This review page is supported in part by the sponsor whose ad is displayed above

Reviewer: Paul Candy
Source: Rotel RCD-971 as transport, Audio Zone DAC-1, Pro-Ject RPM 5 turntable Pro-Ject Speed Box, Ortofon Rondo Blue cartridge
Preamp/Integrated: Manley Labs Shrimp, Audio Zone AMP-1, Pro-Ject Tube Box phono stage
Amp: Manley Labs Mahi monoblocks
Speakers: Green Mountain Audio Callisto (on sand filled Skylan stands), Hornshoppe Horns, REL Q108 Mk II subwoofer
Cables: Acoustic Zen, Audience, Auditorium 23, DH Labs, JPS Labs
Power Cables: Audience, GutWire, Harmonic Technology
Stands: Premier three-tier, filled with sand
Powerline conditioning: BPT Pure Power Center w/Wattgate 381 outlets w/ Bybee Quantum Purifiers and ERS cloth, GutWire MaxCon, Blue Circle BC86
Sundry accessories: Grand Prix Audio Monaco four-tier rack, Grand Prix Audio APEX footers, Isoclean fuses, Walker Audio SST contact enhancer, Nanotech Intron 8500 CD fluid, Audio Magic/Quantum Physics Noise Disruptors, dedicated AC line with Wattgate 381 outlet, Echo Busters acoustic room treatments
Room size: 11' x 18' x 8', long wall setup, hardwood floors with large area rug
Review Component Retail: Signature 70 $2,999/pr; iMod $199

The Red Wine Audio Signature 70 amplifiers are monoblock versions of the award-winning Signature 30 integrated unit Srajan reviewed last year. Riding shotgun for this review was RWA's iMod which is essentially a 4th generation iPod massaged by Vinnie Rossi into an audiophile-quality battery-powered digital source. With the amps and iMod, I was able to audition the complete battery-powered system shown above.

In his review of the Signature 30, Srajan referred to Vinnie as an audiophile Robin Hood coming to the rescue of price-conscious music lovers. I believe Vinnie is a far more subversive character than some dandy frolicking about in green tights. Don't let the cheerful nature and boyish charm fool you. Behind that clean-cut All American visage lays a shrewd revolutionary bent on convincing audiophiles to get "off the grid" as he calls it. Think Che Guevara minus the tousled appearance and gunfire. Vinnie believes today's noisy AC environment is a major impediment to optimum audio system performance. First, there's noise from other components, computers, appliances and the arc-welding shop down the road all sharing the power grid. Then there's the noise produced by diode rectification and magnetic field coupling from AC power supplies. And let's not forget the racket produced from the increasing use of switch-mode power supplies. Instead of buying pricey line conditioners and fancy wallet-busting power cables to combat this garbage, why not take a walk on the wild side and go DC? Matching a robust rechargeable battery power supply with the compact size and efficiencies inherent in Class T (Tripath) amplification would seem to be an ideal solution to the polluted AC grid. Sounds pretty subversive to me. Let's find out what gives.

The Signature 70s ship in the same compact black powder-coated aluminum chassis as the Sig 30. The rear panel features a single pair of high quality binding posts, a mini jack for the battery charger input, a power on/charge toggle, a single RCA input and a variable RCA output for biamping and subwoofers. The front panel sports a machined polished aluminum volume knob and a small LED indicating power status. A rather large 12V, 1,000mA wall-wart style SLA auto-charger ships with each amp. The Sig 70 outputs 70 watts into 4-ohm loads and 30 watts into 8. Input impedance is 20K. The two internal 12V 5Ah Sealed Lead-Acid (SLA) batteries connect in series (24V) when operating and in parallel (12V) when off/charging. Approximate weight is 12 lbs and the enclosure measures 12" W x 8" D x 3" H. Build quality and the accompanying owner's manual are excellent.

The Siggies would not make nice with my REL sub. Had I bothered to read the manual first, I would have noted the warning not to connect the amps to subs with speaker level inputs that have a common ground. Oops. Apparently this is common with Tripath and other Class D switching amps where the L and R speaker outputs are not tied together. However, Ed Schilling over at the HornShoppe has found a novel solution for this woofing conundrum. Head over to his site for the skinny. I haven't tried his "Magic Cable" yet but this could be the ideal solution for Tripath/Class D users who wish to strap on REL or similar subs.

