EZ Line Stage from diyhifisupply, Hong Kong
Copyright 2012 Troels Gravesen

I bought this line stage kit out of pure curiosity. I like it simple and can we really get a good line stage from this simple board with a single tube? One board, one tube, one mains transformer, a potentiometer and a selector + a bunch of phono sockets, that's all. And it comes at around 500 USD.
My thought was to find a high-performance line stage supplementing the JungSon Duro power amp, which also comes for 500 USD at Cattylink. A total of 1000 USD for a high-performance amplifier combo. I've had the opportunity to compared my Jungson JA88D-09 with the Duro and I didn't find any difference in performance. The Duro is the JA88D-09 without MC stage, attenuator and line stage.

There could be a whole range of reasons not to buy this product, but one reason we should anyway:
The assembly manual print is poor. Download here. Former manuals on TRAM and Joblin from the same supplier were beautifully made. 
The cabinet is awkward in having the board and trafo on the bottom panel and whenever you have to tweak you have to disassemble the whole thing and you have bottom panel + front and  rear panels scattered all over. Buy a piece of alu and fasten to the top of the cover panel so that you can have it all nicely in front of you fully assembled except for the bottom panel. View photos below. 

One part of the no-name tube produced nothing but hizz. One Tezla ECC88 promised at website. I have some NOS Siemens ECC88 and some Russian 6N1P on the shelf. I used the 6N1P.
One deck of the attenuator didn't work and after a few steps all of a sudden was fully open. This can be seriously damaging to speakers and potentially damage power amp as well. I've had three Chinese made attenuators over time and the fault percentage is 100. I've managed to make two of these working by soldering here and there. This one I had to fully disassemble and solder some of the resistors, which is trouble as these surface mount resistors are really tiny. It turned out one resistor didn't connect to the next and passing that point the signal all of a sudden doesn't have any ground connection = full signal. Quality check in China can be zero but I think hifisupply should check components before shipping.
Wiring prescribes use of shielded wire. Not supplied with the kit.
Manual states led indicator on front. Not supplied with the kit - now we're at it.
0, 6, 12, 18, 22 and 30 dB gain options are promised at website. Only 6 and 12 dB available according to manual. No instruction on how to get the other gain settings. The 12 dB setting does well with the JungSon, so no problem.

After this grumpy intro, let's talk sound.

The supplied Obbligato coupling cap does well and I'm again puzzled by the sonic quality of these caps because you can listen to a range of music and feel it really doesn't get much better than this. Then comes another piece of music suggesting this doesn't come with the level of resolution it could be. So, in went some tin foil/PP caps and they are seriously close to the best. If budget is an issue buy 2 x 2.2 uF tin-foil/PPs. Next I tried tin-foil/PTFE and we're there. From here on it's a matter of taste. Finally I inserted 2 x 1 uF Mundorf silver/gold/oil and these are likely to stay in place. They may not be as smooth as the tin/PTFE but they may have an edge in resolution. Mind you, tin/PTFE caps do not come with inter-wound series coupled windings like the super caps do. I wonder how this would perform.
Obviously I'm comparing the EZ line stage to my 6N6P transformer coupled line stage. It would be nice if the EZ could match the 6N6P. It doesn't, but it's damned close. The 6N6P has that easy flowing, see-through midrange that made me spend an indecent amount of hours putting it all together - and it costs somewhat more then the EZ due to all the trannies needed. The EZ is in no way a smooth and forgiving (read dull) tubed line stage meant to oil harshness in other parts of the chain. It's a vivid, dynamic performer doing what a line stage should do. In principle a line stage should do nothing except increase gain, but it's not as simple as that. Every time I've tried a passive ditto, the result has been a flat, un-dynamic presentation. Beautified hifi some would say. I don't care as long as it makes me feel better about my system.

Getting it all for 1000 USD (EZ + Duro) may not be quite possible. We have to add ~200 USD for two good coupling caps - and we have to add shipping. Let's say 12-1400 USD all done and we have a basic amplifier system than can run high-efficiency speakers as well as the usual standard-HIFI low-efficiency systems, maybe except the very large/low-efficiency speakers that really do best when power is unlimited. You could buy the minimum 300 USD EZ kit and use the residual 200 USD on two caps. The supplied potentiometer may do as well at the attenuator.

FYI: I have no connection to any of the manufacturers of the components used here.
There may be other valve line stage manufacturers that would do well with the Duro, but I haven't tried. The Bottlehead Foreplay III comes to mind although not as easy to build as the EZ.

Click images to view large

This is the line stage upside down. I suggest adding an alu panel to mount board, input selector and attenuator. The torque of this attenuator is so high that the knobs provided are too smooth for proper operation. When you turn the attenuator is like starting an engine with a broken crankshaft. I added a strip of non-slide tape to have a firm grip. And add a bitumen pad to the alu panel (underneath) to further dampen the sound of the attenuator. 

New Mundorfs in place. To the right the infamous Chinese attenuator. The input selector works excellent.
These silver/gold/oil are nothing short of excellent. Smooth and loads of detail. In fact I think better than tin/PTFE.

The Low-Cost Version

The cheapest EZ line stage kit, 300 USD. This kit will do the same as my 500 USD kit, but you need two good coupling caps.

Duro power amp. 2 x 80 watts class A. 
Whether all of these watts are truly class A I can't tell - and frankly, I don't care. 
What is does, it does darn well and for 500 USD it's a total steal. Be aware this may double due to transport and VAT before it hits your doorstep.


More pics from my EZ line stage, click images to view large

To the right bitumen pad added to mounting plate. Dampens mechanical noise from attenuator.

Have added led indicator and mute switch to front panel.
The led supply comes from 9V AC filament supply. Use 390 ohm resistor.