100W Ultimate Fidelity Amplifier

[vargasmongo3435]

Mister Mile is it really difficult to set up bias on the A33 ?

Regards
Juan

 

[thiagomogi]

Apex A9 irfp240/irfp9240

credits PCB Sonal kunal
Mods Thiago

not tested

 

[sonal kunal]

Nice vork!
I like it!
Can you post Sprint file for this PCB?

Apex A9 on Sprint file

 

[apexaudio]

Mister Mile is it really difficult to set up bias on the A33 ?

Regards
Juan

You must ask alexmm or olafk, I never made A33,
Regards

 

[apexaudio]

credits PCB Sonal kunal
Mods Thiago

not tested

Thank you,
Regards

 

[olafk]

You must ask alexmm or olafk, I never made A33,
Regards

Hi , see post #3815.
I had no trouble to set the offset or bias. So I can't say anything about this. It was working from the very first moment. Sorry.

Regards Olaf

 

[olafk]

By the way, last weeks I have built the A9, A14, A17 and A33.
My Hitlist is:
- A14
- A9
- A17
- A33
But that's just my subjective opinion and only based on listening music. Now a lot of new amplifiers were built. I'm curious how you see it. Any experiences? What is your rating?

regards Olaf

 

[apexaudio]

By the way, last weeks I have built the A9, A14, A17 and A33.
My Hitlist is:
- A14
- A9
- A17
- A33
But that's just my subjective opinion and only based on listening music. Now a lot of new amplifiers were built. I'm curious how you see it. Any experiences? What is your rating?

regards Olaf

This is CFA hitlist, SR150 is new VFA for compare
Regards

 

[BC109]

Apex A9 on Sprint file

Thank you! 🙂

 

[vargasmongo3435]

You must ask alexmm or olafk, I never made A33,
Regards

ok I will ask them I'm really interesting on the A33 circuit 🙂 thanks I have the layout almost done from mister Alex MM PDF files I like it so much that I have to have it, really nice placement thanks Alex I'm gonna order a few for me yes !

Regards
Juan

 

[still4given]

Hi Guys,

I asked earlier but didn't get a definitive answer. To those who built the A33, what value pots did you use for P1 and P2?

Thanks, Terry

 

[apexaudio]

ok I will ask them I'm really interesting on the A33 circuit 🙂 thanks I have the layout almost done from mister Alex MM PDF files I like it so much that I have to have it, really nice placement thanks Alex I'm gonna order a few for me yes !

Regards
Juan

olafk answer you in post #4186

 

[vargasmongo3435]

ok thanks mister Mile I will check that now

Regards
Juan

 

[olafk]

Hi Guys,

I asked earlier but didn't get a definitive answer. To those who built the A33, what value pots did you use for P1 and P2?

Thanks, Terry

I used 500R and 5k.

regards Olaf

 

[still4given]

I used 500R and 5k.

regards Olaf

Thanks, that what I was planning to use.

Blessings, Terry

 

[cook77]

Hi Guys,

I asked earlier but didn't get a definitive answer. To those who built the A33, what value pots did you use for P1 and P2?

Thanks, Terry

4k7, recycled from an TV.

 

[alex mm]

4k7, recycled from an TV.

You must use multi turn potentiometer and for correct bias adjust 680 ohm resistor will be change to 1 Kohm value . Today I have tested A33 amplifier with +/-50V voltage rails and playing nice .Only first two MJE340 and MJE350 are warm ,so I attached a small heat sink .🙂
Regards,Alex

 

[still4given]

Hi Alex,

Please explain further. What value do you use for P1 and what value do you use for P2? May I assume the 680R you refer to is the one in the VBE multiplier?

Thanks, Terry

 

[cook77]

You must use multi turn potentiometer and for correct bias adjust 680 ohm resistor will be change to 1 Kohm value . Today I have tested A33 amplifier with +/-50V voltage rails and playing nice .Only first two MJE340 and MJE350 are warm ,so I attached a small heat sink .🙂
Regards,Alex

Instead of 680ohm+200ohm multiturn , I use 330 ohm and 1k ohm multiturn.
I had many of 1k multiturn ...
Thanks , Laur

 

[alex mm]

Hi Alex,

Please explain further. What value do you use for P1 and what value do you use for P2? May I assume the 680R you refer to is the one in the VBE multiplier?

Thanks, Terry

Hi Terry,
I used 200 ohm MT and 1K ohm resistor for bias .... and 4K7 MT for offset adjust.
Right ,680 ohm resistor it's from the VBE multiplier
Regards,Alex