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General Questions

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

Can I buy BC Audio amps with NOS tubes?

Can I install tube types other than those you specify?

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

Are BC Audio amps geared more toward humbucker guitars or single coil guitars?

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

Will they run on European 220/240VAC power?

Amplifier No. 7 Questions

What is the difference between the ammo can version and the head box and combo versions of Amplifier No. 7?

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

Is 15 watts loud enough?

Is 25 watts loud enough?

Does it have enough gain?

Can it do clean?

Why not EL84s? You know, like every other 10-36 watt guitar amp on the face of the earth?

Amplifier No. 8 Questions

What is the difference between the ammo can version and the head box and combo versions of Amplifier No. 8?

Is 25 watts really enough power? It is much quieter than a 50 watt amp?

Can I use 6V6s and a 5Y3 in Amplifier No. 8?

Amplifier No. 9 Questions

Is Amplifier No. 9 your take on a Marshall JTM45?

What is Depth?

Does it make sense to have an effects loop in a non-master volume amp?

How does the effects loop work? Is it compatible with my gear?

What does “Individual Output Tube Bias” mean?

Amplifier No. 10 Questions

Is Amplifier No. 10 your take on a 50w plexi?

What is Depth?

Why two boosts?

How does the effects loop work? Is it compatible with my gear?

What does “Individual Output Tube Bias” mean?

Ammo Can Questions

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

Why is everything on the front panel? Why not put the power and speaker jacks on the back?

How did you come up with the ammo can idea?

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General Questions

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

I'm certainly don’t dislike 12AX7s. They - and other miniature or "peanut" tubes as they were called when they were new - have been used with great success in so many classic amps, you can't argue with 'em. But, I discovered that 6SL7s have a great sound. In a good circuit, they yield a thick, rich, power-tube-like tone that even the best NOS 12AX7s cannot match. If you know what power tube overdrive sounds like, you will recognize that crunch in these amps.

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. If you really want NOS and don't already have your own stash, I can furnish you with them. If you already have your own stash of old glass, great! If you are new to NOS, I would suggest that you do a little research. Get a variety of opinions. Talk to NOS tube sellers, ask on the forums, read tube shootouts. In the end, everyone's idea of what is best will vary, and no one knows what is best for you except you. Which is why I don't offer an option to buy with NOS tubes by default. But, again, I can work with you on this - give me a call.

Can I install tube types other than those you specify?

For the preamp tubes, you may substitute a 6SN7 for the 6SL7 in any positions. This will lower the overall gain of the amp, much like substituting a 12AY7 for a 12AX7 lowers gain in amps that use those. You will get different results depending on which 6SL7 you replace. Generally speaking, the most noticeable change comes with swapping V1, the first preamp tube (refer to the Owner’s Manual). Please pay the extra cost for low-noise, low-microphonics tested preamp tubes. It’s worth it.

For the power tubes, some substitutions are acceptable, some are not. In Amplifier No. 7 and No. 8, 6L6s will work in place of 5881s, but many 6L6 derivatives, such as the KT66, 6550, 7027 and 7581, as well as other popular types like the EL34, KT77, KT88, draw too much heater current and may damage the power transformer. Only small-size 6L6 tubes will physically fit with the ammo can. In Amplifier No. 9 and No. 10, you may swap in any power tube with the same pinout (such as those I listed above), but you must check and adjust the bias. 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.

For the rectifier, you may use a GZ34/5AR4 in with 6V6s in Amplifier No. 7, 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 replacement 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, you must heck 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 Amplifier No. 9 and No. 10, you must check and adjust the bias when replacing tubes. If you don’t know how to do that, take the amp to a reputable tech for that service.

Preamp tubes never need biasing or matching. Yes, you should buy matched pairs of power tubes.

Are BC Audio amps geared more toward humbucker guitars or single coil guitars?

