Let’s rewind the clock a bit to the 2010 Winter NAMM Show. In the midst of the introduction of the new (at the time) USA-built Heritage line and the first ever neodymium-based enclosures from Ampeg (the Pro Neo line), Ampeg also doled out two “new” bass heads: the SVT-8Pro (a monstrously powerful class-D head which saw limited production before the Loud Technologies acquisition, and was now being re-introduced as a Korean-built unit) and the SVT-7Pro (a “little brother” of sorts to the 8Pro).The Heritage and Pro Neo line attracted most of the attention (and between the two of them, earned Ampeg a Bass Gear MagazineBest of Show Award), and very little fanfare was given to either the 8Pro or the 7Pro.

I will admit that I was a bit preoccupied by some of Ampeg’s other offerings that year, myself, but I do recall liking what I heard of the 7Pro and thinking that it had a great feature set. We had decided early on that we wanted to review the PN- 410HLF, and the more we thought about it, the more we felt that the SVT- 7Pro would make a good match. Not only did this turn out to be a great pairing, but the 7Pro definitely impressed in its own right.

The King of Class-D Amps?

Ampeg is probably most commonly thought of for its iconic all-tube amps – the mighty SVT, the tone-machine B-15, and the “just right” V-4B. But Ampeg also made a name for itself in the world of solid state output sections, with the SVT-3Pro and 4Pro standing out as milestones. The SVT-8Pro is an engineering masterpiece, and one of the most impressive class-D heads I have played. But being “full-sized” (filling two rack spaces) and fairly expensive (North of $2,000), it doesn’t really fit into the trendy “micro head” market (downsized heads using class- D output sections and switch-mode power supplies, and typically coming in at well under $1,000). The Micro- VR fits some of these criteria, but wasn’t really designed to compete in this market, either. The newer PF-350 and PF-500 heads, however, certainly do position themselves well within this class, but it is the 7Pro which seems ideally positioned to bring the King of Amps into the crowded class- D/SMPS market.

Granted, it’s bigger (4” by 15.6” by11. 5”) and heavier (15.5 lbs) than most of the competition, but unless it’s critical that you can fit your head into the front zippered pocket of your gig bag, the SVT-7Pro is certainly small enough and light enough for most players. It definitely feels like a featherweight after hefting a fortypound SVT-4Pro, but when it comes to features and performance, the 7Pro is remarkably similar (on paper, at least) to the 4Pro. The front panel should be quite recognizable to most players who have used the Ampeg “Pro” heads, but might need some explaining to the neophyte. The single ¼” input sits next to an LED indicator that shows both clipping and mute status. The Mute button and the –15dB pad are next up, followed by the (optical) Compressor, with its own indicator LED, which shows when the signal is over the threshold limit and gain reduction is being applied. Next up is the Gain control, which is typical enough, but for those of you who have not spend much time gigging Ampeg heads, it’s worth noting that there are lots of great tones to be found with this knob turned up well past noon.

The Ultra Lo and Ultra Hi switches also warrant more than a cursory look.Leaving them disengaged allows the SVT-7Pro to dish out warm, somewhat mid-forward, vintage Ampeg tone with ease. Engaging the Ultra Hi introduces a 9dB boost at 8kHz, which is actually not so “ultra high” as to add more noise than musical content (which some high frequency boosting circuits can do).Ultra Lo does introduce a slight low frequency boost (2dB at 40Hz), but more noticeably, it also makes a healthy 10dB cut at 500Hz. This control is a real game-changer. The Bass and Treble controls are fairly straightforward, allowing +/- 12dB at 40Hz and +15/-20dB at 4kHz, respectively. The Midrange control takes a different approach. You can boost up to 10dB or cut up to 20dB at one of five different frequency centers: 220Hz, 450Hz, 800Hz, 1.6kHz, or 3kHz. All told, these controls add up to one very flexible EQ section. The front panel is rounded out by the FX Mix (serial effects loop blend control), the Master volume control, ¼” headphone out (which mutes the output section when plugged in), the power switch and power-on indicator LED.

