Choosing transformers

[miltown]

I have an old Silvertone 1331 amp. I wanted to change out the transformers and was wondering what specs I would need for Power and output trans. The Power is 30 W 30mA 270V sec. and the output is 10w 4ohm . Do I have to watch the pri. impedance on the output trans. ie.. 4kohm or 5kohm. I was feeling that switching the transformers would give me better tone, I'm I correct in assuming this?. It is a pretty basic amp.


paul

[R.G.]

I have an old Silvertone 1331 amp. I wanted to change out the transformers and was wondering what specs I would need for Power and output trans.

Of course, this would also destroy any value the amp would have to a collector. There are people who collect Silvertones. Don't know about this particular model though.

Also, any substantial change of the power and output transformers may cascade into changed rectifers, filter caps, power tubes - it's hard to decide when, where, and how to stop.

I was feeling that switching the transformers would give me better tone,

(a) What was this feeling based on?
and
(b) Define "better tone." No, that's not rhetorical, nor sniping. Tone is not a single quantity. As the saying goes, if you don't know where you're going, any road is as good an any other.

I'm I correct in assuming this?

No.

Do I have to watch the pri. impedance on the output trans. ie.. 4kohm or 5kohm.

Yes. However, it depends a lot on what tubes and circuits are involved. There is no simple way to say that 4K is better than 5K, even if you know which direction "better" lies. It's a much more complex issue than X transformers giving better tone.

We identified a health problem over in the effects forums. We called it "Blind Urge to Mod Syndrome", or BUMS for short. It's a progressive condition caused by reading amp and effects mods posts on the internet. It's not clear whether it's treatable or not.

[guitarmike2107]

when you have BUMS, you may need this fault finding sheet to help you sort it out afterwards

http://hqvia.com/wp-content/uploads/...et-420x499.jpg

[miltown]

Well I guess that answers my question!?!? I have read on forums about changing out transformers to improve the quality of the sound. I guess tone might be the wrong word. I'm not a collector nor wish to collect so the whole value issue is unimportant to me. Right know I'm learning so I think you kinda have to go through BUMS to learn. So I guess I'm a BUM.

[R.G.]

Well I guess that answers my question!?!? I have read on forums about changing out transformers to improve the quality of the sound. I guess tone might be the wrong word. I'm not a collector nor wish to collect so the whole value issue is unimportant to me. Right know I'm learning so I think you kinda have to go through BUMS to learn. So I guess I'm a BUM.

Don't get me wrong - I strongly believe in private property rights; if you own it, and you want to "improve" it in any way you like, all the way to shredding it into bits, that's your option and I strongly support your being left alone to do it. If collector value is not important to you, go ahead on. It's yours.

I also strongly believe in knowing what one is getting into. No one can make a responsible decision without information. Hence my advice.

If you know what you're doing in terms of using up an amplifier to learn on, that's fine too. I'm also a proponent of the idea that the "victim" of a learning experiment is a disposable part of the learning.

What I don't agree with is people accepting advice about the magical qualities of this or that "hand wired point to point with oxygen free solid silver wire by Icelandic virgins on the night of a full moon...", or just simple admonitions about "more/better tone".

If you're learning, it's important to learn to separate wheat from chaff, too. And that gets me back to this post.

Can you define, not for me, but for yourself, what "improve the quality of the sound" might mean? Unless and until you can, you're very, very unlikely to get there in any way but luck.

Don't take this as sarcasm. It's level-headed advice. You do not have to go through BUMS to learn. It's the BLIND part I object to. Get unblinded first, or get ready to toss away a lot of money, time and parts.

[miltown]

What I see alot on forums about stereo tube amps is talk about getting better transformers or transformers better suited for audio.I guess I was looking for an answer as to the part a trans. would play in the circuit aside from voltage supplies and impedance matching. I understand to some degree about increasing or decreasing supply voltages and the effects they have on the circuit. Basically will a (just for the sake of argument) a Fender trans. with the same specs as a Silvertone trans. perform better , or is it apples to apples at that point? The sound I'm looking for is basically a clean signal with just a touch of distortion I guess. I want it clean. The amp right now is not a very clean sound. It was the lowest level amp that Silvertone made. I have replaced all the components one for one and it sounds better than when I purchased it but not still were I imagine I want it. The tubes are still the ones that came with it (6V6Gt ,6SJ7) . I know there is things like bias level, speaker selection, plate voltages and neg. feedback that can clean this up and I guess that is what will happen next. I was just wondering if (like other similar products) if a transformer is a transformer or one is better or more stable or what have you ,than the other. My question seems to have been misstated from the beginning.

