Yesterday I had a request from my sons best mate to make him a tube preamp for his acoustic guitar and low and behold this thread landed in my lap.
I have very limited tube experience but have built amps & a valve DAC following closely to the suggested design.
Could the design Nelson has posted be used as a Guitar Preamp ?
I'd like to do something for my sons mate as he has stood by my son in very tough times.
David
I have very limited tube experience but have built amps & a valve DAC following closely to the suggested design.
Could the design Nelson has posted be used as a Guitar Preamp ?
I'd like to do something for my sons mate as he has stood by my son in very tough times.
David
Yes, but the result is probably not as good as plain ol' tubes like the 12AX7. Try it and let us know.
Design of a Korg Nutube Amplifier Part 1: Tube Basics
It depends on the type of sound/style of music that he likes/plays. The gain stages and tonestacks would need to be taylored to suit his liking.
The first post mentioned that this was to be an amp for an acoustic guitar. That is usually a much more straightforward objective - nobody tries to play death-metal on an acoustic guitar, because anything with high gain just gives you uncontrollable feedback. For the same reason, very few guitarists try to play rock or blues distorted solos with acoustic guitars.
So chances are, what your son's friend wants is an amp that is basically very much like a small P.A. system or powered speaker, with a flat frequency response from about 80 Hz to about 10 kHz, and enough power and clean gain to work with the onboard (probably piezo) pickup in the acoustic guitar.
Personally, I feel that an acoustic-electric is the only type of guitar that really doesn't benefit much (if at all) from having valves in the amplification chain, but hey, if it makes him happy, why not?
-Gnobuddy
So chances are, what your son's friend wants is an amp that is basically very much like a small P.A. system or powered speaker, with a flat frequency response from about 80 Hz to about 10 kHz, and enough power and clean gain to work with the onboard (probably piezo) pickup in the acoustic guitar.
Personally, I feel that an acoustic-electric is the only type of guitar that really doesn't benefit much (if at all) from having valves in the amplification chain, but hey, if it makes him happy, why not?
-Gnobuddy
It definitely can, but the thing is, the reason we usually want that extra 2nd harmonic distortion is to "sweeten" the ugly sounds that come out of a solid-body guitar pickup.
A lot of that ugliness is created by the magnetic pickup itself - the magnetic field around the pickup pole-pieces is not uniform, and the guitar string moving through this causes a heavily distorted signal to be generated in the guitar pickup.
A good acoustic guitar (or acoustic-electric) usually has a completely different type of pickup - either a piezo strip under the saddle, or a little microphone inside the guitar body, or both. These types of pickups don't produce the same harsh distortion that the conventional magnetic pickup does. In addition, the guitar body itself is designed to produce a pleasing sound via its wood and cavity resonances.
So IMO a decent acoustic-electric guitar sounds good if you just plug it into any generic low-distortion amplifier with a flat and wide-enough frequency response. Theres no real need for the amp to add "sweetening", the sound is already sweet!
As usual, this is just my opinion, based on just my ears and my brain. Others may or may not agree.
Worth mentioning: I have one guitar (a Takamine) that uses an actual valve (triode) in the built-in preamp. Takamine calls this design their "Cool Tube" preamp, and their stated intention was to remove some of that harsh "piezo quack" that you often read about in reviews of acoustic-electric guitars. So someone at Takamine did think that a wee bit of valve distortion could help improve the sound of an acoustic guitar...
Does it work? I don't know whether the valve is actually responsible, but that particular guitar does have a rather natural plugged-in sound (i.e. it sounds a lot like it does when unplugged).
I bought that guitar for an entirely different reason: it has steel strings but they are almost as widely spaced as a traditional classical nylon-string guitar. I have big fingers, and it's the only guitar I have that gives me enough room for fingerstyle playing.
-Gnobuddy
All sounds great to me, now I just need someone to do a GB on PCB for the Korg Triode
Good chance this might become available in diyaudio store.
Ask Variac.
If you don't want to wait, you can get the buffer PCB from Pete Millett: DIY PCB plus Tube - Buffer PCB using the Korg Nutube 6P1 | eBay
Thanks, waitings not a big problem I have SO many things to get finished, just agreed to a barter with a lady from work, she gives me a new high quality matteress (which I need) and I build her a simple work table and chair from her bedframe which I dont need!
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