Coffman Labs G1-A Full Function Preamp and Headphone Amplifier - Preamp -

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(By Coffman Labs)

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"Judged strictly as a linestage for $5,495, the Coffman G-1A is at the top of its class.  The fact that it includes an excellent phonostage and headphone amplifier makes it the bargain of the year.  All of the tubes are easily found and those predisposed to tube rolling can tune and tweak until Election Day.   Coffman has plans to expand the lineup, possibly making the phonostage and linestage separate boxes. When I asked him if there might be a companion power amplifier in the works, he smiled that evasive smile that usually means “yes, but I don’t want to talk about it now.”

So with that in mind, we award the Coffman Labs G-1A one of our Exceptional Value Awards for 2012 and look forward to the company’s future offerings.  Coffman is certainly off to a brilliant start.  I have purchased the review sample...- Jeff Dorgay - Tone Audio 


 "I was smitten with the Coffman Labs G1-A stereo preamplifier, even before I heard it make a sound. I'd seen pictures of the preamp online and it looked fine, but once I saw it in person I knew it was one of the most beautiful audio components on the market. The feel of the control knobs and the metalwork's fit and finish are state of the art. Granted, the G1-A is priced accordingly, but just as with high-end cars, watches or cameras, with purist audio design build quality is just as important as performance.  Still, I wouldn't be jazzed by the G1-A if it didn't sound special, and it does. I heard it in my friend David N.'s system, which never sounded better than it did with the G1-A. The difference was the transparency and overall clarity of the sound." Steve Guttenberg at C-NET


"Without a doubt well deserving of the Recommended Award and I defy anyone who hears this pre in a decent system to say otherwise.  Had this review been written in 2013 the pre would have been my joint electronics product of the year.  (as it is we'll have to wait till the end of 2014) I hope to make a deal for the demo unit?  Yes, I do."  Stuart Smith, HiFi Pig

Step right up! When we say 'full function', we mean in addition to having a killer active line stage this unit has a phono stage to cure all that ails you.  Does the family need a break from your incessant hifi-ing? Well, just plug in your favorite phones, (we love the Fostex TH-900 with the Coffman Labs) adjust the impedance to match and Voila, everyone wins.  

The G1-A made quite a splash in the hifi world.  It was conceived by musical passion but designed with military precision. Of the 3 or 4 reviewers to have it in house, I think only one didn't want to purchase it. That's a helluva ownership ratio when it comes to reviewers.

Here's a little video by Damon prior to the specs which you can find below:



Here are the specs:

Inputs: 5-position Selector Switch:
Phono, Mute, S1, S2, or S3 selected at Front Panel
Phono: Rear Panel Switch selects type:
MM1 selectable impedance 47K / 70K / 95K
MM2 (95k) or MC based on purchase option
Mute: Shorts all inputs plus REC Out
S1 & S2: 100k input impedance
S3: 10K input impedanceOutputs:  5-position Selector Switch:
Out: (inverted) Direct output via Headphone jack
Note: Rear Panel Main outputs are disabled.
Low: (non-inverted) Selects Headphone jack (32-100 Ω) *
Hi: (non-inverted) Selects Headphone jack (100-300 Ω) *
Off: Shorts all outputs
On: (inverted) Selects Rear Panel ‘Main’ output jacks
-Output impedance: 600 Ω ‘Out 1’ and 1000 Ω ‘Out 2’
[Rear Panel REC Out (non-inverted) always present]* Let your ears be the judge—try both settings.Gain:
Phono to REC OUT jack:  MM=36 dB : MC = 52 dB
Max Phono Gain (Line out):  MM=60.5 dB :  MC = 76 dB
Line level output maximum undistorted: +14 dB
Max Headphone power: ½ watt at 32 Ω, ¼ watt at 300 Ω


Tube Complement:
2 X  12AX7 / ECC83 (RIAA Section)
2 X  12AU7 / ECC82 (Phono Boost)
2 X  5687 (Line Stage Output)
1 X 5AR4 (Power Supply)

Equalization: [measured into a 5 ohm load on MC input]
Passive RIAA, Paper-in-Oil (PIO) capacitors used for filters.
+0.5/- 0.2 dB 20Hz-20KHz (typical) 1Khz standard.
7 Hz rumble filter inherent in Phono Section

Frequency Response:
Line Stage: 20Hz–100KHZ +0.2/-0.5dB; 15Hz–150KHz + /-1.0dB
Headphone: -1dB at 15Hz; -2dB at 20KHz [Sennheiser 650]

Signal to Noise:  (partially dependent on specific tubes used)
Phono:  approximately 85+ dB
Line Stage:  approximately 100+ dB

Power Supply filtering:
Separate external AC line filter not normally required
Line/Boost section supply hum down over 130 db
Phono section supply hum down over 150 db
Type:  zero feedback multi-pole choke input
Heater Supply type: 7-pole filter.  ~80 dB ripple reduction

Chassis Configuration:
Separate power supply on 4-foot cable.
110/120 or 220/240:  Factory set per order

Purchase Options:
Moving Coil: Replaces one MM input with MC input.
Note: MC step-up is 15.5 dB, 0.3mV output
or higher recommended.
120/240 Voltage:  Specify at the time of purchase.

Amplifier: 12 ½” D x 7 ¾” H x 9 ½” W
Power Supply: 12 ½” D (with 5AR4) x 5 ½” H x 6 ½” W


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