I want to build a cello amp

[Milnoque]

My wife has an Yamaha electric cello. I want to build an amp for it. My previous (only) build was a Trinity TC-15. That amp sounds great with the cello but I want a bit more clean headroom for this project. I decided to go with cathode biased 6l6s for this one. I basically used the 12AX7 channel preamp section from the TC-15 because the cut control was very useful when dialing in the tone. I used the output tube section from an old Fender Pro Amp for the 6L6s.

I have an old Hamilton Hi-Fi amp I plan to gut and convert for the project. If someone has the time, I would love comments on whether this whole project is a good idea in the first place and whether I'm close on my schematic.

[Steve L]

Yamaha Cello

I know it is not what you are asking for, however you may find this helpful.

Yamaha SVC10 Silent Cello Service Manual.pdf

Steve

[Milnoque]

Thanks Steve,
We have the manual. The instrument's internal amplifier is only strong enough to push earphones. It doesn't overgain my guitar amp. I want to do this amp as a project because building my TC-15 was very satisfying and I wan't to do something more. I thought figuring out how to voice the amp after I build it would be very instructive for me.

Are you a cellist? My wife took up the cello about three years ago and we have been incorporating it in my acoustic band. The Yammie has been a godsend for outdoor gigs. It's a very satisfying option when conditions are hard on her acoustic one.

[Marc]

Have you considered an Ampeg portaflex circuit? It's a bit more bass friendly than the vox circuit that Dianna's amp is based on.

Marc

[Milnoque]

I have a B-18 portaflex. I definitely considered it. It ends up that the cello requires more articulation. The bowed attack is lost on the Ampeg. I also found the cut control on the TC-15 is more useful than any other part of the tone stack for her instrument. Like I said, The TC-15 sounds great with her cello. I just wanted more clean headroom.

[Steve L]

I like your schematic. I am not a cellist, however I have played a little violin.
In my limited experience, I think that the closer you aim for a wide-bandwidth sound, the better off you will be.
There are a lot of overtones in a cello or violin that can get lost in a guitar or bass amp easily, despite how good it may sound for other instruments.
That is probably why the cut or presence control in the TC-15 is so useful for you.

Steve

[J M Fahey]

Respectfully, I would build an SS amp, not a tubed one, and even less a "guitar type" one.
I have made lots of such amplifiers for Symphonic and Tango orchestras as well as Argentine Folkloric players (they use Spanish guitars, "charangos" (armadillo guitars), violins, "quenas" (reed pipe Pan flutes) , accordions, and raw hide percussion), where an "electric" sound is absolutely unacceptable; they need "the same sound as the unplugged instrument", only louder.
On most instruments I had to add acoustic mics (electrets will do fine) , because piezos are too "spikey", although that can be equalized off.
You also need speakers much flatter than typical guitar ones. You are unconsciously noting that when you find the "cut" control useful: it dampens the treble peaks found in those speakers.
One of Eminence PA series speakers (Alphas, Betas, etc.) coupled to a 5" mid highs unit will be very flat and sweet; if you need a tweeter try to go for an all cone system; piezos will be shrill and bullets overpowering (and Hi Fi type soft domes not loud enough).
Well, that's basically it.
Good luck with your project.

[Milnoque]

To J M Fahey,

Thanks for taking the time to respond. You are not the only one who has recommended solid state as a preferred alternative. I know that when I run her instrument through my PA system the result is lifeless and sterile. Results using an SS keyboard amp were similar. My guitar amp is much warmer and sweeter and actually gives me a sound more like an acoustic cello. You're right on the money about speakers though. The guitar amp through a PA speaker is the best configuration I have. I expect to turn my attention to a purpose built speaker cab as a next project. I have so much to learn in that area. Your suggestion in that area will be very helpful.

The instrument I'm working with is not an acoustic cello. It sends a well chosen sample to be amplified. We use an SDC for her acoustic cello and it sounds acceptable direct to the PA.

[dchang0]

I currently play my Yamaha electric violin through a Princeton Reverb clone, and it sounds great. The tubes really warm up the tone and add body.

However, it rolls off the highs far too much for my tastes, and so I ended up using a Yamaha MSR100 (discontinued), a small wedge-shaped self-powered PA speaker. It is fully solid state and sounded pretty good, even for electric upright bass. I sold it and kept the PR not because the PR sounds better for violin (it doesn't), but because the PR is more versatile (guitar, bass and upright electric bass all sound pretty good). But for bowed instruments, solid state PA amps are definitely the way to go.

If you wish to build a tube amp anyway, I would suggest that you focus on adding clean top end and upper-midrange and install a flat-response PA speaker instead of a guitar speaker. I used to run a pair of JBL PA speakers off of my Twin Reverb, and they were phenomenal. My sound man didn't like 'em because of the piercing highs, but they sure sounded sweet to me! The Twin is probably the best choice for clean headroom for bowed instruments, though the wattage is way too much. Luckily, since you want it clean and not overdriven, you can just turn the volume down...

Alternately, perhaps you would mess with the pickups/transducers in the cello itself to get more highs. I noticed that different models of the Yamaha electric violins have different tonal characteristics, with the cheaper models losing a lot of the highs, and therefore, bow response. Adding an extra pickup or transducer might make a world of difference. This option is the most likely to sound the best, by far.

There is another option: building a small tube preamp and running it into a solid state power section (or right into your mixing board). You might try building one of the Elekit hi-fi tube preamps TU-875 (photo here, review is for the TU-879S: http://www.6moons.com/audioreviews/elekit/6L6.html).

One final idea: get a graphic equalizer pedal or rackmount unit to shape the tone. It may be far cheaper than any other option. This was the only way I could get any bowing definition on the upright electric bass, by the way, no matter what amp or PA we ran it into.