Here is the final 3D PCB layout for the New Class A amplifier module. The New Amplifier module is on schedule for release around Mid April 2015. More updates to follow very soon.
The new Class A module has electronic voltage regulation for the Input-VAS stages, DC Servo for less than 1mv DC offset, Baker clamps for perfect high frequency clipping behavior and 4 position DIP switch selection for 9dB of gain adjustment starting at around 27dB down to 18dB of Global Gain.
The PCB has been designed around the NXV500L form factor and the 4 main output devices have the same positions as the NXV500L module, so for those that already have the 500L or R2 module and want to try out the Class A module, the new Class A module is a practical drop in replacement, with exception to a power supply replacement or reconfigure to suit the Class A module requirements.
With 4 single die lateral MOSFETs on board this module can deliver just over 20 watts in Pure Class A into 8 and 4 ohm loads. With Dual Die Laterals installed this could be almost doubled in power output if you are looking for a bit more power output. Please let me know if any of you would be interested in the higher powered version of this amplifier module?
The Input-VAS stage supply requires +-30 volts to +-35 volts DC input from a raw DC supply to feed the on board power voltage regulators which the regulate this down to a very smooth and quiet +-26 VDC.
The Output stage just requires +-22VDC from a 160VA raw DC supply.
DC supply filtering for the output stage is recommended at 20,000uf per voltage rail as a starting point.
Input-VAS DC raw filtering is much less demanding at 3300uf per voltage rails as a good starting point.
The Class A module has been designed as a Mono Block amplifier in mind, so two separate power supplies as described above would be highly recommended for the best performance.
Total Harmonic Distortion for 1 watt is 0.003% 1khz and 10khz at 0.005% into 8 ohms loads
15 watts it is almost the same at 0.0035% 1khz and 0.0047% 10khz.
Signal to Noise Ratio is -103dB at 27dB Gain.
The PCB dimensions are 220mm x 51mm
In addition to the other features of this new Class A amplifier. There is an option to remotely switch the amplifier into Green Mode or if you like low current/low power dissipation standby mode.
For more information please contact me via info@holtonprecision audio.com
holtonprecisionaudio.com
Cheers Anthony
The new Class A module has electronic voltage regulation for the Input-VAS stages, DC Servo for less than 1mv DC offset, Baker clamps for perfect high frequency clipping behavior and 4 position DIP switch selection for 9dB of gain adjustment starting at around 27dB down to 18dB of Global Gain.
An externally hosted image should be here but it was not working when we last tested it.
The PCB has been designed around the NXV500L form factor and the 4 main output devices have the same positions as the NXV500L module, so for those that already have the 500L or R2 module and want to try out the Class A module, the new Class A module is a practical drop in replacement, with exception to a power supply replacement or reconfigure to suit the Class A module requirements.
With 4 single die lateral MOSFETs on board this module can deliver just over 20 watts in Pure Class A into 8 and 4 ohm loads. With Dual Die Laterals installed this could be almost doubled in power output if you are looking for a bit more power output. Please let me know if any of you would be interested in the higher powered version of this amplifier module?
The Input-VAS stage supply requires +-30 volts to +-35 volts DC input from a raw DC supply to feed the on board power voltage regulators which the regulate this down to a very smooth and quiet +-26 VDC.
The Output stage just requires +-22VDC from a 160VA raw DC supply.
DC supply filtering for the output stage is recommended at 20,000uf per voltage rail as a starting point.
Input-VAS DC raw filtering is much less demanding at 3300uf per voltage rails as a good starting point.
The Class A module has been designed as a Mono Block amplifier in mind, so two separate power supplies as described above would be highly recommended for the best performance.
Total Harmonic Distortion for 1 watt is 0.003% 1khz and 10khz at 0.005% into 8 ohms loads
15 watts it is almost the same at 0.0035% 1khz and 0.0047% 10khz.
Signal to Noise Ratio is -103dB at 27dB Gain.
