, no drama. I've had three tube failures, and there has been no collateral damage whatsoever. I've got over 10,000 hours on the amps. I tested the outputs a month ago and they are all still fine. I did replace the driver tubes at 8000 hours. Very economical, easy on tubes.

Tom

 

[chuckworkb]

Easy Peezy, plug in the tubes, and turn it on.
No bias adjustments, especially not lifting the amp on it's side. Perhaps if a technician wanted to check what the bias voltage was on the tubes as part of some troubleshooting process they might have to take the cover off and flip it over, but not the user.