Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: dunner84 on October 22, 2015, 11:05:51 pm

Title: 1 channel Vibrolux no Trem
Post by: dunner84 on October 22, 2015, 11:05:51 pm

Hello,

So I finally have everything I need to build this amp, and I have begun planning it out. I am using the layout posted on the Hoffman site for the 1 channel ab763 circuit. http://el34world.com/Hoffman/files/Hoffman_AB763_1.pdf (http://el34world.com/Hoffman/files/Hoffman_AB763_1.pdf)

However I am removing the tremolo... boo hiss... It is just a feature that I can live without.

I have started a rough draft of the layout without the tremolo circuit included. I was hoping someone could take a look over the layout where I removed the trem, and make sure I didn't miss anything. I did this up on my lunch break today, so hopefully a fresh set of eyes can proof it for me. It's a bit sloppy, but it's a rough draft. At this point, I am just concerned about the trem section being removed properly. I drew a dotted red line in-between v3 and v5 where the trem section was.

Also, I am using a PT without a 50v bias tap. I am hoping to implement the suggested circuit on this page: https://robrobinette.com/5e3_Modific...djustable_Bias (https://robrobinette.com/5e3_Modific...djustable_Bias)

Any suggestions on how to modify the bias portion to use the HV tap and not a 50v one?

I will most likely be modifying the Mid to be a RAW control, and I will also be adding more control for the verb, but I think I can manage all that on my own.

I will post pics when I am all done. The cabinet is made, the chassis is bent up and mostly drilled, and the components are all here. I will be working out of town for the next 6 weeks, so I have a lot of time to plan and populate the board. The rest will be finished when I get back which is hopefully in time for christmas.

Thanks for the help.

Title: Re: 1 channel Vibrolux no Trem
Post by: sluckey on October 22, 2015, 11:19:42 pm

Quote

Any suggestions on how to modify the bias portion to use the HV tap and not a 50v one?

Looking at Hoffman's layout... The box that says "Bias Tap"... Change to say "HV Tap". Replace the 470Ω/3W bias range resistor with a 100K/3W resistor.

That's all.

Title: Re: 1 channel Vibrolux no Trem
Post by: dunner84 on October 23, 2015, 12:06:44 am

Fantastic, thank you! Much easier than I thought it would be.

Title: Re: 1 channel Vibrolux no Trem
Post by: uki on October 30, 2015, 10:03:02 pm

Quote

ab763 circuit. http://el34world.com/Hoffman/files/Hoffman_AB763_1.pdf (http://el34world.com/Hoffman/files/Hoffman_AB763_1.pdf)

Sorry for hijacking the thread, I've been trying to find the list of files like the one above, no go  :dontknow:, could someone point me the way please and thanks.

Title: Re: 1 channel Vibrolux no Trem
Post by: Willabe on October 30, 2015, 10:13:39 pm

Their in our host Doug's 'Tube Library of information.' Link can be found at the very bottom of any page in the forum.

http://el34world.com/schematics.htm (http://el34world.com/schematics.htm)

Title: Re: 1 channel Vibrolux no Trem
Post by: uki on October 31, 2015, 10:21:28 am

THANKS !!! Those are really helpfull, and good learning platform.