The back panel of the 7Pro shows off some of its additional features: ¼” outputs are provided for tuner out, effects send and return, preamp out and power amp in, and footswitch control for both the Mute function and effects loop in/out. A pair of RCA inputs (“Aux In”) allow you to play a portable music device through the head (or just through the headphones) concurrent with the instrument input.This is a great feature for playing along and learning new songs, or just using your 7Pro (and an attached speaker) to crank out some jams! The fullfeatured, transformer balanced DI is tube-driven, and has all the controls you would want (pre/post EQ, -40dB pad, and ground lift). The pair of Neutrik connectors accept both SpeakonTM and ¼” cables, which is quite nice. A voltage selector switch, cooling fan, and IEC power input receptacle complete the package.

How Does it Stack Up?

As previously mentioned, on paper, the 7Pro appears to line up well with the 4Pro, so I decided that a head-tohead comparison was in order. But why stop there? I also had an 8Pro and a PF-500 on hand, so they were able to join in the fun. The first thing that I noticed was that these two heads sound a lot alike (as would be expected). The 7Pro was not quite as warm sounding as the 4Pro, but more defined. They both had a similar “burp” and “purr” to them, when coaxed. At the same Gain/Master settings, the 7Pro sounded much louder than the 4Pro (it is worth noting that I was only driving a single 4-ohm 4x10 for these comparisons), but I was able to crank the Gain on the 4Pro all the way up (even with no compression) without things getting too nasty. The same could not be said for the 7Pro, which seemed to get into the unusable range of saturation if you cranked the Gain beyond about 3 o’clock (without compression). I also noticed that as you turned the Gain up on both heads, audible preamp tube overdrive came on much earlier with the 7Pro. These differences could be the result of different tapers on the Gain pots, or possibly even variation among preamp tubes. Overall, the 4Pro seemed to offer a broader range of useable grit and grind.

While the optical compressors used on both heads appear to be quite similar, I again noticed differing behavior throughout the travel of the knob. On the 4Pro, there is not very much audible difference in the first half of the travel, but the second half makes up for it, and you can dial in anything from a subtle taming to brutal squashing. Conversely, the compressor on the 7Pro seems to do more early on as you begin to turn it up, but squashes the signal less at the highest settings.

Having basically the same tone controls on hand (not counting the 9- band graphic EQ on the 4Pro), you can dial in a similar range of tones on both heads. But whereas engaging the Ultra Hi/Lo on the 4Pro almost gave me the impression that it was fighting its basic character, the 7Pro seemed more at home with the transformation (and it is a major tonal shift on both heads when you engage these controls simultaneously). Adding both Ultras is like flipping a “vintage/modern” switch, though of course, you do have to EQ a bit in either setting (I found myself backing off on the Bass knob on both units when I engaged Ultra Lo). Hitting the Ultra Lo, but leaving the Ultra Hi off, brought the 7Pro fairly close to the tone of my Markbass LMII (though a “1/2 Ultra Lo” switch probably would have hit the nail closer to on the head). After playing around with the 7Pro in “modern tone mode,” at first it sounded a bit mid-heavy and “boxy” when I turned both Ultra Hi & Lo off, but after a few minutes, it sounds just right. In either “mode,” the SVT-7Pro was very impressive, making it a flexible option, indeed.

Bringing the 8Pro into the fray was interesting. It does not have a compressor knob, but does not seem to need one (perhaps some fixed compression going on?). The 8Pro is the most harmonically rich of the group (and packs the most preamp tubes), and definitely allows for the widest range of useable Gain settings.Cutting some of the subsonics with the Ultra Low (yes, Ampeg adds a “w” for the 8Pro) set to position 2 (Sub Cut) let me get even more drive without farting out. The Power Reduction feature on the 8Pro is supposed to allow you to dial in some tones similar to what you get from overdriving tube output sections. It is highly useable and very cool when the Gain is set below noon, but it tends to be a bit much when you are also dialing in some drive from pushing the Gain higher. The EQ section on the 8Pro differs from that of the 4/7Pro in a number of regards, and it seems to be well suiting to really fine-tuning the “vintage Ampeg” tone.

