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Amps and Pedals: When Gain is not Volume

July 4th, 2017
Keeley D&M Drive with boost Boost and Drive

Keeley D&M Drive with boost Boost and Drive

Here is a typical scenario: Guitar player in local bar band is playing along through a song, and now it’s time for his/her lead. The player hits his stomp box or gain channel and POOF: Where did the guitar go? Instead of standing out, the guitar fails to cut through, and sounds like and angry beehive, lost in the mix.

This is not an uncommon occurrence. Players mistake gain for distortion, or expect to get more gain and just get more distortion. It’s understandable, as on amps and pedals the terms gain, volume, drive and boost all get used quite interchangeably. But generally speaking where you apply the gain in your signal chain will determine whether you are creating more volume, more distortion, or possibly just a bunch of mud.

In a simple non-master volume amplifier, the volume control increases gain at the preamp level. The power amp section  is a fixed amount of gain. Whatever the preamp feeds it, the power amp section boosts it “X” amount. In this layout when the amp distorts, it’s the power amp tubes clipping. Unless your amp is 15 watts or less, this is pretty hard to do at reasonable volumes. This why some studio players like small low powered amps like the Fender Tweeds, old Supro’s, etc.

Master Volume amplifiers come in many shapes and sizes but most of them have some way of overloading a preamp tube (or tubes) and creating the distortion at the preamp level, and then using a second volume control (the master) to keep the overall volume level in check.

Any type of distortion causes clipping, which compresses the signal (reduces its dynamic range). The more distortion, the more the signal is compressed, producing a very even signal but with less ability to cut. Everyone has noticed how a clean guitar tone cuts through the band better than a heavily distorted one. The uncompressed dynamic range of a clean signal has a lot to do with it. Or if you use recording software, notice how much more peaky a clean guitar signal is than a distorted one? Clean guitar is much harder to track.

Let’s say you are on the dirty channel of your master volume amplifier, so you are already creating preamp distortion. If you hit a boost pedal feeding more signal into the amplifier, the effect is often to overload the preamp section even more, creating more clipping and compression. Distortion increases, but relative volume goes up very little or not at all.

Even if your “boost” switch is part of the guitar amplifier’s footpedal system, where the boost is applied will determine whether you get more volume (post preamp) or more distortion (in the preamp section). Pedals can do the same thing: If you pump a distorted pedal signal into a signal path that is already compressed, you are just layering distortion on distortion, further crushing dynamic range.

The concept of a “good pedal amplifier” is an amplifier that has enough headroom (clean gain capability) such that you can feed in boosted and distorted pedal signals without significantly overloading the amplifier. In essence the guitar amplifier is amplifying whatever you send in, but adding little or none of it’s own distortion.

A “bad” pedal amp would be a small Fender Tweed. They have so little headroom that any type of signal boosting device would just overload both sections of the amplifier, creating mush. At the other end, a Fender Twin or 100 watt Marshall can take a hot input signal without distorting, and have enough power to amplify that signal to very high decibel levels. If you listen to Angus riff on most AC/DC songs, it’s not heavily distorted, it’s just really loud. And it’s got great dynamics, bite and texture. Angus does not use any distortion pedals.

There are 15-30 watt amplifiers that are good pedal amps, and it has much to do with amplifier design, transformers, and tube selection. To generalize, a fixed bias amplifier tends to have a good amount of clean headroom (Blackface Fenders, many Mesa amplifiers) while a cathode bias amplifier may have great tone, but can be less forgiving to hot signals (Fender Tweeds, Vox, many Dr. Z EL-84 amplifiers).

Tubes matter too. While the 12AX7 preamp tube is by far the most common, the EF86 tube (some Dr. Z, 65 Amps, Bad Cat, etc.) has more gain and clean headroom potential. They also sound different than a 12AX7, but they handle pedals very well.

The fixed bias EF86 Dr Z. Z-28 makes a good pedal amp.

