Shaka 5

[graemestrat]

It's not rocket science!

In the 2n7000 current flows from drain to source. The intrinsic diode is wired anode to source/cathode to drain, which allows current to flow source to drain, if the drain/source channel is off (ie in a high impedance state).

Where is R.G when you need him!?!!!

[Kipper4]

http://www.diystompboxes.com/smfforum/index.php?topic=58843.msg458654#msg458654

btw I'm using LRF520s

[graemestrat]

[graemestrat]

Hope this helps!

[Kipper4]

Still sound good the way we have it. Yes the character changes when the diodes are reversed .
If it's wrong how come nobody else picked it up in the last 15 yrs.
I'm not arguing just wondering.

[samhay]

>If it's wrong how come nobody else picked it up in the last 15 yrs.

It's not wrong, it's just one of several options.

http://www.diystompboxes.com/smfforum/index.php?topic=38581.0
http://www.diystompboxes.com/smfforum/index.php?topic=90474.0

[Cozybuilder]

Interesting. I had always assumed we were using the Mosfet internal diode as the clipper.

From the schematic I posted yesterday, a few R & C value changes, the most significant is the coupling cap from the Q2-S, I had 1uF, not 100nF in there, and that makes a huge difference in bass response. I tested down to 100nF, which kills the bass, 470nF brings it right back. In the tone circuit, like you I replaced 11K with 10K in the 3 Bass pot positions, in mid I changed 3K6 to 3K3 both positions, and for treble changed the 4n7 to 3n3, pot to B250K, and added a 330pF bypass to the pot (pins 1 & 3). So far, its sounding like a winner. 5 pots- don't see any way to stuff that in an LB, will have to look at 1590A instead 

[mac]

Mosfets as diodes, not the internal diode, have a voltage drop of 1v -3v.
Has anyone compared a mosfet with a fet like mpf102, and leds of different colors?

mac

[aron]

Yes, I know the Shaka 5 uses the internal diode. I just liked the sound more that way. Yes, I tried a ton of different configurations. I like series diodes the most.

[Kipper4]

I like it that way too Aron.
Thanks Sam I was looking for those all morning.
Maybe I'll put the diodes on a reverse ing switch and call it boost.
Thanks everyone for the input.
Some good discussion here.

[Kipper4]

Perhaps you'd like to expand on the series diode some aron. Where? Which? Polarity? Etc thanks

[graemestrat]

If you like the sound of the internal diode then why would you go to the expense of using the MOSFETS?
A cheaper alternative would be to stick any old diode in there and not bother using the MOSFET.
I don't think that there is anything special about the characteristics of the MOSFET intrinsic diode, but not too sure about that, will need to check.
That is why I suggested that there is a right and wrong way. Of course there is no right and wrong as far as musical taste is concerned!!

[Kipper4]

Don't get me wrong.
I'm grateful of your input Graemestrat and I'm sure i will put it to use in future.
I'm sure i read somewhere that part of the mosets character comes from the fact that it has a high capacitance compared to most others. Indeed when measured the capacitance was over 1nf on my little chinese tester.
I will probably test your theory and see if any old diode and a 1n34a combination sounds like too.
Every little helps when like me your on a slow learning curve after all I'm no EE. Everything I've learnt about pedals is mostly down to this forum thanks to guys like you willing to share there knowledge and take the time and patience and effort to educate us.
Tip my hat 

[graemestrat]

Thanks for the kind words, Rich.

[Kipper4]

Interesting. I had always assumed we were using the Mosfet internal diode as the clipper.

From the schematic I posted yesterday, a few R & C value changes, the most significant is the coupling cap from the Q2-S, I had 1uF, not 100nF in there, and that makes a huge difference in bass response. I tested down to 100nF, which kills the bass, 470nF brings it right back. In the tone circuit, like you I replaced 11K with 10K in the 3 Bass pot positions, in mid I changed 3K6 to 3K3 both positions, and for treble changed the 4n7 to 3n3, pot to B250K, and added a 330pF bypass to the pot (pins 1 & 3). So far, its sounding like a winner. 5 pots- don't see any way to stuff that in an LB, will have to look at 1590A instead 

Thanks Russ I'll try that maybe not in a 1590A though.

[aron]

> If you like the sound of the internal diode then why would you go to the expense of using the MOSFETS?A cheaper alternative would be to stick any old diode in there and not bother using the MOSFET.


You are probably right. However, remember at the time when I was playing around with this, I didn't know that. I was still purchasing a ton of "matching" transistors from the local store (when I was purchasing the same type over and over).
I just liked the sound and to me, it sounded different than my usual 1n4148 clippers.


As for the series diodes, I use them like the original Shaka Braddah.
http://www.diystompboxes.com/pedals/shaka.JPG

[Kipper4]

Thanks Aron

[graemestrat]

Thanks Aron,

Please understand that I am not "having a go" at anyone, I just wanted to understand how you came to be using the mosfets if it wasn't for their (to me) interesting sound. (see ROG's many mosfet circuits).

While I was thinking about all of this I came to realise that I really like the enthusiasm of you guys, it inspires me to do more than I normally would and that can only be a good thing, so thanks for that.

The other thing I should mention is that I come from an engineering background where "design reviews" are the norm. In these we are expected to "nit pick" each others' designs in order to come up with the best design. So that is the mindset from where I am coming....I am not trying to be negative as such. hope you understand.

Cheers,
Graeme

[Kipper4]

No thank you for the clarification and explanation.
I learnt something and will try it.
I guess it was the Right/Wrong thing that threw me. No offense taken or given.
We are all sonic travellers on the road to tone.
Rich

[graemestrat]

Thanks Rich.