Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: britmusic on March 12, 2019, 12:32:48 pm

Title: AC-30 Component Layout Question
Post by: britmusic on March 12, 2019, 12:32:48 pm

Hello,

I was wondering if someone can please tell me why on the PDF layout of the AC-30 I see one .1uf at the V1-B. And two 33k resistors coming off the pins 2 and 7 of the V1 tube and function is of each is?  Also I notice that the old version of this layout dose not include these components. I have never seen a .1uf in the Top Boost section of a Vox AC-30. And I am again not sure what the two 33k resistors would accomplish.  [/img][/img][/img]

Title: Re: AC-30 Component Layout Question
Post by: EL34 on March 12, 2019, 12:36:11 pm

Moved, posted in wrong board

Title: Re: AC-30 Component Layout Question
Post by: sluckey on March 12, 2019, 12:42:17 pm

Look at the schematic.

Title: Re: AC-30 Component Layout Question
Post by: tubeswell on March 12, 2019, 01:05:19 pm

The 33k are grid stoppers - there to reduce RF interference


.1uF bypass cap will boost mid-hi freq at v1b

Title: Re: AC-30 Component Layout Question
Post by: pdf64 on March 12, 2019, 02:05:19 pm

The point being that the Hoffman AC30 is a different design to the 60s JMI AC30 https://el34world.com/Hoffman/files/Hoffman_AC30.pdf

Title: Re: AC-30 Component Layout Question
Post by: EL34 on March 12, 2019, 07:25:25 pm

Every one of my board kits on the library page has a link to this document
https://el34world.com/Hoffman/files/CommonHookups.pdf (https://el34world.com/Hoffman/files/CommonHookups.pdf)

Look at the input jacks in the document  above
What happens when you only have one jack per channel as opposed to two jacks?

What is the difference between the two jack layouts in the image below?