[Steve Conner]

RG is being kind of mean today but there is a grain of truth in what he says. These little amps were never meant to generate lots of clean power. They're always going to sound a little funky and dirty.

If your amp seems to lack headroom the first step is always to make sure that it's actually working properly. Old, worn-out tubes and other bad components can lead to a weak, distorted tone. These little 3 watt amps (it's not 10 watts! that's a marketing figure) should be about as loud as a trumpet by the time they start to distort, and plenty loud enough to annoy your neighbours, but they won't keep up with a rock drummer.

A larger output transformer is an easy and popular mod for these small single-ended amps. It seems that the physically larger and heavier the transformer is, the louder and beefier the sound you get, but possibly to the point of endangering a cheap and nasty speaker. It's not snake oil, there are sound scientific reasons why a bigger OT will make more volume and bass. Any transformer meant for upgrading a Fender Champ, Epiphone Valve Jr. etc. will almost certainly work.

I wouldn't recommend changing the power transformer for a higher voltage one. The 6X5 rectifier tube could get stressed. And if you change it for another of the same voltage, it's not going to make any difference to the sound.

But as I said, the first step is to make sure the amp is in good shape before starting to tweak it.

All sizes | Silvertone 1331 schematics | Flickr - Photo Sharing!

[MWJB]

"Basically will a (just for the sake of argument) a Fender trans. with the same specs as a Silvertone trans. perform better , or is it apples to apples at that point?" As far as the power transformer goes, there probably won't be a Fender style part that is directly comparable (the Silvertone runs a 6.3VAC rectifier compared to the Fender's 5VAC 2A rectifier), Fender ran their tubes at higher voltages than most other manufacturers, so If you did fit a Fender style PT, then you might see an additional 50-100vdc on the 6V6 plates & a considerable change in tone.

As far as output transformers go, anything that matches a 6V6 to a 3.2/4ohm speaker will work, again the Fender item is somewhat beefier & probably has a higher primary impedance...but, these are just 2 aspects that seperate the 1331 from an equivalent Fender...almost every other part is different & running at different voltages. You say that you have restored the 1331...good work, but did it/will it ever sound like what you imagine it will? Perhaps compare it to another 1331 to see whether it is ballpark/improved, or otherwise. You could initially try some circuit mods (after ascertaining exactly what it is you want more/less of), but really, to gut & rewire the amp, sub transformers in a bid to make it more Fender-like is more work than just building a Fender 5F1.

Really any small amp can be overdriven, if you want clean then a much later amp design and/or push-pull is the better bet. Your amp could be converted to a simple self-split, push-pull with a change of power tube (6SN7), rewiring of the power tube socket, change of speaker...but you would still have to do some mods to the preamp, such as raise preamp voltage & perhaps replace the 6SJ7 with a 6SL7 & rewire tone & volume controls...again, it's looking like another amp makes more sense.

But I agree with RG entirely, it's your amp, do what you want as long as you realise what you're getting into...none of the reasons I have posted above have ever stopped me gutting & rewiring an amp! ;-)

[guitarmike2107]

well since you have done so much you may as well try a new output transformer too. what it will do is maybe give more/tighter bass and extend the high end to give more chime, all this would make it sound louder too. depends on what is fitted to the silvertone though.

Buy a OT and hook it up without drilling the chassis if you can to see if it makes a big enough improvement. if not there will always be somebody who will buy it off you.
Dont spend stupid money on one though

R.G's advice if good if you can easily digest technical info. for the rest of us "suck it and see" seems to work .. but is more costly and takes us twice as long..

working an small SE amps is a great way to start to learn, or at least generate the interest..

good luck

[miltown]

Great that was great. That was a wealth of info in 3 posts. What I would take out of RG posts and I feel it is a very important one is know where you are going. That one made me think. I could be running around like a chicken with my head cut off very quickly. I'm not trying to create a Champ (I have one) I just want this amp to sound better and I know that is a general term. I don't mind the money at this point I just think of it as school, but I do have a budget. I also want to see what it is like to make an amp I'm just using the Sivertone chassis. It doesn't have to sound like holy #$%@^&&^%#@$^^^ man that's awesome. More kinda like that's cool. Thanks . I have to go back and read these posts again.


paul