transistors in amplifier ear

[pil]

With what transistors can I substitute the ones in the amplifier ear?
http://www.electronics-lab.com/projects/audio/023/

I have the following available:

2N2222
2N3904
BC309
BC258

 

[Norm Dresner]

"pil" <pil@webmail.co.za> wrote in message
news:J5qdneL27N3PxG3dRVn-sA@is.co.za...

With what transistors can I substitute the ones in the amplifier ear?
http://www.electronics-lab.com/projects/audio/023/

I have the following available:

2N2222
2N3904
BC309
BC258

What was originally used?

 

[pil]

BC 547
BC 337

"Norm Dresner" <ndrez@att.net> wrote in message
news:TkZHc.80495$OB3.50723@bgtnsc05-news.ops.worldnet.att.net...

"pil" <pil@webmail.co.za> wrote in message
news:J5qdneL27N3PxG3dRVn-sA@is.co.za...
With what transistors can I substitute the ones in the amplifier ear?
http://www.electronics-lab.com/projects/audio/023/

I have the following available:

2N2222
2N3904
BC309
BC258

What was originally used?

 

[Paul Burridge]

On Sun, 11 Jul 2004 00:43:11 +0200, "pil" <pil@webmail.co.za> wrote:

BC 547
BC 337

"Norm Dresner" <ndrez@att.net> wrote in message
news:TkZHc.80495$OB3.50723@bgtnsc05-news.ops.worldnet.att.net...
"pil" <pil@webmail.co.za> wrote in message
news:J5qdneL27N3PxG3dRVn-sA@is.co.za...
With what transistors can I substitute the ones in the amplifier ear?
http://www.electronics-lab.com/projects/audio/023/

I have the following available:

2N2222
2N3904
BC309
BC258

What was originally used?

Just use the 3904s all through (first substitute) or 2222s mebe. Ought
to do the trick, I'd have thought. Without thinking too deeply about
it, of course.
I stand to be corrected, as always.
--

"What is now proved was once only imagin'd." - William Blake, 1793.

 

[Norm Dresner]

"Paul Burridge" <pb@notthisbit.osiris1.co.uk> wrote in message
newsov0f09r37fa0telo3ar462994ebvf089e@4ax.com...

On Sun, 11 Jul 2004 00:43:11 +0200, "pil" <pil@webmail.co.za> wrote:

BC 547
BC 337

"Norm Dresner" <ndrez@att.net> wrote in message
news:TkZHc.80495$OB3.50723@bgtnsc05-news.ops.worldnet.att.net...
"pil" <pil@webmail.co.za> wrote in message
news:J5qdneL27N3PxG3dRVn-sA@is.co.za...
With what transistors can I substitute the ones in the amplifier ear?
http://www.electronics-lab.com/projects/audio/023/

I have the following available:

2N2222
2N3904
BC309
BC258

What was originally used?

Just use the 3904s all through (first substitute) or 2222s mebe. Ought
to do the trick, I'd have thought. Without thinking too deeply about
it, of course.
I stand to be corrected, as always.

2N3904's are fine for Vceo and Ft. Their Hfe(min) is also similar to the
two BC's, but falls short of the BC's max by a factor of 2. It's not all
that obvious from a quick glance why two different transistors were used in
the original but I'd certainly try 2N3904's in both places and see what
happens.

Norm

 

[Walter Harley]

"pil" <pil@webmail.co.za> wrote in message
news:J5qdneL27N3PxG3dRVn-sA@is.co.za...

With what transistors can I substitute the ones in the amplifier ear?
http://www.electronics-lab.com/projects/audio/023/

To answer that question in general, you need to understand the circuit. No
two transistors are identical; what's important is that you use transistors
that are matched, or in some cases better, on the important parameters. I
don't know if you'll find someone on these groups who wants to go to the
trouble to understand your circuit for you - really, that's your own job.
But in a low-voltage audio circuit like this one, the parameters you most
likely care about are small-signal current gain (beta), maximum collector
current (Ic), and noise. Any transistors that meet or exceed the
specifications of the original transistors will do fine.

By the way, I notice that the rest of the parts seem to be wildly
overspecified. For instance, they specify 63V capacitors, in a circuit
powered by a 1.5V battery. So probably the transistors they used were
whatever happened to be in their parts bin at the time, and anything you use
will also be fine.