811A amp Class A2

[MartinV56]

My new project, 6AK5, VT-25, 811A Single Ended Class A2 amp

Advanced project, chassis perforated, tomorrow painting

 

[astouffer]

Looking pretty good so far Are you running the 6AK5 triode strapped?

 

[MartinV56]

Thanks, No, as pentode is similar to WE717A

 

[tube-lover]

hi,

I also prepare to DIY one 811 SE tube amp.

several friends use this circuit was test stable & sound quite good when drive Yamaha NS-1000 ebony.

pls try study this circuit.

any comment.

thx

thomas

 

[MartinV56]

Thanks, the circuit with my modifications, diodes rectifier and 6AK5 very close WE717A

 

[MartinV56]

Hi, Tube lover, thanks again, Yamaha NS-1000 ebony?, 811A in this schematic, only 10 watts, ideal for my Altec Lansing 97 db, sorry my bad english

 

[tube-lover]

hi MartinV56 ,

at first l also think cann drive or said good control of NS1000 because long time ago I was NS2000 user. NS2000 was very hard to drive!

But when my friend told me that his NS1000 stardard version & FX-1 can very easy to push.

Use 300B SE also can use. But use interstage couple will better bass.


Then I order one pair of Ebony & try to use 300B. yes, it cannot full control for classic music. But for room music & jazz, ( not heavy Jazz) it can do well. I will try 811SE & 211SE. I will continous report to share experience.

this one was very easy to drive/

Yamaha FX-1

http://page.freett.com/knisi/fx-1.html


thx

thomas

An externally hosted image should be here but it was not working when we last tested it.

 

[316a]

The output transformer secondary could go in the cathode circuit of the 811A and the loop feedback could be reduced . On the VT25 'dynamic coupled' driver there is no way of selecting the required bias on the 811A which may need attending to . See schematic , this amp uses a tertiary winding on the transformer to offset anode current against filament current which may be confusing , so ignore the coil marked '55t' . It also uses filament bias for the input valve which may be unfamiliar to some .

cheers

316A

 

[MartinV56]

Thank 316, I will consider that change and its benefits

 

[316a]

Thank 316, I will consider that change and its benefits

It's easy to try the cathode feedback and see if it's to your liking . A2 amps can be made to sound good but do need a lot of work , so far I've barely just scratched the surface . Good luck with your project

cheers

316A