Amp For Both?

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I'm sort of a newbie about acoustic guitar amps and was wondering if any of the ones on the market are suitable for both acoustic AND electric guitar. I'd like to have Loz mic and phantom power capabilities for my acoustic guitar but enough power and a heavy enough speaker for my electric when I play with my oldies duo using backing tracks. My present guitar amp which works just fine is a BOSS Katana 50 (12") but it would be nice to have one amp that would do both. The Katana has an 'acoustic' setting of sorts but no XLR input or phantom power.

That's something I'm really having a hard time making my mind on!
Which one do you prefer? Finger or picked acoustic blues?

Personally I'm a big fan of the pick. Simple reason, I'm coming from the electric Best Blues Guitars 2019 – Reviews and Top Picks .
On the other hand, finding lessons and acoustic blues played with a pick is harder!

I really like seeing someone play with his fingers, delta style but I can't even play a simple rhythm, I'm finger ******ed.
I also love acoustic blues played with a pick... Boogies, etc...

Is this something you had to work on a while to get?
Should I start learning finger style on it's own and then learn finger style blues?
 
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I do not see why a guitar amplifier can not reproduce an acoustic guitar. The speaker may need a crossover and a high frequency speaker but the amp when run cleanly should be up to the task. The question is at what output level. Of course a guitar amp will put out a higher SPL with an electric guitar than a clean acoustic.
 

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I've not worked much with "acoustic" guitar amps.

I do remember Dave playing jazz cello through a Fender Twin. To a point it was just louder with a little boost in the bottom and in the zing. Of course when he leaned into it it could bark (nicely).

That was a l-o-n-g time ago and there must be better techniques.

I don't think it is a fundamental problem any more. Classic e-amps were simple and nasty. Today there is much interest in "Modeling Amps" which is a clean/flat amp plus DSP emulation of 99 classic e-amps. I *assume* there is a setting which would be appropriate for "acoustic" sound.
 
Boss Katana 50 or 100.
I'll second that. And add that I have a Katana 50, and it is an excellent guitar amp both for electric, and for acoustic. It's the first solid-state electric guitar amp I've ever actually liked.

I've used the Katana 50 with my electric guitars at dozens of small jams and one on-stage performance (a friend with a band invited me on as a guest.) I've used the Katana with my Yamaha electro-acoustic several times, including at an outdoor farm jam this last summer.

Like Dotneck335, I did not think it was possible to combine a really good electric guitar amp and a really good electro-acoustic guitar amp into one. But I was wrong, as my Katana 50 proves.

The trick is probably internal electronic EQ, that voices the amp quite differently for electric and acoustic modes. Roland (Boss is part of Roland), with their long history of making electronic keyboards and pianos, knows a thing or two about applying EQ to speakers to make them sound different. They have to, to get acceptable sound out of the tiny built-in speakers in some of their smaller electronic pianos and keyboards!

Many acoustic guitar amps also have a microphone input, so that you only need to lug around one box for one guitarist and one vocalist. The Katana 50 doesn't have a mic input, and IMO this is the only real deficiency it has as an acoustic guitar amp.

Come to think of it, the Katana 50 does have a little 1/8" input jack for MP3 tracks, etc. If you use an external mic preamp, and an adapter to a 1/8" stereo male plug, it might be possible to get both vocals and guitar through the Katana 50. I haven't tried it, and it certainly isn't as convenient as having a proper mic input built in.


-Gnobuddy
 
You do not get much dispersion of highs with a 12" speaker. Otherwise I do not see why you could not use the Katana. It really depends on your location and expectations. Where will you be using it, how loud does it have to get, how many people? With other instruments?
 
...The speaker may need a crossover and a high frequency speaker...
I thought so too, but then I found a very interesting article by Craig Anderton: Better Sound from Acoustic Guitar Piezo Pickups - Guitars - Harmony Central

I've attached the EQ curve Anderton used to make the onboard piezo preamp in a Gibson acoustic guitar sound more like a microphone placed in front of the same guitar. Note that the bass is rolled off heavily below 160 Hz, and the treble is rolled off heavily above 3 kHz!