Beefs? Other than my subwoofering issue, just one: the wall-wart chargers were so large that it was impossible to connect anything else into the same power duplex. The same would be true for power bars and surge protectors with conventional spacing. Keep in mind that you'll require two free wall outlets to connect the chargers. Apart from a polite 'pop' upon power up, the Siggies performed flawlessly over the three months I had them.

Cracking open the case to view the contents, you'll no doubt swear. "Dude, where the frick is my amp?" It's there alright, just tucked between the batteries on a tiny circuit board. As in the Sig 30, the mono brethren utilize the same Tripath TK2501 chipset, DacT CT2 stepped attenuator, hand-wound output filter inductors and point-to-point soldered solid-core OCC mono-crystal copper wiring plus a sizeable Jensen paper-in-oil coupling capacitor.

I asked Vinnie to offer some insight into the Sig 70 monos and how they differ from the Sig 30. "As you are probably aware, the Signature 70s are monoblock versions of the Signature 30 and the output stage is configured in paralleled output mode which means the Sig 70s can output twice the current. This is how it delivers a very clean 70 watts into 4 Ohms. The Sig 30's clean output into 4 ohms is approximately 40 watts.

Into 8 ohms, the Sig 30 and Sig 70s both output a very clean 30 watts. So while there is no power gain with the 70s into an 8-ohm load, I mention on the Sig 70s page that there are the following advantages over the Sig 30: Monoblock operation boasts complete separation of the left and right channels. Each channel is now powered by its own dedicated, high-current SLA battery supply. The volume control setting (or gain control setting if using an active preamp) of each monoblock amplifier can now be individually adjusted via the built-in precision stepped attenuator for balance control.

"Compared to the Signature 30, the Signature 70s feature improved bass response, soundstaging, stereo imaging and spaciousness. You will also find the upper midrange and top end to be a tad warmer. This distinctiveness is attributed to the monoblock operation, the separate power supplies, complete isolation between the channels and the change in the output stage circuit configuration (paralleled output mode)".

As for any concerns regarding the Siggies' charging regime, not to worry. Just plug the charger into an outlet, connect the mini plug to the amp, flip the rear toggle down to charge and then up to play music. There is no need to physically disconnect the charger. I got at least 20 hours of play on a single charge. Turn it on in the morning and flip it off before bed and you'll be good to go come morning. An LED mounted on the charger will glow red when charging and turn green when the batteries are fully topped off.

Regarding Red Wine Audio's iMod, Vinnie identified the following as the main offenders in holding back the iPod's audiophile potential:
  • The low quality stock SMT coupling caps after the Wolfson WM8975 DAC (used in all 4th gen. iPods)
  • Opamp output stage following the Wolfson DAC
  • The minuscule circuit board traces that travel from the top of the mother board down to the dock connector jack
  • SMD resistors and inductors directly in the signal path
  • The dock connector jack at the bottom of the iPod
  • The signal path inside the iPod dock, which contains: the dock connector plug, a very cheap ribbon cable, more minuscule PCB traces, SMD resistors and finally the line out jack

Vinnie's goal was to simplify as much as possible the analog signal path following the Wolfson chip. The mod connects the analog output (line out) straight off the DAC directly to the internal 1/8" headphone jack via Black Gate non-polarized NX-Hi-Q coupling capacitors. This modification service applies only to 4th Generation iPods which according to Vinnie sound superior to all other versions to date. Also be aware that the iMod converts the variable 1/8" headphone jack to a line-out jack. You'll need a volume-controlled headphone amp if you want to listen to cans now. The stock line-out from the dock connector is disabled as well. The output voltage is 1 Vrms.

