Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: jukeboxman on January 27, 2018, 09:35:41 am

Title: 5u4 ps question
Post by: jukeboxman on January 27, 2018, 09:35:41 am

Hi guys --I Have what to most of you will seem  like a dumb question --
on a 5u4 power supply --can i pull my plate supply from the input side of my choke and just let the choke feed the screens and preamp tubes?
i am concerned that my choke may be a little light to run the entire amp
thanks Gary

Title: Re: 5u4 ps question
Post by: sluckey on January 27, 2018, 10:09:15 am

Yes, but...

Most push pull amps do supply the plates prior to the choke. And that's fine because the common mode rejection nature of the push pull circuit cancels power supply ripple (hum).

Single ended amps do not cancel power supply ripple (hum). So a SE amp will have less power supply hum if the plate is supplied ***AFTER*** the choke, due to the improved power supply filtering.

Title: Re: 5u4 ps question
Post by: jukeboxman on January 27, 2018, 10:18:19 am

thank you it will be 6l6 pp -i was sure i could but getting old sucks --mind goes to sleep --lol

Title: Re: 5u4 ps question
Post by: 66Strat on January 27, 2018, 01:20:35 pm

The 200 ma. current rating of the choke that you have is sufficient to implement before the plate supply. The 5E7 Bandmaster, 5E5 Pro, and 5E6 Bassman implemented the choke before the plate supply. IMO, that power supply iteration is a significant part of the sound of that era tweed circuit.

I built an amp many years back using the carcass of an old jukebox amp and it implemented the choke before the plates; 5879 preamp into 6SL7 paraphase PI, into cathode biased pp 6L6 UL outputs, into a vintage Jensen P15N. That amp was a tone monster.

Title: Re: 5u4 ps question
Post by: jukeboxman on January 27, 2018, 03:31:39 pm

Thank you however my actual choke is only 125ma   -not building for max watts  just a bench amp -building for pleasure