6b4g tubes

[pred]

hello all,

Do somebody know if the Stereomour can be used with 6b4g tubes. It is similar to 2A3, different base and heater voltage? I have some stock of these, and it would be great not to start looking for 2A3s that are much more expensive NOS...

Regards,
Pred

 

[galyons]

Basically the 6B4G is a 2A3 with a 6V filament and an octal base. Electrically (in terms of gain, transconductance, plate resistance) they are essentially the same, but you need to change the filament voltage and sockets. 

Cheers,
Geary

 

[pred]

Hello,

thank you for the answer. I knew that but, reading some more posts I think that the heater on Stereomour is AC, so this means there is no wiring for the 6.3V 6b4g. Pitty...

Best regards,
Pred

 

[Paul Birkeland]

Theoretically, you could add a pair of 6.3V transformers under the hood, though you increase your chances of hum front magnetic coupling with extra iron.

IIRC, the Paramount with very minor modifications could run 6B4G's easily (just ask PJ about adding a cap to the DC supply to bump it up from 5 to 6V).

-PB

 

[Paul Joppa]

The problem with 6B4Gs is that they hum a lot more (about 8dB more) with AC filament power, such as is used in the Stereomour and its predecessors.

They should nominally work in the BeePre though. I think Xavier is the only person to try it so far.

The added cap in the Paramount makes closer to 7.5v, so some further adjustment would be needed.

 

[Paul Birkeland]

The added cap in the Paramount makes closer to 7.5v, so some further adjustment would be needed.

Is this at the output of the diode bridge, or at the output of the FC-1?

-PB

 

[Paul Joppa]

The added cap in the Paramount makes closer to 7.5v, so some further adjustment would be needed.

Is this at the output of the diode bridge, or at the output of the FC-1?

-PB

It's the difference between cap-input and choke-input filters.

 

[pred]

Hello Paul,

thank you for the answer. I imagined you heat the 2A3 with 2.5V AC, so I did not understand where the 7.5V comes trough. If there is an AC voltage I could make a regulator my self and heat the tubes in the amp by a DC. Can you further explain please?

 

[chard]

Hello Paul,

thank you for the answer. I imagined you heat the 2A3 with 2.5V AC, so I did not understand where the 7.5V comes trough. If there is an AC voltage I could make a regulator my self and heat the tubes in the amp by a DC. Can you further explain please?

They were discussing the Paramount which has 5v heaters not the Stereomour which as you note has 2.5v heaters. A lot of modern electronic devises are run on 6vdc, so 6vdc plug in power supplies are readily available. These power supplies are fairly inexpensive. I am not sure how well filtered these power supplies tend to be. You would need two 6vdc 1.2A plug in power supplies to run 6b4g's in the Stereomour. If they don't need to be filtered it would only take to two input connectors to implement this mod.

  This is just an idea. More experienced forum members will have a better idea if this will work or not.

 

[pred]

Hello Chard,

you are reading my mind  8). After the answers that was what I started to think about... Since on the pictures it seems cramped I think the best way would be to do it with the external box... If I decide to go for it I will send some pictures. Anyway my S.E.X. is pretty fine with my Hawthorhnes SSI 15" on Pure Audio Project baffle.  ;D

Best regards,
Pred

 

[chard]

Hello Chard,

you are reading my mind  8). After the answers that was what I started to think about... Since on the pictures it seems cramped I think the best way would be to do it with the external box... If I decide to go for it I will send some pictures. Anyway my S.E.X. is pretty fine with my Hawthorhnes SSI 15" on Pure Audio Project baffle.  ;D

Best regards,
Pred

I will be interested to know how this approach works.