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MKIII Solo - Monitor Class

• C-Drive cool running "class A" sound
• Alps volume control
• C-Cap technology
• By-passed and Elna Audio capacitors
• 350V/µS Analog Devices input stage
• 100MHz output stage
• Seamlessly integrates with tape loops
• Teflon & Gold RCA jacks
• Unique extruded aluminium case
• Just 1U (44mm) high*
• A match for the best headphones

Why change? Number one reason, the new sleek aluminium extrusion case (latest silver version pictured above) came on-stream in June 2001, and got us thinking about some of the suggestions by TNT's reviewer DVV. As good a time as any to ring the changes without losing the excellent performance.

We kept what we now call C-Drive. A technique where the headphone is driven by a current rather than a voltage. This technique reduces the effect of intrinsic emitter resistance found in conventional amplifiers, with results similar to that of pure class-A!  What we don't get is the wasteful heat produced by class-A and the frequency limitation imposed by having to use high power transistors. Therefore we can use extremely fast 100MHz output transistors.

We also kept the legendary Analog Devices op-amp based input stage, renowned for its ultra fast 350V/µS slew rate and even faster (70nS to 0.01%) settling time. Given a few hours warm-up, the music it makes is a revelation.

Out went the original volume control, and in came the Alps. A high quality control sharing much of the specification of the bigger blue velvet.

Where capacitors have to be used in low level signal areas, a combination of C-Cap (compound capacitor) techniques, and Elna Audio Grade capacitors, replace those previously used. Film capacitors have been replaced by Wima and Evox polypropylene types.

Bass is now more powerfull and deep, which is unusual for headphone amps, but reviewer DVV already said about the original model "...The bass is deep, but its main virtue is its cleanliness, its lack of overhang and its good definition...". We simply built on that, but not by providing any bass boost, the frequency response is flat, it's just engineered properly.

The bass takes nothing away from the performance either. Here are some quotes taken from a recent Zero-Distortion.com review:-

"...plenty of ambience, and the feeling of the acoustics of the recording room/studio was protrayed very well indeed..."

"...the Solo's probably greatest virtue is that even at very high volume levels, the sound remains firmly knit together, it's the big picture all the way, no segments, no fancy midranges at the expense of the extremes, all of it just pours out at once..."

Facilities

Usually, when you buy a headphone amp, you end-up losing some of your existing facilities. Integrated amplifier users usually have to ditch the tape deck to connect the headphone amp to the tape loop. The Solo, however, can be connected in parallel with the tape loop, and phono tee-adapters are included in the purchase just for this purpose. It's two high impedance inputs (30k) make it transparent to the rest of the system. Once connected, full headphone facilities are at the flick of a switch. One input can select whatever source is selected on the main amp, the other, tape. Just like a tape monitor switch!

You can continue to use the rest of the system as normal, because of this seamless integration.

Alternatively, the Solo's two inputs can be used with any line source of your choice.

Connections are by Teflon insulated, Gold plated phono sockets. The best type, normally only found on high-end gear, but featured on many GSP products.

Headphone Compatibility

C-Drive allows a surprisingly wide range of impedance's to be driven by the Solo with no loss of level when using high impedance types (e.g. Senheiser and Beyer broadcast 'phones). The Solo will drive any dynamic headphone in the range 20 to 600 Ohms with ease. It is a perfect match for the highest quality headphones, plus budget types such as the Grado SR60.

Is it loud enough? Forget wattage! This headphone amplifier will easily put 100 decibels onto your eardrums, although I would advise you turn it down, just a bit.

"...Turning the wick up, I got volume, as much of it as I could possibly want, and WAY above that. Of course, in absolute terms, how loud will depend on headphone efficiency just as much as on the amplifier, but believe me, if I ever let go, I'd end up with punctured eardrums. Let's just say it'll go much louder than you can ever stand for any period of time without permanently damaging your hearing..."
(Zero-Distortion.com)

Outboard Power Supply

"...the concept of two separate cases is top notch..." (TNT-Audio)

The Solo is powered by the (included) PSU1 outboard power supply, packed with Panasonic ultra-low impedance reservoir caps, 12VA transformer, and low impedance voltage regulator. As if this stable supply wasn't enough, it is further regulated inside the Solo to provide the stiffest possible DC rail to the signal.

The Solo's output is short circuit protected, not only protecting your phones from damaging direct current, but allowing the Solo to keep driving at full load current!

Appearance
The Solo is housed in our new 1U height (44mm * plus feet) satin anodised aluminium case. It uses a special extrusion which makes up the top and bottom sections, and engraved and dyed front and rear panels, held together with 8 stainless steel allen bolts.

The front panel carries the volume control with solid anodised aluminium knob, input selection switch and heavy duty 6.3mm (1/4 in) headphone jack socket. With two pairs of Teflon insulated - Gold plated phono jacks and DC power supply socket, to the rear.

The generously rated, double insulated, linear outboard power supply (the PSU1) is contained in an Underwriters Laboratories recognised UL94V-0 case. With captive ac mains input lead and a DC output lead terminated in a plug for connection to the Solo's power socket. Two versions are available: 200-250 volt 50/60Hz (UK, Europe, Hong Kong, etc...)  BS1363 13 A plug, and 100-125 volt 50/60Hz (USA, Japan, etc...) terminated in an American 2 pin plug.

A kit of 4 gold plated phono splitters is provided for insertion into an integrated amplifiers tape loop. With full instructions.

Additional comment
sent by e-mail from TNT-Audio reviewer: Dejan V Veselinovic

"I put on a CD I bought in New York in 1991, a CD version of Simon & Garfunkel's album "Bridge Over Troubled Water" into the Yamaha CDX-993, turned on the Solo, put the Grado SR-60s on and man, I was gone for two solid hours.
The Yamaha has two outputs, one fixed, which leads to the Karan Acoustics KA-i180, and the other one variable, which leads to input 2 on the Solo, bypassing the Karan altogether.
Jesus, Graham, the Solo/Grado combo gave me goosepimples, laughs and almost tearful moments. So much emotion! Such life!
I have no idea how many times I heard that album, must be over a thousand since it appeared on LP in 1970, but tonight, I heard things I never knew were there. Details almost lost in the background, but I actually heard them.
Sure, it's partly just the right mood, I know, but then, isn't music all about mood? And mood may do something for my emotions, but it does nothing for my hearing.
Like I said, the Solo is an excellent performer. I simply underline that now."