Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: batty on April 09, 2021, 09:05:25 am

Title: 6G3 modification
Post by: batty on April 09, 2021, 09:05:25 am

Hello,
I am bulding Brownface Deluxe from the TAD kit. https://www.tubeampdoctor.com/en/tad-amp-kit-brownface-20-6g3-style-amp-kit?c=154 This is my third amp from a kit after 5E3 Deluxe and 5F1 Champ. I made my homework and found some interesting mods. My inspiration was Rob Robinette, Down Brownie, Ceriatone, El34world.com, etc. I put all mods I want in these drawing:

(https://www.thegearpage.net/board/index.php?media/6g3_v1xx-png.280275/full)
I love my Voodoo V-Plex, so I change normal channel in the 6G3 to something similar to V-Plex. It's bassicaly Marshall '70 Lead specs. V-Plex has probably NFB with 100kOhm on 4Ohm tap, I'll check it. Why Voodoo uses 22pF caps on V1 bettwen grid and anode. Any clue?

(https://www.thegearpage.net/board/index.php?media/plex02-png.280272/full)

I am not sure with Master Volume wiring, I followed this ducument http://valvestorm.com/sites/default/files/PPIMV Step by Step.pdf


And the last muddiness... I saw two 22nF caps in tremolo circuit instead of 10nF in some bulds (Down Brownie for example). Is there any effect other than trem speed?

Thanks for any advice.

Title: Re: 6G3 modification
Post by: Esquirefreak on May 15, 2021, 10:21:02 am

IME, subbing one of the 10nF caps for a 22nF also adds a bit more depth to the trem.

/Max

Title: Re: 6G3 modification
Post by: d95err on May 15, 2021, 03:57:45 pm

Two potential issues:

1. Safety ground should be wired to a separate dedicated bolt which is not used for any other connections. It should NOT be wired to a transformer bolt! Preferably, the length of the safety ground cable should be such that if the cord is ripped out, hot and neutral is ripped off before safety ground.

2. The wiring of the bias pot means that if the wiper looses contact, you loose the bias voltage and your power tubes will burn. I recommend wiring the pot as a variable resistor to ensure that if wiper contact is lost, it goes to maximum negative bias instead (safe mode).