Author Topic: Re Transistor Specs  (Read 247 times)

Black Napkins

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Re Transistor Specs
« on: July 29, 2018, 08:51:54 PM »
Hi Folks,

I'm gathering parts for the Pangea build & have found myself lost in 'Specification land' with the options for component choices.
Hope someone can help with some info. Sorry if this is a stupid question.
My choices for a 2N3904 Transistor differ only by DC Current Gain. Is this spec better to be higher or lower or does it really not matter at all in the context of a 9Volt stomp-box?
I have choice of 30, 100 or 300 hFe.
Just wondering :)

Thanks
Matt
« Last Edit: July 30, 2018, 04:58:40 AM by Black Napkins »

reddesert

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Re: Re Transistor Specs
« Reply #1 on: July 30, 2018, 11:30:47 AM »
The TLDR: it likely doesn't matter.

A 2N3904 is a basic NPN silicon transistor, one of the most common parts in guitar (or any other) circuits. It's unlikely that you would actually get a 2N3904 with a gain as low as 30. Most silicon transistors have gains over 60 or 100, especially newly made ones - even the cheapest 2N3904s I have got recently had a gain of about 150 or more. The specs in the datasheet are usually a guaranteed minimum, that is a part must meet several specs to be called a 2N3904, but it could and probably will exceed the specs.

I don't know what the Pangea circuit is. Apart from early / simple circuits like a Fuzz Face, most circuits aren't very sensitive to exact values of transistor gain; they will work with either a gain of 100, 200, 300, ... because they use feedback to control the amplification of the transistor.

ahiddentableau

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Re: Re Transistor Specs
« Reply #2 on: July 30, 2018, 11:57:38 PM »
What's a pangea?  I don't think I've ever heard of that circuit.  Got a link?

somnif

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Re: Re Transistor Specs
« Reply #3 on: July 31, 2018, 12:28:53 AM »
I'm guessing he means Brejna's Voodoo Vibe clone called "Pangea" ( I could be wrong of course)

stringsthings

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Re: Re Transistor Specs
« Reply #4 on: July 31, 2018, 04:50:36 AM »
Hi Folks,

I'm gathering parts for the Pangea build & have found myself lost in 'Specification land' with the options for component choices.
Hope someone can help with some info. Sorry if this is a stupid question.
My choices for a 2N3904 Transistor differ only by DC Current Gain. Is this spec better to be higher or lower or does it really not matter at all in the context of a 9Volt stomp-box?

I have choice of 30, 100 or 300 hFe.
Just wondering :)

Thanks
Matt

( disclaimer:  i have a cold and may be under the influence of drugs ... )

Hi Matt,

Didn't your teachers always say, "Matthew, there are no stupid questions."?  ( insert inspirational quote here )  :D

Welcome to the wide world of component gathering.  As reddesert posted, the 2N3904 is your best friend when it comes to NPN transistors.
It will happily work in many stompboxes.  It's a good idea to buy extras.  They're really inexpensive and will, most likely, out-live most of us.
So the short answer to your question is:  it really does not matter. 

The long answer is full of graphs, numbers and probably equations which would probably bore you to tears.   
So please, please, don't ask us for the long answer!  :D :D :D
All You Need Is Love

Black Napkins

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Re: Re Transistor Specs
« Reply #5 on: August 02, 2018, 04:39:35 AM »
Thanks for the input all :)
Yes, it is Brejna's Pangea build.
I was obviously getting in too deep while shopping around for parts. Appreciate the guidance to bring me back to reality :)
I have trawled through many store component listings & options these past few days and I think I may have almost recovered.
I found myself in that dark place caught between choosing the correct components to do the job as well as possible & those minor spec differences that can at times mean a 3 fold price difference & all possibly for a component spec that may or may not even be relevant in the slightest :)
Thanks for the help :)

Cheers
Matt