What 2A3 for My Amps?

[BNAL]

Currently I’m running Shuguang 2A3Cs, but have been thinking about getting new tubes for my Paramounts. I have been sifting through the forum on what people think about the different offerings out there and have narrowed it down to a couple of options, but wanted to get some input before I pull the trigger.
 
Based on what I have read the JJ 2A3-40s and Full Music 2A3 mesh plate globe are at the top at my list. I would consider the EML 2A3-S, but I just don’t think that I want to invest that much into tubes at this time.

[Hank Murrow]

My Bottlehead Customs 2A3 amp used National Union tubes initially, but I rolled the JJ 2A3-40 tube into the amp and the differences were not subtle. Search for my posts (Hank Murrow) in the Gallery section of the Forum to see pics and detailed listening notes. I have had these tubes in the system for a couple of years and love them. Eurotubes in Portland, OR was the supplier, and they offer the best warranty.

Cheers, Hank

[BNAL]

Hank,

Thanks. I'm about to pull the trigger on them. From what I have read they are a good deal for the performance.

Brad

[ike]

I have the JJs on my Paramounts for the past several years.  They are great!  I had Valve Art, Sovtek and Electro-Harmonix Gold in the past.  The JJs are in different league in comparison to them.  I would buy them again.

[BNAL]

Thanks for the responses. I pulled the trigger and the JJs are on their way.

[STURMJ]

Just so we all understand... The 2a3-40 is wired as a 2a3 but you keep the heaters wired as you would for the 300b?

[Paul Joppa]

The 2A3-40 is a 2A3 - wire the heaters for 2.5 volts. Since it can take a lot more power than a NOS 2A3, you can wire the rest of the circuit either direct-coupled 2A3 or cap-coupled 300B.

[STURMJ]

got it!

[marantzfan]

The 2A3-40 is a 2A3 - wire the heaters for 2.5 volts. Since it can take a lot more power than a NOS 2A3, you can wire the rest of the circuit either direct-coupled 2A3 or cap-coupled 300B.

Digging up an old thread here, but in order to accomplish this.  Which steps should omitted from the 300b to 2a3 conversion guide that has been published?

[Paul Birkeland]

Digging up an old thread here, but in order to accomplish this.  Which steps should omitted from the 300b to 2a3 conversion guide that has been published?

Go back to the Paramount manual and look at the wiring of the FC-1 and how it connects to the power supply PC board.  Those are the changes that you should make to convert the heater to 2.5V.

[marantzfan]

Ok.  I just got done rewiring the FC-1 and chaged the black wire from the 5v to 2.5v solder pad on each amplifier. 

Is there anything else i need to address, other than adjusting the hum pots for the new JJ 2A3-40 tubes? 

[Jcris]

Marantzfan,
Check these pages in the manual:
pg23  filament supply board
31      filament choke
46      cathode resisters
49      output stage grid
Regards,
Jcris

[marantzfan]

Marantzfan,
Check these pages in the manual:
pg23  filament supply board
31      filament choke
46      cathode resisters
49      output stage grid
Regards,
Jcris

Thank you for digging that up for me, but that isn't exactly what I was asking.

I was going by this guide, which is basically the same information just simplified and all in one place:

http://bottlehead.com/paramount-300b-to-paramount-2a3-conversion/

I know that following ALL of the steps will convert the amplifiers to 2A3, my question is in regards to optimizing the Paramounts for the JJ 2A3-40 as described above (changing the filaments voltage to 2.5v and leaving the rest as cap coupled 300b).

From what I have gathered, it seems like following steps 1 and 2 from the guide I linked, will accomplish what PJ and PB have described above.  Is that correct, or is there anything else that needs to be done that I am missing?

[Doc B.]

Yes, in theory all you need to do is change the filament supply since a 2A3-40 is pretty much a 300B with a 2.5V filament.

[marantzfan]

Thank you Dan. 

I just wanted to confirm, as after doing that I popped in the JJ's and while trying to adjust the hum pots, I noticed that one amplifier was fluctuations from 0 to 12 mv, constantly without moving the pot.

I decided to give them a listen at low volume and noticed an intermittent crackling sound from the side that was givin me the odd readings, but I could certainly hear music over it.

I powered everything down, swapped the tubes and noticed that the crackling sound (and readings) followed the tube.

So what does this sound like?  Bad output tube?  Nothing else has changed.