Wednesday, May 28, 2008

The Voice of Music



There is terminology regarding the reason for this post--G.A.S. I don't have to offer any additional explanation for those that have suffered from it. For the uninitiated, the acronym stands for "Gear Acquisition Syndrome" and it infects musicians of all ages, sex, creed and color. I think that the episodes that I've had have been fairly mild. So far, each of the amplifiers that I have offered a post about has its place of importance as far as my harmonica hobby goes (which I still need to provide more historical detail to). The 1483 with the Python cab provides the "boom" needed to hang with bands that get a little loud, the Kalamazoo can provide a little home practice without irritating the neighbors and can play out in small, reasonably volumed venues and the Ol' Smoky just fell in my lap for $1.25.


So, I had two 6L6 powered amplifiers and one EL84 and began to think in terms of maybe getting a 6V6 tubed amplifier for yet another tonal difference. I really had no serious intentions and thought that I would look around eBay and see what was floating around (I always hear a little voice that says, "Put you hands on your head and back away from the keyboard."). I scrolled through the auction fairly rapidly and casually, but kept coming back to a little amplifier head that had been pulled from an old phonograph. The bid price of $100 and the fact that the seller claimed that it had "tone for days" with his guitar, that it had been gone through by his amp tech, that he would include "primo" power tubes and throw in a guitar cord, intrigued me enough to offer my top bid of $125. Of course, I never expected that bid to last long at all and, of course, I was surprised the next day when I was once again informed, "Congratulations, You Won!"--another item that no one else wants.


I knew what to expect with the $1.25 Ol' Smoky amp, but I was hoping for more of a "plug and play" with the Voice of Music since the owner had been playing his guitar through it. The amp arrived in good shape. The "primo" tubes were a couple of different branded 6V6 power tubes. He did include a couple of extra preamp tubes for tone experimenting. I took a chance and plugged the amp in, connected it to my old Sunn cabinet, blew a few harp notes and it didn't sound half bad. I plugged it into the Python cab and it sounded a bit better. I then went into investigation mode.


I found a website dedicated to Voice of Music products of yore and discovered my model was a V-M 160 and was designed in 1952 as an institutional amplifier (for schools and such) to power record turntables and the like. It also was used in a phonograph console, which contained a sliding tray for the amplifier. It was configured to be powered by two 6V6GT tubes, a 5y3 rectifier, and two 12ax7 preamp tubes to generate 8 watts. These amplifiers were produced in a Benton Harbor, Michigan plant and like a great deal of such equipment produced in the '50s, they were built to last--I mean, here it is producing tones in 2008.


After opening the amp up to check out the guts, it was obvious that NO amp tech had gone through the thing. There were a couple of resistors and a capacitor that were added or had values changed to produce a little more gain for guitarists (which is not needed for harp) and the addition of a 1/4 speaker jack and that was about it. There was no indication that the power filter capacitors had been replaced since the fifties or that any of the electrolytic capacitors had been updated. THEN, I went about taking voltage measurements and they were too darned high in both the preamp and power section of the amp and the bias readings on the power tubes exceeded those recommended for 6V6 varieties. Beats me how the seller was playing guitar through this thing without blowing tubes and causing meltdowns to occur. E-mail visits with my guru, Stephen Schneider, led me back down the revamp road.



I replaced the power filter capacitors with ones designed to handle more voltages and on Stephen's suggestion ran two of them separate from the can capacitor for hum reduction. I replaced all the electrolytic capacitors and removed the components designed to increase gain. None of this achieved a drop in power section voltage and Stephen suggested adding a zener diode to get the voltages down to reasonable levels (we had done that in the Ol' Smoky amp successfully). This worked, but the bias on the 6V6 tubes were still running way hot. I had put in brand new reissue Tungsol 6V6 tubes and they sound pretty good in the amp, but when I visually tested them in a darkened room, I noticed a faint pink stripe down the sides that indicated a bit of red plating was taking place and could lead to tube failure and a meltdown scenario. The suggestion of running JJ 6V6s, because of their ability to handle higher voltages, solved that problem. They are tonally different from the Tungsols, but sound pretty darned good.




What I thought was a little gritty distortion being produced by the amp (that actually didn't sound too bad) turned out to be a dirty volume pot, and a spritz there cleaned that up. I then went to changing around preamp tubes to see what combinations worked best with my harp mics and speaker cabs. You harp players know the drill. The higher the preamp tube gain, the more likely feedback howl from the amplifier will occur at lower volumes than we'd like. So, we are normally working on being able to achieve the highest volume before feedback, thus lower gain preamp tubes may be the ticket. Since this amp could be boosted just a notch shy of wide open on the volume knob with two of the higher gain 12ax7 tubes slotted for action with a fairly hot mic, then it looked like it would be more of a matter of tone taste than feedback reduction that I would be after. I played around with the usual suspects in the 12a?7 variety and my ears constantly fool me, but right now I'm liking the Tungsol reissue 12ax7 with a 12av7 (a tube that Stephen recommended as a cheaper alternative to the 12au7 or 12ay7 with relatively low gain).




NOW, I had a nice sounding, working 6V6 version for a harmonica amplifier and it fits in neatly between the 1483 and the Kalamazoo in terms of wattage, especially when pushing a 2x10 cab. It'll push the Python, but if I'm going to go through the trouble to haul that cab out, it'll be with the 1483. A nice, new speaker cabinet with a couple of Weber vintage 10s would be an awesome accessory for the Voice of Music, but I'll probably just end up doing a cheap upgrade to the Sunn cab. I do want to try and make a little chassis cabinet for the amp, that I could just stack on top of whatever cab and plug and play. Anyway--Still have a little Sears amp to discuss.

2 comments:

Talonman said...

Thanks so much for your post. I also have one of these amps, and am now thinking I should find me a local amp tech in Columbus Ohio to look mine over. I use it for guitar.

I posted here, looking for help to identify what this amp actually was...
http://www.guitarforums.com/amplifiers/5039-help-me-identify-my-old-tube-amp.html#post90522

Thanks again!

Ricky Bush said...

Hey Talonman--

Thanks for the thanks. Yeah, I'm having a bit of fun with mine now. An amp tech should be able to get it spruced up for you.