View Full Version : Question about Acoustic Amps and PreAmps
I'm just in the curiosity phase of amplifying an acoustic mandolin. I read in the description of one of the popular pickups that it's very important to use a good preamp meant for acoustic string instruments. But looking amplifiers, it seems like many have a first stage has many of same features, three-band EQ, notch filters, etc. What I wonder is if you have an acoustic amp with the necessary first-stage features, do you really need a preamp? Or, if you have a really nice preamp, do you really need an acoustic amplifier or would just a power amp and appropriate fullrange speaker work?
Ray(T)
Jul-08-2019, 8:06am
1) Not necessarily, give it a try.
2) No; but you might find an acoustic combo amp more convenient for carting around.
Greg P. Stone
Jul-08-2019, 8:56am
Power amp and full range speaker works but Ray is right. Acoustic guitar amps don't have the bass that the first option has but mandolins don't need it and most of the weight of the former is to get the lower bass.
Another option is a small powered PA speaker. Individual used units can be found fairly cheap. I got mine for $30 and it originally sold for $1200. Also got a single Mackie HR824 for $10, original price $850.
IIRC guitar preamps' purpose is to provide a strong enough signal so that the noise picked up in the connecting cable is small by comparison and isn't noticeable coming out of the amp/PA. If you need a long cable, a short one to a booster preamp pedal, then the long one should work.
pops1
Jul-08-2019, 12:33pm
A preamp is not to boost the signal from a transducer pickup. The pickup has plenty of power on it's own. It does however have an impedance of 1 million ohms and a PA wants to see somewhere between 800-1200 ohms. The purpose of the preamp is to match the output impedance of the pickup to the input impedance of the PA. The new acoustic amps have a channel that matches the impedance of the pickup so it is not necessary to use a preamp. Some plug into the acoustic amp and then line it into the PA which also works fine. I use a preamp into the PA.
John Bertotti
Jul-08-2019, 6:36pm
I don't have an electrified mandolin yet but my martin 000-18 has the K&K pure western mini in it. I use it with a QSC K10. Sounds great but it is a bit feedback prone. I do not have a soundhole cover. However, be warned I liked the QSC K10 so much I wound up with two.
It amazes me that people who put pickups in guitars or mandolins don't bother to educate their customers about the importance of an impedance matching devise. I became more involved in an open mic and had realized how many people with $5000 guitars equipped with K&Ks would just plug into a mixing board. The host at the time was an electric guitarist and didn't much care. I listened week after week to piezo mismatch. I used a RedEye, and with few exceptions was alone in this.
Fast forward to a new host and I fill in. We were both concerned about poor sound and have upgraded almost everything. I had SunnAudio build me a blender so we could have a proper impedance match on at least two piezo equipped instruments. The quality of sound improved greatly. Even the cheapest undersaddle piezo pickups sound tolerable now. But now comes the reality. People don't really care. I'm talking about the more casual player. But my ears don't hurt anymore.
An acoustic amp really needs to be a full frequency devise. Most acoustic guitar amps have a tweeter. My well loved Carvin AG 300 has a 12", 5", and tweeter. The speaker part of it is close to a PA cabinet. I can take it out to a small gig and put a mic through it and it is a simple no fuss solution. More and more acoustic musicians are using powered PA speakers as they provide flexibility. Two powered speakers and a small mixer and you can take one or both speakers to a gig depending on need. Add a couple more small powered speakers for monitors and you can power a small band. I'm seeing more mixers with an input impedance switch these days.
We had an issue with the mains one time and just turned the Behringer 8" monitors around and filled a good sized room with sound, and I believe these are around $180, so you don't need to spend a ton. But like everything else throwing money at QSC will make you very happy.
John Bertotti
Jul-08-2019, 6:41pm
It amazes me that people who put pickups in guitars or mandolins don't bother to educate their customers about the importance of an impedance matching devise. I became more involved in an open mic and had realized how many people with $5000 guitars equipped with K&Ks would just plug into a mixing board. The host at the time was an electric guitarist and didn't much care. I listened week after week to piezo mismatch. I used a RedEye, and with few exceptions was alone in this.
Fast forward to a new host and I fill in. We were both concerned about poor sound and have upgraded almost everything. I had SunnAudio build me a blender so we could have a proper impedance match on at least two piezo equipped instruments. The quality of sound improved greatly. Even the cheapest undersaddle piezo pickups sound tolerable now. But now comes the reality. People don't really care. I'm talking about the more casual player. But my ears don't hurt anymore.
