Universal Tube Stage
Universal stereo tube output stage


Hybrid anode follower with circle of two CCS using ECC88/6922/6DJ8/6H1/6CG7
(not included). One board can make a stereo output tube stage for a DAC or line pre-amp. Two boards can make a balance output tube stage DAC or line pre-amp.


A RIAA correction network can be fitted between two boards and make a nice phono stage with about 40 DB of gain. Two boards with a 10K LCR and a 10K termination resistor would be an easy way to build an LCR phono stage.

• S/N ratio > 100 DBA,
• 2V RMS into a 10K, THD is around 0.1%
• output maximum around 10V RMS on clip into 10K load <1% THD
• 20 Hz to 20 KHz <-0.5db
• output impedance is 75-100 ohm.
• dimensions = 140 mm x 80 mm x 45 mm
• Tube used: ECC88/6DJ8/6922/6H1/6CG7 only.
   Do NOT fit 6H30 or 6H6
• includes Obbligatto coupling capacitors.



Application notes (pdf)



Review
DIY HiFi Supply EZ line stage containing the UTS on TNT-audio.com

Less Is More -- A Little Glass and Vacuum

it still never ceases to amaze how little glass and vacuum can bring forth the power and glory of music. As good as the Satch DAC sounds with the opamp output stage, adding a vacuum tube takes the sound to a new level -- bigger, richer, more. Considering the cost of OPA 627 and the other more analog sounding opamps (especially the premium B. series), the universal tube output stage is great value.
I don't think any op amp will even come close to the sound we get here. Take a look at the pictures; it's not that difficult to install. It does take a little bit of ingenuity to piggyback the UTS over the mainboard. First remove the opamp daughtercard and drill a couple extra holes just back side of the mainboard to accommodate two standoffs to fit in the mounting holes in the UTS (universal tube stage). Position the holes so that you can mount a third standoff on the existing mid- edge on the transformers side.



The Inside Story-- Universal Tube Stage

just to provide some reassurance -- you can see below that the Universal Tube Stage is not a cathode follower nor a simple buffer but is a real gain stage.





EZ Lo-Z Linestage

240mm Projekt Box
6 prs RCA jacks
1 Selector switch
1 pc stepped attenuator
2 knobs
4 Isomount feet
UTS module and power transformer
3M hookup wire

with the above list of parts this allows for 4 inputs on the selector and 2 outputs from the UTS module. Considering the very low output impedance it should be no problem.

Per page 30 of the Universal tube stage instruction manual, jumpers set for 6db. gain only requiring L/R and GND connections on the input of the module.

We knocked this together pretty quickly and didn't use any shielded input wiring but even so in this 240mm case were getting much less than 1 mV output noise.

Replacing the TVC the most noticeable feature is low bass frequencies are being driven much lower and with more power. soundstage is expansive and reaches outside the speakers. Complex musical textures are more pronounced and strings have more bite. Well I guess that's what we should expect since now we've got tubes on the front end. you may be due to more favorable impedance matching were also getting more dynamic contrast.

So here is an EZ way to get a very high-end tube sound, without worrying about tube noise. Easy to drive and in turn, should drive even insensitive and low impedance amps without compromise.

This Couldn't Be Any EZ'er

A couple of blog entries ago I described the EZ Lo-Z Linestage using the Universal Tube Stage (UTS). Already the UTS is establishing itself as the way to get music back in your system (it delivers pure grownup tube tone), and it packs a punch!
Most UTS are finding their way into DACs. But that's just the beginning of what can be done with the UTS. Check out the EZ picture based manual. it's almost too EZ.
No need to worry about layout issues, grounding, etc. It's all done for you.
So bring back the music, the EZ way.



Sweet Sounds - EZ!

Yesterday we got the UTS EZ linestage with Extensions into the system.

The shaft extensions make a difference: sound is improved

1. more immediate, micro-macro dynamics resolved more easily, big transients seem strike from out of nowhere and delicate sounds present themselves with noticeable finesse
2. self-noise has dropped significantly; ~0.2mv which is close to our limit to measure and maybe explains some of #1 (update: with 0.4mm copper tube shield in place, grounded to chassis it drops to 0.1mv)
3. The tactile quality of switch action is much improved due to the effect of the flexi connection between shaft and switch. IMO clunky switching puts the ears in a bad mood

We will still try some other enhancements:
coupling caps - we have the obbligato tin foil and a sample pair of paper-in-wax aluminum foil (huge)
tube shield, etc.



EZ UTS-Projekt Phono

As shown in the UTS manual. Basically a 2-UTS-modules-in-series-and-RIAA-network sandwich.

We found it needs 2 power transformers. Reason: to break ground loops and forestall AC filtering imbalance since in a phono stage noise is a paramount issue. Place the transformers in a separate steel box for shielding.

AC wires need to be shielded and the shield connected to IEC chassis ground.

Result: state-of-the-art low noise (0.1mv self noise) and big dynamics tube phono stage with about 36-38db gain (depending on tubes)

And – it’s EZ!

The recipe:
Large Projekt box with feet, connectors and switches etc
Steel enclosure for power transformers
2 UTS modules and 2 power transformers
RIAA parts
AC wire braided shield

Assemble, connect, plug and play!
EZ and no noise tomfoolery.



TNT EZ Linestage Review and Wishing I Was There...

...in that winecellar.
Nick Whetstone of TNT,(one of the earliest webzines), has just posted a review of the EZ Linestage.
Read it here

Universal Tube Stage

I want to draw attention to the centre-piece of the EZ Linestage: the UTS (Universal Tube Stage) module.

