Do output transformers "saturate"

[Mike K]

From the Baier article: "Now the 40 watts of low end that the tubes are delivering will never get to the speaker because it’s saturating in a smaller OT."
As well as: " This basic transformer architecture has remained unchanged to this day. The Blackface Vibrolux, Vibroverb, and Pro Reverb all share this smaller OT, and it is a key ingredient to the vibe of these amps. (The part that Fender produces today is literally identical to the 1950s specifications)."

^^The upper statement referring to BF amps is wrong.

The nominal output of a Vibrolux Rev. is 35W and that's exactly what my own amp measures before clipping.

My measurements show that this transformer could even handle 50W power input at 50Hz without significant drop in relative output.
It might overheat if that power is sustained, though.

The main difference to the SR OT is transformer efficiency/losses.
So the smaller OT might deliver 4W less to the load.

The OT did show signs of beginning saturation at my extreme test conditions, but that doesn't limit signal amplitude.

Yeah - something doesn't add up between the Tweed and BF statements. I think the perhaps the tweeds were different. Even the p/n from Triad for the tweeds is different.

And again, the PSU of the tweeds are a totally different animal with that mighty plate choke. I've never actually had my hands on one, but the schematic shows a much lower quiescent B+ of 415V (410 on the plates and screens).

There's also a very real possibility that the Tweed BM and Pro only would put out 28W, regardless of the OT.

To me, all these things would add up to 1) lower headroom and 2) more dynamic compression when pushed to overdrive. Couple that with the speaker choices and you probably have most of the recipe. I don't doubt the OT flavors things somewhat, but I'm skeptical that a smaller, poor design adds anything that sounds pleasing.


Once again I'll pull up the 5F1 and 5F2A. If you test either of those OTs on same circuit into a 12" speaker which has a wide low end response, anyone will be able to hear an audible difference in the low end response at any gain level. But SE OTs are far more sensitive than PP IME. On the same token, you can clearly hear a difference in the high end response to distortion with both. The 5F2A will handle more low and mid signal before becoming "blurry" or "fizzy". I have no measurements for this, but it's easy to hear.

[Mike K]

Can't see how an OT could cause compression.

I was thinking about this, but in terms of p/ups. I have some Fender 52 tele p/ups that sound "compressed" to me. That is to say they have a wide and bright clear dynamic range when picked moderately, but when you really slam them, they sound flatter*. They have A3 magnets, and I've talked to winders about this, but it doesn't seem well understood. It seems that it's just an effect that sounds like compression, but it's really just lack of harmonic content. As far as I can figure, OTs wouldn't have this sharp downslope that would cause this, as it has been shown that it's the second order slope at high frequencies that causes it, but perhaps some OTs with limited high frequency response may exhibit this to a slight degree, enough that guitarist may think is sounds "compression-like".


*It's not the amp, because at the same volume output, my strat with A4 or 5 p/ups does not sound this way. Or at least if it does, to a much lesser extent.

[Chuck H]

I was thinking about this, but in terms of p/ups. I have some Fender 52 tele p/ups that sound "compressed" to me. That is to say they have a wide and bright clear dynamic range when picked moderately, but when you really slam them, they sound flatter*. They have A3 magnets, and I've talked to winders about this, but it doesn't seem well understood. It seems that it's just an effect that sounds like compression, but it's really just lack of harmonic content. As far as I can figure, OTs wouldn't have this sharp downslope that would cause this, as it has been shown that it's the second order slope at high frequencies that causes it, but perhaps some OTs with limited high frequency response may exhibit this to a slight degree, enough that guitarist may think is sounds "compression-like".


*It's not the amp, because at the same volume output, my strat with A4 or 5 p/ups does not sound this way. Or at least if it does, to a much lesser extent.

Good looking out, really. There's a whole signal chain in play here and it starts with the player. Then there's the acoustic properties of the particular guitar, that feeds the pickups (with their own take on what's happening), then telling this to the amp (with it's own voicing) and then to the speakers in their respective cabinet AND the room it's played in. And how ALL THESE THINGS are set up to trigger each other. Trying to take too much inference on a specific component by ear is VERY problematic at this point. This is where measurements matter. Sometimes, though not too often, a small piece of magic can be identified. Usually it's too nebulous within the circumstances to make it an ALWAYS go to design or modification.

