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**J M Fahey** · 05-31-2011, 02:37 AM

You can't realistically increase its power , but sticking efficient speakers there will certainly help.
Those C12N are loud and sound close to the original ones; a couple Vintage 30's will provide even louder volume, but will sound more British.

**WolfElectric** · 05-31-2011, 04:25 AM

Talked to a friend today that has knowledge of electronics in general but maybe not specifically to vintage tube amps.

He explained the transformer and how it works.

He also explained that since the amp is all original, the caps are probably dried out and need to be replaced, and that should restore the amp to it's proper 50 watts.

Is it as simple as just that? Or is there anything else I can do to make the amp cleaner and louder???

I hear these amps are generally around 30 watts, even tho they say 50 watts, if I replaced the caps would I get a full clear 50 or just 30??

And to JM Fahey... I thought the stock speakers were c12q's?
And the c12n's are the twin reverb speakers

**soundmasterg** · 05-31-2011, 04:35 AM

With the stock output transformer (about as large as a tweed Princeton output transformer so definitly not a 30 watt output transformer!), you can make the amp about 30 watts RMS. Stock it is 25 watts RMS. The stock output transformer is greatly undersized and reduces the lows and highs that the amp can produce. With the voltages in there on the plates (475v), and if you raise the screen voltage from the 340v that it is to close to the plate voltages, and then replace the output transformer with one intended for a Fender Super Reverb, AND install an adjustable bias circuit and pot, then you should be able to get similar to the Super Reverb in power output levels. Once you do all of that and adjust the bias correctly, the amp is more like 460v or so on the plates and 455v or so on the screens. Make sure to pick some speakers that would match the likely 2 ohm load of the replacement transformer, or pick a transformer that has an appropriate load for the speaker setup. The stock Silvertone 1484 and 1485 had output transformer taps for 4 ohms (in use on 1484) and 2.6 ohms (in use on 1485). I don't know if you've ever looked inside these amps, but all of that is a LOT of work. These amps are rats nests inside and hard to work on, but it can be done. No tech in their right mind would want to do the work without charging you through the nose, but if you do the work yourself, be prepared to spend a LOT of time and be cursing the cheap and shoddy construction on these.

For adding the Fender reverb, it can be done. I did it on my brother's. If you search through the archives here at Ampage and at Hoffman amps bbs you can find info on it, but realistically to do it right, you need to redesign the layout of the tubes in the preamp, build a new headbox for the chassis, add a reverb transformer, add some filtering stages, and mount the reverb pan above the chassis on a galvanized steel plate to help cut down on hum. Trust me, its a LOT of work. You could build a new amp with a much better layout and design for not much more work and it will hum less and sound just as good or better. The stock Silvertone 1484 and 1485 have hum issues, especially if you increase the gain, because channel one's input is mounted right in front of the power transformer.

What I would suggest would be to buy a Silvertone 1485 instead. These use four 6L6GC's and have two output transformers. You can pull two tubes and have basically a 1484, or with all four tubes in, it will be 50 watts, BUT you MUST have a speaker load attached to each output transformer at all times or you will cook one of them, and those tubes will also blow on whichever one does not have a load. That means you need to have some custom cabinet configuration, or carry two speaker cabinets with you. The original 1485 had a cabinet with six 10 inch speakers for a 2.6 ohm load on each output transformer. These are the amps that the White Stripes were using so that is an example of some of the sounds that you can get with these, although I'm sure he was using pedals in addition to the amp sound.

I would forget the reverb idea too unless you like spending a LOT of time redesigning and modifying. The first time I fired my brother's amp up after all the mods I did to it, it squealed and hissed and hummed something fierce and it took me about a year and a half to get the amp all dialed in, and it still hums more than many amps because of the power transformer location and the channel 1 preamp location. Just buy a Holy Grail reverb or even better an outboard Fender Reverb unit and that would solve the problem of the lousy reverb these amps have stock.