So it appears the usual electric-guitar speaker may actually have all the bandwidth necessary for acoustic guitar. It definitely doesn't have the right EQ curve, though, so that will need to be fixed in the electronics. My guess is that this is exactly what's done in the Katana 50 and 100.


-Gnobuddy
 

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You do not get much dispersion of highs with a 12" speaker. Otherwise I do not see why you could not use the Katana.
Agree about the dispersion. Worth consideration, though: an actual acoustic guitar has pretty bad treble dispersion, too! It's annoyed me for years that when I'm playing acoustic guitar, I'm hearing a much duller sound than anyone sitting in front of me and facing the guitar.
Where will you be using it, how loud does it have to get, how many people? With other instruments?
The outdoor summer farm jam I mentioned caught me by surprise; I was told it would be small and quiet, and I should show up with just my acoustic guitar.

When I got there, there was a small improvised stage of sorts, a P.A. system with pole-mounted speakers, and a bass player setting up his 500-watt Fender Rumble 500 bass amp. Every other guitar player who'd showed up had brought a guitar amp. :eek: And the audience was scattered on the grass in front of the stage, in a roughly circular area maybe 50 yard (15 metres) in diameter, ringed by tall pine and spruce trees.

Fortunately I'd brought along my microphones, mic stands, Acoustic AG30, which I used as a wedge monitor so that I could hear myself sing, and my Katana 50, which I used to amplify my guitar. And a small suitcase-full of audio and mains cables. :)

There was no drummer, mercifully. Even so, I was really impressed with the Katana 50. This was the first (and so far, only) time I used it on its 50-watt setting, and it was loud enough to hold it's own with the bass and other amplified guitars.

Remember, this is sold as a little practice amp. I bought it to use in my living room, and at small indoor jams with no drummer. I never expected to be using it outdoors, or with an audience at that distance, and I never expected it would actually do a good job under those circumstances.

Every once in a long while, a consumer product comes along that really is head and shoulders above the competition. IMO, the Katana 50 is one of those rare products. It's a very impressive little amp, for a variety of reasons.

I'll add that I have no connection whatsoever with Roland or Boss, and I don't benefit in any way from the sales of Katana amps. I'm just a surprised and impressed customer.


-Gnobuddy
 
I thought so too, but then I found a very interesting article by Craig Anderton: Better Sound from Acoustic Guitar Piezo Pickups - Guitars - Harmony Central

I've attached the EQ curve Anderton used to make the onboard piezo preamp in a Gibson acoustic guitar sound more like a microphone placed in front of the same guitar. Note that the bass is rolled off heavily below 160 Hz, and the treble is rolled off heavily above 3 kHz!

So it appears the usual electric-guitar speaker may actually have all the bandwidth necessary for acoustic guitar. It definitely doesn't have the right EQ curve, though, so that will need to be fixed in the electronics. My guess is that this is exactly what's done in the Katana 50 and 100.


-Gnobuddy


I was not too concerned with frequency response. I have heard the blast of a 12" head on. But get off axis then hopefully you get reflections. But as I said, it all depends on your application. I have been to house concerts where the players had the acoustic guitar going through a Deluxe Reverb and with some fill by the mini PA doing vocals. It was fine for 30 people. Did the acoustic guitar sound like it did two feet away? No. But it did sound like an acoustic and once the (polite) drums and synth for bass (also going through the Deluxe) were added a good time was had by all. A 12" angled upward to the ceiling bounced down to the audience might have worked. While throwing out suggestions is useful it would help to know what level of performance is desired.
 
I wouldn't say I'm an expert on batteries. I know enough to be very respectful and cautious around the lithium ones, though. Once you've seen and smelled three completely burned-out vehicles, in each case destroyed by a lithium battery pack no bigger than a pack of cards that burst into flames, you get a healthy respect for the threat they pose!

There is a wee little battery-powered Katana Mini, with a 4-inch speaker, in a box the size of a box of facial tissues. I've never seen or heard one in person, but I think it resembles the Katana 50 in about the same way a plastic toy Tonka Truck resembles a real Ford F-450...

