AUDIO CRAFT AC-300C/AC-400C
AC-300C : ¥ 29,800 (around 1975)
AC-400C : ¥ 32,800 (around 1975)
Commentary
Tone arm improved based on AC-300/AC-400.
AC-300C is 35 cm type and AC-400C is 40 cm type.
A one point support system with a jewel with spring suspension is adopted for the rotary bearing part, and an oil dump system with moderate oil control by an orthodox semi-spherical damping material is adopted.
As a result, harmful resonance is suppressed, the resonance of the tone arm is low, and the reproducibility of the low-frequency range is excellent.
One point support Oil dump type tone type tone arm has low sensitivity due to its mechanism, it is considered unsuitable for cartridges with high compliance and light needle pressure design. The AC-300C/AC-400C equipped with an oil damping adjustment mechanism to solve this problem. It can be switched to the best damping position according to the characteristics and needle pressure of the cartridge to be used.
In this mechanism, the gap between the brake ball and the oil cup can be precisely adjusted by the precision of the rotating bearings, so that the amount of oil damping can be varied. This eliminates the by sight and manual adjustment that was a drawback of the conventional oil-dump-type tone arm. The adjustment knob can be continuously adjusted to 3 positions (Light-Normal-Heavy) for each rotation, so that the performance of the cartridge used can be demonstrated.
In addition, the damping oil is designed so that it can be easily replaced by removing the three screws. In addition, the standard damping oil with a viscosity unit of 200000 cs was used, and as an option, low viscosity (100,000 cs) and high viscosity (300000 cs) were available.
Equipped with an inside four scan seller.
With the one point support system, it was said that it was difficult to add an inside for scan seller in order to maintain the lateral balance, but with the AC-300C/AC-400C, the cancellation point is taken at the position where the lateral balance is maintained over the entire record surface near the suspension axis center, ensuring stable operation and improving tracing ability.
The lateral balancer uses a neutral lateral balance (NLB) system built into the rear of the center block.
In this system, the built-in weight slides by rotating the left and right small knobs, and accurate lateral balance on the arm axis is possible. The amount of sliding is locked to locked by approximately nine rotations of the knob, and quick adjustment is possible.
In addition, with the attached lateral weight, the balance range can be sufficiently wide, and with the attached lateral balance gauge, the lateral balance can be monitored more reliably.
The head shell is equipped with 2-lock pin type AS-2Plus as standard.
Compared with the conventional single-pin system, it locks securely to the tone arm and there is no mounting looseness. In addition, it has a robust structure made of 2.8 mm thick light alloy material with high rigidity and sufficient suppression of resonance.
The fingers are integrally molded to eliminate harmful resonance, and the contacts and lead pins are gold-plated.
The weight assembly adopts a double-weight mechanism.
The needle pressure is adjusted accurately by rotating the linear slide of the main weight and the Lee Ka-eun tarring. The indicated value is 0 ~ 3g, 0.25g step direct reading type.
By adopting this double-weight mechanism, the total length of the weight assembly can be adjusted to 28 ~ 34 mm for AC-300C and 28 ~ 39 mm for AC-400C. It can be adjusted to the position closer to the movable shaft, and the stability of the arm operation is improved.
The arm lifter has a unique structure and is highly reliable.
The oil dump cylinder has a structure that prevents oil leakage even after many years of use, and the height of the lifter can be adjusted by rotating the ring at the cylinder head in response to the damping adjustment mechanism.
All contacts from the lead pin of the head shell to the pin plug of the output cord are gold-plated to prevent contact failure due to corrosion, etc.
In addition, a low-dose type (33pF/m) is used for the output cord, and the plug socket connected to the tone arm is also a new type that ensures more reliable contact.
A large lock nut with a length of 25 mm is used to attach the tone arm to the monitor board, which is one element for suppressing resonance.
There were plenty of optional parts.
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Model Rating
| Type | Tone arm | |||||||||||||||||||
| Model Name | AC-300C | AC-400C | ||||||||||||||||||
| Method | One point support oil dump | |||||||||||||||||||
| Total Length | 333mm | 379mm | ||||||||||||||||||
| Effective length | 237mm | 283mm | ||||||||||||||||||
| Overhang | 15mm | 13mm | ||||||||||||||||||
| Distance of turntable center from bearing center | 222mm | 270mm | ||||||||||||||||||
| Tracking error | 0.21 ゜ / cm or less | 0.13 ゜ / cm or less | ||||||||||||||||||
| Maximum Rear Length | 85mm | 90mm | ||||||||||||||||||
| Needle pressure application system | 0 ~ 3g (0.25g Step), Direct Reading Type | |||||||||||||||||||
| Range of cartridge use | 3.5 ~ 15g | |||||||||||||||||||
| Lateral balance | NLB method | |||||||||||||||||||
| Arm lifter | Oil dump type (with height adjustment device) | |||||||||||||||||||
| Inside for scan seller | Standard Equipment | |||||||||||||||||||
| Head shell | AS-2Plus | |||||||||||||||||||
| Sold Separately | Head shell
Weight
Wood screw fixing arm base
Damping spare oil
Inside Four Scan Seller Kit
Large lock nut
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