An acoustic amp really needs to be a full frequency devise. Most acoustic guitar amps have a tweeter. My well loved Carvin AG 300 has a 12", 5", and tweeter. The speaker part of it is close to a PA cabinet. I can take it out to a small gig and put a mic through it and it is a simple no fuss solution. More and more acoustic musicians are using powered PA speakers as they provide flexibility. Two powered speakers and a small mixer and you can take one or both speakers to a gig depending on need. Add a couple more small powered speakers for monitors and you can power a small band. I'm seeing more mixers with an input impedance switch these days.
We had an issue with the mains one time and just turned the Behringer 8" monitors around and filled a good sized room with sound, and I believe these are around $180, so you don't need to spend a ton. But like everything else throwing money at QSC will make you very happy.
Interesting. I don't know what difference I would hear with a preamp into the QSC but it does currently sound very representative of its unplugged sound. I wonder if using my audio interface and the preamp output to the QSC would do the required impedance matching so I could hear the difference?
I have tried it through an RNP and it sounded great but a bit different, not better nor worse just different. I think a bit rounder or darker however you want to put it. It is a mic pre so I don't know if the K&K was a good match for the RNP.
Interesting. I don't know what difference I would hear with a preamp into the QSC but it does currently sound very representative of its unplugged sound. I wonder if using my audio interface and the preamp output to the QSC would do the required impedance matching so I could hear the difference?
I have tried it through an RNP and it sounded great but a bit different, not better nor worse just different. I think a bit rounder or darker however you want to put it. It is a mic pre so I don't know if the K&K was a good match for the RNP.
Look at your specs and find input impedance. If it is around 1 million (1Meg) ohms then it will work fine. If it is close either way it will work fine. You may not hear as much difference with a mandolin as there are not as many lows, but you will sure hear it with a guitar.
John Bertotti
Jul-08-2019, 9:54pm
Look at your specs and find input impedance. If it is around 1 million (1Meg) ohms then it will work fine. If it is close either way it will work fine. You may not hear as much difference with a mandolin as there are not as many lows, but you will sure hear it with a guitar.
Xlr or 1/4" input impedance is 2260Ohms so 2.2K set to mic, but I do not know what the pure mini is.
Greg P. Stone
Jul-08-2019, 10:26pm
To continue my uneducated "IIRC", a long cable will kill the treble, so a preamp corrects that problem. Perhaps cables are made so well today that noise which the cable picks up is no longer a problem. If it is still a problem in some parallel universe a preamp helps.
pops1
Jul-08-2019, 10:27pm
The pure mini is 1 million ohms. A long ways away from 1 Meg.
Virtually any acoustic pre amp or acoustic amplifier will have the correct input impedance. Where you need to be careful is if you use a Di instead. Many other devices use DI boxes, keyboards and electronic drums for example, and they don't require this, so you'd need one with a 1 Meg ohm input impedance.
A high impedance switch is showing up on many mixers these days.
John Bertotti
Jul-09-2019, 5:10am
Well, it turns out my RNP is 1Mohm input impedance so I am going to give it another look. I tried it with the K&K equipped 000 once but never really messed with it after that. This bears some more experimenting.
Thansk everyone!
https://fmraudio.com/rnp.html
Todd Bowman
Jul-09-2019, 6:57am
All the technical talk about impedance matching and ohms is great, but as I am not an electrical engineer, I like this quote from the Grace Designs Felix preamp user manual:
Both Ch1 and Ch2 line inputs have 3 input impedance settings,
selectable from the toggle switch labeled ‘Z’ . The settings are:
Ch1: med - 1MΩ / hi -10MΩ / low – 10kΩ
Ch2: med - 1MΩ / hi -20MΩ / low – 332kΩ
Some pickups or sources are more sensitive to preamp input
impedances than others. For example, if you use a ‘Sunrise’
magnetic pickup, they prefer to connect with an input
impedance of 1MΩ. If you have an onboard preamp or a lower
impedance pickup, the input impedance setting will probably
make less of a difference. In any case, we encourage you to try
different settings with your pickup or source. The difference
may be noticeable or not, and should be set accordingly to
what sounds best to you. Always what sounds best to you!