So to some degree we actually do use measurements to design the amp circuits to work with anything. This has the swiss army knife effect of making something that's equal to all tasks, but not exceptional at any one task. And IMHE amps that do this are very popular among pro musicians. These are players that find musical tones in a variety of ways but don't like road blocks. A generic amp that does everything with equal mediocrity allows for experimentation with pedals, speakers/cabinets, guitars and mic/room effects. What I'm saying is that an amp that blocks ANY path only to be exceptional in one (and there have been a few) only find themselves in a niche market. Whereas amps that are just generally "good" at everything have found their way onto stages all over the world. This is a hard concept to grasp for amp builder/tone seekers but a real musician with a live instrument in his/her hands is a different animal.

JM2C on that. And, that said... My own amp and my most poular design is purpose built and somewhat of a one trick pony. There are only a few out there and I don't "manufacture" these and there will probably never be a "market" for them. But I sure love mine and have been graced with meeting a few players that liked them for what they are.

In an interview with Eric Clapton regarding some drop in studio work, recalled by Enzo here some time ago, he said "Just give me an amp. I'll get a tone out of it." That is what players do. They find the musical properties of whatever materials they are presented with and proceed to make art. Samples of car horns, trash cans baging together and cats yowleing have been used in popular music by creative artists. It's really more about the creator than the gear. And it always has been.

But this is our genre. And amps that are "good" in one way or in a general way have appeal to professionals and ameteurs alike. For one it's just another tool. For the other it's a mystical gateway to the magic that the artists create. So we keep designing them and we keep trying to understand what is "right" about the favored designs. But the history on it is for the most part nebulous. The BF Fender and the Marshall 1959 float to the top (with a nod to Vox) mostly because they were ubiquitous in their era. This matters too because what follows and how our sensibilities are trained carries.

So what IS a good output transformer? What IS a good amp? What IS a good tone? I think the lack of any real definitions for these things is what keeps the genre alive. Because artists are simply going to keep making music on ANYTHING that works at the moment. If you're lucky enough it'll be your design and a million ameteurs will buy one.

[Mike K]

I was kind of shooting along the lines that disgruntled people like to talk about all the BS in the music equipment industry, and there certainly is plenty, but I think a good portion of the time it's people using terminology to try to explain something that isn't entirely technically correct. That was the whole premise of this thread, was it not? Sure, transformers can saturate. Do we want them to, I don't think so. Good winders do their best to avoid that. I probably said this before, but it seems to me that guitar equipment was always based on using cheap parts, just like any mass-produced industry, and it just so happened once in a while something came along that was a happy accident of this. People chase that to no end and come up with all sorts of buzz words to describe it, but it doesn't mean there isn't something real.

One clear example I can think of beyond transformers is for pickups. My stock Les Paul, which I no longer own, came with some PAF whatever... It was a fairly high-end LP. I ended up replacing those with some from Wolfe MacLeod, and they weren't even like the same things. The Gibson's had a bit more output, not much, but were so furry sounding. Wolfe's were amazingly clear. The neck pickup was astonishing - which I'd thought of as a throwaway, but the clean tone was amazingly bright and piano-like (I have clips to prove it). I've talked to him quite a few times over the years, and he wouldn't even give me an output spec on one of his pickups - I just wanted a rough idea, but he wasn't interested in that sort of thing. His answer was, "Depends on how hard you pick..." He's not wrong, but I was looking for some kind of comparison. Anyway, point is, he didn't need to be bogged down in these kinds of details to make something that was far superior to what came from Gibson's factory (not hard these days, apparently). I'm sure other people make comparable pickups, maybe for more, maybe for less... who knows... it's all a craps shoot. But some people have a craft and know how to work it, even if they don't have the technical jargon to impress engineers or care in measuring stuff that really doesn't matter.

In the automotive industry, this kind of stuff bothers me, because I know the technical details there, and in some respects, to a greater degree than any layman would. But music is art. I can't argue with results. We can argue till the cows come home about semantics of these things, but I got into this to replace 50W Mesas and Fenders with pedals out front that didn't do much for me. There's a fair bit of engineering involved, but a lot of it is pure luck when finding what works for you or being creative enough to make something great out of it. Not being that level of musician, I'm of the former camp.

[Mike K]

https://imgur.com/a/cZCZ5kK


Here's a fun one.*

$3875 for some messy wiring, cheap transformers (who are out of business now) and lots of ceramic** caps. Some amp snobs would have a field day with this one! But this is Page's amp, in a little less detail than the LE ones that sold out immediately. No one can really figure out wtf the circuit is - unless you pay the $4k and trace it. Supro probably didn't even know what they made and apparently it was a little modified (in addition to the speaker change). To me, that's crazy, but Page can sell it and it's worth it to people buying. I certainly don't know the details. Most of those amps probably ended up in the dump too - they were bottom of the barrel when new. Add in his Danelectro, various cheap preamps, using a wah for a treble booster and all the other stuff and you see how creativity can overcome technical perfection.