The fixed bias EF86 Dr Z. Z-28 makes a good pedal amp.

My own personal preference is to find a single channel amplifier with decent headroom and really good clean tone — pedals won’t make a bad amp sound good — and then go with pedals for overdrive and distortion. Real power amp distortion is awesome, but in a gigging situation where a lot of different tones/colors are needed, pedals are just more convenient and easy to modulate. If you are in a blues band and can put your Tweed on 10 and ride the guitar volume, it’s a great sound. But if you are in a wide-ranging cover band, the pedal-based format is more effective and flexible. For the record I don’t like feel or tone of attenuators, and feel it’s best to pick the right size amplifier for the job. Unless I’m outdoors I don’t play an amp bigger than about 20 watts.

You should also consider the order of your pedals. If your clean boost pedal is before your primary distortion pedal, it will increase distortion and some amount of volume. If it’s after your primary distortion pedal, it will increase volume more effectively with little increase in distortion. Arranging your pedals with an eye towards how they will interact can greatly increase their effectiveness.

If we go back to the hypothetical guitar player at the beginning of this post, think about some of your favorite blues and classic rock guitar leads. Quite often they are not wildly distorted, but there is a lot of texture, dynamics, and the personality of the guitar player comes through. Managing volume versus distortion can improve the quality of your lead work, and help it stand out better in the mix. I’m not talking about playing “clean” but that crushing amounts of pedal or preamp distortion can really suck the emotional life out of a guitar. Music is all about dynamics, and making sure your guitar does not vanish at that crucial moment can make or break the emotional impact of the song.

 

Cool Amp Find Vol. 4 – Fender Deluxe Reverb Electric Blue

July 2nd, 2017

Fender-Blue-Deluxe-smallThe Fender Deluxe Reverb is hardly rare, and there are literally thousands out there: Vintage, new, Blackface, and Silverface. You can spend $750 for a nice used Blackface reissue, or $2000+ for a pre-CBS (1965) vintage unit. Even in the “bad era” of CBS, the circuit remained largely unchanged. So if you must have the Real Thing, a 60’s Silverface is essentially the same.

We pickup up this particular model in trade. It’s circa 2008, but was pretty much new-in-box, wrapped in plastic. The Electric Blue model differs from a garden-variety reissue by virtue of the blue tolex, a premium set of matched Groove Tubes, a limited edition name plate, and a British-made Celestion Blue speaker.

This particular Cool Amp Find is more about my ignorance and prejudice about the Fender Blackface sound than it is about the rarity or greatness of the Fender Deluxe.

I’ve dabbled in early Fenders — Pro Reverb for example — both true Silverface and Blackface. While I have not owned a Twin, I’ve had plenty of contact with them. I was always hit with the same impression: Too hard, too stiff, and too loud. Given that Fender was making amplifiers that “worked” prior to modern PA systems, there was no environment where I ever got into the sweet spot of these amplifiers. A Pro Reverb on “6” is crazy, a Twin on six is fatal.

It turns out that my problem was not Blackface, it was that I was using the wrong amplifier.

I have now learned what countless other guitar players have already figured out: The Blackface Deluxe Reverb is probably one of the most perfect guitar amps ever. Loud enough on stage to match the drummer, enough headroom to handle pedals, but supple enough to get natural tube amp grind. Plus it’s easy to carry, and there is no shortage of parts, mods and tweaks.

While I’ve not experienced a non-Celestion Deluxe, I like the warm early breakup and strong low end of the Celestion blue. By nature I’m a constant tweaker, but we’ve had a lot of gigs lately and all I’ve had time to do is drop in a Mullard GZ-34 rectifier and a longer speaker cable so I could use my Radial JDX box for the PA. I’m toying with the idea of a Mojo Pine Deluxe cabinet to cut a little weight and give it a little warmer vibe.