The "Always what sounds best to you" make the most sense to me. :-)
A nice feature offered by Grace. It is only the pizeo pickups that have such a high impedance, that I know of. A magnetic pickup would be nowhere near that. 6K-12K would be more like it. Nice that Grace offers the 10K input, but then a pre is rarely used with a magnetic pickup.
almeriastrings
Jul-09-2019, 8:22am
You can certainly go from a good 'acoustic' preamp direct into a high quality full-range powered speaker. The QSC K10's and K8's are ideal for this. It essentially gives you an all-in-one 'acoustic combo' but in two pieces. This does give you quite a bit extra flexibility and redundancy.
Obviously, if you need to add other instruments or vocals, you'll need to insert a mixer between them.
There are several valid ways of approaching this. Indeed, you can use some 'acoustic combos' as a mini-PA...
Br1ck
Jul-09-2019, 12:55pm
There are certainly many ways to go here. I've seen guys doing a solo gig with a Fishman mini. Wouldn't do that myself, but in reality, no one cared.
I've seen guys doing a solo gig with a digital QSC mixer, two QSC k 12s , and a thousand dollar mic. In reality no one cared, except for the one sound geek in the audience. Thanks dude.
It comes down to how much you care about your sound.
A friend is doing a solo gig at a venue with no sound reinforcement at all. People have to listen.
Mandobart
Jul-09-2019, 3:37pm
The pure mini is 1 million ohms. A long ways away from 1 Meg.
Ummm, no. 1 megohm = 1 million ohms. Just like 1 kilohm = 1000 ohms.
Dave Greenspoon
Jul-09-2019, 4:05pm
A guitar playing buddy of mine goes thru a Boss acoustic preamp pedal into the Tonematch for his Bose S1. It sounds so great he went out and bought another S1.
On the other side of the spectrum, I recently plugged the Rigel straight into a Fender Passport 250, and it sounded surprisingly decent.
Ummm, no. 1 megohm = 1 million ohms. Just like 1 kilohm = 1000 ohms.
Thanks Bart, that was supposed to be 2.2k
John Bertotti
Jul-09-2019, 9:39pm
Thanks Bart, that was supposed to be 2.2k
That had me a bit confused as well but yes I see what you are saying the 2.2k on the QSC input is a long ways from 1M. I can't wait to get home and play with the RNP some more. I haven't had it out for some time since I got my Zen Tour. I was brushing up on it and it is very versatile, at least for my needs.
Daniel Nestlerode
Jul-11-2019, 2:06am
But now comes the reality. People don't really care. I'm talking about the more casual player. But my ears don't hurt anymore.
Yep. Non-musicians listen with their eyes. But better sound will improve the overall experience, so they will like it better. They just won't be able to tell you why.
I use an Orchid Electronics Pre-amp. Very popular among the folkies in the UK for guitar and mandolin. It's not terribly expensive, it's built like a tank, and it works like a charm. I could go into a full spectrum amp, but I generally go to the PA from it.
The lack of experience with mandolins and acoustic instruments in general among 'engineers' here in the north of France has influenced my efforts to go full electric. At least that way I have control over my tone.
Daniel
mandroid
Jul-11-2019, 4:06pm
Piezo pickups, a company like Fishman also makes amps, and the pickups , so I expect they have inputs with right impedance.
I have a Schertler Dyn* Pickup It is a contact microphone , so acoustic amp preamp in mic channel works..
It has a strong signal , so with a common impedance matching transformer , I can Plug into Guitar amps too....
* now there is an active 48v phantom power, and a passive.. model , I only have the older Dyn Passive,
impedance matching transformers, input is XLR but output is TR 1/4" (minus and ground combined..)
....
almeriastrings
Jul-12-2019, 2:11am
I use an Orchid Electronics Pre-amp. Very popular among the folkies in the UK for guitar and mandolin. It's not terribly expensive, it's built like a tank, and it works like a charm. I could go into a full spectrum amp, but I generally go to the PA from it.
Orchid DI's are really excellent. Their technical performance is up there with the very best at a fraction of the price.
I've used their stuff for years. Never had a failure.
I use the RedEye, still have my Orchid, but too many places I play either don't have phantom or it is not 48 volts so I don't use it much anymore. Liked it while I used it tho.
When putting a system together, it is important to pay attention to the components used in the device. You can spend your money on something like a RedEye, which has relatively few parts of high quality, or spend the same money on something with four bands of EQ, and a digital processor or two. I vote simple quality. These days I use a SunnAudio Stage 1.
Daniel Nestlerode
Jul-14-2019, 1:45pm
I use the RedEye, still have my Orchid, but too many places I play either don't have phantom or it is not 48 volts so I don't use it much anymore. Liked it while I used it tho.
