Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: clyde on November 10, 2023, 11:18:16 am

Title: Mixing parallel triodes
Post by: clyde on November 10, 2023, 11:18:16 am
I will be using a 12AX7 with dissimilar cathode circuits and dissimilar coupling caps for each triode, a separate 100k plate resistor for each and will combine the outputs.  Are series (mixing) resistors needed after the coupling caps?  One triode will be switched out to be used in a cascaded stage which is why I need dissimilar circuits.  Thank you.
Title: Re: Mixing parallel triodes
Post by: kagliostro on November 10, 2023, 11:36:53 am
In the VOX AC30CC2 they do it this way, joined inputs (and have joined cathodes) but I think you can go also with separated cathodes

(https://i.imgur.com/C2pTePE.jpg)

(https://i.imgur.com/XS4BDau.jpg)

Franco
Title: Re: Mixing parallel triodes
Post by: clyde on November 10, 2023, 12:37:15 pm
Thank you, not quite, I'll only have one volume for the combined outputs. There won't be a "normal" channel.   
Title: Re: Mixing parallel triodes
Post by: sluckey on November 10, 2023, 01:03:40 pm
I will be using a 12AX7 with dissimilar cathode circuits and dissimilar coupling caps for each triode, a separate 100k plate resistor for each and will combine the outputs.  Are series (mixing) resistors needed after the coupling caps?  One triode will be switched out to be used in a cascaded stage which is why I need dissimilar circuits.  Thank you.
Probably a good idea to use mixing resistors. Might make more sense if we could see an actual schematic.
Title: Re: Mixing parallel triodes
Post by: clyde on November 10, 2023, 03:05:50 pm
(https://el34world.com/Forum/blob:https://el34world.com/68b99092-a47e-47b8-9fa8-25a0aaae0834)
Title: Re: Mixing parallel triodes
Post by: kagliostro on November 10, 2023, 03:18:05 pm
Ciao Clyde

Revise your schematic, seems that as is it won't work

Franco
Title: Re: Mixing parallel triodes
Post by: stratomaster on November 10, 2023, 03:45:37 pm
(https://el34world.com/Forum/blob:https://el34world.com/68b99092-a47e-47b8-9fa8-25a0aaae0834)

This will block DC from reaching the anode.
Title: Re: Mixing parallel triodes
Post by: clyde on November 10, 2023, 06:08:02 pm
Sorry, I was in a rush to get out the door at the moment.  Let's try this:



Title: Re: Mixing parallel triodes
Post by: PRR on November 10, 2023, 07:50:20 pm
.