274B max voltage

[sumotan]

Hi Guys
A little tutorial pls. There's a Chinese made 845 mono block amp for sale at my end. It uses a 274b rectifiers per amp. Question, from data it states max input voltage with cap input is 450v ac or 500v with choke input, so how do one get away with supplying 1000v or so for the 845 using 274B rectifiers ?


Thanks

 

[rayma]

how do one get away with supplying 1000v or so for the 845 using 274B rectifiers ?

Two supplies in series?

 

[sumotan]

Only one rectifier is used per amplifier.

 

[rayma]

Only one rectifier is used per amplifier.

Then they don't get the 1000V. You can't use that common cathode tube as a voltage doubler.

 

[grovergardner]

Only one rectifier is used per amplifier.

Either they use the 274B in a bridge with diodes, or they use it for a separate supply for the inout and driver stages.

 

[rayma]

Either they use the 274B in a bridge with diodes, or they use it for a separate supply
for the inout and driver stages.

Right, I've seen FW bridge rectifiers done with a tube for the positive, and diodes for the negative.

 

[sumotan]

That's the reason why I posted. This amp uses 6sn7 input & 300B driver stage. Looks very well made but can't find any info on the internet. Could the 845 voltage itself be supplied via SS bridge rectifier ?????

 

[sumotan]

Thanks guys , negative done with diodes ??? Is there a schematics that I can refer too ?

Thanks again

 

[grovergardner]

That's the reason why I posted. This amp uses 6sn7 input & 300B driver stage. Looks very well made but can't find any info on the internet. Could the 845 voltage itself be supplied via SS bridge rectifier ?????

Sure. They could have dual secondaries on the power transformer. You don't really want 1000vdc for the inout and driver stage anyway.

 

[sumotan]

Agree Grovergardener just curious that it was spec this way & wonder how it would work.

Thank you again

 

[grovergardner]

Agree Grovergardener just curious that it was spec this way & wonder how it would work.

Thank you again

Do you have a name and model number of the amp?

 

[sumotan]

Brand is LeiMing model RA-845

 

[rayma]

negative done with diodes ??? Is there a schematics that I can refer too ?

The Valve Wizard

 

[grovergardner]

Brand is LeiMing model RA-845

If it's anything like similar amps on eBay, the power transformers have two HV windings. I'm pretty sure they use SS diodes for the 845 plate supply and the 274B for the 300B and input stage.

 

[sumotan]

Thanks guys. Curious how it sounds, the owner upgraded all the tubes to Psvane,