Anyway, hope that helps. If you are determined to modify one of these I can provide some tips and ideas from what I did, but I would suggest you check the archives at the forums I mentioned first so I don't have to repeat stuff.

Good luck!

Greg

**soundmasterg** · 05-31-2011, 04:42 AM

Originally posted by WolfElectric View Post

Talked to a friend today that has knowledge of electronics in general but maybe not specifically to vintage tube amps.

He explained the transformer and how it works.

He also explained that since the amp is all original, the caps are probably dried out and need to be replaced, and that should restore the amp to it's proper 50 watts.

Is it as simple as just that? Or is there anything else I can do to make the amp cleaner and louder???

I hear these amps are generally around 30 watts, even tho they say 50 watts, if I replaced the caps would I get a full clear 50 or just 30??

And to JM Fahey... I thought the stock speakers were c12q's?
And the c12n's are the twin reverb speakers

The stock speakers were C12Q's, and the C12N will be a little louder with a little more bass response. The original electrolytic caps are probably all dried up and need to be replaced. The original caps were very poor quality but last a long time. The other problem with that is the can cap is not available. You can have Weber VST custom make one, but it will not be an exact fit and the chassis will have to have a larger hole cut out for the can cap. You could also use individual caps under the chassis but there isn't a lot of room for this. These amps were advertised as 50 watts, but like many vintage companies, they were advertising the peak power and not the true RMS power. The true RMS power of these amps stock is 25 watts. You can make it 30 watts with some mods, or 45-50 watts with a lot of mods. These amps are not something that will get a lot more headroom without a lot of mods, and when you do that, it involves increasing the gain and voltages on the preamp stages, and when you do that, you get a lot more hum and possibility for oscillations. Read my other post on that...its a rats nest and you never know what you will end up with on these if you mod it. The 1485 is a true 50 watts, but see the other post for the caution on the speakers. You might be able to get a 1485, yank both output transformers, and stick in a larger output transformer....I don't think a Twin one would fit unless you used a different head box, and you could probably get 70 watts out of the 1485 since it has four 6L6GC's.

Greg

**Ronsonic** · 05-31-2011, 06:13 AM

Rather than change it that much just start with a Fender Tremo-Vibro-Verb-O-Luxe and be done. It is what it is and will sell for surprising money if it's in decent shape. They really do sound brilliant in their funky way. Except the reverb and like others said, fixing that is a reengineering project.

**J M Fahey** · 05-31-2011, 08:54 AM

So, in a nutshell, the options seem to be:
1) If you already have it, have a technician go through it, replacing dry or leaky capacitors but not really modding it , which would be complicated and very expensive.
For higher cleaner volume use C12N which will still sound original.
2) If you have to buy it, choose a Fender instead.
Silvertones were called "the poor man's Fender" (sort of) and were probably so ... in the 60's, today you could go for the real thing for the same or less cost.

**WolfElectric** · 05-31-2011, 11:12 AM

Hey Greg, thanks so much for such detailed concise information...

ive been waiting to find someone who knew so much about these amps.

ive been in the process of paying off the amp but its just begun.

i kindof jumped the gun on getting the amp cause its in such good shape, then i did some research and realized that (due to practicality in needing more watts) i should have been getting a 1485 all along...

which after research began was an idea id come to fear...
that i put money down on the wrong amp

which sucks cause ill have to save for a while longer... but its the one that i want.

i may lose alittle money from getting the 1484 but i really dont want to get the amp i need...

when i get it if i have a questions youll be hearing from me again!!!

know of anybody who would want to sell one?

ANYONE READING THIS... IF YOU HAVE A SEARS SILVERTONE 1485 AMP AND YOUD BE INTERESTED IN LETTING IT GO, CONTACT ME!!!