Really? Nearly every desk I have ever seen has a button for 48v phantom power. Most people never use it. So I can imagine quite a few amateur engineers wouldn't know about it.
I did a gig where one guy turned it off again just before I got to the instrument that uses it. He asked me if it was dangerous to leave it on. :confused:
:)
Daniel
Yes, just about every mixer has phantom power, and Hi Z switches are seen a lot too. But you are correct that the people using them don't know the how and whys of their mixers. I imaging the impedance switches are labeled hi Z for space considerations.
almeriastrings
Jul-15-2019, 2:03am
'Hi Z' is the correct technical term as 'Z' is the formula for impedance in electronic calculations.
John Bertotti
Jul-15-2019, 4:16am
Yes, just about every mixer has phantom power, and Hi Z switches are seen a lot too. But you are correct that the people using them don't know the how and whys of their mixers. I imaging the impedance switches are labeled hi Z for space considerations.
In defense of new people I had no idea what phantom power was when I started. Fortunately Being trained in electrical and electronics I knew what bins was but had no idea how it applied to music at the time. We all start somewhere thankfully there are helpful people out there to get newbs on track. Pardon the pun.
Ray(T)
Jul-15-2019, 5:58am
Phantom power can be scary if you try to connect unbalanced sources to balanced inputs. Don’t turn it on in such circumstances if you don’t know what you’re doing!
Really? Nearly every desk I have ever seen has a button for 48v phantom power. Most people never use it. So I can imagine quite a few amateur engineers wouldn't know about it.
I did a gig where one guy turned it off again just before I got to the instrument that uses it. He asked me if it was dangerous to leave it on. :confused:
:)
Daniel
I am sure most new equipment, especially a board would have 48v phantom. I use a Carvin Stagemate, it does not have phantom. I play weekly boat cruises and set up a smal 6 channel (new) Peavey, it has 30v phantom. The Orchid needs the 48v. It will work with less, but not as well. I like the RedEye as it sounds good and is small to carry. I have sold other pre's, but keep the Orchid around, maybe will get it out again, it was a good sounding pre. A lot of folks I know and play with (old time) use older equipment and while it has phantom, not 48v.
Mandobart
Jul-15-2019, 10:41am
I've never used one of these stand alone phantom power supplies (https://www.sweetwater.com/c959--Phantom_Power_Supplies?mrkgcl=28&mrkgadid=3319245785&rkg_id=0&campaigntype=dsa&campaign=aaDSA&adgroup=1233692239%3ADSA%20-%20Studio%20%26%20Recording&placement=google&adpos=1t2&creative=282276642889&device=t&matchtype=b&network=g&gclid=EAIaIQobChMIk82JjKC34wIVVh6tBh0uVQvoEAAYAiAA EgJmVvD_BwE) (I use a RedEye these days which runs on phantom or 9 volt battery). Would this work if your board/amp doesn't provide it?
pops1
Jul-15-2019, 11:02am
I have a stand alone phantom, used it for years and works great. Usually only use it for large diaphragm condensers tho.
John Bertotti
Jul-15-2019, 3:42pm
If you have phantom power there is always something like the cloudlifter to use phantom to make a clean pre. I think that's what it does.
mandroid
Jul-17-2019, 1:49pm
FWIW, c-Dyn.s is a built in schertler pickup .. now resocoil with TRS 1/4" jack ..
works well.. (XLR Plug may work on large bodied instruments)
https://secure.schertler.com/en_US/shop/pickups/resocoil
Steve Ostrander
Jul-20-2019, 9:30am
I have a K&K in my Breedlove ff and my Acoustic guitar and I go directly into my Fishman Artist with both. It sounds good. I sometimes will use the DI out on the back of the Artist into my Fishman SoloAmp PA if I need to fill more space.
Going direct into a guitar amp made for electric guitar or DI into a mixing board is going to be a mismatch. It usually sounds shrill and quacks like a duck.
Br1ck
Jul-20-2019, 12:26pm
While I like my acoustic amplifier, and use it solo, I believe I'd go the powered speaker route if I were starting over. You can use it solo and it's handy in a group for either PA or monitor speaker. Get two and build a small PA around them. Use either a pre or mixed in front.
John Bertotti
Jul-20-2019, 1:56pm
While I like my acoustic amplifier, and use it solo, I believe I'd go the powered speaker route if I were starting over. You can use it solo and it's handy in a group for either PA or monitor speaker. Get two and build a small PA around them. Use either a pre or mixed in front.
