Hello,
I am trying to find a good starting point to investigate a DIY guitar amp that is to be used with an acoustic guitar with pickup.
Ideally, it would put out 20-50W (for small clubs) and have a second input and mixing stage for a microphone.
Where should I start looking for circuits? Not new to electronics at all and not quite new anymore to tube amps (recently built one), but still considering myself fairly rookie-ish in this space.
I am nuts to even try myself on a guitar amp?
Thanks for your thoughts,
Stefan
I am trying to find a good starting point to investigate a DIY guitar amp that is to be used with an acoustic guitar with pickup.
Ideally, it would put out 20-50W (for small clubs) and have a second input and mixing stage for a microphone.
Where should I start looking for circuits? Not new to electronics at all and not quite new anymore to tube amps (recently built one), but still considering myself fairly rookie-ish in this space.
I am nuts to even try myself on a guitar amp?
Thanks for your thoughts,
Stefan
Nope, not nuts at all. I would strongly suggest a basic Fender two channel design, the root mean squared of all guitar amplifiers. Something like a Bassman circuit with the interstage cap throttled back to flatten the bass out (about .1 mfd if I remeber).
Then, to blow my own horn, one of the O-Netics "Blues" output trannys. This will provide a wonderfully woody sound, with a huge presence and the ability to bend into the notes. Even the thin body / piezo guitars sound like classical guitars with this combo and the tone controls are very useful. No reason to go any larger than 50 watts either, and even that will be stage performance level. The ""Blues" comes in four wattage's by the way. PM me with your email if you are interested and I will send you a data packet.
Bud
Then, to blow my own horn, one of the O-Netics "Blues" output trannys. This will provide a wonderfully woody sound, with a huge presence and the ability to bend into the notes. Even the thin body / piezo guitars sound like classical guitars with this combo and the tone controls are very useful. No reason to go any larger than 50 watts either, and even that will be stage performance level. The ""Blues" comes in four wattage's by the way. PM me with your email if you are interested and I will send you a data packet.
Bud
I think there was a thread here on such a project. Or TGP. I would 1st consider if the pickup is pre-amped or not on board the guitar. If not I would be more concerned about noise and would look to a balanced setup. But you need pretty much need that anyway because of the mic input. More EQ controls than a guitar amp could be cool and an anti-rumble control of some sort is a must with acoustic and doesn't hurt as an option on mics.
Thank you for responding.
The pickup/guitar does not have a pre-amp (it's a friend's guitar and he told me the output from the pickup goes straight to the plug without any active components).
Frankly admitting to not knowing much if anything about amps for musical instruments: Is there people out there who have done similar projects or example circuits that could be used/extended (including and other than the Fender Bassman schematics I've found already)?
Also there is a valid question of whether buying a used and potentially defunct amp off of eBay and fixing/modding it may be the wiser path for me...
Anyway, thank you for your input, I appreciate it!
Sure. The amp for acoustic guitar must be very clean and transparent, unlike electric guitar amp that adds character to the instrument that does not have it.
For an acoustic instrument what I would suggest is to first build one of these to place between the instrument and the amp:
Discrete FET Guitar Preamp
I can tell you from experience that it WILL give you the sparkle, edge, & tone, all without distortion. You will be very happy with the results.
Discrete FET Guitar Preamp
I can tell you from experience that it WILL give you the sparkle, edge, & tone, all without distortion. You will be very happy with the results.
Since it's for acoustic guitar and wants to be uncoloured you could try a chipamp. An LM3886 will do 35W without a big design effort, you could put one together in a pretty short space of time. As for a second input, a 2-input mixer and even some tone controls only require a few components and you will find circuits either by searching here or using google.
You can get more power from this chip, a maximum of 68W into 4 ohms, but it will require more attention to detail and heatsinking.
Show a diagram of what you intend here before you build it and get some feedback.
w
I normally recommend tubes for guitars, but not for acoustic.
You can get more power from this chip, a maximum of 68W into 4 ohms, but it will require more attention to detail and heatsinking.
Show a diagram of what you intend here before you build it and get some feedback.
w
I normally recommend tubes for guitars, but not for acoustic.
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Interesting statement. My amateur musician friend's expectation is that a tube amp would be providing a warmer and richer sound than his current SS amp, similar to what you hear with HiFi tube amps vs. SS.
Maybe that expectation is unjustified and he really is better off overall with the SS amp he is currently using!?
I think it's time for me to reconvene with him and see what he REALLY is looking for. Tubes are cool, sure, but if sound reproduction is the priority (which it always should be imho), then maybe it's the wrong pick for his application.
