Hi,
I am doing a Big Muff Pi build and it requires 2n3904 transistors.
I have a lot of them, but they are all from China and I am concerned about their quality.
I think they are very important to the build, but I will ask rather than assume.
Should I just order some from Mouser and if so, is there any particular one, value or parameter that I should look for .
-Mike
I think the short answer is that it doesn't matter provided they work, and the best way to find that out is to socket them and give them a try. It's not a rare or expensive part so the chances of you getting fakes shouldn't really be that high. But you never know. Trust your ears.
It terms of measurements, the measure that most people would go by is hfe. Whether you want higher or lower hfe is a matter of taste--some people even use MPSA18s and those are as high gain as you can get. The circuit is flexible and IME sounds good with most any type of transistor. You just end up with a slightly different flavour of distortion. I'd socket and try a higher gain set and a lower gain set. Then you'll have a good idea which you prefer and can go from there.
I think there is a Coda Effects blog post about the muff that talks about transistor choice. It summarizes a lot of the talk in the community about this.
https://www.coda-effects.com/2015/11/big-muff-mods-and-tweaks.html (https://www.coda-effects.com/2015/11/big-muff-mods-and-tweaks.html)
I recommend BC849C. If you're in the U.S., I'll PIF you a set. just PM your info.
If you order 2n3904 from mouser you'll be fine. It's a fairly ubiquitous transistor and Mouser sells vetted parts.
Remember, Mike Matthews and his crew made the most famous Real BMPs using the cheapest, bargain basement, buy-by-the-pile parts he could lay hands on.
As long as its an actual transistor and not a blob of plastic with some wires, it will function.
One of the things I did early on when I start building was get a Peak Atlas DCA Pro (I'm not saying you have to get this make or model, I was just able to find one at a steal of a price. I'm sure others can chime in on good semiconductor analyzers they have used that wont break the bank)
With this tool I was able to match the gain of transistors and test for faulty ones. This really became useful when trying to source in-spec J201 transistors.
-Cody
Cody,
Thx, I will put that down on my list. Can you measure leakage (is that the term?) with that as well?
M
Quote from: Ekimneets on September 12, 2018, 04:14:07 PM
Cody,
Thx, I will put that down on my list. Can you measure leakage (is that the term?) with that as well?
M
It can.
A 2N3904 is about the most common transistor in existence. It's going to either work or be DOA; the most likely variable is the gain, which matters in some circuits and not that much in others. It is also likely that most transistors you could buy are made in China, or if not, somewhere else nearby in Asia. The benefit of ordering from Mouser instead of some random ebay seller is that you get a vetted supply chain and a supplier whose reputation depends on 99.99999% reliable parts.
The Big Muff hs a reputation for sounding a little different depending on what parts you put in it, so it's possible that two different batches of transistors would sound different depending on their gains, without any judgment about their relative "quality" or tightness of spec.
For really generic parts like 2N3904, resistors, silicon diodes, basic op-amps, etc, generic sources are probably fine, especially for stompboxes. When you get into rare (unusual ICs, bucket brigade delays, etc) or highly variable parts (JFETs), that you should beware of too-good deals on places like ebay.
I don't have a Peak DCA, but do have a "GM328" cheapo parts tester that can measure values of passive components, transistors, and diodes. These cost only about $10 on, yes, ebay, and can be very useful if you want to sort parts.
Red desert,
Thx for the education, it helps a lot.
-Mike