**soundmasterg** · 06-01-2011, 04:15 AM

You're welcome. I don't know of anyone at the moment who has a 1485 but they are around here and there. You might be better served to get a 1485 head seperate fromt eh cabinet, and make up a cabinet that will work for you. The head and cabinet combination are a bit more rare than the 1484 and in high demand and cost because of the White Stripes connection. They can be found however....

Greg

**J M Fahey** · 06-01-2011, 05:55 AM

Now that I think of it: if you want it so much that you are ready to wait for it (they are not that common) and to reform it extensively, for age related and quality and safety reasons, why don't you just have somebody build you one?
Modern correctly rated parts, cleaner construction, skipping the kranky reverb which never works anyway.
You might even add a regular, Fender type reverb, yet retain the crude, indie type sound it's famous for.
Just a thought.

**WolfElectric** · 06-02-2011, 12:06 AM

Greg, thank you for your invaluable and greatly DETAILED information...
youre leaving little room for question cause you cover so many bases, and ive needed that.

after pouring thru 30 or so pages of google search results i found a forum with someone who knew someone who had one...
i wrote the guy thru facebook who gave me his friends number.

completely stock. even has the original footswitch!

(PICTURES ATTATCHED BELOW!!!)

the amp is due for a recapping im sure... any place i should be sent to buy the caps? any specific kind youd suggest?

its alittle banged up and dirty (as the original owner has long since stuck to his acoustics)
but its nothing a little elbow grease and amp cleaner and conditioner cant help fix.

the sentemental guy wants to send me pics of the amp in its new home, ill send him pics when ive cleaned and fixed it up.

and to J M Fahey, ive considered getting a custom amp made but aside from the awesome tone i really like the asthetic of the 1400 silvertone amp line.
they look really wierd and cool.

maybe someday ill get a custom one made but id be happier with the real mccoy you know?
ill get the thing reccapped within the month

cant wait to play it at the next two concerts opening for Edward Sharpe & The Magnetic Zeros!!!
check out my crappy recordings here:

Wolf Electric | Facebook

Attached Files

**anthillrich** · 06-02-2011, 02:23 AM

The 1484 is a great amp. 25watts, 30 watts, whatever, its plenty loud to play in a band setting.

Don't cut holes in the chasis for custom cap cans, don't do any silly mods, etc, just have a qualified tech do a cap job, and put a 3 prong plug on it.... and start gigging.
Which by the way, would not be all that complicated or even difficult for a good tech.
Even in that "rats nest".
you could spend your time saving for the perfect amp, or you could start playing one that you already dig. seems like a no brainer.

**soundmasterg** · 06-04-2011, 05:07 AM

Originally posted by anthillrich View Post

The 1484 is a great amp. 25watts, 30 watts, whatever, its plenty loud to play in a band setting.

Don't cut holes in the chasis for custom cap cans, don't do any silly mods, etc, just have a qualified tech do a cap job, and put a 3 prong plug on it.... and start gigging.
Which by the way, would not be all that complicated or even difficult for a good tech.
Even in that "rats nest".
you could spend your time saving for the perfect amp, or you could start playing one that you already dig. seems like a no brainer.

There are not any stock can replacement available for these since Vibroworld stopped business operations and as a result stopped making their custom cap cans that were the same as the originals. So you either have to go with a different custom cap can like the Webers that don't quite fit correctly, or leave the can in place and stick discrete caps under the chassis in what little space is in there. The adjustable bias with a voltage doubler mod is a good one to make because the stock bias tap does not have enough voltage available so the tubes are biased too hot and wear out sooner than they would if the bias was set correctly. There was no bias adjustment on these either. These amps will never be as valuable as a vintage Fender, Vox, or Marshall, and if you get one that is already messed up like the one my brother has, then you may as well change it to make things better. I have a pristine and completely working 1484 here that I don't plan on modding myself, aside from the bias change. It has one of the last custom cap cans that Vibroworld did in it so it will be good for a long time. By elaborating on the mods I did to my brother's and calling the amp a rats nest, I was trying to caution the original poster against spending the time to try to make a 1484 into something that it isn't. It can be made to sound better, and be louder, but it isn't really worth the time invested to tear into these on such a scale when you can build yourself a kit and spend less time, and have a better sound.

