Modifying Weber Mass 100

[Helmholtz]

It has a 2mF treble boost cap.

I guess you mean µF (= micro-Farad) not mF (= milli-Farad), the difference is a factor of 1000.

A larger cap like 10µF will add midrange.
You need an NP cap meaning non-polarized aka bipolar cap.
Voltage rating like the original one, probably 50V.

[Chuck H]

Well the tone stack for the line out on the first schematic posted uses a 2n2 treble cap. Neither the treble boost for the speaker signal or the treble cap for the line out tone stack are 2mf, but could this be where the error is?

[Boy Howdy]

Only problem is that it's not so much the frequency of the boost that I have a problem with as it's the amplitude of that frequency.

I haven't had time to study up on what's involved with changing out those big ceramic resistors and I'm actually not sure I want to go to all that trouble - it could turn out to be no improvement at all - but I've contacted Weber about getting a schematic, so we'll see how that goes and take it from there, I guess.

[Chuck H]

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

There are no pics of your innards here. They are pics of other, significantly different models.

[Chuck H]

Only problem is that it's not so much the frequency of the boost that I have a problem with as it's the amplitude of that frequency.

I haven't had time to study up on what's involved with changing out those big ceramic resistors and I'm actually not sure I want to go to all that trouble - it could turn out to be no improvement at all - but I've contacted Weber about getting a schematic, so we'll see how that goes and take it from there, I guess.

If you wish to keep the same frequency for the boost it may (probably will) be necessary to change resistance AND capacitance values to adjust it's amplitude and maintain the same frequency.

[Helmholtz]

Why not ask Weber for advice.
They know their units best and might already have a tried and tested solution.

[Boy Howdy]

All these years and I never knew that (mF = milli farad). Yeah, I meant micro.

All the tone stack stuff is located at the front, and there's only one big 2 microfarad cap at the rear. Sorta narrows it down. But I haven't had a chance to really get in there and see what's going on yet.

[Enzo]

Depends on how many years. 50+ years ago a millifarad was mostly theoretical, and mf would have meant micro. (and mmf meant micro-micro., which is modern pico) But these days you can easily buy 5 FARAD caps, and millifarad are not particularly rare.

[Boy Howdy]

My apologies for making you guys wade through this process. I guess I jumped the gun a bit. I should have explored my options a little more before asking for input.

I've found the appropriate 50 volt caps on ebay (Mouser, et al, is a bitch what with all the minimum order business). Likewise, I found the appropriate ceramic resistors. I even found a used (If that's a bad idea let me know.) wirewound rheostat for $50 (new they're like $85 from Mouser!).

Looks like going with the rheostat might be the easiest and best option in terms of adjustability. I might need to transfer everything into a new enclosure, not sure about any of that yet.

I listened last night to a bunch of recordings - both at bedroom volume and in a band context - and that 2uF cap has a definite effect on the sound. And again, I'm not unhappy with the frequency, actually I like it. It's just that those affected frequencies come through too loud. I still may experiment with that cap value though, curiosity being the better part of valor that killed the catfood . . . however that expression goes.

[Chuck H]

It would help us a lot to have an accurate schematic of the unit. There can't be much to it and I don't think it would be hard to draw one up. That way we could advise on the rheostat (or other resistor/s) and capacitor values and what you might hope to expect from proposed changes. As it stands I can't offer much on any of these matters.

[Enzo]

Mouser minimum order? As far as I know I never faced a minimum there. And quoting from their web site:

There is no minimum order value on products normally stocked in our warehouse. You can order a single part or thousands of parts from our inventory (subject to factory ordering restrictions shown).

[Boy Howdy]

Hmm, could sworn . . . .

[Boy Howdy]

pics

[Helmholtz]

Curious: Does the "speaker motor" vibrate in use?

[Boy Howdy]

I'm up to my eyeballs in busy right now, so this is a slow go, but so far it kinda looks like adding a second rheostat might be the way to go. One would fit right beside the present one if I were to remove the line out tone controls. I've never used those anyway - not even once, so. . . . Looks like it would be a simple matter of just sticking the rheostat in place of R7.

Weber hasn't replied to my inquiry about a schematic. I could possibly draw one up, but it may be a while before I could get to it, and I wouldn't have any way to get it online (that I can think of at the moment anyway.).