100W Ultimate Fidelity Amplifier

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smartx21

smartx21

Member
Joined 2010
Hi, Mr. Mile,
I apologize for my simplicity, but where can I find the rail values that are suitable for these amps (AX14, NX14)? In your schematics only appear a reference to POS and NEG connections to the PSU.
I've got some samples of N-MOS transistors, and I would like to try the NX14 option.
Thanks for your help.
All the best,
Max.
 
apexaudio

apexaudio

Member
Joined 2010
smartx21 said:
Hi, Mr. Mile,
I apologize for my simplicity, but where can I find the rail values that are suitable for these amps (AX14, NX14)? In your schematics only appear a reference to POS and NEG connections to the PSU.
I've got some samples of N-MOS transistors, and I would like to try the NX14 option.
Thanks for your help.
All the best,
Max.
Click to expand...
Amp will work with any rail voltage start +/-24V up to +/-56V DC.
Regards
 
apexaudio

apexaudio

Member
Joined 2010
smartx21 said:
Hi, Mr. Mile,
I apologize for my simplicity, but where can I find the rail values that are suitable for these amps (AX14, NX14)? In your schematics only appear a reference to POS and NEG connections to the PSU.
I've got some samples of N-MOS transistors, and I would like to try the NX14 option.
Thanks for your help.
All the best,
Max.
Click to expand...
If you build NX14, please post pictures and comment, becouse many people like QUASI NMOS amps.
Regards
 
apexaudio

apexaudio

Member
Joined 2010
Useing this terminal it's easy to connect amp to psu with 2,5mm wire.
 

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apexaudio

apexaudio

Member
Joined 2010
sng001 said:
I added two rail bypass capacitors (1.5uF X7R ceramic) closer to the output transisitors.

I found the treble is a bit harsh if I removed the input capacitor (C1).

I put back C1 & that removes the harshness.

I replaced C1 (10uF Bipolar electro) with 10uF film capacitor & the high frequencies is a bit smoother.

I left the BC560C installed at Q1 & Q2 as they gives lower Output DC offset compared with the 2N5401.

Cheers, Stanley
Click to expand...
C1 can be replaced with 1uF or 2,2uF film capacitor. With +/-45V DC rail voltage BC560C is better choice.
Regards
 

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H

hamub

Member
Joined 2009
Transformer

godfrey said:
Aha! A better question might be "What's wrong with current sources?".

With a simple current source like Q3 in this circuit, the collector-base capacitance is effectively in parallel with the current source, so it's dynamic impedance will reduce at high frequencies.

Perhaps this is why Mile put a 10K resistor in series with it - to keep the impedance high at high frequencies.

Also - The transistor's Hfe, Vbe and Ccb all vary non-linearly with collector voltage, so the current will vary with voltage and will be distorted.

Replacing the entire current source with e.g. a 220K resistor connected to a well regulated +300V supply would eliminate the distortion and high-frequency problems.

For the input stage, these aren't serious problems though, because there is very little voltage swing on the current source and the LTP has good rejection anyway.

The second stage is much more important, but here a Baxandall super-pair has been used for the current source (and the VAS) to eliminate all the base-current distortions.

btw: Neither of the current sources in this circuit will hurt propagation delay, with or without a bit of capacitance.
-----------------------------------------------
Sorry for the hijack, Mile.

This looks like a really nice circuit. What rail voltage or power is it intended for?

Cheers - Godfrey
Click to expand...

Godfrey i see you are in Cape Town. Any idea where i can get heat sinks & transformers in Kaapstad?
 
apexaudio

apexaudio

Member
Joined 2010
smartx21 said:
Hi, Mr. Mile,
I apologize for my simplicity, but where can I find the rail values that are suitable for these amps (AX14, NX14)? In your schematics only appear a reference to POS and NEG connections to the PSU.
I've got some samples of N-MOS transistors, and I would like to try the NX14 option.
Thanks for your help.
All the best,
Max.
Click to expand...

Go to post #209,
Regards
 
apexaudio

apexaudio

Member
Joined 2010
Ax14, fx14, nx14

There is all version of 'Ultimate Fidelity Amp'. There is D14 with darllingtons, and other versions with more than single output pair, but this is most popular, and you can see all adventage of useing Baxandall super pair in VAS and CCS.
Regards
 

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S

sng001

Member
Joined 2009
Power Supply

apexaudio said:
C1 can be replaced with 1uF or 2,2uF film capacitor. With +/-45V DC rail voltage BC560C is better choice.
Regards
Click to expand...

Hi Apex,

I am using +/- 42V rail, so I left the BC560C as they are.

I borrowed the big power supply board from my subwoofer with 8x 8200uF filter capacitors and one 25A bridge rectifier per channel to test the AX14.

I have since build two power supply boards with 4x Nichicon 8200uF filter capacitors & 8x On-Semi MUR1520 fast diodes per channel. Surprisingly the AX14 sound better with less filter caps - the amp sound faster & more detailed.

Some comment about the sonics of AX14:
My speaker is quite old - Magnat All ribbon 6p and I would say its treble is vavid. My source is a Pioneer BDP-51 Blu-ray player & a modified Squeezebox 3. I don't have an active pre-amp and the Pioneer is a very competent CD player with Wolfson WM8740 DAC built-in.

I am comparing the AX14 with Mike Bittner's SymAsym v5.3 and Wahab's AWB50.

All three are good amplifiers - I would rate SymAsym the best on my setup - it has got slightly stronger bass & a bit more detailed. AX14 is at close second place and I have to do back-to-back comparison to pick the difference. The SymAsym got its own sonic signature and AX14 is more natural or flat. The result may be different with another setup - YMMV.

Cheers, Stanley
 

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apexaudio

apexaudio

Member
Joined 2010
sng001 said:
Hi Apex,

I am using +/- 42V rail, so I left the BC560C as they are.

I borrowed the big power supply board from my subwoofer with 8x 8200uF filter capacitors and one 25A bridge rectifier per channel to test the AX14.

I have since build two power supply boards with 4x Nichicon 8200uF filter capacitors & 8x On-Semi MUR1520 fast diodes per channel. Surprisingly the AX14 sound better with less filter caps - the amp sound faster & more detailed.

Some comment about the sonics of AX14:
My speaker is quite old - Magnat All ribbon 6p and I would say its treble is vavid. My source is a Pioneer BDP-51 Blu-ray player & a modified Squeezebox 3. I don't have an active pre-amp and the Pioneer is a very competent CD player with Wolfson WM8740 DAC built-in.

I am comparing the AX14 with Mike Bittner's SymAsym v5.3 and Wahab's AWB50.

All three are good amplifiers - I would rate SymAsym the best on my setup - it has got slightly stronger bass & a bit more detailed. AX14 is at close second place and I have to do back-to-back comparison to pick the difference. The SymAsym got its own sonic signature and AX14 is more natural or flat. The result may be different with another setup - YMMV.

Cheers, Stanley
Click to expand...

Thank's Stanley
Your comment is valuable for me. I use topology like SymAsym in my amp from thread: http://www.diyaudio.com/forums/solid-state/162081-dc-servo-mosfet-amplifier-8.html long time. Natural or flat sound from AX14 is important to me for test with many diferent speakers.
Regards
 
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