You're welcome WolfElectric. For the caps, Antique Electronics Supply has most of what you need. Mouser also has a lot of stuff, though you have to hunt in their catalog sometimes to find what you need. The caps in the doubler do not need to be super high voltage...I think the stock ones are 100 uf 150v or something like that. You could increase the actual value of the caps in the doubler though and get some hum reduction and it will not change the tone. The bass may be a little quicker, but probably not with such a small output transformer. Since that design in the 1484 and 1485 use two doublers stacked on top of each other, the actual cap value the amp is seeing is one 25uf cap, which is pretty low for a main filter. If you went with 220uf 150v caps, then you would essentially end up with the equivilant of 60uf in the first section, which should be sufficient. The can cap....well you will have to figure out what you need to do there. The options are a custom Weber can that will be a little too large, and if you have a Greenlee punch of the correct size you can make the hole a little larger to fit the cap. You can also look into using individual caps inside the chassis, mounted around where the can is, but you would have to drill some holes and add a couple terminal strips to make it safe. The coupling caps inside the amp, the brown ones, are pretty crappy caps, and were from day one. They will probably still be working ok and not leaking DC, but they are very low quality caps with high ESR. Pretty much any modern cap like a Mallory 150 or POLYESTER Orange Drop like the PS series would work fine. Don't get the polypropylene Orange Drops like the 715P's or 716P's as they are not going to sound correct. The resistors are all 20% tolerance and are poor quality. Some of them may still be in spec, but you may have to replace some too. Certainly the plate resistors on the preamp and phase inverter stages should be replaced. Make sure to use modern carbon comp resistors or the sound will change. For the other resistor positions in the amp like cathodes, grid leaks, etc., metal film resistors will give less noise and sound just fine. Its your decision if you want to mss with the "vintage mojo" or not on changing caps and resistors, but I would make sure to check every resistor and make sure it is within 20% of whatever the value on the resistor states that it is.

As far as other mods....the 3 wire grounded power cord is a must. Get rid of the death cap and wire up the power stuff correctly. The black(hot) wire needs to go from the wall, through a fuse, then to the switch, then to one of the primary wires on the power transformer. The white wire(neutral) needs to go directly to the other primary wire on the transformer. You will have to add a couple terminal strips and drill a couple holes to do this correctly and safely. Back in the day they put the fuse and switch on opposite sides of the line, and so the wires aren't close to correct now and are spaced such that you will have to add the terminal strips for it to be safe. Maybe a one or two hole strip with one hole in the chassis per strip would be sufficient. I would have to open mine up to see and I have too much going on right now to do that. The other mod that I would do for sure is to add a voltage doubler circuit to the bias supply, and add a pot to make it adjustable. I can look through my notes and see what values I used in my brother's amp if it helps you. You may also consider replacing the pots. Certainly try to clean them with some DeOxit, but they were poor and often get frozen up with age or get noisy. Make sure the nuts holding those on are tight as if not the amp will make strange crackling sounds. Any other mods past those you will have to decide if you want to do.

Also, MAKE SURE to run the amp into that cabinet or have a load on both output transformers at all times. If you only want to use one half of the amp and get lower pwoer and volume, then you need to pull either the left two tubes, or the right two tubes, and then run an appropriate load. The 1485 stock is a 2.6 ohm load for each output transformer. The stock setup for the 1484 is 4 ohms, so it is wired appropriately. If you wish to use a different cabinet or lessor power by pulling two tubes, then you may want to rewire the outputs so that the 2.6 ohm and 4 ohm taps are accessible from the back with some jacks, appropriately labelled of course. If you decided to do this, then you would have four jacks on the back, two 2.6 and two 4, one each for each output transformer and pair of output tubes. Easiest approach of course is to always run it into the stock cabinet.