I don't own a stock iPod so a shootout was impossible. However, the iMod performed better than expected. I used a Radio Shack mini adapter to connect the iMod to my own system and later to the Sig 70s. I ripped a few CDs in Apple Lossless for optimum sonics, then compared the iMod against my transport/DAC front end. Unfortunately, my Rotel/Audio Zone combo handily beat the iMod in detail retrieval, weight and dimensionality. Perhaps this wasn't an entirely fair fight as my DAC is considerably more expensive and has twice the output voltage of the iMod which make side-by-side comparisons tricky. On the other hand, the iMod was certainly quieter on playback and wasn't at all strident or bright. In fact it was quite smooth, with a pleasantly laid-back quality that was missing from any similarly priced digital player I've heard. After long listening sessions, I wasn't exactly in a rush to go back to my usual number-crunching rig. In terms of price, convenience and portability, I can't think of anything else comparable.

Over the course of my time with the Sig 70s, several new interesting recordings saw considerable action; Wire's classic Pink Flag [EMI 4M508m re-released by 4Men With Beards on 180g vinyl}; an excellent debut album by LA-based indie band The Broken West [Merge MRG289]; a swift, lean and smokin' Beethoven 9th from Osmo Vänskä [BIS SACD-1616]; avant-garde jazz/classical violinist Mark Feldman's What Exit [ECM 1928]; a brilliant recording of Piazzolla pieces by Canadian ensemble Les Violins du Roy [ATMA SACD2 2399]; and finally a highly entertaining disc of the 5th and 7th Symphonies [CPO 777 139-2] by the little known Czech composer Johann Wenzel Kalliwoda.

What immediately perked my ears upon powering up the Sig 70s was the completely quiet background. No hum, no hiss, nada. This should be a boon for owners of highly sensitive single driver speakers which ruthlessly reveal the smallest level of noise. The Siggies were definitely the quietest amps I've had in for review. It was a fascinating experience to hear music emerge so effortlessly from such a noise-free backdrop. And yet this quietude wasn't at all like the dry sterile aural black hole offered by many AC conditioners. They may curtail hash and glare but what they leave behind sounds like all the air has been sucked out of the room. The Sig 70s certainly lose the glare but somehow without adversely affecting the light and life of music. It's a quietude that doesn't overdamp.

With their utter lack of noise, the Sig 70s majored in detail retrieval. I got the sense that I was hearing all my recordings had to offer. The Siggies peeled back the complex layers of orchestral music not unlike peeling an onion, just minus the tears. I could concentrate on the scale of the event or zero in on individual lines and instruments. So many amps simply throw a massive wall of sound and leave it up to you to wade through the weeds. Not here.

Another key characteristic was the Siggies' extraordinary balance and natural way with music. Not one portion of the frequency spectrum stood out. There was no hash, glare, sharpness or exaggeration. Nor was playback thin or tonally bleached. The Siggies oozed a lovely relaxed warmth that completely belied their solid-state engine. However, you'd be grossly mistaken to interpret that warmth as over-gilding the lily. I got the detail plus the warmth. A near perfect marriage if ever there was one.

Imaging and soundstaging were well defined and spacious respectively, without exaggeration. The midrange was transparent and tactile, just missing that last degree of texture I typically observe with valve amps. The top end was smooth, sweet and ever so slightly rolled off which is okay by me as most modern equipment and recordings are too bright anyway. However, when I played music with considerable top end energy, I didn't feel I was missing anything.

The bass was full, rich yet fluid and agile but minus the unnatural über bottom end (or cyborg bass as our editor calls it) of most high power solid-state amps. The Siggies had a touch of tubey euphonic bass but without getting soggy or bloated. And don't think the Sig 70s are lacking in bottom end slam and extension due to their battery-powered engine. The Siggies have the moxy to do Led Zep or Wagner with plenty of testicular fortitude. Marry the slightly warmish bass performance with a smooth midrange, soft highs plus the complete absence of AC line noise or trannie hum and you have one serious recipe for a music-friendly system that possesses much of the lit-from-within sonics of quality tube amps.