They’re not! I'll readily admit that I am a Les Paul guy. But I also play single coil guitars including Strats, Teles and my lovely 1956 Les Paul Junior, plus guitars with mixed pickups and coil taps. BC Audio amplifiers have a purity an clarity that brings out the character of whatever guitar you plug into them.

A little story: I was showing Amplifier No. 7 at a guitar show. I actually had more than one guy come back to my booth to test out a guitar they were considering buying from another vendor, because they somehow knew they would get a true and accurate impression of the guitar by playing it through Amplifier No. 7.

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!

Will they run on European 220/240VAC power?

Amplifier No. 9 and No. 10 have a voltage switch for 120 or 240 VAC usage. By special order, and for a small additional charge, I can build you a 240VAC version of Amplifier No. 7 or No. 8. Contact me.

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Amplifier No. 7 Questions

What is the difference between the ammo can version and the head box and combo versions of Amplifier No. 7?

Other than the power inlet and speaker jack locations - and of course the front panel cosmetics - nothing. The same chassis is used in the ammo cans, head boxes and combos. Same parts, same wiring, same tone. The only other difference is that the head box and combo versions have tube retainers.

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

Nothing. They are the same amp, it’s jut a matter of which power and rectifier tubes are installed. Please refer to the Tube Complement section on the Amplifier No. 7 page.

Is 15 watts loud enough?

Probably. Depends on your situation. In its 15w configuration, Amplifier No. 7 can hold its own playing blues or rock in a club, even if it's vocals-only-in-the-PA. If you need lots of clean headroom, or your bass player or drummer are just too damn loud, go for 25w.

Remember, you don’t have to decide now. The amp itself is the same in 15w and 25w configurations - it’s just the tubes that are different. You can always change them later. For a small additional charge you can have it both ways. Contact me for details.

Is 25 watts loud enough?

Again, probably. If you need more that that, you should probably mic up the amps. 25 watts may be louder than you think!

Does it have enough gain?

Once more, probably. Again, it depends on your situation. Amplifier No. 7 has about the same amount of gain as most classic non-Master Volume amps. If you need more gain than that...cool! Amplifier No .7 loves pedals. Pushing the front end with a dirt pedal or clean boost works quite well for leads or high-gain rhythm. I put some tips in the Owner's Manual about using pedals with Amplifier No. 7 or any non-Master Volume amp. Download the Owner’s Manual on the Amplifier No. 7 page.

Can it do clean?

Oh, yeah! I have had great feedback from customers on Amplifier No. 7’s clean tones. And the magazine reviews gush over its clean sounds. The same factors that give Amplifier No. 7 it’s amazing rock voice make it a sweet, sweet clean amp, too. And the transition between clean and dirty is incredibly smooth. It’s not either/or. There are whole worlds to explore in that clean/semi-clean/edge-of-dirty region.

Why not EL84s? You know, like every other 10-36 watt 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.

Now, 6V6s have a reputation for having a flubby bottom. So does my sister. (I don't have a sister.) Amplifier No. 7 does not have that problem. It has lots of good, strong low end, and the tone is thick thick thick. But it never "farts out" or gets week in the knees.

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Amplifier No. 8 Questions

What is the difference between the ammo can version and the head box and combo versions of Amplifier No. 8?

Is 25 watts really enough power? It is much quieter than a 50 watt amp?

You might think that a 50w amp would be twice as loud as a 25w amp. But it’s not. A 50w amp is exactly 3 decibels louder than a 25w amp. That’s not much.

The real beauty of a medium-power amp is that you can get the power tubes working, adding their own magic to the sound, without sterilizing the front row at the gig. If you want that sound, you gotta get the whole amp cookin’, not just the preamp.

Can I use 6V6s and a 5Y3 in Amplifier No. 8?

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.

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Amplifier No. 9 Questions

Is Amplifier No. 9 your take on a JTM45?

No. Amplifier No. 9 features a pair of KT66s and a GZ34 rectifier for 45 watts. But that’s where the similarities with the classic Marshall end. The preamp section is vastly different, not only because of the octal preamp tubes, but because of the basic architecture, lack of tone stack, the built-in variable boost, the Depth control and the optional effects loop.

