Author Topic: NPN transistor choice (finished pedal. just considering other transistors)  (Read 10163 times)

Little_Horn

I finished the pedal. It's working great. I used a 2N2222 transistor. But the thing is, I was expecting to get more volume from the booster and instead, I just get more gain. Don't get me wrong, the sound is extremely transparent, the gain is awesome and I get lots of sustain but, I wanted a certain raise in volume so when soloing, the notes would stand out more! So, any suggestions about trying different NPN transistors? I put it in a socket, so it's easy to replace.

Don't know if the link works but, these are the photos of the finished pedal in Facebook: http://www.facebook.com/media/set/?set=a.293222074056120.72770.100001049905616&type=3

Thanks.

Little_Horn

Re: NPN transistor choice (finished pedal. just considering other transistors)
« Reply #1 on: September 08, 2012, 11:39:37 AM »
UPDATE: Well, turns out I was only using the boost pedal before the distortion and not after. But more on that later.
This pedal was tested yesterday on a Randall Nuno Bettencourt half-stack.

Amazing sound. First it was tested in the front of the amp on the overdrive channel.
The guitar was a beautiful white 7-String Dean RC7x (Rusty Cooley signature model).

The gain setting on the amp was somewhat low. maybe 1/4 or a little more.
As expected, the booster only provided more saturation. But what I noticed was that, to the end of the dial, the booster started to get a little fatter in a very pleasant way. Turned all the way, it provided incredible sustain and a fuzz like sound. very cool.
Having done that, we tested the boost on the clean channel. Wooooooooow :o
The booster provided and excellent increase in volume before the sound started to get saturated. And when it did, because it was with the boost's dial turned fairly up, we got that nice fat tone ideal for blues or rock. Very nice!
But there was still a big test missing: how would this boost behave on an fx loop?
So today, I tested it at my home, with my amp and my cabinet. It's a half-stack also.
The amp is a Dime Amplification Dime D100 Head.

This amps distortion is not bad but, it has definitely a character that reminds me of Dime's sound. So, I use it with a preamp pedal connected directly to the fx loop return, to bypass the preamp stage of the amp. The pedal is an AMT E1.

The cabinet is a 4x12" with Jaguar speakers. They sound great but are a little scooped. Just have to compensate on the medium frequencies a bit. :P
I don't know the exact model but the cabinet looks like this


Testing the Boost in front of the pedal gave the expected results: more saturation.
But testing the Boost after the pedal gave me a huge increase in volume!!!! :D
So much volume in fact that using the Boost with the dial turned all the way down (zero) even gave me a little too much increase in volume for my taste, I should say.
But maybe in the context of a band, this minimum setting is not too much at all...

Yesterday I was checking out some handmade Boost pedals and realized that there are a lot o people using the 2N5088 transistor. I'm using the 2N2222A and getting great results but, would it be worth it to change the transistor to a 2N5088? Or do you even suggest any other transistor? Would the level be more controllable with a 2N5088 (I'm referring specifically to the dial in the zero position and still having too much increase in volume)? I don't need more gain, just more control. Can anyone help on this one? Thanks.

artifus

Re: NPN transistor choice (finished pedal. just considering other transistors)
« Reply #2 on: September 08, 2012, 11:48:00 AM »
the magic word is 'datasheet'

type that into google preceded or followed by the name of your device and compare and contrast the numbers with the device you are are considering a sub for. that's what they do. crunch numbers. sometimes like an abacus and sometimes like a digital calculator but it's all number crunching. there's mojo in there somewhere, or so i'm told, but the numbers are a good starting point.
« Last Edit: September 08, 2012, 11:49:33 AM by artifus »

Gus

Re: NPN transistor choice (finished pedal. just considering other transistors)
« Reply #3 on: September 08, 2012, 12:55:58 PM »
The different transistors shift the bias a small amount.  The bias network is designed to work with a range of hfe values.

A way to pick a transistor is to try different silicon NPN transistors, 2n4401, 2n3904, 2n2222, 2n5089, 2n5088, MPSA18 etc.  Some people like the 2n2222 and others a higher hfe one like a 2n5088


« Last Edit: September 08, 2012, 12:58:30 PM by Gus »

Little_Horn

Re: NPN transistor choice (finished pedal. just considering other transistors)
« Reply #4 on: September 10, 2012, 08:18:02 PM »
I did check the datasheet and 2n5088 has a much higher hfe than 2n2222. But I'm not looking for more gain. The pedal has enough as it is. Just looking for a simple way, if possible, of having better control on the volume, when using it after the preamp. In the "zero" position, the increase in volume as soon as I press the switch is a little too much. It should stay close to unity gain. any suggestions?

midwayfair

Re: NPN transistor choice (finished pedal. just considering other transistors)
« Reply #5 on: September 10, 2012, 09:47:55 PM »
I did check the datasheet and 2n5088 has a much higher hfe than 2n2222. But I'm not looking for more gain. The pedal has enough as it is. Just looking for a simple way, if possible, of having better control on the volume, when using it after the preamp. In the "zero" position, the increase in volume as soon as I press the switch is a little too much. It should stay close to unity gain. any suggestions?

