DPDT true bypass?

[DaKurt]

Hi,

can I make a true bypass just with a DPDT switch or do I need the 3PDTs?


Kurt

[amz-fx]

True bypass wiring of the DPDT:

http://www.muzique.com/schem/dpdt.gif

An article about the Rat bypass:

http://www.muzique.com/lab/true_bypass.htm

regards, Jack

[R.G.]

An article about the Rat bypass:

Hey! How about that - they adopted the JFET from the Millenium 1.

I wonder why they didn't use the diode leakage bias, too. Maybe because the output pot on the rat is low enough to keep the pops down from the 22M. I'm surprised you didn't mention the Millenium in the article.

Neat trick with the two series diodes - run the LED voltage up so much that any JFET threshold problems get washed out.  But with a low Vgs-off device like the 2N5485, the problems are moot anyway; they could have just specified another device.

[amz-fx]

Hey! How about that - they adopted the JFET from the Millenium 1.

They have been using a jfet for a long time...  I'm not sure how long but all of the one's I've seen have had the jfet instead of the darlington.  I repaired a Rat version that was before the Rat 2 and it was a 2N5457 but I'm not sure when they made the switch...  

The diode trick on the source is clever in that it virtually eliminates problems with the Vgs of the fet, and would be an option for anyone using the Mill 1, especially if they have to use an BF245, MPF102 or 2N5457 instead of the fet you mentioned.

best regards, Jack

[DaKurt]

Ok, that's good. But can then anyone tell me when I have to use 3pdt switches?

[smoguzbenjamin]

Whenever you want to have an easy time wiring up the LED It doesn't really matter if you use a FET etc to switch the LED, at least the 3PDT is fool-proof.