past 6 weeks have been a flurry of circuits, and I've made so many
phono stages it's become hard to keep track of them all. It has
been at least a month since I drove a Zen amp with one of these
phono stages and while I remember it worked fine, I don't remember
which one I used, so tonight will be another hopefully final test.
have employed the Zen Design technique along the way on most all
of the design variations that I've done. All the while confirming
that it is indeed the superior method by wasting tons of time building
and listening to everyone else's circuits. In any case, while using
this technique I made an original discovery that no one has ever
done that adds a level of real magic to the sound so I've been pretty
excited about it. It's very much a Zen thing and will have most
engineer's rolling their eyes but ask me if I care?
I plunked a stock Zen amp off the shelf (SE84C) and plugged the
phono stage directly into it. I'm using a high output moving coil
cartridge (Dynavector 10x) on a Rega 3 table as a source because
it's an affordable combination that can (I emphasize 'can') sound
very good. I want to make sure this specific combination will work
with our stock Zen Triode amp.
as Murphy's law would have it, the record I grabbed was a little
on the quiet side, and the bias switch on the front of the Zen was
in the lower gain position so the results were a little iffy. I
used my 8 ohm 90dB speakers for this test. More efficient speakers
and it would have been fine right off the bat but not everyone will
have more efficient speakers. Besides, I'm trying to achieve a 2
volt output with this style of cartridge so I have the same volume
as a CD player. That is what my customers will expect.
doing it, but not quite... I decided to take a duplicate (yes, I
built two of every design I tried) and add a stage of gain so I
could get the dynamics and voltage up a bit more. That went on for
a couple hours running back and forth comparing to the original
until I finally figured out that the original was just fine, perfect
in fact and that it was the particular record I'd chosen that had
the reduced level. I should have had more faith. My punishment was
the two hours I wasted and the capacitor I discharged across my
hand by accident.
it happened.... I grabbed an older Windam Hill record of average
quality (not a master) and plopped it on the turntable, turned the
amp up all the way and sat down for a listen. It was going very
good. You know the feeling - when things sound a little too good
and you feel like you're getting away with something! By the 3rd
track I was so overcome by the sound that I felt a deep emotional
rush building up. It was so good I was just floored. Soon tears
were running down my face and I just kept shaking my head in disbelief.
as if it somehow knew it was gaining control of my inner spirit,
It just kept turning on the screws until I had no choice but to
surrender to it. It reached right inside my soul and purged all
the residual stress I had which resulted in my breaking down and
sobbing. In my adult life I can still count the number of times
I've had a good cry on my fingers. I was very impressed considering
I have even better amplifiers. And I must admit that during this
balls to the wall listening session the amp did clip just slightly
on a couple parts. I remember dropping the level just slightly and
that was all it took to loose the edge or the magic on these 90
this point I received my closure - the phono stage was perfect.
But, now I wanted to hear my favorite track on the LP again without
clipping so I hooked up the Signature Monoblocks and the ZTPRE and
went for it again. I also after being so moved by the stock Zen
amp wondered if the Monoblocks would be as good. Sonic signatures
are delicate fragile things and while almost identical between the two amps, there are subtle differences. Notice how conservatively
I worded that?
I hooked up the Mono's and ZTPRE and gave it a listen. At first
I wasn't sure which was better. There were no signs of stress or
hints of clipping but something was different. It was good, but
I didn't feel like I was going to get teary eyed again. I realized
while listening that what I was hearing was probably the better
stereo separation of the mono blocks. Less perfect separation always
enhances the center image (vocals) and makes them glow by super
imposing the surrounding ambiance over the center image. That changes
the timbre and presence of center image a bit.
I engaged the dual core transformer on the Signature Zens - something
that adds bloom and size to the presentation. Well, holy cow...
I guess. Now it was surpassing the stock Zen without question. In
fact I didn't realize how good that option on the signature mono's
really was. I did realize that you really can't add bloom, only
reveal it. On CD's it's easy to tell when the switch is on, but
I often go back and forth between the two modes never totally sure
which is better. Now for the first time I was hearing it's magic,
and there was no question that it was better. No question that there
is far more bloom hidden in the grooves of a record than the bits
of a DAC.
this was somewhat of a relief because these amps certainly have
more potential than our stock Zen, wonderful as it may be. I listened
to another LP and then decided just for kicks to run the phono stage
directly into the amps without the preamp. I knew the level would
be just about perfect with these 90dB speakers so there was no fear
of blasting myself out of the room.
hooked them and listened to my reference track on the LP that caused
me to loose it a while back. Instantly I was stunned by what I was
hearing. The quality and perfection of it rose to a completely unexpected
height. I simply couldn't believe it. Frankly I was flabbergasted.
It didn't take long for me to realize that I primarily voiced my
preamp for CD's. If ever there was a reason to push the design a
bit farther this was it. All it would take is some 6922 tubes in
place of the 6N1P's and the preamp will be up to par with this source.
this experience sets what I suspect is the final rung in the ladder.