Here's a video demo from Anderton's Music; Pete Honore, the guy on the right with the purple Tele, is as talented and tasteful a player as I've ever encountered, so if anyone can make a Katana Mini sound good, he's probably the guy who can do it: YouTube

I have to say that video doesn't impress me much, despite the talented players. The Katana 50 sounds like a fun little toy for a joke; a $99 (USD) joke, while the excellent Katana 50 costs $230 (USD) at Sweetwater. Fifty times as much amp for two-and-a-third the price...

As to your other question, I haven't opened up my Katana - I kinda made myself a promise not to tinker with it, so I'll always have one good practice amp to use at home. So I don't know what sort of power supply it uses internally.

I suspect, though, that it's going to be a fairly complex one. The amp contains digital (DSP) chips, most of which run on 3.3V DC these days. It probably contains op-amps, which traditionally run on +/- 15 V dual polarity power. And according to the specs it contains a class AB power amp, rated at 50 watts into an 8 ohm speaker, which would require +/- 30 V power rails for a conventional amp, or one 30V power rail if it runs in bridge mode using a pair of power amps with the speaker strung between their two outputs.

All this is just a guess, but the guess is that the power supply will have to provide multiple different DC voltages, and maybe as much as 60 V DC (in the form of +/- 30 V rails.)

In principle, you can always generate the low-current voltages (such as 3.3V or +/- 15V) using little DC-DC converters which are off-the-shelf items these days. But if the amp really does use +/- 30 V rails, which have to be capable of supplying some 70 - 80 watts, that's going to be a challenge to replace with a battery. A single +30V rail that can supply 70 - 80 watts will be a bit easier, but still quite a challenge.

And then there's the whole question of battery size and weight and cost. I don't see any 50-watt battery powered amps on the market, probably because of the size and cost of the battery you'd need. Suppose the amp was running at an average power draw of only 20 watts, and needed to last through a 3-hour gig, you're still talking 60 watt-hours. You'd need about seven or eight 2Ah lithium cells (with their fire risk), or about twenty-five (!) 2 Ah NiMH cells.

Much though I generally hate the idea, I suspect the only reasonably practical way to battery-power a Katana 50 would be to run a sine-wave 120V AC inverter off something like a deep-cycle marine or RV 12V lead-acid battery, and plug the Katana into the inverter. Which would work, but be heavy, expensive, and inefficient. :(


-Gnobuddy
 
Is it really a class AB? It would need to have a substantial amount of cooling, I looked at a picture of the back and only saw two rows of cooling holes that did not look like they could cool a 50W amp. Does it have a power transformer? The weight for the amp is under 25 lbs isn't it?


I have a picture somewhere of a vehicle fire, Li battery caused. The battery of a solar car, I think the batteries most were running were 20Ah, 80V or there about. It was a good thing the driver got out in time.
 
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Is it really a class AB?
That's what the ad copy says. I was expecting class-D, so I was surprised.

Perhaps Roland / Boss didn't want to trigger superstitious "Class D sucks, don't buy a Katana!" responses from ignorant guitarists?

It would need to have a substantial amount of cooling, I looked at a picture of the back and only saw two rows of cooling holes that did not look like they could cool a 50W amp.
I wondered about that too. If the ad copy isn't a lie, and it really is a class AB amp, my guess is the entire metal chassis is used as a heatsink, and the output transistors are mounted directly to it. I've seen that trick in solid-state guitar amps before, including some sort of nasty-sounding Fender I once bought off Craigslist because I wanted the cab and 12" speaker. I think it was called a "Princeton DSP 65" or something like that.


There is another possibility: this is a guitar amp with lots of sophisticated electronics on board, and almost certainly, a switch-mode power supply. It's possible that Yamaha took advantage of that to operate the power amp in class G or class H; class H (where the power supply rails vary their voltage with the audio signal, to provide just enough headroom for the signal at any given instant) makes the amplifier generate much less heat.


Class H is basically class AB with a special power supply, so I can imagine the copywriters deciding to just call it class AB, once again, possibly to avoid spooking guitarists suspicious of any new-fangled technology.


