Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: waldner on September 01, 2017, 11:16:22 am

Title: MV for my 18 Watt Stout Reverb?
Post by: waldner on September 01, 2017, 11:16:22 am

I added a really simple MV to my Hoffman 5e3 (Rob Robinette ver) and like it.  Would like to do the same kind of thing to my 18 Watt Stout Reverb but don't know enough to figure out how.  I've been searching the forum and can't find anything specific to the Stout. 

Is there a simple and good sounding MV that I can add? 

Thanks!

Title: Re: MV for my 18 Watt Stout Reverb?
Post by: Bwmitc9285 on September 01, 2017, 02:56:26 pm

In between C4 (.022) and C5 (.01) there is a 470k resistor. Swap that out for a 500k pot with the wiper connected to C4.

Title: Re: MV for my 18 Watt Stout Reverb?
Post by: waldner on September 01, 2017, 06:01:23 pm

Thanks Bwmitc9285!  Take a look at my revision of the layout attached.  I don't know how to read a schematic and guessed at how to connect.  Let me know if this is what you are referring to?  Also wasn't sure if the other connection on the MV pot goes to ground or nowhere.   I really appreciate your help.

Title: Re: MV for my 18 Watt Stout Reverb?
Post by: sluckey on September 01, 2017, 06:38:32 pm

That will work. This is a bit more proper...

Connect the left side of the pot to the .022 cap. Connect the middle lug to the .01 cap. Connect the right side to ground. Remove the jumper between the .022 and .01 caps.

Title: Re: MV for my 18 Watt Stout Reverb?
Post by: waldner on September 01, 2017, 07:05:43 pm

Ok.  Like this?

Title: Re: MV for my 18 Watt Stout Reverb?
Post by: DummyLoad on September 02, 2017, 07:44:02 am

yes. that will work. try to keep the wires away from the power rail.

 
--pete

Title: Re: MV for my 18 Watt Stout Reverb?
Post by: waldner on September 03, 2017, 05:00:17 pm

I did the mod and it works nicely.  I didn't have a 500k pot laying around, so I used a 1M.  Seems to work fine?

I'm Curious as to what using the 1M pot instead of the 500k is doing to the sound and function of this MV? Also would love to understand what this simple mod is doing and how it works, if anyone could explain.

Thanks again for the help with this! 

Title: Re: MV for my 18 Watt Stout Reverb?
Post by: sluckey on September 03, 2017, 06:34:45 pm

It works exactly like the other volume control in the stout, but it's just located at a different point in the signal chain. 1M vs. 500K yields about the same results.

Title: Re: MV for my 18 Watt Stout Reverb?
Post by: PRR on September 03, 2017, 07:27:26 pm

> using the 1M pot instead of the 500k is doing

The pot should be some larger than the 100K driving it, smaller than the ~~5Meg of the stage after it.

As Sluckey says.... 500K, 1Meg, 250K, 2Meg, no real difference.