But overall I love it, and I feel silly that it took me this long to discover the DR. It works well with single coils and humbuckers, and it makes perfect sense that backlines everywhere are littered with the Fender Deluxe. It’s now my #1 gig amp, and unless I’m outdoors, I don’t need anything bigger.

Given the great tone and portability of the Fender Deluxe, whether you purchase new or used, it’s killer value. If you don’t need channel switching, built in effects (other than Reverb or Vibrato) or modeling, I can’t imagine anything better in this price range. And if you really want hand-wired splendor, you could probably purchase a used Deluxe and have someone do a turret board conversion for less than a new boutique amp.

Sometimes in the chase for ultimate tone, we ignore simple solutions that are right under our nose. The Fender Deluxe is simultaneously mundane and also just what I’ve been looking for.

Here is a demo video of a G&L guitar, using our Fender Deluxe Reverb. The player is Berklee instructor Scott Tarulli. There are no effects other than light compression and reverb. The gain tones are the Deluxe Reverb on the normal channel cranked up:

https://www.youtube.com/watch?v=WJFtFlAbdn4

 

 

Cool Amp Find Vol. 3 – Down Brownie Amplifier

March 31st, 2017
down brownie

Down Brownie 6G3 from Cutthroat Audio

While the past two “Cool Amp Finds” were out of production used amplifiers, this amp is available new right now. Ron Westwood of Cutthroat Audio has come up with the Down Brownie, a very cool totally portable amplifier that is an expertly crafted reproduction of the 6G3 Fender Brownface, but also much more than just a copy.

The 6G3 Brownface is a “transitional” amplifier that came between the Tweed and Blackface era. Putting out about 15 watts and using a fixed bias 6V6 circuit, the Down Brownie is the type of amplifier that just begs you to crank it up to around “8” and manipulate the various shades of semi-clean to dirty with the guitar’s volume control. Pedals? It’s really not the same. To get the classic sound of a small amp turned up, you really do need a small amp turned up. The Brownie has the tactile push-pull nature between the guitar and amplifier that makes it feel like a living, breathing organism rather than an assemblage of wires and components. No matter where you are on the guitar’s volume control the tone is natural, deep, and satisfying.

But Ron did not stop there. The amp also features tube or solid state rectification, three selectable levels of negative feedback, a post phase inverter master volume (on the back), Mercury Transformers, and an Alnico Weber speaker.

We would also be remiss if we did not mention the vibrato circuit. It’s just dynamite, and can add a subtle depth that you can just leave on all the time, or a deep pulsating warble.

The biggest departure from the 6G3 is that the “normal” circuit has been replaced by a “British” circuit. Rather than just having the normal channel be a drier version of the vibrato channel, the tone stack has been voiced and located similar to a small Marshall amplifier. Also, when you pull the volume control it jumpers the two channels. Oh yeah, pulling the tone control is like a bright/defeat switch. This channel is a little bright for my taste (and so are small British amplifiers) but in jumper mode it gives the Brown channel a nice edge.

All this tweaking potential would not matter if the core tone of the amplifier was not as good as it is. The Brownie has a warm, rich “brown” tone that is similar to Tweed Deluxe, but in my mind less raspy with smoother highs and tighter bass your average small Tweed clone. If you want the Neil Young on-the-verge-of-meltdown tone, stick with a Tweed, but to me the Brownie feels more put together.

If you can’t part with your pedals or want ample clean headroom, the Brownie is probably not for you. You can mic this amp for a gig, but if you need true clean volume, this is not the Brownie’s strong suit. But for shades of clean-ish that you can easily push over the edge, the Brownie is a wonderful creation that weighs less than most people’s pedalboards.

 

Interesting Amp Find Part 1 – The Mesa Stiletto 50W

October 22nd, 2016

mesa-shotI would normally categorize myself as a “less is more” person when it comes to amplifiers. I tend to favor rather simple amps, usually single channel, and use a couple pedals. Most of the time I’m using a Dr. Z Remedy, but also have a Bassman, a Custom Vibrolux and as of recent a Mesa F50 (the next blog topic).

