Renometer HI-BOOST

[AS74]

I've been trying to grasp the HI-BOOST circuit but with my limited knowledge can't.

Will somebody be kind enough to explain a little? 

Where is the HI-BOOST getting it's input signal?

Is HI-BOOST running just on +9V or -9V?

Which components effect the boosted frequency's?

Thanks

Adam.

[duck_arse]

T1, the jfet, is yer man. the hi-boost switch switches it's Drain-Source channel high resistance or low resistance, which takes C2/R5 in or out of the feedback loop (to ground), affecting the boost freqs. [proper explanations will follow from those properly qualified.]

[PRR]

As said, all that stuff up to and including the JFET can be replaced with a dumb switch.



The filtered drive to the JFET may be less clunky than the switch. But for understanding the Hi-Boost, it is just a switch.

[AS74]

Thanks guys. 

So the mechanical switch is a switch to activate an electronic switch.

[duck_arse]

I'm baffle by the use of double pole switches on that circuit, seeing as the poles are parralelled. single pole would do in both cases.

also - an eagles fan? [no, not hotel california eagles, the other kind.]

[AS74]

Not a huge footy fan, would rather jam. 

But I did watch a little. Last quarter was good.  Close games always get a little adrenal flow. 

I'm a Westy so I'm glad the eagles won. 

[thermionix]

I'm baffle by the use of double pole switches on that circuit, seeing as the poles are parralelled. single pole would do in both cases.

It adds reliability.  Makes the schematic more confusing though, would be better depicted as SP.

[AS74]

Which components are responsible for the hi boost frequencies so I might tame it a little?

Thanks

Adam.

[blackcorvo]

R5 and C2 are responsible for the boost in high frequencies.

Changing C2's value changes the frequency being boosted:
higher value = lower freq;
lower value = higher freq;

Changing R5's value changes the gain of that boost:
higher value = lower gain;
lower value = higher gain;

If you just want to reduce how much gain it has and not mess with the tone, you could add a 50K trimmer in place of R5 and adjust the boost to your taste.
If you think it's too trebly, you could try adding a capacitor in parallel with C2 to lower the frequency of the boost.

[AS74]

Awesome, thanks.