Re: DC offset dial at extreme on M60 MkII.2

Posted by Lew (A) on September 30, 2005 at 07:45:51

In Reply to: DC offset dial at extreme on M60 MkII.2 posted by Zenjabil on September 29, 2005 at 11:36:17:

Why the relationship between the direction of the bias adjustment and the direction of the needle travel are opposite for the two amplifiers is not easy to say, because there are several possibilities but none of them are a major cause for concern.

The fact that you have to turn the bias adjustment to one extreme in order to balance out one amplifier suggests that one or more output tubes on one side of that monoblock are suboptimal with respect to the tubes on the opposite side, i.e., the two groups of tubes are collectively no longer well-matched (hope that's not too opaque, but it's the simplest way to put it that I can think of right now). Try swapping tubes from one side of that monoblock to the other side of the same monoblock. (The M60 has two groups of four output tubes each on opposite sides of the chassis as you face the unit from the front; for example, take any two tubes from one side and swap them with any two tubes on the other side, etc.) Eventually, you should find a configuration that permits easier biasing. Of course also in the process you may find that one or more tubes needs replacement. Why do you not hear a problem? Because the circlotron design is incredibly tolerant of bad output tubes or mismatching of output tubes. However, I bet when you straighten things out, you will notice a tad of improvement in the sound, just a tad.

As to the question of whether you should balance the amplifiers with or without the speakers in the circuit, I think that is spelled out in the owner's manual, and there is a definite preference. (I just cannot remember what Ralph wants you to do.) I personally ALWAYS balance my amplifiers with the speakers in the circuit. Also, contrary to what doc says, I cannot imagine why having your Quads hooked up should make one amplifier act funny and not the other; presumably each speaker in the stereo pair represents a nearly identical load unless one of them is defective. In other words, biasing with the speakers in circuit may give you a different bias point vs biasing with speakers out of the circuit, but the difference should be the same for both channels.

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Follow Ups Full Thread

Topic - DC offset dial at extreme on M60 MkII.2 - Zenjabil 11:36:17 09/29/05 (16)

SUCCESS!! - Zenjabil 11:27:27 10/01/05 (2)

addendum - Lew 07:16:12 10/03/05 (0)

Relax.. - Lew 07:08:50 10/03/05 (0)

Re: DC offset dial at extreme on M60 MkII.2 - Hot TUBE Swapping - Mike Mount 18:52:55 09/30/05 (0)

Re: DC offset dial at extreme on M60 MkII.2 - docs 13:19:21 09/30/05 (0)

Re: DC offset dial at extreme on M60 MkII.2 - bmotorcycle2003 12:49:41 09/30/05 (1)

Re: DC offset dial at extreme on M60 MkII.2 - Zenjabil 14:09:49 09/30/05 (0)

Re: DC offset dial at extreme on M60 MkII.2 - Lew 07:45:51 09/30/05 (2)

Re: DC offset dial at extreme on M60 MkII.2 - acres verde 08:22:43 09/30/05 (0)

Re: DC offset dial at extreme on M60 MkII.2 - Zenjabil 08:01:15 09/30/05 (0)

Re: DC offset dial at extreme on M60 MkII.2 - docs 17:24:50 09/29/05 (3)

Re: DC offset dial at extreme on M60 MkII.2 - Zenjabil 18:44:07 09/29/05 (2)

Re: DC offset dial at extreme on M60 MkII.2 - docs 04:36:28 09/30/05 (1)

Re: DC offset dial at extreme on M60 MkII.2 - Zenjabil 07:59:25 09/30/05 (0)

Re: DC offset dial at extreme on M60 MkII.2 - BAJ 14:17:12 09/29/05 (1)

Re: DC offset dial at extreme on M60 MkII.2 - Zenjabil 18:45:02 09/29/05 (0)

Follow Ups

Re: DC offset dial at extreme on M60 MkII.2 - Lew 07:45:51 09/30/05 (2)

Re: DC offset dial at extreme on M60 MkII.2 - acres verde 08:22:43 09/30/05 (0)

Re: DC offset dial at extreme on M60 MkII.2 - Zenjabil 08:01:15 09/30/05 (0)

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