But along comes this Mesa 50W Stiletto that we took in trade. I once had a 100w/50w Lone Star Combo, and it shares a lot of the options, knob assignments and tweaking possibilities. So even though I have never played a Stiletto, I somewhat knew my way around it.

This amp was Mesa’s answer to the Marshall sound, and as such sports EL-34 power tubes, a Plexi/Bassman style circuit, and a sealed cabinet with a Vintage 30 speaker. It has the Mesa “spongy” switch that drops the amp voltage for more touch response, and the ability to switch between tube and solid state rectifier (individually on each channel). Also like many Marshall amplifiers there is no reverb.

Initial impressions of the amp was that it was extremely bright and tight. On regular power and solid state rectifier, this amp as very little give, and if you’re a “spongy” amp guy like me it’s a little disconcerting. But between the tube rectifier, the spongy switch, and the three position “character” switch for each channel, there is something for everyone.

I like EL-34’s, and they have a very complex and harmonically rich top end. This helps the Stiletto pump out some awesomely good clean tones. By running on spongy with the gain and master around noon, and using the tube rectifier, it’s not hard to get some sweet touch-induced tube crunch. The amp also has an overall level control, and you can get these tones at reasonable volumes. But if you want your own personal Twin, run it on solid state rectifier and full power and you’ll have ample clean headroom. It’s likely that if you ask a typical Mesa player how they like their clean channel they’ll say, “I don’t know.” The Stiletto has a clean channel worth knowing.

The gain channel is naturally quite bright (like a Marshall) and don’t be afraid to twist the tone controls to tone it down a bit. But once you have it dialed in, it’s got some amazing Brit-crunch that has overtones and character out the wazoo. The sealed back cabinet helps to tighten up the sound, and the enclosure is not a parallel box, we assume in order to reduce standing wave forms. The total gain potential is end-of-days crazy, and we can’t imagine a usable scenario. But if you like tight, harmonic crunch you can cut with a knife, it’s freak’in awesome. You can’t model this….

Drawbacks? The Stiletto combo must weigh around 70 pounds, so it’s a good thing it has casters. Also the Vintage 30 has an inherent midrange spike, and some EL-34 tubes are likewise, and we found the standard Mesa power tubes were a bit too forward in this respect. We are using some groove tubes that we like, and if we can find some Winged C’s we’d probably be really happy. We also tried a Warehouse Reaper HP in the Mesa, as we’ve like the Reaper in the past. We could not get it out of the cabinet fast enough. Just goes to show that Mesa really does engineer the amplifier, and you can’t just stick anything in there. Same with pre-amp tubes: They are not easy to get at, and just leave the Mesa tubes in there. If you can find a NOS 5U4GB, go for it.

I sort of thought that we’d move this Mesa along as soon as it came in the shop. But it sounds awfully good, and we’ve taken it on gigs where we don’t have to haul it up stairs. On cleans it comes close to our beloved Dr. Z. Remedy, and it can break up a lower levels. If you don’t want to bring any pedals and just use the gain channel — and if you can open it up — it’s other-worldly.

The Stiletto does not really EQ or respond like your typical Mesa, and in that respect it was probably somewhat misunderstood, and underappreciated. But it’s probably our favorite Mesa so far, and highly underrated. They are out there anywhere from $800 to $1300 and represent a true bargain.

Guitar Amplifiers – How Many Watts Are Enough?

October 28th, 2014

If you’re an active guitar player, you’ve certainly noticed the continuing trend towards smaller, lower powered amplifiers. This has occurred for a number of reasons: Popularity of boutique clones of early amplifier designs, older players downsizing to focus on playing at home rather than performing, and the advent of very good affordable sound reinforcement systems.

Historically, the first guitar amplifiers were pretty small because the guitar was not necessarily the lead instrument of the band, and in many cases the band itself was not amplified. Plus the technology of the time – tubes – dictated smaller low power systems.

