Guitar Bass Driver mod question. Trying to reduce the bass output. (solved)

[e_man]

I finished building a GBD3 board that I’ve had around for a while.  I used J201s since I didn’t have any 2N5457s on hand, all other components are stock.

I noted in the build documents that you can increase the bass output by increasing the value of C1, C3, & C16.

I’m guessing that it would be possible to lessen the bass output by reducing the value of these 3 caps.  My Les Paul is a little bottom heavy anyways and into this circuit it is way too much.  I can run the bass at zero and the treble at 3 o’clock or higher and it almost gets right.  I think it has some great potential.  All of the GPCB amp emulation preamps I’ve built have been great!

Are my assumptions about the three caps mentioned right? Are there any other component changes that would help bring some balance?

As always, thanks for help and input.

[Barry]

You can just lower C16 to 18n, or 22n.

Let me know how that works.

If your Les Paul is overly Bass heavy measure your pickup height with strings depressed at the 22nd fret and compare. Gibson recommends 3/32″ on the bass string side and 1/16″ on the treble string side.

[e_man]

Thanks for the help Barry.  I socketed the C1, C3, &C16 locations and went with 47nFs at the 3 locations.  MUCH better!

I can run the bass knob around 11 o’clock and get a good balance of tone.  I’ll try your recommendations at C16 and let you know.

I run my pickup height kinda low.  In comparison to my SG or strat, the neck pickup on the LP can get dark, but it’s one of the things I love about it.  The stock BurstBuckers are awesome to me.

Again, thanks for advice on the cap values.

[e_man]

I understand that statements like “too much” are subjective and that that condition can be different for different people.  I can hear that this circuit has an open uncompressed sound and feel like if I can get the EQ better balanced it’s going to be a great circuit for me.  BTW, I’m running both pickups while testing, occasionally checking the bridge and neck.  Both pickups together is kind of my reference when I test drive stuff.  By the way, I finished a Black Dog board last weekend and it is fantastic with my LP in the middle position.

Ok, I spent a little while testing different cap values @ C1, C3, &C16.

First, I placed 47nF at all 3 locations.  This lessened the bass level and improved the clarity.  It still needed the bass control set very low if not off.  It did have more highs present.

Second, I replaced C16 with a 22nF.  This was a barely discernable improvement, still requiring the bass knob nearly off and the treble maxed to come close.

Third, it was 22nF & C1 & C3 with 15nF & C16.  Not much difference at all.

Fourth, 15nF & all 3 locations.  Better, getting closer to what I’d like, but still almost no bass control with treble at 3 o’clock.

I’ve checked my component values and don’t see any problems ( and I paid special attention to my “47’s”).

I’d be interested to hear from other people who have built this circuit and what their experience with it’s bass response was.

I’ll check my components again and verify.

Thanks.

[Barry]

I would start checking your resistor bands by color and verifying. Particularly around the tone sections.

This is one of the oldest circuits I have so you can try a forum search as well.

This demo shows my Les Paul with GBD and the Bass is at 1:00 and the Treble is at 11:00

Pedal has same settings used in the demo. I never changed them.

The switch you see at the top just changes C16 from 100n to 22n.

[e_man]

I received the 2N5457’s I ordered and replaced the J201’s I installed initially.  This was my problem.

With the 5457’s the bass eq control is more effective.  Both tone controls seem to more responsive.  (I reinstalled the original cap values @ C1, C3, & C16)

The pedal sounds more like Barry’s demo.  I’m calling this one solved.

Thanks for your help with this one Barry.

[Barry]

I am glad to hear that. Thanks for reporting back.

Feel free to add my modification as well. You can use a DPDT switch to toggle between the 22n and stock capacitor connected to C16, creating a Bass/Guitar switch. A 10n capacitor is particularly effective with smaller amp cabinets.

[Author]

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