question on Hornby Skewes treble booster tweaks ??

Discussion regarding early stompbox technology: 1960-1975 Please keep discussion focused and contribute what info you have...
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Post by bobster »

hi folks ,
built a hornby skewes booster with an OC44 and its sounding good . The following ideas may be useful in some way if i can work out how to do them lol

There is quite a large boost with noticeable hiss and for the places i play the volume level is harder to control with it 'cooking ' ....

so what i'm thinking -

is there a simple way to calm this circuit down a bit [ attenuate if you like ] ? and reduce the hiss perhaps with small value caps

with my limited knowledge i'm wondering if some kind of master volume control could work ? i don't know where to tie a MV pot to in the circuit though but i could solder one in if i knew where to place it

also , maybe a couple of caps placed in certain slots e'g between collector and base [or is it emitter] ?

i've always liked treble boosters with old valve amps but have also always wanted to keep their tone but calm them down a bit so the boost isn't quite as alarming ?

any thoughts from the more experienced ? thanks

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Post by Nocentelli »

As you can see there a few different schematicss for the hornby skewes treble booster. Assuming you have done the pnp version like the tagboard vero version, a small cap (100p-220p) between collector and bass can remove a bit of hiss at the expensive of the jangling top end. For a master volume, remove the 100k resistor from the output cap, and replace it with a 100k log master volume pot, lug 3 to the end of the output cap and lug 1 to ground: lug 2 is the new attenuatable output.
brownwhopping wrote:How can I learn by reading threads an making circuits, when some day I can see a lawsuit or somebody beat me in the face for that?

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Post by bobster »

thanks for that , great info - just what i needed :thumbsup

i have the input cap at 27n and the output at 10n so it's quite beefy but still with plenty of top, its on a tag board and i copied the original from e bay photos including the switch that drains the battery unless turned off lol and the massive pop when turning on , [ yes im a blackmore freak :D ]

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