As rock music and the electric guitar became more popular, both the volume levels and the size of the venues increased. But true high quality “house” sound systems like today did not exist. So the guitar amplifier was not for “tone”, but was also the primary vehicle for what the audience heard. Amplifiers also did double or triple duty: Check out the input panel of many early amplifiers and you’ll see input jacks for multiple guitars and microphones. Adjusted for today’s dollars, pro gear back in the day was vastly more expensive than now, and sharing was a practical necessity.

So like the Space Race, the power race was on, and by the end of the 50’s the larger guitar amplifiers were pushing 50 watts or more. Fender’s introduction of the blackface amps in the early 60’s addressed the need for louder, cleaner sound. The blackface amps differed from their tweed predecessors in a number of ways, but features such as fixed bias design, higher plate voltages, and solid-state rectification had more to do with volume and headroom than tone. The largest amps topped out at 100 watts, which is really the practical limit of four 6L6 or EL-34 power tubes. This is pretty much true today for tube amps, and anything more than that gets very heavy and hot (bass players had it tough then). Today a bass player can get a 500-watt Class D solid-state amplifier that’s the size of a phone book.

But back then if you were going to play an arena, you needed stacks of amplifiers because they were doing a lot of the heavy lifting. Plus it’s kind a macho thing and looks really cool too. Today, you can play an arena with a 15-watt amplifier, and some performers do. While there is a certain visceral sensation to the sound of a 4×12, the need for a row of Marshall stacks is essentially visual. And unless you’re Yngwie Malmsteen, many of those cabs on stage aren’t even on.

So how much power do you actually need? Unless you require extremely high levels of clean volume without the assist of a PA, 50 watts is the most you’ll ever need. How much volume an amplifier produces is a function of its design: Fixed versus cathode bias, amount of negative feedback, plate voltage, rectifier type, etc. It’s hard to generalize, but a 15-watt amplifier with no negative feedback and a solid-state rectifier can be very loud and clean. My main amp head has (4) 6V6 tubes, solid state rectifier and a 20/40-watt switch. The only time it’s on 40 watts is when the band is playing outside.

If you are playing clubs and typically put the guitars through the PA, 15-30 watts will likely do it. While early amplifier designs were guided by power output, choosing an amplifier today is more about how you want it to sound, rather than how loud it will go. If you play mostly at home or jam with friends, 10-30 watts is where a lot of the amplifier market is targeted these days. Finding the right amount clean headroom – which is important if you use pedals – is an important selection criteria. If you regularly jam with a drummer, 30 watts is probably a better choice than 10. Five-watt amplifiers can be fun, if all you want is loose, old school grind. But with a humbucker-equipped guitar, there will be little in the way of decent clean volume.

Many modern amp designs have the ability to vary total amplifier output. Some do this by actually dropping out power tubes (4-to-2 for example) while others vary the amount of voltage to the power tubes or phase inverter. These features cut volume as well as headroom, allowing the ability to clip the power tubes at reasonable volumes. The Traynor Ironhorse amplifier has a fixed/cathode bias switch that changes the output of the amp from 37 to 17 watts, respectively. This not only affects total volume and headroom, but also the feel (I like the softer nature of cathode bias).

If you have a large amp that you don’t want to part with, there are of course power attenuators, which are available as an add-on accessory. These work by absorbing some of the energy that would normally go to your speakers. In effect, you can crank the amplifier but the attenuator “soaks up” some of the energy (volume). Attenuators work by placing some type of resistance/inductance network in the signal path to the speakers. Without getting technical, even the best ones mess with the feel of the amp, and how the guitar interacts with the amplifier. It’s hard to explain but it’s a disconnected feeling. They sound good on YouTube, but so does everything. My suggestion is to buy a smaller amplifier.