I've never heard anything this good before, and I can't imagine
that it could get much better. I had no idea I would reach this
level, no idea this level even was possible. So with great confidence
I will start building and selling this phono stage and put to rest
once and for all the ongoing argument of which can sound better,
CD or LP.
that I've told you the end result, here is what I've tried:
spent the first 45 days auditioning the best solid state units I
could find. I researched them, and went with designs that were highly
acclaimed and received class A ratings in Stereophile. My hope was
to find something I liked because I knew solid state could be stone
quiet, have no hum, and be compatible with most every cartridge.
didn't take long to go to batteries. A pure DC supply sounded superior
in every way to the best regulated supplies I could build. This
meant that to make it user friendly it would have to be rechargeable.
By the time I had designed a charging circuit that was foolproof,
the battery supply was more expensive than the phono stage itself.
Add to this the unpleasant discovery that rechargeable batteries
having a different chemical makeup do not sound as good as non-rechargeable
could get between 5 and 10 hours out of a set of 8 - 9 Volt batteries,
and when I reached a point where I'd chosen the best phono stage
and best DC power supply the end result was no better than the best
DAC's I've heard. In fact it made everything sound like really good
then put it aside and did a Curcio designed passive RIAA stage using
6DJ8's in a cascode configuration. I knew this would be pretty decent,
and felt confident it would surpass my reference solid state design.
fact, once you compare the bodacious and huge soundstage of the
tube design to the solid state side by side you can't help but come
to the conclusion that any more work with the solid state designs
would be a complete waist of time.
problem now was noise and hum. Again, when you A/B the two units,
you quickly conclude that the noise and hum are nothing compared
to the huge gain in fidelity so you say who cares? Well, reality
check. Unless I send a $4500.00 solid state phono stage with every
unit so you can compare the two and draw the same conclusion, I'm
the new objective was now to get a tube stage quiet enough and stable
enough to work in adverse conditions without it's sound or performance
faltering in any way. I spent about three weeks building prototypes
of this cascode design and ended up with 5 different chassis/layouts
to compare noise and hum issues between them. Some were better that
others, but overall there was a problem. During testing under adverse
conditions the design was unstable, had a tendency to be microphonic,
and just undermined my confidence, despite it's good sound.
then decided to build a couple Dynaco Pass designs so I would have
a stable unit to compare the cascode design with. If the cascode
design blew it away I would peruse that path. If not, I would possibly
come up with an exceptional variation of the last Pass. Well, the
cascode design sounded better than the 3 different versions of the
Dynaco circuit that I built so I turned back to the cascode circuit.
All the while this was confirming my preconceived notion that passive
RIAA sounds better than active RIAA.
few weeks past and a couple more prototypes materialized around
the Curcio design and even though I made some progress, the stability
just wasn't there.
then decided to try some other passive designs, some cascode, some
more conventional. I built two variations of each, having chosen
what I felt were the best looking circuits on paper. I got one of
each style to sound pretty good and felt like I was starting to
make some real progress. I still preferred the passive design, although
it had more noise and far less gain than the active circuit. It
did however have a larger soundstage and better bloom, and was more
played with these two opposite designs for almost two months until
I couldn't improve them any more and evaluated the results. To get
enough gain to drive a Zen amp (2 volts) was making this project
doubly difficult. I now had a couple different passive designs that
were quiet enough to get by with, but they needed a preamp to get
the gain up. Same with most of the active designs.
experimented with tube head amps built into each and compared that
with studio grade silver wound step-up transformers and rotated
between all 4 different turn table/cartridge combinations. Getting
something to work on all 4 was proving to be impossible.
the end I had created some real monsters in the gain department.
Enough to take the worlds lowest moving coil cartridge to a full
2 volts of output plus some. And with just the right combination
of low efficiency speakers (MMG magnapans 86dB and conventional
cone speakers at 90dB) I was able to start really enjoying the music.
Yes there was hum, and some hiss, but we were making progress.
this stage, now having 15 different working phono stages to listen
to, I stilled preferred the passive models for sound, and the active
models for quietness and gain.
units I ended up with were the final results of 15 different designs.
4 tube passive in a cascode circuit all 6DJ8's
2 tube passive in a conventional circuit using 12AX7's
3 tube passive with a tube head amp, 12AX7's and 6922
4 tube passive with tube head amp and cathode follower, all 6922's
2 tube active using 12AX7's
3 tube active with head amp using 12AT7's and 6DJ8
3 tube active with 12Ax7's followed by a 6922
4 tube passive using 6DJ8's in cascode with transformer head amp
2 tube passive using 12AX7's with transformer head amp
3 tube passive using 6922's in a cathode follower with transformer
3 tube active using 12AX7's with a transformer head amp
3 tube active using 12AX7's with selectable transformers and cathode
Reference solid state battery driven supply (to remain nameless.)
of the above (except for the solid state) used the ZTPRE dual mono
remote power supply and were dual mono circuits.
