Two questions re: Silvertone 1484

[Dino_k]

Am the new owner of a Silvertone Twin Twelve 1484 (head only) and have been poring over the schematic and online comments. The two questions that come to mind for this amp are:

(1) Can the plate voltages on the Channel 1 be safely raised enough to make Channel 1 a clean channel, with Channel 2 as the gain channel?

and (2) The reverb sucks, I get it plus I kind of hate reverb anyhow. One of the old "mods" to Fender amps was to unplug the reverb connectors from the pan and directly connect them to each other with nominal resistance in line and the reverb knob and footswitch effectively became a boost switch. Can this be done with the 1484? The reverb circuitry has a different topology and I'm not sure that the piezo driver circuitry can just be bypassed and used as a boost circuit.

Appreciate any input.

Dino

[olddawg]

Speaking as someone who put five 1484 chassis in a dumpster around 1981 (They were worthless at the time) and someone that owns a couple now, I can tell you that these amps do not mod easily. A couple of popular artist used them in recent years so they have become desireable. They will give you that raunchy "Silvertone" sound but little else without a lot of trouble. If you want a different amp you should just get a different amp IMHO. Restore this one and sell it. Modding it will make it worthless and you will never have what you want. As far as I know you can't jump the piezio and it is not cost effective to re-engineer the power supply for more B+. Seriously. It isn't a Fender. It's a quirk, handwired nightmare if you dig into it.

[soundmasterg]

Am the new owner of a Silvertone Twin Twelve 1484 (head only) and have been poring over the schematic and online comments. The two questions that come to mind for this amp are:

(1) Can the plate voltages on the Channel 1 be safely raised enough to make Channel 1 a clean channel, with Channel 2 as the gain channel?

and (2) The reverb sucks, I get it plus I kind of hate reverb anyhow. One of the old "mods" to Fender amps was to unplug the reverb connectors from the pan and directly connect them to each other with nominal resistance in line and the reverb knob and footswitch effectively became a boost switch. Can this be done with the 1484? The reverb circuitry has a different topology and I'm not sure that the piezo driver circuitry can just be bypassed and used as a boost circuit.

Appreciate any input.

Dino

These amps are a PITA to work on as has been noted. They can be modded to give better sound, though you lose some of the Silvertone character when you do that. If you want to change channel 1 significantly from channel 2, then you would have to run a parallel filtering arrangement, and adjust dropping resistors for both channels accordingly to get the voltages where you would like them for the modded channel, and back to stock for the other channel. It can be done, but it won't be easy due to limited space in the chassis for mods of that nature. The easiest way would be to add another can cap, due to space limitations, but I'm on record (here and other sites) as not liking can caps for various reasons. The amp can be increased in power too, up to around 30 watts RMS instead of the 25 that it has stock. It is simple to do this...move the screen supply to a higher voltage tap on the doublers, and add a seperate filter node for it. If you want to change the voicing of one channel without affecting the other, and you want to do so with the least amount of work, then seperate the cathodes in the preamp from each other, and change resistors and caps accordingly to get the sounds you want. The 1484 often is using high value cathode resistors with no cap and going towards more Fender territory with those parts choices can get a brighter, cleaner sound. One highly recommended mod is to add a voltage doubler to the bias supply to get the bias into a safe range, and add a pot and associated circuitry to make it adjustable.

Greg

[Ronsonic]

Speaking as someone who put five 1484 chassis in a dumpster around 1981 (They were worthless at the time) and someone that owns a couple now, I can tell you that these amps do not mod easily. A couple of popular artist used them in recent years so they have become desireable. They will give you that raunchy "Silvertone" sound but little else without a lot of trouble. If you want a different amp you should just get a different amp IMHO. Restore this one and sell it. Modding it will make it worthless and you will never have what you want. As far as I know you can't jump the piezio and it is not cost effective to re-engineer the power supply for more B+. Seriously. It isn't a Fender. It's a quirk, handwired nightmare if you dig into it.

