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FREQUENTLY ASKED QUESTIONS

with BC Audio founder Bruce Clement

Why those funny “octal” preamp tubes? Why not use 12AX7s like every other tube guitar amp on the face of the earth?

I certainly don’t have anything against 12AX7s. They - and other miniature or “peanut” tubes as they were called when they were new - have been used with great success in many classic amps. But I discovered that 6SL7GTs have a different sound - a really great sound. In a good circuit, these octals yield a thick, rich, power-tube-like tone that even the best NOS 12AX7s cannot match.

If you know power tube overdrive - or more accurately whole amp overdrive - you will recognize that crunch in these amps.


Why not use EL84s on your lower-powered amps, like every other lower-powered tube guitar amp on the face of the earth?

In my humble opinion, 6V6s kill EL84s. Eat 'em for lunch. Blow their doors off. Take 'em to the woodshed... I think you get the idea.

If you’re concerned about 6V6 squishiness or “farting out,” consider this: Premier Guitar said in their review of Amplifier No. 7, “6V6s traditionally suffer from a flubby bottom end. In this amp’s case there was none of that, just a pure and gorgeous saturated tone.”


What classic amps are BC Audio amps modeled after?

I put “non-clone” in the BC Audio tag line for a reason. If you want a faithful recreation of your favorite vintage amp - be it tweed, blackface, plexi, ‘Wreck or D-style - there are many choices in the marketplace. I wanted to create something different, amps with their own “voice.” Each one sounds like a great classic amp should, but not exactly like any particular classic amp.

Even the Octal-Plex Series amps are not clones or copies. The original Marshall circuits had to be modified and adapted for the octal preamp tubes. Original plexis did not employ true point-to-point wiring.

As Guitar Player said in their review of Amplifier No. 7, it “sounds like every amp you’ve ever heard, yet something all together different, with its own character and vibe.” All BC Audio amps benefit from this philosophy.


What is “True Point-to-Point” and why is it important?

True point-to-point just means point-to-point, which means the amp is constructed without the use of a circuit board of any kind. No turret board, no eyelet board, no printed circuit board. I added “true” because the original meaning of “point-to-point” has been lost, the term being widely but incorrectly used to refer to vintage and boutique amps with eyelet or turret boards.

Point-to-point wiring, done the way I do it, eliminates several feet of unshielded signal-carrying wire within the amp, thereby reducing noise, cross-talk, errant capacitance, parasitic oscillation and a host of other potential problems of conventional lead dress.

The bottom line is clarity. The physically compact and direct signal path brings a clarity to your sound that other construction methods cannot match.

Want to know more? Read this.


Do BC Audio amps work well with pedals?

Yes! BC Audio amps are very pedal-friendly. Slam the front end with your favorite dirt pedal or clean boost. Expand the sonic landscape with delay or reverb in one of the best loops in the business on Amplifier No. 9, No. 10 and the Octal-Plex Series.


Can they do clean?

Oh, yeah! Truth be told, I never set out to build a great clean amp. But I have had so much positive feedback from customers and the guitar press about the amps’ clean tones. The same factors that give BC Audio amps their great rock tones make for sweet, sweet cleans, too. You will find in all BC Audio amps an incredibly smooth transition between clean and dirty. It’s not either/or. There are whole worlds to explore in that clean/semi-clean/edge-of-dirty region.


Are they quiet, you know, when I'm not playing?

Yes. I hate noise. Hiss, hum, crackling - I hate it all! You will not hear bacon frying when you fire up a BC Audio amp. Even in a quiet room, you have to really crank it up before you'll hear any noise. Well, until you start playing!


Why put amps in an ammo cans?

Why not? Ammo cans are cool. They’re light-weight and compact. And they turns heads. An ammo can is the ultimate “lunch box” form factor. If it's not your thing, no problem - I offer the same models in traditional head boxes.


How did you come up with the ammo can idea?

The idea first came to me when I was a teenager back in the late 1970s. I was already building amps, pedals and other gear for myself and my friends. One day, I was in an Army/Navy surplus store and spotted a couple of the now familiar olive drab metal boxes. I thought, “Wouldn’t it be cool to build some kind of guitar gear in one of those things?” I didn’t even know what I wanted to put in there - amp, fuzz box, who knows? I just thought it would be cool.

