Bottlehead Forum

Bottlehead Kits => Legacy Kit Products => Stereomour => Topic started by: Jim R. on June 09, 2010, 01:54:36 PM

Title: While we're waiting...
Post by: Jim R. on June 09, 2010, 01:54:36 PM

Can I ask a few questions?

Will the pt be the same core size as the other BH transformers except with a taller a la paramount, lamination stack, or a bigger core size?

How thick will the top plate be?

How about the OPTs and plate chokes -- roughly the same size as s.e.x, or smaller or larger?

Anything else you can tell us that hasn't been covered?

Thanks,

Jim

Title: Re: While we're waiting...
Post by: Paul Joppa on June 09, 2010, 02:48:43 PM

The power transformer is bigger.  Laminations are 3.125 by 3.75 inches, stack is about 1.75 inches high. I tried to get away with the standard 2.5 by 3 inch laminations, but it just didn't pencil out without running the iron harder than I wanted to do.

Hopefully Doc B will quote the plate thickness; last I heard he had not confirmed what was available from the laser cutter. It will be at least 0.100 inch; possibly 0.125 inch.

OPTs and plate chokes are halfway between the SEX and Paramount parts, i.e. the same size as the Paramour plate choke.

Title: Re: While we're waiting...
Post by: Jim R. on June 10, 2010, 03:49:27 AM

Thanks, Paul.  Sounds like this will be a chunky little amp.  I've got a nice 12" x 24" sheet of .125 eutectic copper plate should I want to get carried away. :-)

-- Jim

Title: Re: While we're waiting...
Post by: Jim R. on June 22, 2010, 10:15:35 AM

Another question: are the OPTs autoformers or the more usual type with separate windings?

Thanks,

Jim

Title: Re: While we're waiting...
Post by: Paul Joppa on June 22, 2010, 10:27:27 AM

Quote from: jrebman on June 22, 2010, 10:15:35 AM

Another question: are the OPTs autoformers or the more usual type with separate windings?

The OPTs are conventional. That's one reason I wanted new transformers - they can be rated to have a large DC voltage difference between primary and secondary. This allows the primary to be returned to the cathode of the output tube without requiring separate power supplies for each channel; eventually I hope to take advantage of that to get a new power transformer which we will be able to sell on its own. All of these things are potentially slight cost reductions.

The OPT can be wired for 2, 4, 8, or 16 ohms when used in the Stereomour; it will eventually be used in the SEX amp as well where it will do 4, 8, 16, or 32 ohm loads. Incidentally, if anyone needs switchable output impedances, the most practical scheme requires two DPDT switches per transformer. They may have to go on a board below the OPT - haven't tried to make a layout for that yet but I'll eventually want this feature on my own amps!

Title: Re: While we're waiting...
Post by: Jim R. on June 22, 2010, 10:56:14 AM

Thanks Paul.  Welcome back and hope you had a relaxing vacation.

-- Jim