Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: cusebassman on July 01, 2020, 03:29:37 pm

Title: Rob Robinette Bassman Micro FX Loop
Post by: cusebassman on July 01, 2020, 03:29:37 pm

Hey all! I'm currently planning a Bassman Micro build (https://robrobinette.com/Bassman_Micro.htm), and I've got a question about the FX loop. Rob states that:

"The Master Volume acts as the FX 'send volume' so you can feed your true 5F6A Bassman preamp into a PA or soundboard. You can also tap directly into the power amp by inserting a signal from a modeling preamp such as a POD HD500 directly into the Return jack (guitar > HD500 > Return Jack) but since you are bypassing the preamp and volume controls you must control the amp's volume with the FX or guitar volume."

This makes it sound like the passive FX loop is placed after the Bright Volume, Preamp Master Volume, and the EQ. But in the wiring diagram, it seems as though the FX loop is placed immediately after the Bright Volume, and before the EQ and Preamp Master Volume. Am I misreading the wiring diagram? Thanks!

Title: Re: Rob Robinette Bassman Micro FX Loop
Post by: SILVERGUN on July 01, 2020, 03:40:31 pm

Is there a schematic you are looking at?

Title: Re: Rob Robinette Bassman Micro FX Loop
Post by: cusebassman on July 01, 2020, 03:50:38 pm

Just the schematic and wiring diagram from Rob's page. The schematic doesn't include a loop whatsoever, but is one version behind the wiring diagram, as indicated in Rob's photos.

(https://robrobinette.com/images/Guitar/Bassman_Micro/Bassman_Micro_LTP_Schematic.png)

(https://robrobinette.com/images/Guitar/Bassman_Micro/Bassman_Micro_LTP_Layout.png)

Title: Re: Rob Robinette Bassman Micro FX Loop
Post by: SILVERGUN on July 01, 2020, 03:58:48 pm

Ok, I see what you see.
That is either a mistake on the layout, or an intentional different location for the effects loop than the way it is worded.

Title: Re: Rob Robinette Bassman Micro FX Loop
Post by: cusebassman on July 01, 2020, 04:04:43 pm

Thanks for confirming! Hopefully Rob or someone else will weigh in with where the appropriate location is. I assume it's immediately after the Preamp Master Volume, but would like confirmation.

Title: Re: Rob Robinette Bassman Micro FX Loop
Post by: SILVERGUN on July 01, 2020, 04:09:56 pm

It "could" go in either location but if you want the full preamp signal then you'll want to put it after the Pre MV as worded and not pictured.

Title: Re: Rob Robinette Bassman Micro FX Loop
Post by: SILVERGUN on July 01, 2020, 04:48:04 pm

Looking over that page a little more, there is this:

Title: Re: Rob Robinette Bassman Micro FX Loop
Post by: cusebassman on July 01, 2020, 05:10:03 pm

Wow, I don't know how I missed that. I'll have to try it in both positions and see which is better. I also wonder if a buffered loop would work well in the original position.