The PF-500 lifts its preamp section largely from the 7Pro, but without the 12AX7. It seems to have a bit more grit/grind at the same Gain/Master settings as the 7Pro. The compressor behaves very similar to that of the 7Pro, but seems to have less effect on the amount of overdrive that you can safely dial in. Tonally, it is very similar to the 7Pro, though the 7Pro is decidedly more full, smooth, and warm, and the added power is very apparent. The PF-500 sounds perhaps a tad brighter, and has a touch more hiss when you crank it up. Volume wise, the 4Pro, 7Pro, and 8Pro are all capable of delivering massive output.Each was able to drive my single 4x10 as hard as I would dare to push it. The PF-500 is no slouch, but clearly not able to keep up with its brethren.

The SVT-7Pro proved to be no less impressive in a gigging environment. I was able to play out with the 7Pro using several different cab pairings, and it did a great job each time. The power and dynamics I heard at “the shop” definitely translated to the gig. I was also impressed by its ability to get loud, without getting obnoxious.Sometimes I find that a given head has a very fine line between not being able to hear myself and having the guitarists jump down my throat for being too loud.With the 7Pro, I had no problems in either regard.

Pro Neo 410

Ampeg took their time when deciding to enter the neodymium-based enclosure market, and this has both advantages and disadvantages. On the plus side, they definitely set out to “do it right,” and they did so with the help of fellow Loud Technologies company, EAW (who specializes in manufacturing high-end professional loudspeakers). The three Pro Neo models (1x15, 2x10 and 4x10) are all designed and manufactured in the USA. The disadvantage of waiting to enter this market would typically be that your competitors who jumped in ahead of you may be able to establish themselves in the market first. This can be overcome with quality products from a strong brand name, though. The real cost of this delayed entry is that shortly after Ampeg announces its first line of neodymiumbased enclosures, China hits the world with the one-two punch of reducing the amount of neodymium it will allow to be exported, and increasing the price on what it does let out of the country. This issue is not unique to Ampeg, though, and the long-term impact on the market for neodymiumbased drivers remains to be seen. For now, these cabs are still available, and they are quite good.

Construction is topnotch, and the Pro Neo cabs have a spray-on “bedliner” style coating which seems to be fairly durable and is certainly quite attractive. Overall weight is fairly reasonable 64 lbs.Undoubtedly, Ampeg could have made this cab lighter, but it is clear that they wanted a sturdy, gig-worthy enclosure, and the PN-410HLF does seem to be built for the rigors of the road.

After comparing the PN- 410HLF to a number of different 4x10’s, it really struck me as a great blend of the big, round, meaty SVT-410HLF and some of the more bright/clear/articulate neo 4x10 competition.

Compared to an Epifani UL-410 (early Series 2), the PN-410HLF is more warm, full and balanced, while the Epifani is bigger/deeper, and also more bright. The TC Electronic RS410 is a closer comparison, but the Pro Neo is a tad more refined, with more clarity and separation down low, and more high end content. It is not quite as loud as the RS410, but the PN-410HLF is more controlled, and more balanced. The neo-based Bergantino AE410 made for an interesting comparison. The Pro Neo is more full, round, and warm, but not as scalpel-precise as the AE410. The AE410 is not only brighter, but also seems to maintain usable output deeper than the PN. The ceramicbased Bergantino HS410 was an even closer comparison than the AE410, with the HS410 being more precise and the Pro Neo having a touch more natural “growl.” Overall, though, these two cabs had strong similarities.On the whole, I would call the PN- 410HLF fairly dry & tight, but still full sounding; a hint of warmth, but still quite clear. It’s not easy to hit that particular compromise and do it well, but the PN-410 certainly does just that.Much like the SVT-7Pro, the PN-410HLF is well-rounded and versatile, and capable of delivering the goods whether you strive for a vintage vibe or more modern tones.

