100W Ultimate Fidelity Amplifier

[still4given]

Nice work... replace C7 with 1000uF/16V instead 100uF/63V to improve 50hz square.
Regards

Thanks, you are correct. Here are new scope shots with the 1000uF 16V installed in C7.

 

[prasi]

Thanks, you are correct. Here are new scope shots with the 1000uF 16V installed in C7.

did you notice any difference in sound due to cap change?
reg
Prasi

 

[prasi]

did you notice any difference in sound due to cap change?
reg
Prasi

Just trying to understand amp behaviour in bass region. BTW, clipping profile looks as good as any amp.
Reg
Prasi

 

[still4given]

No, I couldn't hear any difference but it was clear on the scope. How much music has much 50hz content? Make no mistake, this is a fine sounding amp. Definitely worth building.

 

[thimios]

No, I couldn't hear any difference but it was clear on the scope. How much music has much 50hz content? Make no mistake, this is a fine sounding amp. Definitely worth building.

Terry i ask about bass responce because this range isn 't the good point for 1058,162
This is my experience.

 

[still4given]

Terry i ask about bass responce because this range isn 't the good point for 1058,162
This is my experience.

Strange, that has not been my experience. P101, VSSA, TubSuMo, Slewmaster mini and now FX8, all with great low end. This FX8 has some of the flattest 50hz square waves i have ever seen. There is a tad of overshoot in the higher frequencies. I used 100p per the schematic. Mile's layout seems to use 330p. I don't have those in stock so i stayed with the 100p. I'm not sure if that is the reason.

 

[sandeep kayarkar]

What is the max vdc for ax14?

 

[apexaudio]

Strange, that has not been my experience. P101, VSSA, TubSuMo, Slewmaster mini and now FX8, all with great low end. This FX8 has some of the flattest 50hz square waves i have ever seen. There is a tad of overshoot in the higher frequencies. I used 100p per the schematic. Mile's layout seems to use 330p. I don't have those in stock so i stayed with the 100p. I'm not sure if that is the reason.

Output inductor will remove overshoot,

 

[apexaudio]

What is the max vdc for ax14?

+/-55V DC

 

[ammel68]

I didn't have any BD139's so I used KSC3503E, KSA1381E. No sign of oscillation, very stable.

Mouser doesn't have the "E" version of the C3503, only the "D" version.
Can this be used without issues with the "E" version of the A1381?

Thanks...

 

[AndrewT]

I bought e from abroad in the hope of solving this in an NX.
Fraid I still have unmatched devices, because the overlap between the wide spread allowed in the specification means that the base currents still don't match.

 

[ammel68]

I bought e from abroad in the hope of solving this in an NX.
Fraid I still have unmatched devices, because the overlap between the wide spread allowed in the specification means that the base currents still don't match.

So you can not mix "D" and "E" versions?

 

[still4given]

So you can not mix "D" and "E" versions?

I think you can. NFB should take care of minor differences. I only matched the input pair. If I feel ambitious I will try it.

 

[Rick G]

Hi Terry,
If possible,can you post iron pdf's for your FX8.

Thanks
Rick

 

[still4given]

Here you go. BTW, I used Prasi's layout for my template. I want to give him the credit.

 

[Rick G]

Thank you, & Thanks to Prasi for making the Orig.

Rick

 

[prasi]

Here you go. BTW, I used Prasi's layout for my template. I want to give him the credit.

Rick

Cheers! .
reg
Prasi

 

[AndrewT]

So you can not mix "D" and "E" versions?

mixing the hFE results in a difference in base current when the devices pass the same emitter current.

That mismatch in hFE will happen whether the devices are both D, or both E, or from D & E.

It's the difference in base current that matters.

Will the circuit perform as well if the base currents are not closely matched?
The designer has not told us what effect on performance there would be if the base currents are not matched.

 

[Rick G]

How about 2N4923G/2N4920G as replacements for BD139/140. Mouser has them for $0.62 a piece.

 

[Dragan100]

How about 2N4923G/2N4920G as replacements for BD139/140. Mouser has them for $0.62 a piece.

OK, pretty close replacements, max 80V, 1A, 20W, h_fe cca 50 (BD139/140 - 10)