Author Topic: switchable transistors  (Read 5136 times)

per_electric

switchable transistors
« on: February 21, 2006, 05:57:56 PM »
Hi,

I'm thinking about adding a switch so that I can choose another transistor without having to open the box up. I haven't actually built anything yet, I'm just playing around with ideas and see where I end up. However, I would like to get some input on what transistors to use. I guess many of you have tried changing the transistor, and I would like to know what you thought of the different types; which are your four favourites?

Thank you, all!!
Per

aron

Re: switchable transistors
« Reply #1 on: February 21, 2006, 07:31:11 PM »
My favorite is the one I mentioned 2N2222 metal can.

per_electric

Re: switchable transistors
« Reply #2 on: February 28, 2006, 10:27:33 AM »
Thanks Aron!!

Another question; how much difference in sound does different transistors do? Will it be worth all my trouble adding switches and stuff? And can I leave the base of the transistors connected at all times (just switching the collector and emitter)? Will I need any kind of pull-down resistors to avoid pops when I switch, and where do I put them? ???

Just one questions left (at the moment); is the 2N2222 metal can a "special edition" of the 2N2222, or are they all metal cans?

Thanks a million!! :)

aron

Re: switchable transistors
« Reply #3 on: February 28, 2006, 01:26:49 PM »
I've never switched transistors. My hunch is that doing so might create a loud transient.... but I'm not sure. The 2N2222 come in "plastic" and metal can. I like the metal can versions but I guess I haven't tested the difference between the two a lot... but my foggy memory tells me the metal is better  ;)

cab42

Re: switchable transistors
« Reply #4 on: March 10, 2006, 05:09:05 AM »
Hello Per,

You might be interested in this method to switch transistors by Dragonfly posted in the gallery:

http://aronnelson.com/gallery/The-Mod-Zone-%21/TRANSISTOR_SWITCHER

I was lucky to get some old germanium NPN trannies (OC140) on ebay and have considered using them in the NPN-boost. It has been done with succes by others.

Regards

Carsten
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Khas Evets

Re: switchable transistors
« Reply #5 on: March 11, 2006, 02:17:12 PM »
Which transistors to try depends on the circuit. I would focus on the hfe (gain) of the transistor.

The switching method above will work, and I would expect it to pop. Another alternative (which I've read here but haven't tried) is to use a DPDT switch and tie the emitters together (probably will also pop). Also, while the differences between trannies are subtile, they do make a difference. I would recommend using a toggle switch rather than a stomp, but it's up to you.

per_electric

Re: switchable transistors
« Reply #6 on: March 12, 2006, 09:00:22 AM »
@cab42
Yeah, it's somehting like that I have in mind. I'm thinking of using a rotary though, three or four throws.

@Khas Evets
Is it better to tie emitters than bases? Is there any way to avoid pops?

Sody54

Re: switchable transistors
« Reply #7 on: February 16, 2007, 06:22:54 AM »
I used Dragonfly's tranny switching mod in mine.  Just hooked them up to either side of a DPDT toggle switch.  I switch between a 2222 and a 5088 with very little pop.  It's noticeable that you switched something, but not anything that's going to sound oout of the ordinary.

Brian

ambulancevoice

Re: switchable transistors
« Reply #8 on: March 09, 2007, 09:20:12 PM »
there is minature 3pdt toggles you can use for this
easy
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