Thank you again for all your input, it is really helpful.
Why not make a hifi amp that doesn't use negative feedback? Then you have the fidelity for the acoustic sound without it sounding either sterile or distorted by the amplifier.
All you'd need is the power amp though it would probably be best to use a transformer-coupled design over an OTL to prevent any chance of electric shocks.
A valve preamp could be good to go with it to, check out the designs here: DIY 12AX7 Tube preamp
All you'd need is the power amp though it would probably be best to use a transformer-coupled design over an OTL to prevent any chance of electric shocks.
A valve preamp could be good to go with it to, check out the designs here: DIY 12AX7 Tube preamp
Perhaps you might like to read this series of white papers by Hartley Peavey:- Peavey.com. They talk about how tube guitar amps differ from hi-fi amps.
It's true that tube amps provide a warmer, more coloured sound, up to and including what would simply be called distortion when overdriven. For acoustic I would be thinking more in terms of a hi-fi amp, which is much easier to build in the power range you are talking about using SS. 20 - 50W is not a big tube guitar amp, but it is a big hi-fi amp.
I don't mean to prejudice the choice, it's really a case of personal preference. Your friend could try a few amps in a shop without causing any offence, I'm sure. Maybe tubes are really what he wants.
w
It's true that tube amps provide a warmer, more coloured sound, up to and including what would simply be called distortion when overdriven. For acoustic I would be thinking more in terms of a hi-fi amp, which is much easier to build in the power range you are talking about using SS. 20 - 50W is not a big tube guitar amp, but it is a big hi-fi amp.
I don't mean to prejudice the choice, it's really a case of personal preference. Your friend could try a few amps in a shop without causing any offence, I'm sure. Maybe tubes are really what he wants.
w
Why do most people, even some tube-guys, say that for acoustics one should not use tube? Obviously they are saying tubes are inferiour. Just b/c tubes are better overdriven than SS doesnt mean tubes can't be used in a clean amp. For an acoustic u basically build a nice class-A PP pwramp and a single gain-stage pre. A tone stack (baxandall type) and perhaps a notch filter to remove unwanted feeding, otherwise a flat HiFi-ish response should do.
I resent the remark that electric guitars dont have character. I've heard many acoustics that are dull and lifeless. However, electrics can be used with effects (on purpose) to produce more types of sounds than most other instruments.
Btw. Peavey is talking about electric guitars. Not to be confused with acoustcs.
I resent the remark that electric guitars dont have character. I've heard many acoustics that are dull and lifeless. However, electrics can be used with effects (on purpose) to produce more types of sounds than most other instruments.
Btw. Peavey is talking about electric guitars. Not to be confused with acoustcs.
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I see 2 options here: either triode output SE amp using DHT with no feedback at all, or pentode PP with deep feedback. Both approaches are valid for clean and transparent amplification of an acoustic guitar. However, the 2'nd one can be made lighter and more effective.
Good PA? Do you mean something from Altec Lansing? Too expensive, I am afraid. I don't remember any more good PA amps, that's why I designed my first Pyramid.
Good Hi-Fi is more affordable, like some amp from vintage Magnavox console. Or, take that nice amp from Tubecad journal that was discussed recently in a couple of threads.
Good Hi-Fi is more affordable, like some amp from vintage Magnavox console. Or, take that nice amp from Tubecad journal that was discussed recently in a couple of threads.
OTL classical guitar amp
I build an OTL guitar amp spesificly for acustic clasical and jazz.
A Freind of mine just loves the amp I've built for him. You can check him out on utube.
He is one of the top prefomers, a must see and hear at Branson Mo.
Jim Greeninger is my good freind. He has spent many HRs helping me make an amp to his liking. His standards a very high.
Another musision that surprized me with the very clean OTL is Fritz the Harp-Mic-Man.
Fritz was just here today in my amp lab. He and his freind Hank who playes with Curtice were both very impressed with the OTL as well as the Masco MA-35 I've just moded.
Anyway check out Jim Greeninger on utube.
Jerry
I build an OTL guitar amp spesificly for acustic clasical and jazz.
A Freind of mine just loves the amp I've built for him. You can check him out on utube.
He is one of the top prefomers, a must see and hear at Branson Mo.
Jim Greeninger is my good freind. He has spent many HRs helping me make an amp to his liking. His standards a very high.
Another musision that surprized me with the very clean OTL is Fritz the Harp-Mic-Man.
Fritz was just here today in my amp lab. He and his freind Hank who playes with Curtice were both very impressed with the OTL as well as the Masco MA-35 I've just moded.
Anyway check out Jim Greeninger on utube.
Jerry
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