If you're a tube head -- and I'm definitely a card-carrying member of that club -- I'm sure you will be impressed with how close these amps come to sounding like glass bottles. Having said that, tubes project a sense of rightness, tonal voluptuousness and drama that I just don't hear with solid-state, be it transistor, opamp, Class D or Class T. While the Sig 70s performed well on their own, I preferred driving them with my Manley Shrimp. With the active preamp, I enjoyed a little more weight, tonal richness and texture. This isn't to say the Sig 70s require a preamp. They don't. I did lose a little low-level detail retrieval and gained a tad higher noise floor but for me, this was a worthwhile tradeoff.

You can add an active preamp to tweak the Sig 70s' sonic flavor to your fancy or you can run them straight with the onboard DacT CT-2 attenuators. Depending on your partnering speaker load, you might prefer the transparency and speed of the naked Siggies over the enhanced weight and image density that a classic tube preamp might add. There is no right or wrong. It really depends on the speaker load and personal preference.

Compared to my opamp-equipped Audio Zone AMP-1 and from what I recall from the similarly priced AMP-2 monos, music via the Sig 70s emerged from a slightly warmer, more relaxed place. The Canuck chip amps were a tad faster, more incisive, with greater leading edge snap and jump. Not that the Siggies were lacking in the transient fidelity department. They weren't. We reviewers tend to exaggerate differences between components to better describe their sonic characters. I'd say the AMP-2s and 1s are more geared towards adrenaline junkies who get off on excitement, speed and jump factor. The Signature series are better suited for those looking for a slightly more relaxed, tonally warm experience coupled with an incredibly low noise floor and superior resolution of detail. In an email to the boss I opined, "One isn't better than the other, just different. The Red Wine is all Sunday afternoon while the Audio Zone is Friday night"

I had three pairs of speakers on hand to try the Siggies with; my GMA Callistos, a pair of JM Reynaud Twin Signatures and Ed Schilling's Horns. Over each, the RWA displayed a similarly warm and relaxed ease but without sounding muddy or bright. However, I thought combining the 70s with Ed's single-driver Fostex horns was the preverbal cherry on top of the double chocolate fudge sundae. Mating a vanishing low noise -- make that no noise -- amp with a single driver speaker minus any energy-robbing crossover was audio nirvana. Sonics were pure, direct and completely involving, with loads of tone color and punch. I know Omega's single driver speakers are also a great match with Vinnie's amps. In fact, Omega and Red Wine frequently demo together at audio shows. No doubt there are plenty more good matches out there.

A couple of readers enquired about matching the Sig 70s with the Mark & Daniel Ruby monitors. I was unable to try that combination myself. However, I'd be wary of matching a modestly rated amp with a demanding load such as the 3-6 ohm, 82.5dB Ruby. M&D recommend 80 watts into 8 ohms minimum.

The Red Wine Audio Signature 70 monoblocks are revolutionary products and among the more satisfying amplification components I have heard to date, tube or solid-state. They offer stunning detail without sounding analytical or sterile and possess a vanishing low noise floor. They confidently travel the neutral ground between solid-state and valves. Think of them as the audiophile version of Switzerland.

The iMod is a brave attempt at taking one the most successful personal electronic devices ever to a higher level of performance. Add it or Red Wine Audio's modded Olive Music Server to a pair of Sig 70s and you would have the foundation for a superb sounding, readily portable, minimalist system minus the usual snake pit of power cables and line conditioners. A little revolution now and then is a good thing, no?
Viva la revolución!
Red Wine Audio responds

Hi Paul,
I want to thank you and 6moons for such a fantastic review of the Signature 70s (as well as for experimenting with the RWA iMod as the source). You did a great job in covering the sonic signature of the “Siggies,” and the essence of the off-the-grid philosophy! I also enjoyed reading how you mixed-in some tubes in front of the Sig 70s as well as tested them with both single-driver and multi-way speaker designs. I agree with you that there really is no right or wrong approach here… and the Signature 70s work very well with (or without) active preamp as well as with many different types speaker designs.

I am also very pleased to accept one of the first Blue Moon Awards in 2007. Between that and very recently becoming a father, I can’t help being one proud papa!

See you at the Montreal FSI Expo in April,

Vinnie Rossi
President/Owner – Red Wine Audio, Inc.
Manufacturer's website