This

It am what it am.

[Dino_k]

Greg,

Thanks for the info. I'm okay with the current output power of the amp, though I may try the screen voltage mod just for fun. Interestingly, the previous owner had a pair of ancient Raytheon 6V6GTA's in it, instead of 6L6's. I'm guessing it is probably pumping out a nice crunchy 14 watts or so. I'll be doing a little tube rolling on it to find which power tubes it seems to like best and work from there. I'm thinking the TAD 6L6's might be a nice, although the JJ 6V6's may be nice too.


Olddawg,

I hear you, brother. It can be scary in some of those old lower end circuits. But it's not about the cost or getting the amp I want. I'm afraid I suffer from PMSS - Permanently Modifying Stuff Syndrome - and I've got more little monsters in my basement than Dr. Moreau. The 1484 is a safe, if not easy, victim in that it has no inherent value, is relatively primitive, and won't incur the wrath of my "don't touch a blackface" friends!

[soundmasterg]

Dino, the Sovtek 5881 actually sounds pretty good in these with an adjustable bias in the amp, and then bias hot. My brother's that I modded the piss out of is currently using Winged C 6L6GC's, though he and I both think the Sovteks sounded better. I never measured the actual output power of the amp before I modded it but I'd guess a stock 1484 is around 25 watts RMS before clipping. My brother's is 30 watts....not a lot of difference, but worth an added resistor, cap, terminal board and some wire, and a moved screen tap wire. The JJ 6V6's would probably sound pretty good in that amp, though we stuck with the 6L6 family.....he needed the power to keep up with Deluxe Reverbs up loud. With the small output transformer in the 1484, it restricts the power and bandwidth a lot to where the 30 watts 1484 is right about the same as the 22 watt Deluxe Reverb. A bigger OT would likely bump the output power up to around Super Reverb levels, with a better headroom too, but my brothe ris fine for now with the lower power.

Greg

[Ronsonic]

I hear you, brother. It can be scary in some of those old lower end circuits. But it's not about the cost or getting the amp I want. I'm afraid I suffer from PMSS - Permanently Modifying Stuff Syndrome - and I've got more little monsters in my basement than Dr. Moreau. The 1484 is a safe, if not easy, victim in that it has no inherent value, is relatively primitive, and won't incur the wrath of my "don't touch a blackface" friends!

Check the prices before you say that. Modded it is worthless. As is, it will sell for enough to buy a whole amp worth of quality parts or attract another more suitable victim into your basement.

[andyjazz]

I just finished a bunch of work on a 1484. The replacements caps I ordered were of slightly different values than the originals (which of course is typical) but my feeling is that by simply replacing these old caps with their modern and more efficient equivalents actually increases the gain and efficiency of these old amps. Other than 5 electrolytics and a couple of new bypass caps all I did was resolder a bunch of crappy connections (Including the reverb circuit, which rendered a noticable improvement) and replace a couple of pots that literally disintigrated in front of me.

And yes the 1484 is tricky to work on, but IMHO well worth your effort. Bottom line is, this amp is one the best diode-rectifier amps I've ever heard when paired with the right bottom. I suggest a closed back 4x12. (A closed back 2x12 is ok too) I'm with the "Run it like it was meant to be run" crowd. Use the 6L6's and all the caps and bias resistors the amp was designed for. The amp will love you back. You won't be dissapointed.

[andyjazz]

One more thing I should mention. Alot of these older amps will have the ground of the input jacks supplied by the physical connection of the nut and tooth washer on the chassis, or whatever serves as "the chassis." There will be nothing soldered to the shield of the input jack. This is "electronically" acceptable for a ground, however, whenever I get one of these amps I make sure to supply the inputs with a direct wire coupling from the shield lug of the input jack to a solid chassis ground, like the lug of the PT or something. Ground is reference for your signal. It is critical.