All of our amplifiers not only have high outputs, they also have extension filters adjustable for both frequency and damping factor. The huge filter caps (for a total of 28,800uF) ensure a large energy reservoir to supply a more stable power to the power amplifier. The smallest is the A300 with output of 300WRMS at 4ohms (available in August). A370 is rated at 370WRMS at 4ohms. And H500 (Available in Oct) is rated as 500WRMS at 4ohms. All of them are audiophile oriented. With ultra low distortion and no electrolytic capacitors on the signal or feedback paths, these Special Edition amplifiers deliver a sound quality comparable to more expensive component power amplifiers. All amplifiers feature relay-less circuit design to ensure the highest damping factor.

We also offer 3 functional models. SE amplifiers are for those who use bass management in their HT receivers. PEQ amplifiers offer defeatable one-band parametric equalization (PEQ) to tackle the most serious room mode. XLR amplifiers offer XLR input and a master control for daisy chain of multiple subwoofer amplifiers under the control of one master amplifier. Here is the comparison chart. All of them have the same cut-out dimenson to be interchangable.

Nonservo Model	A300-SE	A370-XLR	A370-PEQ
Output Power (4ohms)	300W RMS	370W RMS	370W RMS
Input Type	Speaker/RCA	Speaker/RCA/Balanced	Speaker/RCA
Master control	NO	YES	NO
Parametric EQ	NO	NO	Defeatable one-band
Power amp inputs	MOSFETs	MOSFETs	MOSFETs
Setup for	HT receiver	w/ or wo/ HT receiver	w/ or wo/ HT receiver
Subwoofer roll-off	12 dB	12/24 dB selectable	12/24 dB selectable
Power filter caps	4x80V/6800uF	4x100V/6800uF	4x100V/6800uF
Warranty	2yr	2yr	2yr
Sale price	$219	$259	$259
Control Layout

Download manuals | A350 SE | A350 basic | A250 basic

If you plan to build a sealed box and already bought the driver, we strongly recommend the Linkwitz Transform add-on board. Others may recommend using rumble filter or parametric EQ to extend the bass response. However, the bass extension obtained is never as as smooth as the one with Linkwitz transform circuit. For those who haven't bought the driver, we recommend the servo sub option.

Crossover note on all models

SE amplifiers are designed for use with home theater (HT) receivers. The users need to use the bass managment on the receiver. The 12db/oct low pass filter on SE amplifiers is used as a fine tuning knob to adjust the overlap between the sub and the front speakes. PEQ and XLR amplifiers have 12db-24db/oct selectable low pass filter to use with or without an HT receiver. The 24db/oct on them is implemented as 12db/oct adjustable via a knob plus a 12db/oct fixed at either 50hz or 80hz (two switch positions).

Features

Our amplifiers feature a modular design that allows one to later convert the nonservo amplifier to a servo one to use with our servo drivers.

These amplifiers are showcases of our pursue of perfection for those who seek more than just basic functions. The op amps used here are audiophile grade OPA2134 and TL072. OPA2134's are used in the high pass section (the one for front speakers filtering). On the subwoofer signal path, the op amps are mixtures of OPA2134 and TL072. The reason for us to use TL072 is for its richer bass sound. At half of full output rating, the distortion is less than 0.01%. In addition, similar to the A370 servo amps, there is no electrolytic capacitors on the signal and feedback paths. When ordering these amps, please select the model based on the needed feature and mostly depends on if you will use it with a home theater receiver or a conventional stereo setup. The reason is that for stereo setup, one needs to have 24 dB/oct roll off on the subwoofer Low pass filter, which requires either A370PEQ or A370XLR. On the other hand, to use with a home theater receiver, we really need only 12 dB/oct. So all three models can be used.. Here is a summary of features:

1. Harmonic distortion is less 0.01% at 200WRMS @4ohms (-3 dB from full output). This amp can surely qualify as an ultra low distortion amp.
2. All OP amps on the signal paths are OPA2134 and TL072 for better sound quality (SQ) and richer bass sound.
3. MOSFET transistors for power amp's input stage for a more smooth sound.
4. 370W RMS@4ohm <0.1%THD, 245W RMS @8ohm<0.1% THD. Class A/B operation. Bigger power always bring in better bass, simply they use bigger transformer (ours is 600VA), bigger filter cap (ours is 4 of 6800uF/100V), and bigger heat sink (ours is one piece 3/16" thick back plate/heat sink construction for better heat transfer and rigid structure). Power rating is tested for 4 continuous minutes.
5. A defeatable extension filter with separate frequency and damping control. The extension filter can be bypass with 14 Hz and high damping setting. Frequency is adjustable between 14, 20 and 28 Hz. Damping factor is adjustable between high damping (Q=0.6, or bessel filter), medium damping (Q=1.07, or 1.5 dB boost Chebyshev), low damping (Q=1.33, or 3 dB boost Chebyshev). There are a total of 9 settings available. You can use this filter to boost the bottom end or do minor correction for room response. In case you don't know, our competitor has a 6 dB boost at 30 Hz which cannot be defeated. To defeat that, you have to unmount the circuit board and do some soldering, voiding the warranty if there is one. Incorrect rumble filter not only makes the bass sound boomy, it can even bottom out the woofer.
6. Damping factor: 160 @ 4ohms. (Note: damping factor is speaker wires dominated. Without speaker wires, the native damping factor is >800).
7. Signal to noise ratio: better than 107 dB (A-weighted).
8. Input impedance: 30k ohms.
9. Air tight by designed. No need for a back cover or separate chamber. It will give you an extra 0.15 cu ft enclosure net volume compared with those with back covers.
10. Auto ON/OFF on left channel input.
11. Accept both high level (from speaker) and low level (from preamp or processor) inputs.
12. Fixed high pass line level output for satellite speakers.
13. Continuous phase adjustment (0-180) and low pass filter adjustment (25-120 Hz).
14. Gold plated connectors.
15. Build-in thermal and short circuit protection circuitry.
16. The phase control is vastly improved so that it has better control in the non-HT setup.
17. Subwoofer crossover adjustable range is increased to 25-120 Hz for more flexibility.
18. HP filters for satellite is modified to -3 dB@100 Hz with Q=0.6.
    

This amp also carries a 2yr warranty against defects (does not cover abuse or installation errors). All other features such as protection circuits are same as regular amps.

• Dimension: (W)10-3/8"x(H)12-7/16"x(D)4".
• Cutout Dimension: (W) 9 1/8" x (H) 11 1/8".
• Big power transformer with 650W max input power. Net weight is 17 lb.

For international shipping, please check out order page.

	Description (for sealed/vented subwoofers)	Price
	A300SE nonservo amplifier (300WRMS available in August)	$219
	A370PEQ nonservo amplifier	$259
	A370XLR nonservo amplifier	$259

We alo have versions specific designed for general OB subwoofers with a build-in shelving circuit.

	Description (for OB subwoofers)	Price
	A370PEQ OB nonservo amplifier	$269
	A370XLR OB nonservo amplifier	$269