Stereomour vs Stereomour II

[reglys]

Hi

What is the difference between Stereomour I and Stereomour II?
 Is it possible to update Stereomour I to Stereomour II?
 Is it easy to update Stereomour 45 to 2A3 ?

[Paul Joppa]

Stereomour II can be more extensively upgraded - that was the main point of the redesign. It has one more tube socket and one more control (L-R balance), permitting the driver shunt regulator and stepped volume control packages to be installed.  I don't have my notes at hand, and I don't recall whether the DC filament upgrade can be installed in Stereomour.

It should be easy to switch from 45s back to 2A3s as originally made. I believe the current source plate load is still available, if not already installed.

The basic circuit of both is nearly identical. I slightly increased the driver plate current and simplified the driver bias method; this change should be fairly easy to make.

[Paul Birkeland]

What is the difference between Stereomour I and Stereomour II?

Along with what PJ wrote, the Stereomour II has a very different power transformer with universal primary windings and a slight bump in the filament winding voltage for the 2A3s to allow for adding DC heaters as an upgrade.

Is it possible to update Stereomour I to Stereomour II?

Kind of, but not really.  The Stereomour I uses a PC board for the power supply, so if you put the Stereomour II power transformer into a Stereomour I, there would be no place to put the DC filament upgrade if you wanted to add that.  There aren't enough socket holes to add a tube for the driver power supply shunt regulator upgrade, and the attenuator upgrade isn't really made to fit in there either.  The layout of the Stereomour I also isn't setup for the dropping resistors needed for the Stereomour II power transformer, and doesn't have places to land the incoming wall AC power feed to distribute to the universal primaries.  You also wouldn't really get anything in the way of an upgrade from just changing the power transformer, other than being able to rewire it to use in different countries with different mains voltages.

Is it easy to update Stereomour 45 to 2A3 ?

The Stereomour I is very easy to alter for #45 operation, the Stereomour II needs a few extra steps.

[reglys]

Thank you sir for your replies. If I understand well, the stereomour I  was not design to accept the DC filament upgrade.

[Paul Joppa]

Thank you sir for your replies. If I understand well, the stereomour I  was not design to accept the DC filament upgrade.

Yes , that's the case. Well, technically, the DC filament kit was not designed to work with Stereomour I. In fact the desire for DC filaments, the driver shunt regulator, and the stepped volume options are the main reasons for developing the Stereomour II. The basic circuit goes back to the original Paramour, introduced in 2000. The output transformers and plate chokes were developed for Stereomour I, which is probably the biggest sonic improvement in the lineage.