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Chiming in...

Posted by Legendre (A) on August 13, 2006 at 07:45:02

In Reply to: Re: Humm , Mid bass , and Russian 6sn7s and filaments posted by Satelliteman on August 11, 2006 at 23:13:01:

The leakage RK mentioned is heater-cathode leakage, which is fairly typical in the Russian 6SN7 types. Since the filaments are AC, any leakage will superimpose a 60Hz AC signal onto the cathode, which results in increased hum.

There is no need to join the windings of the large filament toroid to power the driver filaments - you should be able to run two 6SN7 off of each 6.3V secondary, without further issue. This is how it's done in all later M-60.

I would not suggest changing the wiring on the main power / standby switches. You want the driver B+ / B- supplies to be present before you apply power to the output section. The output section negative bias voltage is derived from the HV driver supply, by way of the V4 tube - and this voltage needs to be allowed to stabilize before power is applied to the output. The stock arrangement pretty well guarantees this.

Hope that helps, sounds like you're having fun!

This post is made possible by the generous support of people like you and our sponsors:

Herbie's Audio Lab

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