The trend towards lower stage volumes, and the affordability of good sound reinforcement and monitoring systems has been a boon to amateur and pro players alike. Using a guitar amp as the sole amplification source is very rare, and your band will actually sound better if you turn down and let the PA and the monitors do their job. And your band mates will appreciate it. Which brings us to the guitar player’s favorite lament of “I can’t hear myself.” Which is a topic we’ll address shortly.

 

The Fender Bassman Amplifier – The amp for almost everything?

July 5th, 2012

Preface: Never say on the internet that anything is ever the “best” or you will be hounded by email, gear pages will convulse with derision, and internet servers will glow incandescently straining to handle the volume of traffic proclaiming your incorrectness. So in this post I will completely avoid the term “best’ and merely relate one’s own experience with a particular amplifier.

This story started several months back when my brother Neil called up and said “Hey, I found this really nice amp, you want to go in halves with me?” It seems that our friend Dan Neafsey of DGN guitars had acquired a Fender Bassman Ltd in a trade and wanted to sell it. This is the “nice” reissue of the Bassman with a pine cabinet, GZ34 rectifier and (4) Jensen ALNICO 10″ speakers. It’s very much like the original Fender 5F6 schematic except of course for the printed circuit board, non-carcinogenic capacitors and a 3-prong plug. And it doesn’t cost eight grand. On top of that, it’s a rare “relic” version with some nice mild aging to the tweed, and some faux cigarette burns on the topside. Some find the whole relic thing pretty cheesy, but it looked good and the aging was tastefully restrained. Lastly, Dan had ditched the circuit board and done a point-to-point Mojo Guitar Works conversion with some nice high grade components. So not wanting to turn down a brother in need, I sent him some bucks via PayPal and the deal was done.

At this point I should say that my brother lives about 130 miles away, so half ownership is kind of like joint custody: When do I get to see it, how often, and what about weekend visits? However, Neil also does most of the major work on my car. As luck would have it, it was time for a new timing belt and I headed off to Connecticut with my car and a DGN Tele®.

There are a couple guitar players at the repair shop where my brother works, so there is usually some gear hanging about the garage. They literally have a garage band. Shortly after arrival, my car was on a lift in one bay, and in the other bay was the Bassman warming up, along with a LP Junior, the Tele and a couple pedals.

The garage is a high-bay affair with decent acoustics, and any amp tends to sound pretty big in there. But the Bassman was just on another level. Diving in with the Tele, the Bassman had a wonderful combination of slightly spongy twang, deep full bass, and a room-filling presence that made a typical 1×12 combo sound strangled and puny. This puppy really breathed; and the interaction of some rectifier sag and four little speakers huffing and puffing in a pine box created a connection between guitar and amp that was more mechanical than electrical. Each note had a beginning, middle and end that was totally musical, with a broad projection and sense of texture that you could almost reach out and grab. Open tunings and drop D on the Tele created shivers and silly grins all around. I was hooked.

As I drove back I realized that our mutually arranged weekend visits with Bassman would not do. But what now? There are not any shops around me with cool gear — except maybe mine and I sure didn’t have one — and I was not going hit up Guitar Center hoping to get lucky. So with few other options it was off to the “Magic Devaluator” of all merchandise: eBay. I got lucky almost instantly, and there were three used Bassman Ltd’s with the right specifications all bidding in the $700 – $900 range. So for a little over $800 shipped I got a very clean Bassman Ltd with a couple light scuffs, mint condition cover, and even the glossy cardboard piece they put over the top with the all the sales promo stuff and suggested amp settings. From what I can tell, it’s not really used at all. To finance this, I sold my real ’67 Pro Reverb for close to twice that and came out ahead on the deal, sonically and financially.

