MC Phono Stage Review: Rogue Stealth Vs. Benz Lukaschek PP-1 (T8)

[mulveling]

Associated Equipment:

Sources:

SOTA Star Sapphire Seris III table

Fidelity Research FR64fx arm (Effective mass 20-22 grams)

Benz Micro Glider L2 cartridge (Low output MC, 0.3mV, medium compliance)

Merrill Heiloom table

Eminent Technology ET2 arm

Ortofon MC20 cart (Info on this is lacking, but IIRC I've seen an ad for this same cart in a magazine from the 1970's. What I read is very LOW output, very LOW compliance. I would guess an output less than or equal to 0.15mV, based on comparison to my Glider)

Phono Stages:

Benz Lukaschek PP-1 (pre-dates T9 version)

Rogue Stealth (version 2.0 circuit board, has a pair of AD 797 opamps)

Preamps/Headphone Amps:

Eddie Current Zana Deux

Headamp Gilmore V2

Headamp Gilmore Reference (single-ended version)

Power Amps:

McIntosh MC2100 (Vintage Solid State, recenty restored/re-capped, now hits hits 140 Watts/ch continuous)

Heathkit W4-AM (Vintage tube monoblocks, Williamson circuit, recently restored, 20 Watts, original Tung-Sol 5881 outputs)

Speakers:

Tannoy Dimension TD10 stereo pair

Tannoy Dimension TDC-1 center channel (used in a monoaural setup)

Benz Lukaschek PP-1

I've been using the PP-1 for well over a year now. My unit is an older "T8" version that probably dates back to at least 2000. The most current version is the "T9", which I have not heard. The PP-1 is a pretty little unit. The dimensions are roughly that of a reasonably stout remote control control, except it's in a fairly beefy chassis with a mirror-polished chrome finish. The unit is powered by a small wall wart transformer. That seems cheap, but later it became clear to me that it's a great idea to get that transformer as far from the unit as possible. The wall wart's cable hooks into the side FURTHEST from the input jacks, which also is a very good idea. Metal accents are gold, and the RCA jacks look nicer than average. Gain is fixed at 62db. Input impedance (loading) is fixed at 22,000 ohms. With its fixed gain, the PP-1 is only usable with low-output MC cartridges.

On my SOTA table the PP-1 provides the kind of sound I crave, in spades: liquid, smooth, dynamic and resolving, with holographic imaging, all in one. This setup still draws me in to the music more than any digital source I've ever heard - by a significant margin compared to redbook or digital files, and by a smaller margin compared to SACD. I originally bought the PP-1 because it seemed wise to pair my Glider cart with its matching Benz phono stage. Indeed, this is a lovely partnership. Last year, the PP-1 beat out a Dynavector P75 (mk I version) in my setup. The P75 sounded quite good, but the PP-1 provided a slightly smoother, grain-free listening experience. This may be a consequence of the opamps used in the P75, but that's purely speculation. The PP-1 has provided me with solid, trouble free operation and gorgeous sound quality since it arrived. The current MSRP ($1750) on these things is IMO ridiculous for such a small, simple box. Fortunately the older T8 versions are often heavily discounted and can be had used for a very reasonable prices (~$600). That brings it into striking range of the so-called "bargain" stages with MSRPs < $1000 (like the P75 and Rogue Stealth), which are usually only lightly discounted on the used market due to the buzz/hype surrounding these units.

The only problem I've had with the PP-1 is its lack of loading options. Benz's spiel is that this was done to keep the signal path clean: "This elimination of unneeded circuit junction points preserves the low noise/high performance characteristics of this superb phono preamp". The PP-1 input/loading impedance has been fixed at 22,000 ohms - this is much higher than optimal for many non-Benz low MC carts. In fact, the loose rule of thumb is that you should be loading your MC cart with 20x-30x the coil impedance. Since most low MCs have a coil on the order of 5-15 ohms, you're usually looking at a loading of 100-450 ohms. When you load an MC cart too low, you can get treble rolloff. When you load too high, you can (though not always) get a nasty resonance spike in the treble. It must be that Benz low MC carts are designed in a way such that a high loading impedance doesn't bother them.