Are you going to do the work yourself, or take it to a tech? If you were in the area I'd say stop by and I could help you with it, but you're probably a long ways away from Oregon I'm guessing. There are good techs around though. Show them my suggestions if you want and they can email me or call me if they need to.

Greg

P.S. I was going to build myself an amp that would have a similar look to a 1484/1485 and a circuit similar to what I did to my brother's 1484, but I haven't gotten around to it yet. I have the head box done, and the chassis cut out and welded, but no holes drilled or circuit done for it yet. One of these days I guess! I suppose if someone was paying me to do a custom amp for them I would have it done quicker...haha. Anyway, glad you were able to find an amp so soon!

**WolfElectric** · 06-28-2011, 01:25 AM

Hey Greg, another question

(my name is Johnny btw)

So, the amp arrived, and the tremolo/reverb footswitch wasnt secured and it broke one of the main 6L6GC tubes...

the day it arrived i ordered another RCA 6L6GC Blackplate tube

did some more research, and im seeing that unmatched tubes can affect tone and shorten tube life.

im assuming the 3 original tubes were matching but could it really be that much harm to throw in one tube that is the same make and model just not matched?

any suggestions?

ive read alot on the RCA Blackplates and i really want to use them, all the other tubes are stock and sound fantastic with the JJ 6L6GC's i had put in

just to try i put in all new tubes, to hear the contrast between the stock (3) 12AX7s and (2) 6FQ7/6CG7's and JJ/electro harmonix replacements.

the contrast is incredible, the jj's were really bright and thin, and the RCAs sound AMAZING, so much depth, detail and warmth and dynamic.

im a believer, i understand the hype of the RCA Blackplates

the JJ's sound great but if the JJ's had that much contrast with the other tubes id be really curious to see how the RCA 6L6GC's would sound instead of the JJ 6L6GC's.

i really want to just throw in those tubes and see but i dont want to damage them all.

im assuming the 3 (out of 4) RCA 6L6GC's are matching, any input how to make the one tube match the others?

i really dont want to take the tubes to someone to have thier specs taken so i can but ANOTHER RCA 6L6GC, id like to use what ive got if possible.

im going to throw them in and JUST try them regardless when my tech is done with the amp, if the jjs sound better (which i doubt) then ill stick with the JJ's.

theres a pretty revered local tube amp tech my bassist knows that could make something work for me im sure but i wanted to see if there was anything you could shoot over to my tech first if there were any options...

like putting a bias on just that one tube??? i dont know, im still learning.
thats why im asking questions

---------------------

and to update you or anyone following this

my tech read everything youve written me and used that info in buying Caps for everything.

Hes got my amp, the caps come in wednesday and hopefully i can use the amp this Friday at Forest Fair in Girdwood, Alaska.

for reverb, i did a ton of research and saw some people even throwing digital reverb chips into amps for the ease of installation.

and since i LOVE my electroharmonix holy grail reverb i handed that to my tech, hes going to mount the chip of the pedal in the amp and cut off the stock reverb path and put that chip in the amp instead.

the depth knob wiring on the EH H.G. will be extended to replace the "reverb" knob on the front of the amp

im really excited. hes gotten rid of all the crackle in cleaning as many contacts as possible.

the amp wasnt as loud as it should be as the volume had to be turned to 3 to begin getting volume but hes got that figured out.

hes putting in one of those 3 prong computer jacks so a computer cable can power the amp and just detatch for storage. and it will solve the ground issue

and hes eliminating the 25 foot cable and putting in 1/4 inch jacks to make the head and cab connect like modern amps

it cleaned up so nice too...

my tech may use dry ice to get the dent out of the face of the amp.

i just want it functoning properly first tho.

anyways, just thought id ask more questions and update you

thanks Greg!

