DIY Treble Booster

de-em · Post by **de-em** » 20 Aug 2007, 22:31

Please try it out...
http://forum.musikding.de/yabbse/index.php?topic=9760.0

soulsonic · Post by **soulsonic** » 21 Aug 2007, 00:32

Hey! I like this! I'll have to give a go with one of the 2SK117s I just got recently.
Thanks for sharing!

MoreCowbell · Post by **MoreCowbell** » 21 Aug 2007, 00:37

That looks very similar to a mod that was posted for the AMZ Mosfet boost a while back at DIY....I havent seen it used with a JFet, but should sound good. The pot panning between the two bypass caps is what was discussed there.

I might suggest subbing a 100k for the 330k resistor on the output, but overall this is a very nice design. THANKS !

de-em · Post by **de-em** » 21 Aug 2007, 12:23

MoreCowbell wrote:That looks very similar to a mod that was posted for the AMZ Mosfet boost a while back at DIY

Don't know anything about that.

I might suggest subbing a 100k for the 330k resistor on the output, but overall this is a very nice design. THANKS !

I don't know why you'd do that - it would just rob a little extra gain.

MoreCowbell · Post by **MoreCowbell** » 21 Aug 2007, 14:09

de-em wrote:
MoreCowbell wrote:That looks very similar to a mod that was posted for the AMZ Mosfet boost a while back at DIY
Don't know anything about that.
I might suggest subbing a 100k for the 330k resistor on the output, but overall this is a very nice design. THANKS !
I don't know why you'd do that - it would just rob a little extra gain.

Lowered output impedance

de-em · Post by **de-em** » 21 Aug 2007, 18:20

MoreCowbell wrote: Lowered output impedance

I can see where you are coming from but the resistor on the output doesn't really determine output resistance - it's more to do with the drain load resistor (27K) in parallel with the FET drain resistance and the source resistance. (The output cap also plays some part at lower frequencies). In other words it is somewhat less than 27K, so putting a 100K or 330K in parallel doesn't affect things much. The resistor is there to keep the output cap at 0V DC. If it's too low it will shunt the FET circuit and therefore reduce output which is the last thing you want really. Of course, it depends also on what you are driving. You could put an emitter follower on the output for better drive characteristics but I designed this circuit to keep things simple.

MoreCowbell · Post by **MoreCowbell** » 21 Aug 2007, 18:34

de-em wrote:
MoreCowbell wrote: Lowered output impedance
I can see where you are coming from but the resistor on the output doesn't really determine output resistance - it's more to do with the drain load resistor (27K) in parallel with the FET drain resistance and the source resistance. (The output cap also plays some part at lower frequencies). In other words it is somewhat less than 27K, so putting a 100K or 330K in parallel doesn't affect things much. The resistor is there to keep the output cap at 0V DC. If it's too low it will shunt the FET circuit and therefore reduce output which is the last thing you want really. Of course, it depends also on what you are driving. You could put an emitter follower on the output for better drive characteristics but I designed this circuit to keep things simple.

You probably know better than I, as I'm more of a guy who experiments with breadboards

BTW ...here's what I was referring to on the "treble booster modded" AMZ Mosfet Boost having a very similar setup....

https://www.diystompboxes.com/smfforum/ ... ic=56489.0

Here's a weird idea, you could make it pan between the full frequency boost - no boost (in the middle) - and then treble boost on the other end by re-arranging the pot. Wiper to the mosfet and zener diode, and one outer lug goes to a 100uF cap + side, and that cap's - goes to ground. Thats the full boost side. Attach the other free end of the pot to a much smaller cap to ground (+ to the pot side). Thats the treble boost. Use a 10K linear pot. I wager it'll work, because with the 5K pot, set up as a variable resistor, the gain is at its minimum when the MOSFET sees the full 5K resistance to ground (via the 100uF cap that lets AC signal through). So with the 10K pot stuck in the middle, it will see two 5K resistances to AC coupled ground. Those in parallel would make 2.5K, but I don't remember much happening in the first half of the pot's travel anyway. If you wanted the stock minimum gain sound, a 20K pot would be better. Or a would a 50K pot with two 10K resistors going from either outer lug to the wiper be a better taper, an "S" taper, like a mirrored version of the reverse log pot that is reccomended for the best feel in the stock booster?

de-em · Post by **de-em** » 21 Aug 2007, 18:46

BTW ...here's what I was referring to on the "treble booster modded" AMZ Mosfet Boost having a very similar setup....

https://www.diystompboxes.com/smfforum/ ... ic=56489.0

Here is my original post on DIYStompboxes:
https://www.diystompboxes.com/smfforum/ ... ic=53740.0

MoreCowbell · Post by **MoreCowbell** » 21 Aug 2007, 18:59

de-em wrote:
BTW ...here's what I was referring to on the "treble booster modded" AMZ Mosfet Boost having a very similar setup....

https://www.diystompboxes.com/smfforum/ ... ic=56489.0
Here is my original post on DIYStompboxes:
https://www.diystompboxes.com/smfforum/ ... ic=53740.0

I knew I'd seen it, but didnt know which came first. Not that it would matter either way. If I get a chance i'll throw this on the breadboard.

Heres a simple tone control ive used in the past...

grolschie · Post by **grolschie** » 22 Aug 2007, 06:05

Thanks for posting.