Bottlehead Forum

Bottlehead Kits => Legacy Kit Products => Paramount => Topic started by: Jim R. on October 21, 2009, 07:19:05 AM

Title: Can Paramount be built with 45s?
Post by: Jim R. on October 21, 2009, 07:19:05 AM

Just curious if Paramounts can be built with 45s with a change in OPTs, plate chokes, and operating points?

How about shunt regulation for the B+?

Thanks,

Jim

Title: Re: Can Paramount be built with 45s?
Post by: Paul Joppa on October 21, 2009, 01:47:40 PM

Paramount can easily be run with a 45 - just build the 2A3 version but replace the 2K cathode resistors with 3K resistors. They are in series for this direct coupled approach, so the total cathode resistance is 6K for 45s, 4K for 2A3s.

I can't get the numbers to work right for a shunt regulated version - not enough voltage available for direct coupled, and too much voltage for capacitor coupled. And (as posted elsewhere) the voltages work for a 2A3 but the current is too high for designs we have in inventory. I'll continue to work that one but at a low priority.

Title: Re: Can Paramount be built with 45s?
Post by: Jim R. on October 21, 2009, 02:27:48 PM

Thanks very much Paul.  Now I wonder if anybody has done this and what it sounds like :-).

Will the input sensitivity stay pretty close to the same?  The direct coupling is a real bonus too.

Thanks again,

Jim

Title: Re: Can Paramount be built with 45s?
Post by: Paul Folbrecht on March 13, 2010, 09:43:44 AM

I'm considering building a pair for 45.  Anybody who has done this care to share re: the sonics?

I would assume the OPT load is not appropriate but that does not have too big an effect.

Title: Re: Can Paramount be built with 45s?
Post by: Paul Joppa on March 13, 2010, 11:29:42 AM

Quote from: Paul Folbrecht on March 13, 2010, 09:43:44 AM

...
I would assume the OPT load is not appropriate but that does not have too big an effect.

The operating point is adjusted for optimum operation with the Paramount 3K load impedance.

If you do this with Magnequest iron, let me know and we'll get Mike to gap the plate choke for more inductance.

Title: Re: Can Paramount be built with 45s?
Post by: Jim R. on March 13, 2010, 12:47:36 PM

PJ,

If you increased the inductance for use with 45s in the paramount, or used the alternate choke in the stereomour, how would that effect the ability to also play 2a3s?  Aside from the lower power/longer life, willl the higher value plate choke have any negative sonic effects if you built either of these amps to use 45s primarily but with the option of running 2a3s?

-- Jim