100W Ultimate Fidelity Amplifier

[apexaudio]

There is some hole under the heat sink and fan is blowing outside the chasis
To take out hot air inside the case and its realy help for cooling the amp

Nice work,
Regards

 

[maxwell007]

Nice work, yes R8 (560R) affect total gain, if you increase value to 1k2 it will reduce gain.
Regards

so which schematic is correct ? value of R2,R8 is reversed

 

[AndrewT]

I have question about gain.. Is It R8 value, which affects total gain? When I will Increase value from 560R let's say to 1k2? Can someone explain me, how can I find feedback resistor? 🙂 Next question is about maximum PSU voltages, and bias for all apex amp. Is it possible to make some table, because I think its still repeated question.. Thank you...

Max, that input stage uses positive feedback. It is bootstrapped to increase the AC input impedance.

Be very careful with changing any of the component values around the input stage.

Positive feedback is very sensitive to tiny changes.

 

[apexaudio]

so which schematic is correct ? value of R2,R8 is reversed

R2 22k and R8 560R is correct values.

 

[AndrewT]

Could someone ask the Moderators to delete the sch with the values transposed, to avoid confusion for some reader that picks the wrong sch.

 

[Cortez]

There is the report post icon, you could use that.

 

[AndrewT]

It is not my posts and not my design.

It should be the responsibility of either the amplifier Designer or the errant poster to remove "WRONG" schematics.

Otherwise anyone could ask to have stuff removed that they did not agree with or saw as competition to their own designs/philosophy.

 

[maxwell007]

Max, that input stage uses positive feedback. It is bootstrapped to increase the AC input impedance.

Be very careful with changing any of the component values around the input stage.

Positive feedback is very sensitive to tiny changes.

my problem is, that opened input produce adible hum.. its better, when i connect some input device, but hum is still audible...from my point of view is input too sensitive...any other suggestions?

 

[vargasmongo3435]

my problem is, that opened input produce adible hum.. its better, when i connect some input device, but hum is still audible...from my point of view is input too sensitive...any other suggestions?

did you place a GND wire from the star GND of the power supply to the -NEG input ?

Regards
Juan

 

[maxwell007]

I just tested if it´s work...

 

[still4given]

Do you have those wires soldered to the lugs on the PSU or just twisted. I have had ground hum issues before just because I had a slightly loose spade connector on the ground lug. Remember, the ground wire is carrying the return for both rails.

 

[maxwell007]

just when you bring near a finger to the input power components and noise starts to rise.. i think is not grounding problem

 

[vargasmongo3435]

maybe I know what it is, try jumped this resistor with a wire or alligator clips
I think is a mistake from me.

Regards
Juan

 

[apexaudio]

Hello Apexaudio
I build A23 PSU +/- 56v, 3 pairs
So circuit to change anything?
Thanks a lot

No changes.
Regards

 

[AndrewT]

post4633 still shows the wrong values with APEX name attached.

Is this acceptable?

 

[maxwell007]

I'd like try to replace in AX14 all BC's with 2N5551 / 2N5401 transistors , because I think there is lot of dubious quality BC's... Mile, do you think that is possible? Or what is the reason for BC´s usage?

 

[apexaudio]

I'd like try to replace in AX14 all BC's with 2N5551 / 2N5401 transistors , because I think there is lot of dubious quality BC's... Mile, do you think that is possible? Or what is the reason for BC´s usage?

You can use 2N5401 and 2N5551 or 2N3905 and 2N3906 instead BC547 and BC557.
Regards

 

[still4given]

Remember the pins are reversed. You will need to invert them.

 

[wiljj78]

I like the performance of this protect, but it works only in rails supply up to 40VAC.
What are the changes if i want to use separate 18-0-18 up to 24-0-24 VAC in order to use in higher rails power amp?

 

[andrewlebon]

Hi Wiljj78
greetings does this protector have SHORT CIRCUIT protection
warm regards
Andrew