Beginner's question: What components do you recommend

[ghaudio]

Hello

Being an electronics engineer and a high-end afficionado I want to try and build my own DIY solid-state power amplifier. While I certainly have the knowledge to come up with a schematic and make it work I have no clue whatsoever what components to use.


I am particularly looking for:

• dual matched n-channel JFETs on a single chip;
• complementary n/p-channel Power MOSFETs.

They should perform well regarding audio requirements, of course, meaning:

• well-matched;
• low noise;
• high bandwidth;
• high slew rate.

And another question: how critical are the tolerances of resistors according to your experience?

Thanks in advance for any advice from you experienced guys.

gh

[indianajo]

Look at this thread. Easy to find, inexpensive audio power transistors (BJT and FET)? There is another thread that gets to FET's quicker, but I can't find it.
At newark.com I'm paying 6 to 2 cents for 5% metal film resistors, so the old matching games are gone. Certain things like feedback etc, the two channels had better be 5% matched to get the same gain. But transistor mismatch can be as bad. I buy a dozen transistors at a time when I can afford it to try to get similar parts. Same with resistors. Out of a dozen resistors on the same tape, they may all be 4.9% off center but they will usually be pretty close to each other.

[Mooly]

Resistor tolerance in practice isn't normally critical with the exception of feedback determining networks and current mirrors... with feedback if the resistors differ left to right channel then so will the gain.

1% metal films are pretty standard these days... its just not an issue.

Can't help you with the matched jfets on one chip, and as to the power MOSFET's, well the circuit design is probably the limiting factor with regard to noise and slew rates/bandwidth etc.

[lineup]

1% metal film resistors.
You can start with buying a package, 5 or 10 each of 10 Ohm-1 MOhm

Polyester film capacitors are a must. From pF upto 4.7uF

Dual JFET on one chip exist. But are rare to find. Like searching GOLD!
But you should get a bunch of 2SK170. They are pretty much standard N-JFET.
Then you can match pairs yourself.
BF245A, BF245B are useful for constant current sources.
2N3819 is dito.
By using lower cost, readily available JFETs as CCS, constant current sources we save some money.
And save 2SK170 for the input circuit.

Complementary small signal BJT transistors 120V collector-emitter, low-noise, easy to find and use are 2SC2240/2SA970.
Complementary small signal BJT transistors that can take a bit more power are 2N5551/2N5401.

For medium power transistors you have BD139/BD140. Very useful.
If you can buy 2SC2911/2SA1209, then do. Better performance in most applications.

For lower power MOSFET (HEXFET) you should have IRF610/IRF9610

High power MOSFET is something that goes with current application.
Not much use really to have them at home.

[ghaudio]

Thank you very much for your valuable hints

I will check what is available and then evaluate the data sheets.

gh