ACCESSORIES

GRADO proposes 5 accessories:

  • A phonograph preamplifier: PH1
  • A headphone amplifier RA1 (in 3 versions)
  • A “MINI” adaptor: 3.5mm male to 6mm (1/4”) female
  • A 15 foot headphone “EXTENSION”, 6mm (1/4”) male to female
  • A “Y” adaptor for connecting 2 headphones into a headphone outlet, 1 x 6mm (1/4”) male to 2 x 6mm female

     

The GRADO Phono preamplifier PH1

It allows connecting a turntable into a receiver (or preamplifier) that does not have a “phono” input.
Designed to accept a moving magnet cartridge (high output) as well as a moving coil cartridge (low output).
The design of this ‘phono’ preamplifier was a challenging task, similar to the one GRADO faced when designing the headphone amp RA1.

The PH1 was to:

  • handle cartridges with all output levels and a very high saturation point
  • be exceptionally musical
  • have a very low noise level
  • present a very large bandwidth
  • offer a close to perfection RIAA correction
  • be phase coherent
  • have a very low impedance output

GradoPhonoPreamp


The GRADO design team realized immediately that a challenge like this was not going to be met by using either of the time-honored methods of passive or active equalization circuits. The relative advantages and disadvantages of these old methods are very well known: the passive preamp approach is characterized by problems of first stage headroom and second stage noise. This is due to the 40dB high frequency insertion-loss of the passive network itself.

 

A phono stage gain is frequency dependent on the result of too little feedback at the low end and too much at the high end. Of course, both extremes are sonically non-optimum and unacceptable.

The more commonly used active equalization stage provides solutions to the classic passive circuit problems, but it also comes with a whole new set of its own problems. These difficulties arise out of the subtle ramifications of the classic negative feedback theory. The RIAA characteristic requires that the amplifier's closed-loop gain needs to change by a hundred to one (40dB) over the entire audio range. This means too little feedback-closure at low frequencies and too much at high frequencies. Too little causes inadequate suppression of simple distortions, and too much causes the generation of complex distortions (high-order).
The new GRADO phono preamp circuit design now has all of the advantages of the old methods, yet none of its antiquated disadvantages! The challenge was met! The processing problem has been split into two separate parts: a forward propagating signal current and a back propagating error voltage. We have indeed eliminated all of the past methods. Our new phono equalization technique is a derivative of the principals that we used in our highly regarded RA-1 headphone amplifier. In this design, feedback closure ratio does not change with frequency, but the total output gain does. Virtually all latter stage noise disappears! The output impedance is very low, with the EQ stage opened-loop and the closed-loop gain being the same. The best of both worlds!
What is so significant about these new innovations is the fact that the technical superiority claims absolutely correlate to an unprecedented improvement in openness, greater depth of field and increased definition to the sound of eachmusical instrument. The PH-1 offers a true freedom from past sonic problems along with GRADO's usual warm, smooth, full bodied, non-fatiguing and rich sound qualities that everyone has embraced. If your turntable is driven with a GRADO cartridge then you deserve to go the final step with the new PH-1 phono preamplifier.


The GRADO headphone amplifiers RA1

After relying, for many years, on other manufacturers to power his headphones GRADO took the decision to design his own headphones amps: the RA1s

GradoRA1










 
  • The “RA1 Bat” is a perfect match to any GRADO headphone. It will let you enjoy music anywhere for 40 hours (on a set of 2 X 9v batteries).
  • The “RA1 AC”: as the name says, is powered by an AC adaptor (very hefty.
  • The RA1 HG (special order) was designed for higher impedance headphones, (most German headphones).
These headphone amplifiers are housed in a solid block of mahogany and measure: 13cm (5") in width, 14cm (5 1/2") in depth and 4cm (1 1/2") in height; they weigh 336g (12 oz).

Anyone of the 3 above GRADO HEADPHONE AMP, coupled with a quality portable player, uncompressed music, will make a very high end portable audio system.

GRADO “MINI”  Adaptor

GradoMiniAdaptor

 

This is a 20cm (8”) long adaptor with a 3.5mm male (mini) and a 6mm (1/4”) female.
It allows connecting a headphone fitted with a 6mm (1/4”) plug to a player having a 3.5mm (mini) output.

This device will decrease the mechanical stress on the player connection.

This adapter will not introduce any sound degradation

 


GRADO “EXTENSION”

GradoExtension

 

A 4.5m (15 feet) extension is available. It has a 6mm (¼”)
male at one end and a 6mm (1/4”) female at the other.


This extension will not introduce any sound degradation

 


GRADO “Y” Adapter

GradoYcable
  2 headphones (with 6mm, ¼” plugs) can simultaneously be connected to the output of a receiver, player or any other device.

This adapter will not introduce any sound degradation

1234

  123
Updated: August 2014