Some years passed before I acted on that thought. In the mid-1990s I built a couple of prototype tube preamps in .50 caliber ammo cans. Later, to tame my big Marshalls, I built some attenuators in smaller .30 cal ammo cans.

I was working on an idea for my next ammo can tube preamp when it hit me: I didn't want a preamp, I wanted what my Marshalls and other amps were giving me - power tube overdrive. So, in early 2004, I began work on my first prototype amp in an ammo can. I gigged with that “test mule” for years, constantly tweaking it to perfection. In July of 2009 I unveiled the first BC Audio ammo can amp: Amplifier No. 7.

So, you could say Amplifier No. 7 was five years in the making. But it really is more than that. It is the realization of a vague but compelling idea sparked nearly 40 years ago.


On the ammo can amps, why is everything on the front panel? Why not put the power and speaker jacks on the back?

Several reasons:

- Flexibility. You can't set up your rig with the can sitting on its bottom (not the amp chassis bottom, but the ammo can bottom) if there are jacks there.

- Reliability. When the lid is on and you're carrying the thing around, do you really want to set it down on the floor/ground/parking lot with exposed jacks on the bottom? Sure, rubber feet blah blah blah. No thanks. Makes me nervous about damage and exposure to crud. Again, I built these things to be here a long, long time.

- Integrity. I want to maintain the physical and visual integrity of the original ammo can as much as possible.


Do the ammo can amps get hot? Why don't they have ventilation holes? Or a fan?

A fan? Are you kidding me? Sure, like all tube amps, they get hot. But they never get too hot to put out perfect, beautiful tone for hours on end.

During their development, I put prototypes through truly brutal stress and heat testing. They never broke a sweat. No burned parts, no melted iron, no weird noises, no fading. Just unchanging flawless operation under severe conditions for extended periods of time. And every single amp goes through a burn-in process as part of a rigorous Quality Control procedure. You should fully expect your BC Audio amplifier to last every bit as long as so many beloved 1960s workhorse amps have to this day.

As it says on the sticker inside the lid, "Case will get hot. Don't worry about it."


What is the difference between the 15w and 25w versions of Amplifier No. 7?

Nothing. They are the same amp, it’s just a matter of which power and rectifier tubes are installed. You can switch between 15 and 25 watts by swapping tubes. Please refer to the Tube Complement section on the Amplifier No. 7 page or the Owner’s Manual.


Can I get Amplifier No. 8 set up for 15 watts like No. 7?

Yes, you can. I don’t offer that option by default, because you already have the flexibility of having killer overdrive at any volume level via the Volume control. If you would like this option, just let me know.


What is the difference between Gain Boost and Volume Boost?

Amplifier No. 10 and the Octal-Plex Series feature two boost functions: a Gain Boost and a Volume Boost (optional on the Octal-Plex Series). Each boost can be independently engaged by the included foot switch.

The Gain Boost gives you more gain in the preamp section. More gain, more distortion, simple as that.

The Volume Boost gives you an actual increase in volume. As a gigging guitarist, I know the feeling of coming to my solo and no matter how much I slam the front end of the amp with a pedal, it just doesn’t get any louder. That’s where the Volume Boost comes in. When you hit that foot switch, your overall volume will increase, without changing your tone.


What is Depth?

Depth, found on Amplifier No. 9 and No. 10, is a control that tailors the low-frequency response of the power amp section, adding body and thump. Depth is similar to Presence, but it works on low frequencies.


Is your effects loop a good one, or does it suck tone? Is it compatible with my gear?

The BC Audio Effects Loop is one of the best in the industry. No, it does not suck tone, and yes, it will work with whatever gear you throw at it. Let me point out its major features and benefits:

Send Level and Return Level controls: Many amps’ loops lack these basic controls. These controls ensure that you won’t overload guitar-level devices (pedals) or feed studio gear a signal that is too low, resulting in increased noise.

Tube buffering: Buffering isolates the loop from the rest of the amp, so nothing you plug in will load down the signal within the amp.

Low impedance Send: Send is a low impedance source, so it will easily drive any pedal or rack effect without loading.

High-gain Return: There is enough gain in the Return circuit to fully drive the power amp from a guitar-level signal (pedals).

Non-inverting: The loop will not introduce any phase issues in a multi-amp rig or when mic’ing in the studio.

