Bottlehead Forum

Bottlehead Kits => Legacy Kit Products => Paramount => Topic started by: John Roman on September 11, 2011, 06:54:20 AM

Title: Paramount 2A3 converted to 45?
Post by: John Roman on September 11, 2011, 06:54:20 AM

How difficult would it be to convert a Paramount 2A3 to a 45? Possible? Just want to hear a 45 in my system.

Title: Re: Paramount 2A3 converted to 45?
Post by: Paully on September 11, 2011, 12:37:39 PM

I am not in a place to give a long reply.  Go search the old forum.  I asked about this and got some responses.  you have to put in another tube for regulation as the 76 is not a dual triode like the 12at7 or 5670.  But go search the old forum for 76 and Paramount.

Title: Re: Paramount 2A3 converted to 45?
Post by: Grainger49 on September 11, 2011, 01:22:04 PM

Paul didn't read it closely.  The 45 conversion, you can find his questions here on this forum about it, requires only a change in the cathode resistor to be most effective.  I don't really remember it well but I think that is all it takes.

Look at these links:

http://www.bottlehead.com/smf/index.php/topic,920.0.html

http://www.bottlehead.com/smf/index.php/topic,1760.0.html

Title: Re: Paramount 2A3 converted to 45?
Post by: AudioDave on September 11, 2011, 01:23:23 PM

Per previous posts from Paul Joppa in the archives it is simply a matter of changing out a resister in each amp.  I am going to try it myself!
Dave

Title: Re: Paramount 2A3 converted to 45?
Post by: saildoctor on September 12, 2011, 08:19:40 PM

I converted my Paramounts from 300b's to 45's this past spring - I'm very happy with having done so!  They still drive my speakers easily in the 12ft/15ft room in which they reside.  They have 8" Fostex FE207e (95db) and T90a supertweets (106db).  

The cathode power resistors need to be changed to provide 6kohms for a 45.  I just wanted to point out that rather than buying two 3k resistors per monoblock to replace the ones currently installed you can also just get one 4k per and put them in series with one existing 2k.  That's what I did with mine.  But you probably already knew that.  :)  I also have the soft start boards and they allowed me to bias using the same method as 2a3's.

Title: Re: Paramount 2A3 converted to 45?
Post by: Paully on September 13, 2011, 03:40:15 AM

Sorry I wasn't paying attention.  It happens.  But for the 45, I ended up being above 6K for the cathode resistor to get the operation points where I wanted them.  I just strung an additional 680 ohm resistor (IIRC) between the tow 3K.

Title: Re: Paramount 2A3 converted to 45?
Post by: Paul Joppa on September 13, 2011, 09:00:05 AM

I just ran some analyses and was able to confirm that the soft-start board with adjustable driver bias provides near-optimal operation of the 45 when adjusted as described in the Paramount 2 manual and the soft-start upgrade manual.