The Bottom Line

I am once again impressed with what Loud Technologies has done with the Ampeg brand. We discussed Ampeg’s past glory and future direction in greater detail back in issue #4, so I won’t rehash too much of it, here. But when you consider that Ampeg was the brand that people probably used the most often to demonstrate the advantages of smaller, lighter-weight rigs, to see Loud not only enter both the class- D/SMPS head and neodymium cab markets, but to do so with products that perform at the upper range of both markets is very impressive. The SVT- 7Pro has substantial output, sports an EQ that is both powerful and understandable, boasts a great feature set, and does it all in a relatively lightweight, sturdy package. The PN- 410HLF is designed and built in the USA, blends the best tonal attributes of vintage and modern cabs, and also does it all in a relatively lightweight, sturdy package.It would be easy for these two products to get lost in the shadows of Ampeg’s more iconic products. But they are both so darned competent, the SVT-7Pro and the PN-410HLF are each going to turn a lot of heads (and ears).

I am sure that all of you tech heads out there are familiar with “Moore’s Law.” For the unfamiliar, Moore’s law describes a trend in the computer industry where the number of transistors that can be placed inexpensively on an integrated circuit doubles every two years (approximately). As a nugget for you history fans, Moore’s law was coined around 1970 by a Caltech professor, Carver Mead, and is named after Gordon Moore, an Intel co-founder who described this trend in a paper in 1965. A lesserknown fact is that there are many other similar laws. Wirth’s law is the law of bloat. That is, successive generations of computer software acquire enough bloat to offset the performance gains predicted by Moore’s law (sorry, software guys). I could go on with other lesser-known laws, but the law I want to focus on today is what I am coining the “Hughes-Cox Law,” which is a multidimensional trend of SVT awesomeness over time.

Internal Construction

The SVT-7Pro test amplifier was possibly one of the easiest amps to disassemble that I have had on the bench. Moreover, the internal construction is masterfully done. A quick glance at the internals (Fig. A) clearly demonstrates that this amp line has steadily evolved since the inception of the SVT brand. The layout features a preamp section that is nicely shielded from the power supply and power amp sections. A daughter card hosts the back panel jacks. The preamp section hosts a nice blend of tube circuitry, holding a single 12AX7 tube, a Vactrol-based (optocoupler) analog compressor circuit, surface-mount components and nice, panel-mount potentiometers that feel smooth when turning (Fig. B). The main circuit board hosts the class-D output section and power supply.The result is a layout with minimal wire runs and a neat, intuitive organization.

Understanding the Amp

Referring to Fig. C, the SVT-7Pro includes a single input jack, and a switch for engaging a 15dB pad. From the input, the signal is split into two paths. A first path couples to a buffered tuner output. A second path couples to the input of the first tube stage.The output of the first tube stage couples to a mute circuit. As such, muting will not affect the tuner output. After the mute circuit, the signal passes through the compressor circuit. The compressor circuit utilizes a Vactrol for the gain control cell. The output of the compressor couples to a second tube stage for gain recovery. The output of the second tube stage feeds the Gain control, as well as the tone stack. Accordingly, the compressor should be thought of as appearing first in the chain of processing. The Gain and tone controls follow the compressor circuit. A compression control is provided to set the amount of signal compression, from no compression (fully counterclockwise) to 10:1 compression at the fully clockwise position. A threshold light illuminates to tell you when the signal has crossed the compression threshold.

The signal is processed by the Gain control and tone controls (Bass, Mid, Treble, Ultra Hi, Ultra Lo) in the same block. From the tone controls, the signal is passed to the effects loop. As such, the effects loop will always process the equalized, gain-adjusted and compressed (when used) tone. The signal from the effects loop feeds the Master control to the Preamp Out/Power Amp In controls. The Power Amp In feeds the class-D power amplifier section. The DI offers two options. The DI can take a pre-EQ signal, which is tapped before the compressor but after the first tube stage. As an alternative, the user can select post, which is taken right after the effects loop.

The Tone Stack

There are a lot of options with this tone stack, so let’s just jump in. With the Ultra Hi and Ultra Lo switches disengaged, and all controls set to noon, the full range 20Hz-20kHz frequency response shows a familiar mid scoop, slight bass emphasis and gentle treble roll off (Fig. D) with an overall deviation of +/- 10dB. Subjecting the amp to our “optimally flat” passband test of 80Hz to 8kHz, yielded an optimally flat response of +/-1. 6dB, compared to the “all controls at noon” response of +/-4. 6dB (Fig. E). For both measurements, Ultra Hi was switched on, and Ultra Lo was off. For the optimally flat response in this passband, set the tone controls as illustrated in Fig. F.

