Power Transformers?

[anomaly]

Do different power transformers actually change the tone of an amp? I know that output transformers do a bit, but am wondering how a power transformet would change the tone? It just determines the plate voltage, right? Reason I ask is I don't hear much of a difference in those old IIC+ amps. Whether it's a 105 or export...?? Seems to sound the same to me. But they're preamp distortion based amps so... IDK??

 

[FourT6and2]

"Do different power transformers actually change the tone of an amp?"

Yes, they can.

Keeping it simple, if PT-A puts out X voltage and Y current under load for heater, secondaries, and any other accessory taps, and PT-B puts out higher or lower voltages and currents, then there could be a difference in both sound and feel of the amp.

Not only that, but a transformer produces a giant magnetic field. And how a transformer is constructed and the quality of materials both affect this magnetic field. That in turn affects things like how hot or cool the transformer runs or how much hum the transformer injects into other parts of the circuit.

Even if PT-A and PT-B put out the exact same voltages and currents under the same operating conditions, PT-B might induce audible hum into the amp or even vibrate and hum mechanically, while PT-A might not, depending on how they're each constructed.

Some transformers use higher quality laminations like M6 or copper flux bands, which affect things a bit. Then you've got the quality of the potting/lacquering, quality of the wiring (leading to longevity and resistance to shorting under spicy operating conditions), and etc.

Two transformers can supply the same idle voltage and current for their various output taps. But under load, while you're playing, they can each respond and react differently due to any number of factors. e.g. you're chugging away at high volume with some super sick Swedish death metal. PT-A keeps up, supplying the appropriate power. But PT-B starts to struggle, failing to immediately provide the necessary current and/or voltages—leading to sag.

At the end of the day, choose quality transformers from reputable companies and you'll be ok. Avoid bargain-bin, no-name iron.

It just determines the plate voltage, right?

No. They do much more than that and they are not the only thing that contributes to an amp's plate voltage at idle or under load.

Reason I ask is I don't hear much of a difference in those old IIC+ amps. Whether it's a 105 or export...?? Seems to sound the same to me. But they're preamp distortion based amps so... IDK??

This is a slightly different scenario. You're asking about the same amp model that came from the manufacturer with two different transformers. In that case, I would trust the manufacturer to hopefully know what they're doing, so both amps sound the same.

That said, in vintage Marshalls like '70s – '80s JCM800s, they came with any number of different power transformers. And they didn't all supply the same voltages and current. Some yielded B+ as high as 530v and some yielded B+ as low as 380v. Mesa was hopefully more consistent.

 

[fusedbrain]

Great write up, and I agree with all of this.
Bottom line: if you need a replacement pt for your amp, you should be able to get a high quality drop-in from Heyboer, Mercury, or Hammond.
If you're a builder / hobbiest, lots of great options from those companies as well, for whatever your needs are. ( there are a few other good companies whose names escape me at the moment, but you get the idea )
Same logic applies to output tranformers:
there is no such thing as a good quality, budget priced transformer. You get what you pay for.
High quality steel and competent manufacturing costs $$.

 

[Iamnada]

I've always wondered if "upgrading" the transformer in a less expensive amp would improve it..or just make things run outside of their intended parameters.

AC and DC circuit classes in CC were a LONG time a go.

 

[Iamnada]

Do different power transformers actually change the tone of an amp? I know that output transformers do a bit, but am wondering how a power transformet would change the tone? It just determines the plate voltage, right? Reason I ask is I don't hear much of a difference in those old IIC+ amps. Whether it's a 105 or export...?? Seems to sound the same to me. But they're preamp distortion based amps so... IDK??

Awesome Avatar pic by the the way. I bought that movie in it's "steelbook" 4k blu-ray format I love it so much..No one in my family will watch it with me

 

[FourT6and2]

I've always wondered if "upgrading" the transformer in a less expensive amp would improve it..or just make things run outside of their intended parameters.

AC and DC circuit classes in CC were a LONG time a go.

No, I wouldn't bother doing that unless you really know what you're doing with voltage tuning. If you actually need or want higher or lower voltages in the amp, then changing the PT can get you there. Typically, someone hot-rodding an old Marshall, for example, might want to up the preamp voltages higher than what the original PT can provide for a starting B+. In that case, yes... a new PT might be warranted. But just randomly "upgrading" a PT in an amp in hopes of "better tone" isn't going to work.

 

[Racerxrated]

Great write up, and I agree with all of this.
Bottom line: if you need a replacement pt for your amp, you should be able to get a high quality drop-in from Heyboer, Mercury, or Hammond.
If you're a builder / hobbiest, lots of great options from those companies as well, for whatever your needs are. ( there are a few other good companies whose names escape me at the moment, but you get the idea )
Same logic applies to output tranformers:
there is no such thing as a good quality, budget priced transformer. You get what you pay for.
High quality steel and competent manufacturing costs $$.

