[scootsit]

Hey guys, thinking of building a Szekeres current follower for a friend of mine.
I have a question, I know that for my Mosfet Max, transistor matching was necessary, is that the case for the Szekeres?
It would seem to me like it should be, but I have found no mention of it anywhere.
Thanks!

 

[Avro_Arrow]

Not really.
I matched the IRF510 in mine, but I built a DC coupled version.
 
You can build the simple, resistor CCS version, the LM317 CCS version
or the LED CCS version.

 

[nikongod]

The Szekeres is a voltage follower.
 
Mosfet matching is not really necessary in the Szekeres. Just get 2 that are labeled the same and drop them in. I would order 4 in case you blow them up  
 
The output stage in the millet max uses complementary transistors. Getting them to work at their best requires matching. There is only one transistor in the szekeres, so it doesnt need to be matched to a mate.
 
Channel to channel matching is also unimportant. Its a BUFFER! Even with SERIOUSLY mismatched parts (that are labeled the same and not fakes) you wont be able to hear a difference. 

 

[scootsit]

Great!
Thanks for the info, guys.
 
I'll probably go for the simple, or original design.
Haven't actually decided to go for this yet, I've been crazy busy with work, but I'd like to do it.

 

[scootsit]

I cannot seem to find the 5W, 20z resistor for R4.
I'm thinking of either increasing the resistance and decreasing the wattage, or going some other route.
What exactly does R4 in the original schematic "do"?
Thanks a ton!

 

[dsavitsk]

It sets the current going through the FET. If the FET is biased at 9V (not sure what schematic you are looking at), and Vgs is ~4.5V (for the IRF510 and IRF610), then the resistor drops the remaining 4.5V. Using V=IR you can determine the current through the resistor (4.5/20 = 225mA in this case). Wattage = VI, so in this case you'd need a 1W resistor - double it at least for a margin of safety. So long as you have ~100mA, you'll have more than enough current for any headphones.