New 300B Amplifier Idea

[Paully]

Grainger and I are planning our latest Bride of Bottlehead idea.  Just in the discussion phase.  I have plate chokes and output transformers left over from my Paramount conversion that are too good to leave around languishing.  The idea is to take those and then buy new soft start driver boards and filament chokes from Bottlehead and replicate the audio chain.  That is still in discussion, so feel free to offer alternatives.  The place we plan on really playing around is in the power supply and we wanted to do a tube rectified power supply.  Anyway, if anyone has any thoughts, schematics, or a direction you would like to point us in, we are wide open.

 

[Frank Mena]

Cool idea!!      What do you want to do......Still keep it parafeed?  Interstage transformer?  Cap coupled ? Direct coupled?  What gain do you want the amp to have?  All DHT amp (DHT driving a DHT)?  Lots of paths to go thru but will be cool to see where you end up.

Cheers
FM

 

[Paully]

When I say we are at the initial stages, I am not kidding!  I am open to suggestions.  I assume we will keep it parafeed as that is what the transformers were designed for, correct?  I wasn't thinking too much in terms of the audio circuit as we were just planning on buying Bottlehead's driver boards (5670) and using those with a 300B.  Although we were also considering a 6SN7, but only because that is easily accomplished.  Tell me what you would do and why given the parts I already have in hand (Paramount output transformers and plate chokes).  Everything besides that is open to discussion.

 

[jrebman]

Sounds cool.  I have no idea if there is enough voltage overhead on the PT to allow for the extra drop of a tube rectifier, and you may need a separate filament transformer for the rectifier as well, but you could always choose a different operating point that may give you more like 6 watts, and if the voltage  drop of the rectifier is an issue, a lower drop rectifier could be used, and if I were building the amp, I'd use an 83 rectifier as they just give a magical sound and as they are essentially a gas rectifier, they seem to have a voltage regulation effect as well, though I have no measurements to actually prove that.

And if you wanted to get really fancy, use a small pentode, triode strapped, driving something like a 12b4 and an IT to the 300b.  See the diyhifisupply 300b stereo integrated amp, the Lux, to get an idea of what I'm talking about.

Of course these are all just ideas and without knowing all the various voltages, etc. in the paramount, I have no idea if it will actually be possible or practical.

Good luck and keep us posted,

Jim