> From: "G" > Subject: Amp Questions - Gurus req'd - Soldano Atomic 16 - (long) > > Hi All, > Hi G! I'll add some humble comments, I just bought an old Fender Champ tube amp during my staying in LA and I'm making some mods to it so I guess I can add some comments...
> The amp I was asking about ~is~ a Saldano Atomic 16 > Its a 20 Watt, 12" speaker, 16 ohm, Hi-Z input, dual output, A+B all tube > amp. > No reverb. I can't pretend I know what some of that means. > Some theory, when you chain two signal stages, the most efficient way (best power transfer) occurs when you match the output and input impedance (Z). So if it says 16 Ohm speakers it says that the output transformer is around 16 Ohms too so that's the perfect match to get the most powerfull sound.
And it's the same for an input, electric guitars are High Z output, so the best way to get the signal from it is to have a Hi-Z input, crystal/dynamic and ceramic mics are Hi-Z too (if not someone correct me, I don't have my mics here), most vocal and line outputs are LO-Z (as the output Z gets lower, closer is to an ideal voltage source), if you plug it with the wrong Z you'll lose volume. There exists some impedance change boxes in the market.
Class AB means it uses two tubes to get the whole audio signal, one for the upper half period and the other for the negative part, around zero they work together, this configuration is the most common in power amplifiers, it's very efficient in the power consuption sense and I guess that the tubes last longer compared to a Class A, in a class A (like my Champ) the signal moves on a single output tube (Class A, single ended... I've seen some push pull ... with two), well the main difference is that on a class A when there is no signal applied the tube it's working at the middle of it's working range... so even if you don't play the tubes are as hot as hell consuming a lot of power. The advantage is that the class A can have better sound quality because you don't have any distorsion around zero.. compared to the AB where you have a tube swap at zero.
> Its now sitting behind me in my lounge. :)) > Congratulations!
> The manual lists it as having three 12AX7 & two 6BQ5/EL84 tubes. > Can you play with combinations of the three smaller tubes, or do you just > stay with one type ? I guess 12AT7 or 12AUT7 will be mentioned, apparently > the 12AU7 is "cleaner" than the 12AT7 tubes... according to the shop keeper, > he also mentioned they are very rarely bought.... I'm still learning. Any > suggestions here ? Warm tones would be good. > >From what I've read the best tone is aquired saturating the output power tubes, it's been said that the distortion of the preamp tubes is not as warm and round (12ax7), but there're so many types of preamp tubes... some will sound better than others.
Considering that your amp comes with a gain pot you can easily distort the preamp without the need to switch to a lower gain preamp tube (that's the main difference, being the 12au7 the lower one), so I'd recommend to stick with the 12ax7 or maybe 12at7 but I don't know the circuit so I'd rathe say nothing. As the distortion you'll get will come from the preamp you might want to try various manufactureres, specially if you can find a Telefunken or some american NOS (new old stock, old tubes but never used, don't pay much money for them).
Anyway the best tone should be obtained with the interaction between the output power tube with the output transformer and the speaker... so you'll need to play really loud, or get an attenuator at the output.
> Someone kindly pointed out how I seemed to be concentrating on the tone of > the amps rather than considering the difference in mics, I thought this was > a good point. > Yes, of course... but as many of us have heard first is your technique, a good closed cup is really really important for amplified harmonica... it will add you a whole new world to explore in dynamics also.
Then the mike of course... you need to know which type you like the most, crystal, ceramic, dynamic, etc... for that you'll need to try them all, I have three , a shaker dynamic (I just don't used it anymore, a Rod Piazza's modified jt30 crystal mic and an old RCA controlled magneic aerodynamic bullet type mic), what I use the most is the jt30, but I'm tempted to buy a ceramic element for my RCA mike, I tried the green bullet sm520 but I just didn't like the sound it had... but it's a personal opinion.
Also some mics like the sm58 and 57 are really great for different styles, the sm57 is small enough to cup it very well.
> Maybe someone would let me know what type of mic BluesBlasters (or JT30's > for that matter) come with ? eg. Dynamic, Crystal / Condensor, are they > Hi-Z ? > Generaly they come with Crystal and are Hi-Z.
Ok, I got to go now... hope it helps, later on I'll write a summary of the mod I've been doing to my amp, specially to the tone controls...
cheers, Javier.
- -- Javier Argomedo - jargom~so.org - European Southern Observatory Blues Harmonica at http://www.freeyellow.com/members6/harping/ - ---- Casilla 1117, Vina del Mar, CHILE, Earth, Milky Way. ----
