Tube Amps / Music Electronics
|For current discussions, please visit Music Electronics Forum.||New: view Recent Searches.
New: visit Schematic Hell!
The sunn still shines online!
|Listen to great tunes streaming live right now!|
|previous: George Thanks for the note. Sounds like yo... -- 6/23/2004 8:09 PM||View Thread|
|6/24/2004 7:30 PM|
|Greg Simon||Re: Silvertone 1484|
Hi George. Thanks for the compliments. Over the last 5 years or so, I've gotten all the books I can about tube amps, and asked a lot of questions. There is a LOT that I don't know however, especially when it comes to hands on work with the amps. At this point in my experience, I feel book smart but not experience smart. I'm working on correcting that, of course, but it takes time!
Having said that, I can give you some decent advice with the 1484 Silvertone that will help you get it up and running reliably. KOC is Kevin O' Connor and TUT3 is one of the books he has written called Tonnes of Tone Volume 3. His books are expensive, usually around $50, but they are the best out there for modding and restoring tube amps in my opinion. He's also a great guy and frequently posts on Ampage. His site is www.londonpower.com. He's in Canada.
If you're just starting out with amps, and you are committed to increasing your knowledge, I would start with the Tube Amp Book by Dave Funk, and then get TUT3 from KOC. You can get both from Antique Electronics. Their site is www.tubesandmore.com. You can get supplies there also.
The reasons for not messing with the reverb are that
1. It sounds really crummy stock.
2. To make it sound nice isn't really worth the effort in that amp.
3. If you take those tubes out, then you can add more tubes for preamp mods, and/or replace existing tubes with some that draw more filament current and your power transformer won't have as many problems trying to keep up.
As far as which tubes those are...I'm not sure offhand...I'd have to check the schematic, and I don't have it in front of me. You should be able to get it from www.schematicheaven.com. Its also in the Groove Tube and the Gerald Weber books. I have it at home and could email it to you if you can't find it. Let me know if you need it.
If you cahnge to 12AX7's, then yes you would have to rewire the sockets and change some resistors, or at least move them to the proper pins on the socket. The only reason to do this is because 12AX7's are easier to find, cheaper, and will be quieter because they have a humbucking filament option depending on how you wire up the filament. The ones that are in there don't. The gain between the ones that are in there and a 12ax7 are pretty close to each other to where the sound won't completely change.
If you add a gain stage, I would only do it if you are getting rid of the reverb. As I said before, you can use those tubes/sockets to wire up another channel or more gain stages, etc. As you go up in gain however, you can run into oscillation problems. There is a lot of this mentioned and elaborated on in TUT3, though if you're a newbie, it may take lots of reading to understand it. You could always just remove the reverb tubes and otherwise don't add any more gain stages and that would still provide a benefit because your power transformer would run cooler. Since these Silvertones were made to be sold in Sears they use lower quality parts than a Fender for example...so they aren't as reliable. Anything that can be done to make the PT last longer and not heat up would be good. Thats not to say it will fail tomorrow, because my brother's are still original...but its something to think about.
I think a Silvertone 1484 head with a decent cabinet is a great amp to get you a decent tone at various volumes. Stock, they are a nice blues amp at moderate to loud volumes. Many people complain because they are darker sounding than even a tweed Fender, and they don't have much power compared to a Fender. What I mean by that is that they get distorted sooner in the volume range than a comparable Fender. Some of that is due to the smaller output transformer, and putting in a bigger, better quality output transformer will get you a cleaner tone higher up into the volume range. It may sound better just because of that one change. Channel 1 and Channel 2 are almost identical on these amps. Since Channel 2 has tremelo, then I say mod channel 1 to be a different tone if you want to mod something. Thats not super hard to do....change a couple resistors and caps and you can have a completely different sound. You can change the voltages too going to the tubes to change the sound. You do this by changing resistor values in the power supply section.
If you really wanted the amp to perform, then I would say to completely rebuild it...replacing all the caps in the amp with modern replacements, and replacing many of the carbon comp resistors with new carbon films or metal films. There are a couple places in the amp where carbon comps may still be desired, for sound reasons, but I would still replace them with new ones rather than using the old ones. My brother's amp needs new plate resistors because it gets a crackling noise sometimes from them. Make sure that whatever resistors and caps you use have a high enough voltage rating! The other thing to do would be to completely redo the grounding scheme. While you're at it, may want to redo the standby setup also and make it more like a Marshall or Fender. The grounding is just like all the old amps where they ground everything to the chassis, which makes multiple ground paths and increases hum and a chance for oscillation. KOC's TUT3 is really good here for recommendations, but the gist is to isolate all the grounds from the chassis, and use isolated input and output jacks. Then you use a ground lift switch and that is the only point the grounds touch the chassis. Also, if you decouple each stage from each other using filter caps and resistors, then the amp will perform better. As you get more gain out of a circuit, this becomes a necessity. Basically the term KOC uses for the grounding recommendations is to wire it up as a galactic ground scheme. Theres a lot of people who have tried it on this bbs and really like it, but it does require a bit of work. One other useful mod would be to change the power supply section a bit. Right now it is a half wave voltage doubler. You can change it to a full wave voltage doubler scheme and get better regulation so the power supply won't sag as much under a high load. Adding a choke for the screens would probably help things too.
Because these amps were cheap, there are a lot of compromises that were made with them. You can improve some things, but even if you did all of these mods, it is still a Silvertone and isn't ever going to be worth a ton of money. There is also compromises that were made in layout which you have to live with. Having said that though, they are a nice amp stock, and modding it to improve some things can make it into a really nice amp. If you don't plan to make money off it and plan to keep it, then go to town! If you've never done this before, then get some books and read up. Find some old tube guys and engineers and ask lots of questions. You want to be safe first and foremost! Look at the schematic and compare it to your amp. Maybe draw up a layout of the amp on a big piece of paper and label all the parts. That helped me understand it a lot better. Then when you decide to make changes, the mechanical part of doing that is easier too because you can plan it all out on paper first. Hope that helps and I'll let you know about the 2x10 when its done!
|Greg Simon One thing I forgot to mention is th... -- 6/24/2004 7:40 PM|