At the time I acquired my Merrill/Ortofon MC20 setup, I didn't have a 2nd phono stage - this necessitated sharing the PP-1 between two turntables. As the MC20 has a coil impedance of only 5 ohms, the PP-1's fixed loading became a pressing issue. Indeed, the MC20 at 22K loading sounded very clean and detailed, however there was a slight hardness to the treble, the bass was too low in proportion to the spectrum, and the overall sound could be a bit fatiguing over time. Armed with a cheap soldering iron, some nice parts (Vishay resistors, DH Labs hookup wire, nice RCA jacks), a few Radio Shack plastic project boxes, and a crudely untrained hand, I set out to make a few different resistor boxes to achieve lower loading settings with my PP-1. Each box was a simple setup: 2 pairs of RCA jacks, signal-to-signal and ground-to-ground with the hookup wire, and a single metal film resistor shunt from signal-to-ground. The box would be placed between the turntable and phono stage, necessitating an extra pair of RCA interconnects. The resistor acts in parallel to the PP-1's 22K impedance, and by Ohm's Law: 1/Rc=1/R1+1/R2, where Rc is the acting cumulative resistance and R1,R2 are the paralleled resistances. Since 22K is much higher than the resistors I'd be using, its effect on the cumulative is small enough to be inconsequential (hence the load is determined by the value of the resistor I choose). I tried various resistors for 1K, 470, 100, and 50 ohm loads. To my ears, the 100 ohm load struck the best balance. The 50 had too much treble roll-off, and the 470 load sounded closer to 22K than to 100.

Later, I returned to the local hifi dealer (Audio Atlanta) where I had bought and auditioned the Merrill/MC20 setup. It had sounded truly sublime then, though to be fair it was driving the $14K Tannoy Kensington speakers. I asked the shop owner what phono stage & loading he'd used during my audition - to which he replied: "the [Rogue] Stealth @ 100 ohms, those old Ortofons like 100 ohms". It was nice to verify that my ears were right about the 100 ohm loading! I looked up the specs of the Stealth - it was an opamp based design but it had 3db more gain than the PP-1 (65db gain vs 62) and load settings for 100, 300, and 1.1K ohms. I though the extra 3db would be nice since the old MC20 has such a LOW output - it sounds MUCH lower than my 0.3mv Glider. It must be lower than 0.2mV, but might even be lower than 0.15mV (it sounds at least 6db lower, which would put it below 0.15). I also liked having the flexible load settings - my resistor box worked, but it required an extra set of interconnects and another go at the soldering iron if I wished to change from 100 ohms. I figured a total solution like the Stealth might be better and would grant easy flexibility down the road. Hence, I found a local Stealth for sale and arranged to pick it up last week.

Rogue Stealth

The Rogue Stealth is housed in a more traditional hifi component-sized box, though it's less deep than usual. Nothing particularly stands out about the chassis design, but it sports a look and feel that gives the impression of a higher-than-average quality. I've noticed Rogue always gets this aspect right with their gear. No frills, reassuringly heavy/solid, quality fit & finish with a decent overall aesthetic. The Stealth I've acquired should be a fairly recent version. The circuit board lists "Version 2.0" and uses a pair of nice AD797 opamps.

At first listen, the Stealth had a very clean, pleasant sound quality. However, further listening revealed certain issues. At first, I noticed a moderate noise floor of the "ground loop hum" variety. The hum increases with the preamp/headamp volume knob and becomes noticeable right around the range of my "loud" listening levels, during silence or very quiet passages in music. Not a big issue, but the PP-1 is clearly quieter. It MUST be because they put that damn power transformer in the same box. The box is fairly long, but still not long enough to truly get it out of the way. This was not an issue with my placement of the phono interconnects near power cords, because I'd discovered that issue earlier and now make sure my low-level phono ICs are kept as far away from power sources as possible.

