#1
i'm reading a lot about amplifier modifications. since i need to get my amp worked on i'm considering some mods to get done to it.
i constantly read about people switching out transformers
how does this change an amplifier? does it affect tone? what's the deal here?
thanks for the info
#4
^^no

Power transformers don't have a affect on tone really. A good quality transformer will run cooler, have tighter tolerance and last longer than a cheap stock transformer. It will put less stress on the rest of the amp and will last longer.

With OTs they definitely have an affect on tone. I cant explain why but I know its from the way they are made. I can definitely hear the difference between two transformers where the impedecnces of the primary and secondary are the exact same. Its in how they are wound and bad though that makes the difference in sound. But ya a well made OT will defiantly improve tone and I find it noticeable.
#6
In amps though you don't get this extra voltage from the transformer. If you do it that way then you need to increase the voltage rating and power rating on many resistors and caps.

If you want more voltage most people just scale down their plate resistors.

Increasing voltage from the PT (ala a variac) is an easy way to get things blowing up and smoking.
#7
Many amps they put just enough of a power trans to run the stock amp. Something like the Vjr to do some of the mods you might be able to get away with a stock PT but barely, so might need an upgrade. But it really doesnt affect the tone. The OT is a different story. Using the Vjr again the stock OT is just as cheap as they can get em. And a quality OT makes a big difference in the amps tone. And if you change output tubes sometimes you might need a different OT to match. The stock Vjr version1,2 amps the OT was better matched to the 6v6 than the el84, but the version 3 amp OT is better matched to the EL84.
#8
Many stock Output transformers are made with coils that can produce more losses between the primary and the secondary. They are also often made using cheaper E and I lamination that can have an effect on the sound. Some transformers aren't even potted well and can have problems like that.

A power transformer can have an effect upon the amp if the current supply is too low, or if there are problems that cause major voltage fluctuations.

Some modifications are things like putting in a OT that is rated for a higher wattage, this increases the reliability of the amp by making sure that there is sufficient headroom for the amp to distort and pass its clean rating. It may also involve putting a PT that has a higher current rating for the different secondaries, again to increase the reliability of the amp.

An OT can be changed for multiple reasons. Certain laminations can actually cause some distortion in the signal that is is transferring, while something like M6 is more often going to be found in an ultra linear output transformer. A transformer with a lower primary and secondary inductance will also have a inductive impedance, which can have some effects upon the transformer output signal.
#9
Quote by kurtlives91

With OTs they definitely have an affect on tone. I cant explain why but I know its from the way they are made. I can definitely hear the difference between two transformers where the impedecnces of the primary and secondary are the exact same.

In my experience the biggest effect on sound for two similar transformers (ie not comparing a bifilar wound transformer with a torodial or something) is the maximum power rating. Personally I feel this is what is responsible for a significant chunk of the early marshall tone; combine a severly underated transformer with celestions and you'll be most of the way to that grind character... A higher wattage tranny will give you a firmer low end and make everything tighter.

Judging the power rating is difficult however as nobody seems to rate in the same way; I've found weight is a decent indicator though. Lighter weight = lower maximum power in general... Of course you need to consider winding types as well of course...

Oh and remember you can usually SIGNIFICANTLY under-rate OTs in guitar amps without problems... Assuming of course you make sure you impedance match correctly; if you try pulling tubes and don't think about what you're doing you can kill off an under-rated transformer easily, whereas an over-rated one would be fine.
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