3 tube active using 12AX7's with 12AX7 head amp and dual mono power
supply that was NOT remote.
2 tube active using 12AX7's with dual mono power supply that was
general idea I had at this point, and I wrote some articles to that
effect at the time, was that the best of my passive designs would
be my signature phono stage, and the best of the active designs
would be my more affordable unit. I spent a lot of time on number
14 and 15 since the cost to manufacture was half of all the rest.
In fact I spent 5 almost 6 weeks working with only those two. The
end result was a sound I was very happy with, one that had come
a long way with all the tweaking, but under adverse conditions and
with high efficiency speakers (100dB) the level of hum was just
unacceptable. Perhaps this is where some of that residual stress
came from :)
to make it happen, I started modifying the power supply with every
different form of regulation I could find. This journey took another
4 weeks of nightly work and I had the ripple down to 1/10th of 1
millivolt and there was still FULISDJFLKSDJFinG hum. AHHHHHH
I had some other units that were almost identical except for the
fact that they used a remote power supply, I moded one, number #5
to be an exact match and compared it. I did not however modify the
power supply with regulation. Without regulation btw, the ripple
was at 0.7 millivolts.
what, unit number #5 had no hum compared to this, and for the sake
of comparison none of the previous units has as much hum either.
At his stage of the game I would rather have eaten buffalo shit
than hear any more hum. Even though when the music played you couldn't
detect it, bla bla bla. My brilliant chassis design for number #15
was a failure, and the on board power supply was inducing magnetic
field hum into the circuit. Number #14 was even worse having 10
times the gain, and from time to time the damn things turned into
tuners and started playing a radio station.
couple weeks later I was ready to tally up the results and see where
I really was. Certainly just saying the hell with it was a clear
option. The thought of having customers complain about microphonic
tubes, hum and hiss scares the hell out of me.
brings us to the recent past, where a couple weeks ago I went in
the room and lined up all 15 units on the floor. I took them one
at a time and listened to each and weeded out anything that was
unacceptable from a noise standpoint. It would have been amusing
to watch, as I in less than 1 hour had created a reject shelf with
14 units on it.
is that during my diligent efforts with unit #14 and #15 I made
a magic discovery that took the performance of my active prototype
to a level that surpassed the best passive units. Unfortunately
it was at the cost of added noise and hum and I had to abandon it.
took the one remaining unit that was pleasantly quiet and had enough
gain in my hands and cradled it like it was my last chance. It really
did sound good, and I'm sure my customers would probably love it,
but deep down I knew it wasn't as good as some of the noisier units
I'd made. Then it hit me.. the magic discovery that didn't work
because of added noise may have been a side effect of the inducted
hum from the on board power supply, so I tried it again in unit
number #5. There was no added hum or noise, and the magic rushed
right back. Now that it was quiet, there was no question this was
superior to the passive units. It had better clarity, better focus,
better depth, and superior dynamics.
that brings us to the present time. Personally I have never worked
so hard on anything, but then I've never had such a good reputation
to protect before either.
final circuit in #5 obsoleted the passive designs in both sound
and gain so out the window was my idea of having two models. But
that's okay because #5 will be less expensive to build that my previous
designs for the signature model, and will drive a Zen without a
preamp making it most cost effective.
key features that make this unit special are as follows:
I designed it as well as the RIAA from scratch.
I designed the RIAA by ear rather than by spec. (Don't worry it's
very close - I did check it afterwards)
Parts count is at a bare minimum with .022 coupling caps allowing
for incredible speed
The input circuit has a variable impedance infinitely adjustable
from 3.5 ohms to 50K in 20 steps. That means any high output moving
coil or moving magnet will bring a Zen amp to full power, and even
regular lower output MC cartridges will work if the phono stage
is used with a preamp.(or a step-up transformer)
The input grid is decoupled with a capacitor that terminates on
the plate of a 3rd tube that has the heater series wired with the
other two tubes. The cathode and grid allowed to float. This puts
a small potential between the heater and the plate in relation to
the swing of the input signal. A fascinating result of this seems
to be a more relax and believable sound. I played with the screen
and cathode possibilities and got different results with each thing
I tried, like grounding the cathode for example. I preferred letting
it all float.
I have found some 12AX7's that sound so good I'm no longer sure
6DJ8's are a better tube in this application. Especially given the
fact that with 3 times the gain- a single tube per channel can do
the job offering the simplest circuit possibilities.
No hum, no hiss, no RF, no microphics and highly stable.
Dual mono - noiseless remote power supply with high reliability
Can easily be built under the $1000.00 goal
Perfectly drives a Zen amp without needing a preamp.
and circuit details will be available when the unit is released
for sale on this web site.
considering asking me to build a DAC can save their breath. I'm
taking a vacation, and the only thing that could possibly motivate
me to do such a thing now would be someone proving to me that CD's
(even superCDs) can sound better than LPs. When you hear this phono
stage behind a Zen amp, you'll understand how ridiculous that really