The Cole Phono Stage

The Cole phono stage is produced by my briend Brian Cherry of DIYHiFi Supply in Hong Kong. I got the chance to build one of the first Cole phono stages in order to produce the instruction manual for the kit. Cole is a tubed phono stage that uses one 12AX7 and one 6922. Cole's power supply transformer is contained in a separate chassis connected to the main unit by an unbilical cable. Both the HV and filament power supplies employ solid-state DC regulation, which is unusual in a product in this price range. High-quality step-up transformers are also included making Cole able to handle either MM or MC cartridges with the flick of one of its rear panel switches. In addition, MC cartrige loading of either 5 Ohms or 40 Ohms can be selected via a rear panel switch.

An experienced builder should be able to build the Cole in 4-6 hours.

Construction of the kit is exceedingly straightforward due to the fact that all of the major components come already mounted on an high-quality PCB. Construction entails only witing the power supply and wiring of the input and output curcuity.

After the power supply is completed, all that remains is to attache the matching pwer jack to the rear of the chassis and wire the appropirate power connections to the rectifier tube and PCB.
Lastly, the input and output jacks are attached and wire to the PCB
Shown below is the completed unit. The brass objects at the top of the PCB are the stepup transformers for MC cartridges.

Teaking Cole Freshly built, the Cole sounds pretty good. I listened to it for many hours and compared it with my Wrigth PP/100 phono stage which costs $850. Compared to the Wright, the Cole had a tad less harmonic structure to the sound than the Wright. The Wright on the other hand, has a tendency toward noise due to the high-gain of its 6ER5 tubes.
In actuality, the differences between the two units were very small and I could listen to either unit for hours on end.
The first tweak I tried was to upgrade the coupling and output capacitors to Auricaps, very easy to do thanks to the PCB. Adding these produced a major upgrade in the sound. There was more harmonic information present AND the soundstage became wider and a little bit deeper. The auircaps take well over 40 hours to fully break in so be patient.

Mullard/GE 6DJ8 with Dimpled Ring Getter

Tube Rolling I rolled several 12ax7's abd 6DJ8's through the Cole. The major difference I heard between the tubes was the amount of energy/clarity in the high end of the spectrum. None of the tubes made the sound grainy, just added more or less energy to the upper octaves. The 12AX7's I tried are listed in decending order of "brightness". Again, none of these tubes was glaringly bright or grainy. Different folks may prefer a different flavor!

Electro Harmonix 12AX7EH
EI Gold Elite 12AX7
JJ 12AX7
Telefunken 12AX7 smooth plate

Among the 6DJ8/6922's I found the same thing. The major differences were in the energy imparted to the higher freqencies. The tubes I tried listed again in order of decreasing high-end energy were
Tungsram 6922
Sovtek 6922
Amperex 6DJ8 globe logo, ring getter
Amperex Bugule Boy ring getter

The only tube I didn't like was the Tungsram. It's sound was a tad "steely". The most intesting tube ws the Bugle Boy which produced a wider soundstage than all of the others with that sweet Bugle Boy midrange. Paired with the JJ 12AX7 (my favorite of the bunch) I had a soundstage that went wall to wall and sweet violins.

Then, it happened, I found THE tube. One night while browsing EBay, I saw a pair of "GE" 6DJ8 tubes for sale that looked like none I had seen before. They were marked "made in England" and had a dimpled disk getter that had a single support rod. I got the pair and popped one into Cole and, OH, the Magic. It produced the sweetest sound I've ever heard from my vinyl rig and it is THE tube for Cole. The inmates at Audio Asylum tell me the tube is a Mullard from the 60's. Whatever it is, I'm through rolling tubes in Cole!

Jupiter Caps Next I rolled in the Jupiter beeswax/paper capacitors. These too took two days on the Frykleaner to break in and produced an sweeter sound than the Auricaps. I think they are just ever so slightly rolled off at the very extreme top end of the frequency spectrum but no so that they sound dull or muddy. It's more a vintage tube sound. But wait, maybe I have to look at tubes again. Indeed changing the caps changed Cole's preference for tubes. I ended up replacing the Bugle Boy with the slightly higher energy Amperex 6DJ8 and got a very nice mix of sweetness and clarity.
The bottom line is that rarely are we teaking one component but rather the whole system. I learned that changing one component may affect how others interact. In your system the results may be completely different so, please, take my observations with a large grain of salt as they apply only to my systen (which leans toward the bright side of things) and my ears. I am neither a trained listener nor all that experienced at such comparisons.

I'm not done with this unit yet. Come back again to see what else I've done.