Whenever I get a new amp, the first thing I try to do is make it “better”. I hauled out some NOS tubes — Bugle Boys, GE’s, RCA blackplates —  talked to my brother about what he experimented with, and so forth. The amp came with the original Groove Tube/Fender tubes including the USA-made Groove Tube 6L6 ‘s. However, except for substituting one of my NOS 5V4 rectifier tubes that I got from KOS (oddly, rectifier tubes do sound different), nothing really sounded better than the original tubes. Clearly the Jensen speakers sounded great, so I was not going to touch them (plus Neil already tried that and said don’t bother).  Fender had done their homework: The Bassman really needed nothing, and any effort to improve it’s sound took it the wrong direction. Lesson learned.

I experienced a similar phenomena with whatever guitar I plugged into it: The tone was good off the bat, with very little tweaking of the knobs. I tried a lot of guitars: Les Paul’s, an Archtop, various G&L’s, a Rickenbacker, and even a Godin Multiac Nylon string. No matter the guitar, it was never a total “do over” with the EQ. Just maybe a slight tweak of the bass or treble and I was off and running. I would have never imagined bringing my G&L and a Rickenbacker to the same gig, but with the Bassman it might just work. And I’m just talking EQ: I have not even mentioned that the Bassman has a bright and normal channel,  each with hi and lo inputs, and you can jumper the inputs to use both channels at once.

I was flabbergasted: All these years I have been messing around with amplifiers, and it never once occurred to me to try a Tweed Bassman. Now I wonder why they aren’t more popular. To some degree the great popularity and legend of the Blackface amplifiers led me to believe that this style of amp was the holy grail of tone. After trying and failing with a few real Blackface Fenders, I discovered in a roundabout way via a ValveTrain Trenton that the Tweed tone really suited my style. Between the Bassman and my Dr. Z Remedy, I’ve pretty much got things covered. Which I guess means that I’m really a Marshall fan because the Remedy is based loosely on a Plexi (but with 6V6 tubes) and the Bassman is the basis for the JTM45. My whole amplifier belief system has been upended by the Bassman.

There may be some perfectly good reasons not to want a Tweed 5F6 style Bassman. You might find that an amp that looks like a big brown suitcase is the wrong look for you, your band, or your peers. I suggest you get over that one, and just have them listen to it or look the other way. Or, that a 4×10 amp is too heavy and bulky. The amp is a little boxy, but the pine cabinet and ANILCO speakers keep the weight down to around 50 pounds, which is way less than any tube 2×12, and even some tube 1×12 combos (If size and weight are truly major concerns, check out the ValveTrain Trenton for a  vibe that’s close, but in a smaller package). You might also be rightly concerned that a Tweed design amp won’t handle pedals or high gain very well. While this is generally accurate of the Tweed genre, the Bassman was intended to handle a bass guitar signal, and therefore does have pretty good headroom, and it’s 50 watts. I find it works pretty darn good with pedals, although if truly high gain rock/metal is your thing, then you will look silly playing a Bassman, and you are free to purchase the large ominous-looking black box of your choice. But if your styles include blues, roots, indie and a good dollop hard driving rock — think  JTM45 — there is no reason a Bassman and a couple well chosen pedals won’t get you there in style, and at reasonable volume levels, and set you back less than a grand. Plus you can finally bring your Rickenbacker to the gig.

Guitar Amps: Tube or Solid State Rectifier?

January 26th, 2012

When shopping for a high quality tube guitar amplifier, one of the potential decision points along the way is whether to purchase an amplifier with a tube or solid state rectifier. What does all this mean, and does it matter?

Vacuum tubes are powered by high voltage DC (250 – 500 volts) while the power coming out of the wall in your house is 120 volts AC. To convert AC voltage to DC voltage the AC alternating current is rectified into DC current. Back in the early days of tube amplifiers the only way to rectify voltage was to use a special type of vacuum tube called a rectifier tube. By the early 60’s electronics had advanced to the point that solid state silicon diodes had become an affordable alternative to tube rectifiers. A diode allows current to flow only one direction, and a simple “bridge” of four diodes is a cheap and reliable way to rectify AC into DC.

