100W Ultimate Fidelity Amplifier

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still4given

still4given

Member
Joined 2004
The volume pot is 50k linear. I added 5k6 resistors from sweep to ground to simulate log pot. The TB3 is out of phase. I bypassed it and things sound beautiful. With the TB3 in circuit the center is missing. I followed your layout. I can't tell on the schematic which pin are which on the pots but the layout looks correct. It sounds like one of the channels is inverted.
 
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adamart

Member
Joined 2015
TONE CONTROL

hello sir apex audio thanks for a kind reply my post of your speaker protect I appreciate sir, now i would like to ask if this APEX TB2 circuit can be compatible to your AX14 amp NX14 and NX16 amp as you design sir possible to use this as tone control?
 

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apexaudio

apexaudio

Member
Joined 2010
still4given said:
The volume pot is 50k linear. I added 5k6 resistors from sweep to ground to simulate log pot. The TB3 is out of phase. I bypassed it and things sound beautiful. With the TB3 in circuit the center is missing. I followed your layout. I can't tell on the schematic which pin are which on the pots but the layout looks correct. It sounds like one of the channels is inverted.
Click to expand...

TB3 is non inverting circuit... can you test it on scope?
 
still4given

still4given

Member
Joined 2004
apexaudio said:
TB3 is non inverting circuit... can you test it on scope?
Click to expand...

Hi Mile,

OK, I put it on the scope and it is not inverting but there is still something going on. Volume drops when the balance control is in the center position. If I bypass the TB3 the volume is noticeably louder. I tried substituting OPA2134 opamps and there is a slight improvement but still the bypassed signal is far superior. Any idea why centering the balance pot is causing the drop in volume?

Thanks, Terry
 
apexaudio

apexaudio

Member
Joined 2010
still4given said:
Hi Mile,

OK, I put it on the scope and it is not inverting but there is still something going on. Volume drops when the balance control is in the center position. If I bypass the TB3 the volume is noticeably louder. I tried substituting OPA2134 opamps and there is a slight improvement but still the bypassed signal is far superior. Any idea why centering the balance pot is causing the drop in volume?

Thanks, Terry
Click to expand...

Remove balance pot and add jumpers...
 

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AndrewT

R.I.P.
Joined 2004
Landoctor said:
I have a nice chassis and PSU parts that I would like to use (if possible) to build an A40.
The 1200va toroids I have are 60-0-60, which gives me ~80v DC rails after rectification and CLCRC filtering. Is there anyway to use this to power an A40?

Next, has anyone done a dual mono setup (layout and pcbs) for this amp?

Thanks for your time,
Donovan
Click to expand...
I just finished rewinding dual 57Vac transformer before I went on holiday.
I split both 57Vac into two to give me a four secondary of roughly 28.5Vac (~30Vac open circuit). I then added on ~20Turns to each of those windings to give me quad 34.5Vac to power a 100W+100W into 8+8ohms amplifiers.
You could aim for quad 35Vac or quad 40Vac for a big stereo amplifier with isolated channels.
Your big 1200VA may be around 1.5Turns per Volt, so you will not need many extra turns.
The 10A windings probably use 2mm diam wire. That is pretty thick to wind on by hand. Consider using bifilar 1.4mm wire for the extra turns.
 
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