(btw, i attatched before and after pics)

Attached Files

**Archieaa1** · 11-10-2013, 09:23 PM

Originally posted by WolfElectric View Post

So... ive been doing some research for the Sears Silvertone 1484 im about to
aquire

im in a band (Wolf Electric... Wolf Electric | Facebook) and even
tho i have tried one of these amps out briefly (and fell in love) a few
years ago im alittle concerned whether im going to be able to keep up with
the rest of the decibels my bandmates will be pushing out.

i hear these the output transformers in these amps will be (as ive
researched) about 30 watts (even though specs say 50 watts)

i want to make this amp a true 50-60 watt amp... how can i do that?

is this even a realistic request???

To put it simply, No it's not reasonable. Anything you do to the amp that would get it up to more or less twice the power output would absolutely change the sound and character of the amp. Don't worry about the power output. While you may be able to measure the difference in volume between 30 and 60 watts. If you use the same speakers, you will have a hard time hearing the difference. The overall volume has much more to do with the efficiency of the speakers and enclosures than the output of the amplifier. Old speakers are subject to a couple of problems that can make them quieter than new ones. The magnets can weaken overtime, The coils can move from failing glues. Both of these will make old speakers lose volume.

Even if we assume that speakers are perfectly linear, which they are not, The big problem here is that volume is a Logarithmic function. In this case it's a Log 10 function. What this means is to achieve twice the apparent volume you would need 10 times the power. In practice it takes even more than that. When we talk about a 60 watt speaker what we are speaking of are the thermal limits of the voice coil. The figures you really need to look at to understand how loud the speaker can get are A) Xmax which is a measure of how far the cone can travel and B) efficiency, usually described in terms of db at 1 watt/1 meter.

A speaker with high efficiency numbers but, low Xmax will make a lot of sound with a little power but, it will quickly compress as you add more power. by comparison a speaker with a much bigger Xmax and a slightly lower efficiency rating will in practice make more sound with added power. A lot of the early speakers used in guitar amps are of the high efficiency but, low Xmax flavor and as such you don't get the volume you might like from them as you go to bigger and bigger amps.

The way to beat this is to use more speakers. Most speaker will reach their mechanical limits well before they reach their thermal limits. Lets take speaker A that we will feed with a 40 watt amp. It's rated for 50 watts and 3mm Xmax. We test it and we find that it reaches the limits of X max at 20 watts input. Any power you feed it after 20 watts will not get you more sound. It just ends up as heat in the voice coil. the Xmax times the area of the cone tells us how much air it can move. This is fixed. Lets now take speaker B. its a 20 watt speaker with a 2mm Xmax. It reaches Xmax at 10 watts input. If we put four of speaker B into a cabinet and feed it 40 watts, something very different happens. Each speaker gets 10 watts drive so they reach their 2mm Xmax but we are moving 4 cones 2mm each. This gives us an effective displacement of 8mm which will move a lot more air than the single speaker. More drivers almost always win. It's rare to find a 12 inch guitar speaker which has an Xmax figure of 5mm. Most are less. The Xmax figure on my Cannibis Rex is about 1mm.

I haven't gigged with anything larger than a 30 watt amp in many years with the exception of using a Super Reverb from time to time. I usually use a Laney GC30 with a single eminence Cannabis Rex. Its just starting to break up a little with the band. If I need more volume I use my AC30-CC2. It's surprisingly louder but it's still a 30 watt amp. The difference is the speakers. These are both amps that use about 300 volts on a quartet of EL84 tubes. The laney output tranny is somewhat smaller so it does saturate easier but, that's part of the sound. it's still plenty loud enough for most clubs. Before I got the AC30, when I needed more volume, I would use a more efficient speaker cab (you can read that as meaning a 4x12 Marshall style cab) with the laney for more sound.

I hope this helps in your quest.....

Archie

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Output Transformer/Reverb Upgrade for Sears Silvertone 1484

Output Transformer/Reverb Upgrade for Sears Silvertone 1484

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