From a pure cost standpoint, silicon diodes are very attractive to the manufacturer. They are cheap (pennies really) and they rarely fail. They also produce a very “tight” output, and a  power supply with a solid state rectifier is very stable and consistent. And it does not generate any heat to speak of.

In comparison, a tube rectifier requires the tube (dollars not pennies), tube socket, additional wiring, and a more complex power transformer with a special tap (output) to power the tube rectifier. There is also more variation in tube performance than diode performance, and in general a tube rectified power supply is “looser” and it’s actual output will vary more in relation to demand.

The “Sound” of Solid State versus Tube

Besides being a cost advantage, solid state rectifiers provide a “stiffer” power supply to the power tubes which results in more headroom with less distortion. The famous Fender Twin Reverb Amp has always used diodes to provide loud clean sound. An 80 watt amp would overwhelm  the power handling capacity of a single tube rectifier, and diodes were pretty much the only way to go. Certain Fender Bassman designs used two tube rectifiers in parallel to share the load and provide better headroom and cleaner sound. If this sounds somewhat like a Mesa Boogie “Dual Rectifier” you are absolutely right. For a 100w or 150w head, two or three rectifiers in parallel are the only way to provide tight punchy sound without going solid state. So in general solid state rectifiers are associated with cleaner, tight, punchy sound with good headroom. And they help keep costs down.

Tube rectifiers has certain characteristics that are deeply ingrained into the Mojo of tube amps. When faced with a strong power demand (striking a big chord or picking very hard) the voltage output of the tube will actually “sag” or drop in voltage. This results in a softer note attack and maybe a little clipping or “hair” around the notes. As the note decays, the voltage comes back up and “pushes” the note giving the effect of a slight volume swell and more sustain. When players refer to an amp as “touch sensitive” it is this effect of the rectifier tube sagging and swelling with the notes, and responding directly to the player’s style. Low wattage amplifiers with tube rectifiers have a nice spongy feel, warm sound and soft clipping that many players love. With all the boutique builders furiously cloning Champs and Deluxe’s it’s clear that this type of tone has some hard core followers.

Is Tube the only “true” path to Sonic Bliss?

If you need a lot of volume, clean headroom, or really like a tight low end to your sound, an amp with a tube rectifier may not be your cup of tea. Folks who like metal or hard rock need not apply, although Boogie has made a real name for themselves with the Dual Rectifier. Of course having two rectifiers sort of defeats the purpose, but it’s great marketing. Even if you really like that softer  attack and early clipping, you don’t have to have the extra expense and maintenance of a tube rectifier: Just play a smaller amp! If you are playing a 50 watt amp for jamming or in clubs, chances are it’s too big. Even 30 watts may be too much. Big amps were designed prior to pro audio and commercial sound systems. The big 100 watt amps of today are matters of testosterone and showmanship. Nobody needs that back line of amps — OK maybe Yngwie Malmsteen does —  it just looks awesome.

I really like the spongy feel of a fairly low powered tube amplifier. A nice 20 watt amp with a 5AR4 rectifier playing through a 12 or a couple 10’s has great feel and character. And it will handle most club gigs with no problems at all. It may lack a little punch, but this type of setup gives the player great control over the texture of the notes. However, after saying all that, my #1 go-to amp has a solid state rectifier. But it’s still only 20 watts (on half power) and the overall sound quality and touch sensitivity is still there because it’s sized right for the task. There is so much to amplifier design, transformer design, and component selection that picking an amplifier on strictly one aspect — it “must” be Class A for example — just does not make a lot of sense.

Early amplifier builders used tube rectifiers because they had too. If affordable silicon diodes existed in 1950, they would have used them instead, and we would have never known the difference. But tube rectifiers have that tribal folklore attached to them, and for some there can be no other way. They can add a lot of character to the sound of an amp, but like many other “must have’s” a tube rectifier is not instant guarantee of goodness. In the end, buying on sound quality and choosing an amplifier that is sized appropriately for your needs is the best strategy.