*I love Page, in no way am I dissing him.

**I've used ceramic caps and I don't get what's so bad about them tone-wise. But they get a bad rap on the net.

[Chuck H]

One clear example I can think of beyond transformers is for pickups. My stock Les Paul, which I no longer own, came with some PAF whatever... It was a fairly high-end LP. I ended up replacing those with some from Wolfe MacLeod, and they weren't even like the same things. The Gibson's had a bit more output, not much, but were so furry sounding. Wolfe's were amazingly clear. The neck pickup was astonishing - which I'd thought of as a throwaway,...

Well I might argue that there have been an insurmoutable amount of outstanding recordings made with stock Les Paul PAF neck pickups for decades and that just because it didn't work for you doesn't mean that what you like or idealize is better. And that's about all that needs to be sais about that.

But I get it. I've fussed with pickups (and certaily have my favorites) for decades and there are so many "signature" model pickups out there that it's clear your opinion is shared. And for me, personally, the stock PAF neck thing is nothing I've ever used much in my own playing.

But there are litterally hundreds of musicians and recordings that sound just fine or even great that use a Les Paul with a stock PAF in the neck pickup setting. So to even imply that it's flawed seems arrogant. Maybe it's not your thing. That's fine. It's not mine either as it happens. But that doesn't make it inherently wrong as implied.

I don't want to point fingers, but it's come up enough that I'm inclined to just now... You have a prose and cadance in your deliver that is suggestive of anything you disagree with being wrong even though you're delivering this opinion and any information in this highly subjective genre. How you think THAT is valid I can't understand. I would not want to have to lug such an ego around in my own life. Please just realize that it comes across as arrogant and offensive when you're less than careful about it.

And know that there are guys out there that would no sooner change out the stock PAF neck pickup in their Les paul than they would cut off their own toes. Not that you said they should, but there was definitely an inference that what they have is not good or useful without the concession that this is specific to your own tastes. Do you see how that makes your delivery offensive?

[Mike K]

Well I might argue that there have been an insurmoutable amount of outstanding recordings made with stock Les Paul PAF neck pickups for decades and that just because it didn't work for you doesn't mean that what you like or idealize is better. And that's about all that needs to be sais about that.

But I get it. I've fussed with pickups (and certaily have my favorites) for decades and there are so many "signature" model pickups out there that it's clear your opinion is shared. And for me, personally, the stock PAF neck thing is nothing I've ever used much in my own playing.

But there are litterally hundreds of musicians and recordings that sound just fine or even great that use a Les Paul with a stock PAF in the neck pickup setting. So to even imply that it's flawed seems arrogant. Maybe it's not your thing. That's fine. It's not mine either as it happens. But that doesn't make it inherently wrong as implied.

I don't want to point fingers, but it's come up enough that I'm inclined to just now... You have a prose and cadance in your deliver that is suggestive of anything you disagree with being wrong even though you're delivering this opinion and any information in this highly subjective genre. How you think THAT is valid I can't understand. I would not want to have to lug such an ego around in my own life. Please just realize that it comes across as arrogant and offensive when you're less than careful about it.

And know that there are guys out there that would no sooner change out the stock PAF neck pickup in their Les paul than they would cut off their own toes. Not that you said they should, but there was definitely an inference that what they have is not good or useful without the concession that this is specific to your own tastes. Do you see how that makes your delivery offensive?

They were both PAF designs...

I think you're misunderstanding.


Here we go again... OK man. I left last week because you were weird about something I said. Then you seemed OK, so I thought it was OK, even though you clearly had a thread directed at me, which I ignored. Now you're reading into something and directing it negatively.

Bye man. Good luck with this forum.

[Chuck H]

...far superior to what came from Gibson's factory (not hard these days, apparently).

I am sorry Mike. This was a knee jerk to the above quote because I am actually watching you for offensive behavior. (which you have exhibited and even admitted to doing intentionally, but I'm wrong here). You made some concession to individual tastes and were open about this being opinionated. This is my bad. I'm sure I ran with it out of context after re reading the whole post and I apologize.

[Helmholtz]

While I'm convinced that audible distortion by OT saturation in PP amps is unlikely, it might be different with SE amps.
I just recalled the severe single sided saturation/distortion at 400Hz I saw when scoping the reverb drive circuit of my Vibrolux Reverb.
This is just a small SE class A power amp.
The reason for saturation was the asymmetrical plate signal causing a net increase of OT primary DC current.
It seems likely that the same effect can occur with any non-center biased SE power amp using an OT that doesn't have sufficient DC headroom.