Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: idsnowdog on March 24, 2024, 04:55:39 pm

Title: Matchless TMB tone stack.
Post by: idsnowdog on March 24, 2024, 04:55:39 pm

I am building a Matchless Spitfire clone and I would like to add a TMB tone stack to it.  However, I'm unsure what values it would use or how to wire it.  Is there a tone stack that is similar that I could use?  I see Rob Robinette has a TMB on the pots tone stack but that has values more closely associated with Fender.  Would the Hoffman Stout TMB tone stack be close?  As I understand it the Stout is supposed to be Marshall/Vox type 18 watter.

Title: Re: Matchless TMB tone stack.
Post by: sluckey on March 24, 2024, 05:43:38 pm

Look at this current thread...

https://el34world.com/Forum/index.php?topic=31513.0

Title: Re: Matchless TMB tone stack.
Post by: idsnowdog on April 23, 2024, 05:28:52 pm

Does this look right?  I would come off the middle lug of the volume pot into the middle of the treble pot but where would the red question mark go?  With the Hoffman Stout schematic, it connects to the 100K plate resistor for V1. 

Title: Re: Matchless TMB tone stack.
Post by: AlNewman on April 25, 2024, 01:15:49 am

Are you putting the tone stack 1st, or the volume?  Normally the tone stack has 1 input, and 1 output, same as the volume control.

I'm not sure a TMB tone circuit would work well with only 1 gain stage, you may find it sucks too much signal.

Title: Re: Matchless TMB tone stack.
Post by: sluckey on April 25, 2024, 06:58:54 am

Quote from: idsnowdog on April 23, 2024, 05:28:52 pm

Does this look right?

No. See corrected attachment.

The TMB is a very lossy tonestack. You need another gain stage. You won't be happy with the as-drawn layout.

Title: Re: Matchless TMB tone stack.
Post by: idsnowdog on April 25, 2024, 09:39:29 am

I built the little MOSFET IRF820 circuit from the D'Mars OD Special.  Would this wiring work?

Title: Re: Matchless TMB tone stack.
Post by: sluckey on April 25, 2024, 10:43:16 am

no

Title: Re: Matchless TMB tone stack.
Post by: idsnowdog on April 25, 2024, 02:36:59 pm

I had the Zener and pin orientation wrong.

Title: Re: Matchless TMB tone stack.
Post by: sluckey on April 25, 2024, 05:44:04 pm

Still wired wrong.

Title: Re: Matchless TMB tone stack.
Post by: idsnowdog on April 26, 2024, 03:11:38 pm

How's this?

Title: Re: Matchless TMB tone stack.
Post by: sluckey on April 26, 2024, 04:06:37 pm

Finally it works. But that MOSFET circuit is a source follower and has no gain. You still need an extra gain circuit for that TMB TS.

Title: Re: Matchless TMB tone stack.
Post by: idsnowdog on April 27, 2024, 12:32:28 pm

I read through MOSFET Follies this morning and it looks like I can use another IRF820 as a makeup gain stage if I wire it like a triode.  This is the DIY layout I came up with.  The signal flows out of the red wire into the tone circuit.  Out of the blue wire into the volume pot out of the volume into the coupling capacitor.  I'm not sure if the blue wire would go into the makeup gain stage and then into the volume or if the volume would go out to the makeup stage into the coupling cap?

Title: Re: Matchless TMB tone stack.
Post by: sluckey on April 27, 2024, 12:54:14 pm

V1 has two triodes connected in parallel. I would remove the 3 jumpers between the triodes. This frees up a triode to be used as a gain stage before the MOSFET follower.

Title: Re: Matchless TMB tone stack.
Post by: idsnowdog on April 27, 2024, 02:17:42 pm

The simplest would be to put the tone stack between the two V1 triodes like a Princeton Reverb.  I have things cobbled together right now and transplanting those components to a new board with a new layout would simplify things.