I agree with most of this....with one exception. The Classictone transformers, when they were in business were budget trans. 70-80 bucks per transformer. At the same time, Mercury were over 200 per trans. In a couple of Ceriatone builds, same amp model, one used the Classictone set vs the other with Mercury. The Classictone amp sounded better to me. The Mercury sounded good too, just not AS good as the other.
Too bad they went out of business.

 

[Iamnada]

No, I wouldn't bother doing that unless you really know what you're doing with voltage tuning. If you actually need or want higher or lower voltages in the amp, then changing the PT can get you there. Typically, someone hot-rodding an old Marshall, for example, might want to up the preamp voltages higher than what the original PT can provide for a starting B+. In that case, yes... a new PT might be warranted. But just randomly "upgrading" a PT in an amp in hopes of "better tone" isn't going to work.

Thank you for confirming. Basically it'll only help the "tonez" if the OG transformer isn't performing to spec..AKA malfunctioning.

 

[fusedbrain]

I agree with most of this....with one exception. The Classictone transformers, when they were in business were budget trans. 70-80 bucks per transformer. At the same time, Mercury were over 200 per trans. In a couple of Ceriatone builds, same amp model, one used the Classictone set vs the other with Mercury. The Classictone amp sounded better to me. The Mercury sounded good too, just not AS good as the other.
Too bad they went out of business.

Ya know, I never considered Classictone to be budget transformers because they were always around the same price for me in Canada as Hammond and Heyboer.
I just thought it was Mercury being stupid with their pricing.
But man, that Classictone iron sounded damn good. I still have a few sets left for a couple of builds I'd like to do.

 

[FourT6and2]

I agree with most of this....with one exception. The Classictone transformers, when they were in business were budget trans. 70-80 bucks per transformer. At the same time, Mercury were over 200 per trans. In a couple of Ceriatone builds, same amp model, one used the Classictone set vs the other with Mercury. The Classictone amp sounded better to me. The Mercury sounded good too, just not AS good as the other.
Too bad they went out of business.

Output transformers are a different story.

 

[FourT6and2]

Here is a direct comparison of a stock 2203x and with 3 mercury magnetics. He measures the voltage and the MM have higher voltage. I can't hear a difference worth spending $5 or 5 minutes on.


Here is a mark IV with 3 different OTs. Again sound wise not worth the effort.


You could find just a PT change comparison, seems moot.

I'm not going to bother watching those because voltages 100% ABSOLUTELY MAKE A HUGE DIFFERENCE. I've built enough amps to know what works and what doesn't. A B+ of 450V vs 530V will sound and feel VASTLY different. As for Mesa's... they have a bold/spongy switch for a reason. That switch changes the voltages of the amp...

The point of swapping iron to raise the B+ voltage of an amp like that 2203 is completely lost unless other things in the circuit are addressed in parallel. But yes, I agree with you... a transformer swap, on its own, might not do much. And I wouldn't waste time or money on it.

I literally have a voltage tuning decade box to tune B+ voltages. I can turn a dial and get the amp feeling loose and spongy with a ton of fizzy gain, or tight and punchy with a modern high-gain attack. Changing out power transformers simply gives you the ability to raise the voltages higher than some other transformer might yield. Like I said before: it's easier to lower voltages rather than raise them.

This doesn't mean people should go out and swap iron for no reason. This is something best left to qualified techs who know what they're doing and who know what they're trying to accomplish... It's not a plug-and-play upgrade you can just randomly do to an amp to "get better tone".

Here's an example:

For a hot-rodded Marshall, I know what voltages I need at every B+ node in the amp. I know what plate voltage I want. I know what voltage I want to see at the phase inverter. I know what voltages I want to see down the line to each gain stage and any additional gain stages I add. A power transformer that puts out a rectified, loaded B+ of 475v won't work. It will sound too loose and muddy and undefined. The only way to get the amp sounding angry and tight and authoritative is to swap the PT out for something that yields over 500v. But understand this wouldn't be a stock Marshall circuit.

There are other considerations as well, but those get into actual circuit design. Like getting proper B+ and gain stage filtering decoupling. You have to use dropping/decoupling resistors large enough to properly separate the stages. But each one drops the voltage more and more to the next stage(s). So you need to start with a high enough voltage—especially if the amp has more gain stages than stock. And if the PT doesn't give you enough to work with, you're fucked.

 

[anomaly]

Yes, they can.

