Modifying Weber Mass 100

[Boy Howdy]

Merry Christmas to you and yourn!

I've been putting off doing something about this for far too long. It's New Year's resolution time, so here goes.

I have this Mass 100 attenuator. It has a treble boost switch, a two-position, not the three-position of the schematic. I have to use it at a very low level which makes the bright setting way too bright (but the off position is unusable - too dark/dull). I wonder if I can replace the switch with a pot.

What say you guys?

webermass100-gif.186803 (1200×783) (musiker-board.de)

[xtian]

No, you can't replace the treble boost switch with a pot. You're switching caps in or out of the circuit. But you can certainly tinker with the value of C1/C2 (or whatever is actually present in your MASS).

[Boy Howdy]

What about adding a resistor in series with it?

[Jazz P Bass]

I would check how the treble boost circuit is wired up.
If you only have a 2 position switch what capacitors are in it?
The 3 position switch may be a later model to cure exactly what you are experiencing.
You might want to consider modding yours up to a 3 position and adding another 10uf cap in series.

[Boy Howdy]

OR add another cap in series???

I haven't been inside the thing for years. It has weird screws. I think I have the right tools to get into it now. It'll be a couple days before I can get to it.

[Enzo]

Or just add the series cap to the existing boost setting to tame it.

[Helmholtz]

The Weber Mass Lite uses a 50R/100W pot for Mids-Highs adjustment:
https://www.freestompboxes.org/membe...erMASSLite.gif

[Boy Howdy]

Not sure what you're suggesting. That's the Ohmite thing, I think, that you're talking about. Here's some pics of the innards.
inside weber mass at DuckDuckGo

[Helmholtz]

Not sure what you're suggesting. That's the Ohmite thing, I think, that you're talking about. Here's some pics of the innards.
inside weber mass at DuckDuckGo

Yes, Ohmite is a manufacturer of power pots.
The Weber Mass Lite uses 2 of them, see schematic.

[Boy Howdy]

I can't put two of them in there though, wouldn't fit. There kinda expensive too.

I can't understand why a resistor (flameproof?) wouldn't work in series with the cap.

[Helmholtz]

I can't put two of them in there though, wouldn't fit. There kinda expensive too.

I can't understand why a resistor (flameproof?) wouldn't work in series with the cap.

Sure, you could experiment with increasing the value of R7, but it seems you need to use 50W rated resistors.

[Boy Howdy]

Now we're gettin' somewhere. I'm just looking at the schematic and the innards pic and the mouser catalog - looks like it's not your standard resistor. Something unfamiliar. Have to look into it

What about putting a regular resistor in parallel with the existing resistor? Going bigger would mean less bright, I would think?

[Helmholtz]

What about putting a regular resistor in parallel with the existing resistor? Going bigger would mean less bright, I would think?

You can't use regular low power resistors here because it's speaker power level.
Higher resistance lowers treble boost.
You can wire resistors in series to increase resistance.

[Boy Howdy]

Duh, I was thinking caps not resistor. My mistake.

So then, no easy way out. Hmm.

[Boy Howdy]

Well, I'll be. . . .

I opened it up this morning. This version is pretty different from the schematic I posted. I haven't as yet found one for this older model. It has a 2mF treble boost cap.

x911oieq0bboym2hxnfk.jpg (620×465) (reverb.com)