You just want less total volume available in all settings? The simplest way is to reduce the size of the 100K resistor at the output. Try 68K or 47K. This will change the cutoff frequency in a way that might be non-trivial on the lowest notes of a bass guitar, but there's a reason I qualified that with "simplest."
My band, Midway Fair: www.midwayfair.org. Myself's music and things I make: www.jonpattonmusic.com. DIY pedal demos: www.youtube.com/jonspatton. PCBs of my Bearhug Compressor and Cardinal Harmonic Tremolo are available from http://www.1776Effects.com!

Gus

Re: NPN transistor choice (finished pedal. just considering other transistors)
« Reply #6 on: September 11, 2012, 06:56:07 AM »
The circuit has a gain of about x2 at min gain with the 5K gain control and 10K collector resistor.
You can try a 100K volume control instead of the 100K resistor at the output.

Little_Horn

Re: NPN transistor choice (finished pedal. just considering other transistors)
« Reply #7 on: September 11, 2012, 04:23:03 PM »

That's actually simple. I'm thinking of replacing the 100k output resistor for a 100k trimpot (just like the ones above). This is adjustable and stays inside of the box. Plus, anyway, adjusting it will be a one time only type of thing so, there's no need to have it outside of the box. I play guitar and usually play in B standard or Bb standard. But sometimes I can go to Ab standard. Don't think this will be an issue because of the cutoff frequency. But even if this pedal is ever used on a bass, all I got to do is put the trimpot back to 100k. :) What do you think?

midwayfair

Re: NPN transistor choice (finished pedal. just considering other transistors)
« Reply #8 on: September 11, 2012, 05:02:45 PM »

That's actually simple. I'm thinking of replacing the 100k output resistor for a 100k trimpot (just like the ones above). This is adjustable and stays inside of the box. Plus, anyway, adjusting it will be a one time only type of thing so, there's no need to have it outside of the box. I play guitar and usually play in B standard or Bb standard. But sometimes I can go to Ab standard. Don't think this will be an issue because of the cutoff frequency. But even if this pedal is ever used on a bass, all I got to do is put the trimpot back to 100k. :) What do you think?

I was being facetious. You don't need to worry about the cutoff frequency in this build with any instrument that plays notes in the range of human hearing.

Crocodiles might feel differently about the change.
My band, Midway Fair: www.midwayfair.org. Myself's music and things I make: www.jonpattonmusic.com. DIY pedal demos: www.youtube.com/jonspatton. PCBs of my Bearhug Compressor and Cardinal Harmonic Tremolo are available from http://www.1776Effects.com!

Little_Horn

Re: NPN transistor choice (finished pedal. just considering other transistors)
« Reply #9 on: September 12, 2012, 12:31:36 PM »
Well, I'm considering to reduce the collector resistor to 5k to get unity gain. This would be ideal to use the boos in the fx loop just ti increase volume. But when using it in the front of an amp to saturate the tone even more, 2x (10k) would be nice. So, I think I'll use a 10k trimpot on the collector. :P This way, it's adjustable if or when I need it to. What do you think?

Thecomedian

Re: NPN transistor choice (finished pedal. just considering other transistors)
« Reply #10 on: December 21, 2012, 08:54:33 PM »

That's actually simple. I'm thinking of replacing the 100k output resistor for a 100k trimpot (just like the ones above). This is adjustable and stays inside of the box. Plus, anyway, adjusting it will be a one time only type of thing so, there's no need to have it outside of the box. I play guitar and usually play in B standard or Bb standard. But sometimes I can go to Ab standard. Don't think this will be an issue because of the cutoff frequency. But even if this pedal is ever used on a bass, all I got to do is put the trimpot back to 100k. :) What do you think?

As a side note, These little blue guys are pretty nice in terms of high control of accuracy with very slow rotation. The only problem I find with them is that their legs are a bit weak, so they seem like they'd break easily after too much wear. Those flat disc trimmer pots would be good for fiddling around with something more often, I think.
If I can solve the problem for someone else, I've learned valuable skill and information that pays me back for helping someone else.