What is Depth?

Depth 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.

Does it make sense to have an effects loop in a non-master volume amp?

The answer is, it depends. 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, such as chorus, delay and 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 as much benefit from the loop, as the effects in the loop are not after all of the distortion-generating parts of the signal chain. Nevertheless, the loop on Amplifier No. 9 can be quite useful and effective in many situations.

How does the effects loop work? Is it compatible with my gear?

The Effects Loop is tube buffered, meaning it is isolated from the rest of the amp by tube gain stages. So, nothing you plug into the Send or Return will load down the signal within the amp. Send is a low impedance source, so it will easily drive any pedal or rack effect. There is enough gain in the Return circuit to fully drive the power amp from a “guitar level” signal. Translation: It will work with your gear.

The loop is non-inverting, so it won’t introduce any phase issues in a multi-amp rig. And the loop can be fully hard bypassed with the True Bypass rear panel switch. 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). The Return jack can be used as a power amp input. Used this way, Return Level can be used a a kind of master volume. Lastly, for convenience, the signal connects internally from the Send jack to the Return jack if nothing is plugged into Return.

What does “Individual Output Tube Bias” mean?

That means that you can set the bias of each KT66 independently. Setting the bias of each output tube independently means that you can achieve closer matching than you can otherwise, since even matched pairs of tubes may be off by several mA. And you can even use un-matched tubes, an important consideration if you use NOS tubes, as matched pairs are much more costly than individual tubes.

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Amplifier No. 10 Questions

Is Amplifier No. 10 your take on a 50w plexi?

No. Amplifier No. 10 is a 50w 2x EL34 amp, but that’s where the similarities with the classic Marshall end. The preamp section is vastly different, not only because of the octal preamp tubes but because of the basic architecture, the location of tone stack, the two built-in variable boosts, the Depth control and effects loop.

What is Depth?

Depth 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.

Why two boosts?

Amplifier No. 10 features a Gain Boost and a Volume Boost. The Gain Boost gives you more gain in the preamp section. The Volume Boost gives you an actual increase in volume. Each boost is independently variable at the amp’s front panel, and switchable via the included remote foot switch.

The two boosts provide for four different combinations of gain and volume, much more than most channel switching amps. 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. You can dial in a little or a lot of Volume Boost, and when you hit that foot switch, your overall volume will increase, without changing your tone. The Gain Boost can be engaged for high-gain rhythm without blasting everyone out at your solo volume. Or hit both Boosts at the same time for a high-gain, boosted-volume solo tone.

How does the effects loop work? Is it compatible with my gear?

The loop is non-inverting, so it won’t introduce any phase issues in a multi-amp rig. And the loop can be fully hard bypassed with the True Bypass rear panel switch. 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). The Return jack can be used as a power amp input. Used this way, Volume, Volume Boost, Depth and Presence remain active. Lastly, for convenience, the signal connects internally from the Send jack to the Return jack if nothing is plugged into Return.

What does “Individual Output Tube Bias” mean?

That means that you can set the bias of each EL34 independently. Setting the bias of each output tube independently means that you can achieve closer matching than you can otherwise, since even matched pairs of tubes may be off by several mA. And you can even use un-matched tubes, an important consideration if you use NOS tubes, as matched pairs are much more costly than individual tubes.

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Ammo Can Questions

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.

Besides, consider the typical tube amp head. It is closed on the top, bottom, sides and front. On the back it may be somewhat open, or covered with a perforated metal panel. BC Audio ammo can amps are completely open on the front. That’s at least as good as partially open on the back.

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

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.

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 (pic, pic and another pic). Later, to tame my big Marshalls, I built some attenuators in smaller .30 cal ammo cans (pic).

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 (pic). I gigged with that “test mule” for years (pic), 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 over 30 years ago.

Still have questions? Contact me!

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