Big Monk
Well-known member
Thanks to the fact that @Harry Klippton had a unicorn black board VJr PCB in his stash, I'm revamping my amp.
Recently, I implemented a plate driven TMB tonestack and variable negative feedback into what is in essence an EL84 Tweed Champ. The effect was the loss of the filthy tweed overdrive with the volume up but with the benefit of essentially full clean headroom up to almost max on the volume control. This is great for me because I can essentially get more use out of the pedalboard and drive pedals now.
Since I now have a pristine PCB to work off of, I'm looking to implement a few controls straight out of the Early 70s linked input Hiwatt. Since I already have implemented the plate driven tonestack from the Blackface Vibrochamp, I'm going to rework it with the proper values from the Hiwatt stack. Instead of variable NFB on the new build, I'm going to audition and go with a fixed NFB amount and implement the presence control from the Hiwatt as well. Obviously I'm not meaning for this to be Hiwatt like in tone (not possible anyway), but just want to use those circuit snippets as known examples.
Which brings me to my question. I just want a peer check from the collective to confirm whether I'm adapting this correctly. Since I am utilizing the single dual triode from the VJr, my insertion point is the V1b cathode connection which i'll gain access to by removing the cathode bypass cap in that stage:
Here is the Hiwatt implementation:
I have configured the NFB and Presence circuit like this and am wondering if I can get some insight as to whether this is correct:
Recently, I implemented a plate driven TMB tonestack and variable negative feedback into what is in essence an EL84 Tweed Champ. The effect was the loss of the filthy tweed overdrive with the volume up but with the benefit of essentially full clean headroom up to almost max on the volume control. This is great for me because I can essentially get more use out of the pedalboard and drive pedals now.
Since I now have a pristine PCB to work off of, I'm looking to implement a few controls straight out of the Early 70s linked input Hiwatt. Since I already have implemented the plate driven tonestack from the Blackface Vibrochamp, I'm going to rework it with the proper values from the Hiwatt stack. Instead of variable NFB on the new build, I'm going to audition and go with a fixed NFB amount and implement the presence control from the Hiwatt as well. Obviously I'm not meaning for this to be Hiwatt like in tone (not possible anyway), but just want to use those circuit snippets as known examples.
Which brings me to my question. I just want a peer check from the collective to confirm whether I'm adapting this correctly. Since I am utilizing the single dual triode from the VJr, my insertion point is the V1b cathode connection which i'll gain access to by removing the cathode bypass cap in that stage:
Here is the Hiwatt implementation:
I have configured the NFB and Presence circuit like this and am wondering if I can get some insight as to whether this is correct:
