Manual

decade restoring it. [We thank Paul for his efforts and his contribution to our efforts to

trace the history of the 610.]

At least one 610 module is still in use at Oceanway. Allen Sides, who purchased the

studio from Putnam to open Oceanway, personally traveled to Hawaii to collect the 610

console that was used to record the live “Hawaii Calls” broadcasts. Jack Joseph Puig has

been ensconced in Studio A with the 610 (and a stunning collection of vintage gear) for

nearly five years where he has applied the vintage touch to acts including Beck, Hole,

Counting Crows, Goo Goo Dolls, No Doubt, GreenDay and Jellyfish

The 6176 you have purchased carries on the illustrious history of the 610. The 610B

circuitry is identical to one half of our 2-610 Mic pre with a few exceptions. We have

added a 15dB Pad switch and a power supply modification.

1176LN

It was Bill Putnam himself who, in 1966, was responsible for the initial design of the

1176. Its circuit was rooted in the 1108 preamplifier which was also designed by Putnam.

As is evident from entries and schematics in his design notebook, he experimented with

the recently developed Field Effect Transistor (F.E.T.) in various configurations to

control the gain reduction in the circuit. He began using F.E.T.s as voltage variable

resistors, in which the resistance between the drain and the source terminals is controlled

by a voltage applied to the gate. His greatest challenge was to ensure that distortion was

minimized by operating the F.E.T.s within a linear region of operation.

After several unsuccessful attempts at using F.E.T.s in gain reduction circuits, Putnam

settled upon the straightforward approach of using the F.E.T. as the bottom leg in a

voltage divider circuit, which is placed ahead of a preamp stage.

The output stage of the 1176 is a carefully crafted class A line level amplifier, designed

to work with the (then) standard load of 600 ohms. The heart of this stage is the output

transformer, whose design and performance is critical. Its primary function is to convert

the unbalanced nature of the 1176 circuit to a balanced line output, and to provide the

proper impedance matching to drive the line impedance of 600 ohms. These two jobs are

accomplished by the primary and secondary windings whose turns' ratio defines the

impedance ratio.

This transformer is critical due to the fact that it uses several additional sets of windings

to provide feedback, which makes it an integral component in the operation of the output

amplifier. Putnam spent a great deal of time perfecting the design of this tricky

transformer and carefully qualified the few vendors capable of producing it.

The first major modification to the 1176 circuit was designed by Brad Plunkett in an

effort to reduce noise--hence the birth of the 1176LN, whose LN stands for low noise.

Numerous design improvements followed, resulting in at least 13 revisions of the 1176.

Opinion has it that the D and E blackface revisions sound the most “authentic”.

Both the 1176 and the LA-2A remain in daily use. Busy engineers and producers’

comments about both the 1176 and the LA-2A demonstrate their impact on the industry:

Mike Shipley (Def Leppard, Shania Twain, Blondie): "I grew up using 1176s --- in

England they were the compressor of choice. They're especially good for vocals, which is

also what I primarily use the LA-2 for. Most anything else I can do without, but I can't be

without at least a pair of 1176s and an LA-2A. For example, on the Enrique Iglesias