Tuesday, 2 May 2017

Hornby Skewes Bass Boost

Another super rare Hornby Skewes pedal, so rare in fact I can't even find a video for it. Similar to the treble booster, but boosts the bass frequencies instead of the treble. I'm certain just like any other vintage Hornby Skewes pedal it's gonna sound great.

Layout 1: Original PNP


Layout 2: NPN Version



10 comments:

  1. built the NPN version on breadboard with MPSA18 and it works, though I had to leave out the 1k to ground 8F to get decent volume. I ultimately built with a few value changes - 100nf to 82nf and 125uf to 100uf. Sounds great on bass guitar, less so on 6 string..I guess it works like clean boost with more bass in it as described.

    Fun circuit to experiment with as I am just trying to teach myself how to set gain in a circuit.

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    1. nice. leaving out that 1k to ground takes out the filter network at the output, and makes the 100nF go nowhere, so i don't think it would sound the way it should. how low was the output with that 1k to ground attached? i don't think it gives much of a boost, just a little bit. i mean there's not output control, so i can't imagine it being all that much.

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    2. I put it back in and it's way less than unity with it. I put 10k in and it increased the volume to above unity.

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  2. I built the PNP version with a 2N3906, I used a 100uF electrolytic instead of a 125uF. Tag it, it works!

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  3. https://drive.google.com/file/d/0B1xf8RhQa21vcnVUY0pMVjljZWs/view?usp=drivesdk

    Short sound clip playing bass recorded on my phone

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    1. hmm, sounds pretty good to me. to me it sounds like without the resistor, and 100nF to ground it sounds fairly woofy to me, but with the 10k resistor it definitely boosts the lows, but retains some articulation. i dig it. since you have it on the breadboard, and you don't need to try and record another clip if you don't want to, with the 1k vs 10k does it have same tone?

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    2. I agree it sounds better with the resistor in but with the 1k it's just not possible to compare against the 10k due to the large volume drop.
      I've been experimenting a bit and have a pot from 9v to the collector (and a 27k ~roughly~ resistor which was about the max increase in volume before it distorted in a not nice way), I assume this adjusts the bias?

      Anyway here is a clip on guitar on an already pretty crunchy amp thst I forgot to record, you can hear me fiddling with the pot/bbias/gain

      https://drive.google.com/file/d/0B1xf8RhQa21vTDdubzg5cW44TEU/view?usp=drivesdk

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    3. yep, that's playing with the bias. i'm sure the reason for the lower output comes down to the transistor that's being used in place of the 2n3702 in the original.sounds pretty damn good to me.

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  4. This comment has been removed by the author.

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  5. I can provide pictures of the Hornby Bass Booster if you're interested. Didn't even realize it was a rare thing, since i just got it for free off some stranger on FB.

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