Keeping it simple, if PT-A puts out X voltage and Y current under load for heater, secondaries, and any other accessory taps, and PT-B puts out higher or lower voltages and currents, then there could be a difference in both sound and feel of the amp.

Not only that, but a transformer produces a giant magnetic field. And how a transformer is constructed and the quality of materials both affect this magnetic field. That in turn affects things like how hot or cool the transformer runs or how much hum the transformer injects into other parts of the circuit.

Even if PT-A and PT-B put out the exact same voltages and currents under the same operating conditions, PT-B might induce audible hum into the amp or even vibrate and hum mechanically, while PT-A might not, depending on how they're each constructed.

Some transformers use higher quality laminations like M6 or copper flux bands, which affect things a bit. Then you've got the quality of the potting/lacquering, quality of the wiring (leading to longevity and resistance to shorting under spicy operating conditions), and etc.

Two transformers can supply the same idle voltage and current for their various output taps. But under load, while you're playing, they can each respond and react differently due to any number of factors. e.g. you're chugging away at high volume with some super sick Swedish death metal. PT-A keeps up, supplying the appropriate power. But PT-B starts to struggle, failing to immediately provide the necessary current and/or voltages—leading to sag.

At the end of the day, choose quality transformers from reputable companies and you'll be ok. Avoid bargain-bin, no-name iron.




No. They do much more than that and they are not the only thing that contributes to an amp's plate voltage at idle or under load.




This is a slightly different scenario. You're asking about the same amp model that came from the manufacturer with two different transformers. In that case, I would trust the manufacturer to hopefully know what they're doing, so both amps sound the same.

That said, in vintage Marshalls like '70s – '80s JCM800s, they came with any number of different power transformers. And they didn't all supply the same voltages and current. Some yielded B+ as high as 530v and some yielded B+ as low as 380v. Mesa was hopefully more consistent.

That was a very in depth answer, thanks.

 

[Dale B]

Here's an example:

For a hot-rodded Marshall, I know what voltages I need at every B+ node in the amp. I know what plate voltage I want. I know what voltage I want to see at the phase inverter. I know what voltages I want to see down the line to each gain stage and any additional gain stages I add. A power transformer that puts out a rectified, loaded B+ of 475v won't work. It will sound too loose and muddy and undefined. The only way to get the amp sounding angry and tight and authoritative is to swap the PT out for something that yields over 500v. But understand this wouldn't be a stock Marshall circuit.

There are other considerations as well, but those get into actual circuit design. Like getting proper B+ and gain stage filtering decoupling. You have to use dropping/decoupling resistors large enough to properly separate the stages. But each one drops the voltage more and more to the next stage(s). So you need to start with a high enough voltage—especially if the amp has more gain stages than stock. And if the PT doesn't give you enough to work with, you're fucked.

YEP!

 

[Anje]

Agree with everything FourT6and2 said.
I'd ad the general statement that as for most things working out of electricity, the power supply is a critical part of the overall device that can have great impact on the way it functions/behaves; in our case here, translating to the "sound" & "feel" of an amp as we play (not even talking about having things "working safely/properly" to begin with).

 

[matttornado]

Yes, if it puts out different voltages. If the voltages are the same or very close, then no.

 

[FourT6and2]

Yes, if it puts out different voltages. If the voltages are the same or very close, then no.

I disagree.

As I explained above, even if two transformers put out the same exact voltages under the same operating conditions, they can perform differently in other ways. For example, if one has M6 laminations and a copper flux band and the other does not, you can get more noise from the latter transformer—either electrically or mechanically (vibrating/humming/buzzing). The transformer can induce noise into the circuit as well. Will this absolutely happen? No. But it can. And it does happen more often than not. Quality of materials and construction do matter.

Most people assume a transformer is just some wire wrapped around a bunch of metal laminations. And yeah, that's kinda true. But there are nuances that do affect performance.

 

[Hiwatts-n-Gibsons]

I just thought of another thing. Mesa's spongy/bold or variac switch is changing the power transformer's primary windings. You will noticed a difference when trying it. I did not find much use for it on the 2 I had. They are master volume amps and don't need it for reducing volume or trying to coax a bit more distortion.

Suhr SL67/68 amps have hi and lo power, same thing but they also adjust bias independently for each mode.

All the voltages in the amp will change BTW.

I never really thought of Spongy/Bold as being useful for reducing volume or adding gain. To me it seemed more intended for changing the tonal balance and feel of the amp. Spongy noticeably cut highs and lows, pushed the mids more forward, and created a softer, well spongier vintage small amp feel. Super elastic, less controlled, less thump and cut. I was not really a fan of the Spongy setting for high gain tones, but for cleans to mid gain roots rock Americana type stuff it was great.