True bypass: The loop can be fully hard bypassed with the True Bypass switch on the rear panel.

Persistent Send: Signal is always present at the Send jack so you can drive other amps or go to a mixing board without the need to engage the loop (it can remain bypassed).

Pre-master section Return: On those amps with a master volume, the loop is placed before the master so signal levels to the effects remains constant and noise is minimized.


Amplifier No. 9 has an optional effects loop. Does it make sense to have a loop in a non-master volume amp?

It depends on how you use the amp, which is why I offer the loop as an option on Amplifier No. 9. The idea of a loop in any amp is to get time-based effects - chorus, delay, reverb - after the distortion-generating part of the signal path. It sounds much better to add reverb to the overdrive tone than it does to overdrive a reverb-laden tone.

If you tend to crank the hell out of the amp for power tube saturation, you will not get much benefit from the loop, as the effects in the loop are not after all of the distortion-generating parts of the signal chain. If you run the amp on the clean side, a loop can be very useful. The Return Level can even be used as a sort of Master Volume.


Can BC Audio amps run on European 220/240VAC power?

Amplifier No. 7 or No. 8 can be ordered for 240VAC operation.

Amplifier No. 9 and No. 10 have a line voltage switch for 120 or 240VAC.

All other amps are pre-wired for your region (120 or 240VAC).


Can I buy BC Audio amps with NOS tubes?

Aside from the NOS (new old stock) 5Y3 that I supply with the 15w configuration of Amplifier No. 7, all tubes supplied with BC Audio amps are new production tubes.


Can I install tube types other than those that come with the amp?

Preamp tubes: You may substitute a 6SN7 for the 6SL7GT in any position. This will lower the overall gain of the amp, much like substituting a 12AY7 for a 12AX7 in conventional amps. Generally speaking, the most noticeable change comes with swapping V1, the first preamp tube (refer to your Owner’s Manual and tube chart inside the amp enclosure).

Power tubes: Some substitutions are acceptable, some are not.

In Amplifier No. 7 and No. 8, 6L6s will work in place of 5881s. Only small-size 6L6 tubes will physically fit within the ammo can enclosure. Many 6L6 derivatives, such as the KT66, 6550, 7027 and 7581, as well as other popular power tubes like the EL34, KT77, KT88, can NOT be used because they draw too much heater current and may damage the power transformer.

In all other amplifiers, you may swap in any power tube type with the same pin-out (such as those I listed above), but you must check and adjust the bias for safe operation. If you don’t know how to do that, take the amp to a reputable tech for that service. The bias circuit has been designed to offer a wide range of bias voltage in order to accommodate a wide variety of tube types. Amplifier No. 9 and No. 10 feature individual bias pots to allow for setting the bias on each power tube independently.

Rectifier tube: In Amplifier No. 7, you may use a GZ34/5AR4 with 6V6s, but understand that the life of the 6V6s will likely be shortened. Do not use other rectifiers such as a 5AU4 or 5U4 in Amplifier No. 7 or No. 8, as they draw too much heater current and may damage the power transformer.

Do not use a solid state module in place of a tube rectifier, unless it is designed to emulate the rectifier you are replacing, in which case, why not just use the real thing? If you change the rectifier in Amplifier No. 9, JTX45 or JTX50, you should check and adjust the bias. If you don’t know how to do that, take the amp to a reputable tech for that service.


Do I need to set the bias when I replace the tubes?

In Amplifier No. 7 and No. 8, no. These models are cathode biased and designed to operate properly with a wide range of hot- or cold-leaning power tubes.

In all other BC Audio amps, yes, you must check and adjust the bias when replacing power tubes. If you don’t know how to do that, take the amp to a reputable tech for that service.

The preamp tubes never need biasing and need not be matched.


What does “Individual Output Tube Bias” mean?

In Amplifier No. 9 and No. 10, each output tube has its own bias adjustment inside the amp. This allows you (or your tech) to achieve closer matching than you can with a single adjustment. And you can even use un-matched tubes, an important consideration if you favor NOS, as matched pairs are much more costly than singles.

STILL HAVE QUESTIONS?

Give me a call at the number below, or use the contact form at the bottom of this page. I look forward to hearing from you.

   

BC Audio

San Francisco

415.310.3087


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Thank you!