To see the effect of the Ultra Hi and Ultra Lo switches, we compared the full-range, all controls at noon, setting with both switches engaged, compared to both switches disengaged (Fig.G) . The Ultra Hi is capable of adding 15dB of treble boost centered around 6 kHz. However, the natural low-pass filtering of the tone circuit keeps this high frequency boost behaving more like a bell curve than a high shelf, which keeps hiss under control.

The Bass sweep is illustrated in Fig. H. The Mid sweep is broken down into two charts, where positions 1, 3 and 5 on the midrange dial are shown in Fig. I, midrange sweeps 2 and 4 on the midrange dial are shown in Fig. J and the Treble sweep is shown in Fig. K.

Output Power

On the bench, the SVT-7Pro tested well. At 8 ohms, we measured 457 watts continuous, with bursts reaching 483 watts.At 4 ohms, we measured 763 watts continuous, with burst reaching 914 watts. All tests at 5% THD+N, filtered 20Hz- 20kHz. The amplifier consistently output just shy of 48dB gain and a linear response in view of varying level (Fig. L). The amplifier burst response is shown in Fig. M. In this test, we deliberately push the amp into limiting, and this result shows the signal gracefully entering and exiting the limiter.

Conclusion

To challenge the Hughes-Cox Law, I looked back to our 1974 Ampeg SVT, reviewed in issue #4. If our math is correct, our test SVT7-pro sees an 83% reduction in weight, a 92% reduction in tube count, and a 185% increase in output power, compared to our ’74 SVT. The tests suggest that this amp performs like you would expect an SVT to perform. Yep, the SVT is alive and trending well. Now go forth and make music, no back brace required.

Designing a good “neo cab” is a good bit like designing a good “bass cab.” In fact, these two level of efforts should be identical. However, when a number of “neo cabs” hit the market, it appears that the “design” process involved nothing more than throwing some neodymiumbased drivers with similar specs into an existing (ceramic driver-based) enclosure design. Sometimes, this yielded surprisingly good results. Other attempts were not as fruitful. Ampeg took their time in bringing neodymium-based enclosures to the market, but looking at the Pro Neo line of cabs, it is abundantly clear that they did their homework and that they designed these enclosures from the ground up to be pro-level bass cabs (which just happen to use drivers with neodymium magnets).

From a technical perspective, there’s lots to like about these cabs. The overall construction has a “heavy duty” feel about it. The sturdy, slotperforated metal grill is held in place by ten screws. Each driver is held in place by four bolts (though there are holes in the speaker frames for eight). While I am happy to see bolts secured with T-nuts (wood screws can sometimes lose their grip if you have to pull or replace drivers more than a few times), I’d like to see more than four per driver. Case in point, one of the drivers only had three bolts installed, and one of the three looks like it stripped some of the wood when seating the T-nut (see photo).I will note, however, that this particular cabinet was the demo unit, so production run PN-410HLF’s are likely just fine in this regard. The horn was also held in place with bolts & T-nuts – very nice.

The sprayed-on coating has a moderate amount of texture, but is not as coarse as some of these “bedliner” finishes can feel.I like it.

The lack of corners does give it a certain stylish look, but I wonder if adding corners (say, small black metal ones) might enhance roadworthiness if you are gigging out a lot. Pulling one driver revealed cross bracing both front-to-back as well as side-to-side, and fair amount of acoustic insulation. Wiring runs were neat, color-coded, and appeared to use at least 18 gauge wire.

The frequency response was very balanced from 100Hz to 800Hz, with a slight bump around 1kHz, and a bigger peak around 3-4kHz, with a corresponding dip in between. Off-axis performance was not far off the mark at 15 degrees (1m out), but once you got more than 15 degrees off axis, results varied quite a bit (which is not unusual for a 4x10).

The PN-410HLF is a pro touring quality enclosure which takes advantage of the strong performance and lighter weight offered by neodymium drivers, but makes no compromises when it comes to durability or tone.