All this is just guessing, to be very clear. I have no idea exactly what's going on in the power section of this amp.

Does it have a power transformer? The weight for the amp is under 25 lbs isn't it?
Right about 25 lbs, and that includes a sturdy cabinet and a beefy 12" speaker with a big fat magnet on it. I'm guessing the power supply is a light-weight switcher, not a traditional big-iron 60 Hz transformer.

I have a picture somewhere of a vehicle fire, Li battery caused. The battery of a solar car, I think the batteries most were running were 20Ah, 80V or there about. It was a good thing the driver got out in time.
A very good thing! :eek:

Aside from the extreme heat, burning lithium batteries give off some very nasty-smelling and irritating chemicals along with thick clouds of acrid black smoke. I bet it won't do human lungs any good to inhale that stuff.

Two of the three car-fires I saw were caused by pretty small lipo packs, 3 cell 2.2 Ah packs - about 12 volts and 2.2 Ah. That was enough to set fire to the inside of the vehicles, gutting one completely, and very badly damaging a second.

The third fire was in a virtually brand-new Ford van, one of the ones with a very tall roof. That pack was a 5-cell 2.2 Ah pack IIRC - it was for what is called a "Hotliner", an extremely fast, extremely powerful RC model airplane. The van was destroyed - completely burned out by the fire.

Considering that the biggest of these packs was only about 45 watt-hours capacity, I shudder to think what the 1600 watt-hour pack in that solar car could have done. Never mind the 85,000 watt-hour pack in some Teslas. :eek:

It's daunting to think what might happen if the Jaws of Life were used to cut open an electric car that had been in a crash. Shorting out the onboard battery pack by accidentally slicking through a power cable could have terrible consequences for both passengers and emergency response personnel in the vicinity.

There is some info on electric vehicle battery fires (caused by accidents, and in one case, salt-water immersion) on this Wikipedia page: Plug-in electric vehicle fire incidents - Wikipedia


-Gnobuddy
 
We had to qualify the cars for the race. One of the tests was that the driver had to get out of the car in a given amount of tine, 3 seconds seems to be what my poor memory thinks. Sound like a lot but you have to consider these cars are low to the ground and the drivers are laying down. To get in and out the steering wheel usually had to be removed. Our driver got out on the first try, he cut his leg getting out but didn't care because we passed the test. I built the protection circuit for it, dumb analog comparator circuit with the voltage, current and temperature of each cell monitored. I wanted it dumb so a Mechanical student could troubleshoot it if we had a problem. We did have a capacity problem with one of the cells during the race, it shortened the energy of the whole pack. We were suppose to to have a digital monitoring and RF logging system, never worked. Now you can get some great monitoring modules for next to nothing.
 
Sounds like a busy (but fun!) time. :)

Back in the early 2000s, an EE designed and sold little stamp-sized PCBs with a set of 0.1" header pins on one end, and tiny SMD comparators and LEDs on the board. Plug it into a mating connector on your 2 to 6 cell lipo pack, and the LEDs would blink on and off as the LED current balanced out the voltage from the cells. If you used it while the pack was being charged, you'd end up with a properly balanced pack at the end of the process.

The product became known as the "Blinky" balancer among the RC flight crowd.

Shortly after that, Astro Flight began selling a virtually identical product (I hope they licensed it and didn't just rip off the concept), the Astro Flight Blinky: 106 ASTRO "BLINKY" BATTERY BALANCER

I wonder how the same job is accomplished in today's electric cars. They can't just be burning up the extra power when they need to drain one cell in the pack to balance it, can they?


-Gnobuddy
 
Sorry for the devience from amp topic. I seem to recall a load resistor ad a mosfet across the cell and burning up the difference. Just befor qualifying for the race I had a adjustable ps and I spent all night balancing the cells. After the first day of the race I got some sleep. Was up for about 35 hours. Got us in the race. The car had to do about 112 miles around a NASCAR track at a minimum speed. I was not even suppose to be there, but without me we would not have got in the race. It was a crazy time.
 
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