Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: ShaneCW on August 10, 2021, 11:32:41 am
-
Hello,
I'm putting together a parts list to build a Hoffman 1 Channel Vibrolux from a Hotrod Deluxe donor amp.
I am wondering if parts from the HRD reverb section such as 022707 choke and 4EB3C1B tank can be used to help keep costs down?
Can I put the HRD choke and tank in the ab763 circuit in place of the 022921 choke and 4AB3C1B tank that is called for? Can R33's value stay at 220K? or do I need to change the value to 100K like R35 on the HRD?
Are there other things I need to consider?
Thank you!
-
You can use the choke but not the reverb tank. Stay with 220K.
If using the HRD PT you can't copy the Vibrolux power supply. You'll have to use the HDR power supply.
-
The reverb transformer could be dispensed with, and that tank driven by capacitively coupling to the driver valve’s anode or cathode.
-
If using the HRD PT you can't copy the Vibrolux power supply. You'll have to use the HDR power supply.
Thank you!
With the extra tubes on the vibrolux and lack of specs from fender for the HRD transformer, I decided to replace the transformer installed with a Hammond 290cx. Replacement transformers for the HRD PT had amp ratings that appeared too low for the vibrolux's tube compliment.
This is for a buddy I posted about on another thread trying to figure out what I could use the PT for seeing it was an import. Ultimately he decided the cost of a new transformer was cheaper and more convenient than buying a reverb and trem pedal. I also feel a lot more comfortable with that. The other build I was considering was a Bassman circuit with SS rectification using the stock import PT from the HRD. (I may one day try to use that PT for one of those builds.)
I'm thinking the HRD OT will be ok bc I am still only running 1 12" and 2 6L6's, but I'll double check my readings and do the math at the end of my build before pushing the speaker.
Thank you again for the help!
-
The reverb transformer could be dispensed with, and that tank driven by capacitively coupling to the driver valve’s anode or cathode.
Cool, thank you! I don't trust myself to go that far off script. I think I'm gonna stick more closely to the Hoffman schematic. Awesome suggestion, I'll keep it in the back of my mind.