The second issue was more insidious. At higher volumes on headphones, I noticed a distortion during certain dynamic peaks. It sounded somewhat like a soft clipping, sort of like when an output tube is over-driven into a low impedance headphone (toaster SDS w/ full 6sn7 complement into Grado hp2, in my experience - well, maybe not quite THAT soft a clip ). I first noticed it consistently on the drum thwacks on the track "Kimberly" from the Patti Smith "Horses" reissue vinyl. Then more of the same on A-ha's "Hunting High and Low", again on drum thwacks. I was using the HD650 and Headamp Gilmore Reference. I noticed the distortion suddenly appeared at a particular volume step (moderately high level) and then rapidly worsened at steps past that. This would be consistent with amplifier hitting its power limits, however I KNOW the Gilmore designes can push FAR beyond these levels with clean power. More of the same was observed on the Gilmore V2, in fact with no music playing I could hear that the hum noise itself started to distort and break up at the last 1/4th turn of the volume knob!

I swapped in the Zana Deux, and the distortion was gone, even at high levels! So next I put the Gilmore back in, and swapped the PP-1 phono in place of the Stealth. Distortion...completely gone! All I can guess/speculate is that the high noise level, and possibly the nature of said noise, is not playing nice with the fully DC-soupled design of the Gilmores. The Zana Deux with its capacitor-coupled outputs was immune (again, pure speculation).

By now, it was the end of the Stealth's time in my system. Even ignoring the noise & distortion issues, the PP-1 is sonically superior. It's bit more liquid, a bit more unrestrained. Better 3D imaging, and better at presenting a lifelike realism & energy with superior dynamics and a palpable weightiness to the sound. This finding holds for BOTH of my turntable setups (assuming the 100 ohm resistor box was used with the MC20). I hopped on audiogon that night, found a PP-1 ready for the taking at a nice price, and snatched it up! Actually I'm not even sure if it's going to be a T8 or T9, but I'm just fine with another T8. I'll have a PP-1 to drive each setup, now. At used prices, it's a phono stage I can highly recommend for low-output Benz cartridges, or for other brand cartridges WITH the caveat that you may need some resistors to bring down the loading from 22K.

Benz Lukaschek PP-1 Pictures:

PP-1 solo - it's hard to keep clean:

PP-1 all hooked up, yes my shelf has scratches

PP-1 internals:

PP-1 in SOTA/MC2100/TD10 system - to the victor goes a SHELF (...I really need to dust under the SOTA):

Rogue Stealth Pictures:

Stealth front:

Stealth front closeup:

Stealth back:

Stealth inputs/outputs closeup:

Stealth internals:

[DigiPete]

Nice review!

The PP-1 looks like it might wound better since it uses discrete topology,

vs. the cheaper opamp topology of the Stealth.

A Pass ONO or XONO would sound really good but a bit pricey. The Whest .20 or TWO might be very good too.

The Pass Pearl DIY also sounds fantastic, but only 60db gain (might be too low for your cart).

[DigiPete]

Nice review!

The PP-1 looks like it might wound better since it uses discrete topology,

that's 'sound' better

[swt61]

where are the wallwarts?

Those are in a separate case. It's too big to fit in the picture.

Nice review Mike.

I agree with DigiPete about the DIY Pearl.

[mulveling]

Yep, the PP-1 has a small external wall wart to keep the power transformer far, far away from the low-level phono signals. However, in my case, the 2 halves of its plastic outer shell are held together with a strip of electrical tape. I know you guys appreciate cutting-edge technology like that

[mulveling]

I received my 2nd PP-1 today. It's the newer T9 version that retails for $1750

Got this one off agon for $590 - what a deal! Now the plan is to put the T9 in the main stereo/headphone rig and relegate the T8 to the mono/bedroom rig. The T9 sounded just fabulous today. I'll wait and see what longer-term impressions bring. I also added some Audioquest King Cobra & Jaguar ICs to my system, also sourced cheap off of agon/ebay - nice looking, well built cables. That plus a recent re-arrangement of components, keeping the phono ICs further away from power cords & PSUs, has dropped the noise floor down to negligible levels.

Net result is that both systems are just bangin' - really delicious sonics here. The Gilmore Reference is proving to be a killer preamp for its endless transparency; these days I'm even preferring it to the Zana Deux in that capacity with vinyl as the source (and I usually hate dealing with stepped attenuators). Looking forward to much listening in the upcoming weeks

[Smeggy]

Nice review, however, my eyes and interest still get drawn to that old 2100.