I don't play out but the versatility of the Small powered PA is exactly why I went with them and sadly I wanted some less, much less expensive ones but these were in store also and I had to try them. You know how they say only try instruments within your budget, the same holds true for PA speakers. And for anyone new to mixers PAs and such is be aware of the hidden cost, bit me rather hard, cables! Didn't even consider it until I got home and realized I didn't have enough anymore! Oddly I use them for everything music from my acoustics to playing back form my software through them to hear how it sounds to just using them as very loud boom boxes when I am working outside.
I use an ATM350 mic along with a K&K mini for reinforcing my Bourgeois Country Boy and it sounds great, going in to a mic pre (stand alone or mixing board pre) and ending up at a Bose L1 system...very natural, very punchy and above all, not plasticky. You can clip this mic into the soundhole ala Sean Watkins, Chris Eldridge and others. Use your pre to EQ to taste...I really like this combo.
The ATM350 alone is pretty fantastic for mandolin, and as you all probably know, was what Chris Thile used for a long while (well, the older ATM35).
The Grace Felix pre has some great capabilities as well...
Mandobart
Jul-22-2019, 12:03pm
Going direct into a guitar amp made for electric guitar or DI into a mixing board is going to be a mismatch. It usually sounds shrill and quacks like a duck.
Again, its the unmatched output impedance of the piezo (1 to 10 million ohms) with the input impedance of the amp or PA (a few thousand ohms). This is basic signal path stuff that applies to radio, radar, video, etc. I learned it 40 years ago in the USN as an electronic tech. This was discovered when radio was developed. Its not a new phenomenon.
Despite all the other secondary features touted by everyone selling preamps, it is this basic impedance matching (not signal boost, not multi-band EQ, not looks or low weight, not rare materials) that determines how good your signal chain will ultimately sound.
John Bertotti
Jul-22-2019, 12:27pm
Again, its the unmatched output impedance of the piezo (1 to 10 million ohms) with the input impedance of the amp or PA (a few thousand ohms). This is basic signal path stuff that applies to radio, radar, video, etc. I learned it 40 years ago in the USN as an electronic tech. This was discovered when radio was developed. Its not a new phenomenon.
Despite all the other secondary features touted by everyone selling preamps, it is this basic impedance matching (not signal boost, not multi-band EQ, not looks or low weight, not rare materials) that determines how good your signal chain will ultimately sound.
I downloaded the NEETs manuals when they made them available. Solid beginning to electrical and electronics. A lot better than the afunp class. This is a screw driver hahahahaha. But yes impedance matching makes a difference how much depends on where you are starting from and what you want to hear. Like guitars and true bypass, I’m back to a buffer because it
Just works better at retaining the signal.
Just like there are pretty decent mandolins made for modest budgets, like the Eastman 300 series, you can get decent powered speakers these days that won't cost an arm and a leg. I use some very credible Behringer 8" speakers as floor monitors. Pretty good sound for the buck. Of course, put them next to some QSC K series and you'll want those.
John Bertotti
Jul-22-2019, 10:08pm
Just like there are pretty decent mandolins made for modest budgets, like the Eastman 300 series, you can get decent powered speakers these days that won't cost an arm and a leg. I use some very credible Behringer 8" speakers as floor monitors. Pretty good sound for the buck. Of course, put them next to some QSC K series and you'll want those.
Yep a side by side is how I got bit! Love my QSC.
Br1ck
Jul-23-2019, 11:59am
We use a large back room of a restaurant/bar for an open mic. The venue also runs karaoke twice a week. The mains are hung from the ceiling. We were so tired of the thirty year old tired Peaveys, we decided to replace them, since the venue owner pays the ASCAP fees and the host every week, we collectively foot the bill for QSC 15" passive speakers. Extremely high quality and money well spent. QSC has it going on.
mando-bob
Jul-23-2019, 3:09pm
I used AER Compact 60 and Acoustic Image Amps for years. Three years ago my local dealer offered me a QSC K8 for testing. I really loved the clean sound they gave. Now I use the K8.2 which offers (besides many more wonderful features) a optional Hi Z on Input 2, for those of us who want to use it with passive pickup.
For live performance we (acoustic trio) use two QSC 10.2 speakers and three QSC K8.2 for monitor - best system I had so far.
mandroid
Jul-25-2019, 2:41pm
& Y'ha even lets you take the amp/preamp-mixer out, and place it next to you..
mando-bob
Jul-26-2019, 7:21am
Exactly: When using the house P.A. or at festivals I bring the QSC K8.2 for personal monitor, fed by my preamp line out.