The NFB-11 applies the newest ESS high-end Sabre32 DA chip ES9028 which can support up to 32Bit/384KHz input .
To be achieve the best performance of ES9028 , must work in current output model, in voltage output model, there is -12DB THD+N worst .
The standard current model design usually need 3 amps (OPA) , the first amp implement I/V conversion, conversion the ES9028 output current signal to voltage signal .
The second amp is the difference amp, conversion the balance signal to single-ended signal and implement the low pass analog filter , then through volume control feed to the third amp, the headphone amp .
Every amp usually have two gain stages built in so the ES9028 signal must through total 6 gain stages arrive the output stages .
The NFB-11 applies Non-feedback ACSS design. The ES9028 feed to the ACSS circuit without any OPAs .
The ACSS circuit naturally working in current model and have design difference current input , it can process the I/V conversion, signal difference and headphone amp in current model in one ACSS amp . And this ACSS amp only have one current gain stage , the ES9028 output signal only through one stage can arrive the output stages .
The shortest signal journey can reproduce the best detail and dynamic, and almost without sound coloration , It can show the real performance of the ES9028 .
So our ACSS design is the best combo with ES9028 achieve the best performance .
Upside in the picture is the standard ES9028 headphone amp design. The bottom is the NFB-11 design .
The ACSS also is a non-feedback technology made with fully discrete amplifiers. Most people know the global feedback design can offer better specs in test measurements, and non-feedback can't do well in test measurements but can offer better sound for the human's ears. Here is a conflict of the classic circuits.
But the ACSS opens a new field, it can offer a least coloration sound which is more neutral with very low distortion and high linearity. So it can retain the dynamics, detail and neutral sound but not sound bright or harsh.
The output buffers are Non-feedback. For low impedance, we applied a diamond output stage which is quite less colored than most conventional circuits. It built with 4 pcs 20W (in total 80W) high speed Toshiba transistors, no matter to drive the most headphones.
The DAC is without couple caps to avoid coloration. There are two OPAs built in as the DC serve to keep the DC offset .
The 32bit / 384K USB interface outputs a I2S signal to ES9028 .
Fully Discrete ACSS headphone amp.
NFB-11 applies the excellent DA chip ES9028 and excellent analog output stages, but these are not the only keys of the best sound. The power supply is most important. Even applying the best DA chip and the best amp, if matched to a average power supply, the total sound may still be average or sound musical but can't be neutral and detailed. That is why it is easy to find hi-end grade gears maybe without the best chips , but with plenteous dedicated DC supply circuits.
The NFB-11 uses 6 groups of high-quality PSU with dedicated DC supply . Digital and analog voltages each have separately isolated internal power regulations.
The digital power had 4 groups high spend PSU group double stages PSUs , can avoid the interrupt from the power cause the jitter increase, offer the blacker back stage and much pure sound. In ago, double stages PSUs only applied in our USD1500+ products.
This massive power supplies design usually only applied in the USD1000+ products .
The analog power supply is more important for sound reproduce, in NFB-11, the +15V and -15V for the analog output stages are high speed Discrete PSU. They can offer pure and quick power supply for driving the headphone exactly. The high voltage power supply can drive most headphone from 15 to 600 ohms as well.
Strong power supply.
About volume in ACSS circuits:
For a headphone amp, the volume control is very important.
In ACSS, it is placed at the ACSS modules output, where the output is the current signal, not the voltage signal. The volume control is I/V conversion, and the volume depends on the current (I) conversion to the voltage (V). (Like D/A chips output I/V conversion)
As you can see, ACSS circuits have no gain, as it is a completely different circuit.
The sound quality benefits from I/V conversion volume control. Mark Levinson also knows that current volume control has great benefits, so in their Top End preamp NO.32 volume control, they use many components to change the signal to current signal (I), then through the R-2R network to control the volume, and then change back to voltage signal (V) again. But NFB-11 is simply a more complete work in terms of the current signal, and technically, it is superior to conventional technology.
ALPS 27 volume pot
1 % exact match transistors
Audio-gd the manufacturer burn in all equipment for a period of more than 100 hours, the equipment is quality control checked and tested several times before dispatch.
The repair warranty by Audio-gd the manufacturer and the product support by the Locally Appointed Agent does not cover user abuse, improper use of the equipment, electrical surges, electrical transients, lightening damage, use of computer ports USB3.0 or higher and damage to receivers due to unshielded and non-standard USB cabling.
The equipment supplied to the Locally Appointed Agent from Audio-gd the manufacturer is for use within the boarders of the Republic of South Africa and must be mains earthed via the power cable supplied by Audio-gd the manufacturer and fitted the a South African 3 pin mains plug.
First year repair warranty:
Should the equipment have any manufacturing defects which is not caused by the user, the customer is to ship back the equipment to Audio-gd the manufacturer or the Locally Appointed Agent for assessment and inspection. The customer must submit the shipping bill following which we will reimburse the amount to customer.
Note: Audio-gd the manufacturer or the Locally Appointed Agent will only refund shipping cost equal to what the customer initially paid for shipping when placing the order. Audio-gd the manufacturer or the Locally Appointed Agent will repair the defective product at no charge and return ship the equipment to the customer.
1, Should the equipment be found to not to be faulty on assessment and inspection by Audio-gd the manufacturer or by the Local Appointed Agent but the customer has return shipped the equipment, Audio-gd the manufacturer or the Locally Appointed Agent will not cover the shipping cost, The return shipping will be for the customers account.
2, Should the customer notify Audio-gd the manufacturer or the Locally Appointed Agent within 7 days of receiving the equipment and report the equipment faulty. Audio-gd the manufacturer will cover the return shipping cost of the equipment to China and will return ship a new replacement unit to the customer.
3, Should the customer notify Audio-gd the manufacturer or the Locally Appointed Agent within 7 days of receiving the equipment, and the equipment found not to be faulty by assessment and inspection by Audio-gd the manufacturer or by the Locally Appointed Agent the unit will be return shipped to the customer, the return shipping costs are for the customers account which must be paid in full prior to dispatch.
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5, Audio-gd the manufacturer or the Locally appointed Agent will assess, inspect and test the equipment based on a world standard, we will report the status of the assessment and inspection to customer.
After the completion of first year repair guarantee :
Should the equipment have any faults or manufacturing defects which is not caused by the user, the shipping will be for the customers account (to and from Audio-gd the manufacturer or via the Locally Appointed Agent), while Audio-gd the manufacturer or the Locally Appointed Agent will repair the product at no additional labour cost.
User inflicted problem repair guarantee:
Should the assessment and inspection reveal that the equipment has been damaged by the user, the customer will be quoted for the repair costs and will be charged for the return shipping costs by Audio-gd the manufacturer via the Locally Appointed Agent.
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