It was designed as an EZ add-on output stage for a CD/DVD, allowing the removal of the most serious limitation in modern players: the opamps. The trick is to accomplish this without using a cathode follower or buffer, which has its own liabilities. The UTS output is taken from the anode; much of its good sound is attributable to allowing the anode to play its natural role

Coincidentally, the 0.5v > 2V gain needed by a CD player outputs suggests its application in a modern linestage - ergo the EZ linestage.

However if we series a pair of UTS and set the jumpers to highest gain we now have a state-of-the-art quiet phono stage, just needing a simple RIAA network in between.

So: UTS module >>CD/DVD tube output stage>>EZ linestage>>EZ phono stage.

But that's not all! One power transformer can power two UTS modules so if we wanted a balanced output stage - just use two and configure as shown in the instruction manual.

The Universal Tube Stage does it all.

Also we will momentarily have our Ultimate Volume Control working together with the EZ Linesstage. This will be the ultimate in transparency and utility.



Vinyl Song


We are spinning vinyl again. Didn't have time to really do the setup since we moved in April but its needed for the work we are doing with the UTS phono system. Also we have a sample of our turntable bearing and the setup gives us a chance to test it.

The Cinemag step up transformers have gotten good comments wherever they turn up. They are the real deal: Mumetal, Faraday Shield, 18 or 36:1 and measured bandwidth up there with the exotics. They are compact and easy to mount. Their small size means means smaller core and more winding thus copper losses. But they are well-engineered and must be the best value step-up transformers around.

We've connected them close to the input jacks and HiLo silver contact switches make for less stray wiring and thus avoid antenna effect. They add no noise to the MM side of the circuit despite the extra +20db gain. I'd read about some noise problems so was worried we would have a challenge taming the noise. But no problem and result is the quietest phono stage we've ever had in-house.

So on the back panel we have from (background to foreground):
RCA outputs
MM input
MM/MC switch (made-in-Japan silver contact toggle)
Hi/Lo switch (also silver contact) to control gain and loading
(36ohm/56db; 145ohm/63db)
MC RCA input
Chassis ground

MM gives 36db of gain and MC switchable 56/63db

Then you see the Cinemag transformers
Next the RIAA network (polysytrene and tantalum or Takman)
In the middle are the UTS boards with Tinfoil caps for coupling.
The rectangular box provides shielding and an enclosure for the transformers.

Been playing using a Shelter 501 Mk2/Bluenote arm (the best one they made at the time). Sound is full range, dynamic and throws a big soundstage. The Cinemag really surprises considering the cost. Next I need to dig out my Denon 103r and a Shelter MM I have around here somewhere.

So all in all a reasonably priced fully MC capable phono stage that's EZ to build and maintain.



Vinyl Song - #2

EZ is as EZ does..


BTW: the picture shows LCR with different labels but they are both 10k.

The ultimate RIAA EQ solution is an 'LCR'. Unlike cap/resistor networks, it puts nothing in the signal path except high quality chokes. The caps and resistors are to ground so they are mostly out the way. The result is a bigger soundfield, and more dynamic contrast and transparency.

BUT, not so easy to implement as stages around the LCR need to be impedance friendly and layout is critical, noise becomes the problem. An LCR phono stage is one of the more difficult DIY projects.

As explained in a previous blog, two UTS modules set for high gain, in series, with an RIAA network in between makes a dead quiet 36db gain phono stage. (UTS >> RC RIAA >> UTS = 36db phono stage).
Now just remove the RC RIAA and replace with 10k LCR: UTS >> 10k LCR >> UTS = 36+ db phono stage. Everything needed is already there - only a 10k loading resistor needs to be added across the LCR out and ground. = 36+ db because there is an increase in volume level of about 1 or 2 db compared to the RC RIAA.

This recipe is playing now.
There is one more possibility: 600 ohm LCR. The UTS has low enough output impedance to drive it and offers the possibility to direct couple to the driving stage. Over the next few days we will be exploring that possibility as well.

Whichever turns out best will be our UTSphono-Max.



Vinyl Song - #3

10k LCR - that was fun.

Today we installed the 600ohm LCR modules. Just remove the RC RIAA and drop in the modules. This takes advantage of the very low output impedance of the Universal Tube Stage (UTS) (50-100ohms). Adding a series resistor to the input side to bring the load that the first stage sees up to 600ohms allows us to direct couple. So...exchange one 2.2uf capacitor for one series resistor. Make it a good one.

On the output side we need a decoupling capacitor - ~0.47uf in value. Again quality matters in this position so best use the best - teflon, polystyrene, silver - because you can hear the quality in this position. It won't be wasted. We used polystyrene.

Done. Playing now. First few minutes were a bit splashy sounding but settling in nicely. From 20hz-25khz we're at -0.5db which is as good as it gets with LCR.

LCR's impress with their open sound and huge dynamic swings.

This will be our new UTS Phono Max. It is EZ enough and we will release it as a kit. Instruction manual to be written.



Vinyl Song - #3b - This Is It!

The LCR600/UTS sandwich sounds great.

It took a bit of time but we've landed on this as the final layout for lowest noise:
LCR modules need to standup and are wrapped in MUmetal. So we cut some holes into the base plate so the modules would have clearance to stand up.
All wiring kept to the right away from the power transformer box. Tube shields used.

This gives us very low noise (scope jumps between 0.1mv and 0.3mv).
We will soon do a listening session with the original Cole LCR600 compared to this one as there are significant differences.
This is also the most RIAA compliant EQ we ever seen among LCR phono stages.

Got me reaching for vinyl again.