[faileas]

I'm considering building a Szkeres amp, and am currently looking up what i'll need. Apparently the original design used the IRF510, which is out of production, but the instructions/addidium suggests that the IRF610 is a suitable replacement - has anyone built the amp with one, and do i need to make any mods?
 
I'll also need a PSU for testing - would a 16v 4.5 amp regulated laptop power supply do? I might look at a fancier one later, but i'd just like to be able to test as a go along without yet another variable to worry about, and i have one lying around, alternately can i use the 12V output from a desktop PSU?.

 

[Avro_Arrow]

IRF510 is still very common.
 
See the Single ended class "A" design thread...

 

[digger945]

Yep, 510 is available many places, including Digikey in TO-220.
 
Which one of the circuits were you considering? May I suggest you consider incorporating the LM317 CCS or allowing for it in the future.
 
The laptop supply will prolly work so long as you don't overdo it with the opamp supplies.

 

[dsavitsk]

Difference between the 510 and 610 in this design is minimal.  610 has slightly lower gate capacitance, though neither is that high, and 510 has slightly higher Gm, though again, the difference is pretty insignificant.  The Zout of the 610 may be about 0.5 Ohms higher than the 510.
 
The 16V ps should be fine.  If it's noisy, you might want a regulator.

 

[faileas]

To start with, i'll be using the plain vanilla design in the main article. I'd rather use the 610 since i can get it locally from my regular sources (RS has a retail store in the mall i get my usual random junk from) - i'll prolly try the version with the LM317 if i get this working.

 

[Tomo]

?
http://diyaudioprojects.com/Solid/IRF610-Class-A-Headphone-Amp/
?
 
You would probably want to fiddle with the gate voltage and look at the voltage across 20 ohms (R4). I am running 15V PSU doing 3.7~8V which is giving me 200mA per channel. I think that should give me Vgs = 3.7~8V. (Gate voltage to ground is 7.5V)
 
Prolly you guys should come up with a better Mosfet alternative.

 

[faileas]

Thats about what i was thinking. I have another question though - i'm looking through a local supplier for LM317s, and they have a whole bunch of differently priced chips with the same rough specs am i ok getting the cheapest through hole one, or should i be looking at them more closely?
 
EDIT: one's a 50 pack... oops

 

[digger945]

Wrt the 317 look at the data sheets for the device in question and make sure it will handle the current. Some of the different desidnations refer only to the package, TO220 or SMD etc.





In my previous post, I did not mean to imply that the 317 ccs was better, just a different way. A MOSFET is prefered by many here. I have tinkered around quite a bit with a 24v aikido that uses the same se cap coupled output as this one, and even uses the 317 in both ccs and output positions in one example.





I am sure you will be very pleased with the sound of this amp, and look forward to your impressions when you are finally listening to it.

EDIT: From the link you gave, I would choose a TO-220 device with 1.5A or 1500mA to safely cover the current required by this design, and more easily allow you to affix heatsinking if needed.

 

[Tomo]

Quote:

Thats about what i was thinking. I have another question though - i'm looking through a local supplier for LM317s, and they have a whole bunch of differently priced chips with the same rough specs am i ok getting the cheapest through hole one, or should i be looking at them more closely?
 
EDIT: one's a 50 pack... oops

 
I wouldn't worry about suppliers; just find ones you can get in small quantities. Get TO-220(AB) ones so you can attach a heatsink. When you do make sure you get Mica bushing for heatsink mounting. Those tabs are electronically hot and you must insulate if you don't use it in the circuits. (This applies to MOSFETs too)
 
I kinda got fed up with CCS and slapped on a really expensive (but probably not better) resistor for R4.
 
Sometimes less is better. Most time you can spend on listening to music. ... But then if you are a self-respecting audiophile, you shouldn't listen to me. Only thing I can say is to use a modest amount of money for the output couple caps, so you can avoid having to bypass it with film caps. (But you may have to anyway. Besides, film caps at 0.01uF range is fairly cheap.)