Friday, January 16, 2009

Once More With Feeling ('nother Silvertone mod)

I've posted up most everything that I tweaked on the 1483 Silvertone amp to make it quite a substantial blues harp amp and also how Stephen S would always find one more mod to make it sound better. One of the last tweaks that I kept putting off, because I felt the amp sounded as good as it was going to get, was to beef up the first stage power supply filter capacitor--I had raised its value from 16mfd to 20mfd when I originally replaced the filter caps, but he was suggesting doubling that. He had recommended the same mod for my Kalamazoo Model One and I put it off for the same reason--it sounded darned fine as it was. But, as I related in an earlier post, I did jump into the Kalamazoo and it fattened it up and beefed up the bottom end and made a great harp amp better. So, I tackled the 1483 the first part of this week.

I replaced the Sprague 20mfd cap with a 47mfd/500v F&T capacitor (that's the large black cap pictured towards the left in the chassis picture) , which is substantially smaller than the Spragues. I put the amp through its paces and it is certainly more floor thumping and has lost no articulation with the added whomp. Like with the 'Zoo, I don't know why I put off doing this. It took me all of 15 minutes and is completely reversible (which won't be happening).

I know that after the Kalamazoo mod, I had read on one of the harp bulletin boards, from a respected amp tech, that he doesn't do the mod on the Kalamazoos that he refurbishes because it changes the character of the amp. Well, these are amps designed for guitar (in the case of the 1483, Sears sold it as a bass amp), so we harp players are trying to change the characteristics of these amps--aren't we?. To each his own, but no one has to ask, "Where's the beef?" with these two amps--and the smaller of the two needed it most. Stephen is dickering around with a '58 Gibsonette to see what beef he can coax from it right now. I'm interested in hearing how that turns out.

For those that are curious. I've played around with oodles of preamp tube swaps in the 1483 to get the right tones happening with the least feedback problems. The combination that I'm liking at the moment is a GE NOS 12au7 with a Tung Sol Reissue 12ax7. I really do like what I'm hearing with this combination and I really like the Tung Sol. In the past, a 12au7 with any combination was just lifeless and a 12ax7 in any combination fed the feedback monster, but the Tung Sol is so robust that the 12au7 can't kill its tone and compliments it nicely. I tried an EH 12ay7 with the Tung Sol, but things were a little too touchy with that pair. Now, if there was just a stage around here to place the 1483/4x10 cab upon, I could see if it passes a real world test. Anyway--


Anonymous said...

You have mentioned Silvertone 1483 amp head. I will soon have one of these & would like to build a 4x10 cab. Inqueries about speakers just blows me away. Have heard good things about Weber 10a125-0 but then again they have their non-supporters also. What is your opinion os speakers with the Silvertone in mind or other amps.

Ricky Bush said...

Hey Anon--

I'm far from any where close to being knowledgeable about speaker choices. My choices for my cab where made by researching opinions just like you are doing. I like the Weber 100As/Sig ceramic combo just fine, but I've never compared them to any others.

AM Funk said...

Hey Mr Bush:
I have a Silvertone 1843 that I bought on-line from a guy out in NC for a very reasonable price. He recommened an amp tech near him to do some mods,(now I started spending real cash). Although it sounds pretty good I was unable to move vol controls very high before feedback (familiar topic). Well after some on-line research opted to remove 12AX7 & replace with??? Have used 12Au7,12aY7,12aT7, have 5751 on order now (spending more money, the experiment continues). Question the 6FQ7 phase inverter tube, can it be replace with some of the examples above? What has been your experiance with tube swapping in the 1483?
Thanks, near StLouis A.M. Funk

Ricky Bush said...

Hey Mr. Funk--Good luck with the 1483. I've stuck all the tubes in the pre-amp that you've mentioned. I believe that the 12au7 robbed too much oomph. I have two 12ay7s in there right now, but sometimes I'll run one 12ax7. Some brands are hotter than others. No, I don't believe a sub for the 6FQ7 is available. 3 or so on the volume knob seems about average. Rarely makes it above four.