The PCB dimensions are 220mm x 51mm
In addition to the other features of this new Class A amplifier. There is an option to remotely switch the amplifier into Green Mode or if you like low current/low power dissipation standby mode.
For more information please contact me via info@holtonprecision audio.com
holtonprecisionaudio.com
Cheers Anthony
Last edited:
Yes the input between 22-25vac would be good.
18vac would most likely load down a volt or so. This would make 18vac at 160va work very closely to the ideal.
Ideally what you are looking for is a dc level loaded of 22-23 volts for the output
Cheers Anthony
Hi ProtoCNC
The higher powered version would be 50 watts into 8 ohms.
So a little short of the 200 Watts Class A you are looking for.
Cheers Anthony
Hello Oyvind
The transformers needed for the 50 watt version would be as follows.
Output stage transformer 300VA core 2 x 22vac secondary windings.
Input stage transformer 80VA with 2 x 25vac secondary windings.
Heat sinks need to be able to do the following.
They would need to dissipate at least 100 watts per channel in heat.
If they have around 0.2/watt or better that would be a good match.
Cheers Anthony
Here is the latest photo of the new Class A amplifier module.
Cheers Anthony
An externally hosted image should be here but it was not working when we last tested it.
Cheers Anthony
In the 'news' section on Anthony's website;
''I am currently developing a 20 watt Push Pull Pure Class A amplifier module. This will feature a DC Current Servo Bias Generator which actively monitors the DC bias in the main output stage and locks it into place regardless of supply rail voltage and heat sink temperature. The Bias can be actively adjusted from as low as 50ma to as high as 5 amps.''
Anthony how do you compare it against your 500L?
When I first saw your new extreme power designs, I thought they are expensive, I thought your new 20w class A would be to expensive, but your price is like super good!
''I am currently developing a 20 watt Push Pull Pure Class A amplifier module. This will feature a DC Current Servo Bias Generator which actively monitors the DC bias in the main output stage and locks it into place regardless of supply rail voltage and heat sink temperature. The Bias can be actively adjusted from as low as 50ma to as high as 5 amps.''
Anthony how do you compare it against your 500L?
When I first saw your new extreme power designs, I thought they are expensive, I thought your new 20w class A would be to expensive, but your price is like super good!
Hi Ben
It is not an easy thing to compare the NXV500L to the new Class A module as the power output difference is very large. The Class A module is very much suited to the higher efficiency loudspeakers. If you have a pair of loudspeakers that are sub 88dB then the 20 watt Class A is really not for you. If your speakers are 90dB plus then the Class A module is a good match. The sound quality is very open, detailed and has excellent bass control just like the NXV500L, but at the same time has a much sharper imaging and a sweet sound signature that is unique to this module.
I hope this helps you Ben?
Cheers Anthony
''20 Watts RMS sine wave into 8 Ohms Per Channel with 1.7 amps bias''
If I bias the amplifier at 0.85A, will I get 10W RMS into 8 ohm?,
does it go into class AB, at higher levels, or is this strict class A
Can you tell us about; ''Amplifier can be switched into low power dissipation or standby mode''
If I bias the amplifier at 0.85A, will I get 10W RMS into 8 ohm?,
does it go into class AB, at higher levels, or is this strict class A
Can you tell us about; ''Amplifier can be switched into low power dissipation or standby mode''
It would be possible to use it on +-12v supply not a single +12v supply
Cheers Anthony
Hi Ben
For 10 watts a bias level of around 1 amp would be needed, beyond the 10 watts in Class A it will start working in Class AB.
As an example the 20 Watt Class A will double its power level into 4 ohms
but is well into Class AB at 40 watts. you can expect around 25% less power in Class A into a 4 ohm load with a 8 ohm load bias level as a rule of thumb.
The low dissipation mode switches another resistor into the bias network and presets the bias level down to around 300ma.
Cheers Anthony
Yes this is the same NXA20L module but with dual die laterals installed and some small changes to biasing for the higher power rating.
Cheers Anthony
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