Cut Bass in BSIAB II mod?

[hilbi]

Is there a mod for the BSIAB II to cut some bass (punchiness)?

[WGTP]

The cap's between the 2 Jfets in the mu-amp have a significant effect on the bass and overall tone.  Reduce those for less bass.   

[Headshot]

Could you expand on this??  What is a Mu amp, and where is it in the BSIAB II circuit?

Thanks.

[dosmun]

The BSIAB is based on Jack Ormans Mini Tubes which is 2 Mini Boosters.  The
Mini Booster ia also known as a mu-amp

[hilbi]

Can someone tell me wich caps these exactly are? See schematica above.

[DuncanM]

You could try reducing C2 (or C4) or C7 (or C12) depending if you want less bass before or after the signal gets overdriven.

Might also be worth trying a .01uF cap as a replacement for C8 in the tone control. 

[hilbi]

Thanks for you help DuncanM,

I would like to cut down the oophm factor a bit, im not sure if it is better to creduce caps in the clean part or the overdriven part.

Might also be worth trying a .01uF cap as a replacement for C8 in the tone control.

What does this mod do? also cut bass?

[DuncanM]

Changing C8 alters the response of the tone control - in the original, there seems to be a 100Hz hump when the tone control is in the middle, a 'bass boost/treble cut' when the tone is anticlockwise and a 'bass rolloff and boosted' response when turned clockwise (at least, that's what playing with the "Duncan Tonestack Calculator" seemed to imply.
Changing the Cap to 0.01uF makes the response more like a traditional Big Muff type tone control - slight dip at 300hz in the middle, 'bass boost/ treble rolloff' anticlockwise, 'treble boost/bass cut' clockwise.

[hilbi]

Ok Thanks DuncanM,

I think I will try changing C8 first because i'm really happy with how the tone control works, i leave it all the time at 03.00.

[DuncanM]

Out of interest, is the tone pot 100k Lin or 100k Log?

[hilbi]

I think I will try changing C8 first because i'm really happy with how the tone control works, i leave it all the time at 03.00.

Sorry I forgot one important word here. I mean NOT really happy.

Out of interest, is the tone pot 100k Lin or 100k Log?

Don't remember anymore, I will have a look tomorrow.

[hilbi]

I used a 100kb pot for tone, is that lineair or log?

[hilbi]

You could try reducing C2 (or C4) or C7 (or C12) depending if you want less bass before or after the signal gets overdriven.

Might also be worth trying a .01uF cap as a replacement for C8 in the tone control.   

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Mm c8 is already 10nF in my bsiabII, probealy a vaue mistake at that time.

I changed c4 and C12 now to 18nF, the bass is cecreased a bit now, will try that in a band situation next week and see how it works.

Can anyone tell me if a 100kB pot is lineair or log?

[Bucksears]

100K-B is Linear. 100K-A is Log.

- Buck